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Move internal drbg init to specific mul functions

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While it seems cleaner and more convenient to set it in the top-level
mbedtls_ecp_mul() function, the existence of the restartable option changes
things - when it's enabled the drbg context needs to be saved in the restart
context (more precisely in the restart_mul sub-context), which can only be
done when it's allocated, which is in the curve-specific mul function.

This commit only internal drbg management from mbedtls_ecp_mul() to
ecp_mul_mxz() and ecp_mul_comb(), without modifying behaviour (even internal),
and a future commit will modify the ecp_mul_comb() version to handle restart
properly.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
This commit is contained in:
Manuel Pégourié-Gonnard 2020-06-03 12:11:56 +02:00
parent c52a43c2bd
commit f2a9fcff62
1 changed files with 37 additions and 22 deletions
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59
library/ecp.c
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@ -2221,11 +2221,25 @@ static int ecp_mul_comb( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char w, p_eq_g, i;
size_t d;
unsigned char T_size, T_ok;
mbedtls_ecp_point *T;
unsigned char T_size = 0, T_ok = 0;
mbedtls_ecp_point *T = NULL;
#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
ecp_drbg_context drbg_ctx;
ecp_drbg_init( &drbg_ctx );
#endif
ECP_RS_ENTER( rsm );
#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
if( f_rng == NULL )
{
MBEDTLS_MPI_CHK( ecp_drbg_seed( &drbg_ctx, m ) );
f_rng = &ecp_drbg_random;
p_rng = &drbg_ctx;
}
#endif /* !MBEDTLS_ECP_NO_INTERNAL_RNG */
/* Is P the base point ? */
#if MBEDTLS_ECP_FIXED_POINT_OPTIM == 1
p_eq_g = ( mbedtls_mpi_cmp_mpi( &P->Y, &grp->G.Y ) == 0 &&
@ -2297,6 +2311,10 @@ static int ecp_mul_comb( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
cleanup:
#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
ecp_drbg_free( &drbg_ctx );
#endif
/* does T belong to the group? */
if( T == grp->T )
T = NULL;
@ -2487,9 +2505,22 @@ static int ecp_mul_mxz( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
unsigned char b;
mbedtls_ecp_point RP;
mbedtls_mpi PX;
#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
ecp_drbg_context drbg_ctx;
ecp_drbg_init( &drbg_ctx );
#endif
mbedtls_ecp_point_init( &RP ); mbedtls_mpi_init( &PX );
#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
if( f_rng == NULL )
{
MBEDTLS_MPI_CHK( ecp_drbg_seed( &drbg_ctx, m ) );
f_rng = &ecp_drbg_random;
p_rng = &drbg_ctx;
}
#endif /* !MBEDTLS_ECP_NO_INTERNAL_RNG */
/* Save PX and read from P before writing to R, in case P == R */
MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &PX, &P->X ) );
MBEDTLS_MPI_CHK( mbedtls_ecp_copy( &RP, P ) );
@ -2542,6 +2573,10 @@ static int ecp_mul_mxz( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
MBEDTLS_MPI_CHK( ecp_normalize_mxz( grp, R ) );
cleanup:
#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
ecp_drbg_free( &drbg_ctx );
#endif
mbedtls_ecp_point_free( &RP ); mbedtls_mpi_free( &PX );
return( ret );
@ -2560,19 +2595,12 @@ int mbedtls_ecp_mul_restartable( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
int ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
#if defined(MBEDTLS_ECP_INTERNAL_ALT)
char is_grp_capable = 0;
#endif
#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
ecp_drbg_context drbg_ctx;
#endif
ECP_VALIDATE_RET( grp != NULL );
ECP_VALIDATE_RET( R != NULL );
ECP_VALIDATE_RET( m != NULL );
ECP_VALIDATE_RET( P != NULL );
#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
ecp_drbg_init( &drbg_ctx );
#endif /* !MBEDTLS_ECP_NO_INTERNAL_RNG */
#if defined(MBEDTLS_ECP_RESTARTABLE)
/* reset ops count for this call if top-level */
if( rs_ctx != NULL && rs_ctx->depth++ == 0 )
@ -2584,15 +2612,6 @@ int mbedtls_ecp_mul_restartable( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
MBEDTLS_MPI_CHK( mbedtls_internal_ecp_init( grp ) );
#endif /* MBEDTLS_ECP_INTERNAL_ALT */
#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
if( f_rng == NULL )
{
MBEDTLS_MPI_CHK( ecp_drbg_seed( &drbg_ctx, m ) );
f_rng = &ecp_drbg_random;
p_rng = &drbg_ctx;
}
#endif /* !MBEDTLS_ECP_NO_INTERNAL_RNG */
#if defined(MBEDTLS_ECP_RESTARTABLE)
/* skip argument check when restarting */
if( rs_ctx == NULL || rs_ctx->rsm == NULL )
@ -2623,10 +2642,6 @@ cleanup:
mbedtls_internal_ecp_free( grp );
#endif /* MBEDTLS_ECP_INTERNAL_ALT */
#if !defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
ecp_drbg_free( &drbg_ctx );
#endif
#if defined(MBEDTLS_ECP_RESTARTABLE)
if( rs_ctx != NULL )
rs_ctx->depth--;