objects: Fix EdDSA key comparison

When we import the EdDSA key from file, we always use the printable
string choice in the EC_PARAMS. But the key on token can use OID
in which case, we will not be able to match these two keys.

Previously, the fallback involved getting the EC_GROUP from the
EC_PARAMS, but this really works only with the ECDSA keys. On EdDSA
keys, we always fail as the EdDSA keys do not have any EC_GROUP defined
in OpenSSL and there is no conversion from the EC_PARAMS that contain
printable string so the matching needs to be done differently than with
the ECDSA keys.

Previously, this worked because the Ed25519 keys we used had always
representation with printable string so we were able to match the
EC_PARAM strings byte-by-byte.

Signed-off-by: Jakub Jelen <[email protected]>

src/objects.c

@@ -2477,6 +2477,31 @@ static int match_public_keys(P11PROV_OBJ *key1, P11PROV_OBJ *key2)
     return ret;
 }
 
+static int p11prov_obj_get_ed_nid(CK_ATTRIBUTE *ecp)
+{
+    const unsigned char *val = ecp->pValue;
+    ASN1_OBJECT *obj = d2i_ASN1_OBJECT(NULL, &val, ecp->ulValueLen);
+    if (obj) {
+        int nid = OBJ_obj2nid(obj);
+        ASN1_OBJECT_free(obj);
+        if (nid != NID_undef) {
+            return nid;
+        }
+    }
+
+    /* it might be the parameters are encoded printable string
+     * for EdDSA which OpenSSL does not understand */
+    if (ecp->ulValueLen == ED25519_EC_PARAMS_LEN
+        && memcmp(ecp->pValue, ed25519_ec_params, ED25519_EC_PARAMS_LEN) == 0) {
+        return NID_ED25519;
+    } else if (ecp->ulValueLen == ED448_EC_PARAMS_LEN
+               && memcmp(ecp->pValue, ed448_ec_params, ED448_EC_PARAMS_LEN)
+                      == 0) {
+        return NID_ED448;
+    }
+    return NID_undef;
+}
+
 int p11prov_obj_key_cmp(P11PROV_OBJ *key1, P11PROV_OBJ *key2, CK_KEY_TYPE type,
                         int cmp_type)
 {
@@ -2535,7 +2560,6 @@ int p11prov_obj_key_cmp(P11PROV_OBJ *key1, P11PROV_OBJ *key2, CK_KEY_TYPE type,
         break;
 
     case CKK_EC:
-    case CKK_EC_EDWARDS:
         ret = cmp_attr(key1, key2, CKA_EC_PARAMS);
         if (ret != RET_OSSL_OK) {
             /* If EC_PARAMS do not match it may be due to encoding.
@@ -2604,6 +2628,50 @@ int p11prov_obj_key_cmp(P11PROV_OBJ *key1, P11PROV_OBJ *key2, CK_KEY_TYPE type,
             cmp_type = OBJ_CMP_KEY_PUBLIC;
         }
         break;
+    case CKK_EC_EDWARDS:
+        /* The EdDSA params can be encoded as printable string, which is
+         * not recognized by OpenSSL and does not have respective EC_GROUP */
+        ret = cmp_attr(key1, key2, CKA_EC_PARAMS);
+        if (ret != RET_OSSL_OK) {
+            /* If EC_PARAMS do not match it may be due to encoding. */
+            CK_ATTRIBUTE *ec_p;
+            int nid1;
+            int nid2;
+
+            ec_p = p11prov_obj_get_attr(key1, CKA_EC_PARAMS);
+            if (!ec_p) {
+                return RET_OSSL_ERR;
+            }
+            nid1 = p11prov_obj_get_ed_nid(ec_p);
+            if (nid1 == NID_undef) {
+                return RET_OSSL_ERR;
+            }
+
+            ec_p = p11prov_obj_get_attr(key2, CKA_EC_PARAMS);
+            if (!ec_p) {
+                return RET_OSSL_ERR;
+            }
+            nid2 = p11prov_obj_get_ed_nid(ec_p);
+            if (nid2 == NID_undef) {
+                return RET_OSSL_ERR;
+            }
+            if (nid1 != nid2) {
+                return RET_OSSL_ERR;
+            }
+        }
+        if (cmp_type & OBJ_CMP_KEY_PRIVATE) {
+            /* unfortunately we can't really read private attributes
+             * and there is no comparison function int he PKCS11 API.
+             * Generally you do not have 2 identical keys stored in to two
+             * separate objects so the initial shortcircuit that matches if
+             * slotid/handle are identical will often cover this. When that
+             * fails we have no option but to fail for now. */
+            P11PROV_debug("We can't really match private keys");
+            /* OTOH if group and pub point match either this is a broken key
+             * or the private key must also match */
+            cmp_type = OBJ_CMP_KEY_PUBLIC;
+        }
+        break;
 
     default:
         return RET_OSSL_ERR;