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Skip redundant checks for NULL f_rng

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Unless MBEDTLS_ECP_NO_INTERNAL_RNG is defined, it's no longer possible for
f_rng to be NULL at the places that randomize coordinates.

Eliminate the NULL check in this case:
- it makes it clearer to reviewers that randomization always happens (unless
  the user opted out at compile time)
- a NULL check in a place where it's easy to prove the value is never NULL
  might upset or confuse static analyzers (including humans)
- removing the check saves a bit of code size

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
This commit is contained in:
Manuel Pégourié-Gonnard 2020-06-19 10:36:16 +02:00
parent 6d059bf051
commit 22fe5236e9
1 changed files with 8 additions and 0 deletions
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8
library/ecp.c
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@ -1447,7 +1447,9 @@ static int ecp_mul_comb_core( const mbedtls_ecp_group *grp, mbedtls_ecp_point *R
i = d;
MBEDTLS_MPI_CHK( ecp_select_comb( grp, R, T, t_len, x[i] ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &R->Z, 1 ) );
#if defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
if( f_rng != 0 )
#endif
MBEDTLS_MPI_CHK( ecp_randomize_jac( grp, R, f_rng, p_rng ) );
while( i-- != 0 )
@ -1576,7 +1578,9 @@ static int ecp_mul_comb( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
*
* Avoid the leak by randomizing coordinates before we normalize them.
*/
#if defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
if( f_rng != 0 )
#endif
MBEDTLS_MPI_CHK( ecp_randomize_jac( grp, R, f_rng, p_rng ) );
MBEDTLS_MPI_CHK( ecp_normalize_jac( grp, R ) );
@ -1779,7 +1783,9 @@ static int ecp_mul_mxz( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
MOD_ADD( RP.X );
/* Randomize coordinates of the starting point */
#if defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
if( f_rng != NULL )
#endif
MBEDTLS_MPI_CHK( ecp_randomize_mxz( grp, &RP, f_rng, p_rng ) );
/* Loop invariant: R = result so far, RP = R + P */
@ -1812,7 +1818,9 @@ static int ecp_mul_mxz( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
*
* Avoid the leak by randomizing coordinates before we normalize them.
*/
#if defined(MBEDTLS_ECP_NO_INTERNAL_RNG)
if( f_rng != NULL )
#endif
MBEDTLS_MPI_CHK( ecp_randomize_mxz( grp, R, f_rng, p_rng ) );
MBEDTLS_MPI_CHK( ecp_normalize_mxz( grp, R ) );