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Bignum core: break mbedtls_mpi_core_random out of mbedtls_mpi_random

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Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2022-09-21 15:46:04 +02:00
parent 4a8c5cdfbf
commit 78cf3bbf22
1 changed files with 17 additions and 8 deletions
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25
library/bignum.c
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@ -1978,11 +1978,20 @@ int mbedtls_mpi_random( mbedtls_mpi *X,
if( ret != 0 )
return( ret );
unsigned ge_lower = 1, lt_upper = 0;
size_t n_bits = mbedtls_mpi_bitlen( N );
size_t n_bytes = ( n_bits + 7 ) / 8;
return( mbedtls_mpi_core_random( X->p, min, N->p, X->n, f_rng, p_rng ) );
}
ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
int mbedtls_mpi_core_random( mbedtls_mpi_uint *X,
mbedtls_mpi_uint min,
const mbedtls_mpi_uint *N,
size_t limbs,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
unsigned ge_lower = 1, lt_upper = 0;
size_t n_bits = mbedtls_mpi_core_bitlen( N, limbs );
size_t n_bytes = ( n_bits + 7 ) / 8;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
/*
* When min == 0, each try has at worst a probability 1/2 of failing
@ -2013,10 +2022,10 @@ int mbedtls_mpi_random( mbedtls_mpi *X,
*/
do
{
MBEDTLS_MPI_CHK( mbedtls_mpi_core_fill_random( X->p, X->n,
MBEDTLS_MPI_CHK( mbedtls_mpi_core_fill_random( X, limbs,
n_bytes,
f_rng, p_rng ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( X, 8 * n_bytes - n_bits ) );
mbedtls_mpi_core_shift_r( X, limbs, 8 * n_bytes - n_bits );
if( --count == 0 )
{
@ -2024,8 +2033,8 @@ int mbedtls_mpi_random( mbedtls_mpi *X,
goto cleanup;
}
ge_lower = mbedtls_mpi_core_uint_le_mpi( min, X->p, X->n );
lt_upper = mbedtls_mpi_core_lt_ct( X->p, N->p, N->n );
ge_lower = mbedtls_mpi_core_uint_le_mpi( min, X, limbs );
lt_upper = mbedtls_mpi_core_lt_ct( X, N, limbs );
}
while( ge_lower == 0 || lt_upper == 0 );