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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 800-90A DRBGs are described in the following publication.
* http://csrc.nist.gov/publications/nistpubs/800-90A/SP800-90A.pdf
* References below are based on rev. 1 (January 2012).
*/
#if !defined(POLARSSL_CONFIG_FILE)
#include "polarssl/config.h"
#else
#include POLARSSL_CONFIG_FILE
#endif
#if defined(POLARSSL_HMAC_DRBG_C)
#include "polarssl/hmac_drbg.h"
#if defined(POLARSSL_FS_IO)
#include <stdio.h>
#endif
#if defined(POLARSSL_PLATFORM_C)
#include "polarssl/platform.h"
#else
#define polarssl_printf printf
#endif
/* Implementation that should never be optimized out by the compiler */
static void polarssl_zeroize( void *v, size_t n ) {
volatile unsigned char *p = v; while( n-- ) *p++ = 0;
}
/*
* HMAC_DRBG update, using optional additional data (10.1.2.2)
*/
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];
unsigned char K[POLARSSL_MD_MAX_SIZE];
for( sep[0] = 0; sep[0] < rounds; sep[0]++ )
{
/* Step 1 or 4 */
md_hmac_reset( &ctx->md_ctx );
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, K );
/* Step 2 or 5 */
md_hmac_starts( &ctx->md_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 (for use with deterministic ECDSA)
*/
int hmac_drbg_init_buf( 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 ) );
md_init( &ctx->md_ctx );
if( ( ret = md_init_ctx( &ctx->md_ctx, md_info ) ) != 0 )
return( ret );
/*
* Set initial working state.
* Use the V memory location, which is currently all 0, to initialize the
* MD context with an all-zero key. Then set V to its initial value.
*/
md_hmac_starts( &ctx->md_ctx, ctx->V, md_info->size );
memset( ctx->V, 0x01, md_info->size );
hmac_drbg_update( ctx, data, data_len );
return( 0 );
}
/*
* HMAC_DRBG reseeding: 10.1.2.4 (arabic) + 9.2 (Roman)
*/
int hmac_drbg_reseed( hmac_drbg_context *ctx,
const unsigned char *additional, size_t len )
{
unsigned char seed[POLARSSL_HMAC_DRBG_MAX_SEED_INPUT];
size_t seedlen;
/* III. Check input length */
if( len > POLARSSL_HMAC_DRBG_MAX_INPUT ||
ctx->entropy_len + len > POLARSSL_HMAC_DRBG_MAX_SEED_INPUT )
{
return( POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG );
}
memset( seed, 0, POLARSSL_HMAC_DRBG_MAX_SEED_INPUT );
/* IV. Gather entropy_len bytes of entropy for the seed */
if( ctx->f_entropy( ctx->p_entropy, seed, ctx->entropy_len ) != 0 )
return( POLARSSL_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED );
seedlen = ctx->entropy_len;
/* 1. Concatenate entropy and additional data if any */
if( additional != NULL && len != 0 )
{
memcpy( seed + seedlen, additional, len );
seedlen += len;
}
/* 2. Update state */
hmac_drbg_update( ctx, seed, seedlen );
/* 3. Reset reseed_counter */
ctx->reseed_counter = 1;
/* 4. Done */
return( 0 );
}
/*
* HMAC_DRBG initialisation (10.1.2.3 + 9.1)
*/
int hmac_drbg_init( hmac_drbg_context *ctx,
const md_info_t * md_info,
int (*f_entropy)(void *, unsigned char *, size_t),
void *p_entropy,
const unsigned char *custom,
size_t len )
{
int ret;
size_t entropy_len;
memset( ctx, 0, sizeof( hmac_drbg_context ) );
md_init( &ctx->md_ctx );
if( ( ret = md_init_ctx( &ctx->md_ctx, md_info ) ) != 0 )
return( ret );
/*
* Set initial working state.
* Use the V memory location, which is currently all 0, to initialize the
* MD context with an all-zero key. Then set V to its initial value.
