~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

"""Implementation of Transport over SFTP, using paramiko."""

import errno
import getpass
import itertools
import os
import random
import re
import select
import socket
import stat
import subprocess
import sys
import time
import urllib
import urlparse
import weakref

from bzrlib.config import config_dir, ensure_config_dir_exists
from bzrlib.errors import (ConnectionError,
                           FileExists, 
                           TransportNotPossible, NoSuchFile, PathNotChild,
                           TransportError,
                           LockError, 
                           PathError,
                           ParamikoNotPresent,
                           )
from bzrlib.osutils import pathjoin, fancy_rename, getcwd
from bzrlib.trace import mutter, warning, error
from bzrlib.transport import (
    register_urlparse_netloc_protocol,
    Server,
    split_url,
    Transport,
    )
import bzrlib.ui
import bzrlib.urlutils as urlutils

try:
    import paramiko
except ImportError, e:
    raise ParamikoNotPresent(e)
else:
    from paramiko.sftp import (SFTP_FLAG_WRITE, SFTP_FLAG_CREATE,
                               SFTP_FLAG_EXCL, SFTP_FLAG_TRUNC,
                               CMD_HANDLE, CMD_OPEN)
    from paramiko.sftp_attr import SFTPAttributes
    from paramiko.sftp_file import SFTPFile
    from paramiko.sftp_client import SFTPClient


register_urlparse_netloc_protocol('sftp')


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)
    

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,
                }


_paramiko_version = getattr(paramiko, '__version_info__', (0, 0, 0))
# don't use prefetch unless paramiko version >= 1.5.5 (there were bugs earlier)
_default_do_prefetch = (_paramiko_version >= (1, 5, 5))

# 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_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

    _ssh_vendor = 'none'

    if 'BZR_SSH' in os.environ:
        _ssh_vendor = os.environ['BZR_SSH']
        if _ssh_vendor == 'paramiko':
            _ssh_vendor = 'none'
        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 = 'openssh'
    elif 'SSH Secure Shell' in stderr:
        mutter('ssh implementation is SSH Corp.')
        _ssh_vendor = 'ssh'

    if _ssh_vendor != 'none':
        return _ssh_vendor

    # XXX: 20051123 jamesh
    # A check for putty's plink or lsh would go here.

    mutter('falling back to paramiko implementation')
    return _ssh_vendor


class SFTPSubprocess:
    """A socket-like object that talks to an ssh subprocess via pipes."""
    def __init__(self, hostname, vendor, port=None, user=None):
        assert vendor in ['openssh', 'ssh']
        if vendor == 'openssh':
            args = ['ssh',
                    '-oForwardX11=no', '-oForwardAgent=no',
                    '-oClearAllForwardings=yes', '-oProtocol=2',
                    '-oNoHostAuthenticationForLocalhost=yes']
            if port is not None:
                args.extend(['-p', str(port)])
            if user is not None:
                args.extend(['-l', user])
            args.extend(['-s', hostname, 'sftp'])
        elif vendor == 'ssh':
            args = ['ssh', '-x']
            if port is not None:
                args.extend(['-p', str(port)])
            if user is not None:
                args.extend(['-l', user])
            args.extend(['-s', 'sftp', hostname])

        self.proc = subprocess.Popen(args,
                                     stdin=subprocess.PIPE,
                                     stdout=subprocess.PIPE,
                                     **os_specific_subprocess_params())

    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()


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()


SYSTEM_HOSTKEYS = {}
BZR_HOSTKEYS = {}

# This is a weakref dictionary, so that we can reuse connections
# that are still active. Long term, it might be nice to have some
# sort of expiration policy, such as disconnect if inactive for
# X seconds. But that requires a lot more fanciness.
_connected_hosts = weakref.WeakValueDictionary()

def clear_connection_cache():
    """Remove all hosts from the SFTP connection cache.

