tar.py: Always use extraction filter - #2192
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The `tarfile` extraction filter support from Python 3.12 was backported to older Python releases. However, distro packages of Python < 3.12 may not include that backport. Import the latest upstream version to be able to use extraction filters on all Python versions.
This was introduced in Python 3.14. While it was also backported to older versions, the backport may not be available everywhere.
This aligns the behavior across Python versions, offering some protection from unusual and possibly malicious tar files. On Python versions lower than 3.12, this uses the imported copy of `tarfile.py`.
The `tar` filter catches attempts to extract files outside the destination directory but does not catch hardlink targets outside the destination directory. The `data` filter catches both but doesn't preserve symlinks, which may break, e.g., rootfs tarball extraction. Define a custom extraction filter that uses the `data` filter except for symlinks where the `tar` filter is used. This filter replaces the incomplete checks of `_assert_safe()`, which was invoked before extraction, which meant that the checks may already have been outdated during actual extraction.
Reported-by: Gjoko Krstic <gjoko@zeroscience.mk>
juergbi
requested review from
BenjaminSchubert,
abderrahim,
cs-shadow and
gtristan
as code owners
September 15, 2026 11:18
abderrahim
approved these changes
Sep 15, 2026
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Extraction in the tar plugin currently has two code paths. Using extraction filters on Python 3.12+ and relying on custom safety checks on older Python versions. This PR switches to using an extraction filter on all supported Python versions by importing a copy of Python's
tarfile.pyfor use on older Python versions. This allows replacing the custom safety checks with a combination of upstream Python filters that are more widely tested.