*/
md_hmac_starts( &ctx->md_ctx, ctx->V, md_info->size );
memset( ctx->V, 0x01, md_info->size );
ctx->f_entropy = f_entropy;
ctx->p_entropy = p_entropy;
ctx->reseed_interval = POLARSSL_HMAC_DRBG_RESEED_INTERVAL;
/*
* See SP800-57 5.6.1 (p. 65-66) for the security strength provided by
* each hash function, then according to SP800-90A rev1 10.1 table 2,
* min_entropy_len (in bits) is security_strength.
*
* (This also matches the sizes used in the NIST test vectors.)
*/
entropy_len = md_info->size <= 20 ? 16 : /* 160-bits hash -> 128 bits */
md_info->size <= 28 ? 24 : /* 224-bits hash -> 192 bits */
32; /* better (256+) -> 256 bits */
/*
* For initialisation, use more entropy to emulate a nonce
* (Again, matches test vectors.)
*/
ctx->entropy_len = entropy_len * 3 / 2;
if( ( ret = hmac_drbg_reseed( ctx, custom, len ) ) != 0 )
return( ret );
ctx->entropy_len = entropy_len;
return( 0 );
}
/*
* Set prediction resistance
*/
void hmac_drbg_set_prediction_resistance( hmac_drbg_context *ctx,
int resistance )
{
ctx->prediction_resistance = resistance;
}
/*
* Set entropy length grabbed for reseeds
*/
void hmac_drbg_set_entropy_len( hmac_drbg_context *ctx, size_t len )
{
ctx->entropy_len = len;
}
/*
* Set reseed interval
*/
void hmac_drbg_set_reseed_interval( hmac_drbg_context *ctx, int interval )
{
ctx->reseed_interval = interval;
}
/*
* HMAC_DRBG random function with optional additional data:
* 10.1.2.5 (arabic) + 9.3 (Roman)
*/
int hmac_drbg_random_with_add( void *p_rng,
unsigned char *output, size_t out_len,
const unsigned char *additional, size_t add_len )
{
int ret;
hmac_drbg_context *ctx = (hmac_drbg_context *) p_rng;
size_t md_len = md_get_size( ctx->md_ctx.md_info );
size_t left = out_len;
unsigned char *out = output;
/* II. Check request length */
if( out_len > POLARSSL_HMAC_DRBG_MAX_REQUEST )
return( POLARSSL_ERR_HMAC_DRBG_REQUEST_TOO_BIG );
/* III. Check input length */
if( add_len > POLARSSL_HMAC_DRBG_MAX_INPUT )
return( POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG );
/* 1. (aka VII and IX) Check reseed counter and PR */
if( ctx->f_entropy != NULL && /* For no-reseeding instances */
( ctx->prediction_resistance == POLARSSL_HMAC_DRBG_PR_ON ||
ctx->reseed_counter > ctx->reseed_interval ) )
{
if( ( ret = hmac_drbg_reseed( ctx, additional, add_len ) ) != 0 )
return( ret );
add_len = 0; /* VII.4 */
}
/* 2. Use additional data if any */
if( additional != NULL && add_len != 0 )
hmac_drbg_update( ctx, additional, add_len );
/* 3, 4, 5. Generate bytes */
while( left != 0 )
{
size_t use_len = left > md_len ? md_len : left;
md_hmac_reset( &ctx->md_ctx );
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;
}
/* 6. Update */
