261 lines
7 KiB
C
261 lines
7 KiB
C
/*
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* HMAC_DRBG implementation (NIST SP 800-90)
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*
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* Copyright (C) 2014, Brainspark B.V.
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*
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* This file is part of PolarSSL (http://www.polarssl.org)
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* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
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*
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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/*
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* The NIST SP 800-90A DRBGs are described in the following publication.
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* http://csrc.nist.gov/publications/nistpubs/800-90A/SP800-90A.pdf
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* References below are based on rev. 1 (January 2012).
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*/
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#include "polarssl/config.h"
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#if defined(POLARSSL_HMAC_DRBG_C)
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#include "polarssl/hmac_drbg.h"
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/*
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* HMAC_DRBG update, using optional additional data (10.1.2.2)
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*/
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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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{
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size_t md_len = ctx->md_ctx.md_info->size;
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unsigned char rounds = ( additional != NULL && add_len != 0 ) ? 2 : 1;
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unsigned char sep[1];
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for( sep[0] = 0; sep[0] < rounds; sep[0]++ )
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{
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/* Step 1 or 4 */
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md_hmac_starts( &ctx->md_ctx, ctx->K, md_len );
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md_hmac_update( &ctx->md_ctx, ctx->V, md_len );
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md_hmac_update( &ctx->md_ctx, sep, 1 );
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if( rounds == 2 )
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md_hmac_update( &ctx->md_ctx, additional, add_len );
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md_hmac_finish( &ctx->md_ctx, ctx->K );
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/* Step 2 or 5 */
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md_hmac_starts( &ctx->md_ctx, ctx->K, md_len );
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md_hmac_update( &ctx->md_ctx, ctx->V, md_len );
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md_hmac_finish( &ctx->md_ctx, ctx->V );
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}
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}
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/*
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* Simplified HMAC_DRBG initialisation (for use with deterministic ECDSA)
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*/
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int hmac_drbg_init_buf( hmac_drbg_context *ctx,
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const md_info_t * md_info,
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const unsigned char *data, size_t data_len )
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{
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int ret;
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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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return( ret );
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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, data, data_len );
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return( 0 );
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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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* HMAC_DRBG initialisation
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*/
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int hmac_drbg_init( hmac_drbg_context *ctx,
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const md_info_t * md_info,
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int (*f_entropy)(void *, unsigned char *, size_t),
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void *p_entropy,
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const unsigned char *custom,
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size_t len )
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{
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int ret;
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size_t entropy_len;
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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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return( ret );
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/* Set initial working state */
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memset( ctx->V, 0x01, md_info->size );
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/* ctx->K is already 0 */
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ctx->f_entropy = f_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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* 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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ctx->entropy_len = entropy_len * 3 / 2;
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if( ( ret = hmac_drbg_reseed( ctx, custom, len ) ) != 0 )
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return( ret );
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ctx->entropy_len = entropy_len;
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return( 0 );
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}
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/*
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* Set entropy length grabbed for reseeds
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*/
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void hmac_drbg_set_entropy_len( hmac_drbg_context *ctx, size_t len )
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{
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ctx->entropy_len = len;
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}
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/*
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* HMAC_DRBG random function with optional additional data (10.1.2.5)
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*/
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int hmac_drbg_random_with_add( void *p_rng,
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unsigned char *output, size_t out_len,
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const unsigned char *additional, size_t add_len )
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{
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hmac_drbg_context *ctx = (hmac_drbg_context *) p_rng;
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size_t md_len = md_get_size( ctx->md_ctx.md_info );
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size_t left = out_len;
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unsigned char *out = output;
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/* 1. Check reseed counter (TODO) */
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/* 2. Use additional data if any */
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if( additional != NULL && add_len != 0 )
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hmac_drbg_update( ctx, additional, add_len );
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/* 3, 4, 5. Generate bytes */
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while( left != 0 )
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{
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size_t use_len = left > md_len ? md_len : left;
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md_hmac_starts( &ctx->md_ctx, ctx->K, md_len );
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md_hmac_update( &ctx->md_ctx, ctx->V, md_len );
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md_hmac_finish( &ctx->md_ctx, ctx->V );
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memcpy( out, ctx->V, use_len );
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out += use_len;
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left -= use_len;
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}
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/* 6. Update */
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hmac_drbg_update( ctx, additional, add_len );
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/* 7. Update reseed counter (TODO) */
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/* 8. Done */
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return( 0 );
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}
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/*
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* HMAC_DRBG random function
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*/
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int hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len )
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{
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return( hmac_drbg_random_with_add( p_rng, output, out_len, NULL, 0 ) );
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}
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/*
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* Free an HMAC_DRBG context
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*/
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void hmac_drbg_free( hmac_drbg_context *ctx )
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{
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if( ctx == NULL )
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return;
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md_free_ctx( &ctx->md_ctx );
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memset( ctx, 0, sizeof( hmac_drbg_context ) );
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}
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#if defined(POLARSSL_SELF_TEST)
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#include <stdio.h>
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/*
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* Checkup routine
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*/
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int hmac_drbg_self_test( int verbose )
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{
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if( verbose != 0 )
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printf( "\n" );
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return( 0 );
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}
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#endif /* POLARSSL_SELF_TEST */
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#endif /* POLARSSL_HMAC_DRBG_C */
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