    Primarily useful for test cases wanting to force garbage collection.
    """
    _connected_hosts.clear()


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))


class SFTPLock(object):
    """This fakes a lock in a remote location."""
    __slots__ = ['path', 'lock_path', 'lock_file', 'transport']
    def __init__(self, path, transport):
        assert isinstance(transport, SFTPTransport)

        self.lock_file = None
        self.path = path
        self.lock_path = path + '.write-lock'
        self.transport = transport
        try:
            # RBC 20060103 FIXME should we be using private methods here ?
            abspath = transport._remote_path(self.lock_path)
            self.lock_file = transport._sftp_open_exclusive(abspath)
        except FileExists:
            raise LockError('File %r already locked' % (self.path,))

    def __del__(self):
        """Should this warn, or actually try to cleanup?"""
        if self.lock_file:
            warning("SFTPLock %r not explicitly unlocked" % (self.path,))
            self.unlock()

    def unlock(self):
        if not self.lock_file:
            return
        self.lock_file.close()
        self.lock_file = None
        try:
            self.transport.delete(self.lock_path)
        except (NoSuchFile,):
            # What specific errors should we catch here?
            pass


class SFTPTransport (Transport):
    """Transport implementation for SFTP access"""

    _do_prefetch = _default_do_prefetch
    # TODO: jam 20060717 Conceivably these could be configurable, either
    #       by auto-tuning at run-time, or by a configuration (per host??)
    #       but the performance curve is pretty flat, so just going with
    #       reasonable defaults.
    _max_readv_combine = 200
    # Having to round trip to the server means waiting for a response,
    # so it is better to download extra bytes.
    # 8KiB had good performance for both local and remote network operations
    _bytes_to_read_before_seek = 8192

    # The sftp spec says that implementations SHOULD allow reads
    # to be at least 32K. paramiko.readv() does an async request
    # for the chunks. So we need to keep it within a single request
    # size for paramiko <= 1.6.1. paramiko 1.6.2 will probably chop
    # up the request itself, rather than us having to worry about it
    _max_request_size = 32768

    def __init__(self, base, clone_from=None):
        assert base.startswith('sftp://')
        self._parse_url(base)
        base = self._unparse_url()
        if base[-1] != '/':
            base += '/'
        super(SFTPTransport, self).__init__(base)
        if clone_from is None:
            self._sftp_connect()
        else:
            # use the same ssh connection, etc
            self._sftp = clone_from._sftp
        # super saves 'self.base'
    
    def should_cache(self):
        """
        Return True if the data pulled across should be cached locally.
        """
        return True

    def clone(self, offset=None):
        """
        Return a new SFTPTransport with root at self.base + offset.
        We share the same SFTP session between such transports, because it's
        fairly expensive to set them up.
        """
        if offset is None:
            return SFTPTransport(self.base, self)
        else:
            return SFTPTransport(self.abspath(offset), self)

    def abspath(self, relpath):
        """
        Return the full url to the given relative path.
        
        @param relpath: the relative path or path components
        @type relpath: str or list
        """
        return self._unparse_url(self._remote_path(relpath))
    
    def _remote_path(self, relpath):
        """Return the path to be passed along the sftp protocol for relpath.
        
        relpath is a urlencoded string.
        """
        # FIXME: share the common code across transports
        assert isinstance(relpath, basestring)
        relpath = urlutils.unescape(relpath).split('/')
        basepath = self._path.split('/')
        if len(basepath) > 0 and basepath[-1] == '':
            basepath = basepath[:-1]

        for p in relpath:
            if p == '..':
                if len(basepath) == 0:
                    # In most filesystems, a request for the parent
                    # of root, just returns root.
                    continue
                basepath.pop()
            elif p == '.':
                continue # No-op
            else:
                basepath.append(p)

        path = '/'.join(basepath)
        # mutter('relpath => remotepath %s => %s', relpath, path)
        return path

    def relpath(self, abspath):
        username, password, host, port, path = self._split_url(abspath)
        error = []
        if (username != self._username):
            error.append('username mismatch')
        if (host != self._host):
            error.append('host mismatch')
        if (port != self._port):
            error.append('port mismatch')
        if (not path.startswith(self._path)):
            error.append('path mismatch')
        if error:
            extra = ': ' + ', '.join(error)
            raise PathNotChild(abspath, self.base, extra=extra)
        pl = len(self._path)
        return path[pl:].strip('/')

    def has(self, relpath):
        """
        Does the target location exist?
        """
        try:
            self._sftp.stat(self._remote_path(relpath))
            return True
        except IOError:
            return False

    def get(self, relpath):
        """
        Get the file at the given relative path.

