From bea53f1b46a64d6dcf5bbe4794740c4d4459f9bf Mon Sep 17 00:00:00 2001
From: Daiki Ueno <ueno@gnu.org>
Date: Fri, 10 Jul 2020 09:35:49 +0200
Subject: [PATCH 1/5] dh: check validity of Z before export
SP800-56A rev3 section 5.7.1.1 step 2 mandates that the validity of the
calculated shared secret is verified before the data is returned to the
caller. This patch adds the validation check.
Suggested by Stephan Mueller.
Signed-off-by: Daiki Ueno <ueno@gnu.org>
---
lib/nettle/pk.c | 26 +++++++++++++++++---------
1 file changed, 17 insertions(+), 9 deletions(-)
diff --git a/lib/nettle/pk.c b/lib/nettle/pk.c
index 57a8560ed..08c7d4860 100644
--- a/lib/nettle/pk.c
+++ b/lib/nettle/pk.c
@@ -288,7 +288,7 @@ static int _wrap_nettle_pk_derive(gnutls_pk_algorithm_t algo,
switch (algo) {
case GNUTLS_PK_DH: {
bigint_t f, x, q, prime;
- bigint_t k = NULL, ff = NULL, r = NULL;
+ bigint_t k = NULL, primesub1 = NULL, r = NULL;
unsigned int bits;
if (nonce != NULL)
@@ -299,21 +299,20 @@ static int _wrap_nettle_pk_derive(gnutls_pk_algorithm_t algo,
q = priv->params[DH_Q];
prime = priv->params[DH_P];
- ret = _gnutls_mpi_init_multi(&k, &ff, &r, NULL);
+ ret = _gnutls_mpi_init_multi(&k, &primesub1, &r, NULL);
if (ret < 0)
return gnutls_assert_val(ret);
- ret = _gnutls_mpi_add_ui(ff, f, 1);
+ ret = _gnutls_mpi_sub_ui(primesub1, prime, 1);
if (ret < 0) {
gnutls_assert();
goto dh_cleanup;
}
- /* check if f==0,1, or f >= p-1.
- * or (ff=f+1) equivalently ff==1,2, ff >= p */
- if ((_gnutls_mpi_cmp_ui(ff, 2) == 0)
- || (_gnutls_mpi_cmp_ui(ff, 1) == 0)
- || (_gnutls_mpi_cmp(ff, prime) >= 0)) {
+ /* check if f==0,1, or f >= p-1 */
+ if ((_gnutls_mpi_cmp_ui(f, 1) == 0)
+ || (_gnutls_mpi_cmp_ui(f, 0) == 0)
+ || (_gnutls_mpi_cmp(f, primesub1) >= 0)) {
gnutls_assert();
ret = GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
goto dh_cleanup;
@@ -354,6 +353,15 @@ static int _wrap_nettle_pk_derive(gnutls_pk_algorithm_t algo,
goto dh_cleanup;
}
+ /* check if k==0,1, or k = p-1 */
+ if ((_gnutls_mpi_cmp_ui(k, 1) == 0)
+ || (_gnutls_mpi_cmp_ui(k, 0) == 0)
+ || (_gnutls_mpi_cmp(k, primesub1) == 0)) {
+ gnutls_assert();
+ ret = GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
+ goto dh_cleanup;
+ }
+
if (flags & PK_DERIVE_TLS13) {
ret =
_gnutls_mpi_dprint_size(k, out,
@@ -370,7 +378,7 @@ static int _wrap_nettle_pk_derive(gnutls_pk_algorithm_t algo,
ret = 0;
dh_cleanup:
_gnutls_mpi_release(&r);
- _gnutls_mpi_release(&ff);
+ _gnutls_mpi_release(&primesub1);
zrelease_temp_mpi_key(&k);
if (ret < 0)
goto cleanup;
--
2.26.2
From 13202600d3e42258d8758b05ff45a3e3d0f07e4e Mon Sep 17 00:00:00 2001
From: Daiki Ueno <ueno@gnu.org>
Date: Fri, 10 Jul 2020 09:42:30 +0200
Subject: [PATCH 2/5] ecdh: check validity of P before export
SP800-56A rev3 section 5.7.1.2 step 2 mandates that the validity of
the calculated shared secret is verified before the data is returned
to the caller. This patch adds the validation check.
