yuzu/mbedtls
1
0
Fork 0
mirror of https://github.com/yuzu-emu/mbedtls.git synced 2024-10-18 22:01:10 +00:00
Code Issues Packages Projects Releases Wiki Activity

Restore retry in rsa_prepare_blinding()

Browse source 
Starting with commit 49e94e3, the do/while loop in
`rsa_prepare_blinding()` was changed to a `do...while(0)`, which
prevents retry from being effective and leaves dead code.

Restore the while condition to retry, and lift the calls to finish the
computation out of the while loop by by observing that they are
performed only when `mbedtls_mpi_inv_mod()` returns zero.

Signed-off-by: Peter Kolbus <peter.kolbus@garmin.com>
This commit is contained in:
Peter Kolbus 2020-09-24 11:11:50 -05:00
parent 523f0554b6
commit ca8b8e7c31
2 changed files with 12 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
ChangeLog.d/fix-rsa-blinding.txt Normal file
View file

@ -0,0 +1,6 @@
Bugfix
* Fix rsa_prepare_blinding() to retry when the blinding value is not
invertible (mod N), instead of returning MBEDTLS_ERR_RSA_RNG_FAILED. This
addresses a regression but is rare in practice (approx. 1 in 2/sqrt(N)).
Found by Synopsys Coverity, fix contributed by Peter Kolbus (Garmin).
Fixes #3647.

13
library/rsa.c
View file

@ -811,15 +811,14 @@ static int rsa_prepare_blinding( mbedtls_rsa_context *ctx,
* which one, we just loop and choose new values for both of them.
* (Each iteration succeeds with overwhelming probability.) */
ret = mbedtls_mpi_inv_mod( &ctx->Vi, &ctx->Vi, &ctx->N );
if( ret == MBEDTLS_ERR_MPI_NOT_ACCEPTABLE )
continue;
if( ret != 0 )
if( ret != 0 && ret != MBEDTLS_ERR_MPI_NOT_ACCEPTABLE )
goto cleanup;
/* Finish the computation of Vf^-1 = R * (R Vf)^-1 */
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &R ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->N ) );
} while( 0 );
} while( ret == MBEDTLS_ERR_MPI_NOT_ACCEPTABLE );
/* Finish the computation of Vf^-1 = R * (R Vf)^-1 */
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->Vi, &ctx->Vi, &R ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->Vi, &ctx->Vi, &ctx->N ) );
/* Blinding value: Vi = Vf^(-e) mod N
* (Vi already contains Vf^-1 at this point) */