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Suppress a harmless variable-time optimization by clang in memczero #728

Merged
merged 2 commits into from
Mar 27, 2020
Merged

Suppress a harmless variable-time optimization by clang in memczero #728

merged 2 commits into from
Mar 27, 2020

Commits on Mar 27, 2020

  1. Suppress a harmless variable-time optimization by clang in memczero 

    This has been not been caught by the new constant-time tests because
valgrind currently gives us a zero exit code even if finds errors, see
bitcoin-core#723 (comment) .

This commit also simplifies the arithmetic in memczero.

Note that the timing leak here was the bit whether a secret key was
out of range. This leak is harmless and not exploitable. It is just
our overcautious practice to prefer constant-time code even here.
    @real-or-random
    real-or-random committed Mar 27, 2020
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  2. Add test for memczero()

    @real-or-random
    real-or-random committed Mar 27, 2020
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