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Add hmac_drbg_reseed()
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@ -135,6 +135,19 @@ void hmac_drbg_set_entropy_len( hmac_drbg_context *ctx,
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void hmac_drbg_update( hmac_drbg_context *ctx,
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void hmac_drbg_update( hmac_drbg_context *ctx,
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const unsigned char *additional, size_t add_len );
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const unsigned char *additional, size_t add_len );
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/**
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* \brief HMAC_DRBG reseeding (extracts data from entropy source)
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*
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* \param ctx HMAC_DRBG context
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* \param additional Additional data to add to state (Can be NULL)
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* \param len Length of additional data
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*
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* \return 0 if successful, or
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* POLARSSL_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
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*/
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int hmac_drbg_reseed( hmac_drbg_context *ctx,
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const unsigned char *additional, size_t len );
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/**
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/**
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* \brief HMAC_DRBG generate random with additional update input
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* \brief HMAC_DRBG generate random with additional update input
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*
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*
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@ -84,6 +84,42 @@ int hmac_drbg_init_buf( hmac_drbg_context *ctx,
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return( 0 );
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return( 0 );
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}
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}
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/*
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* HMAC_DRBG reseeding (10.1.2.4)
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*/
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int hmac_drbg_reseed( hmac_drbg_context *ctx,
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const unsigned char *additional, size_t len )
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{
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unsigned char seed[HMAC_DRBG_MAX_SEED_INPUT];
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size_t seedlen;
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if( ctx->entropy_len + len > HMAC_DRBG_MAX_SEED_INPUT )
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return( POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG );
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memset( seed, 0, HMAC_DRBG_MAX_SEED_INPUT );
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/* 1a. Gather entropy_len bytes of entropy for the seed */
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if( ctx->f_entropy( ctx->p_entropy, seed, ctx->entropy_len ) != 0 )
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return( POLARSSL_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED );
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seedlen = ctx->entropy_len;
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/* 1b. Append additional data if any */
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if( additional != NULL && len != 0 )
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{
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memcpy( seed + seedlen, additional, len );
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seedlen += len;
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}
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/* 2. Update state */
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hmac_drbg_update( ctx, seed, seedlen );
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/* 3. Reset reseed_counter (TODO) */
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/* 4. Done */
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return( 0 );
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}
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/*
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/*
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* HMAC_DRBG initialisation
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* HMAC_DRBG initialisation
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*/
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*/
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@ -95,63 +131,41 @@ int hmac_drbg_init( hmac_drbg_context *ctx,
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size_t len )
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size_t len )
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{
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{
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int ret;
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int ret;
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unsigned char seed[HMAC_DRBG_MAX_SEED_INPUT];
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size_t entropy_len;
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size_t seedlen, init_entropy_len;
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memset( ctx, 0, sizeof( hmac_drbg_context ) );
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memset( ctx, 0, sizeof( hmac_drbg_context ) );
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if( ( ret = md_init_ctx( &ctx->md_ctx, md_info ) ) != 0 )
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if( ( ret = md_init_ctx( &ctx->md_ctx, md_info ) ) != 0 )
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return( ret );
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return( ret );
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/*
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/* Set initial working state */
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* See SP800-57 5.6.1 (p. 65-66) for the security strength provided by
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memset( ctx->V, 0x01, md_info->size );
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* each hash function, then according to SP800-90A rev1 10.1 table 2,
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/* ctx->K is already 0 */
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* min_entropy_len (in bits) is security_strength.
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*/
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ctx->entropy_len = md_info->size <= 20 ? 16 : /* 160-bits hash -> 128 */
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md_info->size <= 28 ? 24 : /* 224-bits hash -> 192 */
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32; /* better (256+) -> 256 */
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ctx->f_entropy = f_entropy;
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ctx->f_entropy = f_entropy;
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ctx->p_entropy = p_entropy;
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ctx->p_entropy = p_entropy;
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/*
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* See SP800-57 5.6.1 (p. 65-66) for the security strength provided by
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* each hash function, then according to SP800-90A rev1 10.1 table 2,
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* min_entropy_len (in bits) is security_strength.
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*
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* (This also matches the sizes used in the NIST test vectors.)
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*/
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entropy_len = md_info->size <= 20 ? 16 : /* 160-bits hash -> 128 bits */
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md_info->size <= 28 ? 24 : /* 224-bits hash -> 192 bits */
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32; /* better (256+) -> 256 bits */
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/*
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/*
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* For initialisation, use more entropy to emulate a nonce
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* For initialisation, use more entropy to emulate a nonce
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* (Again, matches test vectors.)
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*/
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*/
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init_entropy_len = ctx->entropy_len * 3 / 2;
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ctx->entropy_len = entropy_len * 3 / 2;
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if( init_entropy_len + len > HMAC_DRBG_MAX_SEED_INPUT )
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if( ( ret = hmac_drbg_reseed( ctx, custom, len ) ) != 0 )
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return( POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG );
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return( ret );
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memset( seed, 0, HMAC_DRBG_MAX_SEED_INPUT );
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ctx->entropy_len = entropy_len;
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/*
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* Gather init_entropy_len bytes of entropy for initial seed
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*/
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if( 0 != ctx->f_entropy( ctx->p_entropy, seed,
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init_entropy_len ) )
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{
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return( POLARSSL_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED );
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}
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seedlen = init_entropy_len;
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/*
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* Add additional data
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*/
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if( custom != NULL && len != 0 )
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{
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memcpy( seed + seedlen, custom, len );
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seedlen += len;
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}
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/*
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* Set initial state and update it with initialisation data
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*/
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memset( ctx->V, 0x01, md_info->size );
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/* ctx->K is already 0 */
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hmac_drbg_update( ctx, seed, seedlen );
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return( 0 );
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return( 0 );
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}
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}
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