~bzr-pqm/bzr/bzr.dev

# Copyright (C) 2005 Robey Pointer <robey@lag.net>

# Copyright (C) 2005, 2006 Canonical Ltd

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed 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 General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

"""Foundation SSH support for SFTP and smart server."""

import errno

import getpass

import os

import socket

import subprocess

import sys

from bzrlib.config import config_dir, ensure_config_dir_exists

from bzrlib.errors import (ConnectionError,

                           ParamikoNotPresent,

                           TransportError,

                           )

from bzrlib.osutils import pathjoin

from bzrlib.trace import mutter, warning

import bzrlib.ui

try:

    import paramiko

except ImportError, e:

    raise ParamikoNotPresent(e)

else:

    from paramiko.sftp_client import SFTPClient

SYSTEM_HOSTKEYS = {}

BZR_HOSTKEYS = {}

_paramiko_version = getattr(paramiko, '__version_info__', (0, 0, 0))

# Paramiko 1.5 tries to open a socket.AF_UNIX in order to connect

# to ssh-agent. That attribute doesn't exist on win32 (it does in cygwin)

# so we get an AttributeError exception. So we will not try to

# connect to an agent if we are on win32 and using Paramiko older than 1.6

_use_ssh_agent = (sys.platform != 'win32' or _paramiko_version >= (1, 6, 0))

_ssh_vendors = {}

def register_ssh_vendor(name, vendor):

    """Register SSH vendor."""

    _ssh_vendors[name] = vendor

_ssh_vendor = None

def _get_ssh_vendor():

    """Find out what version of SSH is on the system."""

    global _ssh_vendor

    if _ssh_vendor is not None:

        return _ssh_vendor

    if 'BZR_SSH' in os.environ:

        vendor_name = os.environ['BZR_SSH']

        try:

            _ssh_vendor = _ssh_vendors[vendor_name]

        except KeyError:

            raise UnknownSSH(vendor_name)

        return _ssh_vendor

    try:

        p = subprocess.Popen(['ssh', '-V'],

                             stdin=subprocess.PIPE,

                             stdout=subprocess.PIPE,

                             stderr=subprocess.PIPE,

                             **os_specific_subprocess_params())

        returncode = p.returncode

        stdout, stderr = p.communicate()

    except OSError:

        returncode = -1

        stdout = stderr = ''

    if 'OpenSSH' in stderr:

        mutter('ssh implementation is OpenSSH')

        _ssh_vendor = OpenSSHSubprocessVendor()

    elif 'SSH Secure Shell' in stderr:

        mutter('ssh implementation is SSH Corp.')

        _ssh_vendor = SSHCorpSubprocessVendor()

    if _ssh_vendor is not None:

        return _ssh_vendor

    # XXX: 20051123 jamesh

    # A check for putty's plink or lsh would go here.

    mutter('falling back to paramiko implementation')

    _ssh_vendor = ssh.ParamikoVendor()

    return _ssh_vendor

def _ignore_sigint():

    # TODO: This should possibly ignore SIGHUP as well, but bzr currently

    # doesn't handle it itself.

    # <https://launchpad.net/products/bzr/+bug/41433/+index>

    import signal

    signal.signal(signal.SIGINT, signal.SIG_IGN)

class LoopbackSFTP(object):

    """Simple wrapper for a socket that pretends to be a paramiko Channel."""

    def __init__(self, sock):

        self.__socket = sock

    def send(self, data):

        return self.__socket.send(data)

    def recv(self, n):

        return self.__socket.recv(n)

    def recv_ready(self):

        return True

    def close(self):

        self.__socket.close()

class SSHVendor(object):

    """Abstract base class for SSH vendor implementations."""

    def connect_sftp(self, username, password, host, port):

        """Make an SSH connection, and return an SFTPClient.

        :param username: an ascii string

        :param password: an ascii string

        :param host: a host name as an ascii string

        :param port: a port number

        :type port: int

        :raises: ConnectionError if it cannot connect.

