op-program: Compute the final L2 output root and verify it against a claim

op-node/node/api.go

@@ -9,7 +9,6 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/log"
 
-	"github.com/ethereum-optimism/optimism/op-bindings/bindings"
 	"github.com/ethereum-optimism/optimism/op-bindings/predeploys"
 	"github.com/ethereum-optimism/optimism/op-node/eth"
 	"github.com/ethereum-optimism/optimism/op-node/rollup"
@@ -115,12 +114,7 @@ func (n *nodeAPI) OutputAtBlock(ctx context.Context, number hexutil.Uint64) (*et
 	}
 
 	var l2OutputRootVersion eth.Bytes32 // it's zero for now
-	l2OutputRoot, err := rollup.ComputeL2OutputRoot(&bindings.TypesOutputRootProof{
-		Version:                  l2OutputRootVersion,
-		StateRoot:                head.Root(),
-		MessagePasserStorageRoot: proof.StorageHash,
-		LatestBlockhash:          head.Hash(),
-	})
+	l2OutputRoot, err := rollup.ComputeL2OutputRootV0(head, proof.StorageHash)
 	if err != nil {
 		n.log.Error("Error computing L2 output root, nil ptr passed to hashing function")
 		return nil, err

op-node/rollup/output_root.go

@@ -24,3 +24,13 @@ func ComputeL2OutputRoot(proofElements *bindings.TypesOutputRootProof) (eth.Byte
 	)
 	return eth.Bytes32(digest), nil
 }
+
+func ComputeL2OutputRootV0(block eth.BlockInfo, storageRoot [32]byte) (eth.Bytes32, error) {
+	var l2OutputRootVersion eth.Bytes32 // it's zero for now
+	return ComputeL2OutputRoot(&bindings.TypesOutputRootProof{
+		Version:                  l2OutputRootVersion,
+		StateRoot:                block.Root(),
+		MessagePasserStorageRoot: storageRoot,
+		LatestBlockhash:          block.Hash(),
+	})
+}

op-program/client/driver/driver.go

@@ -18,17 +18,24 @@ type Derivation interface {
 	SafeL2Head() eth.L2BlockRef
 }
 
+type L2Source interface {
+	derive.Engine
+	L2OutputRoot() (eth.Bytes32, error)
+}
+
 type Driver struct {
-	logger   log.Logger
-	pipeline Derivation
+	logger       log.Logger
+	pipeline     Derivation
+	l2OutputRoot func() (eth.Bytes32, error)
 }
 
-func NewDriver(logger log.Logger, cfg *rollup.Config, l1Source derive.L1Fetcher, l2Source derive.Engine) *Driver {
+func NewDriver(logger log.Logger, cfg *rollup.Config, l1Source derive.L1Fetcher, l2Source L2Source) *Driver {
 	pipeline := derive.NewDerivationPipeline(logger, cfg, l1Source, l2Source, metrics.NoopMetrics)
 	pipeline.Reset()
 	return &Driver{
-		logger:   logger,
-		pipeline: pipeline,
+		logger:       logger,
+		pipeline:     pipeline,
+		l2OutputRoot: l2Source.L2OutputRoot,
 	}
 }
 
@@ -51,3 +58,13 @@ func (d *Driver) Step(ctx context.Context) error {
 func (d *Driver) SafeHead() eth.L2BlockRef {
 	return d.pipeline.SafeL2Head()
 }
+
+func (d *Driver) ValidateClaim(claimedOutputRoot eth.Bytes32) bool {
+	outputRoot, err := d.l2OutputRoot()
+	if err != nil {
+		d.logger.Info("Failed to calculate L2 output root", "err", err)
+		return false
+	}
+	d.logger.Info("Derivation complete", "head", d.SafeHead(), "output", outputRoot, "claim", claimedOutputRoot)
+	return claimedOutputRoot == outputRoot
+}

