API Documentation¶

Overview¶

The AsyncSSH API is modeled after the new Python asyncio framework, with a create_connection() coroutine to create an SSH client and a create_server() coroutine to create an SSH server. Like the asyncio framework, these calls take a parameter of a factory which creates protocol objects to manage the connections once they are open. For AsyncSSH, create_connection() should be passed a client_factory which returns objects derived from SSHClient and create_server() should be passed a server_factory which returns objects derived from SSHServer. In addition, each connection will have an associated SSHClientConnection or SSHServerConnection object passed to the protocol objects which can be used to perform actions on the connection.

For client connections, authentication can be performed by passing in a username and password or SSH keys as arguments to create_connection() or by implementing handler methods on the SSHClient object which return credentials when the server requests them. If no credentials are provided, AsyncSSH automatically attempts to send the username of the local user and the keys found in their .ssh subdirectory. A list of expected server host keys can also be specified, with AsyncSSH defaulting to looking for matching lines in the user’s .ssh/known_hosts file.

For server connections, handlers can be implemented on the SSHServer object to return which authentication methods are supported and to validate credentials provided by clients.

Once an SSH client connection is established and authentication is successful, multiple simultaneous channels can be opened on it. This is accomplished calling methods such as create_session(), create_connection(), and create_unix_connection() on the SSHClientConnection object. The client can also set up listeners on remote TCP ports and UNIX domain sockets by calling create_server() and create_unix_server(). All of these methods take session_factory arguments that return SSHClientSession, SSHTCPSession, or SSHUNIXSession objects used to manage the channels once they are open. Alternately, channels can be opened using open_session(), open_connection(), or open_unix_connection(), which return SSHReader and SSHWriter objects that can be used to perform I/O on the channel. The methods start_server() and start_unix_server() can be used to set up listeners on remote TCP ports or UNIX domain sockets and get back these SSHReader and SSHWriter objects in a callback when new connections are opened.

The client can also set up TCP port forwarding by calling forward_local_port() or forward_remote_port() and UNIX domain socket forwarding by calling forward_local_path() or forward_remote_path(). In these cases, data transfer on the channels is managed automatically by AsyncSSH whenever new connections are opened, so custom session objects are not required.

When an SSH server receives a new connection and authentication is successful, handlers such as session_requested(), connection_requested(), unix_connection_requested(), server_requested(), and unix_server_requested() on the associated SSHServer object will be called when clients attempt to open channels or set up listeners. These methods return coroutines which can set up the requested sessions or connections, returning SSHServerSession or SSHTCPSession objects or handler functions that accept SSHReader and SSHWriter objects as arguments which manage the channels once they are open.

Each session object also has an associated SSHClientChannel, SSHServerChannel, or SSHTCPChannel object passed to it which can be used to perform actions on the channel. These channel objects provide a superset of the functionality found in asyncio transport objects.

In addition to the above functions and classes, helper functions for importing public and private keys can be found below under Public Key Support, exceptions can be found under Exceptions, supported algorithms can be found under Supported Algorithms, and some useful constants can be found under Constants.

Main Functions¶

create_connection¶

asyncssh.create_connection(client_factory, host, port=22, *, loop=None, tunnel=None, family=0, flags=0, local_addr=None, known_hosts=(), username=None, password=None, client_keys=(), passphrase=None, agent_path=(), agent_forwarding=False, client_version=(), kex_algs=(), encryption_algs=(), mac_algs=(), compression_algs=(), rekey_bytes=1073741824, rekey_seconds=3600)[source]¶

Create an SSH client connection

This function is a coroutine which can be run to create an outbound SSH client connection to the specified host and port.

When successful, the following steps occur:

The connection is established and an SSHClientConnection object is created to represent it.

The client_factory is called without arguments and should return an SSHClient object.

The client object is tied to the connection and its connection_made() method is called.

The SSH handshake and authentication process is initiated, calling methods on the client object if needed.

When authentication completes successfully, the client’s auth_completed() method is called.

The coroutine returns the (connection, client) pair. At this point, the connection is ready for sessions to be opened or port forwarding to be set up.

If an error occurs, it will be raised as an exception and the partially open connection and client objects will be cleaned up.

Note

Unlike socket.create_connection(), asyncio calls to create a connection do not support a timeout parameter. However, asyncio calls can be wrapped in a call to asyncio.wait_for() or asyncio.wait() which takes a timeout and provides equivalent functionality.

Parameters:

client_factory (callable) – A callable which returns an SSHClient object that will be tied to the connection
host (str) – The hostname or address to connect to
port (int) – (optional) The port number to connect to. If not specified, the default SSH port is used.
loop – (optional) The event loop to use when creating the connection. If not specified, the default event loop is used.
tunnel (SSHClientConnection) – (optional) An existing SSH client connection that this new connection should be tunneled over. If set, a direct TCP/IP tunnel will be opened over this connection to the requested host and port rather than connecting directly via TCP.
family (socket.AF_UNSPEC, socket.AF_INET, or socket.AF_INET6) – (optional) The address family to use when creating the socket. By default, the address family is automatically selected based on the host.
flags (flags to pass to getaddrinfo()) – (optional) The flags to pass to getaddrinfo() when looking up the host address
local_addr (tuple of str and int) – (optional) The host and port to bind the socket to before connecting
known_hosts (see Specifying known hosts) – (optional) The list of keys which will be used to validate the server host key presented during the SSH handshake. If this is not specified, the keys will be looked up in the file .ssh/known_hosts. If this is explicitly set to None, server host key validation will be disabled.
username (str) – (optional) Username to authenticate as on the server. If not specified, the currently logged in user on the local machine will be used.
password (str) – (optional) The password to use for client password authentication or keyboard-interactive authentication which prompts for a password. If this is not specified, client password authentication will not be performed.
client_keys (see Specifying private keys) – (optional) A list of keys which will be used to authenticate this client via public key authentication. If no client keys are specified, an attempt will be made to get them from an ssh-agent process. If that is not available, an attempt will be made to load them from the files .ssh/id_ed25519, .ssh/id_ecdsa, .ssh/id_rsa, and .ssh/id_dsa in the user’s home directory, with optional certificates loaded from the files .ssh/id_ed25519-cert.pub, .ssh/id_ecdsa-cert.pub, .ssh/id_rsa-cert.pub, and .ssh/id_dsa-cert.pub. If this argument is explicitly set to None, client public key authentication will not be performed.
passphrase (str) – (optional) The passphrase to use to decrypt client keys when loading them, if they are encrypted. If this is not specified, only unencrypted client keys can be loaded. If the keys passed into client_keys are already loaded, this argument is ignored.
agent_path (str or SSHServerConnection) – (optional) The path of a UNIX domain socket to use to contact an ssh-agent process which will perform the operations needed for client public key authentication, or the SSHServerConnection to use to forward ssh-agent requests over. If this is not specified and the environment variable SSH_AUTH_SOCK is set, its value will be used as the path. If client_keys is specified or this argument is explicitly set to None, an ssh-agent will not be used.
agent_forwarding (bool) – (optional) Whether or not to allow forwarding of ssh-agent requests from processes running on the server. By default, ssh-agent forwarding requests from the server are not allowed.
client_version (str) – (optional) An ASCII string to advertise to the SSH server as the version of this client, defaulting to AsyncSSH and its version number.
kex_algs (list of str) – (optional) A list of allowed key exchange algorithms in the SSH handshake, taken from key exchange algorithms
encryption_algs (list of str) – (optional) A list of encryption algorithms to use during the SSH handshake, taken from encryption algorithms
mac_algs (list of str) – (optional) A list of MAC algorithms to use during the SSH handshake, taken from MAC algorithms
compression_algs (list of str) – (optional) A list of compression algorithms to use during the SSH handshake, taken from compression algorithms, or None to disable compression
rekey_bytes (int) – (optional) The number of bytes which can be sent before the SSH session key is renegotiated. This defaults to 1 GB.
rekey_seconds (int) – (optional) The maximum time in seconds before the SSH session key is renegotiated. This defaults to 1 hour.

Returns:

An SSHClientConnection and SSHClient

create_server¶

asyncssh.create_server(server_factory, host=None, port=22, *, loop=None, family=0, flags=1, backlog=100, reuse_address=None, server_host_keys, passphrase=None, authorized_client_keys=None, server_version=(), kex_algs=(), encryption_algs=(), mac_algs=(), compression_algs=(), allow_pty=True, agent_forwarding=True, session_factory=None, session_encoding='utf-8', sftp_factory=None, window=2097152, max_pktsize=32768, rekey_bytes=1073741824, rekey_seconds=3600, login_timeout=120)[source]¶

Create an SSH server

This function is a coroutine which can be run to create an SSH server bound to the specified host and port. The return value is an object derived from asyncio.AbstractServer which can be used to later shut down the server.

Parameters:

server_factory (callable) – A callable which returns an SSHServer object that will be created for each new inbound connection
host (str) – (optional) The hostname or address to listen on. If not specified, listeners are created for all addresses.
port (int) – (optional) The port number to listen on. If not specified, the default SSH port is used.
loop – (optional) The event loop to use when creating the server. If not specified, the default event loop is used.
family (socket.AF_UNSPEC, socket.AF_INET, or socket.AF_INET6) – (optional) The address family to use when creating the server. By default, the address families are automatically selected based on the host.
flags (flags to pass to getaddrinfo()) – (optional) The flags to pass to getaddrinfo() when looking up the host
backlog (int) – (optional) The maximum number of queued connections allowed on listeners
reuse_address (bool) – (optional) Whether or not to reuse a local socket in the TIME_WAIT state without waiting for its natural timeout to expire. If not specified, this will be automatically set to True on UNIX.
server_host_keys (see Specifying private keys) – A list of private keys and optional certificates which can be used by the server as a host key. This argument must be specified.
passphrase (str) – (optional) The passphrase to use to decrypt server host keys when loading them, if they are encrypted. If this is not specified, only unencrypted server host keys can be loaded. If the keys passed into server_host_keys are already loaded, this argument is ignored.
authorized_client_keys (see Specifying authorized keys) – (optional) A list of authorized user and CA public keys which should be trusted for certifcate-based client public key authentication.
server_version (str) – (optional) An ASCII string to advertise to SSH clients as the version of this server, defaulting to AsyncSSH and its version number.
kex_algs (list of str) – (optional) A list of allowed key exchange algorithms in the SSH handshake, taken from key exchange algorithms
encryption_algs (list of str) – (optional) A list of encryption algorithms to use during the SSH handshake, taken from encryption algorithms
mac_algs (list of str) – (optional) A list of MAC algorithms to use during the SSH handshake, taken from MAC algorithms
compression_algs (list of str) – (optional) A list of compression algorithms to use during the SSH handshake, taken from compression algorithms, or None to disable compression
allow_pty (bool) – (optional) Whether or not to allow allocation of a pseudo-tty in sessions, defaulting to True
agent_forwarding (bool) – (optional) Whether or not to allow forwarding of ssh-agent requests back to the client when the client supports it, defaulting to True
session_factory (callable) – (optional) A callable or coroutine handler function which takes AsyncSSH stream objects for stdin, stdout, and stderr that will be called each time a new shell, exec, or subsystem other than SFTP is requested by the client. If not specified, sessions are rejected by default unless the session_requested() method is overridden on the SSHServer object returned by server_factory to make this decision.
session_encoding (str) – (optional) The Unicode encoding to use for data exchanged on sessions on this server, defaulting to UTF-8 (ISO 10646) format. If None is passed in, the application can send and receive raw bytes.
sftp_factory (callable) – (optional) A callable which returns an SFTPServer object that will be created each time an SFTP session is requested by the client, or True to use the base SFTPServer class to handle SFTP requests. If not specified, SFTP sessions are rejected by default.
window (int) – (optional) The receive window size for sessions on this server
max_pktsize (int) – (optional) The maximum packet size for sessions on this server
rekey_bytes (int) – (optional) The number of bytes which can be sent before the SSH session key is renegotiated, defaulting to 1 GB
rekey_seconds (int) – (optional) The maximum time in seconds before the SSH session key is renegotiated, defaulting to 1 hour
login_timeout (int) – (optional) The maximum time in seconds allowed for authentication to complete, defaulting to 2 minutes

Returns:

asyncio.AbstractServer

connect¶

asyncssh.connect(host, port=22, **kwargs)[source]¶

Make an SSH client connection

This function is a coroutine wrapper around create_connection() which can be used when a custom SSHClient instance is not needed. It takes all the same arguments as create_connection() except for client_factory and returns only the SSHClientConnection object rather than a tuple of an SSHClientConnection and SSHClient.

When using this call, the following restrictions apply:

No callbacks are called when the connection is successfully opened, when it is closed, or when authentication completes.

Any authentication information must be provided as arguments to this call, as any authentication callbacks will deny other authentication attempts. Also, authentication banner information will be ignored.

Any debug messages sent by the server will be ignored.

listen¶

asyncssh.listen(host=None, port=22, *, server_host_keys, **kwargs)[source]¶

Start an SSH server

This function is a coroutine wrapper around create_server() which can be used when a custom SSHServer instance is not needed. It takes all the same arguments as create_server() except for server_factory.

When using this call, the following restrictions apply:

No callbacks are called when a new connection arrives, when a connection is closed, or when authentication completes.

Any authentication information must be provided as arguments to this call, as any authentication callbacks will deny other authentication attempts. Currently, this allows only public key authentication to be used, by passing in the authorized_client_keys argument.

Only handlers using the streams API are supported and the same handlers must be used for all clients. These handlers must be provided in the session_factory and/or sftp_factory arguments to this call.

Any debug messages sent by the client will be ignored.

Main Classes¶

SSHClient¶

class asyncssh.SSHClient[source]¶

SSH client protocol handler

Applications should subclass this when implementing an SSH client. The functions listed below should be overridden to define application-specific behavior. In particular, the method auth_completed() should be defined to open the desired SSH channels on this connection once authentication has been completed.

For simple password or public key based authentication, nothing needs to be defined here if the password or client keys are passed in when the connection is created. However, to prompt interactively or otherwise dynamically select these values, the methods password_auth_requested() and/or public_key_auth_requested() can be defined. Keyboard-interactive authentication is also supported via kbdint_auth_requested() and kbdint_challenge_received().

If the server sends an authentication banner, the method auth_banner_received() will be called.

If the server requires a password change, the method password_change_requested() will be called, followed by either password_changed() or password_change_failed() depending on whether the password change is successful.

General connection handlers

connection_made(connection)[source]¶

Called when a connection is made

This method is called as soon as the TCP connection completes. The connection parameter should be stored if needed for later use.

Parameters:	connection (`SSHClientConnection`) – The connection which was successfully opened

connection_lost(exc)[source]¶

Called when a connection is lost or closed

This method is called when a connection is closed. If the connection is shut down cleanly, exc will be None. Otherwise, it will be an exception explaining the reason for the disconnect.

Parameters:	exc (`Exception`) – The exception which caused the connection to close, or `None` if the connection closed cleanly

debug_msg_received(msg, lang, always_display)[source]¶

A debug message was received on this connection

This method is called when the other end of the connection sends a debug message. Applications should implement this method if they wish to process these debug messages.

Parameters:	msg (str) – The debug message sent lang (str) – The language the message is in always_display (bool) – Whether or not to display the message

General authentication handlers

auth_banner_received(msg, lang)[source]¶

An incoming authentication banner was received

This method is called when the server sends a banner to display during authentication. Applications should implement this method if they wish to do something with the banner.

Parameters:	msg (str) – The message the server wanted to display lang (str) – The language the message is in

auth_completed()[source]¶

Authentication was completed successfully

This method is called when authentication has completed succesfully. Applications may use this method to create whatever client sessions and direct TCP/IP or UNIX domain connections are needed and/or set up listeners for incoming TCP/IP or UNIX domain connections coming from the server.

Public key authentication handlers

public_key_auth_requested()[source]¶

Public key authentication has been requested

This method should return a private key corresponding to the user that authentication is being attempted for.

This method may be called multiple times and can return a different key to try each time it is called. When there are no keys left to try, it should return None to indicate that some other authentication method should be tried.

If client keys were provided when the connection was opened, they will be tried before this method is called.

If blocking operations need to be performed to determine the key to authenticate with, this method may be defined as a coroutine.

Returns:	A key as described in Specifying private keys or `None` to move on to another authentication method

Password authentication handlers

password_auth_requested()[source]¶

Password authentication has been requested

This method should return a string containing the password corresponding to the user that authentication is being attempted for. It may be called multiple times and can return a different password to try each time, but most servers have a limit on the number of attempts allowed. When there’s no password left to try, this method should return None to indicate that some other authentication method should be tried.

If a password was provided when the connection was opened, it will be tried before this method is called.

If blocking operations need to be performed to determine the password to authenticate with, this method may be defined as a coroutine.

Returns:	A string containing the password to authenticate with or `None` to move on to another authentication method

password_change_requested(prompt, lang)[source]¶

A password change has been requested

This method is called when password authentication was attempted and the user’s password was expired on the server. To request a password change, this method should return a tuple or two strings containing the old and new passwords. Otherwise, it should return NotImplemented.

If blocking operations need to be performed to determine the passwords to authenticate with, this method may be defined as a coroutine.

By default, this method returns NotImplemented.

Parameters:	prompt (str) – The prompt requesting that the user enter a new password lang (str) – The language that the prompt is in
Returns:	A tuple of two strings containing the old and new passwords or `NotImplemented` if password changes aren’t supported

password_changed()[source]¶

The requested password change was successful

This method is called to indicate that a requested password change was successful. It is generally followed by a call to auth_completed() since this means authentication was also successful.

password_change_failed()[source]¶

The requested password change has failed

This method is called to indicate that a requested password change failed, generally because the requested new password doesn’t meet the password criteria on the remote system. After this method is called, other forms of authentication will automatically be attempted.

Keyboard-interactive authentication handlers

kbdint_auth_requested()[source]¶

Keyboard-interactive authentication has been requested

This method should return a string containing a comma-separated list of submethods that the server should use for keyboard-interactive authentication. An empty string can be returned to let the server pick the type of keyboard-interactive authentication to perform. If keyboard-interactive authentication is not supported, None should be returned.

By default, keyboard-interactive authentication is supported if a password was provided when the SSHClient was created and it hasn’t been sent yet. If the challenge is not a password challenge, this authentication will fail. This method and the kbdint_challenge_received() method can be overridden if other forms of challenge should be supported.

If blocking operations need to be performed to determine the submethods to request, this method may be defined as a coroutine.

Returns:	A string containing the submethods the server should use for authentication or `None` to move on to another authentication method

kbdint_challenge_received(name, instruction, lang, prompts)[source]¶

A keyboard-interactive auth challenge has been received

This method is called when the server sends a keyboard-interactive authentication challenge.

The return value should be a list of strings of the same length as the number of prompts provided if the challenge can be answered, or None to indicate that some other form of authentication should be attempted.

If blocking operations need to be performed to determine the responses to authenticate with, this method may be defined as a coroutine.

By default, this method will look for a challenge consisting of a single ‘Password:’ prompt, and call the method password_auth_requested() to provide the response. It will also ignore challenges with no prompts (generally used to provide instructions). Any other form of challenge will cause this method to return None to move on to another authentication method.

Parameters:	name (str) – The name of the challenge instruction (str) – Instructions to the user about how to respond to the challenge lang (str) – The language the challenge is in prompts (list of tuples of str and bool) – The challenges the user should respond to and whether or not the responses should be echoed when they are entered
Returns:	List of string responses to the challenge or `None` to move on to another authentication method

SSHServer¶

class asyncssh.SSHServer[source]¶

SSH server protocol handler

Applications should subclass this when implementing an SSH server. At a minimum, one or more of the authentication handlers will need to be overridden to perform authentication, or begin_auth() should be overridden to return False to indicate that no authentication is required.

