--- /dev/null
+From 6450224f3e3c78fdfa37eadbe6ada8301279f6c1 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se>
+Date: Mon, 20 Jun 2016 20:04:56 +0200
+Subject: Use mpz_powm_sec.
+Subject: Check for invalid keys, with even p, in dsa_sign.
+Subject: Reject invalid keys, with even moduli, in rsa_compute_root_tr.
+Subject: Reject invalid RSA keys with even modulo.
+
+Patch status: upstream
+
+Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
+
+diff --git a/bignum.h b/bignum.h
+index 24158e0..0d30534 100644
+--- a/bignum.h
++++ b/bignum.h
+@@ -53,6 +53,8 @@
+ # define mpz_combit mpz_combit
+ # define mpz_import mpz_import
+ # define mpz_export mpz_export
++/* Side-channel silent powm not available in mini-gmp. */
++# define mpz_powm_sec mpz_powm
+ #else
+ # include <gmp.h>
+ #endif
+diff --git a/configure.ac b/configure.ac
+index e1ee64c..1e88477 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -236,9 +236,9 @@ fi
+ # Checks for libraries
+ if test "x$enable_public_key" = "xyes" ; then
+ if test "x$enable_mini_gmp" = "xno" ; then
+- AC_CHECK_LIB(gmp, __gmpz_getlimbn,,
++ AC_CHECK_LIB(gmp, __gmpz_powm_sec,,
+ [AC_MSG_WARN(
+- [GNU MP not found, or not 3.1 or up, see http://gmplib.org/.
++ [GNU MP not found, or too old. GMP-5.0 or later is needed, see http://gmplib.org/.
+ Support for public key algorithms will be unavailable.])]
+ enable_public_key=no)
+
+diff --git a/dsa-sign.c b/dsa-sign.c
+index 62c7d4a..b713743 100644
+--- a/dsa-sign.c
++++ b/dsa-sign.c
+@@ -56,6 +56,11 @@ dsa_sign(const struct dsa_params *params,
+ mpz_t tmp;
+ int res;
+
++ /* Check that p is odd, so that invalid keys don't result in a crash
++ inside mpz_powm_sec. */
++ if (mpz_even_p (params->p))
++ return 0;
++
+ /* Select k, 0<k<q, randomly */
+ mpz_init_set(tmp, params->q);
+ mpz_sub_ui(tmp, tmp, 1);
+@@ -65,7 +70,7 @@ dsa_sign(const struct dsa_params *params,
+ mpz_add_ui(k, k, 1);
+
+ /* Compute r = (g^k (mod p)) (mod q) */
+- mpz_powm(tmp, params->g, k, params->p);
++ mpz_powm_sec(tmp, params->g, k, params->p);
+ mpz_fdiv_r(signature->r, tmp, params->q);
+
+ /* Compute hash */
+diff --git a/rsa-blind.c b/rsa-blind.c
+index 7662f50..16b03d7 100644
+--- a/rsa-blind.c
++++ b/rsa-blind.c
+@@ -61,7 +61,7 @@ _rsa_blind (const struct rsa_public_key *pub,
+ while (!mpz_invert (ri, r, pub->n));
+
+ /* c = c*(r^e) mod n */
+- mpz_powm(r, r, pub->e, pub->n);
++ mpz_powm_sec(r, r, pub->e, pub->n);
+ mpz_mul(c, c, r);
+ mpz_fdiv_r(c, c, pub->n);
+
+diff --git a/rsa-sign-tr.c b/rsa-sign-tr.c
+index 3d80ed4..8542cae 100644
+--- a/rsa-sign-tr.c
++++ b/rsa-sign-tr.c
+@@ -60,7 +60,7 @@ rsa_blind (const struct rsa_public_key *pub,
+ while (!mpz_invert (ri, r, pub->n));
