/*
* 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 );
}
/*
* 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 left = out_len;
unsigned char *out = output;
/* 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 */
( 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 */
ctx->reseed_counter++;
/* 8. Done */
return( 0 );
}
/*
* HMAC_DRBG initialisation (10.1.2.3 + 9.1)
*/
int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx,
const mbedtls_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, md_size;
if( ( ret = mbedtls_md_setup( &ctx->md_ctx, md_info, 1 ) ) != 0 )
return( ret );
md_size = mbedtls_md_get_size( md_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.
*/
if( ( ret = mbedtls_md_hmac_starts( &ctx->md_ctx, ctx->V, md_size ) ) != 0 )
return( ret );
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 );
}
