Add key agreement for FFDH keys
Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 42ebfcf..7663269 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -1490,6 +1490,59 @@
return PSA_SUCCESS;
}
+#if defined(MBEDTLS_PSA_BUILTIN_ALG_FFDH)
+static psa_status_t psa_key_agreement_ffdh(const uint8_t *peer_key,
+ size_t peer_key_length,
+ const uint8_t *our_key,
+ size_t our_key_length,
+ uint8_t *shared_secret,
+ size_t shared_secret_size,
+ size_t *shared_secret_length)
+{
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ mbedtls_mpi P, G, X, GY, K;
+ const size_t calculated_shared_secret_size = peer_key_length;
+
+ if (peer_key_length != our_key_length ||
+ calculated_shared_secret_size > shared_secret_size) {
+ return PSA_ERROR_INVALID_ARGUMENT;
+ }
+
+ mbedtls_mpi_init(&P); mbedtls_mpi_init(&G);
+ mbedtls_mpi_init(&X); mbedtls_mpi_init(&GY);
+ mbedtls_mpi_init(&K);
+
+ status = psa_ffdh_set_prime_generator(peer_key_length, &P, &G);
+
+ if (status == PSA_SUCCESS) {
+ MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&X, our_key,
+ our_key_length));
+
+ MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&GY, peer_key,
+ peer_key_length));
+
+ /* Calculate shared secret public key: K = G^(XY) mod P */
+ MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&K, &GY, &X, &P, NULL));
+
+ MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&K, shared_secret,
+ calculated_shared_secret_size));
+
+ *shared_secret_length = calculated_shared_secret_size;
+ }
+cleanup:
+ mbedtls_mpi_free(&P); mbedtls_mpi_free(&G);
+ mbedtls_mpi_free(&X); mbedtls_mpi_free(&GY);
+ mbedtls_mpi_free(&K);
+
+ if (status == PSA_SUCCESS && ret != 0) {
+ return mbedtls_to_psa_error(ret);
+ }
+
+ return PSA_SUCCESS;
+}
+#endif /* MBEDTLS_PSA_BUILTIN_ALG_FFDH */
+
static psa_status_t psa_export_ffdh_public_key_internal(
const uint8_t *key_buffer,
size_t key_buffer_size,
@@ -6119,6 +6172,11 @@
return PSA_SUCCESS;
}
#endif
+#if defined(PSA_WANT_ALG_FFDH)
+ if (alg == PSA_ALG_FFDH) {
+ return PSA_SUCCESS;
+ }
+#endif
(void) alg;
return PSA_ERROR_NOT_SUPPORTED;
}
@@ -6707,6 +6765,22 @@
shared_secret_size,
shared_secret_length);
#endif /* MBEDTLS_PSA_BUILTIN_ALG_ECDH */
+
+#if defined(MBEDTLS_PSA_BUILTIN_ALG_FFDH)
+ case PSA_ALG_FFDH:
+ if (!PSA_KEY_TYPE_IS_DH_KEY_PAIR(psa_get_key_type(attributes))) {
+ return PSA_ERROR_INVALID_ARGUMENT;
+ }
+
+ return psa_key_agreement_ffdh(peer_key,
+ peer_key_length,
+ key_buffer,
+ key_buffer_size,
+ shared_secret,
+ shared_secret_size,
+ shared_secret_length);
+#endif /* MBEDTLS_PSA_BUILTIN_ALG_FFDH */
+
default:
(void) attributes;
(void) key_buffer;