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# server.py -- Implementation of the server side git protocols
# Copyright (C) 2008 John Carr <john.carr@unrouted.co.uk>
#
# 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; version 2
# or (at your option) any later version of the License.
#
# 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.
"""Git smart network protocol server implementation.
For more detailed implementation on the network protocol, see the
Documentation/technical directory in the cgit distribution, and in particular:
* Documentation/technical/protocol-capabilities.txt
* Documentation/technical/pack-protocol.txt
Currently supported capabilities:
* include-tag
* thin-pack
* multi_ack_detailed
* multi_ack
* side-band-64k
* ofs-delta
* no-progress
* report-status
* delete-refs
Known capabilities that are not supported:
* shallow (http://pad.lv/909524)
"""
import collections
import os
import socket
import SocketServer
import sys
import zlib
from dulwich.errors import (
ApplyDeltaError,
ChecksumMismatch,
GitProtocolError,
NotGitRepository,
UnexpectedCommandError,
ObjectFormatException,
)
from dulwich import log_utils
from dulwich.objects import (
hex_to_sha,
)
from dulwich.pack import (
write_pack_objects,
)
from dulwich.protocol import (
BufferedPktLineWriter,
MULTI_ACK,
MULTI_ACK_DETAILED,
Protocol,
ProtocolFile,
ReceivableProtocol,
SINGLE_ACK,
TCP_GIT_PORT,
ZERO_SHA,
ack_type,
extract_capabilities,
extract_want_line_capabilities,
)
from dulwich.repo import (
Repo,
)
logger = log_utils.getLogger(__name__)
class Backend(object):
"""A backend for the Git smart server implementation."""
def open_repository(self, path):
"""Open the repository at a path.
:param path: Path to the repository
:raise NotGitRepository: no git repository was found at path
:return: Instance of BackendRepo
"""
raise NotImplementedError(self.open_repository)
class BackendRepo(object):
"""Repository abstraction used by the Git server.
Please note that the methods required here are a
subset of those provided by dulwich.repo.Repo.
"""
object_store = None
refs = None
def get_refs(self):
"""
Get all the refs in the repository
:return: dict of name -> sha
"""
raise NotImplementedError
def get_peeled(self, name):
"""Return the cached peeled value of a ref, if available.
:param name: Name of the ref to peel
:return: The peeled value of the ref. If the ref is known not point to
a tag, this will be the SHA the ref refers to. If no cached
information about a tag is available, this method may return None,
but it should attempt to peel the tag if possible.
"""
return None
def fetch_objects(self, determine_wants, graph_walker, progress,
get_tagged=None):
"""
Yield the objects required for a list of commits.
:param progress: is a callback to send progress messages to the client
:param get_tagged: Function that returns a dict of pointed-to sha -> tag
sha for including tags.
"""
raise NotImplementedError
class DictBackend(Backend):
"""Trivial backend that looks up Git repositories in a dictionary."""
def __init__(self, repos):
self.repos = repos
def open_repository(self, path):
logger.debug('Opening repository at %s', path)
try:
return self.repos[path]
except KeyError:
raise NotGitRepository(
"No git repository was found at %(path)s" % dict(path=path)
)
class FileSystemBackend(Backend):
"""Simple backend that looks up Git repositories in the local file system."""
def open_repository(self, path):
logger.debug('opening repository at %s', path)
return Repo(path)
class Handler(object):
"""Smart protocol command handler base class."""
def __init__(self, backend, proto, http_req=None):
self.backend = backend
self.proto = proto
self.http_req = http_req
self._client_capabilities = None
@classmethod
def capability_line(cls):
return " ".join(cls.capabilities())
@classmethod
def capabilities(cls):
raise NotImplementedError(cls.capabilities)
@classmethod
def innocuous_capabilities(cls):
return ("include-tag", "thin-pack", "no-progress", "ofs-delta")
@classmethod
def required_capabilities(cls):
"""Return a list of capabilities that we require the client to have."""
return []
def set_client_capabilities(self, caps):
allowable_caps = set(self.innocuous_capabilities())
allowable_caps.update(self.capabilities())
for cap in caps:
if cap not in allowable_caps:
raise GitProtocolError('Client asked for capability %s that '
'was not advertised.' % cap)
for cap in self.required_capabilities():
if cap not in caps:
raise GitProtocolError('Client does not support required '
'capability %s.' % cap)
self._client_capabilities = set(caps)
logger.info('Client capabilities: %s', caps)
def has_capability(self, cap):
if self._client_capabilities is None:
raise GitProtocolError('Server attempted to access capability %s '
'before asking client' % cap)
return cap in self._client_capabilities
class UploadPackHandler(Handler):
"""Protocol handler for uploading a pack to the server."""
