paramiko.client

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

      1  # Copyright (C) 2006-2007  Robey Pointer <robey@lag.net>
      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  L{SSHClient}.
     21  """
     22
     23  from binascii import hexlify
     24  import getpass
     25  import os
     26  import socket
     27  import warnings
     28
     29  from paramiko.agent import Agent
     30  from paramiko.common import *
     31  from paramiko.dsskey import DSSKey
     32  from paramiko.hostkeys import HostKeys
     33  from paramiko.resource import ResourceManager
     34  from paramiko.rsakey import RSAKey
     35  from paramiko.ssh_exception import SSHException, BadHostKeyException
     36  from paramiko.transport import Transport
     37
     38
     39 -class MissingHostKeyPolicy (object):
     40      """
     41      Interface for defining the policy that L{SSHClient} should use when the
     42      SSH server's hostname is not in either the system host keys or the
     43      application's keys.  Pre-made classes implement policies for automatically
     44      adding the key to the application's L{HostKeys} object (L{AutoAddPolicy}),
     45      and for automatically rejecting the key (L{RejectPolicy}).
     46
     47      This function may be used to ask the user to verify the key, for example.
     48      """
     49
     50 -    def missing_host_key(self, client, hostname, key):
     51          """
     52          Called when an L{SSHClient} receives a server key for a server that
     53          isn't in either the system or local L{HostKeys} object.  To accept
     54          the key, simply return.  To reject, raised an exception (which will
     55          be passed to the calling application).
     56          """
     57          pass
     58
     59
     60 -class AutoAddPolicy (MissingHostKeyPolicy):
     61      """
     62      Policy for automatically adding the hostname and new host key to the
     63      local L{HostKeys} object, and saving it.  This is used by L{SSHClient}.
     64      """
     65
     66 -    def missing_host_key(self, client, hostname, key):
     67          client._host_keys.add(hostname, key.get_name(), key)
     68          if client._host_keys_filename is not None:
     69              client.save_host_keys(client._host_keys_filename)
     70          client._log(DEBUG, 'Adding %s host key for %s: %s' %
     71                      (key.get_name(), hostname, hexlify(key.get_fingerprint())))
     72
     73
     74 -class RejectPolicy (MissingHostKeyPolicy):
     75      """
     76      Policy for automatically rejecting the unknown hostname & key.  This is
     77      used by L{SSHClient}.
     78      """
     79
     80 -    def missing_host_key(self, client, hostname, key):
     81          client._log(DEBUG, 'Rejecting %s host key for %s: %s' %
     82                      (key.get_name(), hostname, hexlify(key.get_fingerprint())))
     83          raise SSHException('Unknown server %s' % hostname)
     84
     85
     86 -class WarningPolicy (MissingHostKeyPolicy):
     87      """
     88      Policy for logging a python-style warning for an unknown host key, but
     89      accepting it. This is used by L{SSHClient}.
     90      """
     91 -    def missing_host_key(self, client, hostname, key):
     92          warnings.warn('Unknown %s host key for %s: %s' %
     93                        (key.get_name(), hostname, hexlify(key.get_fingerprint())))
     94
     95
     96 -class SSHClient (object):
     97      """
     98      A high-level representation of a session with an SSH server.  This class
     99      wraps L{Transport}, L{Channel}, and L{SFTPClient} to take care of most
    100      aspects of authenticating and opening channels.  A typical use case is::
    101
    102          client = SSHClient()
    103          client.load_system_host_keys()
    104          client.connect('ssh.example.com')
    105          stdin, stdout, stderr = client.exec_command('ls -l')
    106
    107      You may pass in explicit overrides for authentication and server host key
    108      checking.  The default mechanism is to try to use local key files or an
    109      SSH agent (if one is running).
    110
    111      @since: 1.6
    112      """
    113
    114 -    def __init__(self):
    115          """
    116          Create a new SSHClient.
    117          """
    118          self._system_host_keys = HostKeys()
    119          self._host_keys = HostKeys()
    120          self._host_keys_filename = None
    121          self._log_channel = None
    122          self._policy = RejectPolicy()
    123          self._transport = None
    124
    125 -    def load_system_host_keys(self, filename=None):
    126          """
    127          Load host keys from a system (read-only) file.  Host keys read with
    128          this method will not be saved back by L{save_host_keys}.