        :param relpath: The relative path to the file
        """
        try:
            path = self._remote_path(relpath)
            f = self._sftp.file(path, mode='rb')
            if self._do_prefetch and (getattr(f, 'prefetch', None) is not None):
                f.prefetch()
            return f
        except (IOError, paramiko.SSHException), e:
            self._translate_io_exception(e, path, ': error retrieving')

    def readv(self, relpath, offsets):
        """See Transport.readv()"""
        # We overload the default readv() because we want to use a file
        # that does not have prefetch enabled.
        # Also, if we have a new paramiko, it implements an async readv()
        if not offsets:
            return

        try:
            path = self._remote_path(relpath)
            fp = self._sftp.file(path, mode='rb')
            readv = getattr(fp, 'readv', None)
            if readv:
                return self._sftp_readv(fp, offsets)
            mutter('seek and read %s offsets', len(offsets))
            return self._seek_and_read(fp, offsets)
        except (IOError, paramiko.SSHException), e:
            self._translate_io_exception(e, path, ': error retrieving')

    def _sftp_readv(self, fp, offsets):
        """Use the readv() member of fp to do async readv.

        And then read them using paramiko.readv(). paramiko.readv()
        does not support ranges > 64K, so it caps the request size, and
        just reads until it gets all the stuff it wants
        """
        offsets = list(offsets)
        sorted_offsets = sorted(offsets)

        # The algorithm works as follows:
        # 1) Coalesce nearby reads into a single chunk
        #    This generates a list of combined regions, the total size
        #    and the size of the sub regions. This coalescing step is limited
        #    in the number of nearby chunks to combine, and is allowed to
        #    skip small breaks in the requests. Limiting it makes sure that
        #    we can start yielding some data earlier, and skipping means we
        #    make fewer requests. (Beneficial even when using async)
        # 2) Break up this combined regions into chunks that are smaller
        #    than 64KiB. Technically the limit is 65536, but we are a
        #    little bit conservative. This is because sftp has a maximum
        #    return chunk size of 64KiB (max size of an unsigned short)
        # 3) Issue a readv() to paramiko to create an async request for
        #    all of this data
        # 4) Read in the data as it comes back, until we've read one
        #    continuous section as determined in step 1
        # 5) Break up the full sections into hunks for the original requested
        #    offsets. And put them in a cache
        # 6) Check if the next request is in the cache, and if it is, remove
        #    it from the cache, and yield its data. Continue until no more
        #    entries are in the cache.
        # 7) loop back to step 4 until all data has been read
        #
        # TODO: jam 20060725 This could be optimized one step further, by
        #       attempting to yield whatever data we have read, even before
        #       the first coallesced section has been fully processed.

        # When coalescing for use with readv(), we don't really need to
        # use any fudge factor, because the requests are made asynchronously
        coalesced = list(self._coalesce_offsets(sorted_offsets,
                               limit=self._max_readv_combine,
                               fudge_factor=0,
                               ))
        requests = []
        for c_offset in coalesced:
            start = c_offset.start
            size = c_offset.length

            # We need to break this up into multiple requests
            while size > 0:
                next_size = min(size, self._max_request_size)
                requests.append((start, next_size))
                size -= next_size
                start += next_size

        mutter('SFTP.readv() %s offsets => %s coalesced => %s requests',
                len(offsets), len(coalesced), len(requests))

        # Queue the current read until we have read the full coalesced section
        cur_data = []
        cur_data_len = 0
        cur_coalesced_stack = iter(coalesced)
        cur_coalesced = cur_coalesced_stack.next()

        # Cache the results, but only until they have been fulfilled
        data_map = {}
        # turn the list of offsets into a stack
        offset_stack = iter(offsets)
        cur_offset_and_size = offset_stack.next()

        for data in fp.readv(requests):
            cur_data += data
            cur_data_len += len(data)

            if cur_data_len < cur_coalesced.length:
                continue
            assert cur_data_len == cur_coalesced.length, \
                "Somehow we read too much: %s != %s" % (cur_data_len,
                                                        cur_coalesced.length)
            all_data = ''.join(cur_data)
            cur_data = []
            cur_data_len = 0

            for suboffset, subsize in cur_coalesced.ranges:
                key = (cur_coalesced.start+suboffset, subsize)
                data_map[key] = all_data[suboffset:suboffset+subsize]

