Package paramiko :: Class Transport |
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# Class Transport

source code

            object --+
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    threading._Verbose --+
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          threading.Thread --+
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                            Transport

An SSH Transport attaches to a stream (usually a socket), negotiates an encrypted session, authenticates, and then creates stream tunnels, called Channels, across the session. Multiple channels can be multiplexed across a single session (and often are, in the case of port forwardings).

Instance Methods
__init__(self, sock) Create a new SSH session over an existing socket, or socket-like object. | source code
str |
__repr__(self) Returns a string representation of this object, for debugging. | source code
Channel |
accept(self, timeout=None) Return the next channel opened by the client over this transport, in server mode. | source code
add_server_key(self, key) Add a host key to the list of keys used for server mode. | source code
atfork(self) Terminate this Transport without closing the session. | source code
list |
auth_interactive(self, username, handler, submethods=`'````'`) Authenticate to the server interactively. | source code
list |
auth_none(self, username) Try to authenticate to the server using no authentication at all. | source code
list |
auth_password(self, username, password, event=None, fallback=True) Authenticate to the server using a password. | source code
list |
auth_publickey(self, username, key, event=None) Authenticate to the server using a private key. | source code
cancel_port_forward(self, address, port) Ask the server to cancel a previous port-forwarding request. | source code
close(self) Close this session, and any open channels that are tied to it. | source code
connect(self, hostkey=None, username=`'````'`, password=None, pkey=None) Negotiate an SSH2 session, and optionally verify the server's host key and authenticate using a password or private key. | source code
Exception |
get_exception(self) Return any exception that happened during the last server request. | source code
bool |
get_hexdump(self) Return `True` if the transport is currently logging hex dumps of protocol traffic. | source code
str |
get_log_channel(self) Return the channel name used for this transport's logging. | source code
PKey |
get_remote_server_key(self) Return the host key of the server (in client mode). | source code
SecurityOptions |
get_security_options(self) Return a SecurityOptions object which can be used to tweak the encryption algorithms this transport will permit, and the order of preference for them. | source code
PKey |
get_server_key(self) Return the active host key, in server mode. | source code
string |
get_username(self) Return the username this connection is authenticated for. | source code
tuple(str, int) |
getpeername(self) Return the address of the remote side of this Transport, if possible. | source code
Message |
global_request(self, kind, data=None, wait=True) Make a global request to the remote host. | source code
bool |
is_active(self) Return true if this session is active (open). | source code
bool |
is_authenticated(self) Return true if this session is active and authenticated. | source code
Channel |
open_channel(self, kind, dest_addr=None, src_addr=None) Request a new channel to the server. | source code
open_forwarded_tcpip_channel(self, (src_addr, src_port), (dest_addr, dest_port)) Request a new channel back to the client, of type `"forwarded-tcpip"`. | source code
Channel |
open_session(self) Request a new channel to the server, of type `"session"`. | source code
SFTPClient |
open_sftp_client(self) Create an SFTP client channel from an open transport. | source code
Channel |
open_x11_channel(self, src_addr=None) Request a new channel to the client, of type `"x11"`. | source code
renegotiate_keys(self) Force this session to switch to new keys. | source code
int |
request_port_forward(self, address, port, handler=None) Ask the server to forward TCP connections from a listening port on the server, across this SSH session. | source code
run(self) | source code
send_ignore(self, bytes=None) Send a junk packet across the encrypted link. | source code
set_hexdump(self, hexdump) Turn on/off logging a hex dump of protocol traffic at DEBUG level in the logs. | source code
set_keepalive(self, interval) Turn on/off keepalive packets (default is off). | source code
set_log_channel(self, name) Set the channel for this transport's logging. | source code
set_subsystem_handler(self, name, handler, *larg, **kwarg) Set the handler class for a subsystem in server mode. | source code
start_client(self, event=None) Negotiate a new SSH2 session as a client. | source code
start_server(self, event=None, server=None) Negotiate a new SSH2 session as a server. | source code
stop_thread(self) | source code
use_compression(self, compress=True) Turn on/off compression. | source code
Inherited from `threading.Thread`: `getName`, `isAlive`, `isDaemon`, `join`, `setDaemon`, `setName`, `start` Inherited from `object`: `__delattr__`, `__getattribute__`, `__hash__`, `__new__`, `__reduce__`, `__reduce_ex__`, `__setattr__`, `__str__`

