add doc

tests/integration/misbehaviour.go

@@ -94,6 +94,7 @@ func (s *CCVTestSuite) TestGetByzantineValidators() {
 	altSigners[clientTMValset.Validators[1].Address.String()] = clientSigners[clientTMValset.Validators[1].Address.String()]
 	altSigners[clientTMValset.Validators[2].Address.String()] = clientSigners[clientTMValset.Validators[2].Address.String()]
 
+	// create a consumer client header
 	clientHeader := s.consumerChain.CreateTMClientHeader(
 		s.consumerChain.ChainID,
 		int64(clientHeight.RevisionHeight+1),
@@ -105,7 +106,6 @@ func (s *CCVTestSuite) TestGetByzantineValidators() {
 		clientSigners,
 	)
 
-	// TODO: figure out how to test an amnesia cases for "amnesia" attack
 	testCases := []struct {
 		name                   string
 		getMisbehaviour        func() *ibctmtypes.Misbehaviour
@@ -160,13 +160,12 @@ func (s *CCVTestSuite) TestGetByzantineValidators() {
 			true,
 		},
 		{
-			"valid light client attack - equivocation",
+			"light client attack - equivocation",
 			func() *ibctmtypes.Misbehaviour {
 				return &ibctmtypes.Misbehaviour{
 					ClientId: s.path.EndpointA.ClientID,
 					Header1:  clientHeader,
-					// the resulting header contains invalid fields
-					// i.e. ValidatorsHash, NextValidatorsHash etc.
+					// the resulting header contains a different BlockID
 					Header2: s.consumerChain.CreateTMClientHeader(
 						s.consumerChain.ChainID,
 						int64(clientHeight.RevisionHeight+1),
@@ -185,7 +184,7 @@ func (s *CCVTestSuite) TestGetByzantineValidators() {
 			true,
 		},
 		{
-			"valid light client attack - amnesia",
+			"light client attack - amnesia",
 			func() *ibctmtypes.Misbehaviour {
 				// create a valid header with a different hash
 				// and commit round

x/ccv/provider/keeper/misbehaviour.go

@@ -1,6 +1,7 @@
 package keeper
 
 import (
+	"bytes"
 	"fmt"
 
 	"github.com/cosmos/interchain-security/v2/x/ccv/provider/types"
@@ -88,11 +89,11 @@ func (k Keeper) GetByzantineValidators(ctx sdk.Context, misbehaviour ibctmtypes.
 
 	// Check if the misbehaviour corresponds to an Amnesia attack,
 	// meaning that the conflicting headers have both valid state transitions
-	// and different commit rounds. In this case, we return no validators as we can't identify the byzantine validators.
+	// and different commit rounds. In this case, we return no validators as
+	// we can't identify the byzantine validators.
 	//
-	// Note that we cannot differentiate which of the headers is trusted or malicious.
-	ev := &tmtypes.LightClientAttackEvidence{ConflictingBlock: lightBlock1}
-	if !ev.ConflictingHeaderIsInvalid(lightBlock2.Header) && lightBlock1.Commit.Round != lightBlock2.Commit.Round {
+	// Note that we cannot differentiate which of the headers is trusted or malicious,
+	if !headersStateTransitionsAreConflicting(*lightBlock1.Header, *lightBlock2.Header) && lightBlock1.Commit.Round != lightBlock2.Commit.Round {
 		return
 	}
 
@@ -168,3 +169,14 @@ func (k Keeper) CheckMisbehaviour(ctx sdk.Context, misbehaviour ibctmtypes.Misbe
 
 	return nil
 }
+
+// Check if the given block headers have conflicting state transitions.
+// Note that this method was copied from ConflictingHeaderIsInvalid in CometBFT,
+// see https://github.com/cometbft/cometbft/blob/v0.34.27/types/evidence.go#L285
+func headersStateTransitionsAreConflicting(h1, h2 tmtypes.Header) bool {
+	return !bytes.Equal(h1.ValidatorsHash, h2.ValidatorsHash) ||
+		!bytes.Equal(h1.NextValidatorsHash, h2.NextValidatorsHash) ||
+		!bytes.Equal(h1.ConsensusHash, h2.ConsensusHash) ||
+		!bytes.Equal(h1.AppHash, h2.AppHash) ||
+		!bytes.Equal(h1.LastResultsHash, h2.LastResultsHash)
+}