sshmitm.interfaces.server module

class sshmitm.interfaces.server.BaseServerInterface(session: Session)

Bases: ServerInterface, BaseModule

class sshmitm.interfaces.server.ProxySFTPServer(channel: Channel, name: str, server: ServerInterface, sftp_si: Type[SFTPServerInterface], session: Session, *largs: Any, **kwargs: Any)

Bases: SFTPServer

finish_subsystem() None

Perform any cleanup at the end of a subsystem. The default implementation just closes the channel.

New in version 1.1.

start_subsystem(name: str, transport: Transport, channel: Channel) None

Process an ssh subsystem in server mode. This method is called on a new object (and in a new thread) for each subsystem request. It is assumed that all subsystem logic will take place here, and when the subsystem is finished, this method will return. After this method returns, the channel is closed.

The combination of transport and channel are unique; this handler corresponds to exactly one .Channel on one .Transport.

Note

It is the responsibility of this method to exit if the underlying .Transport is closed. This can be done by checking .Transport.is_active or noticing an EOF on the .Channel. If this method loops forever without checking for this case, your Python interpreter may refuse to exit because this thread will still be running.

Parameters:
  • name (str) – name of the requested subsystem.

  • transport (.Transport) – the server-mode .Transport.

  • channel (.Channel) – the channel associated with this subsystem request.

class sshmitm.interfaces.server.ServerInterface(session: Session)

Bases: BaseServerInterface

ssh server implementation for SSH-MITM

cancel_port_forward_request(address: str, port: int) None

The client would like to cancel a previous port-forwarding request. If the given address and port is being forwarded across this ssh connection, the port should be closed.

Parameters:
  • address (str) – the forwarded address

  • port (int) – the forwarded port

check_auth_interactive(username: str, submethods: Union[bytes, str]) Union[int, InteractiveQuery]

Begin an interactive authentication challenge, if supported. You should override this method in server mode if you want to support the "keyboard-interactive" auth type, which requires you to send a series of questions for the client to answer.

Return AUTH_FAILED if this auth method isn’t supported. Otherwise, you should return an .InteractiveQuery object containing the prompts and instructions for the user. The response will be sent via a call to check_auth_interactive_response.

The default implementation always returns AUTH_FAILED.

Parameters:
  • username (str) – the username of the authenticating client

  • submethods (str) – a comma-separated list of methods preferred by the client (usually empty)

Returns:

AUTH_FAILED if this auth method isn’t supported; otherwise an object containing queries for the user

Return type:

int or .InteractiveQuery

check_auth_interactive_response(responses: List[str]) Union[int, InteractiveQuery]

Continue or finish an interactive authentication challenge, if supported. You should override this method in server mode if you want to support the "keyboard-interactive" auth type.

Return AUTH_FAILED if the responses are not accepted, AUTH_SUCCESSFUL if the responses are accepted and complete the authentication, or AUTH_PARTIALLY_SUCCESSFUL if your authentication is stateful, and this set of responses is accepted for authentication, but more authentication is required. (In this latter case, get_allowed_auths will be called to report to the client what options it has for continuing the authentication.)

If you wish to continue interactive authentication with more questions, you may return an .InteractiveQuery object, which should cause the client to respond with more answers, calling this method again. This cycle can continue indefinitely.

The default implementation always returns AUTH_FAILED.

Parameters:

responses – list of str responses from the client

Returns:

AUTH_FAILED if the authentication fails; AUTH_SUCCESSFUL if it succeeds; AUTH_PARTIALLY_SUCCESSFUL if the interactive auth is successful, but authentication must continue; otherwise an object containing queries for the user

Return type:

int or .InteractiveQuery

check_auth_none(username: str) int

Determine if a client may open channels with no (further) authentication.

Return AUTH_FAILED if the client must authenticate, or AUTH_SUCCESSFUL if it’s okay for the client to not authenticate.

The default implementation always returns AUTH_FAILED.

Parameters:

username (str) – the username of the client.

Returns:

AUTH_FAILED if the authentication fails; AUTH_SUCCESSFUL if it succeeds.

Return type:

int

check_auth_password(username: str, password: str) int

Determine if a given username and password supplied by the client is acceptable for use in authentication.

Return AUTH_FAILED if the password is not accepted, AUTH_SUCCESSFUL if the password is accepted and completes the authentication, or AUTH_PARTIALLY_SUCCESSFUL if your authentication is stateful, and this key is accepted for authentication, but more authentication is required. (In this latter case, get_allowed_auths will be called to report to the client what options it has for continuing the authentication.)

The default implementation always returns AUTH_FAILED.

Parameters:
  • username (str) – the username of the authenticating client.

  • password (str) – the password given by the client.

Returns:

AUTH_FAILED if the authentication fails; AUTH_SUCCESSFUL if it succeeds; AUTH_PARTIALLY_SUCCESSFUL if the password auth is successful, but authentication must continue.