Static Methods
bool |
load_server_moduli(filename=None) (optional) Load a file of prime moduli for use in doing group-exchange key negotiation in server mode. | source code

Properties
Inherited from `object`: `__class__`

Method Details

### __init__(self, sock) (Constructor) | source code
Create a new SSH session over an existing socket, or socket-like object. This only creates the Transport object; it doesn't begin the SSH session yet. Use connect or start_client to begin a client session, or start_server to begin a server session. If the object is not actually a socket, it must have the following methods: `send(str)`: Writes from 1 to `len(str)` bytes, and returns an int representing the number of bytes written. Returns 0 or raises `EOFError` if the stream has been closed. `recv(int)`: Reads from 1 to `int` bytes and returns them as a string. Returns 0 or raises `EOFError` if the stream has been closed. `close()`: Closes the socket. `settimeout(n)`: Sets a (float) timeout on I/O operations. For ease of use, you may also pass in an address (as a tuple) or a host string as the `sock` argument. (A host string is a hostname with an optional port (separated by `":"`) which will be converted into a tuple of `(hostname, port)`.) A socket will be connected to this address and used for communication. Exceptions from the `socket` call may be thrown in this case. Parameters: `sock` (socket) - a socket or socket-like object to create the session over. Overrides: object.__init__

### __repr__(self) (Representation operator) | source code
Returns a string representation of this object, for debugging. Returns: str Overrides: object.__repr__

### accept(self, timeout=None) | source code
Return the next channel opened by the client over this transport, in server mode. If no channel is opened before the given timeout, `None` is returned. Parameters: `timeout` (int) - seconds to wait for a channel, or `None` to wait forever Returns: Channel a new Channel opened by the client

### add_server_key(self, key) | source code
Add a host key to the list of keys used for server mode. When behaving as a server, the host key is used to sign certain packets during the SSH2 negotiation, so that the client can trust that we are who we say we are. Because this is used for signing, the key must contain private key info, not just the public half. Only one key of each type (RSA or DSS) is kept. Parameters: `key` (PKey) - the host key to add, usually an RSAKey or DSSKey.

### atfork(self) | source code
Terminate this Transport without closing the session. On posix systems, if a Transport is open during process forking, both parent and child will share the underlying socket, but only one process can use the connection (without corrupting the session). Use this method to clean up a Transport object without disrupting the other process. Since: 1.5.3

### auth_interactive(self, username, handler, submethods=`'````'`) | source code
Authenticate to the server interactively. A handler is used to answer arbitrary questions from the server. On many servers, this is just a dumb wrapper around PAM. This method will block until the authentication succeeds or fails, peroidically calling the handler asynchronously to get answers to authentication questions. The handler may be called more than once if the server continues to ask questions. The handler is expected to be a callable that will handle calls of the form: `handler(title, instructions, prompt_list)`. The `title` is meant to be a dialog-window title, and the `instructions` are user instructions (both are strings). `prompt_list` will be a list of prompts, each prompt being a tuple of `(str, bool)`. The string is the prompt and the boolean indicates whether the user text should be echoed. A sample call would thus be: `handler('title', 'instructions', [('Password:', False)])`. The handler should return a list or tuple of answers to the server's questions. If the server requires multi-step authentication (which is very rare), this method will return a list of auth types permissible for the next step. Otherwise, in the normal case, an empty list is returned. Parameters: `username` (string) - the username to authenticate as `handler` (callable) - a handler for responding to server questions `submethods` (str) - a string list of desired submethods (optional) Returns: list list of auth types permissible for the next stage of authentication (normally empty). Raises: `BadAuthenticationType` - if public-key authentication isn't allowed by the server for this user `AuthenticationException` - if the authentication failed `SSHException` - if there was a network error Since: 1.5

