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Implement mbedtls_mpi_core_fill_random

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Turn mpi_fill_random_internal() into mbedtls_mpi_core_fill_random(). It
had basically the right code except for how X is passed to the function.

Write unit tests.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine
2022-09-09 20:55:53 +02:00
parent 909e03c52f
commit 5980f2bd36
3 changed files with 132 additions and 10 deletions
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23
library/bignum.c
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@ -1934,25 +1934,26 @@ cleanup:
/* Fill X with n_bytes random bytes.
* X must already have room for those bytes.
* The ordering of the bytes returned from the RNG is suitable for
* deterministic ECDSA (see RFC 6979 §3.3 and mbedtls_mpi_random()).
* deterministic ECDSA (see RFC 6979 §3.3 and mbedtls_mpi_core_random()).
* The size and sign of X are unchanged.
* n_bytes must not be 0.
*/
static int mpi_fill_random_internal(
mbedtls_mpi *X, size_t n_bytes,
int mbedtls_mpi_core_fill_random(
mbedtls_mpi_uint *X, size_t X_limbs,
size_t n_bytes,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
const size_t limbs = CHARS_TO_LIMBS( n_bytes );
const size_t overhead = ( limbs * ciL ) - n_bytes;
if( X->n < limbs )
if( X_limbs < limbs )
return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
memset( X->p, 0, overhead );
memset( (unsigned char *) X->p + limbs * ciL, 0, ( X->n - limbs ) * ciL );
MBEDTLS_MPI_CHK( f_rng( p_rng, (unsigned char *) X->p + overhead, n_bytes ) );
mbedtls_mpi_core_bigendian_to_host( X->p, limbs );
memset( X, 0, overhead );
memset( (unsigned char *) X + limbs * ciL, 0, ( X_limbs - limbs ) * ciL );
MBEDTLS_MPI_CHK( f_rng( p_rng, (unsigned char *) X + overhead, n_bytes ) );
mbedtls_mpi_core_bigendian_to_host( X, limbs );
cleanup:
return( ret );
@ -1980,7 +1981,7 @@ int mbedtls_mpi_fill_random( mbedtls_mpi *X, size_t size,
if( size == 0 )
return( 0 );
ret = mpi_fill_random_internal( X, size, f_rng, p_rng );
ret = mbedtls_mpi_core_fill_random( X->p, X->n, size, f_rng, p_rng );
cleanup:
return( ret );
@ -2042,7 +2043,9 @@ int mbedtls_mpi_random( mbedtls_mpi *X,
*/
do
{
MBEDTLS_MPI_CHK( mpi_fill_random_internal( X, n_bytes, f_rng, p_rng ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_core_fill_random( X->p, X->n,
n_bytes,
f_rng, p_rng ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( X, 8 * n_bytes - n_bits ) );
if( --count == 0 )