Add more checks and references
diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c
index 7e361f4..4195bf1 100644
--- a/library/hmac_drbg.c
+++ b/library/hmac_drbg.c
@@ -85,7 +85,7 @@
}
/*
- * HMAC_DRBG reseeding (10.1.2.4)
+ * HMAC_DRBG reseeding: 10.1.2.4 (arabic) + 9.2 (Roman)
*/
int hmac_drbg_reseed( hmac_drbg_context *ctx,
const unsigned char *additional, size_t len )
@@ -93,18 +93,22 @@
unsigned char seed[HMAC_DRBG_MAX_SEED_INPUT];
size_t seedlen;
- if( ctx->entropy_len + len > HMAC_DRBG_MAX_SEED_INPUT )
+ /* III. Check input length */
+ if( len > HMAC_DRBG_MAX_INPUT ||
+ ctx->entropy_len + len > HMAC_DRBG_MAX_SEED_INPUT )
+ {
return( POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG );
+ }
memset( seed, 0, HMAC_DRBG_MAX_SEED_INPUT );
- /* 1a. Gather entropy_len bytes of entropy for the seed */
+ /* IV. Gather entropy_len bytes of entropy for the seed */
if( ctx->f_entropy( ctx->p_entropy, seed, ctx->entropy_len ) != 0 )
return( POLARSSL_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED );
seedlen = ctx->entropy_len;
- /* 1b. Append additional data if any */
+ /* 1. Concatenate entropy and additional data if any */
if( additional != NULL && len != 0 )
{
memcpy( seed + seedlen, additional, len );
@@ -122,7 +126,7 @@
}
/*
- * HMAC_DRBG initialisation
+ * HMAC_DRBG initialisation (10.1.2.3 + 9.1)
*/
int hmac_drbg_init( hmac_drbg_context *ctx,
const md_info_t * md_info,
@@ -199,7 +203,8 @@
}
/*
- * HMAC_DRBG random function with optional additional data (10.1.2.5)
+ * HMAC_DRBG random function with optional additional data:
+ * 10.1.2.5 (arabic) + 9.3 (Roman)
*/
int hmac_drbg_random_with_add( void *p_rng,
unsigned char *output, size_t out_len,
@@ -211,13 +216,23 @@
size_t left = out_len;
unsigned char *out = output;
- /* 1. Check reseed counter and PR */
+ /* II. Check request length */
+ if( out_len > HMAC_DRBG_MAX_REQUEST )
+ return( POLARSSL_ERR_HMAC_DRBG_REQUEST_TOO_BIG );
+
+ /* III. Check input length */
+ if( add_len > HMAC_DRBG_MAX_INPUT )
+ return( POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG );
+
+ /* 1. (aka VII and IX) Check reseed counter and PR */
if( ctx->f_entropy != NULL &&
( ctx->prediction_resistance == HMAC_DRBG_PR_ON ||
ctx->reseed_counter > ctx->reseed_interval ) )
{
if( ( ret = hmac_drbg_reseed( ctx, additional, add_len ) ) != 0 )
return( ret );
+
+ add_len = 0; /* VII.4 */
}
/* 2. Use additional data if any */
