# Copyright (C) 2003-2007 Robey Pointer <robeypointer@gmail.com>
#
# This file is part of paramiko.
#
# Paramiko is free software; you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation; either version 2.1 of the License, or (at your option)
# any later version.
#
# Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with Paramiko; if not, write to the Free Software Foundation, Inc.,
# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
"""
L{Transport} handles the core SSH2 protocol.
"""
import os
import socket
import string
import struct
import sys
import threading
import time
import weakref
from paramiko import util
from paramiko.auth_handler import AuthHandler
from paramiko.channel import Channel
from paramiko.common import *
from paramiko.compress import ZlibCompressor, ZlibDecompressor
from paramiko.dsskey import DSSKey
from paramiko.kex_gex import KexGex
from paramiko.kex_group1 import KexGroup1
from paramiko.message import Message
from paramiko.packet import Packetizer, NeedRekeyException
from paramiko.primes import ModulusPack
from paramiko.rsakey import RSAKey
from paramiko.server import ServerInterface
from paramiko.sftp_client import SFTPClient
from paramiko.ssh_exception import SSHException, BadAuthenticationType, ChannelException
from Crypto import Random
from Crypto.Cipher import Blowfish, AES, DES3, ARC4
from Crypto.Hash import SHA, MD5
try:
from Crypto.Util import Counter
except ImportError:
from paramiko.util import Counter
# for thread cleanup
_active_threads = []
def _join_lingering_threads():
for thr in _active_threads:
thr.stop_thread()
import atexit
atexit.register(_join_lingering_threads)
class SecurityOptions (object):
"""
Simple object containing the security preferences of an ssh transport.
These are tuples of acceptable ciphers, digests, key types, and key
exchange algorithms, listed in order of preference.
Changing the contents and/or order of these fields affects the underlying
L{Transport} (but only if you change them before starting the session).
If you try to add an algorithm that paramiko doesn't recognize,
C{ValueError} will be raised. If you try to assign something besides a
tuple to one of the fields, C{TypeError} will be raised.
"""
__slots__ = [ 'ciphers', 'digests', 'key_types', 'kex', 'compression', '_transport' ]
def __init__(self, transport):
self._transport = transport
def __repr__(self):
"""
Returns a string representation of this object, for debugging.
@rtype: str
"""
return '<paramiko.SecurityOptions for %s>' % repr(self._transport)
def _get_ciphers(self):
return self._transport._preferred_ciphers
def _get_digests(self):
return self._transport._preferred_macs
def _get_key_types(self):
return self._transport._preferred_keys
def _get_kex(self):
return self._transport._preferred_kex
def _get_compression(self):
return self._transport._preferred_compression
def _set(self, name, orig, x):
if type(x) is list:
x = tuple(x)
if type(x) is not tuple:
raise TypeError('expected tuple or list')
possible = getattr(self._transport, orig).keys()
forbidden = filter(lambda n: n not in possible, x)
if len(forbidden) > 0:
raise ValueError('unknown cipher')
setattr(self._transport, name, x)
def _set_ciphers(self, x):
self._set('_preferred_ciphers', '_cipher_info', x)
def _set_digests(self, x):
self._set('_preferred_macs', '_mac_info', x)
def _set_key_types(self, x):
self._set('_preferred_keys', '_key_info', x)
def _set_kex(self, x):
self._set('_preferred_kex', '_kex_info', x)
def _set_compression(self, x):
self._set('_preferred_compression', '_compression_info', x)
ciphers = property(_get_ciphers, _set_ciphers, None,
"Symmetric encryption ciphers")
digests = property(_get_digests, _set_digests, None,
"Digest (one-way hash) algorithms")
key_types = property(_get_key_types, _set_key_types, None,
"Public-key algorithms")
kex = property(_get_kex, _set_kex, None, "Key exchange algorithms")
compression = property(_get_compression, _set_compression, None,
"Compression algorithms")
class ChannelMap (object):
def __init__(self):
# (id -> Channel)
self._map = weakref.WeakValueDictionary()
self._lock = threading.Lock()
def put(self, chanid, chan):
self._lock.acquire()
try:
self._map[chanid] = chan
finally:
self._lock.release()
def get(self, chanid):
self._lock.acquire()
try:
return self._map.get(chanid, None)
finally:
self._lock.release()
def delete(self, chanid):
self._lock.acquire()
try:
try:
del self._map[chanid]
except KeyError:
pass
finally:
self._lock.release()
def values(self):
self._lock.acquire()
try:
return self._map.values()
finally:
self._lock.release()
def __len__(self):
self._lock.acquire()
try:
return len(self._map)
finally:
self._lock.release()
class Transport (threading.Thread):
"""
An SSH Transport attaches to a stream (usually a socket), negotiates an
encrypted session, authenticates, and then creates stream tunnels, called
L{Channel}s, across the session. Multiple channels can be multiplexed
across a single session (and often are, in the case of port forwardings).
"""
_PROTO_ID = '2.0'
_CLIENT_ID = 'paramiko_1.7.7.1'
_preferred_ciphers = ( 'aes128-ctr', 'aes256-ctr', 'aes128-cbc', 'blowfish-cbc', 'aes256-cbc', '3des-cbc',
'arcfour128', 'arcfour256' )
_preferred_macs = ( 'hmac-sha1', 'hmac-md5', 'hmac-sha1-96', 'hmac-md5-96' )
_preferred_keys = ( 'ssh-rsa', 'ssh-dss' )
_preferred_kex = ( 'diffie-hellman-group1-sha1', 'diffie-hellman-group-exchange-sha1' )
_preferred_compression = ( 'none', )
_cipher_info = {
'aes128-ctr': { 'class': AES, 'mode': AES.MODE_CTR, 'block-size': 16, 'key-size': 16 },
'aes256-ctr': { 'class': AES, 'mode': AES.MODE_CTR, 'block-size': 16, 'key-size': 32 },
'blowfish-cbc': { 'class': Blowfish, 'mode': Blowfish.MODE_CBC, 'block-size': 8, 'key-size': 16 },
'aes128-cbc': { 'class': AES, 'mode': AES.MODE_CBC, 'block-size': 16, 'key-size': 16 },
'aes256-cbc': { 'class': AES, 'mode': AES.MODE_CBC, 'block-size': 16, 'key-size': 32 },
'3des-cbc': { 'class': DES3, 'mode': DES3.MODE_CBC, 'block-size': 8, 'key-size': 24 },
'arcfour128': { 'class': ARC4, 'mode': None, 'block-size': 8, 'key-size': 16 },
'arcfour256': { 'class': ARC4, 'mode': None, 'block-size': 8, 'key-size': 32 },
}
_mac_info = {
'hmac-sha1': { 'class': SHA, 'size': 20 },
'hmac-sha1-96': { 'class': SHA, 'size': 12 },
'hmac-md5': { 'class': MD5, 'size': 16 },
'hmac-md5-96': { 'class': MD5, 'size': 12 },
}
_key_info = {
'ssh-rsa': RSAKey,
'ssh-dss': DSSKey,
}
_kex_info = {
'diffie-hellman-group1-sha1': KexGroup1,
'diffie-hellman-group-exchange-sha1': KexGex,
}
_compression_info = {
# zlib@openssh.com is just zlib, but only turned on after a successful
# authentication. openssh servers may only offer this type because
# they've had troubles with security holes in zlib in the past.
'zlib@openssh.com': ( ZlibCompressor, ZlibDecompressor ),
'zlib': ( ZlibCompressor, ZlibDecompressor ),
'none': ( None, None ),
}
_modulus_pack = None
def __init__(self, sock):
"""
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 L{connect} or L{start_client} to begin a client
session, or L{start_server} to begin a server session.