### auth_none(self, username) | source code
Try to authenticate to the server using no authentication at all. This will almost always fail. It may be useful for determining the list of authentication types supported by the server, by catching the BadAuthenticationType exception raised. Parameters: `username` (string) - the username to authenticate as Returns: list list of auth types permissible for the next stage of authentication (normally empty) Raises: `BadAuthenticationType` - if "none" authentication isn't allowed by the server for this user `SSHException` - if the authentication failed due to a network error Since: 1.5

### auth_password(self, username, password, event=None, fallback=True) | source code
Authenticate to the server using a password. The username and password are sent over an encrypted link. If an `event` is passed in, this method will return immediately, and the event will be triggered once authentication succeeds or fails. On success, is_authenticated will return `True`. On failure, you may use get_exception to get more detailed error information. Since 1.1, if no event is passed, this method will block until the authentication succeeds or fails. On failure, an exception is raised. Otherwise, the method simply returns. Since 1.5, if no event is passed and `fallback` is `True` (the default), if the server doesn't support plain password authentication but does support so-called "keyboard-interactive" mode, an attempt will be made to authenticate using this interactive mode. If it fails, the normal exception will be thrown as if the attempt had never been made. This is useful for some recent Gentoo and Debian distributions, which turn off plain password authentication in a misguided belief that interactive authentication is "more secure". (It's not.) If the server requires multi-step authentication (which is very rare), this method will return a list of auth types permissible for the next step. Otherwise, in the normal case, an empty list is returned. Parameters: `username` (str) - the username to authenticate as `password` (str or unicode) - the password to authenticate with `event` (threading.Event) - an event to trigger when the authentication attempt is complete (whether it was successful or not) `fallback` (bool) - `True` if an attempt at an automated "interactive" password auth should be made if the server doesn't support normal password auth Returns: list list of auth types permissible for the next stage of authentication (normally empty) Raises: `BadAuthenticationType` - if password authentication isn't allowed by the server for this user (and no event was passed in) `AuthenticationException` - if the authentication failed (and no event was passed in) `SSHException` - if there was a network error

### auth_publickey(self, username, key, event=None) | source code
Authenticate to the server using a private key. The key is used to sign data from the server, so it must include the private part. If an `event` is passed in, this method will return immediately, and the event will be triggered once authentication succeeds or fails. On success, is_authenticated will return `True`. On failure, you may use get_exception to get more detailed error information. Since 1.1, if no event is passed, this method will block until the authentication succeeds or fails. On failure, an exception is raised. Otherwise, the method simply returns. If the server requires multi-step authentication (which is very rare), this method will return a list of auth types permissible for the next step. Otherwise, in the normal case, an empty list is returned. Parameters: `username` (string) - the username to authenticate as `key` (PKey) - the private key to authenticate with `event` (threading.Event) - an event to trigger when the authentication attempt is complete (whether it was successful or not) Returns: list list of auth types permissible for the next stage of authentication (normally empty) Raises: `BadAuthenticationType` - if public-key authentication isn't allowed by the server for this user (and no event was passed in) `AuthenticationException` - if the authentication failed (and no event was passed in) `SSHException` - if there was a network error

### cancel_port_forward(self, address, port) | source code
Ask the server to cancel a previous port-forwarding request. No more connections to the given address & port will be forwarded across this ssh connection. Parameters: `address` (str) - the address to stop forwarding `port` (int) - the port to stop forwarding

