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Fix two remaining Windows untrusted search path cases #1792

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merged 16 commits into from
Jan 10, 2024

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@EliahKagan EliahKagan commented Jan 10, 2024

This fixes CVE-2024-22190.

Although #1636 caused GitPython to avoid using an untrusted search path on Windows under the most typical circumstances, it turns out that some cases remained. I believe only two remain at this time. This pull request fixes those. The CI status on all commits appears to be as I expected and intended.

This vulnerability was reported privately, initially without a full public writeup, since I wanted to get the pull request out as coordinated/requested, without extra delays. A summary of the vulnerability this fixes is now available in the CVE-2024-22190 advisory. Further information about these changes is present in the commit messages. For the benefit of future readers, I have also since added some more information below, lightly adapted from my original disclosure.


I have found that the fix for CVE-2023-40590 (#1635) that I contributed in #1636 was unfortunately incomplete, missing two cases.

When git is run with a shell, setting the NoDefaultCurrentDirectoryInExePath environment variable in the caller's environment is insufficient, because the shell subprocess is what performs the path search. When a shell is used, the child process's environment needs to have that variable set. This does not happen automatically, because while the env dict is based on os.environ, it is created before NoDefaultCurrentDirectoryInExePath is set in the caller environment. Omitting that variable from the child process's environment was intentional, to avoid modifying the operation of child processes more than necessary. (git itself does not need that variable to be set to avoid looking in the current directory to run its own subprocesses, including custom commands.) But it has to be done when a shell is used.

In addition, when GitPython uses bash.exe to run hooks, it does not do anything to avoid finding and running bash.exe in the current directory, which may be the working tree of an untrusted repository. Because in some reasonable workflows one checks out a branch from an untrusted remote to review it, and such a branch could contain a malicious bash.exe, this is exploitable. The description of CVE-2023-40590 had mentioned "And there are other commands executed that should probably be aware of this problem," but I had not given enough attention to that point when working on the fix, nor recognized its full ramifications.

Historically there have been other places in GitPython where a subprocess was created insecurely on Windows, but I believe that is no longer the case. The call to taskkill was removed (#1754), and a call to ps does not occur on Windows because it is part of the kill_after_timeout feature of Git.execute (#1756, #1761). This is not true of the test suite, but when running tests, a more trusted environment can reasonably be assumed: people trust the directory out of which they are intentionally running the test suite, and I don't think any test cases attempt git operations directly in /tmp anymore, as opposed to a subdirectory (#1744, #1759). Therefore I believe these are the only places that need to be changed. I searched for the names of all subprocess module functions and I did not find other problematic calls.

The shell=True bug was not detected before, due to a combination of two flaws in the regression tests I wrote in #1636 for CVE-2023-40590. First, I did not commit a test with shell=True. Second, although I had also tried it locally with shell=True, the test contained a shortcoming that prevented it from revealing the vulnerability in that case. It entered a new temporary directory with an impostor git.exe in it. But when shell=True, the relevant CWD is that of the cmd.exe shell subprocess, which was the rorepo working tree rather than the GitPython process's CWD. My patch clarifies the test, creating a repository explicitly so that all the test logic is plain, and it parameterizes the test to cover substantially more cases, including when the devious git.exe is in the repository and git is run with a shell.

I have likewise undertaken efforts to make the newly introduced bash.exe impostor test robust, tried it out with each of the WinBashStatus cases, and set up the impostor scenario in a way that allows the effect to be observed whether or not a real bash.exe is available and whether or not it is usable.

To avoid code duplication, make intent clearer, and make it easier to avoid introducing new untrusted search path bugs, this patch extracts both the shell and non-shell logic for preventing such bugs to a safer_popen function that can be used like Popen with no special forethought. This function also documents the relevant issues, including the strange but important distinction on Windows between shell and non-shell executable search behavior (i.e., why facilities such as shutil.which or the external where command often don't do what we need, on Windows). Having this in one place should also aid in future improvements to the technique used, such as to mitigate or eliminate the race condition on os.environ that irwand commented about in #1650. On non-Windows systems, safer_popen is simply an alias for Popen.

Because Git.USE_SHELL = True was useful for suppressing undesired console windows in graphical applications on Windows (#126, 1c2dd54, #360) prior to 2.0.8 (0d93908, #469), and is only much more recently longer documented as recommended for that (#1781, #1782, #1787), it is likely that a significant minority of applications use it on Windows. Searching on GitHub, and the web more broadly, turns up some uses and makes me think this may be so. In contrast, I doubt many people intentionally use GitPython to run hooks. But this happens automatically if it is used in a repository with a pre-commit hook enabled.

This adds a test_it_executes_git_not_from_cwd case for shell=True.
(This case also gives the command as a string, so the test need not
be further special-cased for non-Windows systems, where argument
lists aren't accepted with shell=True.)

The test did not attempt to cover the shell=True case before,
because I had erroneously assumed it worked similarity. It is
actually very different, because when a shell is used, both the
shell and the command the shell runs must be found and executed,
and because the process creation GitPython performs is that of the
shell process, with the state of the shell process being what is
relevant to how the path search is done for the git (or other)
command.

The code change here does not itself demonstrate that the test is
broken for shell=True, because that case passes. However, manually
undoing the fix in cmd.py for CVE-2023-40590, which as expected
causes the preexisting (implicitly shell=False case) to fail, does
*not* cause the new shell=True case to fail. That case passes!

That passing result in the absence of a fix for CVE-2023-40590 is
erroneous, because the cmd.exe shell does search the CWD first when
nothing has been done to prevent it.
This shows that CVE-2023-40590 is only partially patched. This
commit does not fix the vulnerbility, only the test.

The problem is that, when shell=True, the environment of the shell
subprocess, instead of the GitPython process, determines whether
searching for the "git" command will use the current directory.
Currently NoDefaultCurrentDirectoryInExePath is set only in the
current process, and this is done after the environment for the
subprocess (env) is computed. So when git is an indirect subprocess
due to shell=True, Windows still checks a CWD when looking it up.

