fix(state!): check upgrade compatibility in channel upgrade confirm (backport #6935)

CHANGELOG.md

@@ -50,6 +50,8 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Bug Fixes
 
+* (core/04-channel) [\#6935](https://github.com/cosmos/ibc-go/pull/6935) Check upgrade compatibility in `ChanUpgradeConfirm`.
+
 ## [v8.3.2](https://github.com/cosmos/ibc-go/releases/tag/v8.3.2) - 2024-06-20
 
 ### Dependencies

modules/core/04-channel/keeper/upgrade.go

@@ -448,6 +448,21 @@ func (k Keeper) ChanUpgradeConfirm(
 		return errorsmod.Wrap(err, "failed to verify counterparty upgrade")
 	}
 
+	// if we have cancelled our upgrade after performing UpgradeInit,
+	// UpgradeTry or UpgradeAck, the lack of a stored upgrade will prevent
+	// us from continuing the upgrade handshake
+	upgrade, found := k.GetUpgrade(ctx, portID, channelID)
+	if !found {
+		return errorsmod.Wrapf(types.ErrUpgradeNotFound, "failed to retrieve channel upgrade: port ID (%s) channel ID (%s)", portID, channelID)
+	}
+
+	// in the crossing-hello case it is possible that both chains execute the
+	// INIT, TRY and CONFIRM steps without any of them executing ACK, therefore
+	// we also need to check that the upgrades are compatible on this step
+	if err := k.checkForUpgradeCompatibility(ctx, upgrade.Fields, counterpartyUpgrade.Fields); err != nil {
+		return types.NewUpgradeError(channel.UpgradeSequence, err)
+	}
+
 	timeout := counterpartyUpgrade.Timeout
 	selfHeight, selfTimestamp := clienttypes.GetSelfHeight(ctx), uint64(ctx.BlockTime().UnixNano())
 

modules/core/04-channel/keeper/upgrade_test.go

@@ -1124,6 +1124,27 @@ func (suite *KeeperTestSuite) TestChanUpgradeConfirm() {
 			},
 			types.NewUpgradeError(1, types.ErrTimeoutElapsed),
 		},
+		{
+			"upgrade not found",
+			func() {
+				path.EndpointB.Chain.DeleteKey(host.ChannelUpgradeKey(path.EndpointB.ChannelConfig.PortID, path.EndpointB.ChannelID))
+			},
+			types.ErrUpgradeNotFound,
+		},
+		{
+			"upgrades are not compatible",
+			func() {
+				// the expected upgrade version is mock-version-v2
+				counterpartyUpgrade.Fields.Version = fmt.Sprintf("%s-v3", mock.Version)
+				path.EndpointA.SetChannelUpgrade(counterpartyUpgrade)
+
+				suite.coordinator.CommitBlock(suite.chainA)
+
+				err := path.EndpointB.UpdateClient()
+				suite.Require().NoError(err)
+			},
+			types.NewUpgradeError(1, types.ErrIncompatibleCounterpartyUpgrade),
+		},
 	}
 
 	for _, tc := range testCases {