Migrate MAC finish calls into the software driver
Step 3/x in moving the driver. Separate commits should make for easier
review.
Additional changes on top of code movement:
* Copied the implementation of safer_memcmp from psa_crypto into
psa_cipher_mac since the mac_verify driver implementation
depends on it, and it isn't available through external linkage
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
diff --git a/library/psa_crypto_mac.c b/library/psa_crypto_mac.c
index 252afca..72386d8 100644
--- a/library/psa_crypto_mac.c
+++ b/library/psa_crypto_mac.c
@@ -457,18 +457,77 @@
}
}
+static psa_status_t mac_finish_internal( mbedtls_psa_mac_operation_t *operation,
+ uint8_t *mac,
+ size_t mac_size )
+{
+ if( ! operation->key_set )
+ return( PSA_ERROR_BAD_STATE );
+ if( operation->iv_required && ! operation->iv_set )
+ return( PSA_ERROR_BAD_STATE );
+
+ if( mac_size < operation->mac_size )
+ return( PSA_ERROR_BUFFER_TOO_SMALL );
+
+#if defined(BUILTIN_ALG_CMAC)
+ if( operation->alg == PSA_ALG_CMAC )
+ {
+ uint8_t tmp[PSA_BLOCK_CIPHER_BLOCK_MAX_SIZE];
+ int ret = mbedtls_cipher_cmac_finish( &operation->ctx.cmac, tmp );
+ if( ret == 0 )
+ memcpy( mac, tmp, operation->mac_size );
+ mbedtls_platform_zeroize( tmp, sizeof( tmp ) );
+ return( mbedtls_to_psa_error( ret ) );
+ }
+ else
+#endif /* BUILTIN_ALG_CMAC */
+#if defined(BUILTIN_ALG_HMAC)
+ if( PSA_ALG_IS_HMAC( operation->alg ) )
+ {
+ return( psa_hmac_finish_internal( &operation->ctx.hmac,
+ mac, operation->mac_size ) );
+ }
+ else
+#endif /* BUILTIN_ALG_HMAC */
+ {
+ /* This shouldn't happen if `operation` was initialized by
+ * a setup function. */
+ return( PSA_ERROR_BAD_STATE );
+ }
+}
+
static psa_status_t mac_sign_finish(
mbedtls_psa_mac_operation_t *operation,
uint8_t *mac,
size_t mac_size,
size_t *mac_length )
{
- /* To be fleshed out in a subsequent commit */
- (void) operation;
- (void) mac;
- (void) mac_size;
- (void) mac_length;
- return( PSA_ERROR_NOT_SUPPORTED );
+ psa_status_t status;
+
+ if( operation->alg == 0 )
+ return( PSA_ERROR_BAD_STATE );
+
+ if( ! operation->is_sign )
+ return( PSA_ERROR_BAD_STATE );
+
+ status = mac_finish_internal( operation, mac, mac_size );
+
+ if( status == PSA_SUCCESS )
+ *mac_length = operation->mac_size;
+
+ return( status );
+}
+
+/* constant-time buffer comparison */
+static inline int safer_memcmp( const uint8_t *a, const uint8_t *b, size_t n )
+{
+ size_t i;
+ unsigned char diff = 0;
+
+ for( i = 0; i < n; i++ )
+ diff |= a[i] ^ b[i];
+
+ return( diff );
}
static psa_status_t mac_verify_finish(
@@ -476,11 +535,32 @@
const uint8_t *mac,
size_t mac_length )
{
- /* To be fleshed out in a subsequent commit */
- (void) operation;
- (void) mac;
- (void) mac_length;
- return( PSA_ERROR_NOT_SUPPORTED );
+ uint8_t actual_mac[PSA_MAC_MAX_SIZE];
+ psa_status_t status;
+
+ if( operation->alg == 0 )
+ return( PSA_ERROR_BAD_STATE );
+
+ if( operation->is_sign )
+ return( PSA_ERROR_BAD_STATE );
+
+ if( operation->mac_size != mac_length )
+ {
+ status = PSA_ERROR_INVALID_SIGNATURE;
+ goto cleanup;
+ }
+
+ status = mac_finish_internal( operation, actual_mac, sizeof( actual_mac ) );
+ if( status != PSA_SUCCESS )
+ goto cleanup;
+
+ if( safer_memcmp( mac, actual_mac, mac_length ) != 0 )
+ status = PSA_ERROR_INVALID_SIGNATURE;
+
+cleanup:
+ mbedtls_platform_zeroize( actual_mac, sizeof( actual_mac ) );
+
+ return( status );
}
#endif /* MBEDTLS_PSA_BUILTIN_MAC || PSA_CRYPTO_DRIVER_TEST */