op-program/client/driver/driver_test.go

@@ -45,6 +45,36 @@ func TestNoError(t *testing.T) {
 	require.NoError(t, err)
 }
 
+func TestValidateClaim(t *testing.T) {
+	t.Run("Valid", func(t *testing.T) {
+		driver := createDriver(t, io.EOF)
+		expected := eth.Bytes32{0x11}
+		driver.l2OutputRoot = func() (eth.Bytes32, error) {
+			return expected, nil
+		}
+		valid := driver.ValidateClaim(expected)
+		require.True(t, valid)
+	})
+
+	t.Run("Invalid", func(t *testing.T) {
+		driver := createDriver(t, io.EOF)
+		driver.l2OutputRoot = func() (eth.Bytes32, error) {
+			return eth.Bytes32{0x22}, nil
+		}
+		valid := driver.ValidateClaim(eth.Bytes32{0x11})
+		require.False(t, valid)
+	})
+
+	t.Run("Error", func(t *testing.T) {
+		driver := createDriver(t, io.EOF)
+		driver.l2OutputRoot = func() (eth.Bytes32, error) {
+			return eth.Bytes32{}, errors.New("boom")
+		}
+		valid := driver.ValidateClaim(eth.Bytes32{0x11})
+		require.False(t, valid)
+	})
+}
+
 func createDriver(t *testing.T, derivationResult error) *Driver {
 	derivation := &stubDerivation{nextErr: derivationResult}
 	return &Driver{

op-program/client/l2/engine.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 
+	"github.com/ethereum-optimism/optimism/op-bindings/predeploys"
 	"github.com/ethereum-optimism/optimism/op-node/eth"
 	"github.com/ethereum-optimism/optimism/op-node/rollup"
 	"github.com/ethereum-optimism/optimism/op-node/rollup/derive"
@@ -33,6 +34,19 @@ func NewOracleEngine(rollupCfg *rollup.Config, logger log.Logger, backend engine
 	}
 }
 
+func (o *OracleEngine) L2OutputRoot() (eth.Bytes32, error) {
+	outBlock := o.backend.CurrentHeader()
+	stateDB, err := o.backend.StateAt(outBlock.Root)
+	if err != nil {
+		return eth.Bytes32{}, fmt.Errorf("failed to open L2 state db at block %s: %w", outBlock.Hash(), err)
+	}
+	withdrawalsTrie, err := stateDB.StorageTrie(predeploys.L2ToL1MessagePasserAddr)
+	if err != nil {
+		return eth.Bytes32{}, fmt.Errorf("withdrawals trie unavailable at block %v: %w", outBlock.Hash(), err)
+	}
+	return rollup.ComputeL2OutputRootV0(eth.HeaderBlockInfo(outBlock), withdrawalsTrie.Hash())
+}
+
 func (o *OracleEngine) GetPayload(ctx context.Context, payloadId eth.PayloadID) (*eth.ExecutionPayload, error) {
 	return o.api.GetPayloadV1(ctx, payloadId)
 }

op-program/host/cmd/main.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/ethereum-optimism/optimism/op-node/chaincfg"
+	"github.com/ethereum-optimism/optimism/op-node/eth"
 	"github.com/ethereum-optimism/optimism/op-node/rollup/derive"
 	cldr "github.com/ethereum-optimism/optimism/op-program/client/driver"
 	"github.com/ethereum-optimism/optimism/op-program/host/config"
@@ -41,6 +42,10 @@ var VersionWithMeta = func() string {
 	return v
 }()
 
