fix: noop on UpdateState for invalid misbehaviour (#6276)

* fix: noop on UpdateState for invalid misbehaviour

* godoc: update godoc for UpdateState

* Update modules/light-clients/07-tendermint/update.go

Co-authored-by: colin axnér <25233464+colin-axner@users.noreply.github.com>

* chore: add changelog

---------

Co-authored-by: colin axnér <25233464+colin-axner@users.noreply.github.com>
Co-authored-by: Carlos Rodriguez <carlos@interchain.io>

CHANGELOG.md

@@ -55,6 +55,8 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### State Machine Breaking
 
+* (light-clients/07-tendermint) Fix: No-op to avoid panicking on `UpdateState` for invalid misbehaviour submissions.
+
 ### Improvements
 
 * (apps/27-interchain-accounts) [\#5533](https://github.com/cosmos/ibc-go/pull/5533) ICA host sets the host connection ID on `OnChanOpenTry`, so that ICA controller implementations are not obliged to set the value on `OnChanOpenInit` if they are not able.

modules/light-clients/07-tendermint/update.go

@@ -131,10 +131,12 @@ func (cs *ClientState) verifyHeader(
 // UpdateState must only be used to update within a single revision, thus header revision number and trusted height's revision
 // number must be the same. To update to a new revision, use a separate upgrade path
 // UpdateState will prune the oldest consensus state if it is expired.
+// If the provided clientMsg is not of type of Header then the handler will noop and empty slice is returned.
 func (cs ClientState) UpdateState(ctx sdk.Context, cdc codec.BinaryCodec, clientStore storetypes.KVStore, clientMsg exported.ClientMessage) []exported.Height {
 	header, ok := clientMsg.(*Header)
 	if !ok {
-		panic(fmt.Errorf("expected type %T, got %T", &Header{}, clientMsg))
+		// clientMsg is invalid Misbehaviour, no update necessary
+		return []exported.Height{}
 	}
 
 	cs.pruneOldestConsensusState(ctx, cdc, clientStore)

modules/light-clients/07-tendermint/update_test.go

@@ -546,9 +546,12 @@ func (suite *TendermintTestSuite) TestUpdateState() {
 				suite.Require().Equal(expConsensusState, updatedConsensusState)
 
 			} else {
-				suite.Require().Panics(func() {
-					clientState.UpdateState(suite.chainA.GetContext(), suite.chainA.App.AppCodec(), clientStore, clientMessage)
-				})
+				consensusHeights = clientState.UpdateState(suite.chainA.GetContext(), suite.chainA.App.AppCodec(), clientStore, clientMessage)
+				suite.Require().Empty(consensusHeights)
+
+				consensusState, found := suite.chainA.GetSimApp().GetIBCKeeper().ClientKeeper.GetClientConsensusState(suite.chainA.GetContext(), path.EndpointA.ClientID, clienttypes.NewHeight(1, uint64(suite.chainB.GetContext().BlockHeight())))
+				suite.Require().False(found)
+				suite.Require().Nil(consensusState)
 			}
 
 			// perform custom checks