Fix symlink-following arbitrary file write in archive extraction#8303
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Extractor.extract() called shutil.rmtree(output_path, ignore_errors=True) before extracting. Since Python 3.8, shutil.rmtree() raises OSError on a symlink pointing to a directory, which ignore_errors=True silently swallows. An attacker with write access to a shared cache directory could pre-plant a symlink at the predictable extraction output path; rmtree would no-op on it, and extraction would then follow the symlink and write archive contents into the attacker-chosen target, yielding arbitrary file write as the victim. The existing safemembers() zip-slip mitigation only validates member names and is blind to the output directory itself being a symlink. Remove the symlink itself before extracting so contents can no longer be written through it.
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Extractor.extract() called shutil.rmtree(output_path, ignore_errors=True) before extracting. Since Python 3.8, shutil.rmtree() raises OSError on a symlink pointing to a directory, which ignore_errors=True silently swallows. An attacker with write access to a shared cache directory could pre-plant a symlink at the predictable extraction output path; rmtree would no-op on it, and extraction would then follow the symlink and write archive contents into the attacker-chosen target, yielding arbitrary file write as the victim.
The existing safemembers() zip-slip mitigation only validates member names and is blind to the output directory itself being a symlink.
Remove the symlink itself before extracting so contents can no longer be written through it.
#8296