hmac_drbg_update( ctx, additional, add_len );
/* 7. Update reseed counter */
ctx->reseed_counter++;
/* 8. Done */
return( 0 );
}
/*
* HMAC_DRBG random function
*/
int hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len )
{
return( hmac_drbg_random_with_add( p_rng, output, out_len, NULL, 0 ) );
}
/*
* Free an HMAC_DRBG context
*/
void hmac_drbg_free( hmac_drbg_context *ctx )
{
if( ctx == NULL )
return;
md_free_ctx( &ctx->md_ctx );
polarssl_zeroize( ctx, sizeof( hmac_drbg_context ) );
}
#if defined(POLARSSL_FS_IO)
int hmac_drbg_write_seed_file( hmac_drbg_context *ctx, const char *path )
{
int ret;
FILE *f;
unsigned char buf[ POLARSSL_HMAC_DRBG_MAX_INPUT ];
if( ( f = fopen( path, "wb" ) ) == NULL )
return( POLARSSL_ERR_HMAC_DRBG_FILE_IO_ERROR );
if( ( ret = hmac_drbg_random( ctx, buf, sizeof( buf ) ) ) != 0 )
goto exit;
if( fwrite( buf, 1, sizeof( buf ), f ) != sizeof( buf ) )
{
ret = POLARSSL_ERR_HMAC_DRBG_FILE_IO_ERROR;
goto exit;
}
ret = 0;
exit:
fclose( f );
return( ret );
}
int hmac_drbg_update_seed_file( hmac_drbg_context *ctx, const char *path )
{
FILE *f;
size_t n;
unsigned char buf[ POLARSSL_HMAC_DRBG_MAX_INPUT ];
if( ( f = fopen( path, "rb" ) ) == NULL )
return( POLARSSL_ERR_HMAC_DRBG_FILE_IO_ERROR );
fseek( f, 0, SEEK_END );
n = (size_t) ftell( f );
fseek( f, 0, SEEK_SET );
if( n > POLARSSL_HMAC_DRBG_MAX_INPUT )
{
fclose( f );
return( POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG );
}
if( fread( buf, 1, n, f ) != n )
{
fclose( f );
return( POLARSSL_ERR_HMAC_DRBG_FILE_IO_ERROR );
}
fclose( f );
hmac_drbg_update( ctx, buf, n );
return( hmac_drbg_write_seed_file( ctx, path ) );
}
#endif /* POLARSSL_FS_IO */
#if defined(POLARSSL_SELF_TEST)
#include <stdio.h>
#if !defined(POLARSSL_SHA1_C)
/* Dummy checkup routine */
int hmac_drbg_self_test( int verbose )
{
if( verbose != 0 )
polarssl_printf( "\n" );
return( 0 );
}
#else
#define OUTPUT_LEN 80
/* From a NIST PR=true test vector */
static unsigned char entropy_pr[] = {
0xa0, 0xc9, 0xab, 0x58, 0xf1, 0xe2, 0xe5, 0xa4, 0xde, 0x3e, 0xbd, 0x4f,
0xf7, 0x3e, 0x9c, 0x5b, 0x64, 0xef, 0xd8, 0xca, 0x02, 0x8c, 0xf8, 0x11,
0x48, 0xa5, 0x84, 0xfe, 0x69, 0xab, 0x5a, 0xee, 0x42, 0xaa, 0x4d, 0x42,
0x17, 0x60, 0x99, 0xd4, 0x5e, 0x13, 0x97, 0xdc, 0x40, 0x4d, 0x86, 0xa3,
0x7b, 0xf5, 0x59, 0x54, 0x75, 0x69, 0x51, 0xe4 };
static const unsigned char result_pr[OUTPUT_LEN] = {
0x9a, 0x00, 0xa2, 0xd0, 0x0e, 0xd5, 0x9b, 0xfe, 0x31, 0xec, 0xb1, 0x39,
0x9b, 0x60, 0x81, 0x48, 0xd1, 0x96, 0x9d, 0x25, 0x0d, 0x3c, 0x1e, 0x94,
0x10, 0x10, 0x98, 0x12, 0x93, 0x25, 0xca, 0xb8, 0xfc, 0xcc, 0x2d, 0x54,
0x73, 0x19, 0x70, 0xc0, 0x10, 0x7a, 0xa4, 0x89, 0x25, 0x19, 0x95, 0x5e,
0x4b, 0xc6, 0x00, 0x1d, 0x7f, 0x4e, 0x6a, 0x2b, 0xf8, 0xa3, 0x01, 0xab,