(Note that this should not be a problem for indirect subprocesses
started by git itself. When a standard git command is implemented
as an external executable, when git runs a custom command, and when
one git command delegates some of its work to another -- e.g.
"git clone" running git-remote-https -- Git for Windows already
does not search the current directory. Custom git commands that
start their own git subprocesses could have an analogous path
search bug, but this would be separate from the bug in GitPython.)

This is an exploitable vulnerability in GitPython. Although
shell=True is rarer and inherently less secure than the default of
shell=False, it still ought to avoid automatically running an
executable that may exist only due to having been cloned as part of
an untrusted repository. In addition, historically programs on
Windows had sometimes used shell=True as a workaround for console
windows being displayed for subprocesses, and some such code may
still be in use.

Furthermore, even when GitPython's current working directory is
outside the repository being worked on, the Git object in a Repo
instance's "git" attribute holds the repository directory as its
"_working_dir" attribute, which Git.execute consults to determine
the value of "cwd" to pass to subprocess.Popen. When the created
direct subprocess is really a shell, this is the CWD where git.exe
is looked for before searching PATH directories.

This is also why previous, more limited testing (including
accompanying manual testing with shell=True) didn't discover the
bug. Even when modified to test with shell=True, the old test had
the "impostor" git.exe in the GitPython process's own current
directory (which was changed to a temporary directory for the test,
where the "impostor" was created, but this was separate from the
working tree of the self.git repository). This was effective for
the shell=False case, but not the shell=True case where the
impostor would be found and run in the repository directory even
when it differs from the GitPython process's CWD.
In most cases they will be the same, but WINDIR may be absent (or
have a different value?) in rare cases.

The practical reason it matters in GitPython's tests is that tox
automatically passes SystemRoot through to environments on Windows.
By using pathlib.Path instead of os.path functions.
On Python versions for which python/cpython#101283 is not patched,
using Popen with shell=True can find cmd.exe in the current
directory on Windows, in the rare case that the ComSpec environment
variable is not defined.

This is not necessarily worth addressing, because it is a bug in
CPython rahter than GitPython, because that bug has been patched,
and because it is very rare that ComSpec is undefined. However:

- Changing the code to avoid it would also make that code simpler.
- Patched versions of Python <=3.9 don't have python.org builds.

This commit just expands the test to add cases where a repository
also has a file cmd.exe and where ComSpec is undefined, showing
that this case is not covered.
This covers the rare unpatched python/cpython#101283 case the
previous commit added tests for, that only applies in the unusual
situation that the ComSpec environment variable is unset and an old
build (but this includes downloadable builds and current
actions/setup-python builds) of Python <=3.9 for Windows is in use.

The main benefit of this change is really to slightly simplify the
code under test. (It might even be justified to remove the
use_shell_impostor=True test cases at some point.)
This shows that run_commit_hook is vulnerable to an untrusted
search path bug on Windows, when running script hooks: bash.exe is
run without setting NoDefaultCurrentDirectoryInExePath or otherwise
excluding the current directory from the path search.

The new test uses a non-bare repo, even though the surrounding
tests use bare repos. Although the test also works if the repo is
initialized with `Repo.init(rw_dir, bare=True)`, using a bare repo
would obscure how the bug this test reveals would typically be
exploited, where a command that uses a hook is run after a
malicious bash.exe is checked out into the working tree from an
untrusted branch.

Running hooks that are themselves provided by an untrusted
repository or branch is of course never safe. If an attacker can
deceive a user into doing that, then this vulnerability is not
needed. Instead, an attack that leverages this untrusted search
path vulnerability would most likely be of roughly this form:

1. The user clones a trusted repository and installs hooks.
2. A malicious party offers a contribution to the project.
3. The user checks out the malicious party's untrusted branch.
4. The user performs an action that runs a hook.

The hook the user runs is still trusted, but it runs with the
malicious bash.exe found in the current directory (which is the
working tree or perhaps some subdirectory of it).

The test added in this commit should, if possible, be improved to
be able to run and detect the bug (or its absence) even when bash
is absent from the Windows system and, preferably, also even when
the WSL bash.exe is present but no WSL distribution is installed.
This uses the same NoDefaultCurrentDirectoryInExePath technique for
the Popen call in git.index.fun.run_commit_hook on Windows as is
already used in git.cmd.Git.execute.

The code is simpler in run_commit_hook because a shell is never
used to run bash.exe. (bash.exe is itself a shell, but we never
run it *via* a shell by passing shell=True to Popen.) Nonetheless,
it may make sense to extract out a helper function both can call.
This commit does not do that, so there is some code duplication.
- Create and use a test.lib.helper.VirtualEnvironment class.
- Import and use venv module instead of running "python -m venv".

These changes make no significant difference in speed or clarity
for the existing test in test_installation. The reason for this
change is instead to support the use of new per-test virtual
environments in at least one other test.
See comments for details on the test's new implementation and what
it achieves.
The main case where this happens is when tempfile.gettempdir() has
a component in it that uses an 8.3-encoded path, e.g.,
C:\Users\Administrator\... -> C:\Users\ADMINI~1\...

This is a workaround for python/cpython#90329. I call realpath only
once, when the venv is created, and not on any paths inside the
venv, to make it less likely this masks the problems the warning is
meant for. (For example, if Scripts, or python.exe in it, produced
this even with the venv created as it is now, then that may indicte
an actual problem.)

Note that copying python.exe from Scripts to one level up in the
venv, and changing its name to bash.exe to use it to simulate the
bash.exe impostor, as is done in test_hook_uses_shell_not_from_cwd,
should not (and does not) produce this warning. If that ever starts
to do so, then that should be examined as a sign of brittleness.
This creates git.util.safer_popen that, on non-Windows systems, is
bound to subprocess.Popen (to avoid introducing unnecessary
latency). On Windows, it is a function that wraps subprocess.Popen,
consolidating two pieces of logic that had previously been
duplicated:

1. Temporarily setting NoDefaultCurrentDirectoryInExePath in the
   calling environment and, when shell=True is used, setting it in
   the subprocess environment as well. This prevents executables
   specified as single names (which are mainly "git" and, for
   hooks, "bash.exe") from being searched for in the current
   working directory of GitPython or, when a shell is used, the
   current working directory of the shell used to run them.

