CTR_DRBG: support set_entropy_len() before seed()
mbedtls_ctr_drbg_seed() always set the entropy length to the default,
so a call to mbedtls_ctr_drbg_set_entropy_len() before seed() had no
effect. Change this to the more intuitive behavior that
set_entropy_len() sets the entropy length and seed() respects that and
only uses the default entropy length if there was no call to
set_entropy_len().
This removes the need for the test-only function
mbedtls_ctr_drbg_seed_entropy_len(). Just call
mbedtls_ctr_drbg_set_entropy_len() followed by
mbedtls_ctr_drbg_seed(), it works now.
diff --git a/library/ctr_drbg.c b/library/ctr_drbg.c
index c986b70..ae51d54 100644
--- a/library/ctr_drbg.c
+++ b/library/ctr_drbg.c
@@ -381,10 +381,6 @@
return( ret );
}
-/*
- * Non-public function wrapped by mbedtls_ctr_drbg_seed(). Necessary to allow
- * NIST tests to succeed (which require known length fixed entropy)
- */
/* CTR_DRBG_Instantiate with derivation function (SP 800-90A §10.2.1.3.2)
* mbedtls_ctr_drbg_seed_entropy_len(ctx, f_entropy, p_entropy,
* custom, len, entropy_len)
@@ -397,13 +393,11 @@
* and with outputs
* ctx = initial_working_state
*/
-int mbedtls_ctr_drbg_seed_entropy_len(
- mbedtls_ctr_drbg_context *ctx,
- int (*f_entropy)(void *, unsigned char *, size_t),
- void *p_entropy,
- const unsigned char *custom,
- size_t len,
- size_t entropy_len )
+int mbedtls_ctr_drbg_seed( mbedtls_ctr_drbg_context *ctx,
+ int (*f_entropy)(void *, unsigned char *, size_t),
+ void *p_entropy,
+ const unsigned char *custom,
+ size_t len )
{
int ret;
unsigned char key[MBEDTLS_CTR_DRBG_KEYSIZE];
@@ -415,7 +409,8 @@
ctx->f_entropy = f_entropy;
ctx->p_entropy = p_entropy;
- ctx->entropy_len = entropy_len;
+ if( ctx->entropy_len == 0 )
+ ctx->entropy_len = MBEDTLS_CTR_DRBG_ENTROPY_LEN;
ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL;
/*
@@ -434,17 +429,6 @@
return( 0 );
}
-int mbedtls_ctr_drbg_seed( mbedtls_ctr_drbg_context *ctx,
- int (*f_entropy)(void *, unsigned char *, size_t),
- void *p_entropy,
- const unsigned char *custom,
- size_t len )
-{
- return( mbedtls_ctr_drbg_seed_entropy_len( ctx, f_entropy, p_entropy,
- custom, len,
- MBEDTLS_CTR_DRBG_ENTROPY_LEN ) );
-}
-
/* CTR_DRBG_Generate with derivation function (SP 800-90A §10.2.1.5.2)
* mbedtls_ctr_drbg_random_with_add(ctx, output, output_len, additional, add_len)
* implements
@@ -708,8 +692,11 @@
mbedtls_printf( " CTR_DRBG (PR = TRUE) : " );
test_offset = 0;
- CHK( mbedtls_ctr_drbg_seed_entropy_len( &ctx, ctr_drbg_self_test_entropy,
- (void *) entropy_source_pr, nonce_pers_pr, 16, 32 ) );
+ mbedtls_ctr_drbg_set_entropy_len( &ctx, 32 );
+ CHK( mbedtls_ctr_drbg_seed( &ctx,
+ ctr_drbg_self_test_entropy,
+ (void *) entropy_source_pr,
+ nonce_pers_pr, 16 ) );
mbedtls_ctr_drbg_set_prediction_resistance( &ctx, MBEDTLS_CTR_DRBG_PR_ON );
CHK( mbedtls_ctr_drbg_random( &ctx, buf, MBEDTLS_CTR_DRBG_BLOCKSIZE ) );
CHK( mbedtls_ctr_drbg_random( &ctx, buf, MBEDTLS_CTR_DRBG_BLOCKSIZE ) );
@@ -729,8 +716,11 @@
mbedtls_ctr_drbg_init( &ctx );
test_offset = 0;
- CHK( mbedtls_ctr_drbg_seed_entropy_len( &ctx, ctr_drbg_self_test_entropy,
- (void *) entropy_source_nopr, nonce_pers_nopr, 16, 32 ) );
+ mbedtls_ctr_drbg_set_entropy_len( &ctx, 32 );
+ CHK( mbedtls_ctr_drbg_seed( &ctx,
+ ctr_drbg_self_test_entropy,
+ (void *) entropy_source_nopr,
+ nonce_pers_nopr, 16 ) );
CHK( mbedtls_ctr_drbg_random( &ctx, buf, 16 ) );
CHK( mbedtls_ctr_drbg_reseed( &ctx, NULL, 0 ) );
CHK( mbedtls_ctr_drbg_random( &ctx, buf, 16 ) );