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Little HMAC_DRBG refactoring

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Manuel Pégourié-Gonnard 2014-01-06 15:05:01 +01:00
parent 4daaef7e27
commit f42bca6da0
1 changed files with 35 additions and 51 deletions
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86
library/ecdsa.c
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@ -48,53 +48,49 @@ typedef struct
unsigned char K[POLARSSL_MD_MAX_SIZE];
} hmac_drbg_context;
/*
* Simplified HMAC_DRBG update, using optional additional data
*/
static void hmac_drbg_update( hmac_drbg_context *ctx,
const unsigned char *data, size_t data_len )
{
size_t md_len = ctx->md_ctx.md_info->size;
unsigned char rounds = ( data != NULL && data_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, data, data_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.
*
* Uses an entropy buffer rather than callback,
* assumes personalisation is not null,
* assume personalisation string is included in entropy buffer,
* assumes md_info is not NULL and valid.
*/
static void hmac_drbg_init( hmac_drbg_context *ctx,
const md_info_t * md_info,
const unsigned char *entropy, size_t entropy_len,
const unsigned char *pers, size_t pers_len )
const unsigned char *data, size_t data_len )
{
unsigned char sep[1];
size_t md_len = md_info->size;
memset( ctx, 0, sizeof( hmac_drbg_context ) );
md_init_ctx( &ctx->md_ctx, md_info );
memset( ctx->V, 0x01, md_len );
memset( ctx->V, 0x01, md_info->size );
/* ctx->K is already 0 */
sep[0] = 0x00;
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 );
md_hmac_update( &ctx->md_ctx, entropy, entropy_len );
md_hmac_update( &ctx->md_ctx, pers, pers_len );
md_hmac_finish( &ctx->md_ctx, ctx->K );
/* Step e */
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 );
/* Step f */
sep[0] = 0x01;
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 );
md_hmac_update( &ctx->md_ctx, entropy, entropy_len );
md_hmac_update( &ctx->md_ctx, pers, pers_len );
md_hmac_finish( &ctx->md_ctx, ctx->K );
/* Step g */
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 );
hmac_drbg_update( ctx, data, data_len );
}
/*
@ -104,7 +100,6 @@ static int hmac_drbg_random( void *state,
unsigned char *output, size_t out_len )
{
hmac_drbg_context *ctx = (hmac_drbg_context *) state;
unsigned char sep[1] = { 0 };
size_t md_len = ctx->md_ctx.md_info->size;
size_t left = out_len;
unsigned char *out = output;
@ -122,14 +117,7 @@ static int hmac_drbg_random( void *state,
left -= use_len;
}
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 );
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 );
hmac_drbg_update( ctx, NULL, 0 );
return( 0 );
}
@ -249,8 +237,7 @@ int ecdsa_sign_det( ecp_group *grp, mpi *r, mpi *s,
{
int ret;
hmac_drbg_context rng_ctx;
unsigned char key[POLARSSL_ECP_MAX_BYTES];
unsigned char hash[POLARSSL_ECP_MAX_BYTES];
unsigned char data[2 * POLARSSL_ECP_MAX_BYTES];
size_t grp_len = ( grp->nbits + 7 ) / 8;
const md_info_t *md_info;
mpi h;
@ -261,15 +248,12 @@ int ecdsa_sign_det( ecp_group *grp, mpi *r, mpi *s,
mpi_init( &h );
memset( &rng_ctx, 0, sizeof( hmac_drbg_context ) );
/* Export private key as entropy source */
MPI_CHK( mpi_write_binary( d, key, grp_len ) );
/* Export message hash as additional data; need to reduce it first */
/* Use private key and message hash (reduced) to initialize HMAC_DRBG */
MPI_CHK( mpi_write_binary( d, data, grp_len ) );
MPI_CHK( derive_mpi( grp, &h, buf, blen ) );
MPI_CHK( mpi_write_binary( &h, hash, grp_len ) );
MPI_CHK( mpi_write_binary( &h, data + grp_len, grp_len ) );
hmac_drbg_init( &rng_ctx, md_info, data, 2 * grp_len );
/* Initialize HMAC_DRBG and use it for signature */
hmac_drbg_init( &rng_ctx, md_info, key, grp_len, hash, grp_len );
ret = ecdsa_sign( grp, r, s, d, buf, blen,
hmac_drbg_random, &rng_ctx );