2. Passing the CREATE_NO_WINDOW and CREATE_NEW_PROCESS_GROUP flags
   as creationflags. This is not a security measure. It is
   indirectly related to safety in that CREATE_NO_WINDOW eliminated
   at least some, and possibly all, cases where calling Git.execute
   (directly, or indirectly via a dynamic method) with shell=True
   conferred an advantage over the inherently more secure default
   of shell=False; and CREATE_NEW_PROCESS facilitates some ways of
   terminating subprocesses that would otherwise be unavailable,
   thereby making resource exhaustion less likely. But really the
   reason I included creationflags here is that it seems it should
   always be used in the same situations as preventing the current
   directory from being searched (and always was), and including it
   further reduces code duplication and simplifies calling code.

This commit does not improve security or robustness, because these
features were already present. Instead, this moves them to a single
location. It also documents them by giving the function bound to
safer_popen on Windows, _safer_popen_windows, a detailed docstring.

Because there would otherwise be potential for confusion on the
different ways to perform or customize path searches, I have also
added a doctring to py_where noting its limited use case and its
relationship to shutil.which and non-shell search.

(The search in _safer_popen_windows is typically a non-shell
search, which is why it cannot be reimplemented to do its own
lookup by calling an only slightly modified version of
shutil.which, without a risk of breaking some currently working
uses. It may, however, be possible to fix the race condition by
doing something analogous for Windows non-shell search behavior,
which is largely but not entirely described in the documentation
for CreateProcessW.)
I had originally written it in git.util because it is used from two
separate modules (git.cmd and git.index.fun) and is arguably the
same sort of thing as remove_password_if_present, in that both
relate to running processes (and to security) and both are used
from multiple modules yet are not meant for use outside GitPython.

However, all of this is also true of git.cmd.handle_process_output,
which this really has more in common with: it's a utility related
*only* to the use of subprocesses, while remove_password_if_present
can be used for other sanitization. In addition, it also replaces
git.cmd.PROC_CREATIONFLAGS (also imported in git.index.fun) by
passing that to Popen on Windows (since the situations where a
custom value of creationflags should be used are the same as those
where safer_popen should be called for its primary benefit of
avoiding an untrusted path search when creating the subprocess).

safer_popen and its Windows implementation _safer_popen_windows are
thus moved from git/util.py to git/cmd.py, with related changes,
such as to imports, done everywhere they are needed.
@EliahKagan EliahKagan marked this pull request as ready for review January 10, 2024 09:59
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Thanks so much for figuring this out (!!) and for providing not only the fix, but also the tests that exemplify the issue while assuring they are now fixed.

I will create a new release shortly.

@Byron Byron merged commit ef3192c into gitpython-developers:main Jan 10, 2024
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lettuce-bot bot referenced this pull request in lettuce-financial/github-bot-signed-commit Jan 10, 2024
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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [GitPython](https://togithub.com/gitpython-developers/GitPython) |
`==3.1.40` -> `==3.1.41` |
[![age](https://developer.mend.io/api/mc/badges/age/pypi/GitPython/3.1.41?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/pypi/GitPython/3.1.41?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/pypi/GitPython/3.1.40/3.1.41?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/GitPython/3.1.40/3.1.41?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

---

### Release Notes

<details>
<summary>gitpython-developers/GitPython (GitPython)</summary>

###
[`v3.1.41`](https://togithub.com/gitpython-developers/GitPython/releases/tag/3.1.41):
- fix Windows security issue

[Compare
Source](https://togithub.com/gitpython-developers/GitPython/compare/3.1.40...3.1.41)

The details about the Windows security issue [can be found in this
advisory](https://togithub.com/gitpython-developers/GitPython/security/advisories/GHSA-2mqj-m65w-jghx).

Special thanks go to
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) who reported the
issue and fixed it in a single stroke, while being responsible for an
incredible amount of improvements that he contributed over the last
couple of months ❤️.