    129
    130          This method can be called multiple times.  Each new set of host keys
    131          will be merged with the existing set (new replacing old if there are
    132          conflicts).
    133
    134          If C{filename} is left as C{None}, an attempt will be made to read
    135          keys from the user's local "known hosts" file, as used by OpenSSH,
    136          and no exception will be raised if the file can't be read.  This is
    137          probably only useful on posix.
    138
    139          @param filename: the filename to read, or C{None}
    140          @type filename: str
    141
    142          @raise IOError: if a filename was provided and the file could not be
    143              read
    144          """
    145          if filename is None:
    146              # try the user's .ssh key file, and mask exceptions
    147              filename = os.path.expanduser('~/.ssh/known_hosts')
    148              try:
    149                  self._system_host_keys.load(filename)
    150              except IOError:
    151                  pass
    152              return
    153          self._system_host_keys.load(filename)
    154
    155 -    def load_host_keys(self, filename):
    156          """
    157          Load host keys from a local host-key file.  Host keys read with this
    158          method will be checked I{after} keys loaded via L{load_system_host_keys},
    159          but will be saved back by L{save_host_keys} (so they can be modified).
    160          The missing host key policy L{AutoAddPolicy} adds keys to this set and
    161          saves them, when connecting to a previously-unknown server.
    162
    163          This method can be called multiple times.  Each new set of host keys
    164          will be merged with the existing set (new replacing old if there are
    165          conflicts).  When automatically saving, the last hostname is used.
    166
    167          @param filename: the filename to read
    168          @type filename: str
    169
    170          @raise IOError: if the filename could not be read
    171          """
    172          self._host_keys_filename = filename
    173          self._host_keys.load(filename)
    174
    175 -    def save_host_keys(self, filename):
    176          """
    177          Save the host keys back to a file.  Only the host keys loaded with
    178          L{load_host_keys} (plus any added directly) will be saved -- not any
    179          host keys loaded with L{load_system_host_keys}.
    180
    181          @param filename: the filename to save to
    182          @type filename: str
    183
    184          @raise IOError: if the file could not be written
    185          """
    186          f = open(filename, 'w')
    187          f.write('# SSH host keys collected by paramiko\n')
    188          for hostname, keys in self._host_keys.iteritems():
    189              for keytype, key in keys.iteritems():
    190                  f.write('%s %s %s\n' % (hostname, keytype, key.get_base64()))
    191          f.close()
    192
    193 -    def get_host_keys(self):
    194          """
    195          Get the local L{HostKeys} object.  This can be used to examine the
    196          local host keys or change them.
    197
    198          @return: the local host keys
    199          @rtype: L{HostKeys}
    200          """
    201          return self._host_keys
    202
    203 -    def set_log_channel(self, name):
    204          """
    205          Set the channel for logging.  The default is C{"paramiko.transport"}
    206          but it can be set to anything you want.
    207
    208          @param name: new channel name for logging
    209          @type name: str
    210          """
    211          self._log_channel = name
    212
    213 -    def set_missing_host_key_policy(self, policy):
    214          """
    215          Set the policy to use when connecting to a server that doesn't have a
    216          host key in either the system or local L{HostKeys} objects.  The
    217          default policy is to reject all unknown servers (using L{RejectPolicy}).
    218          You may substitute L{AutoAddPolicy} or write your own policy class.
    219
    220          @param policy: the policy to use when receiving a host key from a
    221              previously-unknown server
    222          @type policy: L{MissingHostKeyPolicy}
    223          """
    224          self._policy = policy
    225
    226 -    def connect(self, hostname, port=22, username=None, password=None, pkey=None,
    227                  key_filename=None, timeout=None, allow_agent=True, look_for_keys=True):
    228          """
    229          Connect to an SSH server and authenticate to it.  The server's host key
    230          is checked against the system host keys (see L{load_system_host_keys})
    231          and any local host keys (L{load_host_keys}).  If the server's hostname
    232          is not found in either set of host keys, the missing host key policy
    233          is used (see L{set_missing_host_key_policy}).  The default policy is
    234          to reject the key and raise an L{SSHException}.
    235
    236          Authentication is attempted in the following order of priority:
    237
    238              - The C{pkey} or C{key_filename} passed in (if any)
    239              - Any key we can find through an SSH agent
    240              - Any "id_rsa" or "id_dsa" key discoverable in C{~/.ssh/}
    241              - Plain username/password auth, if a password was given
    242
    243          If a private key requires a password to unlock it, and a password is
    244          passed in, that password will be used to attempt to unlock the key.
