From 0d73de5ee0ec65ff8b60d073b7d1d369ee0a00e6 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Manuel=20P=C3=A9gouri=C3=A9-Gonnard?= Date: Thu, 10 Jul 2025 22:59:39 +0200 Subject: [PATCH] ecdsa: use CT modinv MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Signed-off-by: Manuel Pégourié-Gonnard --- library/ecdsa.c | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-) diff --git a/library/ecdsa.c b/library/ecdsa.c index 2f7a996a7e..0d73c65425 100644 --- a/library/ecdsa.c +++ b/library/ecdsa.c @@ -17,6 +17,7 @@ #include "mbedtls/ecdsa.h" #include "mbedtls/asn1write.h" +#include "bignum_internal.h" #include @@ -340,21 +341,11 @@ modn: MBEDTLS_MPI_CHK(derive_mpi(grp, &e, buf, blen)); /* - * Generate a random value to blind inv_mod in next step, - * avoiding a potential timing leak. - */ - MBEDTLS_MPI_CHK(mbedtls_ecp_gen_privkey(grp, &t, f_rng_blind, - p_rng_blind)); - - /* - * Step 6: compute s = (e + r * d) / k = t (e + rd) / (kt) mod n + * Step 6: compute s = (e + r * d) / k */ MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(s, pr, d)); MBEDTLS_MPI_CHK(mbedtls_mpi_add_mpi(&e, &e, s)); - MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&e, &e, &t)); - MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(pk, pk, &t)); - MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(pk, pk, &grp->N)); - MBEDTLS_MPI_CHK(mbedtls_mpi_inv_mod(s, pk, &grp->N)); + MBEDTLS_MPI_CHK(mbedtls_mpi_gcd_modinv_odd(NULL, s, pk, &grp->N)); MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(s, s, &e)); MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(s, s, &grp->N)); } while (mbedtls_mpi_cmp_int(s, 0) == 0); @@ -540,7 +531,7 @@ int mbedtls_ecdsa_verify_restartable(mbedtls_ecp_group *grp, */ ECDSA_BUDGET(MBEDTLS_ECP_OPS_CHK + MBEDTLS_ECP_OPS_INV + 2); - MBEDTLS_MPI_CHK(mbedtls_mpi_inv_mod(&s_inv, s, &grp->N)); + MBEDTLS_MPI_CHK(mbedtls_mpi_gcd_modinv_odd(NULL, &s_inv, s, &grp->N)); MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(pu1, &e, &s_inv)); MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(pu1, pu1, &grp->N));