+var (
+	ErrClaimNotValid = errors.New("invalid claim")
+)
+
 func main() {
 	args := os.Args
 	err := run(args, FaultProofProgram)
@@ -124,6 +129,9 @@ func FaultProofProgram(logger log.Logger, cfg *config.Config) error {
 			return err
 		}
 	}
-	logger.Info("Derivation complete", "head", d.SafeHead())
+	claim := cfg.L2Claim
+	if !d.ValidateClaim(eth.Bytes32(claim)) {
+		return ErrClaimNotValid
+	}
 	return nil
 }

op-program/host/cmd/main_test.go

@@ -16,6 +16,7 @@ import (
 // Use HexToHash(...).Hex() to ensure the strings are the correct length for a hash
 var l1HeadValue = common.HexToHash("0x111111").Hex()
 var l2HeadValue = common.HexToHash("0x222222").Hex()
+var l2ClaimValue = common.HexToHash("0x333333").Hex()
 
 func TestLogLevel(t *testing.T) {
 	t.Run("RejectInvalid", func(t *testing.T) {
@@ -34,7 +35,12 @@ func TestLogLevel(t *testing.T) {
 
 func TestDefaultCLIOptionsMatchDefaultConfig(t *testing.T) {
 	cfg := configForArgs(t, addRequiredArgs())
-	defaultCfg := config.NewConfig(&chaincfg.Goerli, "genesis.json", common.HexToHash(l1HeadValue), common.HexToHash(l2HeadValue))
+	defaultCfg := config.NewConfig(
+		&chaincfg.Goerli,
+		"genesis.json",
+		common.HexToHash(l1HeadValue),
+		common.HexToHash(l2HeadValue),
+		common.HexToHash(l2ClaimValue))
 	require.Equal(t, defaultCfg, cfg)
 }
 
@@ -167,11 +173,26 @@ func TestL1RPCKind(t *testing.T) {
 // Offline support will be added later, but for now it just bails out with an error
 func TestOfflineModeNotSupported(t *testing.T) {
 	logger := log.New()
-	cfg := config.NewConfig(&chaincfg.Goerli, "genesis.json", common.HexToHash(l1HeadValue), common.HexToHash(l2HeadValue))
+	cfg := config.NewConfig(&chaincfg.Goerli, "genesis.json", common.HexToHash(l1HeadValue), common.HexToHash(l2HeadValue), common.HexToHash(l2ClaimValue))
 	err := FaultProofProgram(logger, cfg)
 	require.ErrorContains(t, err, "offline mode not supported")
 }
 
+func TestL2Claim(t *testing.T) {
+	t.Run("Required", func(t *testing.T) {
+		verifyArgsInvalid(t, "flag l2.claim is required", addRequiredArgsExcept("--l2.claim"))
+	})
+
+	t.Run("Valid", func(t *testing.T) {
+		cfg := configForArgs(t, replaceRequiredArg("--l2.claim", l2ClaimValue))
+		require.EqualValues(t, common.HexToHash(l2ClaimValue), cfg.L2Claim)
+	})
+
+	t.Run("Invalid", func(t *testing.T) {
+		verifyArgsInvalid(t, config.ErrInvalidL2Claim.Error(), replaceRequiredArg("--l2.claim", "something"))
+	})
+}
+
 func verifyArgsInvalid(t *testing.T, messageContains string, cliArgs []string) {
 	_, _, err := runWithArgs(cliArgs)
 	require.ErrorContains(t, err, messageContains)
@@ -220,6 +241,7 @@ func requiredArgs() map[string]string {
 		"--network":    "goerli",
 		"--l1.head":    l1HeadValue,
 		"--l2.head":    l2HeadValue,
+		"--l2.claim":   l2ClaimValue,
 		"--l2.genesis": "genesis.json",
 	}
 }

op-program/host/config/config.go

@@ -17,6 +17,7 @@ var (
 	ErrInvalidL1Head       = errors.New("invalid l1 head")
 	ErrInvalidL2Head       = errors.New("invalid l2 head")
 	ErrL1AndL2Inconsistent = errors.New("l1 and l2 options must be specified together or both omitted")
+	ErrInvalidL2Claim      = errors.New("invalid l2 claim")
 )
 
