/*

* HMAC_DRBG implementation (NIST SP 800-90)

*

* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved

* SPDX-License-Identifier: Apache-2.0

*

* Licensed under the Apache License, Version 2.0 (the "License"); you may

* not use this file except in compliance with the License.

* You may obtain a copy of the License at

*

* http://www.apache.org/licenses/LICENSE-2.0

*

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT

* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

*

* This file is part of mbed TLS (https://tls.mbed.org)

*/

/*

* 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(MBEDTLS_CONFIG_FILE)

// #include "mbedtls/config.h"

// #else

// #include MBEDTLS_CONFIG_FILE

// #endif

#include "hmac_drbg.h"

#include <string.h>

#if defined(MBEDTLS_SELF_TEST)

#include <stdio.h>

#define mbedtls_printf printf

#endif /* MBEDTLS_PLATFORM_C */

#include <stdlib.h>

#include "hmac.h"

struct mbedtls_md_info_t {

int dummy;

};

static const mbedtls_md_info_t mocked_sha256_info;

const mbedtls_md_info_t *mbedtls_md_info_from_string( const char *md_name ) {

return &mocked_sha256_info;

}

const mbedtls_md_info_t *mbedtls_md_info_from_type( mbedtls_md_type_t md_type ) {

return &mocked_sha256_info;

}

unsigned char mbedtls_md_get_size( const mbedtls_md_info_t *md_info ) {

return SHA256_DIGEST_LENGTH;

}

void test_md_get_size() {

mbedtls_md_info_t info;

unsigned char ret;

ret = mbedtls_md_get_size(&info);

}

int mbedtls_md_setup( mbedtls_md_context_t *ctx, const mbedtls_md_info_t *md_info, int hmac ) {

HMAC_CTX * sha_ctx = (HMAC_CTX *) malloc(sizeof(HMAC_CTX));

if (sha_ctx == NULL) {

return MBEDTLS_ERR_MD_ALLOC_FAILED;

}

ctx->hmac_ctx = sha_ctx;

return 0;

}

int mbedtls_md_hmac_starts( mbedtls_md_context_t *ctx, const unsigned char *key, size_t keylen ) {

HMAC_CTX * hmac_ctx = ctx->hmac_ctx;

HMAC_Init(hmac_ctx, (unsigned char*) key, keylen);

return 0;

}

int mbedtls_md_hmac_reset( mbedtls_md_context_t *ctx ) {

HMAC_CTX * hmac_ctx = ctx->hmac_ctx;

HMAC_Init(hmac_ctx, NULL, SHA256_DIGEST_LENGTH);

return 0;

}

int mbedtls_md_hmac_update( mbedtls_md_context_t *ctx, const unsigned char *input, size_t ilen ) {

HMAC_CTX * hmac_ctx = ctx->hmac_ctx;

HMAC_Update(hmac_ctx, (const void *) input, ilen);

return 0;

}

int mbedtls_md_hmac_finish( mbedtls_md_context_t *ctx, unsigned char *output) {

HMAC_CTX * hmac_ctx = ctx->hmac_ctx;

HMAC_Final(hmac_ctx, output);

return 0;

}

void mbedtls_md_free( mbedtls_md_context_t *ctx ) {

HMAC_CTX * hmac_ctx = ctx->hmac_ctx;

free(hmac_ctx);

}

/* dummy entropy function */

int get_entropy(unsigned char*, size_t);

/* Implementation that should never be optimized out by the compiler */

static void mbedtls_zeroize( void *v, size_t n ) {

volatile unsigned char *p = v; while( n-- ) *p++ = 0;

}

/*

* HMAC_DRBG context initialization

*/

void mbedtls_hmac_drbg_init( mbedtls_hmac_drbg_context *ctx )

{

memset( ctx, 0, sizeof( mbedtls_hmac_drbg_context ) );

#if defined(MBEDTLS_THREADING_C)

mbedtls_mutex_init( &ctx->mutex );

#endif

}

/*

* HMAC_DRBG update, using optional additional data (10.1.2.2)

*/

void mbedtls_hmac_drbg_update( mbedtls_hmac_drbg_context *ctx,

const unsigned char *additional, size_t add_len )

{

const mbedtls_md_info_t *info;

size_t md_len;

int /* unsigned char */ rounds;

unsigned char sep[1];

unsigned char K[MBEDTLS_MD_MAX_SIZE];

int sep_value;

info = ctx->md_ctx.md_info;

md_len = mbedtls_md_get_size( info );

rounds = ( add_len != 0 && additional != NULL ) ? 2 : 1;

/* rounds = ( additional != NULL && add_len != 0 ) ? 2 : 1; */

for( sep_value = 0; sep_value < rounds; sep_value++ )