def __init__(self, backend, args, proto, http_req=None,
advertise_refs=False):
Handler.__init__(self, backend, proto, http_req=http_req)
self.repo = backend.open_repository(args[0])
self._graph_walker = None
self.advertise_refs = advertise_refs
@classmethod
def capabilities(cls):
return ("multi_ack_detailed", "multi_ack", "side-band-64k", "thin-pack",
"ofs-delta", "no-progress", "include-tag")
@classmethod
def required_capabilities(cls):
return ("side-band-64k", "thin-pack", "ofs-delta")
def progress(self, message):
if self.has_capability("no-progress"):
return
self.proto.write_sideband(2, message)
def get_tagged(self, refs=None, repo=None):
"""Get a dict of peeled values of tags to their original tag shas.
:param refs: dict of refname -> sha of possible tags; defaults to all of
the backend's refs.
:param repo: optional Repo instance for getting peeled refs; defaults to
the backend's repo, if available
:return: dict of peeled_sha -> tag_sha, where tag_sha is the sha of a
tag whose peeled value is peeled_sha.
"""
if not self.has_capability("include-tag"):
return {}
if refs is None:
refs = self.repo.get_refs()
if repo is None:
repo = getattr(self.repo, "repo", None)
if repo is None:
# Bail if we don't have a Repo available; this is ok since
# clients must be able to handle if the server doesn't include
# all relevant tags.
# TODO: fix behavior when missing
return {}
tagged = {}
for name, sha in refs.iteritems():
peeled_sha = repo.get_peeled(name)
if peeled_sha != sha:
tagged[peeled_sha] = sha
return tagged
def handle(self):
write = lambda x: self.proto.write_sideband(1, x)
graph_walker = ProtocolGraphWalker(self, self.repo.object_store,
self.repo.get_peeled)
objects_iter = self.repo.fetch_objects(
graph_walker.determine_wants, graph_walker, self.progress,
get_tagged=self.get_tagged)
# Did the process short-circuit (e.g. in a stateless RPC call)? Note
# that the client still expects a 0-object pack in most cases.
if objects_iter is None:
return
self.progress("dul-daemon says what\n")
self.progress("counting objects: %d, done.\n" % len(objects_iter))
write_pack_objects(ProtocolFile(None, write), objects_iter)
self.progress("how was that, then?\n")
# we are done
self.proto.write("0000")
def _split_proto_line(line, allowed):
"""Split a line read from the wire.
:param line: The line read from the wire.
:param allowed: An iterable of command names that should be allowed.
Command names not listed below as possible return values will be
ignored. If None, any commands from the possible return values are
allowed.
:return: a tuple having one of the following forms:
('want', obj_id)
('have', obj_id)
('done', None)
(None, None) (for a flush-pkt)
:raise UnexpectedCommandError: if the line cannot be parsed into one of the
allowed return values.
"""
if not line:
fields = [None]
else:
fields = line.rstrip('\n').split(' ', 1)
command = fields[0]
if allowed is not None and command not in allowed:
raise UnexpectedCommandError(command)
try:
if len(fields) == 1 and command in ('done', None):
return (command, None)
elif len(fields) == 2 and command in ('want', 'have'):
hex_to_sha(fields[1])
return tuple(fields)
except (TypeError, AssertionError), e:
raise GitProtocolError(e)
raise GitProtocolError('Received invalid line from client: %s' % line)
class ProtocolGraphWalker(object):
"""A graph walker that knows the git protocol.
As a graph walker, this class implements ack(), next(), and reset(). It
also contains some base methods for interacting with the wire and walking
the commit tree.
The work of determining which acks to send is passed on to the
implementation instance stored in _impl. The reason for this is that we do
not know at object creation time what ack level the protocol requires. A
call to set_ack_level() is required to set up the implementation, before any
calls to next() or ack() are made.
"""
def __init__(self, handler, object_store, get_peeled):
self.handler = handler
self.store = object_store
self.get_peeled = get_peeled
self.proto = handler.proto
self.http_req = handler.http_req
self.advertise_refs = handler.advertise_refs
self._wants = []
self._cached = False
self._cache = []
self._cache_index = 0
self._impl = None
def determine_wants(self, heads):
"""Determine the wants for a set of heads.
The given heads are advertised to the client, who then specifies which
refs he wants using 'want' lines. This portion of the protocol is the
same regardless of ack type, and in fact is used to set the ack type of
the ProtocolGraphWalker.