#### What's Changed

- Add `__all__` in git.exc by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1719](https://togithub.com/gitpython-developers/GitPython/pull/1719)
- Set submodule update cadence to weekly by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1721](https://togithub.com/gitpython-developers/GitPython/pull/1721)
- Never modify sys.path by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1720](https://togithub.com/gitpython-developers/GitPython/pull/1720)
- Bump git/ext/gitdb from `8ec2390` to `ec58b7e` by
[@&#8203;dependabot](https://togithub.com/dependabot) in
[https://github.com/gitpython-developers/GitPython/pull/1722](https://togithub.com/gitpython-developers/GitPython/pull/1722)
- Revise comments, docstrings, some messages, and a bit of code by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1725](https://togithub.com/gitpython-developers/GitPython/pull/1725)
- Use zero-argument super() by
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- Remove obsolete note in \_iter_packed_refs by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1727](https://togithub.com/gitpython-developers/GitPython/pull/1727)
- Reorganize test_util and make xfail marks precise by
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[https://github.com/gitpython-developers/GitPython/pull/1729](https://togithub.com/gitpython-developers/GitPython/pull/1729)
- Clarify license and make module top comments more consistent by
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[https://github.com/gitpython-developers/GitPython/pull/1730](https://togithub.com/gitpython-developers/GitPython/pull/1730)
- Deprecate compat.is\_<platform>, rewriting all uses by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1732](https://togithub.com/gitpython-developers/GitPython/pull/1732)
- Revise and restore some module docstrings by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1735](https://togithub.com/gitpython-developers/GitPython/pull/1735)
- Make the rmtree callback Windows-only by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1739](https://togithub.com/gitpython-developers/GitPython/pull/1739)
- List all non-passing tests in test summaries by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1740](https://togithub.com/gitpython-developers/GitPython/pull/1740)
- Document some minor subtleties in test_util.py by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1749](https://togithub.com/gitpython-developers/GitPython/pull/1749)
- Always read metadata files as UTF-8 in setup.py by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1748](https://togithub.com/gitpython-developers/GitPython/pull/1748)
- Test native Windows on CI by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1745](https://togithub.com/gitpython-developers/GitPython/pull/1745)
- Test macOS on CI by
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- Let close_fds be True on all platforms by
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- Fix IndexFile.from_tree on Windows by
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- Remove unused TASKKILL fallback in AutoInterrupt by
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- Don't return with operand when conceptually void by
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- Group .gitignore entries by purpose by
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- Adding dubious ownership handling by
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- Avoid brittle assumptions about preexisting temporary files in tests
by [@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1759](https://togithub.com/gitpython-developers/GitPython/pull/1759)
- Overhaul noqa directives by
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- Clarify some Git.execute kill_after_timeout limitations by
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- Bump actions/setup-python from 4 to 5 by
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[https://github.com/gitpython-developers/GitPython/pull/1763](https://togithub.com/gitpython-developers/GitPython/pull/1763)
- Don't install black on Cygwin by
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- Extract all "import gc" to module level by
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- Extract remaining local "import gc" to module level by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1768](https://togithub.com/gitpython-developers/GitPython/pull/1768)
- Replace xfail with gc.collect in TestSubmodule.test_rename by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1767](https://togithub.com/gitpython-developers/GitPython/pull/1767)
- Enable CodeQL by [@&#8203;EliahKagan](https://togithub.com/EliahKagan)
in
[https://github.com/gitpython-developers/GitPython/pull/1769](https://togithub.com/gitpython-developers/GitPython/pull/1769)
- Replace some uses of the deprecated mktemp function by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1770](https://togithub.com/gitpython-developers/GitPython/pull/1770)
- Bump github/codeql-action from 2 to 3 by
[@&#8203;dependabot](https://togithub.com/dependabot) in
[https://github.com/gitpython-developers/GitPython/pull/1773](https://togithub.com/gitpython-developers/GitPython/pull/1773)
- Run some Windows environment variable tests only on Windows by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1774](https://togithub.com/gitpython-developers/GitPython/pull/1774)
- Fix TemporaryFileSwap regression where file_path could not be Path by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1776](https://togithub.com/gitpython-developers/GitPython/pull/1776)
- Improve hooks tests by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1777](https://togithub.com/gitpython-developers/GitPython/pull/1777)
- Fix if items of Index is of type PathLike by
[@&#8203;stegm](https://togithub.com/stegm) in
[https://github.com/gitpython-developers/GitPython/pull/1778](https://togithub.com/gitpython-developers/GitPython/pull/1778)
- Better document IterableObj.iter_items and improve some subclasses by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1780](https://togithub.com/gitpython-developers/GitPython/pull/1780)
- Revert "Don't install black on Cygwin" by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1783](https://togithub.com/gitpython-developers/GitPython/pull/1783)
- Add missing pip in $PATH on Cygwin CI by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1784](https://togithub.com/gitpython-developers/GitPython/pull/1784)
- Shorten Iterable docstrings and put IterableObj first by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1785](https://togithub.com/gitpython-developers/GitPython/pull/1785)
- Fix incompletely revised Iterable/IterableObj docstrings by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1786](https://togithub.com/gitpython-developers/GitPython/pull/1786)
- Pre-deprecate setting Git.USE_SHELL by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1782](https://togithub.com/gitpython-developers/GitPython/pull/1782)
- Deprecate Git.USE_SHELL by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1787](https://togithub.com/gitpython-developers/GitPython/pull/1787)
- In handle_process_output don't forward finalizer result by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1788](https://togithub.com/gitpython-developers/GitPython/pull/1788)
- Fix mypy warning "Missing return statement" by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1789](https://togithub.com/gitpython-developers/GitPython/pull/1789)
- Fix two remaining Windows untrusted search path cases by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1792](https://togithub.com/gitpython-developers/GitPython/pull/1792)

#### New Contributors

- [@&#8203;marioaag](https://togithub.com/marioaag) made their first
contribution in
[https://github.com/gitpython-developers/GitPython/pull/1746](https://togithub.com/gitpython-developers/GitPython/pull/1746)
- [@&#8203;stegm](https://togithub.com/stegm) made their first
contribution in
[https://github.com/gitpython-developers/GitPython/pull/1778](https://togithub.com/gitpython-developers/GitPython/pull/1778)

**Full Changelog**:
gitpython-developers/GitPython@3.1.40...3.1.41

</details>

---

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [GitPython](https://togithub.com/gitpython-developers/GitPython) |
`==3.1.40` -> `==3.1.41` |
[![age](https://developer.mend.io/api/mc/badges/age/pypi/GitPython/3.1.41?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
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|
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|

---

### Release Notes

<details>
<summary>gitpython-developers/GitPython (GitPython)</summary>

###
[`v3.1.41`](https://togithub.com/gitpython-developers/GitPython/releases/tag/3.1.41):
- fix Windows security issue

[Compare
Source](https://togithub.com/gitpython-developers/GitPython/compare/3.1.40...3.1.41)

The details about the Windows security issue [can be found in this
advisory](https://togithub.com/gitpython-developers/GitPython/security/advisories/GHSA-2mqj-m65w-jghx).

Special thanks go to
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) who reported the
issue and fixed it in a single stroke, while being responsible for an
incredible amount of improvements that he contributed over the last
couple of months ❤️.

