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Add entropy callbacks to HMAC_DRBG

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Manuel Pégourié-Gonnard 2014-01-30 15:06:40 +01:00
parent 8208d167da
commit fe34a5fb83
3 changed files with 135 additions and 13 deletions
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66
include/polarssl/hmac_drbg.h
View File

@ -29,19 +29,40 @@
#include "md.h"
/*
* ! Same values as ctr_drbg.h !
*/
#define POLARSSL_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED -0x0034 /**< The entropy source failed. */
#define POLARSSL_ERR_HMAC_DRBG_REQUEST_TOO_BIG -0x0036 /**< Too many random requested in single call. */
#define POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG -0x0038 /**< Input too large (Entropy + additional). */
#define POLARSSL_ERR_HMAC_DRBG_FILE_IO_ERROR -0x003A /**< Read/write error in file. */
#define HMAC_DRBG_RESEED_INTERVAL 10000 /**< Interval before reseed is performed by default */
#define HMAC_DRBG_MAX_INPUT 256 /**< Maximum number of additional input bytes */
#define HMAC_DRBG_MAX_REQUEST 1024 /**< Maximum number of requested bytes per call */
#define HMAC_DRBG_MAX_SEED_INPUT 384 /**< Maximum size of (re)seed buffer */
#ifdef __cplusplus
extern "C" {
#endif
/*
* Simplified HMAC_DRBG context.
* No reseed counter, no prediction resistance flag.
/**
* HMAC_DRBG context.
* TODO: reseed counter, prediction resistance flag.
*/
typedef struct
{
md_context_t md_ctx;
unsigned char V[POLARSSL_MD_MAX_SIZE];
unsigned char K[POLARSSL_MD_MAX_SIZE];
size_t entropy_len; /*!< entropy bytes grabbed on each (re)seed */
/*
* Callbacks (Entropy)
*/
int (*f_entropy)(void *, unsigned char *, size_t);
void *p_entropy; /*!< context for the entropy function */
} hmac_drbg_context;
/**
@ -49,18 +70,47 @@ typedef struct
*
* \param ctx HMAC_DRBG context to be initialised
* \param md_info MD algorithm to use for HMAC_DRBG
* \param data Concatenation of entropy string and additional data
* \param data_len Length of data in bytes
* \param f_entropy Entropy callback (p_entropy, buffer to fill, buffer
* length)
* \param p_entropy Entropy context
* \param custom Personalization data (Device specific identifiers)
* (Can be NULL)
* \param len Length of personalization data
*
* \todo Use entropy callback rather than buffer.
* \note The "security strength" as defined by NIST is set to:
* 128 bits if md_alg is SHA-1,
* 192 bits if md_alg is SHA-224,
* 256 bits if md_alg is SHA-256 or higher.
* Note that SHA-256 is just as efficient as SHA-224.
*
* \return 0 if successful, or
* POLARSSL_ERR_MD_BAD_INPUT_DATA, or
* POLARSSL_ERR_MD_ALLOC_FAILED
* POLARSSL_ERR_MD_ALLOC_FAILED, or
* POLARSSL_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED.
*/
int hmac_drbg_init( hmac_drbg_context *ctx,
const md_info_t * md_info,
const unsigned char *data, size_t data_len );
int (*f_entropy)(void *, unsigned char *, size_t),
void *p_entropy,
const unsigned char *custom,
size_t len );
/**
* \brief Simplified HMAC_DRBG initialisation.
* (For use with deterministic ECDSA.)
*
* \param ctx HMAC_DRBG context to be initialised
* \param md_info MD algorithm to use for HMAC_DRBG
* \param data Concatenation of entropy string and additional data
* \param data_len Length of data in bytes
*
* \return 0 if successful, or
* POLARSSL_ERR_MD_BAD_INPUT_DATA, or
* POLARSSL_ERR_MD_ALLOC_FAILED.
*/
int hmac_drbg_init_buf( hmac_drbg_context *ctx,
const md_info_t * md_info,
const unsigned char *data, size_t data_len );
/**
* \brief HMAC_DRBG update state

2
library/ecdsa.c
View File

@ -193,7 +193,7 @@ int ecdsa_sign_det( ecp_group *grp, mpi *r, mpi *s,
MPI_CHK( mpi_write_binary( d, data, grp_len ) );
MPI_CHK( derive_mpi( grp, &h, buf, blen ) );
MPI_CHK( mpi_write_binary( &h, data + grp_len, grp_len ) );
hmac_drbg_init( &rng_ctx, md_info, data, 2 * grp_len );
hmac_drbg_init_buf( &rng_ctx, md_info, data, 2 * grp_len );
ret = ecdsa_sign( grp, r, s, d, buf, blen,
hmac_drbg_random, &rng_ctx );

80
library/hmac_drbg.c
View File

@ -63,11 +63,11 @@ void hmac_drbg_update( hmac_drbg_context *ctx,
}
/*
* Simplified HMAC_DRBG initialisation.
* Simplified HMAC_DRBG initialisation (for use with deterministic ECDSA)
*/
int hmac_drbg_init( hmac_drbg_context *ctx,
const md_info_t * md_info,
const unsigned char *data, size_t data_len )
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;
@ -84,6 +84,78 @@ int hmac_drbg_init( hmac_drbg_context *ctx,
return( 0 );
}
/*
* HMAC_DRBG initialisation
*/
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;
unsigned char seed[HMAC_DRBG_MAX_SEED_INPUT];
size_t seedlen, init_entropy_len;
memset( ctx, 0, sizeof( hmac_drbg_context ) );
if( ( ret = md_init_ctx( &ctx->md_ctx, md_info ) ) != 0 )
return( ret );
/*
* 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.
*/
ctx->entropy_len = md_info->size <= 20 ? 16 : /* 160-bits hash -> 128 */
md_info->size <= 28 ? 24 : /* 224-bits hash -> 192 */
32; /* better (256+) -> 256 */
ctx->f_entropy = f_entropy;
ctx->p_entropy = p_entropy;
/*
* For initialisation, use more entropy to emulate a nonce
*/
init_entropy_len = ctx->entropy_len * 3 / 2;
if( init_entropy_len + len > HMAC_DRBG_MAX_SEED_INPUT )
return( POLARSSL_ERR_HMAC_DRBG_INPUT_TOO_BIG );
memset( seed, 0, HMAC_DRBG_MAX_SEED_INPUT );
/*
* Gather init_entropy_len bytes of entropy for initial seed
*/
if( 0 != ctx->f_entropy( ctx->p_entropy, seed,
init_entropy_len ) )
{
return( POLARSSL_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED );
}
seedlen = init_entropy_len;
/*
* Add additional data
*/
if( custom != NULL && len != 0 )
{
memcpy( seed + seedlen, custom, len );
seedlen += len;
}
/*
* Set initial state and update it with initialisation data
*/
memset( ctx->V, 0x01, md_info->size );
/* ctx->K is already 0 */
hmac_drbg_update( ctx, seed, seedlen );
return( 0 );
}
/*
* HMAC_DRBG random function with optional additional data (10.1.2.5)
*/