feat: adding ConsensusHost interface for custom self client/consens…

…us state validation (backport #6055) (#6547)

* feat: adding `ConsensusHost` interface for custom self client/consensus state validation (#6055)

Co-authored-by: chatton <github.qpeyb@simplelogin.fr>
(cherry picked from commit 50d2a08)

# Conflicts:
#	CHANGELOG.md
#	modules/core/02-client/keeper/keeper.go
#	modules/core/02-client/keeper/keeper_test.go
#	modules/core/02-client/types/errors.go

* restore changes from release/v8.3.x

* chore: update changelog

---------

Co-authored-by: Damian Nolan <damiannolan@gmail.com>

modules/light-clients/08-wasm/CHANGELOG.md

@@ -44,10 +44,12 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Improvements
 
-* [\#5923](https://github.com/cosmos/ibc-go/pull/5923) imp: adding 08-wasm build opts for libwasmvm linking disabled 
+* [\#5923](https://github.com/cosmos/ibc-go/pull/5923) imp: add 08-wasm build opts for libwasmvm linking disabled 
 
 ### Features
 
+* [\#6055](https://github.com/cosmos/ibc-go/pull/6055) feat: add 08-wasm `ConsensusHost` implementation for custom self client/consensus state validation in 03-connection handshake.
+
 ### Bug Fixes
 
 <!-- markdown-link-check-disable-next-line -->

modules/light-clients/08-wasm/testing/simapp/app.go

@@ -418,6 +418,7 @@ func NewSimApp(
 	app.IBCKeeper = ibckeeper.NewKeeper(
 		appCodec, keys[ibcexported.StoreKey], app.GetSubspace(ibcexported.ModuleName), app.StakingKeeper, app.UpgradeKeeper, scopedIBCKeeper, authtypes.NewModuleAddress(govtypes.ModuleName).String(),
 	)
+
 	// Register the proposal types
 	// Deprecated: Avoid adding new handlers, instead use the new proposal flow
 	// by granting the governance module the right to execute the message.

modules/light-clients/08-wasm/types/consensus_host.go

@@ -0,0 +1,77 @@
+package types
+
+import (
+	"fmt"
+
+	errorsmod "cosmossdk.io/errors"
+
+	"github.com/cosmos/cosmos-sdk/codec"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+
+	clienttypes "github.com/cosmos/ibc-go/v8/modules/core/02-client/types"
+	"github.com/cosmos/ibc-go/v8/modules/core/exported"
+)
+
+// WasmConsensusHost implements the 02-client types.ConsensusHost interface.
+type WasmConsensusHost struct {
+	cdc      codec.BinaryCodec
+	delegate clienttypes.ConsensusHost
+}
+
+var _ clienttypes.ConsensusHost = (*WasmConsensusHost)(nil)
+
+// NewWasmConsensusHost creates and returns a new ConsensusHost for wasm wrapped consensus client state and consensus state self validation.
+func NewWasmConsensusHost(cdc codec.BinaryCodec, delegate clienttypes.ConsensusHost) (*WasmConsensusHost, error) {
+	if cdc == nil {
+		return nil, fmt.Errorf("wasm consensus host codec is nil")
+	}
+
+	if delegate == nil {
+		return nil, fmt.Errorf("wasm delegate consensus host is nil")
+	}
+
+	return &WasmConsensusHost{
+		cdc:      cdc,
+		delegate: delegate,
+	}, nil
+}
+
+// GetSelfConsensusState implements the 02-client types.ConsensusHost interface.
+func (w *WasmConsensusHost) GetSelfConsensusState(ctx sdk.Context, height exported.Height) (exported.ConsensusState, error) {
+	consensusState, err := w.delegate.GetSelfConsensusState(ctx, height)
+	if err != nil {
+		return nil, err
+	}
+
+	// encode consensusState to wasm.ConsensusState.Data
+	bz, err := w.cdc.MarshalInterface(consensusState)
+	if err != nil {
+		return nil, err
+	}
+
+	wasmConsensusState := &ConsensusState{
+		Data: bz,
+	}
+
+	return wasmConsensusState, nil
+}
+
+// ValidateSelfClient implements the 02-client types.ConsensusHost interface.
+func (w *WasmConsensusHost) ValidateSelfClient(ctx sdk.Context, clientState exported.ClientState) error {
+	wasmClientState, ok := clientState.(*ClientState)
+	if !ok {
+		return errorsmod.Wrapf(clienttypes.ErrInvalidClient, "client must be a wasm client, expected: %T, got: %T", ClientState{}, wasmClientState)
+	}
+
+	if wasmClientState.Data == nil {
+		return errorsmod.Wrapf(clienttypes.ErrInvalidClient, "wasm client state data is nil")
+	}
+
+	// unmarshal the wasmClientState bytes into the ClientState interface and call self validation
+	var unwrappedClientState exported.ClientState
+	if err := w.cdc.UnmarshalInterface(wasmClientState.Data, &unwrappedClientState); err != nil {
+		return err
+	}
+
+	return w.delegate.ValidateSelfClient(ctx, unwrappedClientState)
+}