If the object is not actually a socket, it must have the following
methods:
- C{send(str)}: Writes from 1 to C{len(str)} bytes, and
returns an int representing the number of bytes written. Returns
0 or raises C{EOFError} if the stream has been closed.
- C{recv(int)}: Reads from 1 to C{int} bytes and returns them as a
string. Returns 0 or raises C{EOFError} if the stream has been
closed.
- C{close()}: Closes the socket.
- C{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 C{sock} argument. (A host string is a hostname with an
optional port (separated by C{":"}) which will be converted into a
tuple of C{(hostname, port)}.) A socket will be connected to this
address and used for communication. Exceptions from the C{socket} call
may be thrown in this case.
@param sock: a socket or socket-like object to create the session over.
@type sock: socket
"""
if isinstance(sock, (str, unicode)):
# convert "host:port" into (host, port)
hl = sock.split(':', 1)
if len(hl) == 1:
sock = (hl[0], 22)
else:
sock = (hl[0], int(hl[1]))
if type(sock) is tuple:
# connect to the given (host, port)
hostname, port = sock
reason = 'No suitable address family'
for (family, socktype, proto, canonname, sockaddr) in socket.getaddrinfo(hostname, port, socket.AF_UNSPEC, socket.SOCK_STREAM):
if socktype == socket.SOCK_STREAM:
af = family
addr = sockaddr
sock = socket.socket(af, socket.SOCK_STREAM)
try:
sock.connect((hostname, port))
except socket.error, e:
reason = str(e)
else:
break
else:
raise SSHException(
'Unable to connect to %s: %s' % (hostname, reason))
# okay, normal socket-ish flow here...
threading.Thread.__init__(self)
self.setDaemon(True)
self.rng = rng
self.sock = sock
# Python < 2.3 doesn't have the settimeout method - RogerB
try:
# we set the timeout so we can check self.active periodically to
# see if we should bail. socket.timeout exception is never
# propagated.
self.sock.settimeout(0.1)
except AttributeError:
pass
# negotiated crypto parameters
self.packetizer = Packetizer(sock)
self.local_version = 'SSH-' + self._PROTO_ID + '-' + self._CLIENT_ID
self.remote_version = ''
self.local_cipher = self.remote_cipher = ''
self.local_kex_init = self.remote_kex_init = None
self.local_mac = self.remote_mac = None
self.local_compression = self.remote_compression = None
self.session_id = None
self.host_key_type = None
self.host_key = None
# state used during negotiation
self.kex_engine = None
self.H = None
self.K = None
self.active = False
self.initial_kex_done = False
self.in_kex = False
self.authenticated = False
self._expected_packet = tuple()
self.lock = threading.Lock() # synchronization (always higher level than write_lock)
# tracking open channels
self._channels = ChannelMap()
self.channel_events = { } # (id -> Event)
self.channels_seen = { } # (id -> True)
self._channel_counter = 1
self.window_size = 65536
self.max_packet_size = 34816
self._x11_handler = None
self._tcp_handler = None
self.saved_exception = None
self.clear_to_send = threading.Event()
self.clear_to_send_lock = threading.Lock()
self.clear_to_send_timeout = 30.0
self.log_name = 'paramiko.transport'
self.logger = util.get_logger(self.log_name)
self.packetizer.set_log(self.logger)
self.auth_handler = None
self.global_response = None # response Message from an arbitrary global request
self.completion_event = None # user-defined event callbacks
self.banner_timeout = 15 # how long (seconds) to wait for the SSH banner
# server mode:
self.server_mode = False
self.server_object = None
self.server_key_dict = { }
self.server_accepts = [ ]
self.server_accept_cv = threading.Condition(self.lock)
self.subsystem_table = { }
def __repr__(self):
"""
Returns a string representation of this object, for debugging.
@rtype: str
"""
out = '<paramiko.Transport at %s' % hex(long(id(self)) & 0xffffffffL)
if not self.active:
out += ' (unconnected)'
else:
if self.local_cipher != '':
out += ' (cipher %s, %d bits)' % (self.local_cipher,
self._cipher_info[self.local_cipher]['key-size'] * 8)
if self.is_authenticated():
out += ' (active; %d open channel(s))' % len(self._channels)
elif self.initial_kex_done:
out += ' (connected; awaiting auth)'
else:
out += ' (connecting)'
out += '>'
return out
def atfork(self):
"""
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
"""
self.sock.close()
self.close()
def get_security_options(self):
"""
Return a L{SecurityOptions} object which can be used to tweak the
encryption algorithms this transport will permit, and the order of
preference for them.
@return: an object that can be used to change the preferred algorithms
for encryption, digest (hash), public key, and key exchange.
@rtype: L{SecurityOptions}
"""
return SecurityOptions(self)
def start_client(self, event=None):
"""
Negotiate a new SSH2 session as a client. This is the first step after
creating a new L{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 C{Event} will
be triggered. On failure, L{is_active} will return C{False}.
(Since 1.4) If C{event} is C{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 L{auth_password <Transport.auth_password>} or
L{auth_publickey <Transport.auth_publickey>}.
@note: L{connect} is a simpler method for connecting as a client.
@note: After calling this method (or L{start_server} or L{connect}),
you should no longer directly read from or write to the original
socket object.
@param event: an event to trigger when negotiation is complete
(optional)
@type event: threading.Event
@raise SSHException: if negotiation fails (and no C{event} was passed
in)
"""
self.active = True
if event is not None:
# async, return immediately and let the app poll for completion
self.completion_event = event
self.start()
return
# synchronous, wait for a result
self.completion_event = event = threading.Event()
self.start()
Random.atfork()
while True:
event.wait(0.1)
if not self.active:
e = self.get_exception()
if e is not None:
raise e
raise SSHException('Negotiation failed.')
if event.isSet():
break
def start_server(self, event=None, server=None):
"""
Negotiate a new SSH2 session as a server. This is the first step after
creating a new L{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 C{Event} will
be triggered. On failure, L{is_active} will return C{False}.
(Since 1.4) If C{event} is C{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
L{get_allowed_auths <ServerInterface.get_allowed_auths>},
L{check_auth_none <ServerInterface.check_auth_none>},
L{check_auth_password <ServerInterface.check_auth_password>}, and
L{check_auth_publickey <ServerInterface.check_auth_publickey>} in the
given C{server} object to control the authentication process.
After a successful authentication, the client should request to open
a channel. Override
L{check_channel_request <ServerInterface.check_channel_request>} in the
given C{server} object to allow channels to be opened.
@note: After calling this method (or L{start_client} or L{connect}),
you should no longer directly read from or write to the original
socket object.
@param event: an event to trigger when negotiation is complete.
@type event: threading.Event
@param server: an object used to perform authentication and create
L{Channel}s.
@type server: L{server.ServerInterface}
@raise SSHException: if negotiation fails (and no C{event} was passed
in)
"""
if server is None:
server = ServerInterface()
self.server_mode = True
self.server_object = server
self.active = True
if event is not None:
# async, return immediately and let the app poll for completion
self.completion_event = event
self.start()
return
# synchronous, wait for a result
self.completion_event = event = threading.Event()
self.start()
while True:
event.wait(0.1)
if not self.active:
e = self.get_exception()
if e is not None:
raise e
raise SSHException('Negotiation failed.')
if event.isSet():
break
def 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. Only one key of each type (RSA or
DSS) is kept.
@param key: the host key to add, usually an L{RSAKey <rsakey.RSAKey>} or
L{DSSKey <dsskey.DSSKey>}.
@type key: L{PKey <pkey.PKey>}
"""
self.server_key_dict[key.get_name()] = key
def 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 L{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, C{None} is returned. In client mode, the behavior is undefined.
@return: host key of the type negotiated by the client, or C{None}.