In addition, one or more of the session_requested(), connection_requested(), server_requested(), unix_connection_requested(), or unix_server_requested() methods will need to be overridden to handle requests to open sessions or direct connections or set up listeners for forwarded connections.

General connection handlers

connection_made(connection)[source]¶

Called when a connection is made

This method is called when a new TCP connection is accepted. The connection parameter should be stored if needed for later use.

connection_lost(exc)[source]¶

Called when a connection is lost or closed

This method is called when a connection is closed. If the connection is shut down cleanly, exc will be None. Otherwise, it will be an exception explaining the reason for the disconnect.

debug_msg_received(msg, lang, always_display)[source]¶

A debug message was received on this connection

This method is called when the other end of the connection sends a debug message. Applications should implement this method if they wish to process these debug messages.

Parameters:	msg (str) – The debug message sent lang (str) – The language the message is in always_display (bool) – Whether or not to display the message

General authentication handlers

begin_auth(username)[source]¶

Authentication has been requested by the client

This method will be called when authentication is attempted for the specified user. Applications should use this method to prepare whatever state they need to complete the authentication, such as loading in the set of authorized keys for that user. If no authentication is required for this user, this method should return False to cause the authentication to immediately succeed. Otherwise, it should return True to indicate that authentication should proceed.

Parameters:	username (str) – The name of the user being authenticated
Returns:	A bool indicating whether authentication is required

Public key authentication handlers

public_key_auth_supported()[source]¶

Return whether or not public key authentication is supported

This method should return True if client public key authentication is supported. Applications wishing to support it must have this method return True and implement validate_public_key() to return whether or not the key provided by the client is valid for the user being authenticated.

By default, it returns False indicating the client public key authentication is not supported.

Returns:	A bool indicating if public key authentication is supported or not

validate_public_key(username, key)[source]¶

Return whether key is an authorized client key for this user

Basic key-based client authentication can be supported by passing authorized keys in the authorized_client_keys argument of create_server(), or by calling set_authorized_keys on the server connection from the begin_auth() method. However, for more flexibility in matching on the allowed set of keys, this method can be implemented by the application to do the matching itself. It should return True if the specified key is a valid client key for the user being authenticated.

This method may be called multiple times with different keys provided by the client. Applications should precompute as much as possible in the begin_auth() method so that this function can quickly return whether the key provided is in the list.

If blocking operations need to be performed to determine the validity of the key, this method may be defined as a coroutine.

By default, this method returns False for all client keys.

Note

This function only needs to report whether the public key provided is a valid client key for this user. If it is, AsyncSSH will verify that the client possesses the corresponding private key before allowing the authentication to succeed.

Parameters:	username (str) – The user being authenticated key (`SSHKey` public key) – The public key sent by the client
Returns:	A bool indicating if the specified key is a valid client key for the user being authenticated

validate_ca_key(username, key)[source]¶

Return whether key is an authorized CA key for this user

Basic key-based client authentication can be supported by passing authorized keys in the authorized_client_keys argument of create_server(), or by calling set_authorized_keys on the server connection from the begin_auth() method. However, for more flexibility in matching on the allowed set of keys, this method can be implemented by the application to do the matching itself. It should return True if the specified key is a valid certificate authority key for the user being authenticated.

This method may be called multiple times with different keys provided by the client. Applications should precompute as much as possible in the begin_auth() method so that this function can quickly return whether the key provided is in the list.

If blocking operations need to be performed to determine the validity of the key, this method may be defined as a coroutine.

By default, this method returns False for all CA keys.

Note

This function only needs to report whether the public key provided is a valid CA key for this user. If it is, AsyncSSH will verify that the certificate is valid, that the user is one of the valid principals for the certificate, and that the client possesses the private key corresponding to the public key in the certificate before allowing the authentication to succeed.

Parameters:	username (str) – The user being authenticated key (`SSHKey` public key) – The public key which signed the certificate sent by the client
Returns:	A bool indicating if the specified key is a valid CA key for the user being authenticated

Password authentication handlers

password_auth_supported()[source]¶

Return whether or not password authentication is supported

This method should return True if password authentication is supported. Applications wishing to support it must have this method return True and implement validate_password() to return whether or not the password provided by the client is valid for the user being authenticated.

By default, this method returns False indicating that password authentication is not supported.

Returns:	A bool indicating if password authentication is supported or not

validate_password(username, password)[source]¶

Return whether password is valid for this user

This method should return True if the specified password is a valid password for the user being authenticated. It must be overridden by applications wishing to support password authentication.

If the password provided is valid but expired, this method may raise PasswordChangeRequired to request that the client provide a new password before authentication is allowed to complete. In this case, the application must override change_password() to handle the password change request.

This method may be called multiple times with different passwords provided by the client. Applications may wish to limit the number of attempts which are allowed. This can be done by having password_auth_supported() begin returning False after the maximum number of attempts is exceeded.

If blocking operations need to be performed to determine the validity of the password, this method may be defined as a coroutine.

By default, this method returns False for all passwords.

Parameters:	username (str) – The user being authenticated password (str) – The password sent by the client
Returns:	A bool indicating if the specified password is valid for the user being authenticated
Raises:	`PasswordChangeRequired` if the password provided is expired and needs to be changed

change_password(username, old_password, new_password)[source]¶

Handle a request to change a user’s password

This method is called when a user makes a request to change their password. It should first validate that the old password provided is correct and then attempt to change the user’s password to the new value.

If the old password provided is valid and the change to the new password is successful, this method should return True. If the old password is not valid or password changes are not supported, it should return False. It may also raise PasswordChangeRequired to request that the client try again if the new password is not acceptable for some reason.

If blocking operations need to be performed to determine the validity of the old password or to change to the new password, this method may be defined as a coroutine.

By default, this method returns False, rejecting all password changes.

Parameters:	username (str) – The user whose password should be changed old_password (str) – The user’s current password new_password (str) – The new password being requested
Returns:	A bool indicating if the password change is successful or not
Raises:	`PasswordChangeRequired` if the new password is not acceptable and the client should be asked to provide another

Keyboard-interactive authentication handlers

kbdint_auth_supported()[source]¶

Return whether or not keyboard-interactive authentication is supported

This method should return True if keyboard-interactive authentication is supported. Applications wishing to support it must have this method return True and implement get_kbdint_challenge() and validate_kbdint_response() to generate the apporiate challenges and validate the responses for the user being authenticated.

By default, this method returns NotImplemented tying this authentication to password authentication. If the application implements password authentication and this method is not overridden, keyboard-interactive authentication will be supported by prompting for a password and passing that to the password authentication callbacks.

Returns:	A bool indicating if keyboard-interactive authentication is supported or not

get_kbdint_challenge(username, lang, submethods)[source]¶

Return a keyboard-interactive auth challenge

This method should return True if authentication should succeed without any challenge, False if authentication should fail without any challenge, or an auth challenge consisting of a challenge name, instructions, a language tag, and a list of tuples containing prompt strings and booleans indicating whether input should be echoed when a value is entered for that prompt.

If blocking operations need to be performed to determine the challenge to issue, this method may be defined as a coroutine.

Parameters:	username (str) – The user being authenticated lang (str) – The language requested by the client for the challenge submethods (str) – A comma-separated list of the types of challenges the client can support, or the empty string if the server should choose
Returns:	An authentication challenge as described above

validate_kbdint_response(username, responses)[source]¶

Return whether the keyboard-interactive response is valid for this user

This method should validate the keyboard-interactive responses provided and return True if authentication should succeed with no further challenge, False if authentication should fail, or an additional auth challenge in the same format returned by get_kbdint_challenge(). Any series of challenges can be returned this way. To print a message in the middle of a sequence of challenges without prompting for additional data, a challenge can be returned with an empty list of prompts. After the client acknowledges this message, this function will be called again with an empty list of responses to continue the authentication.

If blocking operations need to be performed to determine the validity of the response or the next challenge to issue, this method may be defined as a coroutine.

Parameters:	username (str) – The user being authenticated responses (list of str) – A list of responses to the last challenge
Returns:	`True`, `False`, or the next challenge

Channel session open handlers

session_requested()[source]¶

Handle an incoming session request

This method is called when a session open request is received from the client, indicating it wishes to open a channel to be used for running a shell, executing a command, or connecting to a subsystem. If the application wishes to accept the session, it must override this method to return either an SSHServerSession object to use to process the data received on the channel or a tuple consisting of an SSHServerChannel object created with create_server_channel and an SSHServerSession, if the application wishes to pass non-default arguments when creating the channel.

If blocking operations need to be performed before the session can be created, a coroutine which returns an SSHServerSession object can be returned instead of the session iself. This can be either returned directly or as a part of a tuple with an SSHServerChannel object.

To reject this request, this method should return False to send back a “Session refused” response or raise a ChannelOpenError exception with the reason for the failure.

The details of what type of session the client wants to start will be delivered to methods on the SSHServerSession object which is returned, along with other information such as environment variables, terminal type, size, and modes.

By default, all session requests are rejected.

Returns:	One of the following: An `SSHServerSession` object or a coroutine which returns an `SSHServerSession` A tuple consisting of an `SSHServerChannel` and the above A callable or coroutine handler function which takes AsyncSSH stream objects for stdin, stdout, and stderr as arguments A tuple consisting of an `SSHServerChannel` and the above `False` to refuse the request
Raises:	`ChannelOpenError` if the session shouldn’t be accepted

connection_requested(dest_host, dest_port, orig_host, orig_port)[source]¶

Handle a direct TCP/IP connection request

This method is called when a direct TCP/IP connection request is received by the server. Applications wishing to accept such connections must override this method.

To allow standard port forwarding of data on the connection to the requested destination host and port, this method should return True.

To reject this request, this method should return False to send back a “Connection refused” response or raise an ChannelOpenError exception with the reason for the failure.

If the application wishes to process the data on the connection itself, this method should return either an SSHTCPSession object which can be used to process the data received on the channel or a tuple consisting of of an SSHTCPChannel object created with create_tcp_channel() and an SSHTCPSession, if the application wishes to pass non-default arguments when creating the channel.

If blocking operations need to be performed before the session can be created, a coroutine which returns an SSHTCPSession object can be returned instead of the session iself. This can be either returned directly or as a part of a tuple with an SSHTCPChannel object.

By default, all connection requests are rejected.

Parameters:

dest_host (str) – The address the client wishes to connect to
dest_port (int) – The port the client wishes to connect to
orig_host (str) – The address the connection was originated from
orig_port (int) – The port the connection was originated from

Returns:

One of the following:

An SSHTCPSession object or a coroutine which returns an SSHTCPSession
A tuple consisting of an SSHTCPChannel and the above
A callable or coroutine handler function which takes AsyncSSH stream objects for reading from and writing to the connection
A tuple consisting of an SSHTCPChannel and the above
True to request standard port forwarding
False to refuse the connection

Raises:

ChannelOpenError if the connection shouldn’t be accepted

unix_connection_requested(dest_path)[source]¶

Handle a direct UNIX domain socket connection request

This method is called when a direct UNIX domain socket connection request is received by the server. Applications wishing to accept such connections must override this method.

To allow standard path forwarding of data on the connection to the requested destination path, this method should return True.

To reject this request, this method should return False to send back a “Connection refused” response or raise an ChannelOpenError exception with the reason for the failure.

If the application wishes to process the data on the connection itself, this method should return either an SSHUNIXSession object which can be used to process the data received on the channel or a tuple consisting of of an SSHUNIXChannel object created with create_unix_channel() and an SSHUNIXSession, if the application wishes to pass non-default arguments when creating the channel.

If blocking operations need to be performed before the session can be created, a coroutine which returns an SSHUNIXSession object can be returned instead of the session iself. This can be either returned directly or as a part of a tuple with an SSHUNIXChannel object.

By default, all connection requests are rejected.

Parameters:	dest_path (str) – The path the client wishes to connect to
Returns:	One of the following: An `SSHUNIXSession` object or a coroutine which returns an `SSHUNIXSession` A tuple consisting of an `SSHUNIXChannel` and the above A callable or coroutine handler function which takes AsyncSSH stream objects for reading from and writing to the connection A tuple consisting of an `SSHUNIXChannel` and the above `True` to request standard path forwarding `False` to refuse the connection
Raises:	`ChannelOpenError` if the connection shouldn’t be accepted

server_requested(listen_host, listen_port)[source]¶

Handle a request to listen on a TCP/IP address and port

This method is called when a client makes a request to listen on an address and port for incoming TCP connections. The port to listen on may be 0 to request a dynamically allocated port. Applications wishing to allow TCP/IP connection forwarding must override this method.

To set up standard port forwarding of connections received on this address and port, this method should return True.

If the application wishes to manage listening for incoming connections itself, this method should return an SSHListener object that listens for new connections and calls create_connection on each of them to forward them back to the client or return None if the listener can’t be set up.

If blocking operations need to be performed to set up the listener, a coroutine which returns an SSHListener can be returned instead of the listener itself.

To reject this request, this method should return False.

By default, this method rejects all server requests.

Parameters:

listen_host (str) – The address the server should listen on
listen_port (int) – The port the server should listen on, or the value 0 to request that the server dynamically allocate a port

Returns:

One of the following:

An SSHListener object or a coroutine which returns an SSHListener or False if the listener can’t be opened
True to set up standard port forwarding
False to reject the request

unix_server_requested(listen_path)[source]¶

Handle a request to listen on a UNIX domain socket

This method is called when a client makes a request to listen on a path for incoming UNIX domain socket connections. Applications wishing to allow UNIX domain socket forwarding must override this method.

To set up standard path forwarding of connections received on this path, this method should return True.

If the application wishes to manage listening for incoming connections itself, this method should return an SSHListener object that listens for new connections and calls create_unix_connection on each of them to forward them back to the client or return None if the listener can’t be set up.

If blocking operations need to be performed to set up the listener, a coroutine which returns an SSHListener can be returned instead of the listener itself.

To reject this request, this method should return False.

By default, this method rejects all server requests.

Parameters:	listen_path (str) – The path the server should listen on
Returns:	One of the following: An `SSHListener` object or a coroutine which returns an `SSHListener` or `False` if the listener can’t be opened `True` to set up standard path forwarding `False` to reject the request

Connection Classes¶

SSHClientConnection¶

class asyncssh.SSHClientConnection[source]¶

SSH client connection

This class represents an SSH client connection.

Once authentication is successful on a connection, new client sessions can be opened by calling create_session().

Direct TCP connections can be opened by calling create_connection().

Remote listeners for forwarded TCP connections can be opened by calling create_server().

Direct UNIX domain socket connections can be opened by calling create_unix_connection().

Remote listeners for forwarded UNIX domain socket connections can be opened by calling create_unix_server().

TCP port forwarding can be set up by calling forward_local_port() or forward_remote_port().

UNIX domain socket forwarding can be set up by calling forward_local_path() or forward_remote_path().

General connection methods

get_extra_info(name, default=None)¶

Get additional information about the connection

This method returns extra information about the connection once it is established. Supported values include everything supported by a socket transport plus:

username

client_version

server_version

send_cipher

send_mac

send_compression

recv_cipher

recv_mac

recv_compression

See get_extra_info() in asyncio.BaseTransport for more information.

send_debug(msg, lang='en-US', always_display=False)¶

Send a debug message on this connection

This method can be called to send a debug message to the other end of the connection.

Parameters:	msg (str) – The debug message to send lang (str) – The language the message is in always_display (bool) – Whether or not to display the message

Client session open methods

create_session(session_factory, command=None, *, subsystem=None, env={}, term_type=None, term_size=None, term_modes={}, encoding='utf-8', window=2097152, max_pktsize=32768)[source]¶

Create an SSH client session

This method is a coroutine which can be called to create an SSH client session used to execute a command, start a subsystem such as sftp, or if no command or subsystem is specific run an interactive shell. Optional arguments allow terminal and environment information to be provided.

By default, this class expects string data in its send and receive functions, which it encodes on the SSH connection in UTF-8 (ISO 10646) format. An optional encoding argument can be passed in to select a different encoding, or None can be passed in if the application wishes to send and receive raw bytes.

Other optional arguments include the SSH receive window size and max packet size which default to 2 MB and 32 KB, respectively.

Parameters:

session_factory (callable) – A callable which returns an SSHClientSession object that will be created to handle activity on this session
command (str) – (optional) The remote command to execute. By default, an interactive shell is started if no command or subsystem is provided.
subsystem (str) – (optional) The name of a remote subsystem to start up
env (dictionary) –
(optional) The set of environment variables to set for this session. Keys and values passed in here will be converted to Unicode strings encoded as UTF-8 (ISO 10646) for transmission.

Note

Many SSH servers restrict which environment variables a client is allowed to set. The server’s configuration may need to be edited before environment variables can be successfully set in the remote environment.
term_type (str) – (optional) The terminal type to set for this session. If this is not set, a pseudo-terminal will not be requested for this session.
term_size (tuple of 2 or 4 integers) – (optional) The terminal width and height in characters and optionally the width and height in pixels
term_modes – (optional) POSIX terminal modes to set for this session, where keys are taken from POSIX terminal modes with values defined in section 8 of RFC 4254#section-8.
encoding (str) – (optional) The Unicode encoding to use for data exchanged on the connection
window (int) – (optional) The receive window size for this session
max_pktsize (int) – (optional) The maximum packet size for this session

Returns:

an SSHClientChannel and SSHClientSession

open_session(*args, **kwargs)[source]¶

Open an SSH client session

This method is a coroutine wrapper around create_session() designed to provide a “high-level” stream interface for creating an SSH client session. Instead of taking a session_factory argument for constructing an object which will handle activity on the session via callbacks, it returns an SSHWriter and two SSHReader objects representing stdin, stdout, and stderr which can be used to perform I/O on the session. With the exception of session_factory, all of the arguments to create_session() are supported and have the same meaning.

create_connection(session_factory, remote_host, remote_port, orig_host='', orig_port=0, *, encoding=None, window=2097152, max_pktsize=32768)[source]¶

Create an SSH TCP direct connection

This method is a coroutine which can be called to request that the server open a new outbound TCP connection to the specified destination host and port. If the connection is successfully opened, a new SSH channel will be opened with data being handled by a SSHTCPSession object created by session_factory.

Optional arguments include the host and port of the original client opening the connection when performing TCP port forwarding.

By default, this class expects data to be sent and received as raw bytes. However, an optional encoding argument can be passed in to select the encoding to use, allowing the application send and receive string data.

Other optional arguments include the SSH receive window size and max packet size which default to 2 MB and 32 KB, respectively.

Parameters:	session_factory (callable) – A callable which returns an `SSHClientSession` object that will be created to handle activity on this session remote_host (str) – The remote hostname or address to connect to remote_port (int) – The remote port number to connect to orig_host (str) – (optional) The hostname or address of the client requesting the connection orig_port (int) – (optional) The port number of the client requesting the connection encoding (str) – (optional) The Unicode encoding to use for data exchanged on the connection window (int) – (optional) The receive window size for this session max_pktsize (int) – (optional) The maximum packet size for this session
Returns:	an `SSHTCPChannel` and `SSHTCPSession`
Raises:	`ChannelOpenError` if the connection can’t be opened

open_connection(*args, **kwargs)[source]¶

Open an SSH TCP direct connection

This method is a coroutine wrapper around create_connection() designed to provide a “high-level” stream interface for creating an SSH TCP direct connection. Instead of taking a session_factory argument for constructing an object which will handle activity on the session via callbacks, it returns SSHReader and SSHWriter objects which can be used to perform I/O on the connection.