        :rtype: paramiko.sftp_client.SFTPClient

        """

        raise NotImplementedError(self.connect_sftp)

    def connect_ssh(self, username, password, host, port, command):

        """Make an SSH connection, and return a pipe-like object.

        (This is currently unused, it's just here to indicate future directions

        for this code.)

        """

        raise NotImplementedError(self.connect_ssh)

class LoopbackVendor(SSHVendor):

    """SSH "vendor" that connects over a plain TCP socket, not SSH."""

    def connect_sftp(self, username, password, host, port):

        sock = socket.socket()

        try:

            sock.connect((host, port))

        except socket.error, e:

            raise ConnectionError('Unable to connect to SSH host %s:%s: %s'

                                  % (host, port, e))

        return SFTPClient(LoopbackSFTP(sock))

register_ssh_vendor('loopback', LoopbackVendor())

class ParamikoVendor(SSHVendor):

    """Vendor that uses paramiko."""

    def connect_sftp(self, username, password, host, port):

        global SYSTEM_HOSTKEYS, BZR_HOSTKEYS

        load_host_keys()

        try:

            t = paramiko.Transport((host, port or 22))

            t.set_log_channel('bzr.paramiko')

            t.start_client()

        except (paramiko.SSHException, socket.error), e:

            raise ConnectionError('Unable to reach SSH host %s:%s: %s' 

                                  % (host, port, e))

        server_key = t.get_remote_server_key()

        server_key_hex = paramiko.util.hexify(server_key.get_fingerprint())

        keytype = server_key.get_name()

        if host in SYSTEM_HOSTKEYS and keytype in SYSTEM_HOSTKEYS[host]:

            our_server_key = SYSTEM_HOSTKEYS[host][keytype]

            our_server_key_hex = paramiko.util.hexify(our_server_key.get_fingerprint())

        elif host in BZR_HOSTKEYS and keytype in BZR_HOSTKEYS[host]:

            our_server_key = BZR_HOSTKEYS[host][keytype]

            our_server_key_hex = paramiko.util.hexify(our_server_key.get_fingerprint())

        else:

            warning('Adding %s host key for %s: %s' % (keytype, host, server_key_hex))

            if host not in BZR_HOSTKEYS:

                BZR_HOSTKEYS[host] = {}

            BZR_HOSTKEYS[host][keytype] = server_key

            our_server_key = server_key

            our_server_key_hex = paramiko.util.hexify(our_server_key.get_fingerprint())

            save_host_keys()

        if server_key != our_server_key:

            filename1 = os.path.expanduser('~/.ssh/known_hosts')

            filename2 = pathjoin(config_dir(), 'ssh_host_keys')

            raise TransportError('Host keys for %s do not match!  %s != %s' % \

                (host, our_server_key_hex, server_key_hex),

                ['Try editing %s or %s' % (filename1, filename2)])

        _paramiko_auth(username, password, host, t)

        try:

            sftp = t.open_sftp_client()

        except paramiko.SSHException, e:

            raise ConnectionError('Unable to start sftp client %s:%d' %

                                  (host, port), e)

        return sftp

register_ssh_vendor('paramiko', ParamikoVendor())

class SubprocessVendor(SSHVendor):

    """Abstract base class for vendors that use pipes to a subprocess."""

    def connect_sftp(self, username, password, host, port):

        try:

            argv = self._get_vendor_specific_argv(username, host, port,

                                                  subsystem='sftp')

            proc = subprocess.Popen(argv,

                                    stdin=subprocess.PIPE,

                                    stdout=subprocess.PIPE,

                                    **os_specific_subprocess_params())

            sock = SSHSubprocess(proc)

            return SFTPClient(sock)

        except (EOFError, paramiko.SSHException), e:

            raise ConnectionError('Unable to connect to SSH host %s:%s: %s'

                                  % (host, port, e))

        except (OSError, IOError), e:

            # If the machine is fast enough, ssh can actually exit

            # before we try and send it the sftp request, which

            # raises a Broken Pipe

            if e.errno not in (errno.EPIPE,):

                raise

            raise ConnectionError('Unable to connect to SSH host %s:%s: %s'

                                  % (host, port, e))

    def _get_vendor_specific_argv(self, username, host, port, subsystem=None,

                                  command=None):

        """Returns the argument list to run the subprocess with.