### connect(self, hostkey=None, username=`'````'`, password=None, pkey=None) | source code
Negotiate an SSH2 session, and optionally verify the server's host key and authenticate using a password or private key. This is a shortcut for start_client, get_remote_server_key, and Transport.auth_password or Transport.auth_publickey. Use those methods if you want more control. You can use this method immediately after creating a Transport to negotiate encryption with a server. If it fails, an exception will be thrown. On success, the method will return cleanly, and an encrypted session exists. You may immediately call open_channel or open_session to get a Channel object, which is used for data transfer. Parameters: `hostkey` (PKey) - the host key expected from the server, or `None` if you don't want to do host key verification. `username` (str) - the username to authenticate as. `password` (str) - a password to use for authentication, if you want to use password authentication; otherwise `None`. `pkey` (PKey) - a private key to use for authentication, if you want to use private key authentication; otherwise `None`. Raises: `SSHException` - if the SSH2 negotiation fails, the host key supplied by the server is incorrect, or authentication fails. Note: If you fail to supply a password or private key, this method may succeed, but a subsequent open_channel or open_session call may fail because you haven't authenticated yet.

### get_exception(self) | source code
Return any exception that happened during the last server request. This can be used to fetch more specific error information after using calls like start_client. The exception (if any) is cleared after this call. Returns: Exception an exception, or `None` if there is no stored exception. Since: 1.1

### get_hexdump(self) | source code
Return `True` if the transport is currently logging hex dumps of protocol traffic. Returns: bool `True` if hex dumps are being logged Since: 1.4

### get_log_channel(self) | source code
Return the channel name used for this transport's logging. Returns: str channel name. Since: 1.2

### get_remote_server_key(self) | source code
Return the host key of the server (in client mode). Returns: PKey public key of the remote server Raises: `SSHException` - if no session is currently active. Note: Previously this call returned a tuple of (key type, key string). You can get the same effect by calling PKey.get_name for the key type, and `str(key)` for the key string.

### get_security_options(self) | source code
Return a SecurityOptions object which can be used to tweak the encryption algorithms this transport will permit, and the order of preference for them. Returns: SecurityOptions an object that can be used to change the preferred algorithms for encryption, digest (hash), public key, and key exchange.

### get_server_key(self) | source code
Return the active host key, in server mode. After negotiating with the client, this method will return the negotiated host key. If only one type of host key was set with add_server_key, that's the only key that will ever be returned. But in cases where you have set more than one type of host key (for example, an RSA key and a DSS key), the key type will be negotiated by the client, and this method will return the key of the type agreed on. If the host key has not been negotiated yet, `None` is returned. In client mode, the behavior is undefined. Returns: PKey host key of the type negotiated by the client, or `None`.

### get_username(self) | source code
Return the username this connection is authenticated for. If the session is not authenticated (or authentication failed), this method returns `None`. Returns: string username that was authenticated, or `None`.

### getpeername(self) | source code
Return the address of the remote side of this Transport, if possible. This is effectively a wrapper around `'getpeername'` on the underlying socket. If the socket-like object has no `'getpeername'` method, then `("unknown", 0)` is returned. Returns: tuple(str, int) the address if the remote host, if known

### global_request(self, kind, data=None, wait=True) | source code
Make a global request to the remote host. These are normally extensions to the SSH2 protocol. Parameters: `kind` (str) - name of the request. `data` (tuple) - an optional tuple containing additional data to attach to the request. `wait` (bool) - `True` if this method should not return until a response is received; `False` otherwise. Returns: Message a Message containing possible additional data if the request was successful (or an empty Message if `wait` was `False`); `None` if the request was denied.

### is_active(self) | source code
Return true if this session is active (open). Returns: bool True if the session is still active (open); False if the session is closed

### is_authenticated(self) | source code
Return true if this session is active and authenticated. Returns: bool True if the session is still open and has been authenticated successfully; False if authentication failed and/or the session is closed.

