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libnettle
libnettle-CVE-2021-3580-rsa_sec.patch
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File libnettle-CVE-2021-3580-rsa_sec.patch of Package libnettle
From 485b5e2820a057e873b1ba812fdb39cae4adf98c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se> Date: Mon, 17 May 2021 20:55:53 +0200 Subject: [PATCH] Change _rsa_sec_compute_root_tr to take a fix input size. Improves consistency with _rsa_sec_compute_root, and fixes zero-input bug. --- rsa-decrypt-tr.c | 7 ++--- rsa-internal.h | 4 +-- rsa-sec-decrypt.c | 9 ++++-- rsa-sign-tr.c | 61 +++++++++++++++++------------------- testsuite/rsa-encrypt-test.c | 14 ++++++++- 6 files changed, 68 insertions(+), 42 deletions(-) Index: nettle-3.4.1/rsa-decrypt-tr.c =================================================================== --- nettle-3.4.1.orig/rsa-decrypt-tr.c +++ nettle-3.4.1/rsa-decrypt-tr.c @@ -52,14 +52,13 @@ rsa_decrypt_tr(const struct rsa_public_k mp_size_t key_limb_size; int res; - key_limb_size = NETTLE_OCTET_SIZE_TO_LIMB_SIZE(key->size); + key_limb_size = mpz_size(pub->n); TMP_GMP_ALLOC (m, key_limb_size); TMP_GMP_ALLOC (em, key->size); + mpz_limbs_copy(m, gibberish, key_limb_size); - res = _rsa_sec_compute_root_tr (pub, key, random_ctx, random, m, - mpz_limbs_read(gibberish), - mpz_size(gibberish)); + res = _rsa_sec_compute_root_tr (pub, key, random_ctx, random, m, m); mpn_get_base256 (em, key->size, m, key_limb_size); Index: nettle-3.4.1/rsa-internal.h =================================================================== --- nettle-3.4.1.orig/rsa-internal.h +++ nettle-3.4.1/rsa-internal.h @@ -53,12 +53,12 @@ _rsa_sec_compute_root(const struct rsa_p mp_limb_t *scratch); /* Safe side-channel silent variant, using RSA blinding, and checking the - * result after CRT. */ + * result after CRT. In-place calls, with x == m, is allowed. */ int _rsa_sec_compute_root_tr(const struct rsa_public_key *pub, const struct rsa_private_key *key, void *random_ctx, nettle_random_func *random, - mp_limb_t *x, const mp_limb_t *m, size_t mn); + mp_limb_t *x, const mp_limb_t *m); /* additional resistance to memory access side-channel attacks. * Note: message buffer is returned unchanged on error */ Index: nettle-3.4.1/rsa-sec-decrypt.c =================================================================== --- nettle-3.4.1.orig/rsa-sec-decrypt.c +++ nettle-3.4.1/rsa-sec-decrypt.c @@ -57,9 +57,12 @@ rsa_sec_decrypt(const struct rsa_public_ TMP_GMP_ALLOC (m, mpz_size(pub->n)); TMP_GMP_ALLOC (em, key->size); - res = _rsa_sec_compute_root_tr (pub, key, random_ctx, random, m, - mpz_limbs_read(gibberish), - mpz_size(gibberish)); + /* We need a copy because m can be shorter than key_size, + * but _rsa_sec_compute_root_tr expect all inputs to be + * normalized to a key_size long buffer length */ + mpz_limbs_copy(m, gibberish, mpz_size(pub->n)); + + res = _rsa_sec_compute_root_tr (pub, key, random_ctx, random, m, m); mpn_get_base256 (em, key->size, m, mpz_size(pub->n)); Index: nettle-3.4.1/rsa-sign-tr.c =================================================================== --- nettle-3.4.1.orig/rsa-sign-tr.c +++ nettle-3.4.1/rsa-sign-tr.c @@ -131,35 +131,34 @@ int _rsa_sec_compute_root_tr(const struct rsa_public_key *pub, const struct rsa_private_key *key, void *random_ctx, nettle_random_func *random, - mp_limb_t *x, const mp_limb_t *m, size_t mn) + mp_limb_t *x, const mp_limb_t *m) { + mp_size_t nn; mpz_t mz; mpz_t xz; int res; - mpz_init(mz); mpz_init(xz); - mpn_copyi(mpz_limbs_write(mz, mn), m, mn); - mpz_limbs_finish(mz, mn); + nn = mpz_size (pub->n); - res = rsa_compute_root_tr(pub, key, random_ctx, random, xz, mz); + res = rsa_compute_root_tr(pub, key, random_ctx, random, xz, + mpz_roinit_n(mz, m, nn)); if (res) - mpz_limbs_copy(x, xz, mpz_size(pub->n)); + mpz_limbs_copy(x, xz, nn); - mpz_clear(mz); mpz_clear(xz); return res; } #else /* Blinds m, by computing c = m r^e (mod n), for a random r. Also - returns the inverse (ri), for use by rsa_unblind. */ + returns the inverse (ri), for use by rsa_unblind. Must have c != m, + no in-place operation.*/ static void rsa_sec_blind (const struct rsa_public_key *pub, void *random_ctx, nettle_random_func *random, - mp_limb_t *c, mp_limb_t *ri, const mp_limb_t *m, - mp_size_t mn) + mp_limb_t *c, mp_limb_t *ri, const mp_limb_t *m) { const mp_limb_t *ep = mpz_limbs_read (pub->e); const mp_limb_t *np = mpz_limbs_read (pub->n); @@ -177,15 +176,15 @@ rsa_sec_blind (const struct rsa_public_k /* c = m*(r^e) mod n */ itch = mpn_sec_powm_itch(nn, ebn, nn); - i2 = mpn_sec_mul_itch(nn, mn); + i2 = mpn_sec_mul_itch(nn, nn); itch = MAX(itch, i2); - i2 = mpn_sec_div_r_itch(nn + mn, nn); + i2 = mpn_sec_div_r_itch(2*nn, nn); itch = MAX(itch, i2); i2 = mpn_sec_invert_itch(nn); itch = MAX(itch, i2); - TMP_GMP_ALLOC (tp, nn + mn + itch); - scratch = tp + nn + mn; + TMP_GMP_ALLOC (tp, 2*nn + itch); + scratch = tp + 2*nn; /* ri = r^(-1) */ do @@ -198,9 +197,8 @@ rsa_sec_blind (const struct rsa_public_k while (!mpn_sec_invert (ri, tp, np, nn, 2 * nn * GMP_NUMB_BITS, scratch)); mpn_sec_powm (c, rp, nn, ep, ebn, np, nn, scratch); - /* normally mn == nn, but m can be smaller in some cases */ - mpn_sec_mul (tp, c, nn, m, mn, scratch); - mpn_sec_div_r (tp, nn + mn, np, nn, scratch); + mpn_sec_mul (tp, c, nn, m, nn, scratch); + mpn_sec_div_r (tp, 2*nn, np, nn, scratch); mpn_copyi(c, tp, nn); TMP_GMP_FREE (r); @@ -208,7 +206,7 @@ rsa_sec_blind (const struct rsa_public_k TMP_GMP_FREE (tp); } -/* m = c ri mod n */ +/* m = c ri mod n. Allows x == c. */ static void rsa_sec_unblind (const struct rsa_public_key *pub, mp_limb_t *x, mp_limb_t *ri, const mp_limb_t *c) @@ -298,7 +296,7 @@ int _rsa_sec_compute_root_tr(const struct rsa_public_key *pub, const struct rsa_private_key *key, void *random_ctx, nettle_random_func *random, - mp_limb_t *x, const mp_limb_t *m, size_t mn) + mp_limb_t *x, const mp_limb_t *m) { TMP_GMP_DECL (c, mp_limb_t); TMP_GMP_DECL (ri, mp_limb_t); @@ -306,7 +304,7 @@ _rsa_sec_compute_root_tr(const struct rs size_t key_limb_size; int ret; - key_limb_size = NETTLE_OCTET_SIZE_TO_LIMB_SIZE(key->size); + key_limb_size = mpz_size(pub->n); /* mpz_powm_sec handles only odd moduli. If p, q or n is even, the key is invalid and rejected by rsa_private_key_prepare. However, @@ -320,19 +318,18 @@ _rsa_sec_compute_root_tr(const struct rs } assert(mpz_size(pub->n) == key_limb_size); - assert(mn <= key_limb_size); TMP_GMP_ALLOC (c, key_limb_size); TMP_GMP_ALLOC (ri, key_limb_size); TMP_GMP_ALLOC (scratch, _rsa_sec_compute_root_itch(key)); - rsa_sec_blind (pub, random_ctx, random, x, ri, m, mn); + rsa_sec_blind (pub, random_ctx, random, c, ri, m); - _rsa_sec_compute_root(key, c, x, scratch); + _rsa_sec_compute_root(key, x, c, scratch); - ret = rsa_sec_check_root(pub, c, x); + ret = rsa_sec_check_root(pub, x, c); - rsa_sec_unblind(pub, x, ri, c); + rsa_sec_unblind(pub, x, ri, x); cnd_mpn_zero(1 - ret, x, key_limb_size); @@ -356,17 +353,17 @@ rsa_compute_root_tr(const struct rsa_pub mpz_t x, const mpz_t m) { TMP_GMP_DECL (l, mp_limb_t); + mp_size_t nn = mpz_size(pub->n); int res; - mp_size_t l_size = NETTLE_OCTET_SIZE_TO_LIMB_SIZE(key->size); - TMP_GMP_ALLOC (l, l_size); + TMP_GMP_ALLOC (l, nn); + mpz_limbs_copy(l, m, nn); - res = _rsa_sec_compute_root_tr (pub, key, random_ctx, random, l, - mpz_limbs_read(m), mpz_size(m)); + res = _rsa_sec_compute_root_tr (pub, key, random_ctx, random, l, l); if (res) { - mp_limb_t *xp = mpz_limbs_write (x, l_size); - mpn_copyi (xp, l, l_size); - mpz_limbs_finish (x, l_size); + mp_limb_t *xp = mpz_limbs_write (x, nn); + mpn_copyi (xp, l, nn); + mpz_limbs_finish (x, nn); } TMP_GMP_FREE (l); Index: nettle-3.4.1/testsuite/rsa-encrypt-test.c =================================================================== --- nettle-3.4.1.orig/testsuite/rsa-encrypt-test.c +++ nettle-3.4.1/testsuite/rsa-encrypt-test.c @@ -19,6 +19,7 @@ test_main(void) uint8_t after; mpz_t gibberish; + mpz_t zero; rsa_private_key_init(&key); rsa_public_key_init(&pub); @@ -101,6 +102,17 @@ test_main(void) ASSERT(decrypted[decrypted_length] == after); ASSERT(decrypted[0] == 'A'); + /* Test zero input. */ + mpz_init_set_ui (zero, 0); + decrypted_length = msg_length; + ASSERT(!rsa_decrypt(&key, &decrypted_length, decrypted, zero)); + ASSERT(!rsa_decrypt_tr(&pub, &key, + &lfib, (nettle_random_func *) knuth_lfib_random, + &decrypted_length, decrypted, zero)); + ASSERT(!rsa_sec_decrypt(&pub, &key, + &lfib, (nettle_random_func *) knuth_lfib_random, + decrypted_length, decrypted, zero)); + ASSERT(decrypted_length == msg_length); /* Test invalid key. */ mpz_add_ui (key.q, key.q, 2); @@ -112,6 +124,6 @@ test_main(void) rsa_private_key_clear(&key); rsa_public_key_clear(&pub); mpz_clear(gibberish); + mpz_clear(zero); free(decrypted); } -
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