EC_KEY: add EC_KEY_decoded_from_explicit_params()

The function returns 1 when the encoding of a decoded EC key used
explicit encoding of the curve parameters.

Reviewed-by: David von Oheimb <david.von.oheimb@siemens.com>
Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/12909)

8 files changed, 144 insertions, 9 deletions

diff --git a/crypto/ec/ec_asn1.c b/crypto/ec/ec_asn1.c
index 96e7d83ea7..7b7c75ce84 100644
--- a/crypto/ec/ec_asn1.c
+++ b/crypto/ec/ec_asn1.c
@@ -137,6 +137,12 @@ struct ec_parameters_st {
     ASN1_INTEGER *cofactor;
 } /* ECPARAMETERS */ ;
 
+typedef enum {
+    ECPKPARAMETERS_TYPE_NAMED = 0,
+    ECPKPARAMETERS_TYPE_EXPLICIT,
+    ECPKPARAMETERS_TYPE_IMPLICIT
+} ecpk_parameters_type_t;
+
 struct ecpk_parameters_st {
     int type;
     union {
@@ -535,9 +541,10 @@ ECPKPARAMETERS *EC_GROUP_get_ecpkparameters(const EC_GROUP *group,
             return NULL;
         }
     } else {
-        if (ret->type == 0)
+        if (ret->type == ECPKPARAMETERS_TYPE_NAMED)
             ASN1_OBJECT_free(ret->value.named_curve);
-        else if (ret->type == 1 && ret->value.parameters)
+        else if (ret->type == ECPKPARAMETERS_TYPE_EXPLICIT
+                 && ret->value.parameters != NULL)
             ECPARAMETERS_free(ret->value.parameters);
     }
 
@@ -554,7 +561,7 @@ ECPKPARAMETERS *EC_GROUP_get_ecpkparameters(const EC_GROUP *group,
                 ECerr(EC_F_EC_GROUP_GET_ECPKPARAMETERS, EC_R_MISSING_OID);
                 ok = 0;
             } else {
-                ret->type = 0;
+                ret->type = ECPKPARAMETERS_TYPE_NAMED;
                 ret->value.named_curve = asn1obj;
             }
         } else
@@ -562,7 +569,7 @@ ECPKPARAMETERS *EC_GROUP_get_ecpkparameters(const EC_GROUP *group,
             ok = 0;
     } else {
         /* use the ECPARAMETERS structure */
-        ret->type = 1;
+        ret->type = ECPKPARAMETERS_TYPE_EXPLICIT;
         if ((ret->value.parameters =
              EC_GROUP_get_ecparameters(group, NULL)) == NULL)
             ok = 0;
@@ -901,7 +908,8 @@ EC_GROUP *EC_GROUP_new_from_ecpkparameters(const ECPKPARAMETERS *params)
         return NULL;
     }
 
-    if (params->type == 0) {    /* the curve is given by an OID */
+    if (params->type == ECPKPARAMETERS_TYPE_NAMED) {
+        /* the curve is given by an OID */
         tmp = OBJ_obj2nid(params->value.named_curve);
         if ((ret = EC_GROUP_new_by_curve_name(tmp)) == NULL) {
             ECerr(EC_F_EC_GROUP_NEW_FROM_ECPKPARAMETERS,
@@ -909,15 +917,16 @@ EC_GROUP *EC_GROUP_new_from_ecpkparameters(const ECPKPARAMETERS *params)
             return NULL;
         }
         EC_GROUP_set_asn1_flag(ret, OPENSSL_EC_NAMED_CURVE);
-    } else if (params->type == 1) { /* the parameters are given by a
-                                     * ECPARAMETERS structure */
+    } else if (params->type == ECPKPARAMETERS_TYPE_EXPLICIT) {
+        /* the parameters are given by an ECPARAMETERS structure */
         ret = EC_GROUP_new_from_ecparameters(params->value.parameters);
         if (!ret) {
             ECerr(EC_F_EC_GROUP_NEW_FROM_ECPKPARAMETERS, ERR_R_EC_LIB);
             return NULL;
         }
         EC_GROUP_set_asn1_flag(ret, OPENSSL_EC_EXPLICIT_CURVE);
-    } else if (params->type == 2) { /* implicitlyCA */
+    } else if (params->type == ECPKPARAMETERS_TYPE_IMPLICIT) {
+        /* implicit parameters inherited from CA - unsupported */
         return NULL;
     } else {
         ECerr(EC_F_EC_GROUP_NEW_FROM_ECPKPARAMETERS, EC_R_ASN1_ERROR);
@@ -947,6 +956,9 @@ EC_GROUP *d2i_ECPKParameters(EC_GROUP **a, const unsigned char **in, long len)
         return NULL;
     }
 