 type Config struct {
@@ -25,6 +26,7 @@ type Config struct {
 	L2GenesisPath string
 	L1Head        common.Hash
 	L2Head        common.Hash
+	L2Claim       common.Hash
 	L1URL         string
 	L1TrustRPC    bool
 	L1RPCKind     sources.RPCProviderKind
@@ -43,6 +45,9 @@ func (c *Config) Check() error {
 	if c.L2Head == (common.Hash{}) {
 		return ErrInvalidL2Head
 	}
+	if c.L2Claim == (common.Hash{}) {
+		return ErrInvalidL2Claim
+	}
 	if c.L2GenesisPath == "" {
 		return ErrMissingL2Genesis
 	}
@@ -57,12 +62,13 @@ func (c *Config) FetchingEnabled() bool {
 }
 
 // NewConfig creates a Config with all optional values set to the CLI default value
-func NewConfig(rollupCfg *rollup.Config, l2GenesisPath string, l1Head common.Hash, l2Head common.Hash) *Config {
+func NewConfig(rollupCfg *rollup.Config, l2GenesisPath string, l1Head common.Hash, l2Head common.Hash, l2Claim common.Hash) *Config {
 	return &Config{
 		Rollup:        rollupCfg,
 		L2GenesisPath: l2GenesisPath,
 		L1Head:        l1Head,
 		L2Head:        l2Head,
+		L2Claim:       l2Claim,
 		L1RPCKind:     sources.RPCKindBasic,
 	}
 }
@@ -79,6 +85,10 @@ func NewConfigFromCLI(ctx *cli.Context) (*Config, error) {
 	if l2Head == (common.Hash{}) {
 		return nil, ErrInvalidL2Head
 	}
+	l2Claim := common.HexToHash(ctx.GlobalString(flags.L2Claim.Name))
+	if l2Claim == (common.Hash{}) {
+		return nil, ErrInvalidL2Claim
+	}
 	l1Head := common.HexToHash(ctx.GlobalString(flags.L1Head.Name))
 	if l1Head == (common.Hash{}) {
 		return nil, ErrInvalidL1Head
@@ -88,6 +98,7 @@ func NewConfigFromCLI(ctx *cli.Context) (*Config, error) {
 		L2URL:         ctx.GlobalString(flags.L2NodeAddr.Name),
 		L2GenesisPath: ctx.GlobalString(flags.L2GenesisPath.Name),
 		L2Head:        l2Head,
+		L2Claim:       l2Claim,
 		L1Head:        l1Head,
 		L1URL:         ctx.GlobalString(flags.L1NodeAddr.Name),
 		L1TrustRPC:    ctx.GlobalBool(flags.L1TrustRPC.Name),

op-program/host/config/config_test.go

@@ -11,58 +11,78 @@ import (
 
 var validRollupConfig = &chaincfg.Goerli
 var validL2GenesisPath = "genesis.json"
-var validL1Head = common.HexToHash("0x112233889988FF")
-var validL2Head = common.HexToHash("0x6303578b1fa9480389c51bbcef6fe045bb877da39740819e9eb5f36f94949bd0")
+var validL1Head = common.Hash{0xaa}
+var validL2Head = common.Hash{0xbb}
+var validL2Claim = common.Hash{0xcc}
 
 func TestDefaultConfigIsValid(t *testing.T) {
-	err := NewConfig(validRollupConfig, validL2GenesisPath, validL1Head, validL2Head).Check()
+	err := validConfig().Check()
 	require.NoError(t, err)
 }
 
 func TestRollupConfig(t *testing.T) {
 	t.Run("Required", func(t *testing.T) {
-		err := NewConfig(nil, validL2GenesisPath, validL1Head, validL2Head).Check()
+		config := validConfig()
+		config.Rollup = nil
+		err := config.Check()
 		require.ErrorIs(t, err, ErrMissingRollupConfig)
 	})
 
 	t.Run("Invalid", func(t *testing.T) {
-		err := NewConfig(&rollup.Config{}, validL2GenesisPath, validL1Head, validL2Head).Check()
+		config := validConfig()
+		config.Rollup = &rollup.Config{}
+		err := config.Check()
 		require.ErrorIs(t, err, rollup.ErrBlockTimeZero)
 	})
 }
 
