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Don't write to destination until we're done

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Manuel Pégourié-Gonnard 2017-03-14 12:11:21 +01:00
parent 78d564a841
commit 8962ddbb23
1 changed files with 15 additions and 3 deletions
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18
library/ecp.c
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@ -107,6 +107,7 @@ struct mbedtls_ecp_restart {
unsigned char fake_it; /* for tests: should we fake early return? */ unsigned char fake_it; /* for tests: should we fake early return? */
mbedtls_mpi m; /* saved argument: scalar */ mbedtls_mpi m; /* saved argument: scalar */
mbedtls_ecp_point P; /* saved argument: point */ mbedtls_ecp_point P; /* saved argument: point */
mbedtls_ecp_point R; /* current intermediate result */
}; };
/* /*
@ -127,6 +128,7 @@ static void ecp_restart_free( mbedtls_ecp_restart_ctx *ctx )
mbedtls_mpi_free( &ctx->m ); mbedtls_mpi_free( &ctx->m );
mbedtls_ecp_point_free( &ctx->P ); mbedtls_ecp_point_free( &ctx->P );
mbedtls_ecp_point_free( &ctx->R );
} }
#endif /* MBEDTLS_ECP_EARLY_RETURN */ #endif /* MBEDTLS_ECP_EARLY_RETURN */
@ -1456,14 +1458,24 @@ static int ecp_mul_comb_after_precomp( const mbedtls_ecp_group *grp,
int ret; int ret;
unsigned char parity_trick; unsigned char parity_trick;
unsigned char k[COMB_MAX_D + 1]; unsigned char k[COMB_MAX_D + 1];
mbedtls_ecp_point *RR = R;
#if defined(MBEDTLS_ECP_EARLY_RETURN)
if( grp->rs != NULL )
RR = &grp->rs->R;
#endif
MBEDTLS_MPI_CHK( ecp_comb_recode_scalar( grp, m, k, d, w, &parity_trick ) ); MBEDTLS_MPI_CHK( ecp_comb_recode_scalar( grp, m, k, d, w, &parity_trick ) );
MBEDTLS_MPI_CHK( ecp_mul_comb_core( grp, R, T, pre_len, k, d, f_rng, p_rng ) ); MBEDTLS_MPI_CHK( ecp_mul_comb_core( grp, RR, T, pre_len, k, d, f_rng, p_rng ) );
MBEDTLS_MPI_CHK( ecp_safe_invert_jac( grp, R, parity_trick ) ); MBEDTLS_MPI_CHK( ecp_safe_invert_jac( grp, RR, parity_trick ) );
MBEDTLS_MPI_CHK( ecp_normalize_jac( grp, R ) ); MBEDTLS_MPI_CHK( ecp_normalize_jac( grp, RR ) );
#if defined(MBEDTLS_ECP_EARLY_RETURN)
MBEDTLS_MPI_CHK( mbedtls_ecp_copy( R, RR ) );
#endif
cleanup: cleanup:
return( ret ); return( ret );