        Exactly one of 'subsystem' and 'command' must be specified.

        """

        raise NotImplementedError(self._get_vendor_specific_argv)

register_ssh_vendor('none', ParamikoVendor())

class OpenSSHSubprocessVendor(SubprocessVendor):

    """SSH vendor that uses the 'ssh' executable from OpenSSH."""

    def _get_vendor_specific_argv(self, username, host, port, subsystem=None,

                                  command=None):

        assert subsystem is not None or command is not None, (

            'Must specify a command or subsystem')

        if subsystem is not None:

            assert command is None, (

                'subsystem and command are mutually exclusive')

        args = ['ssh',

                '-oForwardX11=no', '-oForwardAgent=no',

                '-oClearAllForwardings=yes', '-oProtocol=2',

                '-oNoHostAuthenticationForLocalhost=yes']

        if port is not None:

            args.extend(['-p', str(port)])

        if username is not None:

            args.extend(['-l', username])

        if subsystem is not None:

            args.extend(['-s', host, subsystem])

        else:

            args.extend([host] + command)

        return args

register_ssh_vendor('openssh', OpenSSHSubprocessVendor())

class SSHCorpSubprocessVendor(SubprocessVendor):

    """SSH vendor that uses the 'ssh' executable from SSH Corporation."""

    def _get_vendor_specific_argv(self, username, host, port, subsystem=None,

                                  command=None):

        assert subsystem is not None or command is not None, (

            'Must specify a command or subsystem')

        if subsystem is not None:

            assert command is None, (

                'subsystem and command are mutually exclusive')

        args = ['ssh', '-x']

        if port is not None:

            args.extend(['-p', str(port)])

        if username is not None:

            args.extend(['-l', username])

        if subsystem is not None:

            args.extend(['-s', subsystem, host])

        else:

            args.extend([host] + command)

        return args

register_ssh_vendor('ssh', SSHCorpSubprocessVendor())

def _paramiko_auth(username, password, host, paramiko_transport):

    # paramiko requires a username, but it might be none if nothing was supplied

    # use the local username, just in case.

    # We don't override username, because if we aren't using paramiko,

    # the username might be specified in ~/.ssh/config and we don't want to

    # force it to something else

    # Also, it would mess up the self.relpath() functionality

    username = username or getpass.getuser()

    if _use_ssh_agent:

        agent = paramiko.Agent()

        for key in agent.get_keys():

            mutter('Trying SSH agent key %s' % paramiko.util.hexify(key.get_fingerprint()))

            try:

                paramiko_transport.auth_publickey(username, key)

                return

            except paramiko.SSHException, e:

                pass

    # okay, try finding id_rsa or id_dss?  (posix only)

    if _try_pkey_auth(paramiko_transport, paramiko.RSAKey, username, 'id_rsa'):

        return

    if _try_pkey_auth(paramiko_transport, paramiko.DSSKey, username, 'id_dsa'):

        return

    if password:

        try:

            paramiko_transport.auth_password(username, password)

            return

        except paramiko.SSHException, e:

            pass

    # give up and ask for a password

    password = bzrlib.ui.ui_factory.get_password(

            prompt='SSH %(user)s@%(host)s password',

            user=username, host=host)

    try:

        paramiko_transport.auth_password(username, password)

    except paramiko.SSHException, e:

        raise ConnectionError('Unable to authenticate to SSH host as %s@%s' %

                              (username, host), e)

