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v0.8.1
https://github.com/python/cpython
09 December 2020, 11:06:31 UTC
Revision 31729366e2bc09632e78f3896dbce0ae64914f28 authored by Devin Jeanpierre on 21 November 2020, 08:55:23 UTC, committed by GitHub on 21 November 2020, 08:55:23 UTC 
bpo-40791: Make compare_digest more constant-time. (GH-20444)
 
* bpo-40791: Make compare_digest more constant-time.

The existing volatile `left`/`right` pointers guarantee that the reads will all occur, but does not guarantee that they will be _used_. So a compiler can still short-circuit the loop, saving e.g. the overhead of doing the xors and especially the overhead of the data dependency between `result` and the reads. That would change performance depending on where the first unequal byte occurs. This change removes that optimization.

(This is change #1 from https://bugs.python.org/issue40791 .)
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History
Tip revision: 31729366e2bc09632e78f3896dbce0ae64914f28 authored by Devin Jeanpierre on 21 November 2020, 08:55:23 UTC
bpo-40791: Make compare_digest more constant-time. (GH-20444)
Tip revision: 3172936
File Mode Size
ax_c_float_words_bigendian.m4 -rw-r--r-- 3.1 KB
ax_check_openssl.m4 -rw-r--r-- 4.1 KB
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