With the exception of session_factory, all of the arguments to create_connection() are supported and have the same meaning here.

Returns:	an `SSHReader` and `SSHWriter`
Raises:	`ChannelOpenError` if the connection can’t be opened

create_server(session_factory, listen_host, listen_port, *, encoding=None, window=2097152, max_pktsize=32768)[source]¶

Create a remote SSH TCP listener

This method is a coroutine which can be called to request that the server listen on the specified remote address and port for incoming TCP connections. If the request is successful, the return value is an SSHListener object which can be used later to shut down the listener. If the request fails, None is returned.

Parameters:

session_factory (callable or coroutine) – A callable or coroutine which takes arguments of the original host and port of the client and decides whether to accept the connection or not, either returning an SSHTCPSession object used to handle activity on that connection or raising ChannelOpenError to indicate that the connection should not be accepted
listen_host (str) – The hostname or address on the remote host to listen on
listen_port (int) – The port number on the remote host to listen on
encoding (str) – (optional) The Unicode encoding to use for data exchanged on the connection
window (int) – (optional) The receive window size for this session
max_pktsize (int) – (optional) The maximum packet size for this session

Returns:

SSHListener or None if the listener can’t be opened

start_server(handler_factory, *args, **kwargs)[source]¶

Start a remote SSH TCP listener

This method is a coroutine wrapper around create_server() designed to provide a “high-level” stream interface for creating remote SSH TCP listeners. Instead of taking a session_factory argument for constructing an object which will handle activity on the session via callbacks, it takes a handler_factory which returns a callable or coroutine that will be passed SSHReader and SSHWriter objects which can be used to perform I/O on each new connection which arrives. Like create_server(), handler_factory can also raise ChannelOpenError if the connection should not be accepted.

With the exception of handler_factory replacing session_factory, all of the arguments to create_server() are supported and have the same meaning here.

Parameters:	handler_factory (callable or coroutine) – A callable or coroutine which takes arguments of the original host and port of the client and decides whether to accept the connection or not, either returning a callback or coroutine used to handle activity on that connection or raising `ChannelOpenError` to indicate that the connection should not be accepted
Returns:	`SSHListener` or `None` if the listener can’t be opened

create_unix_connection(session_factory, remote_path, *, encoding=None, window=2097152, max_pktsize=32768)[source]¶

Create an SSH UNIX domain socket direct connection

This method is a coroutine which can be called to request that the server open a new outbound UNIX domain socket connection to the specified destination path. If the connection is successfully opened, a new SSH channel will be opened with data being handled by a SSHUNIXSession object created by session_factory.

By default, this class expects data to be sent and received as raw bytes. However, an optional encoding argument can be passed in to select the encoding to use, allowing the application send and receive string data.

Other optional arguments include the SSH receive window size and max packet size which default to 2 MB and 32 KB, respectively.

Parameters:	session_factory (callable) – A callable which returns an `SSHClientSession` object that will be created to handle activity on this session remote_path (str) – The remote path to connect to encoding (str) – (optional) The Unicode encoding to use for data exchanged on the connection window (int) – (optional) The receive window size for this session max_pktsize (int) – (optional) The maximum packet size for this session
Returns:	an `SSHUNIXChannel` and `SSHUNIXSession`
Raises:	`ChannelOpenError` if the connection can’t be opened

open_unix_connection(*args, **kwargs)[source]¶

Open an SSH UNIX domain socket direct connection

This method is a coroutine wrapper around create_unix_connection() designed to provide a “high-level” stream interface for creating an SSH UNIX domain socket direct connection. Instead of taking a session_factory argument for constructing an object which will handle activity on the session via callbacks, it returns SSHReader and SSHWriter objects which can be used to perform I/O on the connection.

With the exception of session_factory, all of the arguments to create_unix_connection() are supported and have the same meaning here.

Returns:	an `SSHReader` and `SSHWriter`
Raises:	`ChannelOpenError` if the connection can’t be opened

create_unix_server(session_factory, listen_path, *, encoding=None, window=2097152, max_pktsize=32768)[source]¶

Create a remote SSH UNIX domain socket listener

This method is a coroutine which can be called to request that the server listen on the specified remote path for incoming UNIX domain socket connections. If the request is successful, the return value is an SSHListener object which can be used later to shut down the listener. If the request fails, None is returned.

Parameters:

session_factory (callable or coroutine) – A callable or coroutine which takes arguments of the original host and port of the client and decides whether to accept the connection or not, either returning an SSHUNIXSession object used to handle activity on that connection or raising ChannelOpenError to indicate that the connection should not be accepted
listen_path (str) – The path on the remote host to listen on
encoding (str) – (optional) The Unicode encoding to use for data exchanged on the connection
window (int) – (optional) The receive window size for this session
max_pktsize (int) – (optional) The maximum packet size for this session

Returns:

SSHListener or None if the listener can’t be opened

start_unix_server(handler_factory, *args, **kwargs)[source]¶

Start a remote SSH UNIX domain socket listener

This method is a coroutine wrapper around create_unix_server() designed to provide a “high-level” stream interface for creating remote SSH UNIX domain socket listeners. Instead of taking a session_factory argument for constructing an object which will handle activity on the session via callbacks, it takes a handler_factory which returns a callable or coroutine that will be passed SSHReader and SSHWriter objects which can be used to perform I/O on each new connection which arrives. Like create_unix_server(), handler_factory can also raise ChannelOpenError if the connection should not be accepted.

With the exception of handler_factory replacing session_factory, all of the arguments to create_unix_server() are supported and have the same meaning here.

Parameters:	handler_factory (callable or coroutine) – A callable or coroutine which takes arguments of the original host and port of the client and decides whether to accept the connection or not, either returning a callback or coroutine used to handle activity on that connection or raising `ChannelOpenError` to indicate that the connection should not be accepted
Returns:	`SSHListener` or `None` if the listener can’t be opened

create_ssh_connection(client_factory, host, port=22, *args, **kwargs)[source]¶

Create a tunneled SSH client connection

This method is a coroutine which can be called to open an SSH client connection to the requested host and port tunneled inside this already established connection. It takes all the same arguments as create_connection() but requests that the upstream SSH server open the connection rather than connecting directly.

connect_ssh(host, port=22, *args, **kwargs)[source]¶

Make a tunneled SSH client connection

This method is a coroutine which can be called to open an SSH client connection to the requested host and port tunneled inside this already established connection. It takes all the same arguments as connect() but requests that the upstream SSH server open the connection rather than connecting directly.

start_sftp_client(path_encoding='utf-8', path_errors='strict')[source]¶

Start an SFTP client

This method is a coroutine which attempts to start a secure file transfer session. If it succeeds, it returns an SFTPClient object which can be used to copy and access files on the remote host.

An optional Unicode encoding can be specified for sending and receiving pathnames, defaulting to UTF-8 with strict error checking. If an encoding of None is specified, pathnames will be left as bytes rather than being converted to & from strings.

Parameters:	path_encoding (str) – The Unicode encoding to apply when sending and receiving remote pathnames path_errors (str) – The error handling strategy to apply on encode/decode errors
Returns:	`SFTPClient`
Raises:	`SFTPError` if the session can’t be opened

Client forwarding methods

forward_connection(dest_host, dest_port)¶

Forward a tunneled TCP connection

This method is a coroutine which can be returned by a session_factory to forward connections tunneled over SSH to the specified destination host and port.

Parameters:	dest_host (str) – The hostname or address to forward the connections to dest_port (int) – The port number to forward the connections to
Returns:	`SSHTCPSession`

forward_local_port(listen_host, listen_port, dest_host, dest_port)¶

Set up local port forwarding

This method is a coroutine which attempts to set up port forwarding from a local listening port to a remote host and port via the SSH connection. If the request is successful, the return value is an SSHListener object which can be used later to shut down the port forwarding.

Parameters:	listen_host (str) – The hostname or address on the local host to listen on listen_port (int) – The port number on the local host to listen on dest_host (str) – The hostname or address to forward the connections to dest_port (int) – The port number to forward the connections to
Returns:	`SSHListener`
Raises:	`OSError` if the listener can’t be opened

forward_local_path(listen_path, dest_path)¶

Set up local UNIX domain socket forwarding

This method is a coroutine which attempts to set up UNIX domain socket forwarding from a local listening path to a remote path via the SSH connection. If the request is successful, the return value is an SSHListener object which can be used later to shut down the UNIX domain socket forwarding.

Parameters:	listen_path (str) – The path on the local host to listen on dest_path (str) – The path on the remote host to forward the connections to
Returns:	`SSHListener`
Raises:	`OSError` if the listener can’t be opened

forward_remote_port(listen_host, listen_port, dest_host, dest_port)[source]¶

Set up remote port forwarding

This method is a coroutine which attempts to set up port forwarding from a remote listening port to a local host and port via the SSH connection. If the request is successful, the return value is an SSHListener object which can be used later to shut down the port forwarding. If the request fails, None is returned.

Parameters:	listen_host (str) – The hostname or address on the remote host to listen on listen_port (int) – The port number on the remote host to listen on dest_host (str) – The hostname or address to forward connections to dest_port (int) – The port number to forward connections to
Returns:	`SSHListener` or `None` if the listener can’t be opened

forward_remote_path(listen_path, dest_path)[source]¶

Set up remote UNIX domain socket forwarding

This method is a coroutine which attempts to set up UNIX domain socket forwarding from a remote listening path to a local path via the SSH connection. If the request is successful, the return value is an SSHListener object which can be used later to shut down the port forwarding. If the request fails, None is returned.

Parameters:	listen_path (str) – The path on the remote host to listen on dest_path (str) – The path on the local host to forward connections to
Returns:	`SSHListener` or `None` if the listener can’t be opened

Connection close methods

abort()¶

Forcibly close the SSH connection

This method closes the SSH connection immediately, without waiting for pending operations to complete and wihtout sending an explicit SSH disconnect message. Buffered data waiting to be sent will be lost and no more data will be received. When the the connection is closed, connection_lost() on the associated SSHClient object will be called with the value None.

close()¶

Cleanly close the SSH connection

This method calls disconnect() with the reason set to indicate that the connection was closed explicitly by the application.

disconnect(code, reason, lang='en-US')¶

Disconnect the SSH connection

This method sends a disconnect message and closes the SSH connection after buffered data waiting to be written has been sent. No more data will be received. When the connection is fully closed, connection_lost() on the associated SSHClient or SSHServer object will be called with the value None.

Parameters:	code (int) – The reason for the disconnect, from disconnect reason codes reason (str) – A human readable reason for the disconnect lang (str) – The language the reason is in

wait_closed()¶

Wait for this connection to close

This method is a coroutine which can be called to block until this connection has finished closing.

SSHServerConnection¶

class asyncssh.SSHServerConnection[source]¶

SSH server connection

This class represents an SSH server connection.

During authentication, send_auth_banner() can be called to send an authentication banner to the client.

Once authenticated, SSHServer objects wishing to create session objects with non-default channel properties can call create_server_channel() from their session_requested() method and return a tuple of the SSHServerChannel object returned from that and either an SSHServerSession object or a coroutine which returns an SSHServerSession.

Similarly, SSHServer objects wishing to create TCP connection objects with non-default channel properties can call create_tcp_channel() from their connection_requested() method and return a tuple of the SSHTCPChannel object returned from that and either an SSHTCPSession object or a coroutine which returns an SSHTCPSession.

SSHServer objects wishing to create UNIX domain socket connection objects with non-default channel properties can call create_unix_channel() from the unix_connection_requested() <SSHServer.unix_connection_requested>' method and return a tuple of the :class:`SSHUNIXChannel() object returned from that and either an SSHUNIXSession object or a coroutine which returns an SSHUNIXSession.

General connection methods

get_extra_info(name, default=None)¶

Get additional information about the connection

This method returns extra information about the connection once it is established. Supported values include everything supported by a socket transport plus:

username

client_version

server_version

send_cipher

send_mac

send_compression

recv_cipher

recv_mac

recv_compression

See get_extra_info() in asyncio.BaseTransport for more information.

send_debug(msg, lang='en-US', always_display=False)¶

Send a debug message on this connection

This method can be called to send a debug message to the other end of the connection.

Parameters:	msg (str) – The debug message to send lang (str) – The language the message is in always_display (bool) – Whether or not to display the message

Server authentication methods

send_auth_banner(msg, lang='en-US')[source]¶

Send an authentication banner to the client

This method can be called to send an authentication banner to the client, displaying information while authentication is in progress. It is an error to call this method after the authentication is complete.

Parameters:	msg (str) – The message to display lang (str) – The language the message is in
Raises:	`OSError` if authentication is already completed

set_authorized_keys(authorized_keys)[source]¶

Set the keys trusted for client public key authentication

This method can be called to set the trusted user and CA keys for client public key authentication. It should generally be called from the begin_auth method of SSHServer to set the appropriate keys for the user attempting to authenticate.

Parameters:	authorized_keys (see Specifying authorized keys) – The keys to trust for client public key authentication

get_key_option(option, default=None)[source]¶

Return option from authorized_keys

If a client key or certificate was presented during authentication, this method returns the value of the requested option in the corresponding authorized_keys entry if it was set. Otherwise, it returns the default value provided.

The following standard options are supported:

command (string)

environment (dictionary of name/value pairs)

from (list of host patterns)

permitopen (list of host/port tuples)

principals (list of usernames)

Non-standard options are also supported and will return the value True if the option is present without a value or return a list of strings containing the values associated with each occurrence of that option name. If the option is not present, the specified default value is returned.

Parameters:	option (str) – The name of the option to look up. default – The default value to return if the option is not present.
Returns:	The value of the option in authorized_keys, if set

check_key_permission(permission)[source]¶

Check permissions in authorized_keys

If a client key or certificate was presented during authentication, this method returns whether the specified permission is allowed by the corresponding authorized_keys entry. By default, all permissions are granted, but they can be revoked by specifying an option starting with ‘no-‘ without a value.

The following standard options are supported:

X11-forwarding

agent-forwarding

port-forwarding

pty

user-rc

AsyncSSH internally enforces agent-forwarding, port-forwarding and pty permissions but ignores the other values since it does not implement those features.

Non-standard permissions can also be checked, as long as the option follows the convention of starting with ‘no-‘.

Parameters:	permission (str) – The name of the permission to check (without the ‘no-‘).
Returns:	A bool indicating if the permission is granted.

get_certificate_option(option, default=None)[source]¶

Return option from user certificate

If a user certificate was presented during authentication, this method returns the value of the requested option in the certificate if it was set. Otherwise, it returns the default value provided.

The following options are supported:

force-command (string)

source-address (list of CIDR-style IP network addresses)

Parameters:	option (str) – The name of the option to look up. default – The default value to return if the option is not present.
Returns:	The value of the option in the user certificate, if set

check_certificate_permission(permission)[source]¶

Check permissions in user certificate

If a user certificate was presented during authentication, this method returns whether the specified permission was granted in the certificate. Otherwise, it acts as if all permissions are granted and returns True.

The following permissions are supported:

X11-forwarding

agent-forwarding

port-forwarding

pty

user-rc

AsyncSSH internally enforces agent-forwarding, port-forwarding and pty permissions but ignores the other values since it does not implement those features.

Parameters:	permission (str) – The name of the permission to check (without the ‘permit-‘).
Returns:	A bool indicating if the permission is granted.

Server connection open methods

create_connection(session_factory, remote_host, remote_port, orig_host='', orig_port=0, *, encoding=None, window=2097152, max_pktsize=32768)[source]¶

Create an SSH TCP forwarded connection

This method is a coroutine which can be called to notify the client about a new inbound TCP connection arriving on the specified remote host and port. If the connection is successfully opened, a new SSH channel will be opened with data being handled by a SSHTCPSession object created by session_factory.

Optional arguments include the host and port of the original client opening the connection when performing TCP port forwarding.

By default, this class expects data to be sent and received as raw bytes. However, an optional encoding argument can be passed in to select the encoding to use, allowing the application send and receive string data.

Other optional arguments include the SSH receive window size and max packet size which default to 2 MB and 32 KB, respectively.

Parameters:

session_factory (callable) – A callable which returns an SSHClientSession object that will be created to handle activity on this session
remote_host (str) – The hostname or address the connection was received on
remote_port (int) – The port number the connection was received on
orig_host (str) – (optional) The hostname or address of the client requesting the connection
orig_port (int) – (optional) The port number of the client requesting the connection
encoding (str) – (optional) The Unicode encoding to use for data exchanged on the connection
window (int) – (optional) The receive window size for this session
max_pktsize (int) – (optional) The maximum packet size for this session

Returns:

an SSHTCPChannel and SSHTCPSession

open_connection(*args, **kwargs)[source]¶

Open an SSH TCP forwarded connection

This method is a coroutine wrapper around create_connection() designed to provide a “high-level” stream interface for creating an SSH TCP forwarded connection. Instead of taking a session_factory argument for constructing an object which will handle activity on the session via callbacks, it returns SSHReader and SSHWriter objects which can be used to perform I/O on the connection.

With the exception of session_factory, all of the arguments to create_connection() are supported and have the same meaning here.

Returns:	an `SSHReader` and `SSHWriter`

create_unix_connection(session_factory, remote_path, *, encoding=None, window=2097152, max_pktsize=32768)[source]¶

Create an SSH UNIX domain socket forwarded connection

This method is a coroutine which can be called to notify the client about a new inbound UNIX domain socket connection arriving on the specified remote path. If the connection is successfully opened, a new SSH channel will be opened with data being handled by a SSHUNIXSession object created by session_factory.

By default, this class expects data to be sent and received as raw bytes. However, an optional encoding argument can be passed in to select the encoding to use, allowing the application send and receive string data.

Other optional arguments include the SSH receive window size and max packet size which default to 2 MB and 32 KB, respectively.

Parameters:

session_factory (callable) – A callable which returns an SSHClientSession object that will be created to handle activity on this session
remote_path (str) – The path the connection was received on
encoding (str) – (optional) The Unicode encoding to use for data exchanged on the connection
window (int) – (optional) The receive window size for this session
max_pktsize (int) – (optional) The maximum packet size for this session

Returns:

an SSHTCPChannel and SSHUNIXSession

open_unix_connection(*args, **kwargs)[source]¶

Open an SSH UNIX domain socket forwarded connection

This method is a coroutine wrapper around create_unix_connection() designed to provide a “high-level” stream interface for creating an SSH UNIX domain socket forwarded connection. Instead of taking a session_factory argument for constructing an object which will handle activity on the session via callbacks, it returns SSHReader and SSHWriter objects which can be used to perform I/O on the connection.

With the exception of session_factory, all of the arguments to create_unix_connection() are supported and have the same meaning here.

Returns:	an `SSHReader` and `SSHWriter`

Server forwarding methods

forward_connection(dest_host, dest_port)¶

Forward a tunneled TCP connection

This method is a coroutine which can be returned by a session_factory to forward connections tunneled over SSH to the specified destination host and port.

Parameters:	dest_host (str) – The hostname or address to forward the connections to dest_port (int) – The port number to forward the connections to
Returns:	`SSHTCPSession`

forward_unix_connection(dest_path)¶

Forward a tunneled UNIX domain socket connection

This method is a coroutine which can be returned by a session_factory to forward connections tunneled over SSH to the specified destination path.