            # Now that we've read some data, see if we can yield anything back
            while cur_offset_and_size in data_map:
                this_data = data_map.pop(cur_offset_and_size)
                yield cur_offset_and_size[0], this_data
                cur_offset_and_size = offset_stack.next()

            # Now that we've read all of the data for this coalesced section
            # on to the next
            cur_coalesced = cur_coalesced_stack.next()

    def put(self, relpath, f, mode=None):
        """
        Copy the file-like or string object into the location.

        :param relpath: Location to put the contents, relative to base.
        :param f:       File-like or string object.
        :param mode: The final mode for the file
        """
        final_path = self._remote_path(relpath)
        self._put(final_path, f, mode=mode)

    def _put(self, abspath, f, mode=None):
        """Helper function so both put() and copy_abspaths can reuse the code"""
        tmp_abspath = '%s.tmp.%.9f.%d.%d' % (abspath, time.time(),
                        os.getpid(), random.randint(0,0x7FFFFFFF))
        fout = self._sftp_open_exclusive(tmp_abspath, mode=mode)
        closed = False
        try:
            try:
                fout.set_pipelined(True)
                self._pump(f, fout)
            except (IOError, paramiko.SSHException), e:
                self._translate_io_exception(e, tmp_abspath)
            if mode is not None:
                self._sftp.chmod(tmp_abspath, mode)
            fout.close()
            closed = True
            self._rename_and_overwrite(tmp_abspath, abspath)
        except Exception, e:
            # If we fail, try to clean up the temporary file
            # before we throw the exception
            # but don't let another exception mess things up
            # Write out the traceback, because otherwise
            # the catch and throw destroys it
            import traceback
            mutter(traceback.format_exc())
            try:
                if not closed:
                    fout.close()
                self._sftp.remove(tmp_abspath)
            except:
                # raise the saved except
                raise e
            # raise the original with its traceback if we can.
            raise

    def iter_files_recursive(self):
        """Walk the relative paths of all files in this transport."""
        queue = list(self.list_dir('.'))
        while queue:
            relpath = urllib.quote(queue.pop(0))
            st = self.stat(relpath)
            if stat.S_ISDIR(st.st_mode):
                for i, basename in enumerate(self.list_dir(relpath)):
                    queue.insert(i, relpath+'/'+basename)
            else:
                yield relpath

    def mkdir(self, relpath, mode=None):
        """Create a directory at the given path."""
        path = self._remote_path(relpath)
        try:
            # In the paramiko documentation, it says that passing a mode flag 
            # will filtered against the server umask.
            # StubSFTPServer does not do this, which would be nice, because it is
            # what we really want :)
            # However, real servers do use umask, so we really should do it that way
            self._sftp.mkdir(path)
            if mode is not None:
                self._sftp.chmod(path, mode=mode)
        except (paramiko.SSHException, IOError), e:
            self._translate_io_exception(e, path, ': unable to mkdir',
                failure_exc=FileExists)

    def _translate_io_exception(self, e, path, more_info='', 
                                failure_exc=PathError):
        """Translate a paramiko or IOError into a friendlier exception.

        :param e: The original exception
        :param path: The path in question when the error is raised
        :param more_info: Extra information that can be included,
                          such as what was going on
        :param failure_exc: Paramiko has the super fun ability to raise completely
                           opaque errors that just set "e.args = ('Failure',)" with
                           no more information.
                           If this parameter is set, it defines the exception 
                           to raise in these cases.
        """
        # paramiko seems to generate detailless errors.
        self._translate_error(e, path, raise_generic=False)
        if hasattr(e, 'args'):
            if (e.args == ('No such file or directory',) or
                e.args == ('No such file',)):
                raise NoSuchFile(path, str(e) + more_info)
            if (e.args == ('mkdir failed',)):
                raise FileExists(path, str(e) + more_info)
            # strange but true, for the paramiko server.
            if (e.args == ('Failure',)):
                raise failure_exc(path, str(e) + more_info)
            mutter('Raising exception with args %s', e.args)
        if hasattr(e, 'errno'):
            mutter('Raising exception with errno %s', e.errno)
        raise e