Return type:

int

check_auth_publickey(username: str, key: PKey) int

Determine if a given key supplied by the client is acceptable for use in authentication. You should override this method in server mode to check the username and key and decide if you would accept a signature made using this key.

Return AUTH_FAILED if the key is not accepted, AUTH_SUCCESSFUL if the key is accepted and completes the authentication, or AUTH_PARTIALLY_SUCCESSFUL if your authentication is stateful, and this password is accepted for authentication, but more authentication is required. (In this latter case, get_allowed_auths will be called to report to the client what options it has for continuing the authentication.)

Note that you don’t have to actually verify any key signtature here. If you’re willing to accept the key, Paramiko will do the work of verifying the client’s signature.

The default implementation always returns AUTH_FAILED.

Parameters:
  • username (str) – the username of the authenticating client

  • key (.PKey) – the key object provided by the client

Returns:

AUTH_FAILED if the client can’t authenticate with this key; AUTH_SUCCESSFUL if it can; AUTH_PARTIALLY_SUCCESSFUL if it can authenticate with this key but must continue with authentication

Return type:

int

check_channel_direct_tcpip_request(chanid: int, origin: Tuple[str, int], destination: Tuple[str, int]) int

Determine if a local port forwarding channel will be granted, and return OPEN_SUCCEEDED or an error code. This method is called in server mode when the client requests a channel, after authentication is complete.

The chanid parameter is a small number that uniquely identifies the channel within a .Transport. A .Channel object is not created unless this method returns OPEN_SUCCEEDED – once a .Channel object is created, you can call .Channel.get_id to retrieve the channel ID.

The origin and destination parameters are (ip_address, port) tuples that correspond to both ends of the TCP connection in the forwarding tunnel.

The return value should either be OPEN_SUCCEEDED (or 0) to allow the channel request, or one of the following error codes to reject it:

  • OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED

  • OPEN_FAILED_CONNECT_FAILED

  • OPEN_FAILED_UNKNOWN_CHANNEL_TYPE

  • OPEN_FAILED_RESOURCE_SHORTAGE

The default implementation always returns OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED.

Parameters:
  • chanid (int) – ID of the channel

  • origin (tuple) – 2-tuple containing the IP address and port of the originator (client side)

  • destination (tuple) – 2-tuple containing the IP address and port of the destination (server side)

Returns:

an int success or failure code (listed above)

check_channel_env_request(channel: Channel, name: bytes, value: bytes) bool

Check whether a given environment variable can be specified for the given channel. This method should return True if the server is willing to set the specified environment variable. Note that some environment variables (e.g., PATH) can be exceedingly dangerous, so blindly allowing the client to set the environment is almost certainly not a good idea.

The default implementation always returns False.

Parameters:
  • channel – the .Channel the env request arrived on

  • name (str) – name

  • value (str) – Channel value

Returns:

A boolean

check_channel_exec_request(channel: Channel, command: bytes) bool

Determine if a shell command will be executed for the client. If this method returns True, the channel should be connected to the stdin, stdout, and stderr of the shell command.

The default implementation always returns False.

Parameters:
  • channel (.Channel) – the .Channel the request arrived on.

  • command (str) – the command to execute.

Returns:

True if this channel is now hooked up to the stdin, stdout, and stderr of the executing command; False if the command will not be executed.

New in version 1.1.

check_channel_forward_agent_request(channel: Channel) bool

Determine if the client will be provided with an forward agent session. If this method returns True, the server will allow SSH Agent forwarding.

The default implementation always returns False.

Parameters:

channel (.Channel) – the .Channel the request arrived on

Returns:

True if the AgentForward was loaded; False if not

check_channel_pty_request(channel: Channel, term: bytes, width: int, height: int, pixelwidth: int, pixelheight: int, modes: bytes) bool

Determine if a pseudo-terminal of the given dimensions (usually requested for shell access) can be provided on the given channel.

The default implementation always returns False.

Parameters:
  • channel (.Channel) – the .Channel the pty request arrived on.

  • term (str) – type of terminal requested (for example, "vt100").

  • width (int) – width of screen in characters.

  • height (int) – height of screen in characters.

  • pixelwidth (int) – width of screen in pixels, if known (may be 0 if unknown).

  • pixelheight (int) – height of screen in pixels, if known (may be 0 if unknown).

Returns:

True if the pseudo-terminal has been allocated; False otherwise.

check_channel_request(kind: str, chanid: int) int

Determine if a channel request of a given type will be granted, and return OPEN_SUCCEEDED or an error code. This method is called in server mode when the client requests a channel, after authentication is complete.