@rtype: L{PKey <pkey.PKey>}
"""
try:
return self.server_key_dict[self.host_key_type]
except KeyError:
pass
return None
def load_server_moduli(filename=None):
"""
I{(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 C{/etc/ssh/moduli}).
If you call C{load_server_moduli} and it returns C{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.
@param filename: optional path to the moduli file, if you happen to
know that it's not in a standard location.
@type filename: str
@return: True if a moduli file was successfully loaded; False
otherwise.
@rtype: bool
@note: This has no effect when used in client mode.
"""
Transport._modulus_pack = ModulusPack(rng)
# places to look for the openssh "moduli" file
file_list = [ '/etc/ssh/moduli', '/usr/local/etc/moduli' ]
if filename is not None:
file_list.insert(0, filename)
for fn in file_list:
try:
Transport._modulus_pack.read_file(fn)
return True
except IOError:
pass
# none succeeded
Transport._modulus_pack = None
return False
load_server_moduli = staticmethod(load_server_moduli)
def close(self):
"""
Close this session, and any open channels that are tied to it.
"""
if not self.active:
return
self.active = False
self.packetizer.close()
self.join()
for chan in self._channels.values():
chan._unlink()
def get_remote_server_key(self):
"""
Return the host key of the server (in client mode).
@note: Previously this call returned a tuple of (key type, key string).
You can get the same effect by calling
L{PKey.get_name <pkey.PKey.get_name>} for the key type, and
C{str(key)} for the key string.
@raise SSHException: if no session is currently active.
@return: public key of the remote server
@rtype: L{PKey <pkey.PKey>}
"""
if (not self.active) or (not self.initial_kex_done):
raise SSHException('No existing session')
return self.host_key
def is_active(self):
"""
Return true if this session is active (open).
@return: True if the session is still active (open); False if the
session is closed
@rtype: bool
"""
return self.active
def open_session(self):
"""
Request a new channel to the server, of type C{"session"}. This
is just an alias for C{open_channel('session')}.
@return: a new L{Channel}
@rtype: L{Channel}
@raise SSHException: if the request is rejected or the session ends
prematurely
"""
return self.open_channel('session')
def open_x11_channel(self, src_addr=None):
"""
Request a new channel to the client, of type C{"x11"}. This
is just an alias for C{open_channel('x11', src_addr=src_addr)}.
@param src_addr: the source address of the x11 server (port is the
x11 port, ie. 6010)
@type src_addr: (str, int)
@return: a new L{Channel}
@rtype: L{Channel}
@raise SSHException: if the request is rejected or the session ends
prematurely
"""
return self.open_channel('x11', src_addr=src_addr)
def open_forwarded_tcpip_channel(self, (src_addr, src_port), (dest_addr, dest_port)):
"""
Request a new channel back to the client, of type C{"forwarded-tcpip"}.
This is used after a client has requested port forwarding, for sending
incoming connections back to the client.
@param src_addr: originator's address
@param src_port: originator's port
@param dest_addr: local (server) connected address
@param dest_port: local (server) connected port
"""
return self.open_channel('forwarded-tcpip', (dest_addr, dest_port), (src_addr, src_port))
def open_channel(self, kind, dest_addr=None, src_addr=None):
"""
Request a new channel to the server. L{Channel}s are socket-like
objects used for the actual transfer of data across the session.
You may only request a channel after negotiating encryption (using
L{connect} or L{start_client}) and authenticating.
@param kind: the kind of channel requested (usually C{"session"},
C{"forwarded-tcpip"}, C{"direct-tcpip"}, or C{"x11"})
@type kind: str
@param dest_addr: the destination address of this port forwarding,
if C{kind} is C{"forwarded-tcpip"} or C{"direct-tcpip"} (ignored
for other channel types)
@type dest_addr: (str, int)
@param src_addr: the source address of this port forwarding, if
C{kind} is C{"forwarded-tcpip"}, C{"direct-tcpip"}, or C{"x11"}
@type src_addr: (str, int)
@return: a new L{Channel} on success
@rtype: L{Channel}
@raise SSHException: if the request is rejected or the session ends
prematurely
"""
if not self.active:
raise SSHException('SSH session not active')
self.lock.acquire()
try:
chanid = self._next_channel()
m = Message()
m.add_byte(chr(MSG_CHANNEL_OPEN))
m.add_string(kind)
m.add_int(chanid)
m.add_int(self.window_size)
m.add_int(self.max_packet_size)
if (kind == 'forwarded-tcpip') or (kind == 'direct-tcpip'):
m.add_string(dest_addr[0])
m.add_int(dest_addr[1])
m.add_string(src_addr[0])
m.add_int(src_addr[1])
elif kind == 'x11':
m.add_string(src_addr[0])
m.add_int(src_addr[1])
chan = Channel(chanid)
self._channels.put(chanid, chan)
self.channel_events[chanid] = event = threading.Event()
self.channels_seen[chanid] = True
chan._set_transport(self)
chan._set_window(self.window_size, self.max_packet_size)
finally:
self.lock.release()
self._send_user_message(m)
while True:
event.wait(0.1);
if not self.active:
e = self.get_exception()
if e is None:
e = SSHException('Unable to open channel.')
raise e
if event.isSet():
break
chan = self._channels.get(chanid)
if chan is not None:
return chan
e = self.get_exception()
if e is None:
e = SSHException('Unable to open channel.')
raise e
def 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.
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 C{server_addr} and C{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
L{accept}.
@param address: the address to bind when forwarding
@type address: str
@param port: the port to forward, or 0 to ask the server to allocate
any port
@type port: int
@param handler: optional handler for incoming forwarded connections
@type handler: function(Channel, (str, int), (str, int))
@return: the port # allocated by the server
@rtype: int
@raise SSHException: if the server refused the TCP forward request
"""
if not self.active:
raise SSHException('SSH session not active')
address = str(address)
port = int(port)
response = self.global_request('tcpip-forward', (address, port), wait=True)
if response is None:
raise SSHException('TCP forwarding request denied')
if port == 0:
port = response.get_int()
if handler is None:
def default_handler(channel, (src_addr, src_port), (dest_addr, dest_port)):
self._queue_incoming_channel(channel)
handler = default_handler
self._tcp_handler = handler
return port
def cancel_port_forward(self, address, port):
"""
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.
@param address: the address to stop forwarding
@type address: str
@param port: the port to stop forwarding
@type port: int
"""
if not self.active:
return
self._tcp_handler = None
self.global_request('cancel-tcpip-forward', (address, port), wait=True)
def 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.
@return: a new L{SFTPClient} object, referring to an sftp session
(channel) across this transport
@rtype: L{SFTPClient}
"""
return SFTPClient.from_transport(self)
def 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.
@param 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 bytes: int
"""
m = Message()
m.add_byte(chr(MSG_IGNORE))
if bytes is None:
bytes = (ord(rng.read(1)) % 32) + 10
m.add_bytes(rng.read(bytes))
self._send_user_message(m)
def 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.
@raise SSHException: if the key renegotiation failed (which causes the
session to end)
"""
self.completion_event = threading.Event()
self._send_kex_init()
while True:
self.completion_event.wait(0.1)
if not self.active:
e = self.get_exception()
if e is not None:
raise e
raise SSHException('Negotiation failed.')
if self.completion_event.isSet():
break
return
def set_keepalive(self, interval):
"""
Turn on/off keepalive packets (default is off). If this is set, after
C{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.
@param interval: seconds to wait before sending a keepalive packet (or
0 to disable keepalives).
@type interval: int
"""
self.packetizer.set_keepalive(interval,
lambda x=weakref.proxy(self): x.global_request('keepalive@lag.net', wait=False))
def global_request(self, kind, data=None, wait=True):
"""
Make a global request to the remote host. These are normally
extensions to the SSH2 protocol.