+    if (params->type == ECPKPARAMETERS_TYPE_EXPLICIT)
+        group->decoded_from_explicit_params = 1;
+
     if (a) {
         EC_GROUP_free(*a);
         *a = group;
@@ -998,6 +1010,9 @@ EC_KEY *d2i_ECPrivateKey(EC_KEY **a, const unsigned char **in, long len)
     if (priv_key->parameters) {
         EC_GROUP_free(ret->group);
         ret->group = EC_GROUP_new_from_ecpkparameters(priv_key->parameters);
+        if (ret->group != NULL
+            && priv_key->parameters->type == ECPKPARAMETERS_TYPE_EXPLICIT)
+            ret->group->decoded_from_explicit_params = 1;
     }
 
     if (ret->group == NULL) {
diff --git a/crypto/ec/ec_key.c b/crypto/ec/ec_key.c
index 261087ce23..23efbd015c 100644
--- a/crypto/ec/ec_key.c
+++ b/crypto/ec/ec_key.c
@@ -564,6 +564,13 @@ void EC_KEY_clear_flags(EC_KEY *key, int flags)
     key->flags &= ~flags;
 }
 
+int EC_KEY_decoded_from_explicit_params(const EC_KEY *key)
+{
+    if (key == NULL || key->group == NULL)
+        return -1;
+    return key->group->decoded_from_explicit_params;
+}
+
 size_t EC_KEY_key2buf(const EC_KEY *key, point_conversion_form_t form,
                         unsigned char **pbuf, BN_CTX *ctx)
 {
diff --git a/crypto/ec/ec_lib.c b/crypto/ec/ec_lib.c
index 6832383cad..08db89fcee 100644
--- a/crypto/ec/ec_lib.c
+++ b/crypto/ec/ec_lib.c
@@ -211,6 +211,7 @@ int EC_GROUP_copy(EC_GROUP *dest, const EC_GROUP *src)
 
     dest->asn1_flag = src->asn1_flag;
     dest->asn1_form = src->asn1_form;
+    dest->decoded_from_explicit_params = src->decoded_from_explicit_params;
 
     if (src->seed) {
         OPENSSL_free(dest->seed);
diff --git a/crypto/ec/ec_local.h b/crypto/ec/ec_local.h
index e656fbd5e7..6ea26193e1 100644
--- a/crypto/ec/ec_local.h
+++ b/crypto/ec/ec_local.h
@@ -209,6 +209,8 @@ struct ec_group_st {
     BIGNUM *order, *cofactor;
     int curve_name;             /* optional NID for named curve */
     int asn1_flag;              /* flag to control the asn1 encoding */
+    int decoded_from_explicit_params; /* set if decoded from explicit
+                                       * curve parameters encoding */
     point_conversion_form_t asn1_form;
     unsigned char *seed;        /* optional seed for parameters (appears in
                                  * ASN1) */
diff --git a/doc/man3/EC_KEY_new.pod b/doc/man3/EC_KEY_new.pod
index 21663a032e..530979833d 100644
--- a/doc/man3/EC_KEY_new.pod
+++ b/doc/man3/EC_KEY_new.pod
@@ -9,7 +9,8 @@ EC_KEY_get0_engine,
 EC_KEY_get0_group, EC_KEY_set_group, EC_KEY_get0_private_key,
 EC_KEY_set_private_key, EC_KEY_get0_public_key, EC_KEY_set_public_key,
 EC_KEY_get_conv_form,
-EC_KEY_set_conv_form, EC_KEY_set_asn1_flag, EC_KEY_precompute_mult,
+EC_KEY_set_conv_form, EC_KEY_set_asn1_flag,
+EC_KEY_decoded_from_explicit_params, EC_KEY_precompute_mult,
 EC_KEY_generate_key, EC_KEY_check_key, EC_KEY_set_public_key_affine_coordinates,
 EC_KEY_oct2key, EC_KEY_key2buf, EC_KEY_oct2priv, EC_KEY_priv2oct,
 EC_KEY_priv2buf - Functions for creating, destroying and manipulating
@@ -38,6 +39,7 @@ EC_KEY objects
  point_conversion_form_t EC_KEY_get_conv_form(const EC_KEY *key);
  void EC_KEY_set_conv_form(EC_KEY *eckey, point_conversion_form_t cform);
  void EC_KEY_set_asn1_flag(EC_KEY *eckey, int asn1_flag);
+ int EC_KEY_decoded_from_explicit_params(const EC_KEY *key);
  int EC_KEY_precompute_mult(EC_KEY *key, BN_CTX *ctx);
  int EC_KEY_generate_key(EC_KEY *key);
  int EC_KEY_check_key(const EC_KEY *key);
@@ -118,6 +120,10 @@ EC_KEY_set_asn1_flag() sets the asn1_flag on the underlying EC_GROUP object
 (if set). Refer to L<EC_GROUP_copy(3)> for further information on the
 asn1_flag.
 
