~bzr-pqm/bzr/bzr.dev

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

# Copyright (C) 2005, 2006, 2007 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

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

import errno

import getpass

import logging

import os

import socket

import subprocess

import sys

from bzrlib import (

    config,

    errors,

    osutils,

    trace,

    ui,

    )

try:

    import paramiko

except ImportError, e:

    # If we have an ssh subprocess, we don't strictly need paramiko for all ssh

    # access

    paramiko = None

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))

class SSHVendorManager(object):

    """Manager for manage SSH vendors."""

    # Note, although at first sign the class interface seems similar to

    # bzrlib.registry.Registry it is not possible/convenient to directly use

    # the Registry because the class just has "get()" interface instead of the

    # Registry's "get(key)".

    def __init__(self):

        self._ssh_vendors = {}

        self._cached_ssh_vendor = None

        self._default_ssh_vendor = None

    def register_default_vendor(self, vendor):

        """Register default SSH vendor."""

        self._default_ssh_vendor = vendor

    def register_vendor(self, name, vendor):

        """Register new SSH vendor by name."""

        self._ssh_vendors[name] = vendor

    def clear_cache(self):

        """Clear previously cached lookup result."""

        self._cached_ssh_vendor = None

    def _get_vendor_by_environment(self, environment=None):

        """Return the vendor or None based on BZR_SSH environment variable.

        :raises UnknownSSH: if the BZR_SSH environment variable contains

                            unknown vendor name

        """

        if environment is None:

            environment = os.environ

        if 'BZR_SSH' in environment:

            vendor_name = environment['BZR_SSH']

            try:

                vendor = self._ssh_vendors[vendor_name]

            except KeyError:

                raise errors.UnknownSSH(vendor_name)

            return vendor

        return None

    def _get_ssh_version_string(self, args):

        """Return SSH version string from the subprocess."""

        try:

            p = subprocess.Popen(args,

                                 stdout=subprocess.PIPE,

                                 stderr=subprocess.PIPE,

                                 **os_specific_subprocess_params())

            stdout, stderr = p.communicate()

        except OSError:

            stdout = stderr = ''

        return stdout + stderr

    def _get_vendor_by_version_string(self, version, args):

        """Return the vendor or None based on output from the subprocess.

        :param version: The output of 'ssh -V' like command.

        :param args: Command line that was run.

        """

        vendor = None

        if 'OpenSSH' in version:

            trace.mutter('ssh implementation is OpenSSH')

            vendor = OpenSSHSubprocessVendor()

        elif 'SSH Secure Shell' in version:

            trace.mutter('ssh implementation is SSH Corp.')

            vendor = SSHCorpSubprocessVendor()

        elif 'plink' in version and args[0] == 'plink':

            # Checking if "plink" was the executed argument as Windows

            # sometimes reports 'ssh -V' incorrectly with 'plink' in it's

            # version.  See https://bugs.launchpad.net/bzr/+bug/107155

            trace.mutter("ssh implementation is Putty's plink.")

            vendor = PLinkSubprocessVendor()

        return vendor

    def _get_vendor_by_inspection(self):

        """Return the vendor or None by checking for known SSH implementations."""

        for args in (['ssh', '-V'], ['plink', '-V']):

            version = self._get_ssh_version_string(args)

            vendor = self._get_vendor_by_version_string(version, args)

            if vendor is not None:

                return vendor

        return None

    def get_vendor(self, environment=None):

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

        :raises SSHVendorNotFound: if no any SSH vendor is found

        :raises UnknownSSH: if the BZR_SSH environment variable contains

                            unknown vendor name

        """

        if self._cached_ssh_vendor is None:

            vendor = self._get_vendor_by_environment(environment)

            if vendor is None:

                vendor = self._get_vendor_by_inspection()

                if vendor is None:

                    trace.mutter('falling back to default implementation')

                    vendor = self._default_ssh_vendor

                    if vendor is None:

                        raise errors.SSHVendorNotFound()

            self._cached_ssh_vendor = vendor

        return self._cached_ssh_vendor

_ssh_vendor_manager = SSHVendorManager()

_get_ssh_vendor = _ssh_vendor_manager.get_vendor

register_default_ssh_vendor = _ssh_vendor_manager.register_default_vendor

register_ssh_vendor = _ssh_vendor_manager.register_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 SocketAsChannelAdapter(object):

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

    def __init__(self, sock):

        self.__socket = sock

    def get_name(self):

        return "bzr SocketAsChannelAdapter"

    def send(self, data):

        return self.__socket.send(data)

    def recv(self, n):

        try:

            return self.__socket.recv(n)

        except socket.error, e:

            if e.args[0] in (errno.EPIPE, errno.ECONNRESET, errno.ECONNABORTED,

                             errno.EBADF):

                # Connection has closed.  Paramiko expects an empty string in

                # this case, not an exception.

                return ''

            raise

    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 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.

        :returns: something with a `close` method, and a `get_filelike_channels`

            method that returns a pair of (read, write) filelike objects.

        """

        raise NotImplementedError(self.connect_ssh)

    def _raise_connection_error(self, host, port=None, orig_error=None,

                                msg='Unable to connect to SSH host'):

        """Raise a SocketConnectionError with properly formatted host.

        This just unifies all the locations that try to raise ConnectionError,

        so that they format things properly.