@param kind: name of the request.
@type kind: str
@param data: an optional tuple containing additional data to attach
to the request.
@type data: tuple
@param wait: C{True} if this method should not return until a response
is received; C{False} otherwise.
@type wait: bool
@return: a L{Message} containing possible additional data if the
request was successful (or an empty L{Message} if C{wait} was
C{False}); C{None} if the request was denied.
@rtype: L{Message}
"""
if wait:
self.completion_event = threading.Event()
m = Message()
m.add_byte(chr(MSG_GLOBAL_REQUEST))
m.add_string(kind)
m.add_boolean(wait)
if data is not None:
m.add(*data)
self._log(DEBUG, 'Sending global request "%s"' % kind)
self._send_user_message(m)
if not wait:
return None
while True:
self.completion_event.wait(0.1)
if not self.active:
return None
if self.completion_event.isSet():
break
return self.global_response
def accept(self, timeout=None):
"""
Return the next channel opened by the client over this transport, in
server mode. If no channel is opened before the given timeout, C{None}
is returned.
@param timeout: seconds to wait for a channel, or C{None} to wait
forever
@type timeout: int
@return: a new Channel opened by the client
@rtype: L{Channel}
"""
self.lock.acquire()
try:
if len(self.server_accepts) > 0:
chan = self.server_accepts.pop(0)
else:
self.server_accept_cv.wait(timeout)
if len(self.server_accepts) > 0:
chan = self.server_accepts.pop(0)
else:
# timeout
chan = None
finally:
self.lock.release()
return chan
def 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 L{start_client}, L{get_remote_server_key}, and
L{Transport.auth_password} or L{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 L{open_channel} or
L{open_session} to get a L{Channel} object, which is used for data
transfer.
@note: If you fail to supply a password or private key, this method may
succeed, but a subsequent L{open_channel} or L{open_session} call may
fail because you haven't authenticated yet.
@param hostkey: the host key expected from the server, or C{None} if
you don't want to do host key verification.
@type hostkey: L{PKey<pkey.PKey>}
@param username: the username to authenticate as.
@type username: str
@param password: a password to use for authentication, if you want to
use password authentication; otherwise C{None}.
@type password: str
@param pkey: a private key to use for authentication, if you want to
use private key authentication; otherwise C{None}.
@type pkey: L{PKey<pkey.PKey>}
@raise SSHException: if the SSH2 negotiation fails, the host key
supplied by the server is incorrect, or authentication fails.
"""
if hostkey is not None:
self._preferred_keys = [ hostkey.get_name() ]
self.start_client()
# check host key if we were given one
if (hostkey is not None):
key = self.get_remote_server_key()
if (key.get_name() != hostkey.get_name()) or (str(key) != str(hostkey)):
self._log(DEBUG, 'Bad host key from server')
self._log(DEBUG, 'Expected: %s: %s' % (hostkey.get_name(), repr(str(hostkey))))
self._log(DEBUG, 'Got : %s: %s' % (key.get_name(), repr(str(key))))
raise SSHException('Bad host key from server')
self._log(DEBUG, 'Host key verified (%s)' % hostkey.get_name())
if (pkey is not None) or (password is not None):
if password is not None:
self._log(DEBUG, 'Attempting password auth...')
self.auth_password(username, password)
else:
self._log(DEBUG, 'Attempting public-key auth...')
self.auth_publickey(username, pkey)
return
def 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 L{start_client}. The exception (if any) is cleared after
this call.
@return: an exception, or C{None} if there is no stored exception.
@rtype: Exception
@since: 1.1
"""
self.lock.acquire()
try:
e = self.saved_exception
self.saved_exception = None
return e
finally:
self.lock.release()
def 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 L{SubsystemHandler} for more
detailed documentation.
Any extra parameters (including keyword arguments) are saved and
passed to the L{SubsystemHandler} constructor later.
@param name: name of the subsystem.
@type name: str
@param handler: subclass of L{SubsystemHandler} that handles this
subsystem.
@type handler: class
"""
try:
self.lock.acquire()
self.subsystem_table[name] = (handler, larg, kwarg)
finally:
self.lock.release()
def is_authenticated(self):
"""
Return true if this session is active and authenticated.
@return: True if the session is still open and has been authenticated
successfully; False if authentication failed and/or the session is
closed.
@rtype: bool
"""
return self.active and (self.auth_handler is not None) and self.auth_handler.is_authenticated()
def get_username(self):
"""
Return the username this connection is authenticated for. If the
session is not authenticated (or authentication failed), this method
returns C{None}.
@return: username that was authenticated, or C{None}.
@rtype: string
"""
if not self.active or (self.auth_handler is None):
return None
return self.auth_handler.get_username()
def auth_none(self, username):
"""
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
L{BadAuthenticationType} exception raised.
@param username: the username to authenticate as
@type username: string
@return: list of auth types permissible for the next stage of
authentication (normally empty)
@rtype: list
@raise BadAuthenticationType: if "none" authentication isn't allowed
by the server for this user
@raise SSHException: if the authentication failed due to a network
error
@since: 1.5
"""
if (not self.active) or (not self.initial_kex_done):
raise SSHException('No existing session')
my_event = threading.Event()
self.auth_handler = AuthHandler(self)
self.auth_handler.auth_none(username, my_event)
return self.auth_handler.wait_for_response(my_event)
def auth_password(self, username, password, event=None, fallback=True):
"""
Authenticate to the server using a password. The username and password
are sent over an encrypted link.
If an C{event} is passed in, this method will return immediately, and
the event will be triggered once authentication succeeds or fails. On
success, L{is_authenticated} will return C{True}. On failure, you may
use L{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 C{fallback} is C{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.
@param username: the username to authenticate as
@type username: str
@param password: the password to authenticate with
@type password: str or unicode
@param event: an event to trigger when the authentication attempt is
complete (whether it was successful or not)
@type event: threading.Event
@param fallback: C{True} if an attempt at an automated "interactive"
password auth should be made if the server doesn't support normal
password auth
@type fallback: bool
@return: list of auth types permissible for the next stage of
authentication (normally empty)
@rtype: list
@raise BadAuthenticationType: if password authentication isn't
allowed by the server for this user (and no event was passed in)
@raise AuthenticationException: if the authentication failed (and no
event was passed in)
@raise SSHException: if there was a network error
"""
if (not self.active) or (not self.initial_kex_done):
# we should never try to send the password unless we're on a secure link
raise SSHException('No existing session')
if event is None:
my_event = threading.Event()
else:
my_event = event
self.auth_handler = AuthHandler(self)
self.auth_handler.auth_password(username, password, my_event)
if event is not None:
# caller wants to wait for event themselves
return []
try:
return self.auth_handler.wait_for_response(my_event)
except BadAuthenticationType, x:
# if password auth isn't allowed, but keyboard-interactive *is*, try to fudge it
if not fallback or ('keyboard-interactive' not in x.allowed_types):
raise
try:
def handler(title, instructions, fields):
if len(fields) > 1:
raise SSHException('Fallback authentication failed.')
if len(fields) == 0:
# for some reason, at least on os x, a 2nd request will
# be made with zero fields requested. maybe it's just
# to try to fake out automated scripting of the exact
# type we're doing here. *shrug* :)
return []
return [ password ]
return self.auth_interactive(username, handler)
except SSHException, ignored:
# attempt failed; just raise the original exception
raise x
return None
def auth_publickey(self, username, key, event=None):
"""
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 C{event} is passed in, this method will return immediately, and
the event will be triggered once authentication succeeds or fails. On
success, L{is_authenticated} will return C{True}. On failure, you may
use L{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.
