Package paramiko :: Module transport :: Class BaseTransport
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Class 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.
str __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.
  close(self)
Close this session, and any open channels that are tied to it.
  connect(self, hostkey, username, password, pkey)
Negotiate an SSH2 session, and optionally verify the server's host key and authenticate using a password or private key.
Exception get_exception(self)
Return any exception that happened during the last server request.
bool get_hexdump(self)
Return True if the transport is currently logging hex dumps of protocol traffic.
str get_log_channel(self)
Return the channel name used for this transport's logging.
PKey get_remote_server_key(self)
Return the host key of the server (in client mode).
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.
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, dest_addr, src_addr)
Request a new channel to the server.
Channel open_session(self)
Request a new channel to the server, of type "session".
SFTPClient open_sftp_client(self)
Create an SFTP client channel from an open transport.
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_hexdump(self, hexdump)
Turn on/off logging a hex dump of protocol traffic at DEBUG level in the logs.
  set_keepalive(self, interval)
Turn on/off keepalive packets (default is off).
  set_log_channel(self, name)
Set the channel for this transport's logging.
  set_subsystem_handler(self, name, handler, *larg, **kwarg)
Set the handler class for a subsystem in server mode.
  start_client(self, event)
Negotiate a new SSH2 session as a client.
  start_server(self, event, server)
Negotiate a new SSH2 session as a server.
  stop_thread(self)
  _activate_inbound(self)
switch on newly negotiated encryption parameters for inbound traffic
  _activate_outbound(self)
switch on newly negotiated encryption parameters for outbound traffic
  _check_banner(self)
  _compute_key(self, id, nbytes)
id is 'A' - 'F' for the various keys used by ssh
  _expect_packet(self, type)
used by a kex object to register the next packet type it expects to see
  _get_cipher(self, name, key, iv)
  _get_modulus_pack(self)
used by KexGex to find primes for group exchange
  _get_subsystem_handler(self, name)
  _log(self, level, msg)
  _negotiate_keys(self, m)
  _parse_channel_open(self, m)
  _parse_channel_open_failure(self, m)
  _parse_channel_open_success(self, m)
  _parse_debug(self, m)
  _parse_disconnect(self, m)
  _parse_global_request(self, m)
  _parse_kex_init(self, m)
  _parse_newkeys(self, m)
  _parse_request_failure(self, m)
  _parse_request_success(self, m)
  _run(self)
  _send_kex_init(self)
announce to the other side that we'd like to negotiate keys, and what kind of key negotiation we support.
  _send_message(self, data)
  _send_user_message(self, data)
send a message, but block if we're in key negotiation.
  _set_K_H(self, k, h)
used by a kex object to set the K (root key) and H (exchange hash)
  _unlink_channel(self, chanid)
used by a Channel to remove itself from the active channel list
  _verify_key(self, host_key, sig)
    Inherited from Thread
  getName(self)
  isAlive(self)
  isDaemon(self)
  join(self, timeout)
  run(self)
  setDaemon(self, daemonic)
  setName(self, name)
  start(self)
  _set_daemon(self)
    Inherited from _Verbose
  _note(self, format, *args)
    Inherited from object
  __delattr__(...)
x.__delattr__('name') <==> del x.name
  __getattribute__(...)
x.__getattribute__('name') <==> x.name
  __hash__(x)
x.__hash__() <==> hash(x)
  __reduce__(...)
helper for pickle
  __reduce_ex__(...)
helper for pickle
  __setattr__(...)
x.__setattr__('name', value) <==> x.name = value
  __str__(x)
x.__str__() <==> str(x)
    Inherited from type
  __new__(T, S, ...)
T.__new__(S, ...) -> a new object with type S, a subtype of T

Class Variable Summary
dict _channel_handler_table = {96: <unbound method Channel._h...
dict _cipher_info = {'blowfish-cbc': {'block-size': 8, 'key-s...
str _CLIENT_ID = 'paramiko_1.3.1'
dict _handler_table = {80: <function _parse_global_request at...
dict _kex_info = {'diffie-hellman-group1-sha1': <class 'param...
dict _key_info = {'ssh-dss': <class 'paramiko.dsskey.DSSKey'>...
dict _mac_info = {'hmac-sha1': {'class': <module 'Crypto.Hash...
NoneType _modulus_pack = None                                                                  
tuple _preferred_ciphers = ('aes128-cbc', 'blowfish-cbc', 'aes...
tuple _preferred_kex = ('diffie-hellman-group1-sha1', 'diffie-...
tuple _preferred_keys = ('ssh-rsa', 'ssh-dss')
tuple _preferred_macs = ('hmac-sha1', 'hmac-md5', 'hmac-sha1-9...
str _PROTO_ID = '2.0'
    Inherited from Thread
bool _Thread__initialized = False

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(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 - 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:
str
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)

close(self)

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

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. 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 - the host key expected from the server, or None if you don't want to do host key verification.
           (type=PKey)
username - the username to authenticate as.
           (type=str)
password - a password to use for authentication, if you want to use password authentication; otherwise None.
           (type=str)
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_exception(self)

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:
an exception, or None if there is no stored exception.
           (type=Exception)

Since: 1.1

get_hexdump(self)

Return True if the transport is currently logging hex dumps of protocol traffic.
Returns:
True if hex dumps are being logged
           (type=bool)

Since: 1.4

get_log_channel(self)

Return the channel name used for this transport's logging.
Returns:
channel name.
           (type=str)

Since: 1.2

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_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.
Returns:
an object that can be used to change the preferred algorithms for encryption, digest (hash), public key, and key exchange.
           (type=SecurityOptions)