Suggested by Stephan Mueller.
Signed-off-by: Daiki Ueno <ueno@gnu.org>
---
lib/nettle/pk.c | 27 +++++++++++++++++++++------
1 file changed, 21 insertions(+), 6 deletions(-)
diff --git a/lib/nettle/pk.c b/lib/nettle/pk.c
index 08c7d4860..7f0fa8e03 100644
--- a/lib/nettle/pk.c
+++ b/lib/nettle/pk.c
@@ -229,25 +229,38 @@ _gost_params_to_pubkey(const gnutls_pk_params_st * pk_params,
}
#endif
-static void
+static int
ecc_shared_secret(struct ecc_scalar *private_key,
struct ecc_point *public_key, void *out, unsigned size)
{
struct ecc_point r;
- mpz_t x;
+ mpz_t x, y;
+ int ret = 0;
mpz_init(x);
+ mpz_init(y);
ecc_point_init(&r, public_key->ecc);
ecc_point_mul(&r, private_key, public_key);
- ecc_point_get(&r, x, NULL);
+ ecc_point_get(&r, x, y);
+
+ /* Check if the point is not an identity element. Note that this cannot
+ * happen in nettle implementation, because it cannot represent an
+ * infinity point. */
+ if (mpz_cmp_ui(x, 0) == 0 && mpz_cmp_ui(y, 0) == 0) {
+ ret = gnutls_assert_val(GNUTLS_E_ILLEGAL_PARAMETER);
+ goto cleanup;
+ }
+
nettle_mpz_get_str_256(size, out, x);
+ cleanup:
mpz_clear(x);
+ mpz_clear(y);
ecc_point_clear(&r);
- return;
+ return ret;
}
#define MAX_DH_BITS DEFAULT_MAX_VERIFY_BITS
@@ -423,8 +436,10 @@ dh_cleanup:
goto ecc_cleanup;
}
- ecc_shared_secret(&ecc_priv, &ecc_pub, out->data,
- out->size);
+ ret = ecc_shared_secret(&ecc_priv, &ecc_pub, out->data,
+ out->size);
+ if (ret < 0)
+ gnutls_free(out->data);
ecc_cleanup:
ecc_point_clear(&ecc_pub);
--
2.26.2
From 245fb622e82bfa7b80d2cec7cafdbc65014ca3cb Mon Sep 17 00:00:00 2001
From: Daiki Ueno <ueno@gnu.org>
Date: Fri, 17 Jul 2020 17:45:17 +0200
Subject: [PATCH 3/5] dh-primes: make the FIPS approved check return Q value
This is necessary for full public key validation in
SP800-56A (revision 3), section 5.6.2.3.1.
