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LibCrypto: Use AK::timing_safe_compare to validate sensitive data

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Addresses one FIXME in GCM, and another similar issue in EMSA_PSS.
We should be using constant time memory comparisons in all of our
crypto code.
This commit is contained in:
Brian Gianforcaro 2022-03-12 22:06:46 -08:00 • committed by Brian Gianforcaro
parent 3ab2b90744
commit 0a5321b3f9
2 changed files with 4 additions and 3 deletions
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4
Userland/Libraries/LibCrypto/Cipher/Mode/GCM.h
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@ -6,6 +6,7 @@
#pragma once
#include <AK/Memory.h>
#include <AK/OwnPtr.h>
#include <AK/StringBuilder.h>
#include <AK/StringView.h>
@ -124,12 +125,11 @@ public:
block0.apply_initialization_vector({ auth_tag.data, array_size(auth_tag.data) });
auto test_consistency = [&] {
if (block0.block_size() != tag.size() || __builtin_memcmp(block0.bytes().data(), tag.data(), tag.size()) != 0)
if (block0.block_size() != tag.size() || !timing_safe_compare(block0.bytes().data(), tag.data(), tag.size()))
return VerificationConsistency::Inconsistent;
return VerificationConsistency::Consistent;
};
// FIXME: This block needs constant-time comparisons.
if (in.is_empty()) {
out = {};