 func TestL1HeadRequired(t *testing.T) {
-	err := NewConfig(validRollupConfig, validL2GenesisPath, common.Hash{}, validL2Head).Check()
+	config := validConfig()
+	config.L1Head = common.Hash{}
+	err := config.Check()
 	require.ErrorIs(t, err, ErrInvalidL1Head)
 }
 
 func TestL2HeadRequired(t *testing.T) {
-	err := NewConfig(validRollupConfig, validL2GenesisPath, validL1Head, common.Hash{}).Check()
+	config := validConfig()
+	config.L2Head = common.Hash{}
+	err := config.Check()
 	require.ErrorIs(t, err, ErrInvalidL2Head)
 }
 
+func TestL2ClaimRequired(t *testing.T) {
+	config := validConfig()
+	config.L2Claim = common.Hash{}
+	err := config.Check()
+	require.ErrorIs(t, err, ErrInvalidL2Claim)
+}
+
 func TestL2GenesisRequired(t *testing.T) {
-	err := NewConfig(validRollupConfig, "", validL1Head, validL2Head).Check()
+	config := validConfig()
+	config.L2GenesisPath = ""
+	err := config.Check()
 	require.ErrorIs(t, err, ErrMissingL2Genesis)
 }
 
 func TestFetchingArgConsistency(t *testing.T) {
 	t.Run("RequireL2WhenL1Set", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL1Head, validL2Head)
+		cfg := validConfig()
 		cfg.L1URL = "https://example.com:1234"
 		require.ErrorIs(t, cfg.Check(), ErrL1AndL2Inconsistent)
 	})
 	t.Run("RequireL1WhenL2Set", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL1Head, validL2Head)
+		cfg := validConfig()
 		cfg.L2URL = "https://example.com:1234"
 		require.ErrorIs(t, cfg.Check(), ErrL1AndL2Inconsistent)
 	})
 	t.Run("AllowNeitherSet", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL1Head, validL2Head)
+		cfg := validConfig()
+		cfg.L1URL = ""
+		cfg.L2URL = ""
 		require.NoError(t, cfg.Check())
 	})
 	t.Run("AllowBothSet", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL1Head, validL2Head)
+		cfg := validConfig()
 		cfg.L1URL = "https://example.com:1234"
 		cfg.L2URL = "https://example.com:4678"
 		require.NoError(t, cfg.Check())
@@ -71,32 +91,36 @@ func TestFetchingArgConsistency(t *testing.T) {
 
 func TestFetchingEnabled(t *testing.T) {
 	t.Run("FetchingNotEnabledWhenNoFetcherUrlsSpecified", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL1Head, validL2Head)
+		cfg := validConfig()
 		require.False(t, cfg.FetchingEnabled(), "Should not enable fetching when node URL not supplied")
 	})
 
 	t.Run("FetchingEnabledWhenFetcherUrlsSpecified", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL1Head, validL2Head)
+		cfg := validConfig()
 		cfg.L2URL = "https://example.com:1234"
 		require.False(t, cfg.FetchingEnabled(), "Should not enable fetching when node URL not supplied")
 	})
 
 	t.Run("FetchingNotEnabledWhenNoL1UrlSpecified", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL1Head, validL2Head)
+		cfg := validConfig()
 		cfg.L2URL = "https://example.com:1234"
 		require.False(t, cfg.FetchingEnabled(), "Should not enable L1 fetching when L1 node URL not supplied")
 	})
 
 	t.Run("FetchingNotEnabledWhenNoL2UrlSpecified", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL1Head, validL2Head)
+		cfg := validConfig()
 		cfg.L1URL = "https://example.com:1234"
 		require.False(t, cfg.FetchingEnabled(), "Should not enable L2 fetching when L2 node URL not supplied")
 	})
 
