Package paramiko :: Module transport :: Class BaseTransport
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Type BaseTransport

object --+        
         |        
  _Verbose --+    
             |    
        Thread --+
                 |
                BaseTransport

Known Subclasses:
Transport

Handles protocol negotiation, key exchange, encryption, and the creation of channels across an SSH session. Basically everything but authentication is done here.
Method Summary
  __init__(self, sock)
Create a new SSH session over an existing socket, or socket-like object.
string __repr__(self)
Returns a string representation of this object, for debugging.
  accept(self, timeout)
  add_server_key(self, key)
Add a host key to the list of keys used for server mode.
Channel check_channel_request(self, kind, chanid)
(subclass override) Determine if a channel request of a given type will be granted, and return a suitable Channel object.
bool check_global_request(self, kind, msg)
(subclass override) Handle a global request of the given kind.
  close(self)
Close this session, and any open channels that are tied to it.
  connect(self, hostkeytype, hostkey, username, password, pkey)
Negotiate an SSH2 session, and optionally verify the server's host key and authenticate using a password or private key.
PKey get_remote_server_key(self)
Return the host key of the server (in client mode).
PKey get_server_key(self)
Return the active host key, in server mode.
Message global_request(self, kind, data, wait)
Make a global request to the remote host.
bool is_active(self)
Return true if this session is active (open).
bool load_server_moduli(filename)
(optional) Load a file of prime moduli for use in doing group-exchange key negotiation in server mode. (Static method)
Channel open_channel(self, kind)
Request a new channel to the server.
Channel open_session(self)
Request a new channel to the server, of type "session".
bool renegotiate_keys(self)
Force this session to switch to new keys.
  send_ignore(self, bytes)
Send a junk packet across the encrypted link.
  set_keepalive(self, interval)
Turn on/off keepalive packets (default is off).
  start_client(self, event)
Negotiate a new SSH2 session as a client.
  start_server(self, event)
Negotiate a new SSH2 session as a server.
    Inherited from Thread
  getName(self)
  isAlive(self)
  isDaemon(self)
  join(self, timeout)
  run(self)
  setDaemon(self, daemonic)
  setName(self, name)
  start(self)
    Inherited from object
  __delattr__(...)
x.__delattr__('name') <==> del x.name
  __getattribute__(...)
x.__getattribute__('name') <==> x.name
  __hash__(x)
x.__hash__() <==> hash(x)
  __new__(T, S, ...)
T.__new__(S, ...) -> a new object with type S, a subtype of T
  __reduce__(...)
helper for pickle
  __reduce_ex__(...)
helper for pickle
  __setattr__(...)
x.__setattr__('name', value) <==> x.name = value
  __str__(x)
x.__str__() <==> str(x)

Class Variable Summary
int OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED = 1                                                                     
int OPEN_FAILED_CONNECT_FAILED = 2                                                                     
int OPEN_FAILED_RESOURCE_SHORTAGE = 4                                                                     
int OPEN_FAILED_UNKNOWN_CHANNEL_TYPE = 3                                                                     
list preferred_ciphers = ['aes128-cbc', 'blowfish-cbc', 'aes2...
list preferred_kex = ['diffie-hellman-group1-sha1', 'diffie-h...
list preferred_keys = ['ssh-rsa', 'ssh-dss']
list preferred_macs = ['hmac-sha1', 'hmac-md5', 'hmac-sha1-96...
int REKEY_BYTES = 1073741824                                                            
int REKEY_PACKETS = 1073741824                                                            

Instance Method Details

__init__(self, sock)
(Constructor)

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(string): Writes from 1 to len(string) 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.
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 - a socket or socket-like object to create the session over.
           (type=socket)
Overrides:
threading.Thread.__init__

__repr__(self)
(Representation operator)

Returns a string representation of this object, for debugging.
Returns:
string
Overrides:
threading.Thread.__repr__

add_server_key(self, key)

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.
Parameters:
key - the host key to add, usually an RSAKey or DSSKey.
           (type=PKey)

check_channel_request(self, kind, chanid)

(subclass override) Determine if a channel request of a given type will be granted, and return a suitable Channel object. This method is called in server mode when the client requests a channel, after authentication is complete.

In server mode, you will generally want to subclass Channel to override some of the methods for handling client requests (such as connecting to a subsystem or opening a shell) to determine what you want to allow or disallow. For this reason, check_channel_request must return a new object of that type. The chanid parameter is passed so that you can use it in Channel's constructor.