:param heads: a dict of refname->SHA1 to advertise
:return: a list of SHA1s requested by the client
"""
if not heads:
# The repo is empty, so short-circuit the whole process.
self.proto.write_pkt_line(None)
return None
values = set(heads.itervalues())
if self.advertise_refs or not self.http_req:
for i, (ref, sha) in enumerate(sorted(heads.iteritems())):
line = "%s %s" % (sha, ref)
if not i:
line = "%s\x00%s" % (line, self.handler.capability_line())
self.proto.write_pkt_line("%s\n" % line)
peeled_sha = self.get_peeled(ref)
if peeled_sha != sha:
self.proto.write_pkt_line('%s %s^{}\n' %
(peeled_sha, ref))
# i'm done..
self.proto.write_pkt_line(None)
if self.advertise_refs:
return None
# Now client will sending want want want commands
want = self.proto.read_pkt_line()
if not want:
return []
line, caps = extract_want_line_capabilities(want)
self.handler.set_client_capabilities(caps)
self.set_ack_type(ack_type(caps))
allowed = ('want', None)
command, sha = _split_proto_line(line, allowed)
want_revs = []
while command != None:
if sha not in values:
raise GitProtocolError(
'Client wants invalid object %s' % sha)
want_revs.append(sha)
command, sha = self.read_proto_line(allowed)
self.set_wants(want_revs)
if self.http_req and self.proto.eof():
# The client may close the socket at this point, expecting a
# flush-pkt from the server. We might be ready to send a packfile at
# this point, so we need to explicitly short-circuit in this case.
return None
return want_revs
def ack(self, have_ref):
return self._impl.ack(have_ref)
def reset(self):
self._cached = True
self._cache_index = 0
def next(self):
if not self._cached:
if not self._impl and self.http_req:
return None
return self._impl.next()
self._cache_index += 1
if self._cache_index > len(self._cache):
return None
return self._cache[self._cache_index]
def read_proto_line(self, allowed):
"""Read a line from the wire.
:param allowed: An iterable of command names that should be allowed.
:return: A tuple of (command, value); see _split_proto_line.
:raise GitProtocolError: If an error occurred reading the line.
"""
return _split_proto_line(self.proto.read_pkt_line(), allowed)
def send_ack(self, sha, ack_type=''):
if ack_type:
ack_type = ' %s' % ack_type
self.proto.write_pkt_line('ACK %s%s\n' % (sha, ack_type))
def send_nak(self):
self.proto.write_pkt_line('NAK\n')
def set_wants(self, wants):
self._wants = wants
def _is_satisfied(self, haves, want, earliest):
"""Check whether a want is satisfied by a set of haves.
A want, typically a branch tip, is "satisfied" only if there exists a
path back from that want to one of the haves.
:param haves: A set of commits we know the client has.
:param want: The want to check satisfaction for.
:param earliest: A timestamp beyond which the search for haves will be
terminated, presumably because we're searching too far down the
wrong branch.
"""
o = self.store[want]
pending = collections.deque([o])
while pending:
commit = pending.popleft()
if commit.id in haves:
return True
if commit.type_name != "commit":
# non-commit wants are assumed to be satisfied
continue
for parent in commit.parents:
parent_obj = self.store[parent]
# TODO: handle parents with later commit times than children
if parent_obj.commit_time >= earliest:
pending.append(parent_obj)
return False
def all_wants_satisfied(self, haves):
"""Check whether all the current wants are satisfied by a set of haves.
:param haves: A set of commits we know the client has.
:note: Wants are specified with set_wants rather than passed in since
in the current interface they are determined outside this class.
"""
haves = set(haves)
earliest = min([self.store[h].commit_time for h in haves])
for want in self._wants:
if not self._is_satisfied(haves, want, earliest):
return False
return True
def set_ack_type(self, ack_type):
impl_classes = {
MULTI_ACK: MultiAckGraphWalkerImpl,
MULTI_ACK_DETAILED: MultiAckDetailedGraphWalkerImpl,
SINGLE_ACK: SingleAckGraphWalkerImpl,
}
self._impl = impl_classes[ack_type](self)
_GRAPH_WALKER_COMMANDS = ('have', 'done', None)
class SingleAckGraphWalkerImpl(object):
"""Graph walker implementation that speaks the single-ack protocol."""
def __init__(self, walker):
self.walker = walker
self._sent_ack = False
def ack(self, have_ref):
if not self._sent_ack:
self.walker.send_ack(have_ref)
self._sent_ack = True
def next(self):
command, sha = self.walker.read_proto_line(_GRAPH_WALKER_COMMANDS)
if command in (None, 'done'):
if not self._sent_ack:
self.walker.send_nak()
return None
elif command == 'have':
return sha
class MultiAckGraphWalkerImpl(object):
"""Graph walker implementation that speaks the multi-ack protocol."""