modules/light-clients/08-wasm/types/consensus_host_test.go

@@ -0,0 +1,151 @@
+package types_test
+
+import (
+	sdk "github.com/cosmos/cosmos-sdk/types"
+
+	wasmtesting "github.com/cosmos/ibc-go/modules/light-clients/08-wasm/testing"
+	"github.com/cosmos/ibc-go/modules/light-clients/08-wasm/types"
+	clienttypes "github.com/cosmos/ibc-go/v8/modules/core/02-client/types"
+	"github.com/cosmos/ibc-go/v8/modules/core/exported"
+	ibctm "github.com/cosmos/ibc-go/v8/modules/light-clients/07-tendermint"
+	"github.com/cosmos/ibc-go/v8/testing/mock"
+)
+
+func (suite *TypesTestSuite) TestGetSelfConsensusState() {
+	var (
+		consensusHost  clienttypes.ConsensusHost
+		consensusState exported.ConsensusState
+		height         clienttypes.Height
+	)
+
+	cases := []struct {
+		name     string
+		malleate func()
+		expError error
+	}{
+		{
+			name:     "success",
+			malleate: func() {},
+			expError: nil,
+		},
+		{
+			name: "failure: delegate error",
+			malleate: func() {
+				consensusHost.(*mock.ConsensusHost).GetSelfConsensusStateFn = func(ctx sdk.Context, height exported.Height) (exported.ConsensusState, error) {
+					return nil, mock.MockApplicationCallbackError
+				}
+			},
+			expError: mock.MockApplicationCallbackError,
+		},
+	}
+
+	for i, tc := range cases {
+		tc := tc
+		suite.Run(tc.name, func() {
+			suite.SetupTest()
+			height = clienttypes.ZeroHeight()
+
+			wrappedClientConsensusStateBz := clienttypes.MustMarshalConsensusState(suite.chainA.App.AppCodec(), wasmtesting.MockTendermintClientConsensusState)
+			consensusState = types.NewConsensusState(wrappedClientConsensusStateBz)
+
+			consensusHost = &mock.ConsensusHost{
+				GetSelfConsensusStateFn: func(ctx sdk.Context, height exported.Height) (exported.ConsensusState, error) {
+					return consensusState, nil
+				},
+			}
+
+			tc.malleate()
+
+			var err error
+			consensusHost, err = types.NewWasmConsensusHost(suite.chainA.Codec, consensusHost)
+			suite.Require().NoError(err)
+
+			suite.chainA.App.GetIBCKeeper().ClientKeeper.SetConsensusHost(
+				consensusHost,
+			)
+
+			cs, err := suite.chainA.App.GetIBCKeeper().ClientKeeper.GetSelfConsensusState(suite.chainA.GetContext(), height)
+
+			expPass := tc.expError == nil
+			if expPass {
+				suite.Require().NoError(err, "Case %d should have passed: %s", i, tc.name)
+				suite.Require().NotNil(cs, "Case %d should have passed: %s", i, tc.name)
+				suite.Require().NotNil(cs.(*types.ConsensusState).Data, "Case %d should have passed: %s", i, tc.name)
+			} else {
+				suite.Require().ErrorIs(err, tc.expError, "Case %d should have failed: %s", i, tc.name)
+				suite.Require().Nil(cs, "Case %d should have failed: %s", i, tc.name)
+			}
+		})
+	}
+}
+
+func (suite *TypesTestSuite) TestValidateSelfClient() {
+	var (
+		clientState   exported.ClientState
+		consensusHost clienttypes.ConsensusHost
+	)
+
+	testCases := []struct {
+		name     string
+		malleate func()
+		expError error
+	}{
+		{
+			name:     "success",
+			malleate: func() {},
+			expError: nil,
+		},
+		{
+			name: "failure: invalid data",
+			malleate: func() {
+				clientState = types.NewClientState(nil, wasmtesting.Code, clienttypes.ZeroHeight())
+			},
+			expError: clienttypes.ErrInvalidClient,
+		},
+		{
+			name: "failure: invalid clientstate type",
+			malleate: func() {
+				clientState = &ibctm.ClientState{}
+			},
+			expError: clienttypes.ErrInvalidClient,
+		},
+		{
+			name: "failure: delegate error propagates",
+			malleate: func() {
+				consensusHost.(*mock.ConsensusHost).ValidateSelfClientFn = func(ctx sdk.Context, clientState exported.ClientState) error {
+					return mock.MockApplicationCallbackError
+				}
+			},
+			expError: mock.MockApplicationCallbackError,
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		suite.Run(tc.name, func() {
+			suite.SetupTest()
+
+			clientState = types.NewClientState(wasmtesting.CreateMockClientStateBz(suite.chainA.Codec, suite.checksum), wasmtesting.Code, clienttypes.ZeroHeight())
+			consensusHost = &mock.ConsensusHost{}
+
+			tc.malleate()
+
+			var err error
+			consensusHost, err = types.NewWasmConsensusHost(suite.chainA.Codec, consensusHost)
+			suite.Require().NoError(err)
+
+			suite.chainA.App.GetIBCKeeper().ClientKeeper.SetConsensusHost(
+				consensusHost,
+			)
+
+			err = suite.chainA.App.GetIBCKeeper().ClientKeeper.ValidateSelfClient(suite.chainA.GetContext(), clientState)
+
+			expPass := tc.expError == nil
+			if expPass {
+				suite.Require().NoError(err, "expected valid client for case: %s", tc.name)
+			} else {
+				suite.Require().ErrorIs(err, tc.expError, "expected %s got %s", tc.expError, err)
+			}
+		})
+	}
+}