Parameters:	dest_path (str) – The path to forward the connection to
Returns:	`SSHUNIXSession`

Server channel creation methods

create_server_channel(encoding='utf-8', window=2097152, max_pktsize=32768)[source]¶

Create an SSH server channel for a new SSH session

This method can be called by session_requested() to create an SSHServerChannel with the desired encoding, window, and max packet size for a newly created SSH server session.

Parameters:	encoding (str) – (optional) The Unicode encoding to use for data exchanged on the session, defaulting to UTF-8 (ISO 10646) format. If `None` is passed in, the application can send and receive raw bytes. window (int) – (optional) The receive window size for this session max_pktsize (int) – (optional) The maximum packet size for this session
Returns:	`SSHServerChannel`

create_tcp_channel(encoding=None, window=2097152, max_pktsize=32768)¶

Create an SSH TCP channel for a new direct TCP connection

This method can be called by connection_requested() to create an SSHTCPChannel with the desired encoding, window, and max packet size for a newly created SSH direct connection.

Parameters:	encoding (str) – (optional) The Unicode encoding to use for data exchanged on the connection. This defaults to `None`, allowing the application to send and receive raw bytes. window (int) – (optional) The receive window size for this session max_pktsize (int) – (optional) The maximum packet size for this session
Returns:	`SSHTCPChannel`

create_unix_channel(encoding=None, window=2097152, max_pktsize=32768)¶

Create an SSH UNIX channel for a new direct UNIX domain connection

This method can be called by unix_connection_requested() to create an SSHUNIXChannel with the desired encoding, window, and max packet size for a newly created SSH direct UNIX domain socket connection.

Parameters:	encoding (str) – (optional) The Unicode encoding to use for data exchanged on the connection. This defaults to `None`, allowing the application to send and receive raw bytes. window (int) – (optional) The receive window size for this session max_pktsize (int) – (optional) The maximum packet size for this session
Returns:	`SSHUNIXChannel`

Connection close methods

abort()¶

Forcibly close the SSH connection

This method closes the SSH connection immediately, without waiting for pending operations to complete and wihtout sending an explicit SSH disconnect message. Buffered data waiting to be sent will be lost and no more data will be received. When the the connection is closed, connection_lost() on the associated SSHClient object will be called with the value None.

close()¶

Cleanly close the SSH connection

This method calls disconnect() with the reason set to indicate that the connection was closed explicitly by the application.

disconnect(code, reason, lang='en-US')¶

Disconnect the SSH connection

This method sends a disconnect message and closes the SSH connection after buffered data waiting to be written has been sent. No more data will be received. When the connection is fully closed, connection_lost() on the associated SSHClient or SSHServer object will be called with the value None.

Parameters:	code (int) – The reason for the disconnect, from disconnect reason codes reason (str) – A human readable reason for the disconnect lang (str) – The language the reason is in

wait_closed()¶

Wait for this connection to close

This method is a coroutine which can be called to block until this connection has finished closing.

Session Classes¶

SSHClientSession¶

class asyncssh.SSHClientSession[source]¶

SSH client session handler

Applications should subclass this when implementing an SSH client session handler. The functions listed below should be implemented to define application-specific behavior. In particular, the standard asyncio protocol methods such as connection_made(), connection_lost(), data_received(), eof_received(), pause_writing(), and resume_writing() are all supported. In addition, session_started() is called as soon as the SSH session is fully started, xon_xoff_requested() can be used to determine if the server wants the client to support XON/XOFF flow control, and exit_status_received() and exit_signal_received() can be used to receive session exit information.

General session handlers

connection_made(chan)¶

Called when a channel is opened successfully

This method is called when a channel is opened successfully. The channel parameter should be stored if needed for later use.

Parameters:	chan (`SSHClientChannel`) – The channel which was successfully opened.

connection_lost(exc)¶

Called when a channel is closed

This method is called when a channel is closed. If the channel is shut down cleanly, exc will be None. Otherwise, it will be an exception explaining the reason for the channel close.

Parameters:	exc (`Exception`) – The exception which caused the channel to close, or `None` if the channel closed cleanly.

session_started()¶

Called when the session is started

This method is called when a session has started up. For client and server sessions, this will be called once a shell, exec, or subsystem request has been successfully completed. For TCP and UNIX domain socket sessions, it will be called immediately after the connection is opened.

General session read handlers

data_received(data, datatype)¶

Called when data is received on the channel

This method is called when data is received on the channel. If an encoding was specified when the channel was created, the data will be delivered as a string after decoding with the requested encoding. Otherwise, the data will be delivered as bytes.

Parameters:	data (str or bytes) – The data received on the channel datatype – The extended data type of the data, from extended data types

eof_received()¶

Called when EOF is received on the channel

This method is called when an end-of-file indication is received on the channel, after which no more data will be received. If this method returns True, the channel remains half open and data may still be sent. Otherwise, the channel is automatically closed after this method returns. This is the default behavior.

General session write handlers
`pause_writing`()¶ Called when the write buffer becomes full This method is called when the channel’s write buffer becomes full and no more data can be sent until the remote system adjusts its window. While data can still be buffered locally, applications may wish to stop producing new data until the write buffer has drained.
`resume_writing`()¶ Called when the write buffer has sufficiently drained This method is called when the channel’s send window reopens and enough data has drained from the write buffer to allow the application to produce more data.

Other client session handlers

xon_xoff_requested(client_can_do)[source]¶

XON/XOFF flow control has been enabled or disabled

This method is called to notify the client whether or not to enable XON/XOFF flow control. If client_can_do is True and output is being sent to an interactive terminal the application should allow input of Control-S and Control-Q to pause and resume output, respectively. If client_can_do is False, Control-S and Control-Q should be treated as normal input and passed through to the server. Non-interactive applications can ignore this request.

By default, this message is ignored.

Parameters:	client_can_do (bool) – Whether or not to enable XON/XOFF flow control

exit_status_received(status)[source]¶

A remote exit status has been received for this session

This method is called when the shell, command, or subsystem running on the server terminates and returns an exit status. A zero exit status generally means that the operation was successful. This call will generally be followed by a call to connection_lost().

By default, the exit status is ignored.

Parameters:	status (int) – The exit status returned by the remote process

exit_signal_received(signal, core_dumped, msg, lang)[source]¶

A remote exit signal has been received for this session

This method is called when the shell, command, or subsystem running on the server terminates abnormally with a signal. A more detailed error may also be provided, along with an indication of whether the remote process dumped core. This call will generally be followed by a call to connection_lost().

By default, exit signals are ignored.

Parameters:	signal (str) – The signal which caused the remote process to exit core_dumped (bool) – Whether or not the remote process dumped core msg – Details about what error occurred lang – The language the error message is in

SSHServerSession¶

class asyncssh.SSHServerSession[source]¶

SSH server session handler

Applications should subclass this when implementing an SSH server session handler. The functions listed below should be implemented to define application-specific behavior. In particular, the standard asyncio protocol methods such as connection_made(), connection_lost(), data_received(), eof_received(), pause_writing(), and resume_writing() are all supported. In addition, pty_requested() is called when the client requests a pseudo-terminal, one of shell_requested(), exec_requested(), or subsystem_requested() is called depending on what type of session the client wants to start, session_started() is called once the SSH session is fully started, terminal_size_changed() is called when the client’s terminal size changes, signal_received() is called when the client sends a signal, and break_received() is called when the client sends a break.

General session handlers

connection_made(chan)¶

Called when a channel is opened successfully

This method is called when a channel is opened successfully. The channel parameter should be stored if needed for later use.

Parameters:	chan (`SSHClientChannel`) – The channel which was successfully opened.

connection_lost(exc)¶

Called when a channel is closed

This method is called when a channel is closed. If the channel is shut down cleanly, exc will be None. Otherwise, it will be an exception explaining the reason for the channel close.

Parameters:	exc (`Exception`) – The exception which caused the channel to close, or `None` if the channel closed cleanly.

session_started()¶

Called when the session is started

This method is called when a session has started up. For client and server sessions, this will be called once a shell, exec, or subsystem request has been successfully completed. For TCP and UNIX domain socket sessions, it will be called immediately after the connection is opened.

Server session open handlers

pty_requested(term_type, term_size, term_modes)[source]¶

A psuedo-terminal has been requested

This method is called when the client sends a request to allocate a pseudo-terminal with the requested terminal type, size, and POSIX terminal modes. This method should return True if the request for the pseudo-terminal is accepted. Otherwise, it should return False to reject the request.

By default, requests to allocate a pseudo-terminal are accepted but nothing is done with the associated terminal information. Applications wishing to use this information should implement this method and have it return True, or call get_terminal_type(), get_terminal_size(), or get_terminal_mode() on the SSHServerChannel to get the information they need after a shell, command, or subsystem is started.

Parameters:

term_type (str) – Terminal type to set for this session
term_size (tuple) – Terminal size to set for this session provided as a tuple of four integers: the width and height of the terminal in characters followed by the width and height of the terminal in pixels
term_modes (dictionary) – POSIX terminal modes to set for this session, where keys are taken from POSIX terminal modes with values defined in section 8 of RFC 4254#section-8.

Returns:

A bool indicating if the request for a pseudo-terminal was allowed or not

shell_requested()[source]¶

The client has requested a shell

This method should be implemented by the application to perform whatever processing is required when a client makes a request to open an interactive shell. It should return True to accept the request, or False to reject it.

If the application returns True, the session_started() method will be called once the channel is fully open. No output should be sent until this method is called.

By default this method returns False to reject all requests.

Returns:	A bool indicating if the shell request was allowed or not

exec_requested(command)[source]¶

The client has requested to execute a command

This method should be implemented by the application to perform whatever processing is required when a client makes a request to execute a command. It should return True to accept the request, or False to reject it.

If the application returns True, the session_started() method will be called once the channel is fully open. No output should be sent until this method is called.

By default this method returns False to reject all requests.

Parameters:	command (str) – The command the client has requested to execute
Returns:	A bool indicating if the exec request was allowed or not

subsystem_requested(subsystem)[source]¶

The client has requested to start a subsystem

This method should be implemented by the application to perform whatever processing is required when a client makes a request to start a subsystem. It should return True to accept the request, or False to reject it.

If the application returns True, the session_started() method will be called once the channel is fully open. No output should be sent until this method is called.

By default this method returns False to reject all requests.

Parameters:	subsystem (str) – The subsystem to start
Returns:	A bool indicating if the request to open the subsystem was allowed or not

General session read handlers

data_received(data, datatype)¶

Called when data is received on the channel

This method is called when data is received on the channel. If an encoding was specified when the channel was created, the data will be delivered as a string after decoding with the requested encoding. Otherwise, the data will be delivered as bytes.

Parameters:	data (str or bytes) – The data received on the channel datatype – The extended data type of the data, from extended data types

eof_received()¶

Called when EOF is received on the channel

This method is called when an end-of-file indication is received on the channel, after which no more data will be received. If this method returns True, the channel remains half open and data may still be sent. Otherwise, the channel is automatically closed after this method returns. This is the default behavior.

General session write handlers
`pause_writing`()¶ Called when the write buffer becomes full This method is called when the channel’s write buffer becomes full and no more data can be sent until the remote system adjusts its window. While data can still be buffered locally, applications may wish to stop producing new data until the write buffer has drained.
`resume_writing`()¶ Called when the write buffer has sufficiently drained This method is called when the channel’s send window reopens and enough data has drained from the write buffer to allow the application to produce more data.

Other server session handlers

break_received(msec)[source]¶

The client has sent a break

This method is called when the client requests that the server perform a break operation on the terminal. If the break is performed, this method should return True. Otherwise, it should return False.

By default, this method returns False indicating that no break was performed.

Parameters:	msec (int) – The duration of the break in milliseconds
Returns:	A bool to indicate if the break operation was performed or not

signal_received(signal)[source]¶

The client has sent a signal

This method is called when the client delivers a signal on the channel.

By default, signals from the client are ignored.

terminal_size_changed(width, height, pixwidth, pixheight)[source]¶

The terminal size has changed

This method is called when a client requests a pseudo-terminal and again whenever the the size of he client’s terminal window changes.

By default, this information is ignored, but applications wishing to use the terminal size can implement this method to get notified whenever it changes.

Parameters:	width (int) – The width of the terminal in characters height (int) – The height of the terminal in characters pixwidth (int) – (optional) The width of the terminal in pixels pixheight (int) – (optional) The height of the terminal in pixels

SSHTCPSession¶

class asyncssh.SSHTCPSession[source]¶

SSH TCP session handler

Applications should subclass this when implementing a handler for SSH direct or forwarded TCP connections.

SSH client applications wishing to open a direct connection should call create_connection() on their SSHClientConnection, passing in a factory which returns instances of this class.

Server applications wishing to allow direct connections should implement the coroutine connection_requested() on their SSHServer object and have it return instances of this class.

Server applications wishing to allow connection forwarding back to the client should implement the coroutine server_requested() on their SSHServer object and call create_connection() on their SSHServerConnection for each new connection, passing it a factory which returns instances of this class.

When a connection is successfully opened, session_started() will be called, after which the application can begin sending data. Received data will be passed to the data_received() method.

General session handlers

connection_made(chan)¶

Called when a channel is opened successfully

This method is called when a channel is opened successfully. The channel parameter should be stored if needed for later use.

Parameters:	chan (`SSHClientChannel`) – The channel which was successfully opened.

connection_lost(exc)¶

Called when a channel is closed

This method is called when a channel is closed. If the channel is shut down cleanly, exc will be None. Otherwise, it will be an exception explaining the reason for the channel close.

Parameters:	exc (`Exception`) – The exception which caused the channel to close, or `None` if the channel closed cleanly.

session_started()¶

Called when the session is started

This method is called when a session has started up. For client and server sessions, this will be called once a shell, exec, or subsystem request has been successfully completed. For TCP and UNIX domain socket sessions, it will be called immediately after the connection is opened.

General session read handlers

data_received(data, datatype)¶

Called when data is received on the channel

This method is called when data is received on the channel. If an encoding was specified when the channel was created, the data will be delivered as a string after decoding with the requested encoding. Otherwise, the data will be delivered as bytes.

Parameters:	data (str or bytes) – The data received on the channel datatype – The extended data type of the data, from extended data types

eof_received()¶

Called when EOF is received on the channel

This method is called when an end-of-file indication is received on the channel, after which no more data will be received. If this method returns True, the channel remains half open and data may still be sent. Otherwise, the channel is automatically closed after this method returns. This is the default behavior.

General session write handlers
`pause_writing`()¶ Called when the write buffer becomes full This method is called when the channel’s write buffer becomes full and no more data can be sent until the remote system adjusts its window. While data can still be buffered locally, applications may wish to stop producing new data until the write buffer has drained.
`resume_writing`()¶ Called when the write buffer has sufficiently drained This method is called when the channel’s send window reopens and enough data has drained from the write buffer to allow the application to produce more data.

SSHUNIXSession¶

class asyncssh.SSHUNIXSession[source]¶

SSH UNIX domain socket session handler

Applications should subclass this when implementing a handler for SSH direct or forwarded UNIX domain socket connections.

SSH client applications wishing to open a direct connection should call create_unix_connection() on their SSHClientConnection, passing in a factory which returns instances of this class.

Server applications wishing to allow direct connections should implement the coroutine unix_connection_requested() on their SSHServer object and have it return instances of this class.

Server applications wishing to allow connection forwarding back to the client should implement the coroutine unix_server_requested() on their SSHServer object and call create_unix_connection() on their SSHServerConnection for each new connection, passing it a factory which returns instances of this class.

When a connection is successfully opened, session_started() will be called, after which the application can begin sending data. Received data will be passed to the data_received() method.

General session handlers

connection_made(chan)¶

Called when a channel is opened successfully

This method is called when a channel is opened successfully. The channel parameter should be stored if needed for later use.

Parameters:	chan (`SSHClientChannel`) – The channel which was successfully opened.

connection_lost(exc)¶

Called when a channel is closed

This method is called when a channel is closed. If the channel is shut down cleanly, exc will be None. Otherwise, it will be an exception explaining the reason for the channel close.

Parameters:	exc (`Exception`) – The exception which caused the channel to close, or `None` if the channel closed cleanly.

session_started()¶

Called when the session is started

This method is called when a session has started up. For client and server sessions, this will be called once a shell, exec, or subsystem request has been successfully completed. For TCP and UNIX domain socket sessions, it will be called immediately after the connection is opened.

General session read handlers

data_received(data, datatype)¶

Called when data is received on the channel

This method is called when data is received on the channel. If an encoding was specified when the channel was created, the data will be delivered as a string after decoding with the requested encoding. Otherwise, the data will be delivered as bytes.

Parameters:	data (str or bytes) – The data received on the channel datatype – The extended data type of the data, from extended data types

eof_received()¶

Called when EOF is received on the channel

This method is called when an end-of-file indication is received on the channel, after which no more data will be received. If this method returns True, the channel remains half open and data may still be sent. Otherwise, the channel is automatically closed after this method returns. This is the default behavior.

General session write handlers
`pause_writing`()¶ Called when the write buffer becomes full This method is called when the channel’s write buffer becomes full and no more data can be sent until the remote system adjusts its window. While data can still be buffered locally, applications may wish to stop producing new data until the write buffer has drained.
`resume_writing`()¶ Called when the write buffer has sufficiently drained This method is called when the channel’s send window reopens and enough data has drained from the write buffer to allow the application to produce more data.

Channel Classes¶

SSHClientChannel¶

class asyncssh.SSHClientChannel[source]¶

SSH client channel

General channel methods

get_extra_info(name, default=None)¶

Get additional information about the channel

This method returns extra information about the channel once it is established. Supported values include 'connection' to return the SSH connection this channel is running over plus all of the values supported on that connection.

For TCP channels, the values 'local_peername' and 'remote_peername' are added to return the local and remote host and port information for the tunneled TCP connection.

For UNIX channels, the values 'local_peername' and 'remote_peername' are added to return the local and remote path information for the tunneled UNIX domain socket connection. Since UNIX domain sockets provide no “source” address, only one of these will be filled in.

See get_extra_info() on SSHClientConnection for more information.

Client channel read methods

pause_reading()¶

Pause delivery of incoming data

This method is used to temporarily suspend delivery of incoming channel data. After this call, incoming data will no longer be delivered until resume_reading() is called. Data will be buffered locally up to the configured SSH channel window size, but window updates will no longer be sent, eventually causing back pressure on the remote system.

Note

Channel close notifications are not suspended by this call. If the remote system closes the channel while delivery is suspended, the channel will be closed even though some buffered data may not have been delivered.

resume_reading()¶

Resume delivery of incoming data

This method can be called to resume delivery of incoming data which was suspended by a call to pause_reading(). As soon as this method is called, any buffered data will be delivered immediately. A pending end-of-file notication may also be delivered if one was queued while reading was paused.

Client channel write methods

can_write_eof()¶

Return whether the channel supports write_eof()

This method always returns True.

get_write_buffer_size()¶

Return the current size of the channel’s output buffer

This method returns how many bytes are currently in the channel’s output buffer waiting to be written.

set_write_buffer_limits(high=None, low=None)¶

Set the high- and low-water limits for write flow control

This method sets the limits used when deciding when to call the pause_writing() and resume_writing() methods on SSH sessions. Writing will be paused when the write buffer size exceeds the high-water mark, and resumed when the write buffer size equals or drops below the low-water mark.

write(data, datatype=None)¶

Write data on the channel

This method can be called to send data on the channel. If an encoding was specified when the channel was created, the data should be provided as a string and will be converted using that encoding. Otherwise, the data should be provided as bytes.

