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Fix and improve documentation of HMAC DRBG

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- a comment regarding the implementation of hmac_drbg_reseed_core()
  was misplaced.
- add more references to the standard, and add details on how the
  comments in the code refer to various parts of the standard.
This commit is contained in:
Hanno Becker 2019-08-27 09:22:09 +01:00
parent b3a06e66d8
commit 31c95e1e94
1 changed files with 11 additions and 3 deletions
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14
library/hmac_drbg.c
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@ -148,6 +148,11 @@ int mbedtls_hmac_drbg_seed_buf( mbedtls_hmac_drbg_context *ctx,
return( 0 ); return( 0 );
} }
/*
* Internal function used both for seeding and reseeding the DRBG.
* Comments starting with arabic numbers refer to section 10.1.2.4
* of SP800-90A, while roman numbers refer to section 9.2.
*/
static int hmac_drbg_reseed_core( mbedtls_hmac_drbg_context *ctx, static int hmac_drbg_reseed_core( mbedtls_hmac_drbg_context *ctx,
const unsigned char *additional, size_t len, const unsigned char *additional, size_t len,
int use_nonce ) int use_nonce )
@ -182,8 +187,8 @@ static int hmac_drbg_reseed_core( mbedtls_hmac_drbg_context *ctx,
} }
seedlen += ctx->entropy_len; seedlen += ctx->entropy_len;
/* IV'. For initial seeding, allow adding of nonce generated /* For initial seeding, allow adding of nonce generated
* from the entropy source. See Sect 8.6.7 in SP800-90A. */ * from the entropy source. See Sect 8.6.7 in SP800-90A. */
if( use_nonce ) if( use_nonce )
{ {
/* Note: We don't merge the two calls to f_entropy() in order /* Note: We don't merge the two calls to f_entropy() in order
@ -225,7 +230,7 @@ exit:
} }
/* /*
* HMAC_DRBG reseeding: 10.1.2.4 (arabic) + 9.2 (Roman) * HMAC_DRBG reseeding: 10.1.2.4 + 9.2
*/ */
int mbedtls_hmac_drbg_reseed( mbedtls_hmac_drbg_context *ctx, int mbedtls_hmac_drbg_reseed( mbedtls_hmac_drbg_context *ctx,
const unsigned char *additional, size_t len ) const unsigned char *additional, size_t len )
@ -236,6 +241,9 @@ int mbedtls_hmac_drbg_reseed( mbedtls_hmac_drbg_context *ctx,
/* /*
* HMAC_DRBG initialisation (10.1.2.3 + 9.1) * HMAC_DRBG initialisation (10.1.2.3 + 9.1)
*
* The nonce is not passed as a separate parameter but extracted
* from the entropy source as suggested in 8.6.7.
*/ */
int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx, int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx,
const mbedtls_md_info_t * md_info, const mbedtls_md_info_t * md_info,