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Change mbedtls_mpi_core_mla() to be constant time

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Signed-off-by: Waleed Elmelegy <waleed.elmelegy@arm.com>
This commit is contained in:
Waleed Elmelegy 2024-05-21 18:17:22 +00:00
parent e146940714
commit 77bd479825
2 changed files with 21 additions and 1 deletions
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2
library/bignum_core.c
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@ -489,7 +489,7 @@ mbedtls_mpi_uint mbedtls_mpi_core_mla(mbedtls_mpi_uint *d, size_t d_len,
while (excess_len--) {
*d += c;
c = (*d < c);
c = mbedtls_ct_mpi_uint_if(mbedtls_ct_uint_lt(*d, c), 1, 0);
d++;
}

20
tests/suites/test_suite_bignum_core.function
View File

@ -770,16 +770,36 @@ void mpi_core_mla(char *input_A, char *input_B, char *input_S,
memcpy(a, A.p, A.n * sizeof(mbedtls_mpi_uint));
memcpy(x, X->p, X->n * sizeof(mbedtls_mpi_uint));
#if !defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN)
TEST_CF_SECRET(a, bytes);
TEST_CF_SECRET(B.p, B.n * sizeof(mbedtls_mpi_uint));
TEST_CF_SECRET(S.p, sizeof(mbedtls_mpi_uint));
#endif
/* 1a) A += B * s => we should get the correct carry */
TEST_EQUAL(mbedtls_mpi_core_mla(a, limbs, B.p, B.n, *S.p), *cy->p);
#if !defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN)
TEST_CF_PUBLIC(a, bytes);
TEST_CF_PUBLIC(B.p, B.n * sizeof(mbedtls_mpi_uint));
TEST_CF_PUBLIC(S.p, sizeof(mbedtls_mpi_uint));
#endif
/* 1b) A += B * s => we should get the correct result */
TEST_MEMORY_COMPARE(a, bytes, x, bytes);
if (A.n == B.n && memcmp(A.p, B.p, bytes) == 0) {
/* Check when A and B are aliased */
memcpy(a, A.p, A.n * sizeof(mbedtls_mpi_uint));
#if !defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN)
TEST_CF_SECRET(a, bytes);
TEST_CF_SECRET(S.p, sizeof(mbedtls_mpi_uint));
#endif
TEST_EQUAL(mbedtls_mpi_core_mla(a, limbs, a, limbs, *S.p), *cy->p);
#if !defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN)
TEST_CF_PUBLIC(a, bytes);
TEST_CF_PUBLIC(S.p, sizeof(mbedtls_mpi_uint));
#endif
TEST_MEMORY_COMPARE(a, bytes, x, bytes);
}