#### What's Changed

- Add `__all__` in git.exc by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1719](https://togithub.com/gitpython-developers/GitPython/pull/1719)
- Set submodule update cadence to weekly by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1721](https://togithub.com/gitpython-developers/GitPython/pull/1721)
- Never modify sys.path by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1720](https://togithub.com/gitpython-developers/GitPython/pull/1720)
- Bump git/ext/gitdb from `8ec2390` to `ec58b7e` by
[@&#8203;dependabot](https://togithub.com/dependabot) in
[https://github.com/gitpython-developers/GitPython/pull/1722](https://togithub.com/gitpython-developers/GitPython/pull/1722)
- Revise comments, docstrings, some messages, and a bit of code by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1725](https://togithub.com/gitpython-developers/GitPython/pull/1725)
- Use zero-argument super() by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1726](https://togithub.com/gitpython-developers/GitPython/pull/1726)
- Remove obsolete note in \_iter_packed_refs by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1727](https://togithub.com/gitpython-developers/GitPython/pull/1727)
- Reorganize test_util and make xfail marks precise by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1729](https://togithub.com/gitpython-developers/GitPython/pull/1729)
- Clarify license and make module top comments more consistent by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1730](https://togithub.com/gitpython-developers/GitPython/pull/1730)
- Deprecate compat.is\_<platform>, rewriting all uses by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1732](https://togithub.com/gitpython-developers/GitPython/pull/1732)
- Revise and restore some module docstrings by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1735](https://togithub.com/gitpython-developers/GitPython/pull/1735)
- Make the rmtree callback Windows-only by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1739](https://togithub.com/gitpython-developers/GitPython/pull/1739)
- List all non-passing tests in test summaries by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1740](https://togithub.com/gitpython-developers/GitPython/pull/1740)
- Document some minor subtleties in test_util.py by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1749](https://togithub.com/gitpython-developers/GitPython/pull/1749)
- Always read metadata files as UTF-8 in setup.py by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1748](https://togithub.com/gitpython-developers/GitPython/pull/1748)
- Test native Windows on CI by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1745](https://togithub.com/gitpython-developers/GitPython/pull/1745)
- Test macOS on CI by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1752](https://togithub.com/gitpython-developers/GitPython/pull/1752)
- Let close_fds be True on all platforms by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1753](https://togithub.com/gitpython-developers/GitPython/pull/1753)
- Fix IndexFile.from_tree on Windows by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1751](https://togithub.com/gitpython-developers/GitPython/pull/1751)
- Remove unused TASKKILL fallback in AutoInterrupt by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1754](https://togithub.com/gitpython-developers/GitPython/pull/1754)
- Don't return with operand when conceptually void by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1755](https://togithub.com/gitpython-developers/GitPython/pull/1755)
- Group .gitignore entries by purpose by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1758](https://togithub.com/gitpython-developers/GitPython/pull/1758)
- Adding dubious ownership handling by
[@&#8203;marioaag](https://togithub.com/marioaag) in
[https://github.com/gitpython-developers/GitPython/pull/1746](https://togithub.com/gitpython-developers/GitPython/pull/1746)
- Avoid brittle assumptions about preexisting temporary files in tests
by [@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1759](https://togithub.com/gitpython-developers/GitPython/pull/1759)
- Overhaul noqa directives by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1760](https://togithub.com/gitpython-developers/GitPython/pull/1760)
- Clarify some Git.execute kill_after_timeout limitations by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1761](https://togithub.com/gitpython-developers/GitPython/pull/1761)
- Bump actions/setup-python from 4 to 5 by
[@&#8203;dependabot](https://togithub.com/dependabot) in
[https://github.com/gitpython-developers/GitPython/pull/1763](https://togithub.com/gitpython-developers/GitPython/pull/1763)
- Don't install black on Cygwin by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1766](https://togithub.com/gitpython-developers/GitPython/pull/1766)
- Extract all "import gc" to module level by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1765](https://togithub.com/gitpython-developers/GitPython/pull/1765)
- Extract remaining local "import gc" to module level by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1768](https://togithub.com/gitpython-developers/GitPython/pull/1768)
- Replace xfail with gc.collect in TestSubmodule.test_rename by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1767](https://togithub.com/gitpython-developers/GitPython/pull/1767)
- Enable CodeQL by [@&#8203;EliahKagan](https://togithub.com/EliahKagan)
in
[https://github.com/gitpython-developers/GitPython/pull/1769](https://togithub.com/gitpython-developers/GitPython/pull/1769)
- Replace some uses of the deprecated mktemp function by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1770](https://togithub.com/gitpython-developers/GitPython/pull/1770)
- Bump github/codeql-action from 2 to 3 by
[@&#8203;dependabot](https://togithub.com/dependabot) in
[https://github.com/gitpython-developers/GitPython/pull/1773](https://togithub.com/gitpython-developers/GitPython/pull/1773)
- Run some Windows environment variable tests only on Windows by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1774](https://togithub.com/gitpython-developers/GitPython/pull/1774)
- Fix TemporaryFileSwap regression where file_path could not be Path by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1776](https://togithub.com/gitpython-developers/GitPython/pull/1776)
- Improve hooks tests by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1777](https://togithub.com/gitpython-developers/GitPython/pull/1777)
- Fix if items of Index is of type PathLike by
[@&#8203;stegm](https://togithub.com/stegm) in
[https://github.com/gitpython-developers/GitPython/pull/1778](https://togithub.com/gitpython-developers/GitPython/pull/1778)
- Better document IterableObj.iter_items and improve some subclasses by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1780](https://togithub.com/gitpython-developers/GitPython/pull/1780)
- Revert "Don't install black on Cygwin" by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1783](https://togithub.com/gitpython-developers/GitPython/pull/1783)
- Add missing pip in $PATH on Cygwin CI by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1784](https://togithub.com/gitpython-developers/GitPython/pull/1784)
- Shorten Iterable docstrings and put IterableObj first by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1785](https://togithub.com/gitpython-developers/GitPython/pull/1785)
- Fix incompletely revised Iterable/IterableObj docstrings by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1786](https://togithub.com/gitpython-developers/GitPython/pull/1786)
- Pre-deprecate setting Git.USE_SHELL by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1782](https://togithub.com/gitpython-developers/GitPython/pull/1782)
- Deprecate Git.USE_SHELL by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1787](https://togithub.com/gitpython-developers/GitPython/pull/1787)
- In handle_process_output don't forward finalizer result by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1788](https://togithub.com/gitpython-developers/GitPython/pull/1788)
- Fix mypy warning "Missing return statement" by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1789](https://togithub.com/gitpython-developers/GitPython/pull/1789)
- Fix two remaining Windows untrusted search path cases by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1792](https://togithub.com/gitpython-developers/GitPython/pull/1792)

#### New Contributors

- [@&#8203;marioaag](https://togithub.com/marioaag) made their first
contribution in
[https://github.com/gitpython-developers/GitPython/pull/1746](https://togithub.com/gitpython-developers/GitPython/pull/1746)
- [@&#8203;stegm](https://togithub.com/stegm) made their first
contribution in
[https://github.com/gitpython-developers/GitPython/pull/1778](https://togithub.com/gitpython-developers/GitPython/pull/1778)

**Full Changelog**:
gitpython-developers/GitPython@3.1.40...3.1.41

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined),
Automerge - At any time (no schedule defined).