    def append(self, relpath, f, mode=None):
        """
        Append the text in the file-like object into the final
        location.
        """
        try:
            path = self._remote_path(relpath)
            fout = self._sftp.file(path, 'ab')
            if mode is not None:
                self._sftp.chmod(path, mode)
            result = fout.tell()
            self._pump(f, fout)
            return result
        except (IOError, paramiko.SSHException), e:
            self._translate_io_exception(e, relpath, ': unable to append')

    def rename(self, rel_from, rel_to):
        """Rename without special overwriting"""
        try:
            self._sftp.rename(self._remote_path(rel_from),
                              self._remote_path(rel_to))
        except (IOError, paramiko.SSHException), e:
            self._translate_io_exception(e, rel_from,
                    ': unable to rename to %r' % (rel_to))

    def _rename_and_overwrite(self, abs_from, abs_to):
        """Do a fancy rename on the remote server.
        
        Using the implementation provided by osutils.
        """
        try:
            fancy_rename(abs_from, abs_to,
                    rename_func=self._sftp.rename,
                    unlink_func=self._sftp.remove)
        except (IOError, paramiko.SSHException), e:
            self._translate_io_exception(e, abs_from, ': unable to rename to %r' % (abs_to))

    def move(self, rel_from, rel_to):
        """Move the item at rel_from to the location at rel_to"""
        path_from = self._remote_path(rel_from)
        path_to = self._remote_path(rel_to)
        self._rename_and_overwrite(path_from, path_to)

    def delete(self, relpath):
        """Delete the item at relpath"""
        path = self._remote_path(relpath)
        try:
            self._sftp.remove(path)
        except (IOError, paramiko.SSHException), e:
            self._translate_io_exception(e, path, ': unable to delete')
            
    def listable(self):
        """Return True if this store supports listing."""
        return True

    def list_dir(self, relpath):
        """
        Return a list of all files at the given location.
        """
        # does anything actually use this?
        path = self._remote_path(relpath)
        try:
            return self._sftp.listdir(path)
        except (IOError, paramiko.SSHException), e:
            self._translate_io_exception(e, path, ': failed to list_dir')

    def rmdir(self, relpath):
        """See Transport.rmdir."""
        path = self._remote_path(relpath)
        try:
            return self._sftp.rmdir(path)
        except (IOError, paramiko.SSHException), e:
            self._translate_io_exception(e, path, ': failed to rmdir')

    def stat(self, relpath):
        """Return the stat information for a file."""
        path = self._remote_path(relpath)
        try:
            return self._sftp.stat(path)
        except (IOError, paramiko.SSHException), e:
            self._translate_io_exception(e, path, ': unable to stat')

    def lock_read(self, relpath):
        """
        Lock the given file for shared (read) access.
        :return: A lock object, which has an unlock() member function
        """
        # FIXME: there should be something clever i can do here...
        class BogusLock(object):
            def __init__(self, path):
                self.path = path
            def unlock(self):
                pass
        return BogusLock(relpath)

    def lock_write(self, relpath):
        """
        Lock the given file for exclusive (write) access.
        WARNING: many transports do not support this, so trying avoid using it

        :return: A lock object, which has an unlock() member function
        """
        # This is a little bit bogus, but basically, we create a file
        # which should not already exist, and if it does, we assume
        # that there is a lock, and if it doesn't, the we assume
        # that we have taken the lock.
        return SFTPLock(relpath, self)

    def _unparse_url(self, path=None):
        if path is None:
            path = self._path
        path = urllib.quote(path)
        # handle homedir paths
        if not path.startswith('/'):
            path = "/~/" + path
        netloc = urllib.quote(self._host)
        if self._username is not None:
            netloc = '%s@%s' % (urllib.quote(self._username), netloc)
        if self._port is not None:
            netloc = '%s:%d' % (netloc, self._port)
        return urlparse.urlunparse(('sftp', netloc, path, '', '', ''))

    def _split_url(self, url):
        (scheme, username, password, host, port, path) = split_url(url)
        assert scheme == 'sftp'

