Commit e0935a04 authored by Niels Möller's avatar Niels Möller

New function rsa_compute_root_tr.

parent cbfdd27c
2015-09-14 Niels Möller <nisse@lysator.liu.se>
* rsa-sign-tr.c (rsa_compute_root_tr): New file and function.
* rsa.h: Declare it.
* rsa-pkcs1-sign-tr.c (rsa_pkcs1_sign_tr): Use rsa_compute_root_tr.
(rsa_verify_res): Deleted, replaced by rsa_compute_root_tr.
* testsuite/rsa-sign-tr-test.c (test_rsa_sign_tr): Check that
signature argument is unchanged on failure.
* Makefile.in (hogweed_SOURCES): Added rsa-sign-tr.c.
2015-09-07 Niels Möller <nisse@lysator.liu.se>
* testsuite/rsa-sign-tr-test.c: Drop include of nettle-internal.h.
......
......@@ -144,7 +144,7 @@ hogweed_SOURCES = sexp.c sexp-format.c \
pkcs1.c pkcs1-encrypt.c pkcs1-decrypt.c \
pkcs1-rsa-digest.c pkcs1-rsa-md5.c pkcs1-rsa-sha1.c \
pkcs1-rsa-sha256.c pkcs1-rsa-sha512.c \
rsa.c rsa-sign.c rsa-verify.c \
rsa.c rsa-sign.c rsa-sign-tr.c rsa-verify.c \
rsa-pkcs1-sign.c rsa-pkcs1-sign-tr.c rsa-pkcs1-verify.c \
rsa-md5-sign.c rsa-md5-verify.c \
rsa-sha1-sign.c rsa-sha1-verify.c \
......
......@@ -38,26 +38,6 @@
#include "pkcs1.h"
/* Checks for any errors done in the RSA computation. That avoids
* attacks which rely on faults on hardware, or even software MPI
* implementation. */
static int
rsa_verify_res(const struct rsa_public_key *pub,
mpz_t s, mpz_t m)
{
mpz_t t;
int res;
mpz_init(t);
mpz_powm(t, s, pub->e, pub->n);
res = !mpz_cmp(m, t);
mpz_clear(t);
return res;
}
/* Side-channel resistant version of rsa_pkcs1_sign() */
int
rsa_pkcs1_sign_tr(const struct rsa_public_key *pub,
......@@ -66,34 +46,14 @@ rsa_pkcs1_sign_tr(const struct rsa_public_key *pub,
size_t length, const uint8_t *digest_info,
mpz_t s)
{
mpz_t ri, m;
mpz_t m;
int ret;
mpz_init(m);
if (pkcs1_rsa_digest_encode (m, key->size, length, digest_info))
{
mpz_init (ri);
_rsa_blind (pub, random_ctx, random, m, ri);
rsa_compute_root(key, s, m);
if (rsa_verify_res(pub, s, m) == 0)
{
mpz_set_ui(s, 0);
ret = 0;
}
else
ret = 1;
_rsa_unblind (pub, s, ri);
mpz_clear (ri);
}
else
{
mpz_set_ui(s, 0);
ret = 0;
}
ret = (pkcs1_rsa_digest_encode (m, key->size, length, digest_info)
&& rsa_compute_root_tr (pub, key, random_ctx, random,
s, m));
mpz_clear(m);
return ret;
}
/* rsa-sign-tr.c
Creating RSA signatures, with some additional checks.
Copyright (C) 2001, 2015 Niels Möller
Copyright (C) 2012 Nikos Mavrogiannopoulos
This file is part of GNU Nettle.
GNU Nettle is free software: you can redistribute it and/or
modify it under the terms of either:
* the GNU Lesser General Public License as published by the Free
Software Foundation; either version 3 of the License, or (at your
option) any later version.
or
* the GNU General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your
option) any later version.
or both in parallel, as here.
GNU Nettle is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received copies of the GNU General Public License and
the GNU Lesser General Public License along with this program. If
not, see http://www.gnu.org/licenses/.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include "rsa.h"
/* Blinds m, by computing c = m r^e (mod n), for a random r. Also
returns the inverse (ri), for use by rsa_unblind. */
static void
rsa_blind (const struct rsa_public_key *pub,
void *random_ctx, nettle_random_func *random,
mpz_t c, mpz_t ri, const mpz_t m)
{
mpz_t r;
mpz_init(r);
/* c = m*(r^e)
* ri = r^(-1)
*/
do
{
nettle_mpz_random(r, random_ctx, random, pub->n);
/* invert r */
}
while (!mpz_invert (ri, r, pub->n));
/* c = c*(r^e) mod n */
mpz_powm(r, r, pub->e, pub->n);
mpz_mul(c, m, r);
mpz_fdiv_r(c, c, pub->n);
mpz_clear(r);
}
/* m = c ri mod n */
static void
rsa_unblind (const struct rsa_public_key *pub,
mpz_t m, const mpz_t ri, const mpz_t c)
{
mpz_mul(m, c, ri);
mpz_fdiv_r(m, m, pub->n);
}
/* Checks for any errors done in the RSA computation. That avoids
* attacks which rely on faults on hardware, or even software MPI
* implementation. */
int
rsa_compute_root_tr(const struct rsa_public_key *pub,
const struct rsa_private_key *key,
void *random_ctx, nettle_random_func *random,
mpz_t x, const mpz_t m)
{
int res;
mpz_t t, mb, xb, ri;
mpz_init (mb);
mpz_init (xb);
mpz_init (ri);
mpz_init (t);
rsa_blind (pub, random_ctx, random, mb, ri, m);
rsa_compute_root (key, xb, mb);
mpz_powm(t, xb, pub->e, pub->n);
res = (mpz_cmp(mb, t) == 0);
if (res)
rsa_unblind (pub, x, ri, xb);
mpz_clear (mb);
mpz_clear (xb);
mpz_clear (ri);
mpz_clear (t);
return res;
}
......@@ -75,6 +75,7 @@ extern "C" {
#define rsa_decrypt nettle_rsa_decrypt
#define rsa_decrypt_tr nettle_rsa_decrypt_tr
#define rsa_compute_root nettle_rsa_compute_root
#define rsa_compute_root_tr nettle_rsa_compute_root_tr
#define rsa_generate_keypair nettle_rsa_generate_keypair
#define rsa_keypair_to_sexp nettle_rsa_keypair_to_sexp
#define rsa_keypair_from_sexp_alist nettle_rsa_keypair_from_sexp_alist
......@@ -315,6 +316,13 @@ void
rsa_compute_root(const struct rsa_private_key *key,
mpz_t x, const mpz_t m);
/* Safer variant, using RSA blinding, and checking the result after
CRT. */
int
rsa_compute_root_tr(const struct rsa_public_key *pub,
const struct rsa_private_key *key,
void *random_ctx, nettle_random_func *random,
mpz_t x, const mpz_t m);
/* Key generation */
......
......@@ -17,7 +17,7 @@ test_rsa_sign_tr(struct rsa_public_key *pub,
knuth_lfib_init(&lfib, 1111);
mpz_init(signature);
mpz_set_ui (signature, 17);
/* Try bad private key */
mpz_add_ui(key->p, key->p, 2);
......@@ -27,7 +27,7 @@ test_rsa_sign_tr(struct rsa_public_key *pub,
mpz_sub_ui(key->p, key->p, 2);
ASSERT(!mpz_cmp_ui(signature, 0));
ASSERT(!mpz_cmp_ui(signature, 17));
/* Try the good private key */
ASSERT(rsa_pkcs1_sign_tr(pub, key,
......
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