def __init__(self, walker):
self.walker = walker
self._found_base = False
self._common = []
def ack(self, have_ref):
self._common.append(have_ref)
if not self._found_base:
self.walker.send_ack(have_ref, 'continue')
if self.walker.all_wants_satisfied(self._common):
self._found_base = True
# else we blind ack within next
def next(self):
while True:
command, sha = self.walker.read_proto_line(_GRAPH_WALKER_COMMANDS)
if command is None:
self.walker.send_nak()
# in multi-ack mode, a flush-pkt indicates the client wants to
# flush but more have lines are still coming
continue
elif command == 'done':
# don't nak unless no common commits were found, even if not
# everything is satisfied
if self._common:
self.walker.send_ack(self._common[-1])
else:
self.walker.send_nak()
return None
elif command == 'have':
if self._found_base:
# blind ack
self.walker.send_ack(sha, 'continue')
return sha
class MultiAckDetailedGraphWalkerImpl(object):
"""Graph walker implementation speaking the multi-ack-detailed protocol."""
def __init__(self, walker):
self.walker = walker
self._found_base = False
self._common = []
def ack(self, have_ref):
self._common.append(have_ref)
if not self._found_base:
self.walker.send_ack(have_ref, 'common')
if self.walker.all_wants_satisfied(self._common):
self._found_base = True
self.walker.send_ack(have_ref, 'ready')
# else we blind ack within next
def next(self):
while True:
command, sha = self.walker.read_proto_line(_GRAPH_WALKER_COMMANDS)
if command is None:
self.walker.send_nak()
if self.walker.http_req:
return None
continue
elif command == 'done':
# don't nak unless no common commits were found, even if not
# everything is satisfied
if self._common:
self.walker.send_ack(self._common[-1])
else:
self.walker.send_nak()
return None
elif command == 'have':
if self._found_base:
# blind ack; can happen if the client has more requests
# inflight
self.walker.send_ack(sha, 'ready')
return sha
class ReceivePackHandler(Handler):
"""Protocol handler for downloading a pack from the client."""
def __init__(self, backend, args, proto, http_req=None,
advertise_refs=False):
Handler.__init__(self, backend, proto, http_req=http_req)
self.repo = backend.open_repository(args[0])
self.advertise_refs = advertise_refs
@classmethod
def capabilities(cls):
return ("report-status", "delete-refs", "side-band-64k")
def _apply_pack(self, refs):
all_exceptions = (IOError, OSError, ChecksumMismatch, ApplyDeltaError,
AssertionError, socket.error, zlib.error,
ObjectFormatException)
status = []
# TODO: more informative error messages than just the exception string
try:
recv = getattr(self.proto, "recv", None)
p = self.repo.object_store.add_thin_pack(self.proto.read, recv)
status.append(('unpack', 'ok'))
except all_exceptions, e:
status.append(('unpack', str(e).replace('\n', '')))
# The pack may still have been moved in, but it may contain broken
# objects. We trust a later GC to clean it up.
for oldsha, sha, ref in refs:
ref_status = 'ok'
try:
if sha == ZERO_SHA:
if not 'delete-refs' in self.capabilities():
raise GitProtocolError(
'Attempted to delete refs without delete-refs '
'capability.')
try:
del self.repo.refs[ref]
except all_exceptions:
ref_status = 'failed to delete'
else:
try:
self.repo.refs[ref] = sha
except all_exceptions:
ref_status = 'failed to write'
except KeyError, e:
ref_status = 'bad ref'
status.append((ref, ref_status))
return status
def _report_status(self, status):
if self.has_capability('side-band-64k'):
writer = BufferedPktLineWriter(
lambda d: self.proto.write_sideband(1, d))
write = writer.write
def flush():
writer.flush()
self.proto.write_pkt_line(None)
else:
write = self.proto.write_pkt_line
flush = lambda: None
for name, msg in status:
if name == 'unpack':
write('unpack %s\n' % msg)
elif msg == 'ok':
write('ok %s\n' % name)
else:
write('ng %s %s\n' % (name, msg))
write(None)
flush()
def handle(self):
refs = sorted(self.repo.get_refs().iteritems())
if self.advertise_refs or not self.http_req:
if refs:
self.proto.write_pkt_line(
"%s %s\x00%s\n" % (refs[0][1], refs[0][0],
self.capability_line()))
for i in range(1, len(refs)):
ref = refs[i]
self.proto.write_pkt_line("%s %s\n" % (ref[1], ref[0]))
else:
self.proto.write_pkt_line("%s capabilities^{}\0%s" % (
ZERO_SHA, self.capability_line()))
self.proto.write("0000")
if self.advertise_refs:
return
client_refs = []
ref = self.proto.read_pkt_line()