🚦 **Automerge**: Enabled.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update
again.

---

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---

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@EliahKagan
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EliahKagan commented Jan 16, 2024

I hope it's okay that I've made a small edit to the advisory to fix some confusing and slightly inaccurate wording that I had missed when first writing it. I'd be pleased to make any further changes if desired (or even undo this change if for some reason it is not considered beneficial).

I've applied the change already at the advisory on this repository. For the global advisory, I cannot apply the change directly; I've submitted github/advisory-database#3290.

I've noticed that these changes may be hard to spot quickly in the public web-based interface, so I've also made a gist whose revision history shows the proposed changes.

@Byron
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Byron commented Jan 17, 2024

Thanks a lot, and since the first time I wasn't able to suggest improvements, now that it is further improved, I am even more out of my ability to do so. I am sure, however, that the one reviewing the advisory PR will come to the same conclusion and merge the improvements.

Thanks again for your relentless pursuit of excellence!

@EliahKagan
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The global advisory has been successfully updated.

EliahKagan added a commit to EliahKagan/GitPython that referenced this pull request Mar 7, 2024
On Windows, Python's subprocess module contains constants useful to
pass to the `creationflags` parameter of subprocess.Popen. These
are absent on other platforms, where they are not meaningful.

The code was already safe at runtime from any AttributeError
related to these constants, because they were only used in
git.cmd._safer_popen_windows, which was defined on Windows.

But in gitpython-developers#1792 I did not write the code in a way where mypy can
verify its correctness. So if a regression of the kind mypy can in
principle catch were to occur, it would be harder to notice it.

This refactors the code, keeping the same behavior but expressing
it in a way mypy can understand. This consists of two changes:

1. Only define _safer_popen_windows when the platform is Windows,
   placing it in the first branch of the `if` statement.

   This is needed because mypy will not take the only current call
   to that nonpublic function being on Windows as sufficient
   evidence that the platform is always Windows when it is run.

2. Determine the platform, for this purpose, using sys.platform
   instead of os.name.

   These are far from equivalent in general (see the deprecation
   rationale for is_<platform> in gitpython-developers#1732, revised in a0fa2bd
   in gitpython-developers#1787). However, in Python 3 (GitPython no longer supports
   Python 2), in the specific case of Windows, we have a choice of
   which to use, as both `sys.platform == "win32"` and
   `os.name == "nt"`.

   os.name is "nt" on native Windows, and "posix" on Cygwin.
   sys.platform is "win32" on native Windows (including 64-bit
   systems with 64-bit Python builds), and "cygwin" on Cygwin. See:
   https://docs.python.org/3/library/sys.html#sys.platform

   This is needed because the type stubs for the subprocess module
   use this sys.platform check (rather than an os.name check) to
   determine if the platform is Windows for the purpose of deciding
   which constants to say the subprocess module defines.

I have verified that neither of these changes is enough by itself.
EliahKagan added a commit to EliahKagan/GitPython that referenced this pull request Mar 29, 2024
In the USE_SHELL docstring:

- Restore the older wording "when executing git commands" rather
  than "to execute git commands". I've realized that longer phrase,
  which dates back to the introduction of USE_SHELL in 1c2dd54, is
  clearer, because readers less familiar with GitPython's overall
  design and operation will still not be misled into thinking
  USE_SHELL ever affects whether GitPython uses an external git
  command, versus some other mechanism, to do something.

- Give some more information about why USE_SHELL = True is unsafe
  (though further revision or clarification may be called for).

- Note some non-obvious aspects of USE_SHELL, that some of the way
  it interacts with other aspects of GitPython is not part of what
  is or has been documented about it, and in practice changes over
  time. The first example relates to gitpython-developers#1792; the second may help
  users understand why code that enables USE_SHELL on Windows, in
  addition to being unsafe there, often breaks immediately on other
  platforms; the third is included so the warnings in the expanded
  docstring are not interpreted as a new commitment that any shell
  syntax that may have a *desired* effect in some application will
  continue to have the same effect in the future.

- Cover a second application that might lead, or have led, to
  setting USE_SHELL to True, and explain what to do instead.

In test_successful_default_refresh_invalidates_cached_version_info:

- Rewrite the commented explanation of a special variant of that
  second application, where the usual easy alternatives are not
  used because part of the goal of the test is to check a "default"
  scenario that does not include either of them. This better
  explains why that choice is made in the test, and also hopefully
  will prevent anyone from thinking that test is a model for
  another situation (which, as noted, is unlikely to be the case
  even in unit tests).
JoeWang1127 referenced this pull request in googleapis/sdk-platform-java Apr 6, 2024
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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [GitPython](https://togithub.com/gitpython-developers/GitPython) |
`==3.1.40` -> `==3.1.41` |
[![age](https://developer.mend.io/api/mc/badges/age/pypi/GitPython/3.1.41?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/pypi/GitPython/3.1.41?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/pypi/GitPython/3.1.40/3.1.41?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/pypi/GitPython/3.1.40/3.1.41?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

---

> [!WARNING]
> Some dependencies could not be looked up. Check the Dependency
Dashboard for more information.

### GitHub Vulnerability Alerts

####
[CVE-2024-22190](https://togithub.com/gitpython-developers/GitPython/security/advisories/GHSA-2mqj-m65w-jghx)

### Summary

This issue exists because of an incomplete fix for CVE-2023-40590. On
Windows, GitPython uses an untrusted search path if it uses a shell to
run `git`, as well as when it runs `bash.exe` to interpret hooks. If
either of those features are used on Windows, a malicious `git.exe` or
`bash.exe` may be run from an untrusted repository.

### Details

Although GitPython often avoids executing programs found in an untrusted
search path since 3.1.33, two situations remain where this still occurs.
Either can allow arbitrary code execution under some circumstances.

