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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
View file

@ -6,6 +6,7 @@
#pragma once #pragma once
#include <AK/Memory.h>
#include <AK/OwnPtr.h> #include <AK/OwnPtr.h>
#include <AK/StringBuilder.h> #include <AK/StringBuilder.h>
#include <AK/StringView.h> #include <AK/StringView.h>
@ -124,12 +125,11 @@ public:
block0.apply_initialization_vector({ auth_tag.data, array_size(auth_tag.data) }); block0.apply_initialization_vector({ auth_tag.data, array_size(auth_tag.data) });
auto test_consistency = [&] { 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::Inconsistent;
return VerificationConsistency::Consistent; return VerificationConsistency::Consistent;
}; };
// FIXME: This block needs constant-time comparisons.
if (in.is_empty()) { if (in.is_empty()) {
out = {}; out = {};

3
Userland/Libraries/LibCrypto/PK/Code/EMSA_PSS.h
View file

@ -8,6 +8,7 @@
#include <AK/Array.h> #include <AK/Array.h>
#include <AK/Format.h> #include <AK/Format.h>
#include <AK/Memory.h>
#include <AK/Random.h> #include <AK/Random.h>
#include <AK/Vector.h> #include <AK/Vector.h>
#include <LibCrypto/PK/Code/Code.h> #include <LibCrypto/PK/Code/Code.h>
@ -140,7 +141,7 @@ public:
hash_fn.update(m_prime_buffer); hash_fn.update(m_prime_buffer);
auto H_prime = hash_fn.digest(); auto H_prime = hash_fn.digest();
if (__builtin_memcmp(message_hash.data, H_prime.data, HashFunction::DigestSize) != 0) if (!timing_safe_compare(message_hash.data, H_prime.data, HashFunction::DigestSize))
return VerificationConsistency::Inconsistent; return VerificationConsistency::Inconsistent;
return VerificationConsistency::Consistent; return VerificationConsistency::Consistent;