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# protocol.py -- Shared parts of the git protocols
# Copyright (C) 2008 John Carr <john.carr@unrouted.co.uk>
# Copyright (C) 2008-2012 Jelmer Vernooij <jelmer@samba.org>
#
# Dulwich is dual-licensed under the Apache License, Version 2.0 and the GNU
# General Public License as public by the Free Software Foundation; version 2.0
# or (at your option) any later version. You can redistribute it and/or
# modify it under the terms of either of these two licenses.
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# You should have received a copy of the licenses; if not, see
# <http://www.gnu.org/licenses/> for a copy of the GNU General Public License
# and <http://www.apache.org/licenses/LICENSE-2.0> for a copy of the Apache
# License, Version 2.0.
#
"""Generic functions for talking the git smart server protocol."""
from io import BytesIO
from os import (
SEEK_END,
)
import socket
import dulwich
from dulwich.errors import (
HangupException,
GitProtocolError,
)
TCP_GIT_PORT = 9418
ZERO_SHA = b"0" * 40
SINGLE_ACK = 0
MULTI_ACK = 1
MULTI_ACK_DETAILED = 2
# pack data
SIDE_BAND_CHANNEL_DATA = 1
# progress messages
SIDE_BAND_CHANNEL_PROGRESS = 2
# fatal error message just before stream aborts
SIDE_BAND_CHANNEL_FATAL = 3
CAPABILITY_DEEPEN_SINCE = b'deepen-since'
CAPABILITY_DEEPEN_NOT = b'deepen-not'
CAPABILITY_DEEPEN_RELATIVE = b'deepen-relative'
CAPABILITY_DELETE_REFS = b'delete-refs'
CAPABILITY_INCLUDE_TAG = b'include-tag'
CAPABILITY_MULTI_ACK = b'multi_ack'
CAPABILITY_MULTI_ACK_DETAILED = b'multi_ack_detailed'
CAPABILITY_NO_DONE = b'no-done'
CAPABILITY_NO_PROGRESS = b'no-progress'
CAPABILITY_OFS_DELTA = b'ofs-delta'
CAPABILITY_QUIET = b'quiet'
CAPABILITY_REPORT_STATUS = b'report-status'
CAPABILITY_SHALLOW = b'shallow'
CAPABILITY_SIDE_BAND = b'side-band'
CAPABILITY_SIDE_BAND_64K = b'side-band-64k'
CAPABILITY_THIN_PACK = b'thin-pack'
CAPABILITY_AGENT = b'agent'
CAPABILITY_SYMREF = b'symref'
# Magic ref that is used to attach capabilities to when
# there are no refs. Should always be ste to ZERO_SHA.
CAPABILITIES_REF = b'capabilities^{}'
COMMON_CAPABILITIES = [
CAPABILITY_OFS_DELTA,
CAPABILITY_SIDE_BAND,
CAPABILITY_SIDE_BAND_64K,
CAPABILITY_AGENT,
CAPABILITY_NO_PROGRESS]
KNOWN_UPLOAD_CAPABILITIES = set(COMMON_CAPABILITIES + [
CAPABILITY_THIN_PACK,
CAPABILITY_MULTI_ACK,
CAPABILITY_MULTI_ACK_DETAILED,
CAPABILITY_INCLUDE_TAG,
CAPABILITY_DEEPEN_SINCE,
CAPABILITY_SYMREF,
CAPABILITY_SHALLOW,
CAPABILITY_DEEPEN_NOT,
CAPABILITY_DEEPEN_RELATIVE,
])
KNOWN_RECEIVE_CAPABILITIES = set(COMMON_CAPABILITIES + [
CAPABILITY_REPORT_STATUS])
def agent_string():
return ('dulwich/%d.%d.%d' % dulwich.__version__).encode('ascii')
def capability_agent():
return CAPABILITY_AGENT + b'=' + agent_string()
def capability_symref(from_ref, to_ref):
return CAPABILITY_SYMREF + b'=' + from_ref + b':' + to_ref
def extract_capability_names(capabilities):
return set(parse_capability(c)[0] for c in capabilities)
def parse_capability(capability):
parts = capability.split('=', 1)
if len(parts) == 1:
return (parts[0], None)
return tuple(parts)
COMMAND_DEEPEN = b'deepen'
COMMAND_SHALLOW = b'shallow'
COMMAND_UNSHALLOW = b'unshallow'
COMMAND_DONE = b'done'
COMMAND_WANT = b'want'
COMMAND_HAVE = b'have'
class ProtocolFile(object):
"""A dummy file for network ops that expect file-like objects."""