{

sep[0] = sep_value;

/* Step 1 or 4 */

mbedtls_md_hmac_reset( &ctx->md_ctx );

mbedtls_md_hmac_update( &ctx->md_ctx, ctx->V, md_len );

mbedtls_md_hmac_update( &ctx->md_ctx, sep, 1 );

if( rounds == 2 )

mbedtls_md_hmac_update( &ctx->md_ctx, additional, add_len );

mbedtls_md_hmac_finish( &ctx->md_ctx, K );

/* Step 2 or 5 */

mbedtls_md_hmac_starts( &ctx->md_ctx, K, md_len );

mbedtls_md_hmac_update( &ctx->md_ctx, ctx->V, md_len );

mbedtls_md_hmac_finish( &ctx->md_ctx, ctx->V );

}

}

/*

* Simplified HMAC_DRBG initialisation (for use with deterministic ECDSA)

*/

int mbedtls_hmac_drbg_seed_buf( mbedtls_hmac_drbg_context *ctx,

const mbedtls_md_info_t * md_info,

const unsigned char *data, size_t data_len )

{

int ret;

if( ( ret = mbedtls_md_setup( &ctx->md_ctx, md_info, 1 ) ) != 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.

*/

mbedtls_md_hmac_starts( &ctx->md_ctx, ctx->V, mbedtls_md_get_size( md_info ) );

memset( ctx->V, 0x01, mbedtls_md_get_size( md_info ) );

mbedtls_hmac_drbg_update( ctx, data, data_len );

return( 0 );

}

/*

* HMAC_DRBG reseeding: 10.1.2.4 (arabic) + 9.2 (Roman)

*/

int mbedtls_hmac_drbg_reseed( mbedtls_hmac_drbg_context *ctx,

const unsigned char *additional, size_t len )

{

unsigned char seed[MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT];

size_t seedlen;

size_t entropy_len;

/* III. Check input length */

entropy_len = ctx->entropy_len;

if( len > MBEDTLS_HMAC_DRBG_MAX_INPUT ||

entropy_len + len > MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT )

//ctx->entropy_len + len > MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT )

{

return( MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG );

}

memset( seed, 0, MBEDTLS_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 )

if( get_entropy(seed, entropy_len ) != 0 )

return( MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED );

seedlen = 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 */

mbedtls_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 mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx,

size_t len )

{

int ret;

size_t entropy_len, md_size;

if( ( ret = mbedtls_md_setup( &ctx->md_ctx, md_info, 1 ) ) != 0 )

return( ret );

md_size = mbedtls_md_get_size( md_info ); // TODO hardcode this, get rid of info

/*

* 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.

*/

mbedtls_md_hmac_starts( &ctx->md_ctx, ctx->V, md_size );

memset( ctx->V, 0x01, md_size );

// ctx->f_entropy = f_entropy;

// ctx->p_entropy = p_entropy;

ctx->reseed_interval = MBEDTLS_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_size <= 20 ? 16 : /* 160-bits hash -> 128 bits */

md_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 = mbedtls_hmac_drbg_reseed( ctx, custom, len ) ) != 0 )

return( ret );

ctx->entropy_len = entropy_len;

return( 0 );

}

/*

* Set prediction resistance

*/

void mbedtls_hmac_drbg_set_prediction_resistance( mbedtls_hmac_drbg_context *ctx,

int resistance )

{

ctx->prediction_resistance = resistance;

}

/*

* Set entropy length grabbed for reseeds

*/

void mbedtls_hmac_drbg_set_entropy_len( mbedtls_hmac_drbg_context *ctx, size_t len )

{

ctx->entropy_len = len;

}

/*

* Set reseed interval

*/

void mbedtls_hmac_drbg_set_reseed_interval( mbedtls_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 mbedtls_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;

mbedtls_hmac_drbg_context *ctx = (mbedtls_hmac_drbg_context *) p_rng;

// size_t md_len = mbedtls_md_get_size( ctx->md_ctx.md_info );

size_t md_len;

size_t left = out_len;

unsigned char *out = output;

const mbedtls_md_info_t *info;

int prediction_resistance = ctx->prediction_resistance;

int reseed_counter = ctx->reseed_counter;

int reseed_interval = ctx->reseed_interval;

info = ctx->md_ctx.md_info;

md_len = mbedtls_md_get_size(info);

/* II. Check request length */

if( out_len > MBEDTLS_HMAC_DRBG_MAX_REQUEST )

return( MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG );

/* III. Check input length */

if( add_len > MBEDTLS_HMAC_DRBG_MAX_INPUT )

return( MBEDTLS_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 */

( prediction_resistance == MBEDTLS_HMAC_DRBG_PR_ON ||

reseed_counter > reseed_interval ) )

