feat: impl check reject transfer if len(hops) > 0 and ics20-1 (#6675)

* impl check reject transfer if len(hops) > 0 and ics20-1

* add test case hops is not empty with ics20-2

* address review comments

* reorder variable declaration

---------

Co-authored-by: Carlos Rodriguez <carlos@interchain.io>
Co-authored-by: Gjermund Garaba <bjaanes@gmail.com>

modules/apps/transfer/keeper/relay.go

@@ -76,9 +76,16 @@ func (k Keeper) sendTransfer(
 		return 0, errorsmod.Wrapf(ibcerrors.ErrInvalidRequest, "application version not found for source port: %s and source channel: %s", sourcePort, sourceChannel)
 	}
 
-	// ics20-1 only supports a single coin, so if that is the current version, we must only process a single coin.
-	if appVersion == types.V1 && len(coins) > 1 {
-		return 0, errorsmod.Wrapf(ibcerrors.ErrInvalidRequest, "cannot transfer multiple coins with ics20-1")
+	if appVersion == types.V1 {
+		// ics20-1 only supports a single coin, so if that is the current version, we must only process a single coin.
+		if len(coins) > 1 {
+			return 0, errorsmod.Wrapf(ibcerrors.ErrInvalidRequest, "cannot transfer multiple coins with %s", types.V1)
+		}
+
+		// ics20-1 does not support forwarding, so if that is the current version, we must reject the transfer.
+		if len(forwarding.Hops) > 0 {
+			return 0, errorsmod.Wrapf(ibcerrors.ErrInvalidRequest, "cannot forward coins with %s", types.V1)
+		}
 	}
 
 	destinationPort := channel.Counterparty.PortId

modules/apps/transfer/keeper/relay_test.go

@@ -35,8 +35,8 @@ func (suite *KeeperTestSuite) TestSendTransfer() {
 		sender          sdk.AccAddress
 		timeoutHeight   clienttypes.Height
 		memo            string
+		forwarding      types.Forwarding
 		expEscrowAmount sdkmath.Int // total amount in escrow for denom on receiving chain
-
 	)
 
 	testCases := []struct {
@@ -80,6 +80,29 @@ func (suite *KeeperTestSuite) TestSendTransfer() {
 			},
 			nil,
 		},
+		{
+			"successful transfer with empty forwarding hops and ics20-1",
+			func() {
+				expEscrowAmount = sdkmath.NewInt(100)
+
+				// Set version to isc20-1.
+				path.EndpointA.UpdateChannel(func(channel *channeltypes.Channel) {
+					channel.Version = types.V1
+				})
+			},
+			nil,
+		},
+		{
+			"successful transfer with non-empty forwarding hops and ics20-2",
+			func() {
+				expEscrowAmount = sdkmath.NewInt(100)
+				forwarding = types.NewForwarding(false, types.Hop{
+					PortId:    path.EndpointA.ChannelConfig.PortID,
+					ChannelId: path.EndpointA.ChannelID,
+				})
+			},
+			nil,
+		},
 		{
 			"successful transfer of IBC token with memo",
 			func() {
@@ -146,6 +169,21 @@ func (suite *KeeperTestSuite) TestSendTransfer() {
 			},
 			channeltypes.ErrInvalidPacket,
 		},
+		{
+			"failure: forwarding hops is not empty with ics20-1",
+			func() {
+				// Set version to isc20-1.
+				path.EndpointA.UpdateChannel(func(channel *channeltypes.Channel) {
+					channel.Version = types.V1
+				})
+
+				forwarding = types.NewForwarding(false, types.Hop{
+					PortId:    path.EndpointA.ChannelConfig.PortID,
+					ChannelId: path.EndpointA.ChannelID,
+				})
+			},
+			ibcerrors.ErrInvalidRequest,
+		},
 	}
 
 	for _, tc := range testCases {
@@ -162,6 +200,7 @@ func (suite *KeeperTestSuite) TestSendTransfer() {
 			memo = ""
 			timeoutHeight = suite.chainB.GetTimeoutHeight()
 			expEscrowAmount = sdkmath.ZeroInt()
+			forwarding = emptyForwarding
 
 			// create IBC token on chainA
 			transferMsg := types.NewMsgTransfer(path.EndpointB.ChannelConfig.PortID, path.EndpointB.ChannelID, sdk.NewCoins(coin), suite.chainB.SenderAccount.GetAddress().String(), suite.chainA.SenderAccount.GetAddress().String(), suite.chainA.GetTimeoutHeight(), 0, "", emptyForwarding)
@@ -184,7 +223,7 @@ func (suite *KeeperTestSuite) TestSendTransfer() {
 				suite.chainB.SenderAccount.GetAddress().String(),
 				timeoutHeight, 0, // only use timeout height
 				memo,
-				emptyForwarding,
+				forwarding,
 			)
 
 			res, err := suite.chainA.GetSimApp().TransferKeeper.Transfer(suite.chainA.GetContext(), msg)