#### When a shell is used

GitPython can be told to run `git` commands through a shell rather than
as direct subprocesses, by passing `shell=True` to any method that
accepts it, or by both setting `Git.USE_SHELL = True` and not passing
`shell=False`. Then the Windows `cmd.exe` shell process performs the
path search, and GitPython does not prevent that shell from finding and
running `git` in the current directory.

When GitPython runs `git` directly rather than through a shell, the
GitPython process performs the path search, and currently omits the
current directory by setting `NoDefaultCurrentDirectoryInExePath` in its
own environment during the `Popen` call. Although the `cmd.exe` shell
will honor this environment variable when present, GitPython does not
currently pass it into the shell subprocess's environment.

Furthermore, because GitPython sets the subprocess CWD to the root of a
repository's working tree, using a shell will run a malicious `git.exe`
in an untrusted repository even if GitPython itself is run from a
trusted location.

This also applies if `Git.execute` is called directly with `shell=True`
(or after `Git.USE_SHELL = True`) to run any command.

#### When hook scripts are run

On Windows, GitPython uses `bash.exe` to run hooks that appear to be
scripts. However, unlike when running `git`, no steps are taken to avoid
finding and running `bash.exe` in the current directory.

This allows the author of an untrusted fork or branch to cause a
malicious `bash.exe` to be run in some otherwise safe workflows. An
example of such a scenario is if the user installs a trusted hook while
on a trusted branch, then switches to an untrusted feature branch
(possibly from a fork) to review proposed changes. If the untrusted
feature branch contains a malicious `bash.exe` and the user's current
working directory is the working tree, and the user performs an action
that runs the hook, then although the hook itself is uncorrupted, it
runs with the malicious `bash.exe`.

Note that, while `bash.exe` is a shell, this is a separate scenario from
when `git` is run using the unrelated Windows `cmd.exe` shell.

### PoC

On Windows, create a `git.exe` file in a repository. Then create a
`Repo` object, and call any method through it (directly or indirectly)
that supports the `shell` keyword argument with `shell=True`:

```powershell
mkdir testrepo
git init testrepo
cp ... testrepo git.exe # Replace "..." with any executable of choice.
python -c "import git; print(git.Repo('testrepo').git.version(shell=True))"
```

The `git.exe` executable in the repository directory will be run.

Or use no `Repo` object, but do it from the location with the `git.exe`:

```powershell
cd testrepo
python -c "import git; print(git.Git().version(shell=True))"
```

The `git.exe` executable in the current directory will be run.

For the scenario with hooks, install a hook in a repository, create a
`bash.exe` file in the current directory, and perform an operation that
causes GitPython to attempt to run the hook:

```powershell
mkdir testrepo
cd testrepo
git init
mv .git/hooks/pre-commit.sample .git/hooks/pre-commit
cp ... bash.exe # Replace "..." with any executable of choice.
echo "Some text" >file.txt
git add file.txt
python -c "import git; git.Repo().index.commit('Some message')"
```

The `bash.exe` executable in the current directory will be run.

### Impact

The greatest impact is probably in applications that set `Git.USE_SHELL
= True` for historical reasons. (Undesired console windows had, in the
past, been created in some kinds of applications, when it was not used.)
Such an application may be vulnerable to arbitrary code execution from a
malicious repository, even with no other exacerbating conditions. This
is to say that, if a shell is used to run `git`, the full effect of
CVE-2023-40590 is still present. Furthermore, as noted above, running
the application itself from a trusted directory is not a sufficient
mitigation.

An application that does not direct GitPython to use a shell to run
`git` subprocesses thus avoids most of the risk. However, there is no
such straightforward way to prevent GitPython from running `bash.exe` to
interpret hooks. So while the conditions needed for that to be exploited
are more involved, it may be harder to mitigate decisively prior to
patching.

### Possible solutions

A straightforward approach would be to address each bug directly:

- When a shell is used, pass `NoDefaultCurrentDirectoryInExePath` into
the subprocess environment, because in that scenario the subprocess is
the `cmd.exe` shell that itself performs the path search.
- Set `NoDefaultCurrentDirectoryInExePath` in the GitPython process
environment during the `Popen` call made to run hooks with a `bash.exe`
subprocess.

These need only be done on Windows.

---

### Release Notes

<details>
<summary>gitpython-developers/GitPython (GitPython)</summary>

###
[`v3.1.41`](https://togithub.com/gitpython-developers/GitPython/releases/tag/3.1.41):
- fix Windows security issue

[Compare
Source](https://togithub.com/gitpython-developers/GitPython/compare/3.1.40...3.1.41)

The details about the Windows security issue [can be found in this
advisory](https://togithub.com/gitpython-developers/GitPython/security/advisories/GHSA-2mqj-m65w-jghx).

Special thanks go to
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) who reported the
issue and fixed it in a single stroke, while being responsible for an
incredible amount of improvements that he contributed over the last
couple of months ❤️.

