angelos.lib.ssh.node

Module docstring.

class angelos.lib.ssh.node.NodesServer(ioc)

Bases: angelos.lib.ssh.ssh.SSHServer

SSH Server for the nodes.

begin_auth(username)

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.

If blocking operations need to be performed to prepare the state needed to complete the authentication, this method may be defined as a coroutine.

Parameters

username (str) – The name of the user being authenticated

Returns

A bool indicating whether authentication is required

session_requested()

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

validate_public_key(username, key)

Return whether key is an authorized client key for this user

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