### load_server_moduli(filename=None) Static Method | source code
(optional) Load a file of prime moduli for use in doing group-exchange key negotiation in server mode. It's a rather obscure option and can be safely ignored. In server mode, the remote client may request "group-exchange" key negotiation, which asks the server to send a random prime number that fits certain criteria. These primes are pretty difficult to compute, so they can't be generated on demand. But many systems contain a file of suitable primes (usually named something like `/etc/ssh/moduli`). If you call `load_server_moduli` and it returns `True`, then this file of primes has been loaded and we will support "group-exchange" in server mode. Otherwise server mode will just claim that it doesn't support that method of key negotiation. Parameters: `filename` (str) - optional path to the moduli file, if you happen to know that it's not in a standard location. Returns: bool True if a moduli file was successfully loaded; False otherwise. Note: This has no effect when used in client mode.

### open_channel(self, kind, dest_addr=None, src_addr=None) | source code
Request a new channel to the server. Channels are socket-like objects used for the actual transfer of data across the session. You may only request a channel after negotiating encryption (using connect or start_client) and authenticating. Parameters: `kind` (str) - the kind of channel requested (usually `"session"`, `"forwarded-tcpip"`, `"direct-tcpip"`, or `"x11"`) `dest_addr` ((str, int)) - the destination address of this port forwarding, if `kind` is `"forwarded-tcpip"` or `"direct-tcpip"` (ignored for other channel types) `src_addr` ((str, int)) - the source address of this port forwarding, if `kind` is `"forwarded-tcpip"`, `"direct-tcpip"`, or `"x11"` Returns: Channel a new Channel on success Raises: `SSHException` - if the request is rejected or the session ends prematurely

### open_forwarded_tcpip_channel(self, (src_addr, src_port), (dest_addr, dest_port)) | source code
Request a new channel back to the client, of type `"forwarded-tcpip"`. This is used after a client has requested port forwarding, for sending incoming connections back to the client. Parameters: `src_addr` - originator's address `src_port` - originator's port `dest_addr` - local (server) connected address `dest_port` - local (server) connected port

### open_session(self) | source code
Request a new channel to the server, of type `"session"`. This is just an alias for `open_channel('session')`. Returns: Channel a new Channel Raises: `SSHException` - if the request is rejected or the session ends prematurely

### open_sftp_client(self) | source code
Create an SFTP client channel from an open transport. On success, an SFTP session will be opened with the remote host, and a new SFTPClient object will be returned. Returns: SFTPClient a new SFTPClient object, referring to an sftp session (channel) across this transport

### open_x11_channel(self, src_addr=None) | source code
Request a new channel to the client, of type `"x11"`. This is just an alias for `open_channel('x11', src_addr=src_addr)`. Parameters: `src_addr` ((str, int)) - the source address of the x11 server (port is the x11 port, ie. 6010) Returns: Channel a new Channel Raises: `SSHException` - if the request is rejected or the session ends prematurely

### renegotiate_keys(self) | source code
Force this session to switch to new keys. Normally this is done automatically after the session hits a certain number of packets or bytes sent or received, but this method gives you the option of forcing new keys whenever you want. Negotiating new keys causes a pause in traffic both ways as the two sides swap keys and do computations. This method returns when the session has switched to new keys. Raises: `SSHException` - if the key renegotiation failed (which causes the session to end)

### request_port_forward(self, address, port, handler=None) | source code
Ask the server to forward TCP connections from a listening port on the server, across this SSH session. If a handler is given, that handler is called from a different thread whenever a forwarded connection arrives. The handler parameters are:
       handler(channel, (origin_addr, origin_port), (server_addr, server_port))
where `server_addr` and `server_port` are the address and port that the server was listening on. If no handler is set, the default behavior is to send new incoming forwarded connections into the accept queue, to be picked up via accept. Parameters: `address` (str) - the address to bind when forwarding `port` (int) - the port to forward, or 0 to ask the server to allocate any port `handler` (function(Channel, (str, int), (str, int))) - optional handler for incoming forwarded connections Returns: int the port # allocated by the server Raises: `SSHException` - if the server refused the TCP forward request

### run(self) | source code
Overrides: threading.Thread.run

### send_ignore(self, bytes=None) | source code
Send a junk packet across the encrypted link. This is sometimes used to add "noise" to a connection to confuse would-be attackers. It can also be used as a keep-alive for long lived connections traversing firewalls. Parameters: `bytes` (int) - the number of random bytes to send in the payload of the ignored packet -- defaults to a random number from 10 to 41.