def _try_pkey_auth(paramiko_transport, pkey_class, username, filename):

    filename = os.path.expanduser('~/.ssh/' + filename)

    try:

        key = pkey_class.from_private_key_file(filename)

        paramiko_transport.auth_publickey(username, key)

        return True

    except paramiko.PasswordRequiredException:

        password = bzrlib.ui.ui_factory.get_password(

                prompt='SSH %(filename)s password',

                filename=filename)

        try:

            key = pkey_class.from_private_key_file(filename, password)

            paramiko_transport.auth_publickey(username, key)

            return True

        except paramiko.SSHException:

            mutter('SSH authentication via %s key failed.' % (os.path.basename(filename),))

    except paramiko.SSHException:

        mutter('SSH authentication via %s key failed.' % (os.path.basename(filename),))

    except IOError:

        pass

    return False

def load_host_keys():

    """

    Load system host keys (probably doesn't work on windows) and any

    "discovered" keys from previous sessions.

    """

    global SYSTEM_HOSTKEYS, BZR_HOSTKEYS

    try:

        SYSTEM_HOSTKEYS = paramiko.util.load_host_keys(os.path.expanduser('~/.ssh/known_hosts'))

    except Exception, e:

        mutter('failed to load system host keys: ' + str(e))

    bzr_hostkey_path = pathjoin(config_dir(), 'ssh_host_keys')

    try:

        BZR_HOSTKEYS = paramiko.util.load_host_keys(bzr_hostkey_path)

    except Exception, e:

        mutter('failed to load bzr host keys: ' + str(e))

        save_host_keys()

def save_host_keys():

    """

    Save "discovered" host keys in $(config)/ssh_host_keys/.

    """

    global SYSTEM_HOSTKEYS, BZR_HOSTKEYS

    bzr_hostkey_path = pathjoin(config_dir(), 'ssh_host_keys')

    ensure_config_dir_exists()

    try:

        f = open(bzr_hostkey_path, 'w')

        f.write('# SSH host keys collected by bzr\n')

        for hostname, keys in BZR_HOSTKEYS.iteritems():

            for keytype, key in keys.iteritems():

                f.write('%s %s %s\n' % (hostname, keytype, key.get_base64()))

        f.close()

    except IOError, e:

        mutter('failed to save bzr host keys: ' + str(e))

def os_specific_subprocess_params():

    """Get O/S specific subprocess parameters."""

    if sys.platform == 'win32':

        # setting the process group and closing fds is not supported on 

        # win32

        return {}

    else:

        # We close fds other than the pipes as the child process does not need 

        # them to be open.

        #

        # We also set the child process to ignore SIGINT.  Normally the signal

        # would be sent to every process in the foreground process group, but

        # this causes it to be seen only by bzr and not by ssh.  Python will

        # generate a KeyboardInterrupt in bzr, and we will then have a chance

        # to release locks or do other cleanup over ssh before the connection

        # goes away.  

        # <https://launchpad.net/products/bzr/+bug/5987>

        #

        # Running it in a separate process group is not good because then it

        # can't get non-echoed input of a password or passphrase.

        # <https://launchpad.net/products/bzr/+bug/40508>

        return {'preexec_fn': _ignore_sigint,

                'close_fds': True,

                }

class SSHSubprocess(object):

    """A socket-like object that talks to an ssh subprocess via pipes."""

    def __init__(self, proc):

        self.proc = proc

    def send(self, data):

        return os.write(self.proc.stdin.fileno(), data)

    def recv_ready(self):

        # TODO: jam 20051215 this function is necessary to support the

        # pipelined() function. In reality, it probably should use

        # poll() or select() to actually return if there is data

        # available, otherwise we probably don't get any benefit

        return True

    def recv(self, count):

        return os.read(self.proc.stdout.fileno(), count)

    def close(self):

        self.proc.stdin.close()

        self.proc.stdout.close()

        self.proc.wait()