Signed-off-by: Daiki Ueno <ueno@gnu.org>
---
lib/auth/dh_common.c | 2 +-
lib/dh-primes.c | 38 +++++++++++++++++++++++---------------
lib/dh.h | 10 ++++++----
3 files changed, 30 insertions(+), 20 deletions(-)
diff --git a/lib/auth/dh_common.c b/lib/auth/dh_common.c
index 252eea0cb..fcd696d4d 100644
--- a/lib/auth/dh_common.c
+++ b/lib/auth/dh_common.c
@@ -259,7 +259,7 @@ _gnutls_proc_dh_common_server_kx(gnutls_session_t session,
#ifdef ENABLE_FIPS140
if (gnutls_fips140_mode_enabled() &&
- !_gnutls_dh_prime_is_fips_approved(data_p, n_p, data_g, n_g)) {
+ !_gnutls_dh_prime_match_fips_approved(data_p, n_p, data_g, n_g, NULL, NULL)) {
gnutls_assert();
return GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER;
}
diff --git a/lib/dh-primes.c b/lib/dh-primes.c
index a43a8e5de..a440b5b98 100644
--- a/lib/dh-primes.c
+++ b/lib/dh-primes.c
@@ -1894,25 +1894,28 @@ const gnutls_datum_t gnutls_modp_8192_group_generator = {
const unsigned int gnutls_modp_8192_key_bits = 512;
unsigned
-_gnutls_dh_prime_is_fips_approved(const uint8_t *prime,
- size_t prime_size,
- const uint8_t *generator,
- size_t generator_size)
+_gnutls_dh_prime_match_fips_approved(const uint8_t *prime,
+ size_t prime_size,
+ const uint8_t *generator,
+ size_t generator_size,
+ uint8_t **q,
+ size_t *q_size)
{
static const struct {
const gnutls_datum_t *prime;
const gnutls_datum_t *generator;
+ const gnutls_datum_t *q;
} primes[] = {
- { &gnutls_ffdhe_8192_group_prime, &gnutls_ffdhe_8192_group_generator },
- { &gnutls_ffdhe_6144_group_prime, &gnutls_ffdhe_6144_group_generator },
- { &gnutls_ffdhe_4096_group_prime, &gnutls_ffdhe_4096_group_generator },
- { &gnutls_ffdhe_3072_group_prime, &gnutls_ffdhe_3072_group_generator },
- { &gnutls_ffdhe_2048_group_prime, &gnutls_ffdhe_2048_group_generator },
- { &gnutls_modp_8192_group_prime, &gnutls_modp_8192_group_generator },
- { &gnutls_modp_6144_group_prime, &gnutls_modp_6144_group_generator },
- { &gnutls_modp_4096_group_prime, &gnutls_modp_4096_group_generator },
- { &gnutls_modp_3072_group_prime, &gnutls_modp_3072_group_generator },
- { &gnutls_modp_2048_group_prime, &gnutls_modp_2048_group_generator },
+ { &gnutls_ffdhe_8192_group_prime, &gnutls_ffdhe_8192_group_generator, &gnutls_ffdhe_8192_group_q },
+ { &gnutls_ffdhe_6144_group_prime, &gnutls_ffdhe_6144_group_generator, &gnutls_ffdhe_6144_group_q },
+ { &gnutls_ffdhe_4096_group_prime, &gnutls_ffdhe_4096_group_generator, &gnutls_ffdhe_4096_group_q },
+ { &gnutls_ffdhe_3072_group_prime, &gnutls_ffdhe_3072_group_generator, &gnutls_ffdhe_3072_group_q },
+ { &gnutls_ffdhe_2048_group_prime, &gnutls_ffdhe_2048_group_generator, &gnutls_ffdhe_2048_group_q },
+ { &gnutls_modp_8192_group_prime, &gnutls_modp_8192_group_generator, &gnutls_modp_8192_group_q },
+ { &gnutls_modp_6144_group_prime, &gnutls_modp_6144_group_generator, &gnutls_modp_6144_group_q },
+ { &gnutls_modp_4096_group_prime, &gnutls_modp_4096_group_generator, &gnutls_modp_4096_group_q },
+ { &gnutls_modp_3072_group_prime, &gnutls_modp_3072_group_generator, &gnutls_modp_3072_group_q },
+ { &gnutls_modp_2048_group_prime, &gnutls_modp_2048_group_generator, &gnutls_modp_2048_group_q },