Since: ivysaur

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=str)
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, dest_addr=None, src_addr=None)

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", "forwarded-tcpip" or "direct-tcpip").
           (type=str)
dest_addr - the destination address of this port forwarding, if kind is "forwarded-tcpip" or "direct-tcpip" (ignored for other channel types).
           (type=(str, int))
src_addr - the source address of this port forwarding, if kind is "forwarded-tcpip" or "direct-tcpip".
           (type=(str, int))
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)

open_sftp_client(self)

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:
a new SFTPClient object, referring to an sftp session (channel) across this transport
           (type=SFTPClient)

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_hexdump(self, hexdump)

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 - True to log protocol traffix (in hex) to the log; False otherwise.
           (type=bool)

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

set_log_channel(self, name)

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 - new channel name for logging.
           (type=str)

Since: 1.1

set_subsystem_handler(self, name, handler, *larg, **kwarg)

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 - name of the subsystem.
           (type=str)
handler - subclass of SubsystemHandler that handles this subsystem.
           (type=class)

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, server=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 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 - an event to trigger when negotiation is complete.
           (type=threading.Event)
server - an object used to perform authentication and create Channels.
           (type=server.ServerInterface)

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

_activate_inbound(self)

switch on newly negotiated encryption parameters for inbound traffic

_activate_outbound(self)

switch on newly negotiated encryption parameters for outbound traffic

_compute_key(self, id, nbytes)

id is 'A' - 'F' for the various keys used by ssh

_expect_packet(self, type)

used by a kex object to register the next packet type it expects to see

_get_modulus_pack(self)

used by KexGex to find primes for group exchange

_send_kex_init(self)

announce to the other side that we'd like to negotiate keys, and what kind of key negotiation we support.

_send_user_message(self, data)

send a message, but block if we're in key negotiation. this is used for user-initiated requests.

_set_K_H(self, k, h)

used by a kex object to set the K (root key) and H (exchange hash)

_unlink_channel(self, chanid)

used by a Channel to remove itself from the active channel list

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=str)
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

_channel_handler_table

Type:
dict
Value:
{93: <unbound method Channel._window_adjust>,
 94: <unbound method Channel._feed>,
 95: <unbound method Channel._feed_extended>,
 96: <unbound method Channel._handle_eof>,
 97: <unbound method Channel._handle_close>,
 98: <unbound method Channel._handle_request>,
 99: <unbound method Channel._request_success>,
 100: <unbound method Channel._request_failed>}                        

_cipher_info

Type:
dict
Value:
{'3des-cbc': {'block-size': 8,
              'class': <module 'Crypto.Cipher.DES3' from '/usr/lib/pyt\
hon2.3/site-packages/Crypto/Cipher/DES3.so'>,
              'key-size': 24,
              'mode': 2},
 'aes128-cbc': {'block-size': 16,
                'class': <module 'Crypto.Cipher.AES' from '/usr/lib/py\
thon2.3/site-packages/Crypto/Cipher/AES.so'>,
...                                                                    

_CLIENT_ID

Type:
str
Value:
'paramiko_1.3.1'                                                       

_handler_table

Type:
dict
Value:
{20: <function _negotiate_keys at 0xb7b7809c>,
 21: <function _parse_newkeys at 0xb7b781ec>,
 80: <function _parse_global_request at 0xb7b7825c>,
 81: <function _parse_request_success at 0xb7b78294>,
 82: <function _parse_request_failure at 0xb7b782cc>,
 90: <function _parse_channel_open at 0xb7b78374>,
 91: <function _parse_channel_open_success at 0xb7b78304>,
 92: <function _parse_channel_open_failure at 0xb7b7833c>}             

_kex_info

Type:
dict
Value:
{'diffie-hellman-group-exchange-sha1': <class 'paramiko.kex_gex.KexGex\
'>,
 'diffie-hellman-group1-sha1': <class 'paramiko.kex_group1.KexGroup1'>\
}                                                                      

_key_info

Type:
dict
Value:
{'ssh-dss': <class 'paramiko.dsskey.DSSKey'>,
 'ssh-rsa': <class 'paramiko.rsakey.RSAKey'>}                          

_mac_info

Type:
dict
Value:
{'hmac-md5': {'class': <module 'Crypto.Hash.MD5' from '/usr/lib/python\
2.3/site-packages/Crypto/Hash/MD5.pyc'>,
              'size': 16},
 'hmac-md5-96': {'class': <module 'Crypto.Hash.MD5' from '/usr/lib/pyt\
hon2.3/site-packages/Crypto/Hash/MD5.pyc'>,
                 'size': 12},
 'hmac-sha1': {'class': <module 'Crypto.Hash.SHA' from '/usr/lib/pytho\
n2.3/site-packages/Crypto/Hash/SHA.pyc'>,
...                                                                    

_modulus_pack

Type:
NoneType
Value:
None                                                                  

_preferred_ciphers

Type:
tuple
Value:
('aes128-cbc', 'blowfish-cbc', 'aes256-cbc', '3des-cbc')               

_preferred_kex

Type:
tuple
Value:
('diffie-hellman-group1-sha1', 'diffie-hellman-group-exchange-sha1')   

_preferred_keys

Type:
tuple
Value:
('ssh-rsa', 'ssh-dss')                                                 

_preferred_macs

Type:
tuple
Value:
('hmac-sha1', 'hmac-md5', 'hmac-sha1-96', 'hmac-md5-96')               

_PROTO_ID

Type:
str
Value:
'2.0'                                                                  

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