gh-146287: Fix signed/unsigned mismatch in _hashlib_hmac_digest_size#148407
Merged
gpshead merged 2 commits intopython:mainfrom Apr 12, 2026
Merged
gh-146287: Fix signed/unsigned mismatch in _hashlib_hmac_digest_size#148407gpshead merged 2 commits intopython:mainfrom
gpshead merged 2 commits intopython:mainfrom
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…gned wrapping Change _hashlib_hmac_digest_size() return type from unsigned int to int so that a hypothetical negative return from EVP_MD_size() is not silently wrapped to a large positive value. Add an explicit check for negative digest_size in the legacy OpenSSL path, and use SystemError (not ValueError) since these conditions indicate internal invariant violations. Also add debug-build asserts to EVP_get_block_size and EVP_get_digest_size documenting that the hash context is always initialized.
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picnixz
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Apr 11, 2026
picnixz
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Apr 11, 2026
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
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Summary
_hashlib_hmac_digest_size()returnsunsigned int, but on the legacy OpenSSL 1.1.1 path it gets its value fromEVP_MD_size()which returnsint. A negative error return (-1) would silently wrap to UINT_MAX, bypassing the== 0error check and propagating a bogus size to callers.This can't be triggered through the Python API today (the
mdpointer is always validated before use), but the type mismatch means the safety net has a hole._hashlib_hmac_digest_size()return type toint< 0guard in the legacy OpenSSL pathSystemErrorinstead ofValueErrorfor these checks, sincethey represent internal invariant violations
assert()toEVP_get_block_sizeandEVP_get_digest_sizeto document that the hash context is always initialized
intinstead ofunsigned int_hashopenssl.c: Missing negative return check inEVP_get_block_sizeandEVP_get_digest_size#146287fixes #146287