# if ref is none then client doesnt want to send us anything..
if ref is None:
return
ref, caps = extract_capabilities(ref)
self.set_client_capabilities(caps)
# client will now send us a list of (oldsha, newsha, ref)
while ref:
client_refs.append(ref.split())
ref = self.proto.read_pkt_line()
# backend can now deal with this refs and read a pack using self.read
status = self._apply_pack(client_refs)
# when we have read all the pack from the client, send a status report
# if the client asked for it
if self.has_capability('report-status'):
self._report_status(status)
# Default handler classes for git services.
DEFAULT_HANDLERS = {
'git-upload-pack': UploadPackHandler,
'git-receive-pack': ReceivePackHandler,
}
class TCPGitRequestHandler(SocketServer.StreamRequestHandler):
def __init__(self, handlers, *args, **kwargs):
self.handlers = handlers
SocketServer.StreamRequestHandler.__init__(self, *args, **kwargs)
def handle(self):
proto = ReceivableProtocol(self.connection.recv, self.wfile.write)
command, args = proto.read_cmd()
logger.info('Handling %s request, args=%s', command, args)
cls = self.handlers.get(command, None)
if not callable(cls):
raise GitProtocolError('Invalid service %s' % command)
h = cls(self.server.backend, args, proto)
h.handle()
class TCPGitServer(SocketServer.TCPServer):
allow_reuse_address = True
serve = SocketServer.TCPServer.serve_forever
def _make_handler(self, *args, **kwargs):
return TCPGitRequestHandler(self.handlers, *args, **kwargs)
def __init__(self, backend, listen_addr, port=TCP_GIT_PORT, handlers=None):
self.handlers = dict(DEFAULT_HANDLERS)
if handlers is not None:
self.handlers.update(handlers)
self.backend = backend
logger.info('Listening for TCP connections on %s:%d', listen_addr, port)
SocketServer.TCPServer.__init__(self, (listen_addr, port),
self._make_handler)
def verify_request(self, request, client_address):
logger.info('Handling request from %s', client_address)
return True
def handle_error(self, request, client_address):
logger.exception('Exception happened during processing of request '
'from %s', client_address)
def main(argv=sys.argv):
"""Entry point for starting a TCP git server."""
if len(argv) > 1:
gitdir = argv[1]
else:
gitdir = '.'
log_utils.default_logging_config()
backend = DictBackend({'/': Repo(gitdir)})
server = TCPGitServer(backend, 'localhost')
server.serve_forever()
def serve_command(handler_cls, argv=sys.argv, backend=None, inf=sys.stdin,
outf=sys.stdout):
"""Serve a single command.
This is mostly useful for the implementation of commands used by e.g. git+ssh.
:param handler_cls: `Handler` class to use for the request
:param argv: execv-style command-line arguments. Defaults to sys.argv.
:param backend: `Backend` to use
:param inf: File-like object to read from, defaults to standard input.
:param outf: File-like object to write to, defaults to standard output.
:return: Exit code for use with sys.exit. 0 on success, 1 on failure.
"""
if backend is None:
backend = FileSystemBackend()
def send_fn(data):
outf.write(data)
outf.flush()
proto = Protocol(inf.read, send_fn)
handler = handler_cls(backend, argv[1:], proto)
# FIXME: Catch exceptions and write a single-line summary to outf.
handler.handle()
return 0
def generate_info_refs(repo):
"""Generate an info refs file."""
refs = repo.get_refs()
for name in sorted(refs.iterkeys()):
# get_refs() includes HEAD as a special case, but we don't want to
# advertise it
if name == 'HEAD':
continue
sha = refs[name]
o = repo.object_store[sha]
if not o:
continue
yield '%s\t%s\n' % (sha, name)
peeled_sha = repo.get_peeled(name)
if peeled_sha != sha:
yield '%s\t%s^{}\n' % (peeled_sha, name)
def generate_objects_info_packs(repo):
"""Generate an index for for packs."""
for pack in repo.object_store.packs:
yield 'P pack-%s.pack\n' % pack.name()
def update_server_info(repo):
"""Generate server info for dumb file access.
This generates info/refs and objects/info/packs,
similar to "git update-server-info".
"""
repo._put_named_file(os.path.join('info', 'refs'),
"".join(generate_info_refs(repo)))
repo._put_named_file(os.path.join('objects', 'info', 'packs'),
"".join(generate_objects_info_packs(repo)))
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