Clarify license and make module top comments more consistent by EliahKagan · Pull Request #1730 · gitpython-developers/GitPython

added 3 commits

November 3, 2023 14:35
This improves the consistency of top-of-module comments as follows:

- All names of the current file are removed. Some included these
  while others didn't. In general, this can be useful information,
  which can remind readers and developers of what the file is and
  may even reduce mistakes. However, in GitPython, many modules
  inside git/ have the same name as other modules in other
  subdirectories of git/. So the presence of filenames would
  often be the same for multiple files, a condition that would be
  intensified if consistency were achieved by adding them
  everywhere. This instead removes them, which should (albeit
  slightly) decrease the risk of confusing modules that have the
  same name as each other.

- All modules (.py files) inside git/ and test/, except for .py
  files that are entirely empty (without even comments) or are
  inside test/fixtures/, now have comments indicating the license
  and linking to it on opensource.org. Previously, some modules
  had this, while others did not.

The comment about the license is short, and does not contain an
explicit copyright statement. No new explicit copyright statements
are added, but some top-of-modules already contained them, and this
does not remove (nor update or otherwise modify) them.

Although explicit copyright statements are not touched, all the
license comments are modified, including where they had previously
appeared, to say "the 3-Clause BSD License" instead of
"the BSD License", since there is no specific license known as the
"BSD License" (and both the 2-clause and 3-clause BSD licenses are
very popular).

This change should not be confused with gitpython-developers#1662, which fixed an
originally correct hyperlink that had come to redirect to a page
about a different license. The change here does not change the link
again. It makes the commented wording more specific, so that it is
clear, even without looking at the link, which BSD license is being
referred to.
The license in README.md was named as "New BSD License", which is
in practice unambiguous, but no longer as readily recognized as is
"3-Clause BSD License". This updates the wording to call it by the
latter name, for that reason and for consistency with the previous
commit's changes to top-of-module comments, while also noting
parenthetically that it is also called the New BSD License.

The main reason for retaining "New BSD License" parenthetically is
to prevent anyone from being confused into thinking this change is
in any way associated with a change to the license, or that any
license change has occurred or is forthcoming. (This does *not*
change how GitPython is actually licensed in any way.)
This uses "BSD-3-Clause" instead of "BSD" as the "license" metadata
in setup.py. "BSD-3-Clause" is the SPDX license identifier for the
BSD 3-Clause "New" or "Revised" License (the license GitPython
uses): https://spdx.org/licenses/BSD-3-Clause.html

There is no requirement to use an SPDX license identifier here,
but it is one of the common approaches, and it has the advantage of
making unambiguously clear, when a package is published on PyPI,
exactly what license it uses.

In contrast, the license-related *classifier* is unchanged, since
no more specific classfifier than what is in use now is currently
available.

The combination should result in

    License: BSD License (BSD-3-Clause)

being shown under "Meta" on PyPI, as of the next PyPI release. This
can be seen in other projects that use this combination of license
keyword argument and license-related classifier, such as:
https://pypi.org/project/flask-restx/

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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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