def __init__(self, read, write):
self.read = read
self.write = write
def tell(self):
pass
def close(self):
pass
def pkt_line(data):
"""Wrap data in a pkt-line.
:param data: The data to wrap, as a str or None.
:return: The data prefixed with its length in pkt-line format; if data was
None, returns the flush-pkt ('0000').
"""
if data is None:
return b'0000'
return ('%04x' % (len(data) + 4)).encode('ascii') + data
class Protocol(object):
"""Class for interacting with a remote git process over the wire.
Parts of the git wire protocol use 'pkt-lines' to communicate. A pkt-line
consists of the length of the line as a 4-byte hex string, followed by the
payload data. The length includes the 4-byte header. The special line
'0000' indicates the end of a section of input and is called a 'flush-pkt'.
For details on the pkt-line format, see the cgit distribution:
Documentation/technical/protocol-common.txt
"""
def __init__(self, read, write, close=None, report_activity=None):
self.read = read
self.write = write
self._close = close
self.report_activity = report_activity
self._readahead = None
def close(self):
if self._close:
self._close()
def __enter__(self):
return self
def __exit__(self, exc_type, exc_val, exc_tb):
self.close()
def read_pkt_line(self):
"""Reads a pkt-line from the remote git process.
This method may read from the readahead buffer; see unread_pkt_line.
:return: The next string from the stream, without the length prefix, or
None for a flush-pkt ('0000').
"""
if self._readahead is None:
read = self.read
else:
read = self._readahead.read
self._readahead = None
try:
sizestr = read(4)
if not sizestr:
raise HangupException()
size = int(sizestr, 16)
if size == 0:
if self.report_activity:
self.report_activity(4, 'read')
return None
if self.report_activity:
self.report_activity(size, 'read')
pkt_contents = read(size-4)
except socket.error as e:
raise GitProtocolError(e)
else:
if len(pkt_contents) + 4 != size:
raise GitProtocolError(
'Length of pkt read %04x does not match length prefix %04x'
% (len(pkt_contents) + 4, size))
return pkt_contents
def eof(self):
"""Test whether the protocol stream has reached EOF.
Note that this refers to the actual stream EOF and not just a
flush-pkt.
:return: True if the stream is at EOF, False otherwise.
"""
try:
next_line = self.read_pkt_line()
except HangupException:
return True
self.unread_pkt_line(next_line)
return False
def unread_pkt_line(self, data):
"""Unread a single line of data into the readahead buffer.
This method can be used to unread a single pkt-line into a fixed
readahead buffer.
:param data: The data to unread, without the length prefix.
:raise ValueError: If more than one pkt-line is unread.
"""
if self._readahead is not None:
raise ValueError('Attempted to unread multiple pkt-lines.')
self._readahead = BytesIO(pkt_line(data))
def read_pkt_seq(self):
"""Read a sequence of pkt-lines from the remote git process.
:return: Yields each line of data up to but not including the next
flush-pkt.
"""
pkt = self.read_pkt_line()
while pkt:
yield pkt
pkt = self.read_pkt_line()
def write_pkt_line(self, line):
"""Sends a pkt-line to the remote git process.
:param line: A string containing the data to send, without the length
prefix.