An extended data type can optionally be provided. For instance, this is used from a SSHServerSession to write data to stderr.

Parameters:	data (str or bytes) – The data to send on the channel datatype (int) – (optional) The extended data type of the data, from extended data types
Raises:	`OSError` if the channel isn’t open for sending or the extended data type is not valid for this type of channel

writelines(list_of_data, datatype=None)¶

Write a list of data bytes on the channel

This method can be called to write a list (or any iterable) of data bytes to the channel. It is functionality equivalent to calling write() on each element in the list.

Parameters:	list_of_data (iterable of str or bytes objects) – The data to send on the channel datatype (int) – (optional) The extended data type of the data, from extended data types
Raises:	`OSError` if the channel isn’t open for sending or the extended data type is not valid for this type of channel

write_eof()¶

Write EOF on the channel

This method sends an end-of-file indication on the channel, after which no more data can be sent. The channel remains open, though, and data may still be sent in the other direction.

Raises:	`OSError` if the channel isn’t open for sending

Other client channel methods

get_exit_status()[source]¶

Return the session’s exit status

This method returns the exit status of the session if one has been sent. If an exit signal was received, this method returns -1 and the exit signal information can be collected by calling get_exit_signal(). If neither has been sent, this method returns None.

get_exit_signal()[source]¶

Return the session’s exit signal, if one was sent

This method returns information about the exit signal sent on this session. If an exit signal was sent, a tuple is returned containing the signal name, a boolean for whether a core dump occurred, a message associated with the signal, and the language the message was in. If no exit signal was sent, None is returned.

change_terminal_size(width, height, pixwidth=0, pixheight=0)[source]¶

Change the terminal window size for this session

This method changes the width and height of the terminal associated with this session.

Parameters:	width (int) – The width of the terminal in characters height (int) – The height of the terminal in characters pixwidth (int) – (optional) The width of the terminal in pixels pixheight (int) – (optional) The height of the terminal in pixels

send_break(msec)[source]¶

Send a break to the remote process

This method requests that the server perform a break operation on the remote process or service as described in RFC 4335.

Parameters:	msec (int) – The duration of the break in milliseconds
Raises:	`OSError` if the channel is not open

send_signal(signal)[source]¶

Send a signal to the remote process

This method can be called to deliver a signal to the remote process or service. Signal names should be as described in section 6.10 of RFC 4254#section-6.10.

Parameters:	signal (str) – The signal to deliver
Raises:	`OSError` if the channel is not open

kill()[source]¶

Forcibly kill the remote process

This method can be called to forcibly stop the remote process or service by sending it a KILL signal.

Raises:	`OSError` if the channel is not open

terminate()[source]¶

Terminate the remote process

This method can be called to terminate the remote process or service by sending it a TERM signal.

Raises:	`OSError` if the channel is not open

General channel close methods
`abort`()¶ Forcibly close the channel This method can be called to forcibly close the channel, after which no more data can be sent or received. Any unsent buffered data and any incoming data in flight will be discarded.
`close`()¶ Cleanly close the channel This method can be called to cleanly close the channel, after which no more data can be sent or received. Any unsent buffered data will be flushed asynchronously before the channel is closed.
`wait_closed`()¶ Wait for this channel to close This method is a coroutine which can be called to block until this channel has finished closing.

SSHServerChannel¶

class asyncssh.SSHServerChannel[source]¶

SSH server channel

General channel methods

get_extra_info(name, default=None)¶

Get additional information about the channel

This method returns extra information about the channel once it is established. Supported values include 'connection' to return the SSH connection this channel is running over plus all of the values supported on that connection.

For TCP channels, the values 'local_peername' and 'remote_peername' are added to return the local and remote host and port information for the tunneled TCP connection.

For UNIX channels, the values 'local_peername' and 'remote_peername' are added to return the local and remote path information for the tunneled UNIX domain socket connection. Since UNIX domain sockets provide no “source” address, only one of these will be filled in.

See get_extra_info() on SSHClientConnection for more information.

Server channel info methods

get_environment()[source]¶

Return the environment for this session

This method returns the environment set by the client when the session was opened. Calls to this method should only be made after session_started has been called on the SSHServerSession.

Returns:	A dictionary containing the environment variables set by the client

get_command()[source]¶

Return the command the client requested to execute, if any

This method returns the command the client requested to execute when the session was opened, if any. If the client did not request that a command be executed, this method will return None. Calls to this method should only be made after session_started has been called on the SSHServerSession. When using the stream-based API, calls to this can be made at any time after the handler function has started up.

get_subsystem()[source]¶

Return the subsystem the client requested to open, if any

This method returns the subsystem the client requested to open when the session was opened, if any. If the client did not request that a subsystem be opened, this method will return None. Calls to this method should only be made after session_started has been called on the SSHServerSession. When using the stream-based API, calls to this can be made at any time after the handler function has started up.

get_terminal_type()[source]¶

Return the terminal type for this session

This method returns the terminal type set by the client when the session was opened. If the client didn’t request a pseudo-terminal, this method will return None. Calls to this method should only be made after session_started has been called on the SSHServerSession. When using the stream-based API, calls to this can be made at any time after the handler function has started up.

Returns:	A str containing the terminal type or `None` if no pseudo-terminal was requested

get_terminal_size()[source]¶

Return terminal size information for this session

This method returns the latest terminal size information set by the client. If the client didn’t set any terminal size information, all values returned will be zero. Calls to this method should only be made after session_started has been called on the SSHServerSession. When using the stream-based API, calls to this can be made at any time after the handler function has started up.

Also see terminal_size_changed() or the TerminalSizeChanged exception for how to get notified when the terminal size changes.

Returns:	A tuple of four integers containing the width and height of the terminal in characters and the width and height of the terminal in pixels

get_terminal_mode(mode)[source]¶

Return the requested TTY mode for this session

This method looks up the value of a POSIX terminal mode set by the client when the session was opened. If the client didn’t request a pseudo-terminal or didn’t set the requested TTY mode opcode, this method will return None. Calls to this method should only be made after session_started has been called on the SSHServerSession. When using the stream-based API, calls to this can be made at any time after the handler function has started up.

Parameters:	mode (int) – POSIX terminal mode taken from POSIX terminal modes to look up
Returns:	An int containing the value of the requested POSIX terminal mode or `None` if the requested mode was not set

Server channel read methods

pause_reading()¶

Pause delivery of incoming data

This method is used to temporarily suspend delivery of incoming channel data. After this call, incoming data will no longer be delivered until resume_reading() is called. Data will be buffered locally up to the configured SSH channel window size, but window updates will no longer be sent, eventually causing back pressure on the remote system.

Note

Channel close notifications are not suspended by this call. If the remote system closes the channel while delivery is suspended, the channel will be closed even though some buffered data may not have been delivered.

resume_reading()¶

Resume delivery of incoming data

This method can be called to resume delivery of incoming data which was suspended by a call to pause_reading(). As soon as this method is called, any buffered data will be delivered immediately. A pending end-of-file notication may also be delivered if one was queued while reading was paused.

Server channel write methods

can_write_eof()¶

Return whether the channel supports write_eof()

This method always returns True.

get_write_buffer_size()¶

Return the current size of the channel’s output buffer

This method returns how many bytes are currently in the channel’s output buffer waiting to be written.

set_write_buffer_limits(high=None, low=None)¶

Set the high- and low-water limits for write flow control

This method sets the limits used when deciding when to call the pause_writing() and resume_writing() methods on SSH sessions. Writing will be paused when the write buffer size exceeds the high-water mark, and resumed when the write buffer size equals or drops below the low-water mark.

write(data, datatype=None)¶

Write data on the channel

This method can be called to send data on the channel. If an encoding was specified when the channel was created, the data should be provided as a string and will be converted using that encoding. Otherwise, the data should be provided as bytes.

An extended data type can optionally be provided. For instance, this is used from a SSHServerSession to write data to stderr.

Parameters:	data (str or bytes) – The data to send on the channel datatype (int) – (optional) The extended data type of the data, from extended data types
Raises:	`OSError` if the channel isn’t open for sending or the extended data type is not valid for this type of channel

writelines(list_of_data, datatype=None)¶

Write a list of data bytes on the channel

This method can be called to write a list (or any iterable) of data bytes to the channel. It is functionality equivalent to calling write() on each element in the list.

Parameters:	list_of_data (iterable of str or bytes objects) – The data to send on the channel datatype (int) – (optional) The extended data type of the data, from extended data types
Raises:	`OSError` if the channel isn’t open for sending or the extended data type is not valid for this type of channel

write_stderr(data)[source]¶

Write output to stderr

This method can be called to send output to the client which is intended to be displayed on stderr. If an encoding was specified when the channel was created, the data should be provided as a string and will be converted using that encoding. Otherwise, the data should be provided as bytes.

Parameters:	data (str or bytes) – The data to send to stderr
Raises:	`OSError` if the channel isn’t open for sending

writelines_stderr(list_of_data)[source]¶

Write a list of data bytes to stderr

This method can be called to write a list (or any iterable) of data bytes to the channel. It is functionality equivalent to calling write_stderr() on each element in the list.

write_eof()¶

Write EOF on the channel

This method sends an end-of-file indication on the channel, after which no more data can be sent. The channel remains open, though, and data may still be sent in the other direction.

Raises:	`OSError` if the channel isn’t open for sending

Other server channel methods

set_xon_xoff(client_can_do)[source]¶

Set whether the client should enable XON/XOFF flow control

This method can be called to tell the client whether or not to enable XON/XOFF flow control, indicating that it should intercept Control-S and Control-Q coming from its local terminal to pause and resume output, respectively. Applications should set client_can_do to True to enable this functionality or to False to tell the client to forward Control-S and Control-Q through as normal input.

Parameters:	client_can_do (bool) – Whether or not the client should enable XON/XOFF flow control

exit(status)[source]¶

Send exit status and close the channel

This method can be called to report an exit status for the process back to the client and close the channel. A zero exit status is generally returned when the operation was successful. After reporting the status, the channel is closed.

Parameters:	status (int) – The exit status to report to the client
Raises:	`OSError` if the channel isn’t open

exit_with_signal(signal, core_dumped=False, msg='', lang='en-US')[source]¶

Send exit signal and close the channel

This method can be called to report that the process terminated abnormslly with a signal. A more detailed error message may also provided, along with an indication of whether or not the process dumped core. After reporting the signal, the channel is closed.

Parameters:	signal (str) – The signal which caused the process to exit core_dumped (bool) – (optional) Whether or not the process dumped core msg (str) – (optional) Details about what error occurred lang (str) – (optional) The language the error message is in
Raises:	`OSError` if the channel isn’t open

General channel close methods
`abort`()¶ Forcibly close the channel This method can be called to forcibly close the channel, after which no more data can be sent or received. Any unsent buffered data and any incoming data in flight will be discarded.
`close`()¶ Cleanly close the channel This method can be called to cleanly close the channel, after which no more data can be sent or received. Any unsent buffered data will be flushed asynchronously before the channel is closed.
`wait_closed`()¶ Wait for this channel to close This method is a coroutine which can be called to block until this channel has finished closing.

SSHTCPChannel¶

class asyncssh.SSHTCPChannel[source]¶

SSH TCP channel

General channel methods

get_extra_info(name, default=None)¶

Get additional information about the channel

This method returns extra information about the channel once it is established. Supported values include 'connection' to return the SSH connection this channel is running over plus all of the values supported on that connection.

For TCP channels, the values 'local_peername' and 'remote_peername' are added to return the local and remote host and port information for the tunneled TCP connection.

For UNIX channels, the values 'local_peername' and 'remote_peername' are added to return the local and remote path information for the tunneled UNIX domain socket connection. Since UNIX domain sockets provide no “source” address, only one of these will be filled in.

See get_extra_info() on SSHClientConnection for more information.

General channel read methods

pause_reading()¶

Pause delivery of incoming data

This method is used to temporarily suspend delivery of incoming channel data. After this call, incoming data will no longer be delivered until resume_reading() is called. Data will be buffered locally up to the configured SSH channel window size, but window updates will no longer be sent, eventually causing back pressure on the remote system.

Note

Channel close notifications are not suspended by this call. If the remote system closes the channel while delivery is suspended, the channel will be closed even though some buffered data may not have been delivered.

resume_reading()¶

Resume delivery of incoming data

This method can be called to resume delivery of incoming data which was suspended by a call to pause_reading(). As soon as this method is called, any buffered data will be delivered immediately. A pending end-of-file notication may also be delivered if one was queued while reading was paused.

General channel write methods

can_write_eof()¶

Return whether the channel supports write_eof()

This method always returns True.

get_write_buffer_size()¶

Return the current size of the channel’s output buffer

This method returns how many bytes are currently in the channel’s output buffer waiting to be written.

set_write_buffer_limits(high=None, low=None)¶

Set the high- and low-water limits for write flow control

This method sets the limits used when deciding when to call the pause_writing() and resume_writing() methods on SSH sessions. Writing will be paused when the write buffer size exceeds the high-water mark, and resumed when the write buffer size equals or drops below the low-water mark.

write(data, datatype=None)¶

Write data on the channel

This method can be called to send data on the channel. If an encoding was specified when the channel was created, the data should be provided as a string and will be converted using that encoding. Otherwise, the data should be provided as bytes.

An extended data type can optionally be provided. For instance, this is used from a SSHServerSession to write data to stderr.

Parameters:	data (str or bytes) – The data to send on the channel datatype (int) – (optional) The extended data type of the data, from extended data types
Raises:	`OSError` if the channel isn’t open for sending or the extended data type is not valid for this type of channel

writelines(list_of_data, datatype=None)¶

Write a list of data bytes on the channel

This method can be called to write a list (or any iterable) of data bytes to the channel. It is functionality equivalent to calling write() on each element in the list.

Parameters:	list_of_data (iterable of str or bytes objects) – The data to send on the channel datatype (int) – (optional) The extended data type of the data, from extended data types
Raises:	`OSError` if the channel isn’t open for sending or the extended data type is not valid for this type of channel

write_eof()¶

Write EOF on the channel

This method sends an end-of-file indication on the channel, after which no more data can be sent. The channel remains open, though, and data may still be sent in the other direction.

Raises:	`OSError` if the channel isn’t open for sending

General channel close methods
`abort`()¶ Forcibly close the channel This method can be called to forcibly close the channel, after which no more data can be sent or received. Any unsent buffered data and any incoming data in flight will be discarded.
`close`()¶ Cleanly close the channel This method can be called to cleanly close the channel, after which no more data can be sent or received. Any unsent buffered data will be flushed asynchronously before the channel is closed.
`wait_closed`()¶ Wait for this channel to close This method is a coroutine which can be called to block until this channel has finished closing.

SSHUNIXChannel¶

class asyncssh.SSHUNIXChannel[source]¶

SSH UNIX channel

General channel methods

get_extra_info(name, default=None)¶

Get additional information about the channel

This method returns extra information about the channel once it is established. Supported values include 'connection' to return the SSH connection this channel is running over plus all of the values supported on that connection.

For TCP channels, the values 'local_peername' and 'remote_peername' are added to return the local and remote host and port information for the tunneled TCP connection.

For UNIX channels, the values 'local_peername' and 'remote_peername' are added to return the local and remote path information for the tunneled UNIX domain socket connection. Since UNIX domain sockets provide no “source” address, only one of these will be filled in.

See get_extra_info() on SSHClientConnection for more information.

General channel read methods

pause_reading()¶

Pause delivery of incoming data

This method is used to temporarily suspend delivery of incoming channel data. After this call, incoming data will no longer be delivered until resume_reading() is called. Data will be buffered locally up to the configured SSH channel window size, but window updates will no longer be sent, eventually causing back pressure on the remote system.

Note

Channel close notifications are not suspended by this call. If the remote system closes the channel while delivery is suspended, the channel will be closed even though some buffered data may not have been delivered.

resume_reading()¶

Resume delivery of incoming data

This method can be called to resume delivery of incoming data which was suspended by a call to pause_reading(). As soon as this method is called, any buffered data will be delivered immediately. A pending end-of-file notication may also be delivered if one was queued while reading was paused.

General channel write methods

can_write_eof()¶

Return whether the channel supports write_eof()

This method always returns True.

get_write_buffer_size()¶

Return the current size of the channel’s output buffer

This method returns how many bytes are currently in the channel’s output buffer waiting to be written.

set_write_buffer_limits(high=None, low=None)¶

Set the high- and low-water limits for write flow control

This method sets the limits used when deciding when to call the pause_writing() and resume_writing() methods on SSH sessions. Writing will be paused when the write buffer size exceeds the high-water mark, and resumed when the write buffer size equals or drops below the low-water mark.

write(data, datatype=None)¶

Write data on the channel

This method can be called to send data on the channel. If an encoding was specified when the channel was created, the data should be provided as a string and will be converted using that encoding. Otherwise, the data should be provided as bytes.

An extended data type can optionally be provided. For instance, this is used from a SSHServerSession to write data to stderr.

Parameters:	data (str or bytes) – The data to send on the channel datatype (int) – (optional) The extended data type of the data, from extended data types
Raises:	`OSError` if the channel isn’t open for sending or the extended data type is not valid for this type of channel

writelines(list_of_data, datatype=None)¶

Write a list of data bytes on the channel

This method can be called to write a list (or any iterable) of data bytes to the channel. It is functionality equivalent to calling write() on each element in the list.

Parameters:	list_of_data (iterable of str or bytes objects) – The data to send on the channel datatype (int) – (optional) The extended data type of the data, from extended data types
Raises:	`OSError` if the channel isn’t open for sending or the extended data type is not valid for this type of channel

write_eof()¶

Write EOF on the channel

This method sends an end-of-file indication on the channel, after which no more data can be sent. The channel remains open, though, and data may still be sent in the other direction.

Raises:	`OSError` if the channel isn’t open for sending

General channel close methods
`abort`()¶ Forcibly close the channel This method can be called to forcibly close the channel, after which no more data can be sent or received. Any unsent buffered data and any incoming data in flight will be discarded.
`close`()¶ Cleanly close the channel This method can be called to cleanly close the channel, after which no more data can be sent or received. Any unsent buffered data will be flushed asynchronously before the channel is closed.
`wait_closed`()¶ Wait for this channel to close This method is a coroutine which can be called to block until this channel has finished closing.

Listener Classes¶

SSHListener¶

class asyncssh.SSHListener[source]¶

SSH listener for inbound connections

get_port()[source]¶

Return the port number being listened on

This method returns the port number that the remote listener was bound to. When the requested remote listening port is 0 to indicate a dynamic port, this method can be called to determine what listening port was selected. This function only applies to TCP listeners.

Returns:	The port number being listened on

close()[source]¶

Stop listening for new connections

This method can be called to stop listening for connections. Existing connections will remain open.

wait_closed()[source]¶

Wait for the listener to close

This method is a coroutine which waits for the associated listeners to be closed.

