Ref #123: Define/Implement unlinkauth

Add an unlinkauth message type which removes a link from a message type
to a required authority

libraries/native_contract/eos_contract.cpp

@@ -378,7 +378,7 @@ void apply_eos_linkauth(apply_context& context) {
 
    if (link) {
       EOS_ASSERT(link->required_permission != requirement.requirement, message_precondition_exception,
-                 "Attempting to update required authority, but new requirement is same as old.");
+                 "Attempting to update required authority, but new requirement is same as old");
       db.modify(*link, [requirement = requirement.requirement](permission_link_object& link) {
          link.required_permission = requirement;
       });
@@ -392,5 +392,14 @@ void apply_eos_linkauth(apply_context& context) {
    }
 }
 
+void apply_eos_unlinkauth(apply_context& context) {
+   auto& db = context.mutable_db;
+   auto unlink = context.msg.as<types::unlinkauth>();
+   auto linkKey = boost::make_tuple(unlink.account, unlink.code, unlink.type);
+   auto link = db.find<permission_link_object, by_message_type>(linkKey);
+   EOS_ASSERT(link != nullptr, message_precondition_exception, "Attempting to unlink authority, but no link found");
+   db.remove(*link);
+}
+
 } // namespace eos
 } // namespace native

libraries/native_contract/include/eos/native_contract/eos_contract.hpp

@@ -19,6 +19,7 @@ void apply_eos_setproducer(chain::apply_context&);
 void apply_eos_setproxy(chain::apply_context&);
 void apply_eos_setcode(chain::apply_context&);
 void apply_eos_linkauth(chain::apply_context&);
+void apply_eos_unlinkauth(chain::apply_context&);
 
 } // namespace eos
 } // namespace native

libraries/native_contract/native_contract_chain_initializer.cpp

@@ -49,6 +49,7 @@ void native_contract_chain_initializer::register_types(chain_controller& chain,
    SET_APP_HANDLER( eos, eos, setproxy );
    SET_APP_HANDLER( eos, eos, setcode );
    SET_APP_HANDLER( eos, eos, linkauth );
+   SET_APP_HANDLER( eos, eos, unlinkauth );
 }
 
 std::vector<chain::Message> native_contract_chain_initializer::prepare_database(chain_controller& chain,

libraries/types/types.eos

@@ -131,3 +131,8 @@ struct linkauth
    code        AccountName # The contract to require permissions to invoke
    type        FuncName
    requirement PermissionName # The permission name to require
+
+struct unlinkauth
+   account     AccountName # The account to require permissions for
+   code        AccountName # The contract to require permissions to invoke
+   type        FuncName