0x46, 0x05, 0x5c, 0x09, 0xa6, 0x71, 0x88, 0xf1, 0xa7, 0x40, 0xee, 0xf3,
0xe1, 0x5c, 0x02, 0x9b, 0x44, 0xaf, 0x03, 0x44 };
/* From a NIST PR=false test vector */
static unsigned char entropy_nopr[] = {
0x79, 0x34, 0x9b, 0xbf, 0x7c, 0xdd, 0xa5, 0x79, 0x95, 0x57, 0x86, 0x66,
0x21, 0xc9, 0x13, 0x83, 0x11, 0x46, 0x73, 0x3a, 0xbf, 0x8c, 0x35, 0xc8,
0xc7, 0x21, 0x5b, 0x5b, 0x96, 0xc4, 0x8e, 0x9b, 0x33, 0x8c, 0x74, 0xe3,
0xe9, 0x9d, 0xfe, 0xdf };
static const unsigned char result_nopr[OUTPUT_LEN] = {
0xc6, 0xa1, 0x6a, 0xb8, 0xd4, 0x20, 0x70, 0x6f, 0x0f, 0x34, 0xab, 0x7f,
0xec, 0x5a, 0xdc, 0xa9, 0xd8, 0xca, 0x3a, 0x13, 0x3e, 0x15, 0x9c, 0xa6,
0xac, 0x43, 0xc6, 0xf8, 0xa2, 0xbe, 0x22, 0x83, 0x4a, 0x4c, 0x0a, 0x0a,
0xff, 0xb1, 0x0d, 0x71, 0x94, 0xf1, 0xc1, 0xa5, 0xcf, 0x73, 0x22, 0xec,
0x1a, 0xe0, 0x96, 0x4e, 0xd4, 0xbf, 0x12, 0x27, 0x46, 0xe0, 0x87, 0xfd,
0xb5, 0xb3, 0xe9, 0x1b, 0x34, 0x93, 0xd5, 0xbb, 0x98, 0xfa, 0xed, 0x49,
0xe8, 0x5f, 0x13, 0x0f, 0xc8, 0xa4, 0x59, 0xb7 };
/* "Entropy" from buffer */
static size_t test_offset;
static int hmac_drbg_self_test_entropy( void *data,
unsigned char *buf, size_t len )
{
const unsigned char *p = data;
memcpy( buf, p + test_offset, len );
test_offset += len;
return( 0 );
}
#define CHK( c ) if( (c) != 0 ) \
{ \
if( verbose != 0 ) \
polarssl_printf( "failed\n" ); \
return( 1 ); \
}
/*
* Checkup routine for HMAC_DRBG with SHA-1
*/
int hmac_drbg_self_test( int verbose )
{
hmac_drbg_context ctx;
unsigned char buf[OUTPUT_LEN];
const md_info_t *md_info = md_info_from_type( POLARSSL_MD_SHA1 );
/*
* PR = True
*/
if( verbose != 0 )
polarssl_printf( " HMAC_DRBG (PR = True) : " );
test_offset = 0;
CHK( hmac_drbg_init( &ctx, md_info,
hmac_drbg_self_test_entropy, entropy_pr,
NULL, 0 ) );
hmac_drbg_set_prediction_resistance( &ctx, POLARSSL_HMAC_DRBG_PR_ON );
CHK( hmac_drbg_random( &ctx, buf, OUTPUT_LEN ) );
CHK( hmac_drbg_random( &ctx, buf, OUTPUT_LEN ) );
CHK( memcmp( buf, result_pr, OUTPUT_LEN ) );
hmac_drbg_free( &ctx );
if( verbose != 0 )
polarssl_printf( "passed\n" );
/*
* PR = False
*/
if( verbose != 0 )
polarssl_printf( " HMAC_DRBG (PR = False) : " );
test_offset = 0;
CHK( hmac_drbg_init( &ctx, md_info,
hmac_drbg_self_test_entropy, entropy_nopr,
NULL, 0 ) );
CHK( hmac_drbg_reseed( &ctx, NULL, 0 ) );
CHK( hmac_drbg_random( &ctx, buf, OUTPUT_LEN ) );
CHK( hmac_drbg_random( &ctx, buf, OUTPUT_LEN ) );
CHK( memcmp( buf, result_nopr, OUTPUT_LEN ) );
hmac_drbg_free( &ctx );
if( verbose != 0 )
polarssl_printf( "passed\n" );
if( verbose != 0 )
polarssl_printf( "\n" );
return( 0 );
}
#endif /* POLARSSL_SHA1_C */
#endif /* POLARSSL_SELF_TEST */
#endif /* POLARSSL_HMAC_DRBG_C */
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