Stream Classes¶

SSHReader¶

class asyncssh.SSHReader[source]¶

SSH read stream handler

`channel`¶ The SSH channel associated with this stream
`get_extra_info`(name, default=None)[source]¶ Return additional information about this stream This method returns extra information about the channel associated with this stream. See `get_extra_info()` on `SSHClientChannel` for additional information.
`at_eof`()[source]¶ Return whether the stream is at EOF This method returns `True` when EOF has been received and all data in the stream has been read.
`read`(n=-1)[source]¶ Read data from the stream This method is a coroutine which reads up to `n` bytes or characters from the stream. If `n` is not provided or set to `-1`, it reads until EOF or until a signal is received on the stream. If EOF was received and the receive buffer is empty, an empty bytes or str object is returned. Note Unlike traditional `asyncio` stream readers, the data will be delivered as either bytes or a str depending on whether an encoding was specified when the underlying channel was opened.
`readline`()[source]¶ Read one line from the stream This method is a coroutine which reads one line, ending in `'\n'`. If EOF was received before `'\n'` was found, the partial line is returned. If EOF was received and the receive buffer is empty, an empty bytes or str object is returned.
`readexactly`(n)[source]¶ Read an exact amount of data from the stream This method is a coroutine which reads exactly n bytes or characters from the stream. If EOF is received before `n` bytes are read, an `IncompleteReadError` is raised and its `partial` attribute contains the partially read data.

SSHWriter¶

class asyncssh.SSHWriter[source]¶

SSH write stream handler

`channel`¶ The SSH channel associated with this stream
`get_extra_info`(name, default=None)[source]¶ Return additional information about this stream This method returns extra information about the channel associated with this stream. See `get_extra_info()` on `SSHClientChannel` for additional information.
`can_write_eof`()[source]¶ Return whether the stream supports `write_eof()`
`close`()[source]¶ Close the channel Note After this is called, no data can be read or written from any of the streams associated with this channel.
`drain`()[source]¶ Wait until the write buffer on the channel is flushed This method is a coroutine which blocks the caller if the stream is currently paused for writing, returning when enough data has been sent on the channel to allow writing to resume. This can be used to avoid buffering an excessive amount of data in the channel’s send buffer.
`write`(data)[source]¶ Write data to the stream This method writes bytes or characters to the stream. Note Unlike traditional `asyncio` stream writers, the data must be supplied as either bytes or a str depending on whether an encoding was specified when the underlying channel was opened.
`writelines`(list_of_data)[source]¶ Write a collection of data to the stream
`write_eof`()[source]¶ Write EOF on the channel This method sends an end-of-file indication on the channel, after which no more data can be written. Note On an `SSHServerChannel` where multiple output streams are created, writing EOF on one stream signals EOF for all of them, since it applies to the channel as a whole.

SFTP Support¶

SFTPClient¶

class asyncssh.SFTPClient[source]¶

SFTP client

This class represents the client side of an SFTP session. It is started by calling the start_sftp_client() method on the SSHClientConnection class.

File transfer methods

get(remotepaths, localpath=None, *, preserve=False, recurse=False, follow_symlinks=False, error_handler=None)[source]¶

Download remote files

This method downloads one or more files or directories from the remote system. Either a single remote path or a sequence of remote paths to download can be provided.

When downloading a single file or directory, the local path can be either the full path to download data into or the path to an existing directory where the data should be placed. In the latter case, the base file name from the remote path will be used as the local name.

When downloading multiple files, the local path must refer to an existing directory.

If no local path is provided, the file is downloaded into the current local working directory.

If preserve is True, the access and modification times and permissions of the original file are set on the downloaded file.

If recurse is True and the remote path points at a directory, the entire subtree under that directory is downloaded.

If follow_symlinks is set to True, symbolic links found on the remote system will have the contents of their target downloaded rather than creating a local symbolic link. When using this option during a recursive download, one needs to watch out for links that result in loops.

If error_handler is specified and an error occurs during the download, this handler will be called with the exception instead of it being raised. This is intended to primarily be used when multiple remote paths are provided or when recurse is set to True, to allow error information to be collected without aborting the download of the remaining files. The error handler can raise an exception if it wants the download to completely stop. Otherwise, after an error, the download will continue starting with the next file.

Parameters:

remotepaths (str or bytes, or a sequence of these) – The paths of the remote files or directories to download
localpath (str) – (optional) The path of the local file or directory to download into
preserve (bool) – (optional) Whether or not to preserve the original file attributes
recurse (bool) – (optional) Whether or not to recursively copy directories
follow_symlinks (bool) – (optional) Whether or not to follow symbolic links
error_handler (callable) – (optional) The function to call when an error occurs

Raises:

OSError if a local file I/O error occurs

SFTPError if the server returns an error

put(localpaths, remotepath=None, *, preserve=False, recurse=False, follow_symlinks=False, error_handler=None)[source]¶

Upload local files

This method uploads one or more files or directories to the remote system. Either a single local path or a sequence of local paths to upload can be provided.

When uploading a single file or directory, the remote path can be either the full path to upload data into or the path to an existing directory where the data should be placed. In the latter case, the base file name from the local path will be used as the remote name.

When uploading multiple files, the remote path must refer to an existing directory.

If no remote path is provided, the file is uploaded into the current remote working directory.

If preserve is True, the access and modification times and permissions of the original file are set on the uploaded file.

If recurse is True and the local path points at a directory, the entire subtree under that directory is uploaded.

If follow_symlinks is set to True, symbolic links found on the local system will have the contents of their target uploaded rather than creating a remote symbolic link. When using this option during a recursive upload, one needs to watch out for links that result in loops.

If error_handler is specified and an error occurs during the upload, this handler will be called with the exception instead of it being raised. This is intended to primarily be used when multiple local paths are provided or when recurse is set to True, to allow error information to be collected without aborting the upload of the remaining files. The error handler can raise an exception if it wants the upload to completely stop. Otherwise, after an error, the upload will continue starting with the next file.

Parameters:

localpaths (str or bytes, or a sequence of these) – The paths of the local files or directories to upload
remotepath (str or bytes) – (optional) The path of the remote file or directory to upload into
preserve (bool) – (optional) Whether or not to preserve the original file attributes
recurse (bool) – (optional) Whether or not to recursively copy directories
follow_symlinks (bool) – (optional) Whether or not to follow symbolic links
error_handler (callable) – (optional) The function to call when an error occurs

Raises:

OSError if a local file I/O error occurs

SFTPError if the server returns an error

copy(srcpaths, dstpath=None, *, preserve=False, recurse=False, follow_symlinks=False, error_handler=None)[source]¶

Copy remote files to a new location

This method copies one or more files or directories on the remote system to a new location. Either a single source path or a sequence of source paths to copy can be provided.

When copying a single file or directory, the destination path can be either the full path to copy data into or the path to an existing directory where the data should be placed. In the latter case, the base file name from the source path will be used as the destination name.

When copying multiple files, the destination path must refer to an existing remote directory.

If no destination path is provided, the file is copied into the current remote working directory.

If preserve is True, the access and modification times and permissions of the original file are set on the copied file.

If recurse is True and the source path points at a directory, the entire subtree under that directory is copied.

If follow_symlinks is set to True, symbolic links found in the source will have the contents of their target copied rather than creating a copy of the symbolic link. When using this option during a recursive copy, one needs to watch out for links that result in loops.

If error_handler is specified and an error occurs during the copy, this handler will be called with the exception instead of it being raised. This is intended to primarily be used when multiple source paths are provided or when recurse is set to True, to allow error information to be collected without aborting the copy of the remaining files. The error handler can raise an exception if it wants the copy to completely stop. Otherwise, after an error, the copy will continue starting with the next file.

Parameters:

srcpaths (str or bytes, or a sequence of these) – The paths of the remote files or directories to copy
dstpath (str or bytes) – (optional) The path of the remote file or directory to copy into
preserve (bool) – (optional) Whether or not to preserve the original file attributes
recurse (bool) – (optional) Whether or not to recursively copy directories
follow_symlinks (bool) – (optional) Whether or not to follow symbolic links
error_handler (callable) – (optional) The function to call when an error occurs

Raises:

OSError if a local file I/O error occurs

SFTPError if the server returns an error

mget(remotepaths, localpath=None, *, preserve=False, recurse=False, follow_symlinks=False, error_handler=None)[source]¶

Download remote files with glob pattern match

This method downloads files and directories from the remote system matching one or more glob patterns.

The arguments to this method are identical to the get() method, except that the remote paths specified can contain ‘*’ and ‘?’ wildcard characters.

mput(localpaths, remotepath=None, *, preserve=False, recurse=False, follow_symlinks=False, error_handler=None)[source]¶

Upload local files with glob pattern match

This method uploads files and directories to the remote system matching one or more glob patterns.

The arguments to this method are identical to the put() method, except that the local paths specified can contain ‘*’ and ‘?’ wildcard characters.

mcopy(srcpaths, dstpath=None, *, preserve=False, recurse=False, follow_symlinks=False, error_handler=None)[source]¶

Download remote files with glob pattern match

This method copies files and directories on the remote system matching one or more glob patterns.

The arguments to this method are identical to the copy() method, except that the source paths specified can contain ‘*’ and ‘?’ wildcard characters.

File access methods

open(path, mode='r', attrs=SFTPAttrs(), encoding='utf-8', errors='strict')[source]¶

Open a remote file

This method opens a remote file and returns an SFTPFile object which can be used to read and write data and get and set file attributes.

The path can be either a str or bytes value. If it is a str, it will be encoded using the file encoding specified when the SFTPClient was started.

The following open mode flags are supported:

Mode Description

FXF_READ Open the file for reading.

FXF_WRITE Open the file for writing. If both this and FXF_READ are set, open the file for both reading and writing.

FXF_APPEND Force writes to append data to the end of the file regardless of seek position.

FXF_CREAT Create the file if it doesn’t exist. Without this, attempts to open a non-existent file will fail.

FXF_TRUNC Truncate the file to zero length if it already exists.

FXF_EXCL Return an error when trying to open a file which already exists.

By default, file data is read and written as strings in UTF-8 format with strict error checking, but this can be changed using the encoding and errors parameters. To read and write data as bytes in binary format, an encoding value of None can be used.

Instead of these flags, a Python open mode string can also be provided. Python open modes map to the above flags as follows:

Mode Flags

r FXF_READ

w FXF_WRITE | FXF_CREAT | FXF_TRUNC

a FXF_WRITE | FXF_CREAT | FXF_APPEND

x FXF_WRITE | FXF_CREAT | FXF_EXCL

r+ FXF_READ | FXF_WRITE

w+ FXF_READ | FXF_WRITE | FXF_CREAT | FXF_TRUNC

a+ FXF_READ | FXF_WRITE | FXF_CREAT | FXF_APPEND

x+ FXF_READ | FXF_WRITE | FXF_CREAT | FXF_EXCL

Including a ‘b’ in the mode causes the encoding to be set to None, forcing all data to be read and written as bytes in binary format.

The attrs argument is used to set initial attributes of the file if it needs to be created. Otherwise, this argument is ignored.

Parameters:	path (str or bytes) – The name of the remote file to open pflags_or_mode (int or str) – (optional) The access mode to use for the remote file (see above) attrs (`SFTPAttrs`) – (optional) File attributes to use if the file needs to be created encoding (str) – (optional) The Unicode encoding to use for data read and written to the remote file errors (str) – (optional) The error-handling mode if an invalid Unicode byte sequence is detected, defaulting to ‘strict’ which raises an exception
Returns:	An `SFTPFile` to use to access the file
Raises:	`ValueError` if the mode is not valid `SFTPError` if the server returns an error

truncate(path, size)[source]¶

Truncate a remote file to the specified size

This method truncates a remote file to the specified size. If the path provided is a symbolic link, the target of the link will be truncated.

Parameters:	path (str or bytes) – The path of the remote file to be truncated size (int) – The desired size of the file, in bytes
Raises:	`SFTPError` if the server returns an error

rename(oldpath, newpath)[source]¶

Rename a remote file, directory, or link

This method renames a remote file, directory, or link.

Note

This requests the standard SFTP version of rename which will not overwrite the new path if it already exists. To request POSIX behavior where the new path is removed before the rename, use posix_rename().

Parameters:	oldpath (str or bytes) – The path of the remote file, directory, or link to rename newpath (str or bytes) – The new name for this file, directory, or link
Raises:	`SFTPError` if the server returns an error

posix_rename(oldpath, newpath)[source]¶

Rename a remote file, directory, or link with POSIX semantics

This method renames a remote file, directory, or link, removing the prior instance of new path if it previously existed.

This method may not be supported by all SFTP servers.

Parameters:	oldpath (str or bytes) – The path of the remote file, directory, or link to rename newpath (str or bytes) – The new name for this file, directory, or link
Raises:	`SFTPError` if the server doesn’t support this extension or returns an error

remove(path)[source]¶

Remove a remote file

This method removes a remote file or symbolic link.

Parameters:	path (str or bytes) – The path of the remote file or link to remove
Raises:	`SFTPError` if the server returns an error

unlink(path)[source]¶: Remove a remote file (see remove())

readlink(path)[source]¶

Return the target of a remote symbolic link

This method returns the target of a symbolic link.

Parameters:	path (str or bytes) – The path of the remote symbolic link to follow
Returns:	The target path of the link as a str or bytes
Raises:	`SFTPError` if the server returns an error

symlink(oldpath, newpath)[source]¶

Create a remote symbolic link

This method creates a symbolic link. The argument order here matches the standard Python os.symlink() call. The argument order sent on the wire is automatically adapted depending on the version information sent by the server, as a number of servers (OpenSSH in particular) did not follow the SFTP standard when implementing this call.

Parameters:	oldpath (str or bytes) – The path the link should point to newpath (str or bytes) – The path of where to create the remote symbolic link
Raises:	`SFTPError` if the server returns an error

link(oldpath, newpath)[source]¶

Create a remote hard link

This method creates a hard link to the remote file specified by oldpath at the location specified by newpath.

This method may not be supported by all SFTP servers.

Parameters:	oldpath (str or bytes) – The path of the remote file the hard link should point to newpath (str or bytes) – The path of where to create the remote hard link
Raises:	`SFTPError` if the server doesn’t support this extension or returns an error

realpath(path)[source]¶

Return the canonical version of a remote path

This method returns a canonical version of the requested path.

Parameters:	path (str or bytes) – (optional) The path of the remote directory to canonicalize
Returns:	The canonical path as a str or bytes, matching the type used to pass in the path
Raises:	`SFTPError` if the server returns an error

File attribute access methods

stat(path)[source]¶

Get attributes of a remote file or directory, following symlinks

This method queries the attributes of a remote file or directory. If the path provided is a symbolic link, the returned attributes will correspond to the target of the link.

Parameters:	path (str or bytes) – The path of the remote file or directory to get attributes for
Returns:	An `SFTPAttrs` containing the file attributes
Raises:	`SFTPError` if the server returns an error

lstat(path)[source]¶

Get attributes of a remote file, directory, or symlink

This method queries the attributes of a remote file, directory, or symlink. Unlike stat(), this method returns the attributes of a symlink itself rather than the target of that link.

Parameters:	path (str or bytes) – The path of the remote file, directory, or link to get attributes for
Returns:	An `SFTPAttrs` containing the file attributes
Raises:	`SFTPError` if the server returns an error

setstat(path, attrs)[source]¶

Set attributes of a remote file or directory

This method sets attributes of a remote file or directory. If the path provided is a symbolic link, the attributes will be set on the target of the link. A subset of the fields in attrs can be initialized and only those attributes will be changed.

Parameters:	path (str or bytes) – The path of the remote file or directory to set attributes for attrs (`SFTPAttrs`) – File attributes to set
Raises:	`SFTPError` if the server returns an error

statvfs(path)[source]¶

Get attributes of a remote file system

This method queries the attributes of the file system containing the specified path.

Parameters:	path (str or bytes) – The path of the remote file system to get attributes for
Returns:	An `SFTPVFSAttrs` containing the file system attributes
Raises:	`SFTPError` if the server doesn’t support this extension or returns an error

chown(path, uid, gid)[source]¶

Change the owner user and group id of a remote file or directory

This method changes the user and group id of a remote file or directory. If the path provided is a symbolic link, the target of the link will be changed.

Parameters:	path (str or bytes) – The path of the remote file to change uid (int) – The new user id to assign to the file gid (int) – The new group id to assign to the file
Raises:	`SFTPError` if the server returns an error

chmod(path, mode)[source]¶

Change the file permissions of a remote file or directory

This method changes the permissions of a remote file or directory. If the path provided is a symbolic link, the target of the link will be changed.

Parameters:	path (str or bytes) – The path of the remote file to change mode (int) – The new file permissions, expressed as an int
Raises:	`SFTPError` if the server returns an error

utime(path, times=None)[source]¶

Change the access and modify times of a remote file or directory

This method changes the access and modify times of a remote file or directory. If times is not provided, the times will be changed to the current time. If the path provided is a symbolic link, the target of the link will be changed.

Parameters:	path (str or bytes) – The path of the remote file to change times (tuple of two int or float values) – (optional) The new access and modify times, as seconds relative to the UNIX epoch
Raises:	`SFTPError` if the server returns an error

exists(path)[source]¶

Return if the remote path exists and isn’t a broken symbolic link

Parameters:	path (str or bytes) – The remote path to check
Raises:	`SFTPError` if the server returns an error

lexists(path)[source]¶

Return if the remote path exists, without following symbolic links

Parameters:	path (str or bytes) – The remote path to check
Raises:	`SFTPError` if the server returns an error

getatime(path)[source]¶

Return the last access time of a remote file or directory

Parameters:	path (str or bytes) – The remote path to check
Raises:	`SFTPError` if the server returns an error

getmtime(path)[source]¶

Return the last modification time of a remote file or directory

Parameters:	path (str or bytes) – The remote path to check
Raises:	`SFTPError` if the server returns an error

getsize(path)[source]¶

Return the size of a remote file or directory

Parameters:	path (str or bytes) – The remote path to check
Raises:	`SFTPError` if the server returns an error

isdir(path)[source]¶

Return if the remote path refers to a directory

Parameters:	path (str or bytes) – The remote path to check
Raises:	`SFTPError` if the server returns an error

isfile(path)[source]¶

Return if the remote path refers to a regular file

Parameters:	path (str or bytes) – The remote path to check
Raises:	`SFTPError` if the server returns an error

islink(path)[source]¶

Return if the remote path refers to a symbolic link

Parameters:	path (str or bytes) – The remote path to check
Raises:	`SFTPError` if the server returns an error

Directory access methods

chdir(path)[source]¶

Change the current remote working directory

Parameters:	path (str or bytes) – The path to set as the new remote working directory
Raises:	`SFTPError` if the server returns an error

getcwd()[source]¶

Return the current remote working directory

Returns:	The current remote working directory, decoded using the specified path encoding
Raises:	`SFTPError` if the server returns an error

mkdir(path, attrs=SFTPAttrs())[source]¶

Create a remote directory with the specified attributes

This method creates a new remote directory at the specified path with the requested attributes.

Parameters:	path (str or bytes) – The path of where the new remote directory should be created attrs (`SFTPAttrs`) – (optional) The file attributes to use when creating the directory
Raises:	`SFTPError` if the server returns an error

rmdir(path)[source]¶

Remove a remote directory

This method removes a remote directory. The directory must be empty for the removal to succeed.

Parameters:	path (str or bytes) – The path of the remote directory to remove
Raises:	`SFTPError` if the server returns an error

readdir(path='.')[source]¶

Read the contents of a remote directory

This method reads the contents of a directory, returning the names and attributes of what is contained there. If no path is provided, it defaults to the current remote working directory.

Parameters:	path (str or bytes) – (optional) The path of the remote directory to read
Returns:	A list of `SFTPName` entries, with path names matching the type used to pass in the path
Raises:	`SFTPError` if the server returns an error

listdir(path='.')[source]¶

Read the names of the files in a remote directory

This method reads the names of files and subdirectories in a remote directory. If no path is provided, it defaults to the current remote working directory.