@param username: the username to authenticate as
@type username: string
@param key: the private key to authenticate with
@type key: L{PKey <pkey.PKey>}
@param event: an event to trigger when the authentication attempt is
complete (whether it was successful or not)
@type event: threading.Event
@return: list of auth types permissible for the next stage of
authentication (normally empty)
@rtype: list
@raise BadAuthenticationType: if public-key authentication isn't
allowed by the server for this user (and no event was passed in)
@raise AuthenticationException: if the authentication failed (and no
event was passed in)
@raise SSHException: if there was a network error
"""
if (not self.active) or (not self.initial_kex_done):
# we should never try to authenticate unless we're on a secure link
raise SSHException('No existing session')
if event is None:
my_event = threading.Event()
else:
my_event = event
self.auth_handler = AuthHandler(self)
self.auth_handler.auth_publickey(username, key, my_event)
if event is not None:
# caller wants to wait for event themselves
return []
return self.auth_handler.wait_for_response(my_event)
def auth_interactive(self, username, handler, submethods=''):
"""
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: C{handler(title, instructions, prompt_list)}. The C{title} is
meant to be a dialog-window title, and the C{instructions} are user
instructions (both are strings). C{prompt_list} will be a list of
prompts, each prompt being a tuple of C{(str, bool)}. The string is
the prompt and the boolean indicates whether the user text should be
echoed.
A sample call would thus be:
C{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.
@param username: the username to authenticate as
@type username: string
@param handler: a handler for responding to server questions
@type handler: callable
@param submethods: a string list of desired submethods (optional)
@type submethods: str
@return: list of auth types permissible for the next stage of
authentication (normally empty).
@rtype: list
@raise BadAuthenticationType: if public-key authentication isn't
allowed by the server for this user
@raise AuthenticationException: if the authentication failed
@raise SSHException: if there was a network error
@since: 1.5
"""
if (not self.active) or (not self.initial_kex_done):
# we should never try to authenticate unless we're on a secure link
raise SSHException('No existing session')
my_event = threading.Event()
self.auth_handler = AuthHandler(self)
self.auth_handler.auth_interactive(username, handler, my_event, submethods)
return self.auth_handler.wait_for_response(my_event)
def set_log_channel(self, name):
"""
Set the channel for this transport's logging. The default is
C{"paramiko.transport"} but it can be set to anything you want.
(See the C{logging} module for more info.) SSH Channels will log
to a sub-channel of the one specified.
@param name: new channel name for logging
@type name: str
@since: 1.1
"""
self.log_name = name
self.logger = util.get_logger(name)
self.packetizer.set_log(self.logger)
def get_log_channel(self):
"""
Return the channel name used for this transport's logging.
@return: channel name.
@rtype: str
@since: 1.2
"""
return self.log_name
def 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.
@param hexdump: C{True} to log protocol traffix (in hex) to the log;
C{False} otherwise.
@type hexdump: bool
"""
self.packetizer.set_hexdump(hexdump)
def get_hexdump(self):
"""
Return C{True} if the transport is currently logging hex dumps of
protocol traffic.
@return: C{True} if hex dumps are being logged
@rtype: bool
@since: 1.4
"""
return self.packetizer.get_hexdump()
def use_compression(self, compress=True):
"""
Turn on/off compression. This will only have an affect before starting
the transport (ie before calling L{connect}, etc). By default,
compression is off since it negatively affects interactive sessions.
@param compress: C{True} to ask the remote client/server to compress
traffic; C{False} to refuse compression
@type compress: bool
@since: 1.5.2
"""
if compress:
self._preferred_compression = ( 'zlib@openssh.com', 'zlib', 'none' )
else:
self._preferred_compression = ( 'none', )
def getpeername(self):
"""
Return the address of the remote side of this Transport, if possible.
This is effectively a wrapper around C{'getpeername'} on the underlying
socket. If the socket-like object has no C{'getpeername'} method,
then C{("unknown", 0)} is returned.
@return: the address if the remote host, if known
@rtype: tuple(str, int)
"""
gp = getattr(self.sock, 'getpeername', None)
if gp is None:
return ('unknown', 0)
return gp()
def stop_thread(self):
self.active = False
self.packetizer.close()
### internals...
def _log(self, level, msg, *args):
if issubclass(type(msg), list):
for m in msg:
self.logger.log(level, m)
else:
self.logger.log(level, msg, *args)
def _get_modulus_pack(self):
"used by KexGex to find primes for group exchange"
return self._modulus_pack
def _next_channel(self):
"you are holding the lock"
chanid = self._channel_counter
while self._channels.get(chanid) is not None:
self._channel_counter = (self._channel_counter + 1) & 0xffffff
chanid = self._channel_counter
self._channel_counter = (self._channel_counter + 1) & 0xffffff
return chanid
def _unlink_channel(self, chanid):
"used by a Channel to remove itself from the active channel list"
self._channels.delete(chanid)
def _send_message(self, data):
self.packetizer.send_message(data)
def _send_user_message(self, data):
"""
send a message, but block if we're in key negotiation. this is used
for user-initiated requests.
"""
start = time.time()
while True:
self.clear_to_send.wait(0.1)
if not self.active:
self._log(DEBUG, 'Dropping user packet because connection is dead.')
return
self.clear_to_send_lock.acquire()
if self.clear_to_send.isSet():
break
self.clear_to_send_lock.release()
if time.time() > start + self.clear_to_send_timeout:
raise SSHException('Key-exchange timed out waiting for key negotiation')
try:
self._send_message(data)
finally:
self.clear_to_send_lock.release()
def _set_K_H(self, k, h):
"used by a kex object to set the K (root key) and H (exchange hash)"
self.K = k
self.H = h
if self.session_id == None:
self.session_id = h
def _expect_packet(self, *ptypes):
"used by a kex object to register the next packet type it expects to see"
self._expected_packet = tuple(ptypes)
def _verify_key(self, host_key, sig):
key = self._key_info[self.host_key_type](Message(host_key))
if key is None:
raise SSHException('Unknown host key type')
if not key.verify_ssh_sig(self.H, Message(sig)):
raise SSHException('Signature verification (%s) failed.' % self.host_key_type)
self.host_key = key
def _compute_key(self, id, nbytes):
"id is 'A' - 'F' for the various keys used by ssh"
m = Message()
m.add_mpint(self.K)
m.add_bytes(self.H)
m.add_byte(id)
m.add_bytes(self.session_id)
out = sofar = SHA.new(str(m)).digest()
while len(out) < nbytes:
m = Message()
m.add_mpint(self.K)
m.add_bytes(self.H)
m.add_bytes(sofar)
digest = SHA.new(str(m)).digest()
out += digest
sofar += digest
return out[:nbytes]
def _get_cipher(self, name, key, iv):
if name not in self._cipher_info:
raise SSHException('Unknown client cipher ' + name)
if name in ('arcfour128', 'arcfour256'):
# arcfour cipher
cipher = self._cipher_info[name]['class'].new(key)
# as per RFC 4345, the first 1536 bytes of keystream
# generated by the cipher MUST be discarded
cipher.encrypt(" " * 1536)
return cipher
elif name.endswith("-ctr"):
# CTR modes, we need a counter
counter = Counter.new(nbits=self._cipher_info[name]['block-size'] * 8, initial_value=util.inflate_long(iv, True))
return self._cipher_info[name]['class'].new(key, self._cipher_info[name]['mode'], iv, counter)
else:
return self._cipher_info[name]['class'].new(key, self._cipher_info[name]['mode'], iv)
def _set_x11_handler(self, handler):
# only called if a channel has turned on x11 forwarding
if handler is None:
# by default, use the same mechanism as accept()
def default_handler(channel, (src_addr, src_port)):
self._queue_incoming_channel(channel)
self._x11_handler = default_handler
else:
self._x11_handler = handler
def _queue_incoming_channel(self, channel):
self.lock.acquire()
try:
self.server_accepts.append(channel)
self.server_accept_cv.notify()
finally:
self.lock.release()
def run(self):
