From 2b53d717084d589cf0ddaa8064c4db9ac3c249cf Mon Sep 17 00:00:00 2001
From: Mykhailo Prakhov <117639195+mprakhov@users.noreply.github.com>
Date: Fri, 22 Sep 2023 19:57:27 +0200
Subject: [PATCH] fix: Prevent (reject event <-> resend event) loop (#4055)

---
 protocol/communities/manager.go              | 17 ++++++
 protocol/communities_messenger_admin_test.go | 59 ++++++++++++++++++++
 2 files changed, 76 insertions(+)

diff --git a/protocol/communities/manager.go b/protocol/communities/manager.go
index e6f24e3f4..eed470e9d 100644
--- a/protocol/communities/manager.go
+++ b/protocol/communities/manager.go
@@ -1425,6 +1425,8 @@ func (m *Manager) HandleCommunityEventsMessage(signer *ecdsa.PublicKey, message
 	err = community.UpdateCommunityByEvents(eventsMessage)
 	if err != nil {
 		if err == ErrInvalidCommunityEventClock && community.IsControlNode() {
+			// send updated CommunityDescription to the event sender on top of which he must apply his changes
+			eventsMessage.EventsBaseCommunityDescription = community.config.CommunityDescriptionProtocolMessage
 			m.publish(&Subscription{
 				CommunityEventsMessageInvalidClock: &CommunityEventsMessageInvalidClockSignal{
 					Community:              community,
@@ -1491,6 +1493,17 @@ func (m *Manager) HandleCommunityEventsMessageRejected(signer *ecdsa.PublicKey,
 	if err != nil {
 		return nil, err
 	}
+
+	communityDescription, err := validateAndGetEventsMessageCommunityDescription(eventsMessage.EventsBaseCommunityDescription, signer)
+	if err != nil {
+		return nil, err
+	}
+	// the privileged member did not receive updated CommunityDescription so his events
+	// will be send on top of outdated CommunityDescription
+	if communityDescription.Clock != community.Clock() {
+		return nil, errors.New("resend rejected community events aborted, client node has outdated community description")
+	}
+
 	eventsMessage.Events = m.validateAndFilterEvents(community, eventsMessage.Events)
 
 	myRejectedEvents := make([]CommunityEvent, 0)
@@ -4813,3 +4826,7 @@ func (m *Manager) shareAcceptedRequestToJoinWithPrivilegedMembers(community *Com
 func (m *Manager) GetCommunityRequestsToJoinWithRevealedAddresses(communityID types.HexBytes) ([]*RequestToJoin, error) {
 	return m.persistence.GetCommunityRequestsToJoinWithRevealedAddresses(communityID)
 }
+
+func (m *Manager) SaveCommunity(community *Community) error {
+	return m.persistence.SaveCommunity(community)
+}
diff --git a/protocol/communities_messenger_admin_test.go b/protocol/communities_messenger_admin_test.go
index 936cf089c..fbd1d3429 100644
--- a/protocol/communities_messenger_admin_test.go
+++ b/protocol/communities_messenger_admin_test.go
@@ -381,3 +381,62 @@ func (s *AdminCommunityEventsSuite) TestReceiveRequestsToJoinWithRevealedAccount
 	bob := s.newMessenger(accountPassword, []string{bobAccountAddress})
 	testMemberReceiveRequestsToJoinAfterGettingNewRole(s, bob, protobuf.CommunityTokenPermission_BECOME_ADMIN)
 }
+
+func (s *AdminCommunityEventsSuite) TestAdminDoesNotHaveRejectedEventsLoop() {
+	community := setUpCommunityAndRoles(s, protobuf.CommunityMember_ROLE_ADMIN)
+
+	// admin modifies community description
+	adminEditRequest := &requests.EditCommunity{
+		CommunityID: community.ID(),
+		CreateCommunity: requests.CreateCommunity{
+			Name:        "admin name",
+			Description: "admin description",
+			Color:       "#FFFFFF",
+			Membership:  protobuf.CommunityPermissions_ON_REQUEST,
+		},
+	}
+	_, err := s.admin.EditCommunity(adminEditRequest)
+	s.Require().NoError(err)
+
+	community, err = s.owner.communitiesManager.GetByID(community.ID())
+	s.Require().NoError(err)
+
+	// Update community clock without publishing new CommunityDescription
+	err = community.DeclineRequestToJoin(nil)
+	s.Require().NoError(err)
+
+	err = s.owner.communitiesManager.SaveCommunity(community)
+	s.Require().NoError(err)
+
+	waitOnAdminEventsRejection := waitOnCommunitiesEvent(s.owner, func(s *communities.Subscription) bool {
+		return s.CommunityEventsMessageInvalidClock != nil
+	})
+
+	// control node receives admin event and rejects it
+	_, err = WaitOnMessengerResponse(s.owner, func(response *MessengerResponse) bool {
+		select {
+		case err := <-waitOnAdminEventsRejection:
+			s.Require().NoError(err)
+			return true
+		default:
+			return false
+		}
+	}, "")
+	s.Require().NoError(err)
+
+	community, err = s.owner.communitiesManager.GetByID(community.ID())
+	s.Require().NoError(err)
+	s.Require().NotEqual(adminEditRequest.Description, community.DescriptionText())
+
+	// admin receives rejected events and re-applies them
+	// there is no signal whatsoever, we just wait for admin to process all incoming messages
+	_, _ = WaitOnMessengerResponse(s.admin, func(response *MessengerResponse) bool {
+		return false
+	}, "")
+
+	// control node does not receives admin event
+	_, err = WaitOnMessengerResponse(s.owner, func(response *MessengerResponse) bool {
+		return len(response.Communities()) > 0
+	}, "no communities in response")
+	s.Require().Error(err)
+}