Add output_length parameter to mbedtls_gcm_finish
Without this parameter, it would be hard for callers to know how many bytes
of output the function wrote into the output buffer. It would be possible,
since the cumulated output must have the same length as the cumulated input,
but it would be cumbersome for the caller to keep track.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/cipher.c b/library/cipher.c
index 4f56b52..546cace 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -1109,9 +1109,14 @@
#if defined(MBEDTLS_GCM_C)
if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
+ {
+ size_t output_length;
+ /* The code here doesn't yet support alternative implementations
+ * that can delay up to a block of output. */
return( mbedtls_gcm_finish( (mbedtls_gcm_context *) ctx->cipher_ctx,
- NULL, 0,
+ NULL, 0, &output_length,
tag, tag_len ) );
+ }
#endif
#if defined(MBEDTLS_CHACHAPOLY_C)
@@ -1158,12 +1163,16 @@
#if defined(MBEDTLS_GCM_C)
if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
{
+ size_t output_length;
+ /* The code here doesn't yet support alternative implementations
+ * that can delay up to a block of output. */
+
if( tag_len > sizeof( check_tag ) )
return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
if( 0 != ( ret = mbedtls_gcm_finish(
(mbedtls_gcm_context *) ctx->cipher_ctx,
- NULL, 0,
+ NULL, 0, &output_length,
check_tag, tag_len ) ) )
{
return( ret );