// ( ctx->prediction_resistance == MBEDTLS_HMAC_DRBG_PR_ON ||

// ctx->reseed_counter > ctx->reseed_interval ) )

{

if( ( ret = mbedtls_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 )

mbedtls_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;

mbedtls_md_hmac_reset( &ctx->md_ctx );

mbedtls_md_hmac_update( &ctx->md_ctx, ctx->V, md_len );

mbedtls_md_hmac_finish( &ctx->md_ctx, ctx->V );

memcpy( out, ctx->V, use_len );

out += use_len;

left -= use_len;

}

/* 6. Update */

mbedtls_hmac_drbg_update( ctx, additional, add_len );

/* 7. Update reseed counter */

reseed_counter = ctx->reseed_counter;

ctx->reseed_counter = reseed_counter + 1;

// ctx->reseed_counter++;

/* 8. Done */

return( 0 );

}

/*

* HMAC_DRBG random function

*/

int mbedtls_hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len )

{

int ret;

mbedtls_hmac_drbg_context *ctx = (mbedtls_hmac_drbg_context *) p_rng;

#if defined(MBEDTLS_THREADING_C)

if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )

return( ret );

#endif

ret = mbedtls_hmac_drbg_random_with_add( ctx, output, out_len, NULL, 0 );

#if defined(MBEDTLS_THREADING_C)

if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )

return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );

#endif

return( ret );

}

/*

* Free an HMAC_DRBG context

*/

void mbedtls_hmac_drbg_free( mbedtls_hmac_drbg_context *ctx )

{

if( ctx == NULL )

return;

#if defined(MBEDTLS_THREADING_C)

mbedtls_mutex_free( &ctx->mutex );

#endif

mbedtls_md_free( &ctx->md_ctx );

mbedtls_zeroize( ctx, sizeof( mbedtls_hmac_drbg_context ) );

}

#if defined(MBEDTLS_SELF_TEST)

#define OUTPUT_LEN 80

/* From a NIST PR=true test vector */

static const 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 const 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 ) \

mbedtls_printf( "failed\n" ); \

return( 1 ); \

}

#include <assert.h>

/*

* Checkup routine for HMAC_DRBG with SHA-1

*/

int mbedtls_hmac_drbg_self_test( int verbose )

{

mbedtls_hmac_drbg_context ctx;

unsigned char buf[OUTPUT_LEN];

const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type( MBEDTLS_MD_SHA1 );

mbedtls_hmac_drbg_init( &ctx );

/*

* PR = True

*/

if( verbose != 0 )

mbedtls_printf( " HMAC_DRBG (PR = True) : " );

test_offset = 0;

CHK( mbedtls_hmac_drbg_seed( &ctx, md_info,

hmac_drbg_self_test_entropy, (void *) entropy_pr,

NULL, 0 ) );

mbedtls_hmac_drbg_set_prediction_resistance( &ctx, MBEDTLS_HMAC_DRBG_PR_ON );

CHK( mbedtls_hmac_drbg_random( &ctx, buf, OUTPUT_LEN ) );

CHK( mbedtls_hmac_drbg_random( &ctx, buf, OUTPUT_LEN ) );

CHK( memcmp( buf, result_pr, OUTPUT_LEN ) );

mbedtls_hmac_drbg_free( &ctx );

mbedtls_hmac_drbg_free( &ctx );

if( verbose != 0 )

mbedtls_printf( "passed\n" );

/*

* PR = False

*/

if( verbose != 0 )

mbedtls_printf( " HMAC_DRBG (PR = False) : " );

mbedtls_hmac_drbg_init( &ctx );

test_offset = 0;

CHK( mbedtls_hmac_drbg_seed( &ctx, md_info,

hmac_drbg_self_test_entropy, (void *) entropy_nopr,

NULL, 0 ) );

CHK( mbedtls_hmac_drbg_reseed( &ctx, NULL, 0 ) );

CHK( mbedtls_hmac_drbg_random( &ctx, buf, OUTPUT_LEN ) );

CHK( mbedtls_hmac_drbg_random( &ctx, buf, OUTPUT_LEN ) );

CHK( memcmp( buf, result_nopr, OUTPUT_LEN ) );

mbedtls_hmac_drbg_free( &ctx );

mbedtls_hmac_drbg_free( &ctx );

if( verbose != 0 )

mbedtls_printf( "passed\n" );

if( verbose != 0 )

mbedtls_printf( "\n" );

return( 0 );

}

#endif /* MBEDTLS_SELF_TEST */

int main()

{

#if defined(MBEDTLS_SELF_TEST)

return mbedtls_hmac_drbg_self_test(1);

#else

return 0;

#endif /* MBEDTLS_SELF_TEST */

}