Skip to content

[3.7] bpo-40791: Make compare_digest more constant-time. (GH-20444) #23438

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Nov 22, 2020
Merged

[3.7] bpo-40791: Make compare_digest more constant-time. (GH-20444) #23438

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Security/2020-05-28-06-06-47.bpo-40791.QGZClX.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Add ``volatile`` to the accumulator variable in ``hmac.compare_digest``, making constant-time-defeating optimizations less likely.
2 changes: 1 addition & 1 deletion Modules/_operator.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -735,7 +735,7 @@ _tscmp(const unsigned char *a, const unsigned char *b,
volatile const unsigned char *left;
volatile const unsigned char *right;
Py_ssize_t i;
unsigned char result;
volatile unsigned char result;

/* loop count depends on length of b */
length = len_b;
Expand Down