};
size_t i;
@@ -1920,8 +1923,13 @@ _gnutls_dh_prime_is_fips_approved(const uint8_t *prime,
if (primes[i].prime->size == prime_size &&
memcmp(primes[i].prime->data, prime, primes[i].prime->size) == 0 &&
primes[i].generator->size == generator_size &&
- memcmp(primes[i].generator->data, generator, primes[i].generator->size) == 0)
+ memcmp(primes[i].generator->data, generator, primes[i].generator->size) == 0) {
+ if (q) {
+ *q = primes[i].q->data;
+ *q_size = primes[i].q->size;
+ }
return 1;
+ }
}
return 0;
diff --git a/lib/dh.h b/lib/dh.h
index 672451947..f5c2c0924 100644
--- a/lib/dh.h
+++ b/lib/dh.h
@@ -61,9 +61,11 @@ extern const gnutls_datum_t gnutls_modp_2048_group_generator;
extern const unsigned int gnutls_modp_2048_key_bits;
unsigned
-_gnutls_dh_prime_is_fips_approved(const uint8_t *prime,
- size_t prime_size,
- const uint8_t *generator,
- size_t generator_size);
+_gnutls_dh_prime_match_fips_approved(const uint8_t *prime,
+ size_t prime_size,
+ const uint8_t *generator,
+ size_t generator_size,
+ uint8_t **q,
+ size_t *q_size);
#endif /* GNUTLS_LIB_DH_H */
--
2.26.2
From 8b575625614fbe5a22b68dc8d1877efb1d44dd37 Mon Sep 17 00:00:00 2001
From: Daiki Ueno <ueno@gnu.org>
Date: Fri, 17 Jul 2020 17:47:06 +0200
Subject: [PATCH 4/5] dh: perform SP800-56A rev3 full pubkey validation on
keygen
This implements full public key validation required in SP800-56A rev3,
section 5.6.2.3.1.
Signed-off-by: Daiki Ueno <ueno@gnu.org>
---
lib/nettle/pk.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 90 insertions(+)
diff --git a/lib/nettle/pk.c b/lib/nettle/pk.c
index 7f0fa8e03..057836bc2 100644
--- a/lib/nettle/pk.c
+++ b/lib/nettle/pk.c
@@ -71,6 +71,7 @@
#include "int/dsa-compute-k.h"
#include <gnettle.h>
#include <fips.h>
+#include "dh.h"
static inline const struct ecc_curve *get_supported_nist_curve(int curve);
static inline const struct ecc_curve *get_supported_gost_curve(int curve);
@@ -2131,6 +2132,53 @@ edwards_curve_mul_g(gnutls_pk_algorithm_t algo,
}
}
+static inline int
+dh_find_q(const gnutls_pk_params_st *pk_params, mpz_t q)
+{
+ gnutls_datum_t prime = { NULL, 0 };
+ gnutls_datum_t generator = { NULL, 0 };
+ uint8_t *data_q;
+ size_t n_q;
+ bigint_t _q;
+ int ret = 0;
+
+ ret = _gnutls_mpi_dprint(pk_params->params[DSA_P], &prime);
+ if (ret < 0) {
+ gnutls_assert();
+ goto cleanup;
+ }
+
+ ret = _gnutls_mpi_dprint(pk_params->params[DSA_G], &generator);
+ if (ret < 0) {
+ gnutls_assert();
+ goto cleanup;
+ }
+
+ if (!_gnutls_dh_prime_match_fips_approved(prime.data,
+ prime.size,
+ generator.data,
+ generator.size,
+ &data_q,
+ &n_q)) {
+ ret = gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
+ goto cleanup;
+ }
+
+ if (_gnutls_mpi_init_scan_nz(&_q, data_q, n_q) != 0) {
+ ret = gnutls_assert_val(GNUTLS_E_MPI_SCAN_FAILED);
+ goto cleanup;
+ }
+
+ mpz_set(q, TOMPZ(_q));
+ _gnutls_mpi_release(&_q);
+
+ cleanup:
+ gnutls_free(prime.data);
+ gnutls_free(generator.data);
+
+ return ret;
+}
+
/* To generate a DH key either q must be set in the params or
* level should be set to the number of required bits.
