Package paramiko :: Module agent |
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# Source Code for Module paramiko.agent

      1  # Copyright (C) 2003-2007  John Rochester <john@jrochester.org>
      2  #
      3  # This file is part of paramiko.
      4  #
      5  # Paramiko is free software; you can redistribute it and/or modify it under the
      6  # terms of the GNU Lesser General Public License as published by the Free
      7  # Software Foundation; either version 2.1 of the License, or (at your option)
      8  # any later version.
      9  #
     10  # Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY
     11  # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
     12  # A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
     13  # details.
     14  #
     15  # You should have received a copy of the GNU Lesser General Public License
     16  # along with Paramiko; if not, write to the Free Software Foundation, Inc.,
     17  # 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
     18
     19  """
     20  SSH Agent interface for Unix clients.
     21  """
     22
     23  import os
     24  import socket
     25  import struct
     26  import sys
     27
     28  from paramiko.ssh_exception import SSHException
     29  from paramiko.message import Message
     30  from paramiko.pkey import PKey
     31
     32
     33  SSH2_AGENTC_REQUEST_IDENTITIES, SSH2_AGENT_IDENTITIES_ANSWER, \
     34      SSH2_AGENTC_SIGN_REQUEST, SSH2_AGENT_SIGN_RESPONSE = range(11, 15)
     35
     36
     37 -class Agent:
     38      """
     39      Client interface for using private keys from an SSH agent running on the
     40      local machine.  If an SSH agent is running, this class can be used to
     41      connect to it and retreive L{PKey} objects which can be used when
     42      attempting to authenticate to remote SSH servers.
     43
     44      Because the SSH agent protocol uses environment variables and unix-domain
     45      sockets, this probably doesn't work on Windows.  It does work on most
     46      posix platforms though (Linux and MacOS X, for example).
     47      """
     48
     49 -    def __init__(self):
     50          """
     51          Open a session with the local machine's SSH agent, if one is running.
     52          If no agent is running, initialization will succeed, but L{get_keys}
     53          will return an empty tuple.
     54
     55          @raise SSHException: if an SSH agent is found, but speaks an
     56              incompatible protocol
     57          """
     58          self.conn = None
     59          self.keys = ()
     60          if ('SSH_AUTH_SOCK' in os.environ) and (sys.platform != 'win32'):
     61              conn = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
     62              try:
     63                  conn.connect(os.environ['SSH_AUTH_SOCK'])
     64              except:
     65                  # probably a dangling env var: the ssh agent is gone
     66                  return
     67              self.conn = conn
     68          elif sys.platform == 'win32':
     69              import win_pageant
     70              if win_pageant.can_talk_to_agent():
     71                  self.conn = win_pageant.PageantConnection()
     72              else:
     73                  return
     74          else:
     75              # no agent support
     76              return
     77
     78          ptype, result = self._send_message(chr(SSH2_AGENTC_REQUEST_IDENTITIES))
     79          if ptype != SSH2_AGENT_IDENTITIES_ANSWER:
     80              raise SSHException('could not get keys from ssh-agent')
     81          keys = []
     82          for i in range(result.get_int()):
     83              keys.append(AgentKey(self, result.get_string()))
     84              result.get_string()
     85          self.keys = tuple(keys)
     86
     87 -    def close(self):
     88          """
     89          Close the SSH agent connection.
     90          """
     91          if self.conn is not None:
     92              self.conn.close()
     93          self.conn = None
     94          self.keys = ()
     95
     96 -    def get_keys(self):
     97          """
     98          Return the list of keys available through the SSH agent, if any.  If
     99          no SSH agent was running (or it couldn't be contacted), an empty list
    100          will be returned.
    101
    102          @return: a list of keys available on the SSH agent
    103          @rtype: tuple of L{AgentKey}
    104          """
    105          return self.keys
    106
    107 -    def _send_message(self, msg):
    108          msg = str(msg)
    109          self.conn.send(struct.pack('>I', len(msg)) + msg)
    110          l = self._read_all(4)
    111          msg = Message(self._read_all(struct.unpack('>I', l)[0]))
    112          return ord(msg.get_byte()), msg
    113
    114 -    def _read_all(self, wanted):
    115          result = self.conn.recv(wanted)
    116          while len(result) < wanted:
    117              if len(result) == 0:
    118                  raise SSHException('lost ssh-agent')
    119              extra = self.conn.recv(wanted - len(result))
    120              if len(extra) == 0:
    121                  raise SSHException('lost ssh-agent')
    122              result += extra
    123          return result
    124
    125
    126 -class AgentKey(PKey):
    127      """
    128      Private key held in a local SSH agent.  This type of key can be used for
    129      authenticating to a remote server (signing).  Most other key operations
    130      work as expected.
    131      """
    132
    133 -    def __init__(self, agent, blob):
    134          self.agent = agent
    135          self.blob = blob
    136          self.name = Message(blob).get_string()
    137
    138 -    def __str__(self):
    139          return self.blob
    140
    141 -    def get_name(self):
    142          return self.name
    143
    144 -    def sign_ssh_data(self, rng, data):
    145          msg = Message()
    146          msg.add_byte(chr(SSH2_AGENTC_SIGN_REQUEST))
    147          msg.add_string(self.blob)
    148          msg.add_string(data)
    149          msg.add_int(0)
    150          ptype, result = self.agent._send_message(msg)
    151          if ptype != SSH2_AGENT_SIGN_RESPONSE:
    152              raise SSHException('key cannot be used for signing')
    153          return result.get_string()
    154