    245
    246          @param hostname: the server to connect to
    247          @type hostname: str
    248          @param port: the server port to connect to
    249          @type port: int
    250          @param username: the username to authenticate as (defaults to the
    251              current local username)
    252          @type username: str
    253          @param password: a password to use for authentication or for unlocking
    254              a private key
    255          @type password: str
    256          @param pkey: an optional private key to use for authentication
    257          @type pkey: L{PKey}
    258          @param key_filename: the filename of an optional private key to use
    259              for authentication
    260          @type key_filename: str
    261          @param timeout: an optional timeout (in seconds) for the TCP connect
    262          @type timeout: float
    263          @param allow_agent: set to False to disable connecting to the SSH agent
    264          @type allow_agent: bool
    265          @param look_for_keys: set to False to disable searching for discoverable
    266              private key files in C{~/.ssh/}
    267          @type look_for_keys: bool
    268
    269          @raise BadHostKeyException: if the server's host key could not be
    270              verified
    271          @raise AuthenticationException: if authentication failed
    272          @raise SSHException: if there was any other error connecting or
    273              establishing an SSH session
    274          @raise socket.error: if a socket error occurred while connecting
    275          """
    276          sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    277          if timeout is not None:
    278              try:
    279                  sock.settimeout(timeout)
    280              except:
    281                  pass
    282
    283          sock.connect((hostname, port))
    284          t = self._transport = Transport(sock)
    285
    286          if self._log_channel is not None:
    287              t.set_log_channel(self._log_channel)
    288          t.start_client()
    289          ResourceManager.register(self, t)
    290
    291          server_key = t.get_remote_server_key()
    292          keytype = server_key.get_name()
    293
    294          our_server_key = self._system_host_keys.get(hostname, {}).get(keytype, None)
    295          if our_server_key is None:
    296              our_server_key = self._host_keys.get(hostname, {}).get(keytype, None)
    297          if our_server_key is None:
    298              # will raise exception if the key is rejected; let that fall out
    299              self._policy.missing_host_key(self, hostname, server_key)
    300              # if the callback returns, assume the key is ok
    301              our_server_key = server_key
    302
    303          if server_key != our_server_key:
    304              raise BadHostKeyException(hostname, server_key, our_server_key)
    305
    306          if username is None:
    307              username = getpass.getuser()
    308
    309          self._auth(username, password, pkey, key_filename, allow_agent, look_for_keys)
    310
    311 -    def close(self):
    312          """
    313          Close this SSHClient and its underlying L{Transport}.
    314          """
    315          if self._transport is None:
    316              return
    317          self._transport.close()
    318          self._transport = None
    319
    320 -    def exec_command(self, command, bufsize=-1):
    321          """
    322          Execute a command on the SSH server.  A new L{Channel} is opened and
    323          the requested command is executed.  The command's input and output
    324          streams are returned as python C{file}-like objects representing
    325          stdin, stdout, and stderr.
    326
    327          @param command: the command to execute
    328          @type command: str
    329          @param bufsize: interpreted the same way as by the built-in C{file()} function in python
    330          @type bufsize: int
    331          @return: the stdin, stdout, and stderr of the executing command
    332          @rtype: tuple(L{ChannelFile}, L{ChannelFile}, L{ChannelFile})
    333
    334          @raise SSHException: if the server fails to execute the command
    335          """
    336          chan = self._transport.open_session()
    337          chan.exec_command(command)
    338          stdin = chan.makefile('wb', bufsize)
    339          stdout = chan.makefile('rb', bufsize)
    340          stderr = chan.makefile_stderr('rb', bufsize)
    341          return stdin, stdout, stderr
    342
    343 -    def invoke_shell(self, term='vt100', width=80, height=24):
    344          """
    345          Start an interactive shell session on the SSH server.  A new L{Channel}
    346          is opened and connected to a pseudo-terminal using the requested
    347          terminal type and size.