+EC_KEY_decoded_from_explicit_params() returns 1 if the group of the I<key> was
+decoded from data with explicitly encoded group parameters, -1 if the I<key>
+is NULL or the group parameters are missing, and 0 otherwise.
+
 EC_KEY_precompute_mult() stores multiples of the underlying EC_GROUP generator
 for faster point multiplication. See also L<EC_POINT_add(3)>.
 
diff --git a/include/openssl/ec.h b/include/openssl/ec.h
index 5af9ebdc7f..ca86ec15c5 100644
--- a/include/openssl/ec.h
+++ b/include/openssl/ec.h
@@ -829,6 +829,8 @@ void EC_KEY_set_flags(EC_KEY *key, int flags);
 
 void EC_KEY_clear_flags(EC_KEY *key, int flags);
 
+int EC_KEY_decoded_from_explicit_params(const EC_KEY *key);
+
 /** Creates a new EC_KEY object using a named curve as underlying
  *  EC_GROUP object.
  *  \param  nid  NID of the named curve.
diff --git a/test/ec_internal_test.c b/test/ec_internal_test.c
index 4b849312be..d1eede3a7f 100644
--- a/test/ec_internal_test.c
+++ b/test/ec_internal_test.c
@@ -183,6 +183,106 @@ static int field_tests_default(int n)
     return ret;
 }
 