#### What's Changed

- Add `__all__` in git.exc by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1719](https://togithub.com/gitpython-developers/GitPython/pull/1719)
- Set submodule update cadence to weekly by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1721](https://togithub.com/gitpython-developers/GitPython/pull/1721)
- Never modify sys.path by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1720](https://togithub.com/gitpython-developers/GitPython/pull/1720)
- Bump git/ext/gitdb from `8ec2390` to `ec58b7e` by
[@&#8203;dependabot](https://togithub.com/dependabot) in
[https://github.com/gitpython-developers/GitPython/pull/1722](https://togithub.com/gitpython-developers/GitPython/pull/1722)
- Revise comments, docstrings, some messages, and a bit of code by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1725](https://togithub.com/gitpython-developers/GitPython/pull/1725)
- Use zero-argument super() by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1726](https://togithub.com/gitpython-developers/GitPython/pull/1726)
- Remove obsolete note in \_iter_packed_refs by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1727](https://togithub.com/gitpython-developers/GitPython/pull/1727)
- Reorganize test_util and make xfail marks precise by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1729](https://togithub.com/gitpython-developers/GitPython/pull/1729)
- Clarify license and make module top comments more consistent by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1730](https://togithub.com/gitpython-developers/GitPython/pull/1730)
- Deprecate compat.is\_<platform>, rewriting all uses by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1732](https://togithub.com/gitpython-developers/GitPython/pull/1732)
- Revise and restore some module docstrings by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1735](https://togithub.com/gitpython-developers/GitPython/pull/1735)
- Make the rmtree callback Windows-only by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1739](https://togithub.com/gitpython-developers/GitPython/pull/1739)
- List all non-passing tests in test summaries by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1740](https://togithub.com/gitpython-developers/GitPython/pull/1740)
- Document some minor subtleties in test_util.py by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1749](https://togithub.com/gitpython-developers/GitPython/pull/1749)
- Always read metadata files as UTF-8 in setup.py by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1748](https://togithub.com/gitpython-developers/GitPython/pull/1748)
- Test native Windows on CI by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1745](https://togithub.com/gitpython-developers/GitPython/pull/1745)
- Test macOS on CI by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1752](https://togithub.com/gitpython-developers/GitPython/pull/1752)
- Let close_fds be True on all platforms by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1753](https://togithub.com/gitpython-developers/GitPython/pull/1753)
- Fix IndexFile.from_tree on Windows by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1751](https://togithub.com/gitpython-developers/GitPython/pull/1751)
- Remove unused TASKKILL fallback in AutoInterrupt by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1754](https://togithub.com/gitpython-developers/GitPython/pull/1754)
- Don't return with operand when conceptually void by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1755](https://togithub.com/gitpython-developers/GitPython/pull/1755)
- Group .gitignore entries by purpose by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1758](https://togithub.com/gitpython-developers/GitPython/pull/1758)
- Adding dubious ownership handling by
[@&#8203;marioaag](https://togithub.com/marioaag) in
[https://github.com/gitpython-developers/GitPython/pull/1746](https://togithub.com/gitpython-developers/GitPython/pull/1746)
- Avoid brittle assumptions about preexisting temporary files in tests
by [@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1759](https://togithub.com/gitpython-developers/GitPython/pull/1759)
- Overhaul noqa directives by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1760](https://togithub.com/gitpython-developers/GitPython/pull/1760)
- Clarify some Git.execute kill_after_timeout limitations by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1761](https://togithub.com/gitpython-developers/GitPython/pull/1761)
- Bump actions/setup-python from 4 to 5 by
[@&#8203;dependabot](https://togithub.com/dependabot) in
[https://github.com/gitpython-developers/GitPython/pull/1763](https://togithub.com/gitpython-developers/GitPython/pull/1763)
- Don't install black on Cygwin by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1766](https://togithub.com/gitpython-developers/GitPython/pull/1766)
- Extract all "import gc" to module level by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1765](https://togithub.com/gitpython-developers/GitPython/pull/1765)
- Extract remaining local "import gc" to module level by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1768](https://togithub.com/gitpython-developers/GitPython/pull/1768)
- Replace xfail with gc.collect in TestSubmodule.test_rename by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1767](https://togithub.com/gitpython-developers/GitPython/pull/1767)
- Enable CodeQL by [@&#8203;EliahKagan](https://togithub.com/EliahKagan)
in
[https://github.com/gitpython-developers/GitPython/pull/1769](https://togithub.com/gitpython-developers/GitPython/pull/1769)
- Replace some uses of the deprecated mktemp function by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1770](https://togithub.com/gitpython-developers/GitPython/pull/1770)
- Bump github/codeql-action from 2 to 3 by
[@&#8203;dependabot](https://togithub.com/dependabot) in
[https://github.com/gitpython-developers/GitPython/pull/1773](https://togithub.com/gitpython-developers/GitPython/pull/1773)
- Run some Windows environment variable tests only on Windows by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1774](https://togithub.com/gitpython-developers/GitPython/pull/1774)
- Fix TemporaryFileSwap regression where file_path could not be Path by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1776](https://togithub.com/gitpython-developers/GitPython/pull/1776)
- Improve hooks tests by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1777](https://togithub.com/gitpython-developers/GitPython/pull/1777)
- Fix if items of Index is of type PathLike by
[@&#8203;stegm](https://togithub.com/stegm) in
[https://github.com/gitpython-developers/GitPython/pull/1778](https://togithub.com/gitpython-developers/GitPython/pull/1778)
- Better document IterableObj.iter_items and improve some subclasses by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1780](https://togithub.com/gitpython-developers/GitPython/pull/1780)
- Revert "Don't install black on Cygwin" by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1783](https://togithub.com/gitpython-developers/GitPython/pull/1783)
- Add missing pip in $PATH on Cygwin CI by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1784](https://togithub.com/gitpython-developers/GitPython/pull/1784)
- Shorten Iterable docstrings and put IterableObj first by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1785](https://togithub.com/gitpython-developers/GitPython/pull/1785)
- Fix incompletely revised Iterable/IterableObj docstrings by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1786](https://togithub.com/gitpython-developers/GitPython/pull/1786)
- Pre-deprecate setting Git.USE_SHELL by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1782](https://togithub.com/gitpython-developers/GitPython/pull/1782)
- Deprecate Git.USE_SHELL by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1787](https://togithub.com/gitpython-developers/GitPython/pull/1787)
- In handle_process_output don't forward finalizer result by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1788](https://togithub.com/gitpython-developers/GitPython/pull/1788)
- Fix mypy warning "Missing return statement" by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1789](https://togithub.com/gitpython-developers/GitPython/pull/1789)
- Fix two remaining Windows untrusted search path cases by
[@&#8203;EliahKagan](https://togithub.com/EliahKagan) in
[https://github.com/gitpython-developers/GitPython/pull/1792](https://togithub.com/gitpython-developers/GitPython/pull/1792)

#### New Contributors

- [@&#8203;marioaag](https://togithub.com/marioaag) made their first
contribution in
[https://github.com/gitpython-developers/GitPython/pull/1746](https://togithub.com/gitpython-developers/GitPython/pull/1746)
- [@&#8203;stegm](https://togithub.com/stegm) made their first
contribution in
[https://github.com/gitpython-developers/GitPython/pull/1778](https://togithub.com/gitpython-developers/GitPython/pull/1778)

**Full Changelog**:
gitpython-developers/GitPython@3.1.40...3.1.41

</details>

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