    348
    349          @param term: the terminal type to emulate (for example, C{"vt100"})
    350          @type term: str
    351          @param width: the width (in characters) of the terminal window
    352          @type width: int
    353          @param height: the height (in characters) of the terminal window
    354          @type height: int
    355          @return: a new channel connected to the remote shell
    356          @rtype: L{Channel}
    357
    358          @raise SSHException: if the server fails to invoke a shell
    359          """
    360          chan = self._transport.open_session()
    361          chan.get_pty(term, width, height)
    362          chan.invoke_shell()
    363          return chan
    364
    365 -    def open_sftp(self):
    366          """
    367          Open an SFTP session on the SSH server.
    368
    369          @return: a new SFTP session object
    370          @rtype: L{SFTPClient}
    371          """
    372          return self._transport.open_sftp_client()
    373
    374 -    def get_transport(self):
    375          """
    376          Return the underlying L{Transport} object for this SSH connection.
    377          This can be used to perform lower-level tasks, like opening specific
    378          kinds of channels.
    379
    380          @return: the Transport for this connection
    381          @rtype: L{Transport}
    382          """
    383          return self._transport
    384
    385 -    def _auth(self, username, password, pkey, key_filename, allow_agent, look_for_keys):
    386          """
    387          Try, in order:
    388
    389              - The key passed in, if one was passed in.
    390              - Any key we can find through an SSH agent (if allowed).
    391              - Any "id_rsa" or "id_dsa" key discoverable in ~/.ssh/ (if allowed).
    392              - Plain username/password auth, if a password was given.
    393
    394          (The password might be needed to unlock a private key.)
    395          """
    396          saved_exception = None
    397
    398          if pkey is not None:
    399              try:
    400                  self._log(DEBUG, 'Trying SSH key %s' % hexlify(pkey.get_fingerprint()))
    401                  self._transport.auth_publickey(username, pkey)
    402                  return
    403              except SSHException, e:
    404                  saved_exception = e
    405
    406          if key_filename is not None:
    407              for pkey_class in (RSAKey, DSSKey):
    408                  try:
    409                      key = pkey_class.from_private_key_file(key_filename, password)
    410                      self._log(DEBUG, 'Trying key %s from %s' % (hexlify(key.get_fingerprint()), key_filename))
    411                      self._transport.auth_publickey(username, key)
    412                      return
    413                  except SSHException, e:
    414                      saved_exception = e
    415
    416          if allow_agent:
    417              for key in Agent().get_keys():
    418                  try:
    419                      self._log(DEBUG, 'Trying SSH agent key %s' % hexlify(key.get_fingerprint()))
    420                      self._transport.auth_publickey(username, key)
    421                      return
    422                  except SSHException, e:
    423                      saved_exception = e
    424
    425          keyfiles = []
    426          rsa_key = os.path.expanduser('~/.ssh/id_rsa')
    427          dsa_key = os.path.expanduser('~/.ssh/id_dsa')
    428          if os.path.isfile(rsa_key):
    429              keyfiles.append((RSAKey, rsa_key))
    430          if os.path.isfile(dsa_key):
    431              keyfiles.append((DSSKey, dsa_key))
    432          # look in ~/ssh/ for windows users:
    433          rsa_key = os.path.expanduser('~/ssh/id_rsa')
    434          dsa_key = os.path.expanduser('~/ssh/id_dsa')
    435          if os.path.isfile(rsa_key):
    436              keyfiles.append((RSAKey, rsa_key))
    437          if os.path.isfile(dsa_key):
    438              keyfiles.append((DSSKey, dsa_key))
    439
    440          if not look_for_keys:
    441              keyfiles = []
    442
    443          for pkey_class, filename in keyfiles:
    444              try:
    445                  key = pkey_class.from_private_key_file(filename, password)
    446                  self._log(DEBUG, 'Trying discovered key %s in %s' % (hexlify(key.get_fingerprint()), filename))
    447                  self._transport.auth_publickey(username, key)
    448                  return
    449              except SSHException, e:
    450                  saved_exception = e
    451              except IOError, e:
    452                  saved_exception = e
    453
    454          if password is not None:
    455              try:
    456                  self._transport.auth_password(username, password)
    457                  return
    458              except SSHException, e:
    459                  saved_exception = e
    460
    461          # if we got an auth-failed exception earlier, re-raise it
    462          if saved_exception is not None:
    463              raise saved_exception
    464          raise SSHException('No authentication methods available')
    465
    466 -    def _log(self, level, msg):
    467          self._transport._log(level, msg)
    468