*/
@@ -2212,6 +2260,9 @@ wrap_nettle_pk_generate_keys(gnutls_pk_algorithm_t algo,
mpz_t x, y;
int max_tries;
unsigned have_q = 0;
+ mpz_t q;
+ mpz_t primesub1;
+ mpz_t ypowq;
if (algo != params->algo)
return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
@@ -2229,6 +2280,10 @@ wrap_nettle_pk_generate_keys(gnutls_pk_algorithm_t algo,
mpz_init(x);
mpz_init(y);
+ mpz_init(q);
+ mpz_init(primesub1);
+ mpz_init(ypowq);
+
max_tries = 3;
do {
if (have_q) {
@@ -2260,8 +2315,40 @@ wrap_nettle_pk_generate_keys(gnutls_pk_algorithm_t algo,
ret = GNUTLS_E_LIB_IN_ERROR_STATE;
goto dh_fail;
}
+
} while(mpz_cmp_ui(y, 1) == 0);
+#ifdef ENABLE_FIPS140
+ if (_gnutls_fips_mode_enabled()) {
+ /* Perform FFC full public key validation checks
+ * according to SP800-56A (revision 3), 5.6.2.3.1.
+ */
+
+ /* Step 1: 2 <= y <= p - 2 */
+ mpz_sub_ui(primesub1, pub.p, 1);
+
+ if (mpz_cmp_ui(y, 2) < 0 || mpz_cmp(y, primesub1) >= 0) {
+ ret = gnutls_assert_val(GNUTLS_E_RANDOM_FAILED);
+ goto dh_fail;
+ }
+
+ /* Step 2: 1 = y^q mod p */
+ if (have_q)
+ mpz_set(q, pub.q);
+ else {
+ ret = dh_find_q(params, q);
+ if (ret < 0)
+ goto dh_fail;
+ }
+
+ mpz_powm(ypowq, y, q, pub.p);
+ if (mpz_cmp_ui(ypowq, 1) != 0) {
+ ret = gnutls_assert_val(GNUTLS_E_RANDOM_FAILED);
+ goto dh_fail;
+ }
+ }
+#endif
+
ret = _gnutls_mpi_init_multi(¶ms->params[DSA_Y], ¶ms->params[DSA_X], NULL);
if (ret < 0) {
gnutls_assert();
@@ -2278,6 +2365,9 @@ wrap_nettle_pk_generate_keys(gnutls_pk_algorithm_t algo,
mpz_clear(r);
mpz_clear(x);
mpz_clear(y);
+ mpz_clear(q);
+ mpz_clear(primesub1);
+ mpz_clear(ypowq);
if (ret < 0)
goto fail;
--
2.26.2
From 23756c8580dff99d0856adca49dd22a55352ad62 Mon Sep 17 00:00:00 2001
From: Daiki Ueno <ueno@gnu.org>
Date: Sat, 18 Jul 2020 08:26:48 +0200
Subject: [PATCH 5/5] ecdh: perform SP800-56A rev3 full pubkey validation on
keygen
This implements full public key validation required in
SP800-56A rev3, section 5.6.2.3.3.
Signed-off-by: Daiki Ueno <ueno@gnu.org>
---
lib/nettle/pk.c | 182 +++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 180 insertions(+), 2 deletions(-)
diff --git a/lib/nettle/pk.c b/lib/nettle/pk.c
index 057836bc2..588e9df50 100644
--- a/lib/nettle/pk.c
+++ b/lib/nettle/pk.c
@@ -1552,6 +1552,80 @@ static inline const struct ecc_curve *get_supported_nist_curve(int curve)
}
}
+static inline const char *get_supported_nist_curve_order(int curve)
+{
+ static const struct {
+ int curve;
+ const char *order;
+ } orders[] = {
+#ifdef ENABLE_NON_SUITEB_CURVES
+ { GNUTLS_ECC_CURVE_SECP192R1,
+ "ffffffffffffffffffffffff99def836"
+ "146bc9b1b4d22831" },
+ { GNUTLS_ECC_CURVE_SECP224R1,
+ "ffffffffffffffffffffffffffff16a2"
+ "e0b8f03e13dd29455c5c2a3d" },
+#endif
+ { GNUTLS_ECC_CURVE_SECP256R1,
+ "ffffffff00000000ffffffffffffffff"
+ "bce6faada7179e84f3b9cac2fc632551" },
+ { GNUTLS_ECC_CURVE_SECP384R1,
+ "ffffffffffffffffffffffffffffffff"
+ "ffffffffffffffffc7634d81f4372ddf"
+ "581a0db248b0a77aecec196accc52973" },
+ { GNUTLS_ECC_CURVE_SECP521R1,
+ "1fffffffffffffffffffffffffffffff"
+ "ffffffffffffffffffffffffffffffff"
+ "ffa51868783bf2f966b7fcc0148f709a"
+ "5d03bb5c9b8899c47aebb6fb71e91386"
+ "409" },
+ };
+ size_t i;
+
+ for (i = 0; i < sizeof(orders)/sizeof(orders[0]); i++) {
+ if (orders[i].curve == curve)
+ return orders[i].order;
+ }
+ return NULL;
+}
+
+static inline const char *get_supported_nist_curve_modulus(int curve)
+{
+ static const struct {
+ int curve;
+ const char *order;
+ } orders[] = {
+#ifdef ENABLE_NON_SUITEB_CURVES
+ { GNUTLS_ECC_CURVE_SECP192R1,
+ "fffffffffffffffffffffffffffffffe"
+ "ffffffffffffffff" },
+ { GNUTLS_ECC_CURVE_SECP224R1,
+ "ffffffffffffffffffffffffffffffff"
+ "000000000000000000000001" },
+#endif
+ { GNUTLS_ECC_CURVE_SECP256R1,
+ "ffffffff000000010000000000000000"
+ "00000000ffffffffffffffffffffffff" },
+ { GNUTLS_ECC_CURVE_SECP384R1,
+ "ffffffffffffffffffffffffffffffff"
+ "fffffffffffffffffffffffffffffffe"
+ "ffffffff0000000000000000ffffffff" },
+ { GNUTLS_ECC_CURVE_SECP521R1,
+ "1ff"
+ "ffffffffffffffffffffffffffffffff"
+ "ffffffffffffffffffffffffffffffff"
+ "ffffffffffffffffffffffffffffffff"
+ "ffffffffffffffffffffffffffffffff" },
+ };
+ size_t i;
+
+ for (i = 0; i < sizeof(orders)/sizeof(orders[0]); i++) {
+ if (orders[i].curve == curve)
+ return orders[i].order;
+ }
+ return NULL;
+}
+
static inline const struct ecc_curve *get_supported_gost_curve(int curve)
{
switch (curve) {
@@ -2507,6 +2581,10 @@ wrap_nettle_pk_generate_keys(gnutls_pk_algorithm_t algo,
struct ecc_scalar key;
struct ecc_point pub;
const struct ecc_curve *curve;
+ struct ecc_scalar n;
+ struct ecc_scalar m;
+ struct ecc_point r;
+ mpz_t x, y, xx, yy, nn, mm;
curve = get_supported_nist_curve(level);
if (curve == NULL)
@@ -2514,8 +2592,18 @@ wrap_nettle_pk_generate_keys(gnutls_pk_algorithm_t algo,
gnutls_assert_val
(GNUTLS_E_ECC_UNSUPPORTED_CURVE);
+ mpz_init(x);
+ mpz_init(y);
+ mpz_init(xx);
+ mpz_init(yy);
+ mpz_init(nn);
+ mpz_init(mm);
+
ecc_scalar_init(&key, curve);
ecc_point_init(&pub, curve);
+ ecc_scalar_init(&n, curve);
+ ecc_scalar_init(&m, curve);
+ ecc_point_init(&r, curve);
ecdsa_generate_keypair(&pub, &key, NULL, rnd_func);
if (HAVE_LIB_ERROR()) {
@@ -2533,15 +2621,105 @@ wrap_nettle_pk_generate_keys(gnutls_pk_algorithm_t algo,
params->curve = level;
params->params_nr = ECC_PRIVATE_PARAMS;
- ecc_point_get(&pub, TOMPZ(params->params[ECC_X]),
- TOMPZ(params->params[ECC_Y]));
+ ecc_point_get(&pub, x, y);
+
+#ifdef ENABLE_FIPS140
+ if (_gnutls_fips_mode_enabled()) {
+ /* Perform ECC full public key validation checks
+ * according to SP800-56A (revision 3), 5.6.2.3.3.
+ */
+
+ const char *order, *modulus;
+
+ /* Step 1: verify that Q is not an identity
+ * element (an infinity point). Note that this
+ * cannot happen in the nettle implementation,
+ * because it cannot represent an infinity point
+ * on curves. */
+ if (mpz_cmp_ui(x, 0) == 0 && mpz_cmp_ui(y, 0) == 0) {
+ ret = gnutls_assert_val(GNUTLS_E_ILLEGAL_PARAMETER);
+ goto ecc_fail;
+ }
+
+ /* Step 2: verify that both coordinates of Q are
+ * in the range [0, p - 1].
+ *
+ * Step 3: verify that Q lie on the curve
+ *
+ * Both checks are performed in nettle. */
+ if (!ecc_point_set(&r, x, y)) {
+ ret = gnutls_assert_val(GNUTLS_E_ILLEGAL_PARAMETER);
+ goto ecc_fail;
+ }
+
+ /* Step 4: verify that n * Q, where n is the
+ * curve order, result in an identity element
+ *
+ * Since nettle internally cannot represent an
+ * identity element on curves, we validate this
+ * instead:
+ *
+ * (n - 1) * Q = -Q
+ *
+ * That effectively means: n * Q = -Q + Q = O
+ */
+ order = get_supported_nist_curve_order(level);
+ if (unlikely(order == NULL)) {
+ ret = gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
+ goto ecc_fail;
+ }
+
+ ret = mpz_set_str(nn, order, 16);
+ if (unlikely(ret < 0)) {
+ ret = gnutls_assert_val(GNUTLS_E_MPI_SCAN_FAILED);
+ goto ecc_fail;
+ }
+
+ modulus = get_supported_nist_curve_modulus(level);
+ if (unlikely(modulus == NULL)) {
+ ret = gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
+ goto ecc_fail;
+ }
+
+ ret = mpz_set_str(mm, modulus, 16);
+ if (unlikely(ret < 0)) {
+ ret = gnutls_assert_val(GNUTLS_E_MPI_SCAN_FAILED);
+ goto ecc_fail;
+ }
+
+ /* (n - 1) * Q = -Q */
+ mpz_sub_ui (nn, nn, 1);
+ ecc_scalar_set(&n, nn);
+ ecc_point_mul(&r, &n, &r);
+ ecc_point_get(&r, xx, yy);
+ mpz_sub (mm, mm, y);
+
+ if (mpz_cmp(xx, x) != 0 || mpz_cmp(yy, mm) != 0) {
+ ret = gnutls_assert_val(GNUTLS_E_ILLEGAL_PARAMETER);
+ goto ecc_fail;
+ }
+ }
+#endif
+
+ mpz_set(TOMPZ(params->params[ECC_X]), x);
+ mpz_set(TOMPZ(params->params[ECC_Y]), y);
+
ecc_scalar_get(&key, TOMPZ(params->params[ECC_K]));
ret = 0;
ecc_fail:
+ mpz_clear(x);
+ mpz_clear(y);
+ mpz_clear(xx);
+ mpz_clear(yy);
+ mpz_clear(nn);
+ mpz_clear(mm);
ecc_point_clear(&pub);
ecc_scalar_clear(&key);
+ ecc_point_clear(&r);
+ ecc_scalar_clear(&n);
+ ecc_scalar_clear(&m);
if (ret < 0)
goto fail;
--
2.26.2