        # the initial slash should be removed from the path, and treated
        # as a homedir relative path (the path begins with a double slash
        # if it is absolute).
        # see draft-ietf-secsh-scp-sftp-ssh-uri-03.txt
        # RBC 20060118 we are not using this as its too user hostile. instead
        # we are following lftp and using /~/foo to mean '~/foo'.
        # handle homedir paths
        if path.startswith('/~/'):
            path = path[3:]
        elif path == '/~':
            path = ''
        return (username, password, host, port, path)

    def _parse_url(self, url):
        (self._username, self._password,
         self._host, self._port, self._path) = self._split_url(url)

    def _sftp_connect(self):
        """Connect to the remote sftp server.
        After this, self._sftp should have a valid connection (or
        we raise an TransportError 'could not connect').

        TODO: Raise a more reasonable ConnectionFailed exception
        """
        global _connected_hosts

        idx = (self._host, self._port, self._username)
        try:
            self._sftp = _connected_hosts[idx]
            return
        except KeyError:
            pass
        
        vendor = _get_ssh_vendor()
        if vendor == 'loopback':
            sock = socket.socket()
            try:
                sock.connect((self._host, self._port))
            except socket.error, e:
                raise ConnectionError('Unable to connect to SSH host %s:%s: %s'
                                      % (self._host, self._port, e))
            self._sftp = SFTPClient(LoopbackSFTP(sock))
        elif vendor != 'none':
            try:
                sock = SFTPSubprocess(self._host, vendor, self._port,
                                      self._username)
                self._sftp = SFTPClient(sock)
            except (EOFError, paramiko.SSHException), e:
                raise ConnectionError('Unable to connect to SSH host %s:%s: %s'
                                      % (self._host, self._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'
                                      % (self._host, self._port, e))
        else:
            self._paramiko_connect()

        _connected_hosts[idx] = self._sftp

    def _paramiko_connect(self):
        global SYSTEM_HOSTKEYS, BZR_HOSTKEYS
        
        load_host_keys()

        try:
            t = paramiko.Transport((self._host, self._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' 
                                  % (self._host, self._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 SYSTEM_HOSTKEYS.has_key(self._host) and SYSTEM_HOSTKEYS[self._host].has_key(keytype):
            our_server_key = SYSTEM_HOSTKEYS[self._host][keytype]
            our_server_key_hex = paramiko.util.hexify(our_server_key.get_fingerprint())
        elif BZR_HOSTKEYS.has_key(self._host) and BZR_HOSTKEYS[self._host].has_key(keytype):
            our_server_key = BZR_HOSTKEYS[self._host][keytype]
            our_server_key_hex = paramiko.util.hexify(our_server_key.get_fingerprint())
        else:
            warning('Adding %s host key for %s: %s' % (keytype, self._host, server_key_hex))
            if not BZR_HOSTKEYS.has_key(self._host):
                BZR_HOSTKEYS[self._host] = {}
            BZR_HOSTKEYS[self._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' % \
                (self._host, our_server_key_hex, server_key_hex),
                ['Try editing %s or %s' % (filename1, filename2)])

        self._sftp_auth(t)
        
        try:
            self._sftp = t.open_sftp_client()
        except paramiko.SSHException, e:
            raise ConnectionError('Unable to start sftp client %s:%d' %
                                  (self._host, self._port), e)

    def _sftp_auth(self, 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 self._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 = self._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:
                    transport.auth_publickey(username, key)
                    return
                except paramiko.SSHException, e:
                    pass
        
        # okay, try finding id_rsa or id_dss?  (posix only)
        if self._try_pkey_auth(transport, paramiko.RSAKey, username, 'id_rsa'):
            return
        if self._try_pkey_auth(transport, paramiko.DSSKey, username, 'id_dsa'):
            return

        if self._password:
            try:
                transport.auth_password(username, self._password)
                return
            except paramiko.SSHException, e:
                pass

            # FIXME: Don't keep a password held in memory if you can help it
            #self._password = None

        # give up and ask for a password
        password = bzrlib.ui.ui_factory.get_password(
                prompt='SSH %(user)s@%(host)s password',
                user=username, host=self._host)
        try:
            transport.auth_password(username, password)
        except paramiko.SSHException, e:
            raise ConnectionError('Unable to authenticate to SSH host as %s@%s' %
                                  (username, self._host), e)

    def _try_pkey_auth(self, transport, pkey_class, username, filename):
        filename = os.path.expanduser('~/.ssh/' + filename)
        try:
            key = pkey_class.from_private_key_file(filename)
            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)
                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 _sftp_open_exclusive(self, abspath, mode=None):
        """Open a remote path exclusively.

