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)

4 files changed, 33 insertions, 8 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) */