# (use the exposed "run" method, because if we specify a thread target
# of a private method, threading.Thread will keep a reference to it
# indefinitely, creating a GC cycle and not letting Transport ever be
# GC'd. it's a bug in Thread.)
# active=True occurs before the thread is launched, to avoid a race
_active_threads.append(self)
if self.server_mode:
self._log(DEBUG, 'starting thread (server mode): %s' % hex(long(id(self)) & 0xffffffffL))
else:
self._log(DEBUG, 'starting thread (client mode): %s' % hex(long(id(self)) & 0xffffffffL))
try:
self.packetizer.write_all(self.local_version + '\r\n')
self._check_banner()
self._send_kex_init()
self._expect_packet(MSG_KEXINIT)
while self.active:
if self.packetizer.need_rekey() and not self.in_kex:
self._send_kex_init()
try:
ptype, m = self.packetizer.read_message()
except NeedRekeyException:
continue
if ptype == MSG_IGNORE:
continue
elif ptype == MSG_DISCONNECT:
self._parse_disconnect(m)
self.active = False
self.packetizer.close()
break
elif ptype == MSG_DEBUG:
self._parse_debug(m)
continue
if len(self._expected_packet) > 0:
if ptype not in self._expected_packet:
raise SSHException('Expecting packet from %r, got %d' % (self._expected_packet, ptype))
self._expected_packet = tuple()
if (ptype >= 30) and (ptype <= 39):
self.kex_engine.parse_next(ptype, m)
continue
if ptype in self._handler_table:
self._handler_table[ptype](self, m)
elif ptype in self._channel_handler_table:
chanid = m.get_int()
chan = self._channels.get(chanid)
if chan is not None:
self._channel_handler_table[ptype](chan, m)
elif chanid in self.channels_seen:
self._log(DEBUG, 'Ignoring message for dead channel %d' % chanid)
else:
self._log(ERROR, 'Channel request for unknown channel %d' % chanid)
self.active = False
self.packetizer.close()
elif (self.auth_handler is not None) and (ptype in self.auth_handler._handler_table):
self.auth_handler._handler_table[ptype](self.auth_handler, m)
else:
self._log(WARNING, 'Oops, unhandled type %d' % ptype)
msg = Message()
msg.add_byte(chr(MSG_UNIMPLEMENTED))
msg.add_int(m.seqno)
self._send_message(msg)
except SSHException, e:
self._log(ERROR, 'Exception: ' + str(e))
self._log(ERROR, util.tb_strings())
self.saved_exception = e
except EOFError, e:
self._log(DEBUG, 'EOF in transport thread')
#self._log(DEBUG, util.tb_strings())
self.saved_exception = e
except socket.error, e:
if type(e.args) is tuple:
emsg = '%s (%d)' % (e.args[1], e.args[0])
else:
emsg = e.args
self._log(ERROR, 'Socket exception: ' + emsg)
self.saved_exception = e
except Exception, e:
self._log(ERROR, 'Unknown exception: ' + str(e))
self._log(ERROR, util.tb_strings())
self.saved_exception = e
_active_threads.remove(self)
for chan in self._channels.values():
chan._unlink()
if self.active:
self.active = False
self.packetizer.close()
if self.completion_event != None:
self.completion_event.set()
if self.auth_handler is not None:
self.auth_handler.abort()
for event in self.channel_events.values():
event.set()
try:
self.lock.acquire()
self.server_accept_cv.notify()
finally:
self.lock.release()
self.sock.close()
### protocol stages
def _negotiate_keys(self, m):
# throws SSHException on anything unusual
self.clear_to_send_lock.acquire()
try:
self.clear_to_send.clear()
finally:
self.clear_to_send_lock.release()
if self.local_kex_init == None:
# remote side wants to renegotiate
self._send_kex_init()
self._parse_kex_init(m)
self.kex_engine.start_kex()
def _check_banner(self):
# this is slow, but we only have to do it once
for i in range(100):
# give them 15 seconds for the first line, then just 2 seconds
# each additional line. (some sites have very high latency.)
if i == 0:
timeout = self.banner_timeout
else:
timeout = 2
try:
buf = self.packetizer.readline(timeout)
except Exception, x:
raise SSHException('Error reading SSH protocol banner' + str(x))
if buf[:4] == 'SSH-':
break
self._log(DEBUG, 'Banner: ' + buf)
if buf[:4] != 'SSH-':
raise SSHException('Indecipherable protocol version "' + buf + '"')
# save this server version string for later
self.remote_version = buf
# pull off any attached comment
comment = ''
i = string.find(buf, ' ')
if i >= 0:
comment = buf[i+1:]
buf = buf[:i]
# parse out version string and make sure it matches
segs = buf.split('-', 2)
if len(segs) < 3:
raise SSHException('Invalid SSH banner')
version = segs[1]
client = segs[2]
if version != '1.99' and version != '2.0':
raise SSHException('Incompatible version (%s instead of 2.0)' % (version,))
self._log(INFO, 'Connected (version %s, client %s)' % (version, client))
def _send_kex_init(self):
"""
announce to the other side that we'd like to negotiate keys, and what
kind of key negotiation we support.
"""
self.clear_to_send_lock.acquire()
try:
self.clear_to_send.clear()
finally:
self.clear_to_send_lock.release()
self.in_kex = True
if self.server_mode:
if (self._modulus_pack is None) and ('diffie-hellman-group-exchange-sha1' in self._preferred_kex):
# can't do group-exchange if we don't have a pack of potential primes
pkex = list(self.get_security_options().kex)
pkex.remove('diffie-hellman-group-exchange-sha1')
self.get_security_options().kex = pkex
available_server_keys = filter(self.server_key_dict.keys().__contains__,
self._preferred_keys)
else:
available_server_keys = self._preferred_keys
m = Message()
m.add_byte(chr(MSG_KEXINIT))
m.add_bytes(rng.read(16))
m.add_list(self._preferred_kex)
m.add_list(available_server_keys)
m.add_list(self._preferred_ciphers)
m.add_list(self._preferred_ciphers)
m.add_list(self._preferred_macs)
m.add_list(self._preferred_macs)
m.add_list(self._preferred_compression)
m.add_list(self._preferred_compression)
m.add_string('')
m.add_string('')
m.add_boolean(False)
m.add_int(0)
# save a copy for later (needed to compute a hash)
self.local_kex_init = str(m)
self._send_message(m)
def _parse_kex_init(self, m):
cookie = m.get_bytes(16)
kex_algo_list = m.get_list()
server_key_algo_list = m.get_list()
client_encrypt_algo_list = m.get_list()
server_encrypt_algo_list = m.get_list()
client_mac_algo_list = m.get_list()
server_mac_algo_list = m.get_list()
client_compress_algo_list = m.get_list()
server_compress_algo_list = m.get_list()
client_lang_list = m.get_list()
server_lang_list = m.get_list()
kex_follows = m.get_boolean()
unused = m.get_int()
self._log(DEBUG, 'kex algos:' + str(kex_algo_list) + ' server key:' + str(server_key_algo_list) + \
' client encrypt:' + str(client_encrypt_algo_list) + \
' server encrypt:' + str(server_encrypt_algo_list) + \
' client mac:' + str(client_mac_algo_list) + \
' server mac:' + str(server_mac_algo_list) + \
' client compress:' + str(client_compress_algo_list) + \
' server compress:' + str(server_compress_algo_list) + \
' client lang:' + str(client_lang_list) + \
' server lang:' + str(server_lang_list) + \
' kex follows?' + str(kex_follows))