If you allow channel requests (and an ssh server that didn’t would be useless), you should also override some of the channel request methods below, which are used to determine which services will be allowed on a given channel:

  • check_channel_pty_request

  • check_channel_shell_request

  • check_channel_subsystem_request

  • check_channel_window_change_request

  • check_channel_x11_request

  • check_channel_forward_agent_request

The chanid parameter is a small number that uniquely identifies the channel within a .Transport. A .Channel object is not created unless this method returns OPEN_SUCCEEDED – once a .Channel object is created, you can call .Channel.get_id to retrieve the channel ID.

The return value should either be OPEN_SUCCEEDED (or 0) to allow the channel request, or one of the following error codes to reject it:

  • OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED

  • OPEN_FAILED_CONNECT_FAILED

  • OPEN_FAILED_UNKNOWN_CHANNEL_TYPE

  • OPEN_FAILED_RESOURCE_SHORTAGE

The default implementation always returns OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED.

Parameters:
  • kind (str) – the kind of channel the client would like to open (usually "session").

  • chanid (int) – ID of the channel

Returns:

an int success or failure code (listed above)

check_channel_shell_request(channel: Channel) bool

Determine if a shell will be provided to the client on the given channel. If this method returns True, the channel should be connected to the stdin/stdout of a shell (or something that acts like a shell).

The default implementation always returns False.

Parameters:

channel (.Channel) – the .Channel the request arrived on.

Returns:

True if this channel is now hooked up to a shell; False if a shell can’t or won’t be provided.

check_channel_subsystem_request(channel: Channel, name: str) bool

Determine if a requested subsystem will be provided to the client on the given channel. If this method returns True, all future I/O through this channel will be assumed to be connected to the requested subsystem. An example of a subsystem is sftp.

The default implementation checks for a subsystem handler assigned via .Transport.set_subsystem_handler. If one has been set, the handler is invoked and this method returns True. Otherwise it returns False.

Note

Because the default implementation uses the .Transport to identify valid subsystems, you probably won’t need to override this method.

Parameters:
  • channel (.Channel) – the .Channel the pty request arrived on.

  • name (str) – name of the requested subsystem.

Returns:

True if this channel is now hooked up to the requested subsystem; False if that subsystem can’t or won’t be provided.

check_channel_window_change_request(channel: Channel, width: int, height: int, pixelwidth: int, pixelheight: int) bool

Determine if the pseudo-terminal on the given channel can be resized. This only makes sense if a pty was previously allocated on it.

The default implementation always returns False.

Parameters:
  • channel (.Channel) – the .Channel the pty request arrived on.

  • width (int) – width of screen in characters.

  • height (int) – height of screen in characters.

  • pixelwidth (int) – width of screen in pixels, if known (may be 0 if unknown).

  • pixelheight (int) – height of screen in pixels, if known (may be 0 if unknown).

Returns:

True if the terminal was resized; False if not.

check_channel_x11_request(channel: Channel, single_connection: bool, auth_protocol: str, auth_cookie: ByteString, screen_number: int) bool

Determine if the client will be provided with an X11 session. If this method returns True, X11 applications should be routed through new SSH channels, using .Transport.open_x11_channel.

The default implementation always returns False.

Parameters:
  • channel (.Channel) – the .Channel the X11 request arrived on

  • single_connection (bool) – True if only a single X11 channel should be opened, else False.

  • auth_protocol (str) – the protocol used for X11 authentication

  • auth_cookie (str) – the cookie used to authenticate to X11

  • screen_number (int) – the number of the X11 screen to connect to

Returns:

True if the X11 session was opened; False if not

check_global_request(kind: str, msg: Message) Union[bool, Tuple[Union[bool, int, str], ...]]

Handle a global request of the given kind. This method is called in server mode and client mode, whenever the remote host makes a global request. If there are any arguments to the request, they will be in msg.

There aren’t any useful global requests defined, aside from port forwarding, so usually this type of request is an extension to the protocol.

If the request was successful and you would like to return contextual data to the remote host, return a tuple. Items in the tuple will be sent back with the successful result. (Note that the items in the tuple can only be strings, ints, longs, or bools.)

The default implementation always returns False, indicating that it does not support any global requests.

Note

Port forwarding requests are handled separately, in check_port_forward_request.

Parameters:
  • kind (str) – the kind of global request being made.

  • msg (.Message) – any extra arguments to the request.

Returns:

True or a tuple of data if the request was granted; False otherwise.

check_port_forward_request(address: str, port: int) int

Note that the if the client requested the port, we must handle it or return false. Only if it requested 0 as port we can open a random port (actually the OS will tell us which port). If it can’t be opened, we just return false.

get_allowed_auths(username: str) str

Return a list of authentication methods supported by the server. This list is sent to clients attempting to authenticate, to inform them of authentication methods that might be successful.

The “list” is actually a string of comma-separated names of types of authentication. Possible values are "password", "publickey", and "none".

The default implementation always returns "password".

Parameters:

username (str) – the username requesting authentication.

Returns:

a comma-separated str of authentication types

classmethod parser_arguments() None