Parameters:	path (str or bytes) – (optional) The path of the remote directory to read
Returns:	A list of file/subdirectory names, matching the type used to pass in the path
Raises:	`SFTPError` if the server returns an error

glob(patterns, error_handler=None)[source]¶

Match remote files against glob patterns

This method matches remote files against one or more glob patterns. Either a single pattern or a sequence of patterns can be provided to match against.

If error_handler is specified and an error occurs during the match, this handler will be called with the exception instead of it being raised. This is intended to primarily be used when multiple patterns are provided to allow error information to be collected without aborting the match against the remaining patterns. The error handler can raise an exception if it wants to completely abort the match. Otherwise, after an error, the match will continue starting with the next pattern.

An error will be raised if any of the patterns completely fail to match, and this can either stop the match against the remaining patterns or be handled by the error_handler just like other errors.

Parameters:	patterns (str or bytes, or a sequence of these) – Glob patterns to try and match remote files against error_handler (callable) – (optional) The function to call when an error occurs
Raises:	`SFTPError` if the server returns an error or no match is found

Cleanup methods
`exit`()[source]¶ Exit the SFTP client session This method exits the SFTP client session, closing the corresponding channel opened on the server.
`wait_closed`()[source]¶ Wait for this SFTP client session to close

SFTPServer¶

class asyncssh.SFTPServer(conn, chroot=None)[source]¶

SFTP server

Applications should subclass this when implementing an SFTP server. The methods listed below should be implemented to provide the desired application behavior.

Note

Any method can optionally be defined as a coroutine if that method needs to perform blocking opertions to determine its result.

The conn object provided here refers to the SSHServerConnection instance this SFTP server is associated with. It can be queried to determine which user the client authenticated as or to request key and certificate options or permissions which should be applied to this session.

If the chroot argument is specified when this object is created, the default map_path() and reverse_map_path() methods will enforce a virtual root directory starting in that location, limiting access to only files within that directory tree. This will also affect path names returned by the realpath() and readlink() methods.

Path remapping and display methods

format_longname(name)[source]¶

Format the long name associated with an SFTP name

This method fills in the longname field of a SFTPName object. By default, it generates something similar to UNIX “ls -l” output. The filename and attrs fields of the SFTPName should already be filled in before this method is called.

Parameters:	name (`SFTPName`) – The `SFTPName` instance to format the long name for

map_path(path)[source]¶

Map the path requested by the client to a local path

This method can be overridden to provide a custom mapping from path names requested by the client to paths in the local filesystem. By default, it will enforce a virtual “chroot” if one was specified when this server was created. Otherwise, path names are left unchanged, with relative paths being interpreted based on the working directory of the currently running process.

Parameters:	path (bytes) – The path name to map
Returns:	bytes containing he local path name to operate on

reverse_map_path(path)[source]¶

Reverse map a local path into the path reported to the client

This method can be overridden to provide a custom reverse mapping for the mapping provided by map_path(). By default, it hides the portion of the local path associated with the virtual “chroot” if one was specified.

Parameters:	path (bytes) – The local path name to reverse map
Returns:	bytes containing the path name to report to the client

File access methods

open(path, pflags, attrs)[source]¶

Open a file to serve to a remote client

This method returns a file object which can be used to read and write data and get and set file attributes.

The possible open mode flags and their meanings are:

Mode Description

FXF_READ Open the file for reading. If neither FXF_READ nor FXF_WRITE are set, this is the default.

FXF_WRITE Open the file for writing. If both this and FXF_READ are set, open the file for both reading and writing.

FXF_APPEND Force writes to append data to the end of the file regardless of seek position.

FXF_CREAT Create the file if it doesn’t exist. Without this, attempts to open a non-existent file will fail.

FXF_TRUNC Truncate the file to zero length if it already exists.

FXF_EXCL Return an error when trying to open a file which already exists.

The attrs argument is used to set initial attributes of the file if it needs to be created. Otherwise, this argument is ignored.

Parameters:	path (bytes) – The name of the file to open pflags (int) – The access mode to use for the file (see above) attrs (`SFTPAttrs`) – File attributes to use if the file needs to be created
Returns:	A file object to use to access the file
Raises:	`SFTPError` to return an error to the client

close(file_obj)[source]¶

Close an open file or directory

Parameters:	file_obj (file) – The file or directory object to close
Raises:	`SFTPError` to return an error to the client

read(file_obj, offset, size)[source]¶

Read data from an open file

Parameters:	file_obj (file) – The file to read from offset (int) – The offset from the beginning of the file to begin reading size (int) – The number of bytes to read
Returns:	bytes read from the file
Raises:	`SFTPError` to return an error to the client

write(file_obj, offset, data)[source]¶

Write data to an open file

Parameters:	file_obj (file) – The file to write to offset (int) – The offset from the beginning of the file to begin writing data (bytes) – The data to write to the file
Returns:	number of bytes written
Raises:	`SFTPError` to return an error to the client

rename(oldpath, newpath)[source]¶

Rename a file, directory, or link

This method renames a file, directory, or link.

Note

This is a request for the standard SFTP version of rename which will not overwrite the new path if it already exists. The posix_rename() method will be called if the client requests the POSIX behavior where an existing instance of the new path is removed before the rename.

Parameters:	oldpath (bytes) – The path of the file, directory, or link to rename newpath (bytes) – The new name for this file, directory, or link
Raises:	`SFTPError` to return an error to the client

posix_rename(oldpath, newpath)[source]¶

Rename a file, directory, or link with POSIX semantics

This method renames a file, directory, or link, removing the prior instance of new path if it previously existed.

Parameters:	oldpath (bytes) – The path of the file, directory, or link to rename newpath (bytes) – The new name for this file, directory, or link
Raises:	`SFTPError` to return an error to the client

remove(path)[source]¶

Remove a file or symbolic link

Parameters:	path (bytes) – The path of the file or link to remove
Raises:	`SFTPError` to return an error to the client

readlink(path)[source]¶

Return the target of a symbolic link

Parameters:	path (bytes) – The path of the symbolic link to follow
Returns:	bytes containing the target path of the link
Raises:	`SFTPError` to return an error to the client

symlink(oldpath, newpath)[source]¶

Create a symbolic link

Parameters:	oldpath (bytes) – The path the link should point to newpath (bytes) – The path of where to create the symbolic link
Raises:	`SFTPError` to return an error to the client

link(oldpath, newpath)[source]¶

Create a hard link

Parameters:	oldpath (bytes) – The path of the file the hard link should point to newpath (bytes) – The path of where to create the hard link
Raises:	`SFTPError` to return an error to the client

realpath(path)[source]¶

Return the canonical version of a path

Parameters:	path (bytes) – The path of the directory to canonicalize
Returns:	bytes containing the canonical path
Raises:	`SFTPError` to return an error to the client

File attribute access methods

stat(path)[source]¶

Get attributes of a file or directory, following symlinks

This method queries the attributes of a file or directory. If the path provided is a symbolic link, the returned attributes should correspond to the target of the link.

Parameters:	path (bytes) – The path of the remote file or directory to get attributes for
Returns:	An `SFTPAttrs` or an os.stat_result containing the file attributes
Raises:	`SFTPError` to return an error to the client

lstat(path)[source]¶

Get attributes of a file, directory, or symlink

This method queries the attributes of a file, directory, or symlink. Unlike stat(), this method should return the attributes of a symlink itself rather than the target of that link.

Parameters:	path (bytes) – The path of the file, directory, or link to get attributes for
Returns:	An `SFTPAttrs` or an os.stat_result containing the file attributes
Raises:	`SFTPError` to return an error to the client

fstat(file_obj)[source]¶

Get attributes of an open file

Parameters:	file_obj (file) – The file to get attributes for
Returns:	An `SFTPAttrs` or an os.stat_result containing the file attributes
Raises:	`SFTPError` to return an error to the client

setstat(path, attrs)[source]¶

Set attributes of a file or directory

This method sets attributes of a file or directory. If the path provided is a symbolic link, the attributes should be set on the target of the link. A subset of the fields in attrs can be initialized and only those attributes should be changed.

Parameters:	path (bytes) – The path of the remote file or directory to set attributes for attrs (`SFTPAttrs`) – File attributes to set
Raises:	`SFTPError` to return an error to the client

fsetstat(file_obj, attrs)[source]¶

Set attributes of an open file

Parameters:	attrs (`SFTPAttrs`) – File attributes to set on the file
Raises:	`SFTPError` to return an error to the client

statvfs(path)[source]¶

Get attributes of the file system containing a file

Parameters:	path (bytes) – The path of the file system to get attributes for
Returns:	An `SFTPVFSAttrs` or an os.statvfs_result containing the file system attributes
Raises:	`SFTPError` to return an error to the client

fstatvfs(file_obj)[source]¶

Return attributes of the file system containing an open file

Parameters:	file_obj (file) – The open file to get file system attributes for
Returns:	An `SFTPVFSAttrs` or an os.statvfs_result containing the file system attributes
Raises:	`SFTPError` to return an error to the client

Directory access methods

listdir(path)[source]¶

List the contents of a directory

Parameters:	path (bytes) – The path of the directory to open
Returns:	A list of names of files in the directory
Raises:	`SFTPError` to return an error to the client

mkdir(path, attrs)[source]¶

Create a directory with the specified attributes

Parameters:	path (bytes) – The path of where the new directory should be created attrs (`SFTPAttrs`) – The file attributes to use when creating the directory
Raises:	`SFTPError` to return an error to the client

rmdir(path)[source]¶

Remove a directory

Parameters:	path (bytes) – The path of the directory to remove
Raises:	`SFTPError` to return an error to the client

Cleanup methods
`exit`()[source]¶ Shut down this SFTP server

SFTPFile¶

class asyncssh.SFTPFile[source]¶

SFTP client remote file object

This class represents an open file on a remote SFTP server. It is opened with the open() method on the SFTPClient class and provides methods to read and write data and get and set attributes on the open file.

read(size=-1, offset=None)[source]¶

Read data from the remote file

This method reads and returns up to size bytes of data from the remote file. If size is negative, all data up to the end of the file is returned.

If offset is specified, the read will be performed starting at that offset rather than the current file position. This argument should be provided if you want to issue parallel reads on the same file, since the file position is not predictable in that case.

Data will be returned as a string if an encoding was set when the file was opened. Otherwise, data is returned as bytes.

An empty string or bytes object is returned when at EOF.

Parameters:	size (int) – The number of bytes to read offset (int) – (optional) The offset from the beginning of the file to begin reading
Returns:	data read from the file, as a str or bytes
Raises:	`ValueError` if the file has been closed `UnicodeDecodeError` if the data can’t be decoded using the requested encoding `SFTPError` if the server returns an error

write(data, offset=None)[source]¶

Write data to the remote file

This method writes the specified data at the current position in the remote file.

Parameters:	data (str or bytes) – The data to write to the file offset (int) – (optional) The offset from the beginning of the file to begin writing

If offset is specified, the write will be performed starting at that offset rather than the current file position. This argument should be provided if you want to issue parallel writes on the same file, since the file position is not predictable in that case.

Returns:	number of bytes written
Raises:	`ValueError` if the file has been closed `UnicodeEncodeError` if the data can’t be encoded using the requested encoding `SFTPError` if the server returns an error

seek(offset, from_what=SEEK_SET)[source]¶

Seek to a new position in the remote file

This method changes the position in the remote file. The offset passed in is treated as relative to the beginning of the file if from_what is set to SEEK_SET (the default), relative to the current file position if it is set to SEEK_CUR, or relative to the end of the file if it is set to SEEK_END.

Parameters:	offset (int) – The amount to seek from_what (int) – (optional) The reference point to use (SEEK_SET, SEEK_CUR, or SEEK_END)
Returns:	The new byte offset from the beginning of the file

tell()[source]¶

Return the current position in the remote file

This method returns the current position in the remote file.

Returns:	The current byte offset from the beginning of the file

stat()[source]¶

Return file attributes of the remote file

This method queries file attributes of the currently open file.

Returns:	An `SFTPAttrs` containing the file attributes
Raises:	`SFTPError` if the server returns an error

setstat(attrs)[source]¶

Set attributes of the remote file

This method sets file attributes of the currently open file.

Parameters:	attrs (`SFTPAttrs`) – File attributes to set on the file
Raises:	`SFTPError` if the server returns an error

statvfs()[source]¶

Return file system attributes of the remote file

This method queries attributes of the file system containing the currently open file.

Returns:	An `SFTPVFSAttrs` containing the file system attributes
Raises:	`SFTPError` if the server doesn’t support this extension or returns an error

truncate(size=None)[source]¶

Truncate the remote file to the specified size

This method changes the remote file’s size to the specified value. If a size is not provided, the current file position is used.

Parameters:	size (int) – (optional) The desired size of the file, in bytes
Raises:	`SFTPError` if the server returns an error

chown(uid, gid)[source]¶

Change the owner user and group id of the remote file

This method changes the user and group id of the currently open file.

Parameters:	uid (int) – The new user id to assign to the file gid (int) – The new group id to assign to the file
Raises:	`SFTPError` if the server returns an error

chmod(mode)[source]¶

Change the file permissions of the remote file

This method changes the permissions of the currently open file.

Parameters:	mode (int) – The new file permissions, expressed as an int
Raises:	`SFTPError` if the server returns an error

utime(times=None)[source]¶

Change the access and modify times of the remote file

This method changes the access and modify times of the currently open file. If times is not provided, the times will be changed to the current time.

Parameters:	times (tuple of two int or float values) – (optional) The new access and modify times, as seconds relative to the UNIX epoch
Raises:	`SFTPError` if the server returns an error

fsync()[source]¶: Force the remote file data to be written to disk

close()[source]¶: Close the remote file

SFTPAttrs¶

class asyncssh.SFTPAttrs[source]¶

SFTP file attributes

SFTPAttrs is a simple record class with the following fields:

Field Description Type

size File size in bytes uint64

uid User id of file owner uint32

gid Group id of file owner uint32

permissions Bit mask of POSIX file permissions, uint32

atime Last access time, UNIX epoch seconds uint32

mtime Last modification time, UNIX epoch seconds uint32

In addition to the above, an nlink field is provided which stores the number of links to this file, but it is not encoded in the SFTP protocol. It’s included here only so that it can be used to create the default longname string in SFTPName objects.

Extended attributes can also be added via a field named extended which is a list of string name/value pairs.

When setting attributes using an SFTPAttrs, only fields which have been initialized will be changed on the selected file.

SFTPVFSAttrs¶

class asyncssh.SFTPVFSAttrs[source]¶

SFTP file system attributes

SFTPVFSAttrs is a simple record class with the following fields:

Field Description Type

bsize File system block size (I/O size) uint64

frsize Fundamental block size (allocation size) uint64

blocks Total data blocks (in frsize units) uint64

bfree Free data blocks uint64

bavail Available data blocks (for non-root) uint64

files Total file inodes uint64

ffree Free file inodes uint64

favail Available file inodes (for non-root) uint64

fsid File system id uint64

flags File system flags (read-only, no-setuid) uint64

namemax Maximum filename length uint64

SFTPName¶

class asyncssh.SFTPName[source]¶

SFTP file name and attributes

SFTPName is a simple record class with the following fields:

Field Description Type

filename Filename str or bytes

longname Expanded form of filename & attrs str or bytes

attrs File attributes SFTPAttrs

A list of these is returned by readdir() in SFTPClient when retrieving the contents of a directory.

Public Key Support¶

AsyncSSH has extensive public key and certificate support.

Supported public key types include DSA, RSA, and ECDSA. In addition, ed25519 keys are supported if the libnacl package and libsodium library are installed.

Supported certificate types include version 00 certificates for DSA and RSA keys and version 01 certificates for DSA, RSA, ECDSA, and ed25519 keys. Support is also available for the certificate critical options of force-command and source-address and the extensions permit-pty and permit-port-forwarding.

Several public key and certificate formats are supported including PKCS#1 and PKCS#8 DER and PEM, OpenSSH, and RFC4716 formats.

PEM and PKCS#8 password-based encryption of private keys is supported, as is OpenSSH private key encryption when the bcrypt package is installed.

Specifying private keys¶

Private keys may be passed into AsyncSSH in a variety of forms. The simplest option is to pass the name of a file containing the list of private keys to read in using read_private_key_list(). However, this form can only be used for unencrypted private keys and does not allow any of the private keys to have associated certificates.

An alternate form involves passing in a list of values which can be either a reference to a private key or a tuple containing a reference to a private key and a reference to a matching certificate.

Key references can either be the name of a file to load a key from, a byte string to import it from, or an already loaded SSHKey private key. See the function import_private_key() for the list of supported private key formats.

Certificate references can be the name of a file to load the certificate from, a byte string to import it from, an already loaded SSHCertificate, or None if no certificate should be associated with the key.

When a filename is provided as a value in the list, an attempt is made to load a private key from that file and a certificate from a file constructed by appending ‘-cert.pub’ to the end of the name.

Encrypted private keys can be loaded by making an explicit call to import_private_key() or read_private_key() with the correct passphrase. The resulting SSHKey objects can then be included in thie list, each with an optional matching certificate.

Specifying public keys¶

Public keys may be passed into AsyncSSH in a variety of forms. The simplest option is to pass the name of a file containing the list of public keys to read in using read_public_key_list().

An alternate form involves passing in a list of values each of which can be either the name of a file to load a key from, a byte string to import it from, or an already loaded SSHKey public key. See the function import_public_key() for the list of supported public key formats.

SSHKey¶

class asyncssh.SSHKey[source]¶

Parent class which holds an asymmetric encryption key

export_private_key(format_name, passphrase=None, cipher_name='aes256-cbc', hash_name='sha256', pbe_version=2, rounds=16)[source]¶

Export a private key in the requested format

This function returns this object’s private key encoded in the requested format. If a passphrase is specified, the key will be exported in encrypted form.

Available formats include:

pkcs1-der, pkcs1-pem, pkcs8-der, pkcs8-pem, openssh

Encryption is supported in pkcs1-pem, pkcs8-der, pkcs8-pem, and openssh formats. For pkcs1-pem, only the cipher can be specified. For pkcs8-der and pkcs-8, cipher, hash and PBE version can be specified. For openssh, cipher and rounds can be specified.

Available ciphers for pkcs1-pem are:

aes128-cbc, aes192-cbc, aes256-cbc, des-cbc, des3-cbc

Available ciphers for pkcs8-der and pkcs8-pem are:

aes128-cbc, aes192-cbc, aes256-cbc, blowfish-cbc, cast128-cbc, des-cbc, des2-cbc, des3-cbc, rc4-40, rc4-128

Available ciphers for openssh format include the following encryption algorithms.

Available hashes include:

md5, sha1, sha256, sha384, sha512, sha512-224, sha512-256

Available PBE versions include 1 for PBES1 and 2 for PBES2.

Not all combinations of cipher, hash, and version are supported.

The default cipher is aes256. In the pkcs8 formats, the default hash is sha256 and default version is PBES2. In openssh format, the default number of rounds is 16.

Parameters:

format_name (str) – The format to export the key in.
passphrase (str) – (optional) A passphrase to encrypt the private key with.
cipher_name (str) – (optional) The cipher to use for private key encryption.
hash_name (str) – (optional) The hash to use for private key encryption.
pbe_version (int) – (optional) The PBE version to use for private key encryption.
rounds (int) – (optional) The number of KDF rounds to apply to the passphrase.

export_public_key(format_name)[source]¶

Export a public key in the requested format

This function returns this object’s public key encoded in the requested format. Available formats include:

pkcs1-der, pkcs1-pem, pkcs8-der, pkcs8-pem, openssh, rfc4716

Parameters:	format (str) – The format to export the key in.

write_private_key(filename, *args, **kwargs)[source]¶

Write a private key to a file in the requested format

This function is a simple wrapper around export_private_key which writes the exported key data to a file.