### set_hexdump(self, hexdump) | source code
Turn on/off logging a hex dump of protocol traffic at DEBUG level in the logs. Normally you would want this off (which is the default), but if you are debugging something, it may be useful. Parameters: `hexdump` (bool) - `True` to log protocol traffix (in hex) to the log; `False` otherwise.

### set_keepalive(self, interval) | source code
Turn on/off keepalive packets (default is off). If this is set, after `interval` seconds without sending any data over the connection, a "keepalive" packet will be sent (and ignored by the remote host). This can be useful to keep connections alive over a NAT, for example. Parameters: `interval` (int) - seconds to wait before sending a keepalive packet (or 0 to disable keepalives).

### set_log_channel(self, name) | source code
Set the channel for this transport's logging. The default is `"paramiko.transport"` but it can be set to anything you want. (See the `logging` module for more info.) SSH Channels will log to a sub-channel of the one specified. Parameters: `name` (str) - new channel name for logging Since: 1.1

### set_subsystem_handler(self, name, handler, *larg, **kwarg) | source code
Set the handler class for a subsystem in server mode. If a request for this subsystem is made on an open ssh channel later, this handler will be constructed and called -- see SubsystemHandler for more detailed documentation. Any extra parameters (including keyword arguments) are saved and passed to the SubsystemHandler constructor later. Parameters: `name` (str) - name of the subsystem. `handler` (class) - subclass of SubsystemHandler that handles this subsystem.

### start_client(self, event=None) | source code
Negotiate a new SSH2 session as a client. This is the first step after creating a new Transport. A separate thread is created for protocol negotiation. If an event is passed in, this method returns immediately. When negotiation is done (successful or not), the given `Event` will be triggered. On failure, is_active will return `False`. (Since 1.4) If `event` is `None`, this method will not return until negotation is done. On success, the method returns normally. Otherwise an SSHException is raised. After a successful negotiation, you will usually want to authenticate, calling auth_password or auth_publickey. Parameters: `event` (threading.Event) - an event to trigger when negotiation is complete (optional) Raises: `SSHException` - if negotiation fails (and no `event` was passed in) Notes: connect is a simpler method for connecting as a client. After calling this method (or start_server or connect), you should no longer directly read from or write to the original socket object.

### start_server(self, event=None, server=None) | source code
Negotiate a new SSH2 session as a server. This is the first step after creating a new Transport and setting up your server host key(s). A separate thread is created for protocol negotiation. If an event is passed in, this method returns immediately. When negotiation is done (successful or not), the given `Event` will be triggered. On failure, is_active will return `False`. (Since 1.4) If `event` is `None`, this method will not return until negotation is done. On success, the method returns normally. Otherwise an SSHException is raised. After a successful negotiation, the client will need to authenticate. Override the methods get_allowed_auths, check_auth_none, check_auth_password, and check_auth_publickey in the given `server` object to control the authentication process. After a successful authentication, the client should request to open a channel. Override check_channel_request in the given `server` object to allow channels to be opened. Parameters: `event` (threading.Event) - an event to trigger when negotiation is complete. `server` (server.ServerInterface) - an object used to perform authentication and create Channels. Raises: `SSHException` - if negotiation fails (and no `event` was passed in) Note: After calling this method (or start_client or connect), you should no longer directly read from or write to the original socket object.

### use_compression(self, compress=True) | source code
Turn on/off compression. This will only have an affect before starting the transport (ie before calling connect, etc). By default, compression is off since it negatively affects interactive sessions. Parameters: `compress` (bool) - `True` to ask the remote client/server to compress traffic; `False` to refuse compression Since: 1.5.2