contributed by Nikos Mavrogiannopoulos.
2012-04-09 Niels Möller <nisse@lysator.liu.se>
+ Timing resistant RSA decryption, based on RSA blinding code
+ contributed by Nikos Mavrogiannopoulos.
+ * rsa-decrypt-tr.c (rsa_decrypt_tr): New function.
+ (rsa_blind): Helper function.
+ (rsa_unblind): Helper function.
+ * rsa.h: Declare rsa_decrypt_tr. Some cleanups, no longer include
+ nettle-meta.h, more consistent declrations of function pointer
+ arguments.
+ * testsuite/rsa-encrypt-test.c (test_main): Test rsa_encrypt_tr.
+ Check for writes past the end of the message area.
+
* Makefile.in (hogweed_SOURCES): Added pkcs1-decrypt.c.
* rsa-decrypt.c (rsa_decrypt): Use pkcs1_decrypt.
* pkcs1-decrypt.c (pkcs1_decrypt): New file and function,
rsa-sha1-sign.c rsa-sha1-verify.c \
rsa-sha256-sign.c rsa-sha256-verify.c \
rsa-sha512-sign.c rsa-sha512-verify.c \
- rsa-encrypt.c rsa-decrypt.c \
+ rsa-encrypt.c rsa-decrypt.c rsa-decrypt-tr.c \
rsa-keygen.c rsa-compat.c \
rsa2sexp.c sexp2rsa.c \
dsa.c dsa-sign.c dsa-verify.c dsa-keygen.c \
--- /dev/null
+/* rsa-decrypt-tr.c
+ *
+ * RSA decryption, using randomized RSA blinding to be more resistant
+ * to timing attacks.
+ */
+
+/* nettle, low-level cryptographics library
+ *
+ * Copyright (C) 2001, 2012 Niels Möller, Nikos Mavrogiannopoulos
+ *
+ * The nettle library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ *
+ * The nettle library 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 Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the nettle library; see the file COPYING.LIB. If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+#if HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include "rsa.h"
+
+#include "bignum.h"
+#include "pkcs1.h"
+
+/* Blinds the c, by computing c *= 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)
+{
+ mpz_t r;
+
+ mpz_init(r);
+
+ /* c = c*(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, c, r);
+ mpz_fdiv_r(c, c, pub->n);
+
+ mpz_clear(r);
+}
+
+/* c *= ri mod n */
+static void
+rsa_unblind (const struct rsa_public_key *pub, mpz_t c, const mpz_t ri)
+{
+ mpz_mul(c, c, ri);
+ mpz_fdiv_r(c, c, pub->n);
+}
+
+int
+rsa_decrypt_tr(const struct rsa_public_key *pub,
+ const struct rsa_private_key *key,
+ void *random_ctx, nettle_random_func random,
+ unsigned *length, uint8_t *message,
+ const mpz_t gibberish)
+{
+ mpz_t m, ri;
+ int res;
+
+ mpz_init_set(m, gibberish);
+ mpz_init (ri);
+
+ rsa_blind (pub, random_ctx, random, m, ri);
+ rsa_compute_root(key, m, m);
+ rsa_unblind (pub, m, ri);
+
+ res = pkcs1_decrypt (key->size, m, length, message);
+ mpz_clear(m);
+ return res;
+}
#include "md5.h"
#include "sha.h"
-/* For nettle_random_func */
-#include "nettle-meta.h"
-
#ifdef __cplusplus
extern "C" {
#endif
#define rsa_sha512_verify_digest nettle_rsa_sha512_verify_digest
#define rsa_encrypt nettle_rsa_encrypt
#define rsa_decrypt nettle_rsa_decrypt
+#define rsa_decrypt_tr nettle_rsa_decrypt_tr
#define rsa_compute_root nettle_rsa_compute_root
#define rsa_generate_keypair nettle_rsa_generate_keypair
#define rsa_keypair_to_sexp nettle_rsa_keypair_to_sexp
int
rsa_encrypt(const struct rsa_public_key *key,
/* For padding */
- void *random_ctx, nettle_random_func random,
+ void *random_ctx, nettle_random_func *random,
unsigned length, const uint8_t *cleartext,
mpz_t cipher);
unsigned *length, uint8_t *cleartext,
const mpz_t ciphertext);
+/* Timing-resistant version, using randomized RSA blinding. */
+int
+rsa_decrypt_tr(const struct rsa_public_key *pub,
+ const struct rsa_private_key *key,
+ void *random_ctx, nettle_random_func *random,
+ unsigned *length, uint8_t *message,
+ const mpz_t gibberish);
+
/* Compute x, the e:th root of m. Calling it with x == m is allowed. */
void
rsa_compute_root(const struct rsa_private_key *key,
rsa_generate_keypair(struct rsa_public_key *pub,
struct rsa_private_key *key,
- void *random_ctx, nettle_random_func random,
- void *progress_ctx, nettle_progress_func progress,
+ void *random_ctx, nettle_random_func *random,
+ void *progress_ctx, nettle_progress_func *progress,
/* Desired size of modulo, in bits */
unsigned n_size,
uint8_t *decrypted;
unsigned decrypted_length;
-
+ uint8_t after;
+
mpz_t gibberish;
rsa_private_key_init(&key);
decrypted = xalloc(msg_length + 1);
+ knuth_lfib_random (&lfib, msg_length + 1, decrypted);
+ after = decrypted[msg_length];
+
decrypted_length = msg_length - 1;
ASSERT(!rsa_decrypt(&key, &decrypted_length, decrypted, gibberish));
ASSERT(rsa_decrypt(&key, &decrypted_length, decrypted, gibberish));
ASSERT(decrypted_length == msg_length);
ASSERT(MEMEQ(msg_length, msg, decrypted));
+ ASSERT(decrypted[msg_length] == after);
+
+ knuth_lfib_random (&lfib, msg_length + 1, decrypted);
+ after = decrypted[msg_length];
decrypted_length = key.size;
ASSERT(rsa_decrypt(&key, &decrypted_length, decrypted, gibberish));
ASSERT(decrypted_length == msg_length);
ASSERT(MEMEQ(msg_length, msg, decrypted));
+ ASSERT(decrypted[msg_length] == after);
+ knuth_lfib_random (&lfib, msg_length + 1, decrypted);
+ after = decrypted[msg_length];
+
+ decrypted_length = msg_length;
+ ASSERT(rsa_decrypt_tr(&pub, &key,
+ &lfib, (nettle_random_func *) knuth_lfib_random,
+ &decrypted_length, decrypted, gibberish));
+ ASSERT(decrypted_length == msg_length);
+ ASSERT(MEMEQ(msg_length, msg, decrypted));
+ ASSERT(decrypted[msg_length] == after);
+
rsa_private_key_clear(&key);
rsa_public_key_clear(&pub);
mpz_clear(gibberish);
projects / thirdparty / nettle.git / commitdiff