The default implementation always returns None, rejecting any channel requests. A useful server must override this method.
Parameters:
kind - the kind of channel the client would like to open (usually "session").
           (type=string)
chanid - ID of the channel, required to create a new Channel object.
           (type=int)
Returns:
a new Channel object (or subclass thereof), or None to refuse the request.
           (type=Channel)

check_global_request(self, kind, msg)

(subclass override) 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.
Parameters:
kind - the kind of global request being made.
           (type=string)
msg - any extra arguments to the request.
           (type=Message)
Returns:
True or a tuple of data if the request was granted; False otherwise.
           (type=bool)

close(self)

Close this session, and any open channels that are tied to it.

connect(self, hostkeytype=None, 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. 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:
hostkeytype - the type of host key expected from the server (usually "ssh-rsa" or "ssh-dss"), or None if you don't want to do host key verification.
           (type=string)
hostkey - the host key expected from the server, or None if you don't want to do host key verification.
           (type=string)
username - the username to authenticate as.
           (type=string)
password - a password to use for authentication, if you want to use password authentication; otherwise None.
           (type=string)
pkey - a private key to use for authentication, if you want to use private key authentication; otherwise None.
           (type=PKey)
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.

Since: doduo

get_remote_server_key(self)

Return the host key of the server (in client mode).
Returns:
public key of the remote server.
           (type=PKey)
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_server_key(self)

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:
host key of the type negotiated by the client, or None.
           (type=PKey)

global_request(self, kind, data=None, wait=True)

Make a global request to the remote host. These are normally extensions to the SSH2 protocol.
Parameters:
kind - name of the request.
           (type=string)
data - an optional tuple containing additional data to attach to the request.
           (type=tuple)
wait - True if this method should not return until a response is received; False otherwise.
           (type=bool)
Returns:
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.
           (type=Message)

Since: fearow

is_active(self)

Return true if this session is active (open).
Returns:
True if the session is still active (open); False if the session is closed.
           (type=bool)

open_channel(self, kind)

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 - the kind of channel requested (usually "session").
           (type=string)
Returns:
a new Channel on success, or None if the request is rejected or the session ends prematurely.
           (type=Channel)

open_session(self)

Request a new channel to the server, of type "session". This is just an alias for open_channel('session').
Returns:
a new Channel on success, or None if the request is rejected or the session ends prematurely.
           (type=Channel)

renegotiate_keys(self)

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, or the session has died mid-negotiation.
Returns:
True if the renegotiation was successful, and the link is using new keys; False if the session dropped during renegotiation.
           (type=bool)

send_ignore(self, bytes=None)

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 - the number of random bytes to send in the payload of the ignored packet -- defaults to a random number from 10 to 41.
           (type=int)

Since: fearow

set_keepalive(self, interval)

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 - seconds to wait before sending a keepalive packet (or 0 to disable keepalives).
           (type=int)

Since: fearow

start_client(self, event=None)

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, so this method returns immediately.

When negotiation is done (successful or not), the given Event will be triggered. On failure, is_active will return False.

After a successful negotiation, you will usually want to authenticate, calling auth_password or auth_publickey.
Parameters:
event - an event to trigger when negotiation is complete.
           (type=threading.Event)

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)

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, so this method returns immediately.

When negotiation is done (successful or not), the given Event will be triggered. On failure, is_active will return False.

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 to control the authentication process.

After a successful authentication, the client should request to open a channel. Override check_channel_request to allow channels to be opened.
Parameters:
event - an event to trigger when negotiation is complete.
           (type=threading.Event)

Note: After calling this method (or start_client or connect), you should no longer directly read from or write to the original socket object.


Static Method Details

load_server_moduli(filename=None)

(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 - optional path to the moduli file, if you happen to know that it's not in a standard location.
           (type=string)
Returns:
True if a moduli file was successfully loaded; False otherwise.
           (type=bool)

Note: This has no effect when used in client mode.

Since: doduo


Class Variable Details

OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED

Type:
int
Value:
1                                                                     

OPEN_FAILED_CONNECT_FAILED

Type:
int
Value:
2                                                                     

OPEN_FAILED_RESOURCE_SHORTAGE

Type:
int
Value:
4                                                                     

OPEN_FAILED_UNKNOWN_CHANNEL_TYPE

Type:
int
Value:
3                                                                     

preferred_ciphers

Type:
list
Value:
['aes128-cbc', 'blowfish-cbc', 'aes256-cbc', '3des-cbc']               

preferred_kex

Type:
list
Value:
['diffie-hellman-group1-sha1', 'diffie-hellman-group-exchange-sha1']   

preferred_keys

Type:
list
Value:
['ssh-rsa', 'ssh-dss']                                                 

preferred_macs

Type:
list
Value:
['hmac-sha1', 'hmac-md5', 'hmac-sha1-96', 'hmac-md5-96']               

REKEY_BYTES

Type:
int
Value:
1073741824                                                            

REKEY_PACKETS

Type:
int
Value:
1073741824                                                            

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