"""
try:
line = pkt_line(line)
self.write(line)
if self.report_activity:
self.report_activity(len(line), 'write')
except socket.error as e:
raise GitProtocolError(e)
def write_file(self):
"""Return a writable file-like object for this protocol."""
class ProtocolFile(object):
def __init__(self, proto):
self._proto = proto
self._offset = 0
def write(self, data):
self._proto.write(data)
self._offset += len(data)
def tell(self):
return self._offset
def close(self):
pass
return ProtocolFile(self)
def write_sideband(self, channel, blob):
"""Write multiplexed data to the sideband.
:param channel: An int specifying the channel to write to.
:param blob: A blob of data (as a string) to send on this channel.
"""
# a pktline can be a max of 65520. a sideband line can therefore be
# 65520-5 = 65515
# WTF: Why have the len in ASCII, but the channel in binary.
while blob:
self.write_pkt_line(bytes(bytearray([channel])) + blob[:65515])
blob = blob[65515:]
def send_cmd(self, cmd, *args):
"""Send a command and some arguments to a git server.
Only used for the TCP git protocol (git://).
:param cmd: The remote service to access.
:param args: List of arguments to send to remove service.
"""
self.write_pkt_line(cmd + b" " + b"".join([(a + b"\0") for a in args]))
def read_cmd(self):
"""Read a command and some arguments from the git client
Only used for the TCP git protocol (git://).
:return: A tuple of (command, [list of arguments]).
"""
line = self.read_pkt_line()
splice_at = line.find(b" ")
cmd, args = line[:splice_at], line[splice_at+1:]
assert args[-1:] == b"\x00"
return cmd, args[:-1].split(b"\0")
_RBUFSIZE = 8192 # Default read buffer size.
class ReceivableProtocol(Protocol):
"""Variant of Protocol that allows reading up to a size without blocking.
This class has a recv() method that behaves like socket.recv() in addition
to a read() method.
If you want to read n bytes from the wire and block until exactly n bytes
(or EOF) are read, use read(n). If you want to read at most n bytes from
the wire but don't care if you get less, use recv(n). Note that recv(n)
will still block until at least one byte is read.
"""
def __init__(self, recv, write, report_activity=None, rbufsize=_RBUFSIZE):
super(ReceivableProtocol, self).__init__(self.read, write,
report_activity)
self._recv = recv
self._rbuf = BytesIO()
self._rbufsize = rbufsize
def read(self, size):
# From _fileobj.read in socket.py in the Python 2.6.5 standard library,
# with the following modifications:
# - omit the size <= 0 branch
# - seek back to start rather than 0 in case some buffer has been
# consumed.
# - use SEEK_END instead of the magic number.
# Copyright (c) 2001-2010 Python Software Foundation; All Rights
# Reserved
# Licensed under the Python Software Foundation License.
# TODO: see if buffer is more efficient than cBytesIO.
assert size > 0
# Our use of BytesIO rather than lists of string objects returned by
# recv() minimizes memory usage and fragmentation that occurs when
# rbufsize is large compared to the typical return value of recv().
buf = self._rbuf
start = buf.tell()
buf.seek(0, SEEK_END)
# buffer may have been partially consumed by recv()
buf_len = buf.tell() - start
if buf_len >= size:
# Already have size bytes in our buffer? Extract and return.
buf.seek(start)
rv = buf.read(size)
self._rbuf = BytesIO()
self._rbuf.write(buf.read())
self._rbuf.seek(0)
return rv
self._rbuf = BytesIO() # reset _rbuf. we consume it via buf.