        SFTP supports O_EXCL (SFTP_FLAG_EXCL), which fails if
        the file already exists. However it does not expose this
        at the higher level of SFTPClient.open(), so we have to
        sneak away with it.

        WARNING: This breaks the SFTPClient abstraction, so it
        could easily break against an updated version of paramiko.

        :param abspath: The remote absolute path where the file should be opened
        :param mode: The mode permissions bits for the new file
        """
        path = self._sftp._adjust_cwd(abspath)
        # mutter('sftp abspath %s => %s', abspath, path)
        attr = SFTPAttributes()
        if mode is not None:
            attr.st_mode = mode
        omode = (SFTP_FLAG_WRITE | SFTP_FLAG_CREATE 
                | SFTP_FLAG_TRUNC | SFTP_FLAG_EXCL)
        try:
            t, msg = self._sftp._request(CMD_OPEN, path, omode, attr)
            if t != CMD_HANDLE:
                raise TransportError('Expected an SFTP handle')
            handle = msg.get_string()
            return SFTPFile(self._sftp, handle, 'wb', -1)
        except (paramiko.SSHException, IOError), e:
            self._translate_io_exception(e, abspath, ': unable to open',
                failure_exc=FileExists)


# ------------- server test implementation --------------
import socket
import threading

from bzrlib.tests.stub_sftp import StubServer, StubSFTPServer

STUB_SERVER_KEY = """
-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----
"""


class SocketListener(threading.Thread):

    def __init__(self, callback):
        threading.Thread.__init__(self)
        self._callback = callback
        self._socket = socket.socket()
        self._socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self._socket.bind(('localhost', 0))
        self._socket.listen(1)
        self.port = self._socket.getsockname()[1]
        self._stop_event = threading.Event()

    def stop(self):
        # called from outside this thread
        self._stop_event.set()
        # use a timeout here, because if the test fails, the server thread may
        # never notice the stop_event.
        self.join(5.0)
        self._socket.close()

    def run(self):
        while True:
            readable, writable_unused, exception_unused = \
                select.select([self._socket], [], [], 0.1)
            if self._stop_event.isSet():
                return
            if len(readable) == 0:
                continue
            try:
                s, addr_unused = self._socket.accept()
                # because the loopback socket is inline, and transports are
                # never explicitly closed, best to launch a new thread.
                threading.Thread(target=self._callback, args=(s,)).start()
            except socket.error, x:
                sys.excepthook(*sys.exc_info())
                warning('Socket error during accept() within unit test server'
                        ' thread: %r' % x)
            except Exception, x:
                # probably a failed test; unit test thread will log the
                # failure/error
                sys.excepthook(*sys.exc_info())
                warning('Exception from within unit test server thread: %r' % 
                        x)


class SFTPServer(Server):
    """Common code for SFTP server facilities."""

    def __init__(self):
        self._original_vendor = None
        self._homedir = None
        self._server_homedir = None
        self._listener = None
        self._root = None
        self._vendor = 'none'
        # sftp server logs
        self.logs = []

    def _get_sftp_url(self, path):
        """Calculate an sftp url to this server for path."""
        return 'sftp://foo:bar@localhost:%d/%s' % (self._listener.port, path)

    def log(self, message):
        """StubServer uses this to log when a new server is created."""
        self.logs.append(message)