        """

        raise errors.SocketConnectionError(host=host, port=port, msg=msg,

                                           orig_error=orig_error)

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:

            self._raise_connection_error(host, port=port, orig_error=e)

        return SFTPClient(SocketAsChannelAdapter(sock))

register_ssh_vendor('loopback', LoopbackVendor())

class _ParamikoSSHConnection(object):

    def __init__(self, channel):

        self.channel = channel

    def get_filelike_channels(self):

        return self.channel.makefile('rb'), self.channel.makefile('wb')

    def close(self):

        return self.channel.close()

class ParamikoVendor(SSHVendor):

    """Vendor that uses paramiko."""

    def _connect(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:

            self._raise_connection_error(host, port=port, orig_error=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:

            trace.warning('Adding %s host key for %s: %s'

                          % (keytype, host, server_key_hex))

            add = getattr(BZR_HOSTKEYS, 'add', None)

            if add is not None: # paramiko >= 1.X.X

                BZR_HOSTKEYS.add(host, keytype, server_key)

            else:

                BZR_HOSTKEYS.setdefault(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 = osutils.pathjoin(config.config_dir(), 'ssh_host_keys')

            raise errors.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, port, t)

        return t

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

        t = self._connect(username, password, host, port)

        try:

            return t.open_sftp_client()

        except paramiko.SSHException, e:

            self._raise_connection_error(host, port=port, orig_error=e,

                                         msg='Unable to start sftp client')

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

        t = self._connect(username, password, host, port)

        try:

            channel = t.open_session()

            cmdline = ' '.join(command)

            channel.exec_command(cmdline)

            return _ParamikoSSHConnection(channel)

        except paramiko.SSHException, e:

            self._raise_connection_error(host, port=port, orig_error=e,

                                         msg='Unable to invoke remote bzr')

if paramiko is not None:

    vendor = ParamikoVendor()

    register_ssh_vendor('paramiko', vendor)

    register_ssh_vendor('none', vendor)

    register_default_ssh_vendor(vendor)

    _sftp_connection_errors = (EOFError, paramiko.SSHException)

    del vendor

else:

    _sftp_connection_errors = (EOFError,)

class SubprocessVendor(SSHVendor):

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

    def _connect(self, argv):

        proc = subprocess.Popen(argv,

                                stdin=subprocess.PIPE,

                                stdout=subprocess.PIPE,

                                **os_specific_subprocess_params())

        return SSHSubprocess(proc)

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

        try:

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

                                                  subsystem='sftp')

            sock = self._connect(argv)

            return SFTPClient(SocketAsChannelAdapter(sock))

        except _sftp_connection_errors, e:

            self._raise_connection_error(host, port=port, orig_error=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

            self._raise_connection_error(host, port=port, orig_error=e)

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

        try:

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

                                                  command=command)

            return self._connect(argv)

        except (EOFError), e:

            self._raise_connection_error(host, port=port, orig_error=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

            self._raise_connection_error(host, port=port, orig_error=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)

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):

        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):

        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())

class PLinkSubprocessVendor(SubprocessVendor):

    """SSH vendor that uses the 'plink' executable from Putty."""

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

                                  command=None):

        args = ['plink', '-x', '-a', '-ssh', '-2', '-batch']

        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('plink', PLinkSubprocessVendor())

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

    auth = config.AuthenticationConfig()

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

    # supplied.  If so, use the local username.

    if username is None:

        username = auth.get_user('ssh', host, port=port,

                                 default=getpass.getuser())

    if _use_ssh_agent:

        agent = paramiko.Agent()

        for key in agent.get_keys():

            trace.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 we have gotten this far, we are about to try for passwords, do an

    # auth_none check to see if it is even supported.

    supported_auth_types = []

    try:

        # Note that with paramiko <1.7.5 this logs an INFO message:

        #    Authentication type (none) not permitted.

        # So we explicitly disable the logging level for this action

        old_level = paramiko_transport.logger.level

        paramiko_transport.logger.setLevel(logging.WARNING)

        try:

            paramiko_transport.auth_none(username)

        finally:

            paramiko_transport.logger.setLevel(old_level)

    except paramiko.BadAuthenticationType, e:

        # Supported methods are in the exception

        supported_auth_types = e.allowed_types

    except paramiko.SSHException, e:

        # Don't know what happened, but just ignore it

        pass

    if 'password' not in supported_auth_types:

        raise errors.ConnectionError('Unable to authenticate to SSH host as'

            '\n  %s@%s\nsupported auth types: %s'

            % (username, host, supported_auth_types))

    if password:

        try:

            paramiko_transport.auth_password(username, password)

            return

        except paramiko.SSHException, e:

            pass

    # give up and ask for a password

    password = auth.get_password('ssh', host, username, port=port)

    # get_password can still return None, which means we should not prompt

    if password is not None:

        try:

            paramiko_transport.auth_password(username, password)

        except paramiko.SSHException, e:

            raise errors.ConnectionError(

                'Unable to authenticate to SSH host as'

                '\n  %s@%s\n' % (username, host), e)

    else:

        raise errors.ConnectionError('Unable to authenticate to SSH host as'

                                     '  %s@%s' % (username, host))

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 = 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:

            trace.mutter('SSH authentication via %s key failed.'

                         % (os.path.basename(filename),))

    except paramiko.SSHException:

        trace.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 IOError, e:

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

    bzr_hostkey_path = osutils.pathjoin(config.config_dir(), 'ssh_host_keys')

    try:

        BZR_HOSTKEYS = paramiko.util.load_host_keys(bzr_hostkey_path)

    except IOError, e:

        trace.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 = osutils.pathjoin(config.config_dir(), 'ssh_host_keys')

    config.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:

        trace.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(self, count):

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

    def close(self):

        self.proc.stdin.close()

        self.proc.stdout.close()

        self.proc.wait()

    def get_filelike_channels(self):

        return (self.proc.stdout, self.proc.stdin)