while True:
left = size - buf_len
# recv() will malloc the amount of memory given as its
# parameter even though it often returns much less data
# than that. The returned data string is short lived
# as we copy it into a BytesIO and free it. This avoids
# fragmentation issues on many platforms.
data = self._recv(left)
if not data:
break
n = len(data)
if n == size and not buf_len:
# Shortcut. Avoid buffer data copies when:
# - We have no data in our buffer.
# AND
# - Our call to recv returned exactly the
# number of bytes we were asked to read.
return data
if n == left:
buf.write(data)
del data # explicit free
break
assert n <= left, "_recv(%d) returned %d bytes" % (left, n)
buf.write(data)
buf_len += n
del data # explicit free
# assert buf_len == buf.tell()
buf.seek(start)
return buf.read()
def recv(self, size):
assert size > 0
buf = self._rbuf
start = buf.tell()
buf.seek(0, SEEK_END)
buf_len = buf.tell()
buf.seek(start)
left = buf_len - start
if not left:
# only read from the wire if our read buffer is exhausted
data = self._recv(self._rbufsize)
if len(data) == size:
# shortcut: skip the buffer if we read exactly size bytes
return data
buf = BytesIO()
buf.write(data)
buf.seek(0)
del data # explicit free
self._rbuf = buf
return buf.read(size)
def extract_capabilities(text):
"""Extract a capabilities list from a string, if present.
:param text: String to extract from
:return: Tuple with text with capabilities removed and list of capabilities
"""
if b"\0" not in text:
return text, []
text, capabilities = text.rstrip().split(b"\0")
return (text, capabilities.strip().split(b" "))
def extract_want_line_capabilities(text):
"""Extract a capabilities list from a want line, if present.
Note that want lines have capabilities separated from the rest of the line
by a space instead of a null byte. Thus want lines have the form:
want obj-id cap1 cap2 ...
:param text: Want line to extract from
:return: Tuple with text with capabilities removed and list of capabilities
"""
split_text = text.rstrip().split(b" ")
if len(split_text) < 3:
return text, []
return (b" ".join(split_text[:2]), split_text[2:])
def ack_type(capabilities):
"""Extract the ack type from a capabilities list."""
if b'multi_ack_detailed' in capabilities:
return MULTI_ACK_DETAILED
elif b'multi_ack' in capabilities:
return MULTI_ACK
return SINGLE_ACK
class BufferedPktLineWriter(object):
"""Writer that wraps its data in pkt-lines and has an independent buffer.
Consecutive calls to write() wrap the data in a pkt-line and then buffers
it until enough lines have been written such that their total length
(including length prefix) reach the buffer size.
"""
def __init__(self, write, bufsize=65515):
"""Initialize the BufferedPktLineWriter.
:param write: A write callback for the underlying writer.
:param bufsize: The internal buffer size, including length prefixes.
"""
self._write = write
self._bufsize = bufsize
self._wbuf = BytesIO()
self._buflen = 0
def write(self, data):
"""Write data, wrapping it in a pkt-line."""
line = pkt_line(data)
line_len = len(line)
over = self._buflen + line_len - self._bufsize
if over >= 0:
start = line_len - over
self._wbuf.write(line[:start])
self.flush()
else:
start = 0
saved = line[start:]
self._wbuf.write(saved)
self._buflen += len(saved)
def flush(self):
"""Flush all data from the buffer."""
data = self._wbuf.getvalue()
if data:
self._write(data)
self._len = 0
self._wbuf = BytesIO()
class PktLineParser(object):
"""Packet line parser that hands completed packets off to a callback.
"""
def __init__(self, handle_pkt):
self.handle_pkt = handle_pkt
self._readahead = BytesIO()
def parse(self, data):
"""Parse a fragment of data and call back for any completed packets.
"""
self._readahead.write(data)
buf = self._readahead.getvalue()
if len(buf) < 4:
return
while len(buf) >= 4:
size = int(buf[:4], 16)
if size == 0:
self.handle_pkt(None)
buf = buf[4:]
elif size <= len(buf):
self.handle_pkt(buf[4:size])
buf = buf[size:]
else:
break
self._readahead = BytesIO()
self._readahead.write(buf)
def get_tail(self):
"""Read back any unused data."""
return self._readahead.getvalue()

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