# as a server, we pick the first item in the client's list that we support.
# as a client, we pick the first item in our list that the server supports.
if self.server_mode:
agreed_kex = filter(self._preferred_kex.__contains__, kex_algo_list)
else:
agreed_kex = filter(kex_algo_list.__contains__, self._preferred_kex)
if len(agreed_kex) == 0:
raise SSHException('Incompatible ssh peer (no acceptable kex algorithm)')
self.kex_engine = self._kex_info[agreed_kex[0]](self)
if self.server_mode:
available_server_keys = filter(self.server_key_dict.keys().__contains__,
self._preferred_keys)
agreed_keys = filter(available_server_keys.__contains__, server_key_algo_list)
else:
agreed_keys = filter(server_key_algo_list.__contains__, self._preferred_keys)
if len(agreed_keys) == 0:
raise SSHException('Incompatible ssh peer (no acceptable host key)')
self.host_key_type = agreed_keys[0]
if self.server_mode and (self.get_server_key() is None):
raise SSHException('Incompatible ssh peer (can\'t match requested host key type)')
if self.server_mode:
agreed_local_ciphers = filter(self._preferred_ciphers.__contains__,
server_encrypt_algo_list)
agreed_remote_ciphers = filter(self._preferred_ciphers.__contains__,
client_encrypt_algo_list)
else:
agreed_local_ciphers = filter(client_encrypt_algo_list.__contains__,
self._preferred_ciphers)
agreed_remote_ciphers = filter(server_encrypt_algo_list.__contains__,
self._preferred_ciphers)
if (len(agreed_local_ciphers) == 0) or (len(agreed_remote_ciphers) == 0):
raise SSHException('Incompatible ssh server (no acceptable ciphers)')
self.local_cipher = agreed_local_ciphers[0]
self.remote_cipher = agreed_remote_ciphers[0]
self._log(DEBUG, 'Ciphers agreed: local=%s, remote=%s' % (self.local_cipher, self.remote_cipher))
if self.server_mode:
agreed_remote_macs = filter(self._preferred_macs.__contains__, client_mac_algo_list)
agreed_local_macs = filter(self._preferred_macs.__contains__, server_mac_algo_list)
else:
agreed_local_macs = filter(client_mac_algo_list.__contains__, self._preferred_macs)
agreed_remote_macs = filter(server_mac_algo_list.__contains__, self._preferred_macs)
if (len(agreed_local_macs) == 0) or (len(agreed_remote_macs) == 0):
raise SSHException('Incompatible ssh server (no acceptable macs)')
self.local_mac = agreed_local_macs[0]
self.remote_mac = agreed_remote_macs[0]
if self.server_mode:
agreed_remote_compression = filter(self._preferred_compression.__contains__, client_compress_algo_list)
agreed_local_compression = filter(self._preferred_compression.__contains__, server_compress_algo_list)
else:
agreed_local_compression = filter(client_compress_algo_list.__contains__, self._preferred_compression)
agreed_remote_compression = filter(server_compress_algo_list.__contains__, self._preferred_compression)
if (len(agreed_local_compression) == 0) or (len(agreed_remote_compression) == 0):
raise SSHException('Incompatible ssh server (no acceptable compression) %r %r %r' % (agreed_local_compression, agreed_remote_compression, self._preferred_compression))
self.local_compression = agreed_local_compression[0]
self.remote_compression = agreed_remote_compression[0]
self._log(DEBUG, 'using kex %s; server key type %s; cipher: local %s, remote %s; mac: local %s, remote %s; compression: local %s, remote %s' %
(agreed_kex[0], self.host_key_type, self.local_cipher, self.remote_cipher, self.local_mac,
self.remote_mac, self.local_compression, self.remote_compression))
# save for computing hash later...
# now wait! openssh has a bug (and others might too) where there are
# actually some extra bytes (one NUL byte in openssh's case) added to
# the end of the packet but not parsed. turns out we need to throw
# away those bytes because they aren't part of the hash.
self.remote_kex_init = chr(MSG_KEXINIT) + m.get_so_far()
def _activate_inbound(self):
"switch on newly negotiated encryption parameters for inbound traffic"
block_size = self._cipher_info[self.remote_cipher]['block-size']
if self.server_mode:
IV_in = self._compute_key('A', block_size)
key_in = self._compute_key('C', self._cipher_info[self.remote_cipher]['key-size'])
else:
IV_in = self._compute_key('B', block_size)
key_in = self._compute_key('D', self._cipher_info[self.remote_cipher]['key-size'])
engine = self._get_cipher(self.remote_cipher, key_in, IV_in)
mac_size = self._mac_info[self.remote_mac]['size']
mac_engine = self._mac_info[self.remote_mac]['class']
# initial mac keys are done in the hash's natural size (not the potentially truncated
# transmission size)
if self.server_mode:
mac_key = self._compute_key('E', mac_engine.digest_size)
else:
mac_key = self._compute_key('F', mac_engine.digest_size)
self.packetizer.set_inbound_cipher(engine, block_size, mac_engine, mac_size, mac_key)
compress_in = self._compression_info[self.remote_compression][1]
if (compress_in is not None) and ((self.remote_compression != 'zlib@openssh.com') or self.authenticated):
self._log(DEBUG, 'Switching on inbound compression ...')
self.packetizer.set_inbound_compressor(compress_in())
def _activate_outbound(self):
"switch on newly negotiated encryption parameters for outbound traffic"
m = Message()
m.add_byte(chr(MSG_NEWKEYS))
self._send_message(m)
block_size = self._cipher_info[self.local_cipher]['block-size']
if self.server_mode:
IV_out = self._compute_key('B', block_size)
key_out = self._compute_key('D', self._cipher_info[self.local_cipher]['key-size'])
else:
IV_out = self._compute_key('A', block_size)
key_out = self._compute_key('C', self._cipher_info[self.local_cipher]['key-size'])
engine = self._get_cipher(self.local_cipher, key_out, IV_out)
mac_size = self._mac_info[self.local_mac]['size']
mac_engine = self._mac_info[self.local_mac]['class']
# initial mac keys are done in the hash's natural size (not the potentially truncated
# transmission size)
if self.server_mode:
mac_key = self._compute_key('F', mac_engine.digest_size)
else:
mac_key = self._compute_key('E', mac_engine.digest_size)
self.packetizer.set_outbound_cipher(engine, block_size, mac_engine, mac_size, mac_key)
compress_out = self._compression_info[self.local_compression][0]
if (compress_out is not None) and ((self.local_compression != 'zlib@openssh.com') or self.authenticated):
self._log(DEBUG, 'Switching on outbound compression ...')
self.packetizer.set_outbound_compressor(compress_out())
if not self.packetizer.need_rekey():
self.in_kex = False
# we always expect to receive NEWKEYS now
self._expect_packet(MSG_NEWKEYS)
def _auth_trigger(self):
self.authenticated = True
# delayed initiation of compression
if self.local_compression == 'zlib@openssh.com':
compress_out = self._compression_info[self.local_compression][0]
self._log(DEBUG, 'Switching on outbound compression ...')
self.packetizer.set_outbound_compressor(compress_out())
if self.remote_compression == 'zlib@openssh.com':
compress_in = self._compression_info[self.remote_compression][1]
self._log(DEBUG, 'Switching on inbound compression ...')
self.packetizer.set_inbound_compressor(compress_in())
def _parse_newkeys(self, m):
self._log(DEBUG, 'Switch to new keys ...')
