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[3.9] bpo-40695: Limit hashlib builtin hash fallback (GH-20259) #20377

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Merged
merged 1 commit into from
May 25, 2020
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[3.9] bpo-40695: Limit hashlib builtin hash fallback (GH-20259) #20377

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5 changes: 3 additions & 2 deletions Lib/hashlib.py
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Original file line number Diff line number Diff line change
Expand Up @@ -127,8 +127,9 @@ def __get_openssl_constructor(name):
# SHA3/shake are available in OpenSSL 1.1.1+
f = getattr(_hashlib, 'openssl_' + name)
# Allow the C module to raise ValueError. The function will be
# defined but the hash not actually available thanks to OpenSSL.
f()
# defined but the hash not actually available. Don't fall back to
# builtin if the current security policy blocks a digest, bpo#40695.
f(usedforsecurity=False)
# Use the C function directly (very fast)
return f
except (AttributeError, ValueError):
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2020-05-20-13-03-28.bpo-40695.lr4aIS.rst
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@@ -0,0 +1,3 @@
:mod:`hashlib` no longer falls back to builtin hash implementations when
OpenSSL provides a hash digest and the algorithm is blocked by security
policy.