    def _run_server(self, s):
        ssh_server = paramiko.Transport(s)
        key_file = pathjoin(self._homedir, 'test_rsa.key')
        f = open(key_file, 'w')
        f.write(STUB_SERVER_KEY)
        f.close()
        host_key = paramiko.RSAKey.from_private_key_file(key_file)
        ssh_server.add_server_key(host_key)
        server = StubServer(self)
        ssh_server.set_subsystem_handler('sftp', paramiko.SFTPServer,
                                         StubSFTPServer, root=self._root,
                                         home=self._server_homedir)
        event = threading.Event()
        ssh_server.start_server(event, server)
        event.wait(5.0)
    
    def setUp(self):
        global _ssh_vendor
        self._original_vendor = _ssh_vendor
        _ssh_vendor = self._vendor
        if sys.platform == 'win32':
            # Win32 needs to use the UNICODE api
            self._homedir = getcwd()
        else:
            # But Linux SFTP servers should just deal in bytestreams
            self._homedir = os.getcwd()
        if self._server_homedir is None:
            self._server_homedir = self._homedir
        self._root = '/'
        if sys.platform == 'win32':
            self._root = ''
        self._listener = SocketListener(self._run_server)
        self._listener.setDaemon(True)
        self._listener.start()

    def tearDown(self):
        """See bzrlib.transport.Server.tearDown."""
        global _ssh_vendor
        self._listener.stop()
        _ssh_vendor = self._original_vendor

    def get_bogus_url(self):
        """See bzrlib.transport.Server.get_bogus_url."""
        # this is chosen to try to prevent trouble with proxies, wierd dns, etc
        # we bind a random socket, so that we get a guaranteed unused port
        # we just never listen on that port
        s = socket.socket()
        s.bind(('localhost', 0))
        return 'sftp://%s:%s/' % s.getsockname()


class SFTPFullAbsoluteServer(SFTPServer):
    """A test server for sftp transports, using absolute urls and ssh."""

    def get_url(self):
        """See bzrlib.transport.Server.get_url."""
        return self._get_sftp_url(urlutils.escape(self._homedir[1:]))


class SFTPServerWithoutSSH(SFTPServer):
    """An SFTP server that uses a simple TCP socket pair rather than SSH."""

    def __init__(self):
        super(SFTPServerWithoutSSH, self).__init__()
        self._vendor = 'loopback'

    def _run_server(self, sock):
        class FakeChannel(object):
            def get_transport(self):
                return self
            def get_log_channel(self):
                return 'paramiko'
            def get_name(self):
                return '1'
            def get_hexdump(self):
                return False
            def close(self):
                pass

        server = paramiko.SFTPServer(FakeChannel(), 'sftp', StubServer(self), StubSFTPServer,
                                     root=self._root, home=self._server_homedir)
        try:
            server.start_subsystem('sftp', None, sock)
        except socket.error, e:
            if (len(e.args) > 0) and (e.args[0] == errno.EPIPE):
                # it's okay for the client to disconnect abruptly
                # (bug in paramiko 1.6: it should absorb this exception)
                pass
            else:
                raise
        except Exception, e:
            import sys; sys.stderr.write('\nEXCEPTION %r\n\n' % e.__class__)
        server.finish_subsystem()


class SFTPAbsoluteServer(SFTPServerWithoutSSH):
    """A test server for sftp transports, using absolute urls."""

    def get_url(self):
        """See bzrlib.transport.Server.get_url."""
        if sys.platform == 'win32':
            return self._get_sftp_url(urlutils.escape(self._homedir))
        else:
            return self._get_sftp_url(urlutils.escape(self._homedir[1:]))


class SFTPHomeDirServer(SFTPServerWithoutSSH):
    """A test server for sftp transports, using homedir relative urls."""

    def get_url(self):
        """See bzrlib.transport.Server.get_url."""
        return self._get_sftp_url("~/")


class SFTPSiblingAbsoluteServer(SFTPAbsoluteServer):
    """A test servere for sftp transports, using absolute urls to non-home."""

    def setUp(self):
        self._server_homedir = '/dev/noone/runs/tests/here'
        super(SFTPSiblingAbsoluteServer, self).setUp()


def get_test_permutations():
    """Return the permutations to be used in testing."""
    return [(SFTPTransport, SFTPAbsoluteServer),
            (SFTPTransport, SFTPHomeDirServer),
            (SFTPTransport, SFTPSiblingAbsoluteServer),
            ]