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Merge pull request #1241 from Mbed-TLS/change-mpi-exp-mod-to-constant-time

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Change mbedtls_mpi_core_exp_mod() to constant time
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Janos Follath 2024-06-26 11:54:08 +01:00 committed by GitHub
commit d1615b814a
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2 changed files with 17 additions and 1 deletions
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3
library/bignum_core.h
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@ -621,6 +621,9 @@ size_t mbedtls_mpi_core_exp_mod_working_limbs(size_t AN_limbs, size_t E_limbs);
* \p X may be aliased to \p A, but not to \p RR or \p E, even if \p E_limbs ==
* \p AN_limbs.
*
* This function operates in constant time with respect
* to the values of \p A, \p N and \p E.
*
* \param[out] X The destination MPI, as a little endian array of length
* \p AN_limbs.
* \param[in] A The base MPI, as a little endian array of length \p AN_limbs.

15
tests/suites/test_suite_bignum_core.function
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@ -1303,14 +1303,27 @@ void mpi_core_exp_mod(char *input_N, char *input_A,
TEST_CALLOC(T, working_limbs);
/* Temporary because MEMSAN doesn't support assembly implementation see #1243 */
#if !defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN)
TEST_CF_SECRET(A, A_limbs * sizeof(mbedtls_mpi_uint));
TEST_CF_SECRET(N, N_limbs * sizeof(mbedtls_mpi_uint));
TEST_CF_SECRET(E, E_limbs * sizeof(mbedtls_mpi_uint));
#endif
mbedtls_mpi_core_exp_mod(Y, A, N, N_limbs, E, E_limbs, R2, T);
TEST_CF_PUBLIC(Y, N_limbs * sizeof(mbedtls_mpi_uint));
TEST_EQUAL(0, memcmp(X, Y, N_limbs * sizeof(mbedtls_mpi_uint)));
#if !defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN)
TEST_CF_SECRET(A, A_limbs * sizeof(mbedtls_mpi_uint));
TEST_CF_SECRET(N, N_limbs * sizeof(mbedtls_mpi_uint));
TEST_CF_SECRET(E, E_limbs * sizeof(mbedtls_mpi_uint));
#endif
/* Check when output aliased to input */
mbedtls_mpi_core_exp_mod(A, A, N, N_limbs, E, E_limbs, R2, T);
TEST_CF_PUBLIC(A, A_limbs * sizeof(mbedtls_mpi_uint));
TEST_EQUAL(0, memcmp(X, A, N_limbs * sizeof(mbedtls_mpi_uint)));
exit: