[ec] Match built-in curves on EC_GROUP_new_from_ecparameters

Description
-----------

Upon `EC_GROUP_new_from_ecparameters()` check if the parameters match any
of the built-in curves. If that is the case, return a new
`EC_GROUP_new_by_curve_name()` object instead of the explicit parameters
`EC_GROUP`.

This affects all users of `EC_GROUP_new_from_ecparameters()`:
- direct calls to `EC_GROUP_new_from_ecparameters()`
- direct calls to `EC_GROUP_new_from_ecpkparameters()` with an explicit
  parameters argument
- ASN.1 parsing of explicit parameters keys (as it eventually
  ends up calling `EC_GROUP_new_from_ecpkparameters()`)

A parsed explicit parameter key will still be marked with the
`OPENSSL_EC_EXPLICIT_CURVE` ASN.1 flag on load, so, unless
programmatically forced otherwise, if the key is eventually serialized
the output will still be encoded with explicit parameters, even if
internally it is treated as a named curve `EC_GROUP`.

Before this change, creating any `EC_GROUP` object using
`EC_GROUP_new_from_ecparameters()`, yielded an object associated with
the default generic `EC_METHOD`, but this was never guaranteed in the
documentation.
After this commit, users of the library that intentionally want to
create an `EC_GROUP` object using a specific `EC_METHOD` can still
explicitly call `EC_GROUP_new(foo_method)` and then manually set the
curve parameters using `EC_GROUP_set_*()`.

Motivation
----------

This has obvious performance benefits for the built-in curves with
specialized `EC_METHOD`s and subtle but important security benefits:
- the specialized methods have better security hardening than the
  generic implementations
- optional fields in the parameter encoding, like the `cofactor`, cannot
  be leveraged by an attacker to force execution of the less secure
  code-paths for single point scalar multiplication
- in general, this leads to reducing the attack surface

Check the manuscript at https://arxiv.org/abs/1909.01785 for an in depth
analysis of the issues related to this commit.

It should be noted that `libssl` does not allow to negotiate explicit
parameters (as per RFC 8422), so it is not directly affected by the
consequences of using explicit parameters that this commit fixes.
On the other hand, we detected external applications and users in the
wild that use explicit parameters by default (and sometimes using 0 as
the cofactor value, which is technically not a valid value per the
specification, but is tolerated by parsers for wider compatibility given
that the field is optional).
These external users of `libcrypto` are exposed to these vulnerabilities
and their security will benefit from this commit.

Related commits
---------------

While this commit is beneficial for users using built-in curves and
explicit parameters encoding for serialized keys, commit
b783beeadf6b80bc431e6f3230b5d5585c87ef87 (and its equivalents for the
1.0.2, 1.1.0 and 1.1.1 stable branches) fixes the consequences of the
invalid cofactor values more in general also for other curves
(CVE-2019-1547).

The following list covers commits in `master` that are related to the
vulnerabilities presented in the manuscript motivating this commit:

- d2baf88c43 [crypto/rsa] Set the constant-time flag in multi-prime RSA too
- 311e903d84 [crypto/asn1] Fix multiple SCA vulnerabilities during RSA key validation.
- b783beeadf [crypto/ec] for ECC parameters with NULL or zero cofactor, compute it
- 724339ff44 Fix SCA vulnerability when using PVK and MSBLOB key formats

Note that the PRs that contributed the listed commits also include other
commits providing related testing and documentation, in addition to
links to PRs and commits backporting the fixes to the 1.0.2, 1.1.0 and
1.1.1 branches.

This commit includes a partial backport of
https://github.com/openssl/openssl/pull/8555
(commit 8402cd5f75f8c2f60d8bd39775b24b03dd8b3b38)
for which the main author is Shane Lontis.

Responsible Disclosure
----------------------

This and the other issues presented in https://arxiv.org/abs/1909.01785
were reported by Cesar Pereida García, Sohaib ul Hassan, Nicola Tuveri,
Iaroslav Gridin, Alejandro Cabrera Aldaya and Billy Bob Brumley from the
NISEC group at Tampere University, FINLAND.

The OpenSSL Security Team evaluated the security risk for this
vulnerability as low, and encouraged to propose fixes using public Pull
Requests.

_______________________________________________________________________________

Co-authored-by: Shane Lontis <shane.lontis@oracle.com>

(Backport from https://github.com/openssl/openssl/pull/9808)

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9809)

1 files changed, 268 insertions, 1 deletions

diff --git a/test/ectest.c b/test/ectest.c
index ddc4ea11d6..ebd831ca40 100644
--- a/test/ectest.c
+++ b/test/ectest.c
@@ -1519,6 +1519,271 @@ static const unsigned char p521_explicit[] = {
     0xbb, 0x6f, 0xb7, 0x1e, 0x91, 0x38, 0x64, 0x09, 0x02, 0x01, 0x01,
 };
 
+/*
+ * Sometime we cannot compare nids for equality, as the built-in curve table
+ * includes aliases with different names for the same curve.
+ *
+ * This function returns TRUE (1) if the checked nids are identical, or if they
+ * alias to the same curve. FALSE (0) otherwise.
+ */
+static ossl_inline
+int are_ec_nids_compatible(int n1d, int n2d)
+{
+    int ret = 0;
+    switch (n1d) {
+# ifndef OPENSSL_NO_EC2M
+        case NID_sect113r1:
+        case NID_wap_wsg_idm_ecid_wtls4:
+            ret = (n2d == NID_sect113r1 || n2d == NID_wap_wsg_idm_ecid_wtls4);
+            break;
+        case NID_sect163k1:
+        case NID_wap_wsg_idm_ecid_wtls3:
+            ret = (n2d == NID_sect163k1 || n2d == NID_wap_wsg_idm_ecid_wtls3);
+            break;
+        case NID_sect233k1:
+        case NID_wap_wsg_idm_ecid_wtls10:
+            ret = (n2d == NID_sect233k1 || n2d == NID_wap_wsg_idm_ecid_wtls10);
+            break;
+        case NID_sect233r1:
+        case NID_wap_wsg_idm_ecid_wtls11:
+            ret = (n2d == NID_sect233r1 || n2d == NID_wap_wsg_idm_ecid_wtls11);
+            break;
+        case NID_X9_62_c2pnb163v1:
+        case NID_wap_wsg_idm_ecid_wtls5:
+            ret = (n2d == NID_X9_62_c2pnb163v1
+                   || n2d == NID_wap_wsg_idm_ecid_wtls5);
+            break;
+# endif /* OPENSSL_NO_EC2M */
+        case NID_secp112r1:
+        case NID_wap_wsg_idm_ecid_wtls6:
+            ret = (n2d == NID_secp112r1 || n2d == NID_wap_wsg_idm_ecid_wtls6);
+            break;
+        case NID_secp160r2:
+        case NID_wap_wsg_idm_ecid_wtls7:
+            ret = (n2d == NID_secp160r2 || n2d == NID_wap_wsg_idm_ecid_wtls7);
+            break;
+# ifdef OPENSSL_NO_EC_NISTP_64_GCC_128
+        case NID_secp224r1:
+        case NID_wap_wsg_idm_ecid_wtls12:
+            ret = (n2d == NID_secp224r1 || n2d == NID_wap_wsg_idm_ecid_wtls12);
+            break;
+# else
+        /*
+         * For SEC P-224 we want to ensure that the SECP nid is returned, as
+         * that is associated with a specialized method.
+         */
+        case NID_wap_wsg_idm_ecid_wtls12:
+            ret = (n2d == NID_secp224r1);
+            break;
+# endif /* def(OPENSSL_NO_EC_NISTP_64_GCC_128) */
+
+        default:
+            ret = (n1d == n2d);
+    }
+    return ret;
+}
+
+/*
+ * This checks that EC_GROUP_bew_from_ecparameters() returns a "named"
+ * EC_GROUP for built-in curves.
+ *
+ * Note that it is possible to retrieve an alternative alias that does not match
+ * the original nid.
+ *
+ * Ensure that the OPENSSL_EC_EXPLICIT_CURVE ASN1 flag is set.
+ */
+static int check_named_curve_from_ecparameters(int id)
+{
+    int ret = 0, nid, tnid;
+    EC_GROUP *group = NULL, *tgroup = NULL, *tmpg = NULL;
+    const EC_POINT *group_gen = NULL;
+    EC_POINT *other_gen = NULL;
+    BIGNUM *group_cofactor = NULL, *other_cofactor = NULL;
+    BIGNUM *other_gen_x = NULL, *other_gen_y = NULL;
+    const BIGNUM *group_order = NULL;
+    BIGNUM *other_order = NULL;
+    BN_CTX *bn_ctx = NULL;
+    static const unsigned char invalid_seed[] = "THIS IS NOT A VALID SEED";
+    static size_t invalid_seed_len = sizeof(invalid_seed);
+    ECPARAMETERS *params = NULL, *other_params = NULL;
+    EC_GROUP *g_ary[8] = {NULL};
+    EC_GROUP **g_next = &g_ary[0];
+    ECPARAMETERS *p_ary[8] = {NULL};
+    ECPARAMETERS **p_next = &p_ary[0];
+
+    /* Do some setup */
+    nid = curves[id].nid;
+    TEST_note("Curve %s", OBJ_nid2sn(nid));
+    if (!TEST_ptr(bn_ctx = BN_CTX_new()))
+        return ret;
+    BN_CTX_start(bn_ctx);
+
+    if (/* Allocations */
+        !TEST_ptr(group_cofactor = BN_CTX_get(bn_ctx))
+        || !TEST_ptr(other_gen_x = BN_CTX_get(bn_ctx))
+        || !TEST_ptr(other_gen_y = BN_CTX_get(bn_ctx))
+        || !TEST_ptr(other_order = BN_CTX_get(bn_ctx))
+        || !TEST_ptr(other_cofactor = BN_CTX_get(bn_ctx))
+        /* Generate reference group and params */
+        || !TEST_ptr(group = EC_GROUP_new_by_curve_name(nid))
+        || !TEST_ptr(params = EC_GROUP_get_ecparameters(group, NULL))
+        || !TEST_ptr(group_gen = EC_GROUP_get0_generator(group))
+        || !TEST_ptr(group_order = EC_GROUP_get0_order(group))
+        || !TEST_true(EC_GROUP_get_cofactor(group, group_cofactor, NULL))
+        /* compute `other_*` values */
+        || !TEST_ptr(tmpg = EC_GROUP_dup(group))
+        || !TEST_ptr(other_gen = EC_POINT_dup(group_gen, group))
+        || !TEST_true(EC_POINT_add(group, other_gen, group_gen, group_gen, NULL))
+        || !TEST_true(EC_POINT_get_affine_coordinates(group, other_gen,
+                      other_gen_x, other_gen_y, bn_ctx))
+        || !TEST_true(BN_copy(other_order, group_order))
+        || !TEST_true(BN_add_word(other_order, 1))
+        || !TEST_true(BN_copy(other_cofactor, group_cofactor))
+        || !TEST_true(BN_add_word(other_cofactor, 1)))
+        goto err;
+
+    EC_POINT_free(other_gen);
+    other_gen = NULL;
+
+    if (!TEST_ptr(other_gen = EC_POINT_new(tmpg))
+        || !TEST_true(EC_POINT_set_affine_coordinates(tmpg, other_gen,
+                                                      other_gen_x, other_gen_y,
+                                                      bn_ctx)))
+        goto err;
+
+    /*
+     * ###########################
+     * # Actual tests start here #
+     * ###########################
+     */
+
+    /*
+     * Creating a group from built-in explicit parameters returns a
+     * "named" EC_GROUP
+     */
+    if (!TEST_ptr(tgroup = *g_next++ = EC_GROUP_new_from_ecparameters(params))
+        || !TEST_int_ne((tnid = EC_GROUP_get_curve_name(tgroup)), NID_undef))
+        goto err;
+    /*
+     * We cannot always guarantee the names match, as the built-in table
+     * contains aliases for the same curve with different names.
+     */
+    if (!TEST_true(are_ec_nids_compatible(nid, tnid))) {
+        TEST_info("nid = %s, tnid = %s", OBJ_nid2sn(nid), OBJ_nid2sn(tnid));
+        goto err;
+    }
+    /* Ensure that the OPENSSL_EC_EXPLICIT_CURVE ASN1 flag is set. */
+    if (!TEST_int_eq(EC_GROUP_get_asn1_flag(tgroup), OPENSSL_EC_EXPLICIT_CURVE))
+        goto err;
+
+    /*
+     * An invalid seed in the parameters should be ignored: expect a "named"
+     * group.
+     */
+    if (!TEST_int_eq(EC_GROUP_set_seed(tmpg, invalid_seed, invalid_seed_len),
+                     invalid_seed_len)
+            || !TEST_ptr(other_params = *p_next++ =
+                         EC_GROUP_get_ecparameters(tmpg, NULL))
+            || !TEST_ptr(tgroup = *g_next++ =
+                          EC_GROUP_new_from_ecparameters(other_params))
+            || !TEST_int_ne((tnid = EC_GROUP_get_curve_name(tgroup)), NID_undef)
+            || !TEST_true(are_ec_nids_compatible(nid, tnid))
+            || !TEST_int_eq(EC_GROUP_get_asn1_flag(tgroup),
+                            OPENSSL_EC_EXPLICIT_CURVE)) {
+        TEST_info("nid = %s, tnid = %s", OBJ_nid2sn(nid), OBJ_nid2sn(tnid));
+        goto err;
+    }
+
+    /*
+     * A null seed in the parameters should be ignored, as it is optional:
+     * expect a "named" group.
+     */
+    if (!TEST_int_eq(EC_GROUP_set_seed(tmpg, NULL, 0), 1)
+            || !TEST_ptr(other_params = *p_next++ =
+                         EC_GROUP_get_ecparameters(tmpg, NULL))
+            || !TEST_ptr(tgroup = *g_next++ =
+                          EC_GROUP_new_from_ecparameters(other_params))
+            || !TEST_int_ne((tnid = EC_GROUP_get_curve_name(tgroup)), NID_undef)
+            || !TEST_true(are_ec_nids_compatible(nid, tnid))
+            || !TEST_int_eq(EC_GROUP_get_asn1_flag(tgroup),
+                            OPENSSL_EC_EXPLICIT_CURVE)) {
+        TEST_info("nid = %s, tnid = %s", OBJ_nid2sn(nid), OBJ_nid2sn(tnid));
+        goto err;
+    }
+
+    /*
+     * Check that changing any of the generator parameters does not yield a
+     * match with the built-in curves
+     */
+    if (/* Other gen, same group order & cofactor */
+        !TEST_true(EC_GROUP_set_generator(tmpg, other_gen, group_order,
+                                          group_cofactor))
+        || !TEST_ptr(other_params = *p_next++ =
+                     EC_GROUP_get_ecparameters(tmpg, NULL))
+        || !TEST_ptr(tgroup = *g_next++ =
+                      EC_GROUP_new_from_ecparameters(other_params))
+        || !TEST_int_eq((tnid = EC_GROUP_get_curve_name(tgroup)), NID_undef)
+        /* Same gen & cofactor, different order */
+        || !TEST_true(EC_GROUP_set_generator(tmpg, group_gen, other_order,
+                                             group_cofactor))
+        || !TEST_ptr(other_params = *p_next++ =
+                     EC_GROUP_get_ecparameters(tmpg, NULL))
+        || !TEST_ptr(tgroup = *g_next++ =