 	t.Run("FetchingEnabledWhenBothFetcherUrlsSpecified", func(t *testing.T) {
-		cfg := NewConfig(&chaincfg.Beta1, validL2GenesisPath, validL1Head, validL2Head)
+		cfg := validConfig()
 		cfg.L1URL = "https://example.com:1234"
 		cfg.L2URL = "https://example.com:5678"
 		require.True(t, cfg.FetchingEnabled(), "Should enable fetching when node URL supplied")
 	})
 }
+
+func validConfig() *Config {
+	return NewConfig(validRollupConfig, validL2GenesisPath, validL1Head, validL2Head, validL2Claim)
+}

op-program/host/flags/flags.go

@@ -41,6 +41,11 @@ var (
 		Usage:  "Hash of the agreed L2 block to start derivation from",
 		EnvVar: service.PrefixEnvVar(envVarPrefix, "L2_HEAD"),
 	}
+	L2Claim = cli.StringFlag{
+		Name:   "l2.claim",
+		Usage:  "Claimed L2 output root to validate",
+		EnvVar: service.PrefixEnvVar(envVarPrefix, "L2_CLAIM"),
+	}
 	L2GenesisPath = cli.StringFlag{
 		Name:   "l2.genesis",
 		Usage:  "Path to the op-geth genesis file",
@@ -71,13 +76,16 @@ var (
 // Flags contains the list of configuration options available to the binary.
 var Flags []cli.Flag
 
+var requiredFlags = []cli.Flag{
+	L1Head,
+	L2Head,
+	L2Claim,
+	L2GenesisPath,
+}
 var programFlags = []cli.Flag{
 	RollupConfig,
 	Network,
 	L2NodeAddr,
-	L1Head,
-	L2Head,
-	L2GenesisPath,
 	L1NodeAddr,
 	L1TrustRPC,
 	L1RPCProviderKind,
@@ -85,6 +93,7 @@ var programFlags = []cli.Flag{
 
 func init() {
 	Flags = append(Flags, oplog.CLIFlags(envVarPrefix)...)
+	Flags = append(Flags, requiredFlags...)
 	Flags = append(Flags, programFlags...)
 }
 
@@ -97,14 +106,10 @@ func CheckRequired(ctx *cli.Context) error {
 	if rollupConfig != "" && network != "" {
 		return fmt.Errorf("cannot specify both %s and %s", RollupConfig.Name, Network.Name)
 	}
-	if ctx.GlobalString(L2GenesisPath.Name) == "" {
-		return fmt.Errorf("flag %s is required", L2GenesisPath.Name)
-	}
-	if ctx.GlobalString(L2Head.Name) == "" {
-		return fmt.Errorf("flag %s is required", L2Head.Name)
-	}
-	if ctx.GlobalString(L1Head.Name) == "" {
-		return fmt.Errorf("flag %s is required", L1Head.Name)
+	for _, flag := range requiredFlags {
+		if ctx.GlobalString(flag.GetName()) == "" {
+			return fmt.Errorf("flag %s is required", flag.GetName())
+		}
 	}
 	return nil
 }

op-program/host/l2/l2.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"os"
 
-	"github.com/ethereum-optimism/optimism/op-node/rollup/derive"
 	cll2 "github.com/ethereum-optimism/optimism/op-program/client/l2"
 	"github.com/ethereum-optimism/optimism/op-program/host/config"
 	"github.com/ethereum/go-ethereum/core"
@@ -14,7 +13,7 @@ import (
 	"github.com/ethereum/go-ethereum/params"
 )
 
-func NewFetchingEngine(ctx context.Context, logger log.Logger, cfg *config.Config) (derive.Engine, error) {
+func NewFetchingEngine(ctx context.Context, logger log.Logger, cfg *config.Config) (*cll2.OracleEngine, error) {
 	genesis, err := loadL2Genesis(cfg)
 	if err != nil {
 		return nil, err