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v0.5.1
https://github.com/python/cpython
09 December 2020, 11:06:31 UTC
Revision 97136d71a78a4b6b816f7e14acc52be426efcb6f authored by Miss Islington (bot) on 21 November 2020, 09:12:21 UTC, committed by GitHub on 21 November 2020, 09:12:21 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 GH-1 from https://bugs.python.org/issue40791 .)
(cherry picked from commit 31729366e2bc09632e78f3896dbce0ae64914f28)

Co-authored-by: Devin Jeanpierre <jeanpierreda@google.com>
1 parent 0762e09
History
Tip revision: 97136d71a78a4b6b816f7e14acc52be426efcb6f authored by Miss Islington (bot) on 21 November 2020, 09:12:21 UTC
bpo-40791: Make compare_digest more constant-time. (GH-20444)
Tip revision: 97136d7
File Mode Size
windows-release
ci.yml -rw-r--r-- 2.6 KB
docs-steps.yml -rw-r--r-- 1.3 KB
macos-steps.yml -rw-r--r-- 768 bytes
posix-deps-apt.sh -rwxr-xr-x 580 bytes
posix-steps.yml -rw-r--r-- 2.5 KB
pr.yml -rw-r--r-- 2.6 KB
prebuild-checks.yml -rw-r--r-- 1.2 KB
windows-layout-steps.yml -rw-r--r-- 1.5 KB
windows-release.yml -rw-r--r-- 3.9 KB
windows-steps.yml -rw-r--r-- 1.5 KB
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