mbedtls/library/hmac_drbg.c

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