+
+ /* c = c*(r^e) mod n */
+- mpz_powm(r, r, pub->e, pub->n);
++ mpz_powm_sec(r, r, pub->e, pub->n);
+ mpz_mul(c, m, r);
+ mpz_fdiv_r(c, c, pub->n);
+
+@@ -88,6 +88,14 @@ rsa_compute_root_tr(const struct rsa_public_key *pub,
+ int res;
+ mpz_t t, mb, xb, ri;
+
++ /* 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,
++ some applications, notably gnutls, don't use this function, and
++ we don't want an invalid key to lead to a crash down inside
++ mpz_powm_sec. So do an additional check here. */
++ if (mpz_even_p (pub->n) || mpz_even_p (key->p) || mpz_even_p (key->q))
++ return 0;
++
+ mpz_init (mb);
+ mpz_init (xb);
+ mpz_init (ri);
+@@ -97,7 +105,7 @@ rsa_compute_root_tr(const struct rsa_public_key *pub,
+
+ rsa_compute_root (key, xb, mb);
+
+- mpz_powm(t, xb, pub->e, pub->n);
++ mpz_powm_sec(t, xb, pub->e, pub->n);
+ res = (mpz_cmp(mb, t) == 0);
+
+ if (res)
+diff --git a/rsa-sign.c b/rsa-sign.c
+index eba7388..4832352 100644
+--- a/rsa-sign.c
++++ b/rsa-sign.c
+@@ -96,11 +96,11 @@ rsa_compute_root(const struct rsa_private_key *key,
+
+ /* Compute xq = m^d % q = (m%q)^b % q */
+ mpz_fdiv_r(xq, m, key->q);
+- mpz_powm(xq, xq, key->b, key->q);
++ mpz_powm_sec(xq, xq, key->b, key->q);
+
+ /* Compute xp = m^d % p = (m%p)^a % p */
+ mpz_fdiv_r(xp, m, key->p);
+- mpz_powm(xp, xp, key->a, key->p);
++ mpz_powm_sec(xp, xp, key->a, key->p);
+
+ /* Set xp' = (xp - xq) c % p. */
+ mpz_sub(xp, xp, xq);
+diff --git a/rsa.c b/rsa.c
+index 19d93de..f594140 100644
+--- a/rsa.c
++++ b/rsa.c
+@@ -58,13 +58,18 @@ rsa_public_key_clear(struct rsa_public_key *key)
+ }
+
+ /* Computes the size, in octets, of a the modulo. Returns 0 if the
+- * modulo is too small to be useful. */
+-
++ * modulo is too small to be useful, or otherwise appears invalid. */
+ size_t
+ _rsa_check_size(mpz_t n)
+ {
+ /* Round upwards */
+- size_t size = (mpz_sizeinbase(n, 2) + 7) / 8;
++ size_t size;
++
++ /* Even moduli are invalid, and not supported by mpz_powm_sec. */
++ if (mpz_even_p (n))
++ return 0;
++
++ size = (mpz_sizeinbase(n, 2) + 7) / 8;
+
+ if (size < RSA_MINIMUM_N_OCTETS)
+ return 0;
+diff --git a/testsuite/rsa-test.c b/testsuite/rsa-test.c
+index e9b1c03..a429664 100644
+--- a/testsuite/rsa-test.c
++++ b/testsuite/rsa-test.c
+@@ -57,6 +57,13 @@ test_main(void)
+
+ test_rsa_sha512(&pub, &key, expected);
+
++ /* Test detection of invalid keys with even modulo */
++ mpz_clrbit (pub.n, 0);
++ ASSERT (!rsa_public_key_prepare (&pub));
++
++ mpz_clrbit (key.p, 0);
++ ASSERT (!rsa_private_key_prepare (&key));
++
+ /* 777-bit key, generated by
+ *
+ * lsh-keygen -a rsa -l 777 -f advanced-hex
+--
+2.7.3
+
projects / buildroot.git / commitdiff