+/*
+ * Tests behavior of the decoded_from_explicit_params flag and API
+ */
+static int decoded_flag_test(void)
+{
+    EC_GROUP *grp;
+    EC_GROUP *grp_copy = NULL;
+    ECPARAMETERS *ecparams = NULL;
+    ECPKPARAMETERS *ecpkparams = NULL;
+    EC_KEY *key = NULL;
+    unsigned char *encodedparams = NULL;
+    const unsigned char *encp;
+    int encodedlen;
+    int testresult = 0;
+
+    /* Test EC_GROUP_new not setting the flag */
+    grp = EC_GROUP_new(EC_GFp_simple_method());
+    if (!TEST_ptr(grp)
+        || !TEST_int_eq(grp->decoded_from_explicit_params, 0))
+        goto err;
+    EC_GROUP_free(grp);
+
+    /* Test EC_GROUP_new_by_curve_name not setting the flag */
+    grp = EC_GROUP_new_by_curve_name(NID_X9_62_prime256v1);
+    if (!TEST_ptr(grp)
+        || !TEST_int_eq(grp->decoded_from_explicit_params, 0))
+        goto err;
+
+    /* Test EC_GROUP_new_from_ecparameters not setting the flag */
+    if (!TEST_ptr(ecparams = EC_GROUP_get_ecparameters(grp, NULL))
+        || !TEST_ptr(grp_copy = EC_GROUP_new_from_ecparameters(ecparams))
+        || !TEST_int_eq(grp_copy->decoded_from_explicit_params, 0))
+        goto err;
+    EC_GROUP_free(grp_copy);
+    grp_copy = NULL;
+    ECPARAMETERS_free(ecparams);
+    ecparams = NULL;
+
+    /* Test EC_GROUP_new_from_ecpkparameters not setting the flag */
+    if (!TEST_int_eq(EC_GROUP_get_asn1_flag(grp), OPENSSL_EC_NAMED_CURVE)
+        || !TEST_ptr(ecpkparams = EC_GROUP_get_ecpkparameters(grp, NULL))
+        || !TEST_ptr(grp_copy = EC_GROUP_new_from_ecpkparameters(ecpkparams))
+        || !TEST_int_eq(grp_copy->decoded_from_explicit_params, 0)
+        || !TEST_ptr(key = EC_KEY_new())
+    /* Test EC_KEY_decoded_from_explicit_params on key without a group */
+        || !TEST_int_eq(EC_KEY_decoded_from_explicit_params(key), -1)
+        || !TEST_int_eq(EC_KEY_set_group(key, grp_copy), 1)
+    /* Test EC_KEY_decoded_from_explicit_params negative case */
+        || !TEST_int_eq(EC_KEY_decoded_from_explicit_params(key), 0))
+        goto err;
+    EC_GROUP_free(grp_copy);
+    grp_copy = NULL;
+    ECPKPARAMETERS_free(ecpkparams);
+    ecpkparams = NULL;
+
+    /* Test d2i_ECPKParameters with named params not setting the flag */
+    if (!TEST_int_gt(encodedlen = i2d_ECPKParameters(grp, &encodedparams), 0)
+        || !TEST_ptr(encp = encodedparams)
+        || !TEST_ptr(grp_copy = d2i_ECPKParameters(NULL, &encp, encodedlen))
+        || !TEST_int_eq(grp_copy->decoded_from_explicit_params, 0))
+        goto err;
+    EC_GROUP_free(grp_copy);
+    grp_copy = NULL;
+    OPENSSL_free(encodedparams);
+    encodedparams = NULL;
+
+    /* Asn1 flag stays set to explicit with EC_GROUP_new_from_ecpkparameters */
+    EC_GROUP_set_asn1_flag(grp, OPENSSL_EC_EXPLICIT_CURVE);
+    if (!TEST_ptr(ecpkparams = EC_GROUP_get_ecpkparameters(grp, NULL))
+        || !TEST_ptr(grp_copy = EC_GROUP_new_from_ecpkparameters(ecpkparams))
+        || !TEST_int_eq(EC_GROUP_get_asn1_flag(grp_copy), OPENSSL_EC_EXPLICIT_CURVE)
+        || !TEST_int_eq(grp_copy->decoded_from_explicit_params, 0))
+        goto err;
+    EC_GROUP_free(grp_copy);
+    grp_copy = NULL;
+
+    /* Test d2i_ECPKParameters with explicit params setting the flag */
+    if (!TEST_int_gt(encodedlen = i2d_ECPKParameters(grp, &encodedparams), 0)
+        || !TEST_ptr(encp = encodedparams)
+        || !TEST_ptr(grp_copy = d2i_ECPKParameters(NULL, &encp, encodedlen))
+        || !TEST_int_eq(EC_GROUP_get_asn1_flag(grp_copy), OPENSSL_EC_EXPLICIT_CURVE)
+        || !TEST_int_eq(grp_copy->decoded_from_explicit_params, 1)
+        || !TEST_int_eq(EC_KEY_set_group(key, grp_copy), 1)
+    /* Test EC_KEY_decoded_from_explicit_params positive case */
+        || !TEST_int_eq(EC_KEY_decoded_from_explicit_params(key), 1))
+        goto err;
+
+    testresult = 1;
+
+ err:
+    EC_KEY_free(key);
+    EC_GROUP_free(grp);
+    EC_GROUP_free(grp_copy);
+    ECPARAMETERS_free(ecparams);
+    ECPKPARAMETERS_free(ecpkparams);
+    OPENSSL_free(encodedparams);
+
+    return testresult;
+}
+
 int setup_tests(void)
 {
     crv_len = EC_get_builtin_curves(NULL, 0);
@@ -196,6 +296,7 @@ int setup_tests(void)
     ADD_TEST(field_tests_ec2_simple);
 #endif
     ADD_ALL_TESTS(field_tests_default, crv_len);
+    ADD_TEST(decoded_flag_test);
     return 1;
 }
 
diff --git a/util/libcrypto.num b/util/libcrypto.num
index e16b836eb2..436f799bca 100644
--- a/util/libcrypto.num
+++ b/util/libcrypto.num
@@ -4590,3 +4590,4 @@ RSA_get0_pss_params                     4543	1_1_1e	EXIST::FUNCTION:RSA
 X509_ALGOR_copy                         4544	1_1_1h	EXIST::FUNCTION:
 X509_REQ_set0_signature                 4545	1_1_1h	EXIST::FUNCTION:
 X509_REQ_set1_signature_algo            4546	1_1_1h	EXIST::FUNCTION:
+EC_KEY_decoded_from_explicit_params     4547	1_1_1h	EXIST::FUNCTION:EC