+                      EC_GROUP_new_from_ecparameters(other_params))
+        || !TEST_int_eq((tnid = EC_GROUP_get_curve_name(tgroup)), NID_undef)
+        /* The order is not an optional field, so this should fail */
+        || !TEST_false(EC_GROUP_set_generator(tmpg, group_gen, NULL,
+                                              group_cofactor))
+        /* Check that a wrong cofactor is ignored, and we still match */
+        || !TEST_true(EC_GROUP_set_generator(tmpg, group_gen, group_order,
+                                             other_cofactor))
+        || !TEST_ptr(other_params = *p_next++ =
+                     EC_GROUP_get_ecparameters(tmpg, NULL))
+        || !TEST_ptr(tgroup = *g_next++ =
+                      EC_GROUP_new_from_ecparameters(other_params))
+        || !TEST_int_ne((tnid = EC_GROUP_get_curve_name(tgroup)), NID_undef)
+        || !TEST_true(are_ec_nids_compatible(nid, tnid))
+        || !TEST_int_eq(EC_GROUP_get_asn1_flag(tgroup),
+                        OPENSSL_EC_EXPLICIT_CURVE)
+        /* Check that if the cofactor is not set then it still matches */
+        || !TEST_true(EC_GROUP_set_generator(tmpg, group_gen, group_order,
+                                             NULL))
+        || !TEST_ptr(other_params = *p_next++ =
+                     EC_GROUP_get_ecparameters(tmpg, NULL))
+        || !TEST_ptr(tgroup = *g_next++ =
+                      EC_GROUP_new_from_ecparameters(other_params))
+        || !TEST_int_ne((tnid = EC_GROUP_get_curve_name(tgroup)), NID_undef)
+        || !TEST_true(are_ec_nids_compatible(nid, tnid))
+        || !TEST_int_eq(EC_GROUP_get_asn1_flag(tgroup),
+                        OPENSSL_EC_EXPLICIT_CURVE)
+        /* check that restoring the generator passes */
+        || !TEST_true(EC_GROUP_set_generator(tmpg, group_gen, group_order,
+                                             group_cofactor))
+        || !TEST_ptr(other_params = *p_next++ =
+                     EC_GROUP_get_ecparameters(tmpg, NULL))
+        || !TEST_ptr(tgroup = *g_next++ =
+                      EC_GROUP_new_from_ecparameters(other_params))
+        || !TEST_int_ne((tnid = EC_GROUP_get_curve_name(tgroup)), NID_undef)
+        || !TEST_true(are_ec_nids_compatible(nid, tnid))
+        || !TEST_int_eq(EC_GROUP_get_asn1_flag(tgroup),
+                        OPENSSL_EC_EXPLICIT_CURVE))
+        goto err;
+
+    ret = 1;
+err:
+    for (g_next = &g_ary[0]; g_next < g_ary + OSSL_NELEM(g_ary); g_next++)
+        EC_GROUP_free(*g_next);
+    for (p_next = &p_ary[0]; p_next < p_ary + OSSL_NELEM(g_ary); p_next++)
+        ECPARAMETERS_free(*p_next);
+    ECPARAMETERS_free(params);
+    EC_POINT_free(other_gen);
+    EC_GROUP_free(tmpg);
+    EC_GROUP_free(group);
+    BN_CTX_end(bn_ctx);
+    BN_CTX_free(bn_ctx);
+    return ret;
+}
+
 static int parameter_test(void)
 {
     EC_GROUP *group = NULL, *group2 = NULL;
@@ -1667,7 +1932,9 @@ int setup_tests(void)
 # endif
     ADD_ALL_TESTS(internal_curve_test, crv_len);
     ADD_ALL_TESTS(internal_curve_test_method, crv_len);
-#endif
+
+    ADD_ALL_TESTS(check_named_curve_from_ecparameters, crv_len);
+#endif /* OPENSSL_NO_EC */
     return 1;
 }