self._activate_inbound()
# can also free a bunch of stuff here
self.local_kex_init = self.remote_kex_init = None
self.K = None
self.kex_engine = None
if self.server_mode and (self.auth_handler is None):
# create auth handler for server mode
self.auth_handler = AuthHandler(self)
if not self.initial_kex_done:
# this was the first key exchange
self.initial_kex_done = True
# send an event?
if self.completion_event != None:
self.completion_event.set()
# it's now okay to send data again (if this was a re-key)
if not self.packetizer.need_rekey():
self.in_kex = False
self.clear_to_send_lock.acquire()
try:
self.clear_to_send.set()
finally:
self.clear_to_send_lock.release()
return
def _parse_disconnect(self, m):
code = m.get_int()
desc = m.get_string()
self._log(INFO, 'Disconnect (code %d): %s' % (code, desc))
def _parse_global_request(self, m):
kind = m.get_string()
self._log(DEBUG, 'Received global request "%s"' % kind)
want_reply = m.get_boolean()
if not self.server_mode:
self._log(DEBUG, 'Rejecting "%s" global request from server.' % kind)
ok = False
elif kind == 'tcpip-forward':
address = m.get_string()
port = m.get_int()
ok = self.server_object.check_port_forward_request(address, port)
if ok != False:
ok = (ok,)
elif kind == 'cancel-tcpip-forward':
address = m.get_string()
port = m.get_int()
self.server_object.cancel_port_forward_request(address, port)
ok = True
else:
ok = self.server_object.check_global_request(kind, m)
extra = ()
if type(ok) is tuple:
extra = ok
ok = True
if want_reply:
msg = Message()
if ok:
msg.add_byte(chr(MSG_REQUEST_SUCCESS))
msg.add(*extra)
else:
msg.add_byte(chr(MSG_REQUEST_FAILURE))
self._send_message(msg)
def _parse_request_success(self, m):
self._log(DEBUG, 'Global request successful.')
self.global_response = m
if self.completion_event is not None:
self.completion_event.set()
def _parse_request_failure(self, m):
self._log(DEBUG, 'Global request denied.')
self.global_response = None
if self.completion_event is not None:
self.completion_event.set()
def _parse_channel_open_success(self, m):
chanid = m.get_int()
server_chanid = m.get_int()
server_window_size = m.get_int()
server_max_packet_size = m.get_int()
chan = self._channels.get(chanid)
if chan is None:
self._log(WARNING, 'Success for unrequested channel! [??]')
return
self.lock.acquire()
try:
chan._set_remote_channel(server_chanid, server_window_size, server_max_packet_size)
self._log(INFO, 'Secsh channel %d opened.' % chanid)
if chanid in self.channel_events:
self.channel_events[chanid].set()
del self.channel_events[chanid]
finally:
self.lock.release()
return
def _parse_channel_open_failure(self, m):
chanid = m.get_int()
reason = m.get_int()
reason_str = m.get_string()
lang = m.get_string()
reason_text = CONNECTION_FAILED_CODE.get(reason, '(unknown code)')
self._log(INFO, 'Secsh channel %d open FAILED: %s: %s' % (chanid, reason_str, reason_text))
self.lock.acquire()
try:
self.saved_exception = ChannelException(reason, reason_text)
if chanid in self.channel_events:
self._channels.delete(chanid)
if chanid in self.channel_events:
self.channel_events[chanid].set()
del self.channel_events[chanid]
finally:
self.lock.release()
return
def _parse_channel_open(self, m):
kind = m.get_string()
chanid = m.get_int()
initial_window_size = m.get_int()
max_packet_size = m.get_int()
reject = False
if (kind == 'x11') and (self._x11_handler is not None):
origin_addr = m.get_string()
origin_port = m.get_int()
self._log(DEBUG, 'Incoming x11 connection from %s:%d' % (origin_addr, origin_port))
self.lock.acquire()
try:
my_chanid = self._next_channel()
finally:
self.lock.release()
elif (kind == 'forwarded-tcpip') and (self._tcp_handler is not None):
server_addr = m.get_string()
server_port = m.get_int()
origin_addr = m.get_string()
origin_port = m.get_int()
self._log(DEBUG, 'Incoming tcp forwarded connection from %s:%d' % (origin_addr, origin_port))
self.lock.acquire()
try:
my_chanid = self._next_channel()
finally:
self.lock.release()
elif not self.server_mode:
self._log(DEBUG, 'Rejecting "%s" channel request from server.' % kind)
reject = True
reason = OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED
else:
self.lock.acquire()
try:
my_chanid = self._next_channel()
finally:
self.lock.release()
if kind == 'direct-tcpip':
# handle direct-tcpip requests comming from the client
dest_addr = m.get_string()
dest_port = m.get_int()
origin_addr = m.get_string()
origin_port = m.get_int()
reason = self.server_object.check_channel_direct_tcpip_request(
my_chanid, (origin_addr, origin_port),
(dest_addr, dest_port))
else:
reason = self.server_object.check_channel_request(kind, my_chanid)
if reason != OPEN_SUCCEEDED:
self._log(DEBUG, 'Rejecting "%s" channel request from client.' % kind)
reject = True
if reject:
msg = Message()
msg.add_byte(chr(MSG_CHANNEL_OPEN_FAILURE))
msg.add_int(chanid)
msg.add_int(reason)
msg.add_string('')
msg.add_string('en')
self._send_message(msg)
return
chan = Channel(my_chanid)
self.lock.acquire()
try:
self._channels.put(my_chanid, chan)
self.channels_seen[my_chanid] = True
chan._set_transport(self)
chan._set_window(self.window_size, self.max_packet_size)
chan._set_remote_channel(chanid, initial_window_size, max_packet_size)
finally:
self.lock.release()
m = Message()
m.add_byte(chr(MSG_CHANNEL_OPEN_SUCCESS))
m.add_int(chanid)
m.add_int(my_chanid)
m.add_int(self.window_size)
m.add_int(self.max_packet_size)
self._send_message(m)
self._log(INFO, 'Secsh channel %d (%s) opened.', my_chanid, kind)
if kind == 'x11':
self._x11_handler(chan, (origin_addr, origin_port))
elif kind == 'forwarded-tcpip':
chan.origin_addr = (origin_addr, origin_port)
self._tcp_handler(chan, (origin_addr, origin_port), (server_addr, server_port))
else:
self._queue_incoming_channel(chan)
def _parse_debug(self, m):
always_display = m.get_boolean()
msg = m.get_string()
lang = m.get_string()
self._log(DEBUG, 'Debug msg: ' + util.safe_string(msg))
def _get_subsystem_handler(self, name):
try:
self.lock.acquire()
if name not in self.subsystem_table:
return (None, [], {})
return self.subsystem_table[name]
finally:
self.lock.release()
_handler_table = {
MSG_NEWKEYS: _parse_newkeys,
MSG_GLOBAL_REQUEST: _parse_global_request,
MSG_REQUEST_SUCCESS: _parse_request_success,
MSG_REQUEST_FAILURE: _parse_request_failure,
MSG_CHANNEL_OPEN_SUCCESS: _parse_channel_open_success,
MSG_CHANNEL_OPEN_FAILURE: _parse_channel_open_failure,
MSG_CHANNEL_OPEN: _parse_channel_open,
MSG_KEXINIT: _negotiate_keys,
}
_channel_handler_table = {
MSG_CHANNEL_SUCCESS: Channel._request_success,
MSG_CHANNEL_FAILURE: Channel._request_failed,
MSG_CHANNEL_DATA: Channel._feed,
MSG_CHANNEL_EXTENDED_DATA: Channel._feed_extended,
MSG_CHANNEL_WINDOW_ADJUST: Channel._window_adjust,
MSG_CHANNEL_REQUEST: Channel._handle_request,
MSG_CHANNEL_EOF: Channel._handle_eof,
MSG_CHANNEL_CLOSE: Channel._handle_close,
}