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mbedtls_psa_ffdh_generate_key: optimize code and return fixed key size

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Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
This commit is contained in:
Przemek Stekiel 2023-05-05 09:53:37 +02:00
parent 2488afcd71
commit e1621a460a
1 changed files with 13 additions and 14 deletions
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27
library/psa_crypto_ffdh.c
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@ -231,24 +231,23 @@ psa_status_t mbedtls_psa_ffdh_generate_key(
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
mbedtls_mpi_init(&P); mbedtls_mpi_init(&X);
(void) attributes;
status = mbedtls_psa_ffdh_set_prime_generator(
PSA_BITS_TO_BYTES(attributes->core.bits), &P, NULL);
status = mbedtls_psa_ffdh_set_prime_generator(key_buffer_size, &P, NULL);
if (status == PSA_SUCCESS) {
/* RFC7919: Traditional finite field Diffie-Hellman has each peer choose their
secret exponent from the range [2, P-2].
Select random value in range [3, P-1] and decrease it by 1. */
MBEDTLS_MPI_CHK(mbedtls_mpi_random(&X, 3, &P, mbedtls_psa_get_random,
MBEDTLS_PSA_RANDOM_STATE));
MBEDTLS_MPI_CHK(mbedtls_mpi_sub_int(&X, &X, 1));
*key_buffer_length = mbedtls_mpi_size(&X);
MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&X, key_buffer,
key_buffer_size));
if (status != PSA_SUCCESS) {
goto cleanup;
}
/* RFC7919: Traditional finite field Diffie-Hellman has each peer choose their
secret exponent from the range [2, P-2].
Select random value in range [3, P-1] and decrease it by 1. */
MBEDTLS_MPI_CHK(mbedtls_mpi_random(&X, 3, &P, mbedtls_psa_get_random,
MBEDTLS_PSA_RANDOM_STATE));
MBEDTLS_MPI_CHK(mbedtls_mpi_sub_int(&X, &X, 1));
MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&X, key_buffer, key_buffer_size));
*key_buffer_length = key_buffer_size;
cleanup:
mbedtls_mpi_free(&P); mbedtls_mpi_free(&X);
if (status == PSA_SUCCESS && ret != 0) {