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Merge pull request #2 from ActiveState/Consolidated_CVE_Fixes
Consolidated CVE fixes
2 parents 09ac0a1 + d1e140f commit a37a229

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‎AUTHORS‎

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Original file line numberDiff line numberDiff line change
@@ -33,5 +33,6 @@ Contributors are:
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-Steven Whitman <ninloot _at_ gmail.com>
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-Stefan Stancu <stefan.stancu _at_ gmail.com>
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-César Izurieta <cesar _at_ caih.org>
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-Santos Gallegos <stsewd _at_ proton.me>
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Portions derived from other open source works and are clearly marked.

‎git/cmd.py‎

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@@ -4,7 +4,9 @@
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# This module is part of GitPython and is released under
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# the BSD License: http://www.opensource.org/licenses/bsd-license.php
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7-
from contextlib import contextmanager
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import contextlib
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import re
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import io
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import logging
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import os
@@ -19,6 +21,7 @@
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import threading
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from collections import OrderedDict
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from textwrap import dedent
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import mock
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from git.compat import (
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string_types,
@@ -31,7 +34,7 @@
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is_posix,
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is_win,
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)
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from git.exc import CommandError
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from git.exc import CommandError, UnsafeOptionError, UnsafeProtocolError
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from git.util import is_cygwin_git, cygpath, expand_path
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from .exc import (
@@ -59,6 +62,11 @@
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__all__ = ('Git',)
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@contextlib.contextmanager
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def nullcontext(enter_result=None):
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yield enter_result
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# ==============================================================================
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## @name Utilities
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# ------------------------------------------------------------------------------
@@ -124,6 +132,59 @@ def pump_stream(cmdline, name, stream, is_decode, handler):
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return finalizer(process)
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def _safer_popen_windows(command, shell, env=None, **kwargs):
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"""Call :class:`subprocess.Popen` on Windows but don't include a CWD in the search.
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This avoids an untrusted search path condition where a file like ``git.exe`` in a
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malicious repository would be run when GitPython operates on the repository. The
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process using GitPython may have an untrusted repository's working tree as its
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current working directory. Some operations may temporarily change to that directory
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before running a subprocess. In addition, while by default GitPython does not run
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external commands with a shell, it can be made to do so, in which case the CWD of
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the subprocess, which GitPython usually sets to a repository working tree, can
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itself be searched automatically by the shell. This wrapper covers all those cases.
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:note: This currently works by setting the ``NoDefaultCurrentDirectoryInExePath``
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environment variable during subprocess creation. It also takes care of passing
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Windows-specific process creation flags, but that is unrelated to path search.
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:note: The current implementation contains a race condition on :attr:`os.environ`.
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GitPython isn't thread-safe, but a program using it on one thread should ideally
150+
be able to mutate :attr:`os.environ` on another, without unpredictable results.
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See comments in https://github.com/gitpython-developers/GitPython/pull/1650.
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"""
153+
# CREATE_NEW_PROCESS_GROUP is needed for some ways of killing it afterwards. See:
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# https://docs.python.org/3/library/subprocess.html#subprocess.Popen.send_signal
155+
# https://docs.python.org/3/library/subprocess.html#subprocess.CREATE_NEW_PROCESS_GROUP
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creationflags = subprocess.CREATE_NO_WINDOW | subprocess.CREATE_NEW_PROCESS_GROUP
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# When using a shell, the shell is the direct subprocess, so the variable must be
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# set in its environment, to affect its search behavior. (The "1" can be any value.)
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if shell:
161+
safer_env = {} if env is None else dict(env)
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safer_env["NoDefaultCurrentDirectoryInExePath"] = "1"
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else:
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safer_env = env
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# When not using a shell, the current process does the search in a CreateProcessW
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# API call, so the variable must be set in our environment. With a shell, this is
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# unnecessary, in versions where https://github.com/python/cpython/issues/101283 is
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# patched. If not, in the rare case the ComSpec environment variable is unset, the
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# shell is searched for unsafely. Setting NoDefaultCurrentDirectoryInExePath in all
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# cases, as here, is simpler and protects against that. (The "1" can be any value.)
172+
with patch_env("NoDefaultCurrentDirectoryInExePath", "1"):
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return Popen(
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command,
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shell=shell,
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env=safer_env,
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creationflags=creationflags,
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**kwargs
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)
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if os.name == "nt":
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safer_popen = _safer_popen_windows
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else:
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safer_popen = Popen
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127188
def dashify(string):
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return string.replace('_', '-')
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@@ -144,11 +205,6 @@ def dict_to_slots_and__excluded_are_none(self, d, excluded=()):
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# value of Windows process creation flag taken from MSDN
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CREATE_NO_WINDOW = 0x08000000
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147-
## CREATE_NEW_PROCESS_GROUP is needed to allow killing it afterwards,
148-
# see https://docs.python.org/3/library/subprocess.html#subprocess.Popen.send_signal
149-
PROC_CREATIONFLAGS = (CREATE_NO_WINDOW | subprocess.CREATE_NEW_PROCESS_GROUP
150-
if is_win else 0)
151-
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153209
class Git(LazyMixin):
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@@ -171,9 +227,49 @@ class Git(LazyMixin):
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172228
_excluded_ = ('cat_file_all', 'cat_file_header', '_version_info')
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230+
re_unsafe_protocol = re.compile("(.+)::.+")
231+
174232
def __getstate__(self):
175233
return slots_to_dict(self, exclude=self._excluded_)
176234

235+
@classmethod
236+
def check_unsafe_protocols(cls, url):
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"""
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Check for unsafe protocols.
239+
Apart from the usual protocols (http, git, ssh),
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Git allows "remote helpers" that have the form `<transport>::<address>`,
241+
one of these helpers (`ext::`) can be used to invoke any arbitrary command.
242+
See:
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- https://git-scm.com/docs/gitremote-helpers
244+
- https://git-scm.com/docs/git-remote-ext
245+
"""
246+
match = cls.re_unsafe_protocol.match(url)
247+
if match:
248+
protocol = match.group(1)
249+
raise UnsafeProtocolError(
250+
"The `" + protocol + "::` protocol looks suspicious, use `allow_unsafe_protocols=True` to allow it."
251+
)
252+
253+
@classmethod
254+
def check_unsafe_options(cls, options, unsafe_options):
255+
"""
256+
Check for unsafe options.
257+
Some options that are passed to `git <command>` can be used to execute
258+
arbitrary commands, this are blocked by default.
259+
"""
260+
# Options can be of the form `foo` or `--foo bar` `--foo=bar`,
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# so we need to check if they start with "--foo" or if they are equal to "foo".
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bare_unsafe_options = [
263+
option.lstrip("-")
264+
for option in unsafe_options
265+
]
266+
for option in options:
267+
for unsafe_option, bare_option in zip(unsafe_options, bare_unsafe_options):
268+
if option.startswith(unsafe_option) or option == bare_option:
269+
raise UnsafeOptionError(
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unsafe_option +" is not allowed, use `allow_unsafe_options=True` to allow it."
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)
272+
177273
def __setstate__(self, d):
178274
dict_to_slots_and__excluded_are_none(self, d, excluded=self._excluded_)
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@@ -705,11 +801,15 @@ def execute(self, command,
705801
cmd_not_found_exception = OSError
706802
if kill_after_timeout:
707803
raise GitCommandError(command, '"kill_after_timeout" feature is not supported on Windows.')
804+
805+
# Only search PATH, not CWD. This must be in the *caller* environment. The "1" can be any value.
806+
patch_caller_env = unittest.mock.patch.dict(os.environ, {"NoDefaultCurrentDirectoryInExePath": "1"})
708807
else:
709808
if sys.version_info[0] > 2:
710809
cmd_not_found_exception = FileNotFoundError # NOQA # exists, flake8 unknown @UndefinedVariable
711810
else:
712811
cmd_not_found_exception = OSError
812+
patch_caller_env = nullcontext()
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# end handle
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715815
stdout_sink = (PIPE
@@ -721,19 +821,18 @@ def execute(self, command,
721821
log.debug("Popen(%s, cwd=%s, universal_newlines=%s, shell=%s, istream=%s)",
722822
command, cwd, universal_newlines, shell, istream_ok)
723823
try:
724-
proc = Popen(command,
725-
env=env,
726-
cwd=cwd,
727-
bufsize=-1,
728-
stdin=istream,
729-
stderr=PIPE,
730-
stdout=stdout_sink,
731-
shell=shell is not None and shell or self.USE_SHELL,
732-
close_fds=is_posix, # unsupported on windows
733-
universal_newlines=universal_newlines,
734-
creationflags=PROC_CREATIONFLAGS,
735-
**subprocess_kwargs
736-
)
824+
proc = safer_popen(
825+
command,
826+
env=env,
827+
cwd=cwd,
828+
bufsize=-1,
829+
stdin=istream,
830+
stderr=PIPE,
831+
stdout=stdout_sink,
832+
shell=shell is not None and shell or self.USE_SHELL,
833+
universal_newlines=universal_newlines,
834+
**subprocess_kwargs
835+
)
737836
except cmd_not_found_exception as err:
738837
raise GitCommandNotFound(command, err)
739838

@@ -862,7 +961,7 @@ def update_environment(self, **kwargs):
862961
del self._environment[key]
863962
return old_env
864963

865-
@contextmanager
964+
@contextlib.contextmanager
866965
def custom_environment(self, **kwargs):
867966
"""
868967
A context manager around the above ``update_environment`` method to restore the
@@ -1082,7 +1181,7 @@ def get_object_data(self, ref):
10821181
:note: not threadsafe"""
10831182
hexsha, typename, size, stream = self.stream_object_data(ref)
10841183
data = stream.read(size)
1085-
del(stream)
1184+
del (stream)
10861185
return (hexsha, typename, size, data)
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10881187
def stream_object_data(self, ref):

‎git/exc.py‎

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Original file line numberDiff line numberDiff line change
@@ -25,6 +25,14 @@ class NoSuchPathError(GitError, OSError):
2525
""" Thrown if a path could not be access by the system. """
2626

2727

28+
class UnsafeProtocolError(GitError):
29+
"""Thrown if unsafe protocols are passed without being explicitly allowed."""
30+
31+
32+
class UnsafeOptionError(GitError):
33+
"""Thrown if unsafe options are passed without being explicitly allowed."""
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35+
2836
class CommandError(UnicodeMixin, GitError):
2937
"""Base class for exceptions thrown at every stage of `Popen()` execution.
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