Parameters:	filename (str) – The filename to write the private key to. args,*kwargs – Additional arguments to pass through to `export_private_key()`.

write_public_key(filename, *args, **kwargs)[source]¶

Write a public key to a file in the requested format

This function is a simple wrapper around export_public_key which writes the exported key data to a file.

Parameters:	filename (str) – The filename to write the public key to. args,*kwargs – Additional arguments to pass through to `export_public_key()`.

SSHKeyPair¶

class asyncssh.SSHKeyPair[source]¶

Parent class which represents an asymmetric key pair

This is an abstract class which provides a method to sign data with a private key and members to access the corresponding algorithm and public key or certificate information needed to identify what key was used for signing.

algorithm¶: The public key or certificate algorithm associated with this key pair.

public_data¶: The public key associated with this key pair in OpenSSH binary format.

sign(data)[source]¶

Sign a block of data with this private key

Parameters:	data (str) – The data to be signed.
Returns:	bytes containing the signature.

SSHCertificate¶

class asyncssh.SSHCertificate[source]¶

Parent class which holds an SSH certificate

validate(cert_type, principal)[source]¶

Validate the certificate type, validity period, and principal

This method validates that the certificate is of the specified type, that the current time is within the certificate validity period, and that the principal being authenticated is one of the certificate’s valid principals.

Parameters:	cert_type (int) – The expected certificate type. principal (str) – The principal being authenticated.
Raises:	`ValueError` if any of the validity checks fail

import_private_key¶

asyncssh.import_private_key(data, passphrase=None)[source]¶

Import a private key

This function imports a private key encoded in PKCS#1 or PKCS#8 DER or PEM format or OpenSSH format. Encrypted private keys can be imported by specifying the passphrase needed to decrypt them.

Parameters:	data (bytes or ASCII string) – The data to import. passphrase (str) – (optional) The passphrase to use to decrypt the key.
Returns:	An `SSHKey` private key

import_public_key¶

asyncssh.import_public_key(data)[source]¶

Import a public key

This function imports a public key encoded in OpenSSH, RFC4716, or PKCS#1 or PKCS#8 DER or PEM format.

Parameters:	data (bytes or ASCII string) – The data to import.
Returns:	An `SSHKey` public key

import_certificate¶

asyncssh.import_certificate(data)[source]¶

Import a certificate

This function imports an SSH certificate in OpenSSH or RFC4716 format.

Parameters:	data (bytes or ASCII string) – The data to import.
Returns:	An `SSHCertificate` certificate

read_private_key¶

asyncssh.read_private_key(filename, passphrase=None)[source]¶

Read a private key from a file

This function reads a private key from a file. See the function import_private_key() for information about the formats supported.

Parameters:	filename (str) – The file to read the key from. passphrase (str) – (optional) The passphrase to use to decrypt the key.
Returns:	An `SSHKey` private key

read_public_key¶

asyncssh.read_public_key(filename)[source]¶

Read a public key from a file

This function reads a public key from a file. See the function import_public_key() for information about the formats supported.

Parameters:	filename (str) – The file to read the key from.
Returns:	An `SSHKey` public key

read_certificate¶

asyncssh.read_certificate(filename)[source]¶

Read a certificate from a file

This function reads an SSH certificate from a file. See the function import_certificate() for information about the formats supported.

Parameters:	filename (str) – The file to read the certificate from.
Returns:	An `SSHCertificate` certificate

read_private_key_list¶

asyncssh.read_private_key_list(filename, passphrase=None)[source]¶

Read a list of private keys from a file

This function reads a list of private keys from a file. See the function import_private_key() for information about the formats supported. If any of the keys are encrypted, they must all be encrypted with the same passphrase.

Parameters:	filename (str) – The file to read the keys from. passphrase (str) – (optional) The passphrase to use to decrypt the keys.
Returns:	A list of `SSHKey` private keys

read_public_key_list¶

asyncssh.read_public_key_list(filename)[source]¶

Read a list of public keys from a file

This function reads a list of public keys from a file. See the function import_public_key() for information about the formats supported.

Parameters:	filename (str) – The file to read the keys from.
Returns:	A list of `SSHKey` public keys

read_certificate_list¶

asyncssh.read_certificate_list(filename)[source]¶

Read a list of certificates from a file

This function reads a list of SSH certificates from a file. See the function import_certificate() for information about the formats supported.

Parameters:	filename (str) – The file to read the certificates from.
Returns:	A list of `SSHCertificate` certificates

SSH Agent Support¶

SSHAgentClient¶

class asyncssh.SSHAgentClient[source]¶

SSH agent client

get_keys()[source]¶

Request the available client keys

This method is a coroutine which returns a list of client keys available in the ssh-agent.

Returns:	A list of `SSHKeyPair` objects

close()[source]¶

Close the SSH agent connection

This method closes the connection to the ssh-agent. Any attempts to use this :class:SSHAgentClient or the key pairs it previously returned will result in an error.

connect_agent¶

asyncssh.connect_agent(agent_path=None, *, loop=None)[source]¶

Make a connection to the SSH agent

This function attempts to connect to an ssh-agent process listening on a UNIX domain socket at agent_path. If not provided, it will attempt to get the path from the SSH_AUTH_SOCK environment variable.

If the connection is successful, an SSHAgentClient object is returned that has methods on it you can use to query the ssh-agent. If no path is specified and the environment variable is not set or the connection to the agent fails, this function returns None.

Parameters:	agent_path (str or `SSHServerConnection`) – (optional) The path to use to contact the ssh-agent process, or the `SSHServerConnection` to forward the agent request over. loop – (optional) The event loop to use when creating the connection. If not specified, the default event loop is used.
Returns:	An `SSHAgentClient` or `None`

Known Hosts¶

AsyncSSH supports OpenSSH-style known_hosts files, including both plain and hashed host entries. Regular and negated host patterns are supported in plain entries. AsyncSSH also supports the @cert_authority marker to indicate certificate authority keys and the @revoked marker to indicate revoked keys which should no longer be trusted.

Specifying known hosts¶

Known hosts may be passed into AsyncSSH via the known_hosts argument to create_connection(). This can be the name of a file containing a list of known hosts or an SSHKnownHosts object which was previously imported from a string by calling import_known_hosts() or read from a file by calling read_known_hosts().

Alternately, known hosts can be passed into AsyncSSH as a sequence of three public key lists containing trusted host keys, trusted CA keys, and revoked keys which should no longer be trusted. See Specifying public keys for the allowed form of each of these values.

SSHKnownHosts¶

class asyncssh.SSHKnownHosts[source]¶

An SSH known hosts list

match(host, addr, port)[source]¶

Match a host, IP address, and port against known_hosts patterns

If the port is not the default port and no match is found for it, the lookup is attempted again without a port number.

Parameters:	host (str) – The hostname of the target host addr (str) – The IP address of the target host port (int) – The port number on the target host, or `None` for the default
Returns:	A tuple of matching host keys, CA keys, and revoked keys

import_known_hosts¶

asyncssh.import_known_hosts(data)[source]¶

Import SSH known hosts

This function imports known host patterns and keys in OpenSSH known hosts format.

Parameters:	data (str) – The known hosts data to import
Returns:	An `SSHKnownHosts` object

read_known_hosts¶

asyncssh.read_known_hosts(filename)[source]¶

Read SSH known hosts from a file

This function reads known host patterns and keys in OpenSSH known hosts format from a file.

Parameters:	filename (str) – The file to read the known hosts from
Returns:	An `SSHKnownHosts` object

match_known_hosts¶

asyncssh.match_known_hosts(known_hosts, host, addr, port)[source]¶

Match a host, IP address, and port against a known_hosts list

This function looks up a host, IP address, and port in a list of host patterns in OpenSSH known_hosts format and returns the host keys, CA keys, and revoked keys which match.

The known_hosts argument can be a string containing the filename to load the host patterns from, a byte string containing host pattern data, or an already loaded SSHKnownHosts object.

If the port is not the default port and no match is found for it, the lookup is attempted again without a port number.

Parameters:	known_hosts (str or bytes or `SSHKnownHosts`) – The host patterns to match against host (str) – The hostname of the target host addr (str) – The IP address of the target host port (int) – The port number on the target host, or `None` for the default
Returns:	A tuple of matching host keys, CA keys, and revoked keys

Authorized Keys¶

AsyncSSH supports OpenSSH-style authorized_keys files, including the cert-authority option to validate user certificates, enforcement of from and principals options to restrict key matching, enforcement of no-pty, no-port-forwarding, and permitopen options, and support for command and environment options.

Specifying authorized keys¶

Authorized keys may be passed into AsyncSSH via the authorized_client_keys argument to create_server() or by calling set_authorized_keys() on the SSHServerConnection from within the begin_auth() method in SSHServer.

Authorized keys can be provided as either the name of a file to read the keys from or an SSHAuthorizedKeys object which was previously imported from a string by calling import_authorized_keys() or read from a file by calling read_authorized_keys().

SSHAuthorizedKeys¶

class asyncssh.SSHAuthorizedKeys[source]¶: An SSH authorized keys list

import_authorized_keys¶

asyncssh.import_authorized_keys(data)[source]¶

Import SSH authorized keys

This function imports public keys and associated options in OpenSSH authorized keys format.

Parameters:	data (str) – The key data to import.
Returns:	An `SSHAuthorizedKeys` object

read_authorized_keys¶

asyncssh.read_authorized_keys(filename)[source]¶

Read SSH authorized keys from a file

This function reads public keys and associated options in OpenSSH authorized_keys format from a file.

Parameters:	filename (str) – The file to read the keys from.
Returns:	An `SSHAuthorizedKeys` object

Exceptions¶

PasswordChangeRequired¶

exception asyncssh.PasswordChangeRequired(prompt, lang='en-US')[source]¶

SSH password change required

This exception is raised during password validation on the server to indicate that a password change is required. It shouuld be raised when the password provided is valid but expired, to trigger the client to provide a new password.

Parameters:	prompt (str) – The prompt requesting that the user enter a new password lang (str) – The language that the prompt is in

BreakReceived¶

exception asyncssh.BreakReceived(msec)[source]¶

SSH break request received

This exception is raised on an SSH server stdin stream when the client sends a break on the channel.

Parameters:	msec (int) – The duration of the break in milliseconds

SignalReceived¶

exception asyncssh.SignalReceived(signal)[source]¶

SSH signal request received

This exception is raised on an SSH server stdin stream when the client sends a signal on the channel.

Parameters:	signal (str) – The name of the signal sent by the client

TerminalSizeChanged¶

exception asyncssh.TerminalSizeChanged(width, height, pixwidth, pixheight)[source]¶

SSH terminal size change notification received

This exception is raised on an SSH server stdin stream when the client sends a terminal size change on the channel.

Parameters:	width (int) – The new terminal width height (int) – The new terminal height pixwidth (int) – The new terminal width in pixels pixheight (int) – The new terminal height in pixels

DisconnectError¶

exception asyncssh.DisconnectError(code, reason, lang='en-US')[source]¶

SSH disconnect error

This exception is raised when a serious error occurs which causes the SSH connection to be disconnected. Exception codes should be taken from disconnect reason codes.

Parameters:	code (int) – Disconnect reason, taken from disconnect reason codes reason (str) – A human-readable reason for the disconnect lang (str) – The language the reason is in

ChannelOpenError¶

exception asyncssh.ChannelOpenError(code, reason, lang='en-US')[source]¶

SSH channel open error

This exception is raised by connection handlers to report channel open failures.

Parameters:	code (int) – Channel open failure reason, taken from channel open failure reason codes reason (str) – A human-readable reason for the channel open failure lang (str) – The language the reason is in

SFTPError¶

exception asyncssh.SFTPError(code, reason, lang='en-US')[source]¶

SFTP error

This exception is raised when an error occurs while processing an SFTP request. Exception codes should be taken from SFTP error codes.

Parameters:	code (int) – Disconnect reason, taken from disconnect reason codes reason (str) – A human-readable reason for the disconnect lang (str) – The language the reason is in

KeyImportError¶

exception asyncssh.KeyImportError[source]¶

Key import error

This exception is raised by key import functions when the data provided cannot be imported as a valid key.

KeyExportError¶

exception asyncssh.KeyExportError[source]¶

Key export error

This exception is raised by key export functions when the requested format is unknown or encryption is requested for a format which doesn’t support it.

KeyEncryptionError¶

exception asyncssh.KeyEncryptionError[source]¶

Key encryption error

This exception is raised by key decryption functions when the data provided is not a valid encrypted private key.

Supported Algorithms¶

Key exchange algorithms¶

The following are the key exchange algorithms currently supported by AsyncSSH:

curve25519-sha256@libssh.org

ecdh-sha2-nistp521

ecdh-sha2-nistp384

ecdh-sha2-nistp256

diffie-hellman-group-exchange-sha256

diffie-hellman-group-exchange-sha1

diffie-hellman-group14-sha1

diffie-hellman-group1-sha1

Curve25519 support is only available when the libnacl package and libsodium library are installed.

Encryption algorithms¶

The following are the encryption algorithms currently supported by AsyncSSH:

chacha20-poly1305@openssh.com

aes256-ctr

aes192-ctr

aes128-ctr

aes256-gcm@openssh.com

aes128-gcm@openssh.com

aes256-cbc

aes192-cbc

aes128-cbc

3des-cbc

blowfish-cbc

cast128-cbc

arcfour256

arcfour128

arcfour

Chacha20-poly1305 support is only available when the libnacl package and libsodium library are installed.

MAC algorithms¶

The following are the MAC algorithms currently supported by AsyncSSH:

hmac-sha2-256-etm@openssh.com

hmac-sha2-512-etm@openssh.com

hmac-sha1-etm@openssh.com

hmac-md5-etm@openssh.com

hmac-sha2-256-96-etm@openssh.com

hmac-sha2-512-96-etm@openssh.com

hmac-sha1-96-etm@openssh.com

hmac-md5-96-etm@openssh.com

hmac-sha2-256

hmac-sha2-512

hmac-sha1

hmac-md5

hmac-sha2-256-96

hmac-sha2-512-96

hmac-sha1-96

hmac-md5-96

Compression algorithms¶

The following are the compression algorithms currently supported by AsyncSSH:

zlib@openssh.com

zlib

none

Public key & certificate algorithms¶

The following are the public key and certificate algorithms currently supported by AsyncSSH:

ssh-ed25519-cert-v01@openssh.com

ecdsa-sha2-nistp521-cert-v01@openssh.com

ecdsa-sha2-nistp384-cert-v01@openssh.com

ecdsa-sha2-nistp256-cert-v01@openssh.com

ssh-rsa-cert-v01@openssh.com

ssh-dss-cert-v01@openssh.com

ssh-ed25519

ecdsa-sha2-nistp521

ecdsa-sha2-nistp384

ecdsa-sha2-nistp256

ssh-rsa

ssh-dss

Ed25519 support is only available when the libnacl package and libsodium library are installed.

Constants¶

Certificate types¶

The following values can be specified as certificate types:

CERT_TYPE_USER

CERT_TYPE_HOST

Disconnect reasons¶

The following values defined in section 11.1 of RFC 4253#section-11.1 can be specified as disconnect reason codes:

DISC_HOST_NOT_ALLOWED_TO_CONNECT

DISC_PROTOCOL_ERROR

DISC_KEY_EXCHANGE_FAILED

DISC_RESERVED

DISC_MAC_ERROR

DISC_COMPRESSION_ERROR

DISC_SERVICE_NOT_AVAILABLE

DISC_PROTOCOL_VERSION_NOT_SUPPORTED

DISC_HOST_KEY_NOT_VERIFYABLE

DISC_CONNECTION_LOST

DISC_BY_APPLICATION

DISC_TOO_MANY_CONNECTIONS

DISC_AUTH_CANCELLED_BY_USER

DISC_NO_MORE_AUTH_METHODS_AVAILABLE

DISC_ILLEGAL_USER_NAME

Channel open failure reasons¶

The following values defined in section 5.1 of RFC 4254#section-5.1 can be specified as channel open failure reason codes:

OPEN_ADMINISTRATIVELY_PROHIBITED

OPEN_CONNECT_FAILED

OPEN_UNKNOWN_CHANNEL_TYPE

OPEN_RESOURCE_SHORTAGE

OPEN_REQUEST_PTY_FAILED

OPEN_REQUEST_SESSION_FAILED

SFTP error codes¶

The following values defined in the SSH File Transfer Internet Draft can be specified as SFTP error codes:

FX_OK

FX_EOF

FX_NO_SUCH_FILE

FX_PERMISSION_DENIED

FX_FAILURE

FX_BAD_MESSAGE

FX_NO_CONNECTION

FX_CONNECTION_LOST

FX_OP_UNSUPPORTED

Extended data types¶

The following values defined in section 5.2 of RFC 4254#section-5.2 can be specified as SSH extended channel data types:

EXTENDED_DATA_STDERR

POSIX terminal modes¶

The following values defined in section 8 of RFC 4254#section-8 can be specified as PTY mode opcodes:

PTY_OP_END

PTY_VINTR

PTY_VQUIT

PTY_VERASE

PTY_VKILL

PTY_VEOF

PTY_VEOL

PTY_VEOL2

PTY_VSTART

PTY_VSTOP

PTY_VSUSP

PTY_VDSUSP

PTY_VREPRINT

PTY_WERASE

PTY_VLNEXT

PTY_VFLUSH

PTY_VSWTCH

PTY_VSTATUS

PTY_VDISCARD

PTY_IGNPAR

PTY_PARMRK

PTY_INPCK

PTY_ISTRIP

PTY_INLCR

PTY_IGNCR

PTY_ICRNL

PTY_IUCLC

PTY_IXON

PTY_IXANY

PTY_IXOFF

PTY_IMAXBEL

PTY_ISIG

PTY_ICANON

PTY_XCASE

PTY_ECHO

PTY_ECHOE

PTY_ECHOK

PTY_ECHONL

PTY_NOFLSH

PTY_TOSTOP

PTY_IEXTEN

PTY_ECHOCTL

PTY_ECHOKE

PTY_PENDIN

PTY_OPOST

PTY_OLCUC

PTY_ONLCR

PTY_OCRNL

PTY_ONOCR

PTY_ONLRET

PTY_CS7

PTY_CS8

PTY_PARENB

PTY_PARODD

PTY_OP_ISPEED

PTY_OP_OSPEED

Field	Description	Type
size	File size in bytes	uint64
uid	User id of file owner	uint32
gid	Group id of file owner	uint32
permissions	Bit mask of POSIX file permissions,	uint32
atime	Last access time, UNIX epoch seconds	uint32
mtime	Last modification time, UNIX epoch seconds	uint32

Field	Description	Type
bsize	File system block size (I/O size)	uint64
frsize	Fundamental block size (allocation size)	uint64
blocks	Total data blocks (in frsize units)	uint64
bfree	Free data blocks	uint64
bavail	Available data blocks (for non-root)	uint64
files	Total file inodes	uint64
ffree	Free file inodes	uint64
favail	Available file inodes (for non-root)	uint64
fsid	File system id	uint64
flags	File system flags (read-only, no-setuid)	uint64
namemax	Maximum filename length	uint64

Field	Description	Type
filename	Filename	str or bytes
longname	Expanded form of filename & attrs	str or bytes
attrs	File attributes	`SFTPAttrs`