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package contracts
import (
"bytes"
"errors"
"fmt"
"io"
"math/big"
"github.com/ethereum-optimism/optimism/op-service/predeploys"
"github.com/ethereum-optimism/optimism/op-service/solabi"
"github.com/ethereum-optimism/optimism/op-service/sources/batching"
"github.com/ethereum-optimism/optimism/op-supervisor/supervisor/types"
"github.com/ethereum-optimism/optimism/packages/contracts-bedrock/snapshots"
"github.com/ethereum/go-ethereum/common"
ethTypes "github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/crypto"
)
const (
eventExecutingMessage = "ExecutingMessage"
)
var (
ErrEventNotFound = errors.New("event not found")
)
type contractIdentifier struct {
// Origin represents the address that initiated the message
// it is used in combination with the MsgHash to uniquely identify a message
// and is hashed into the log hash, not stored directly.
Origin common.Address
LogIndex *big.Int
BlockNumber *big.Int
ChainId *big.Int
Timestamp *big.Int
}
type CrossL2Inbox struct {
contract *batching.BoundContract
}
func NewCrossL2Inbox() *CrossL2Inbox {
abi := snapshots.LoadCrossL2InboxABI()
return &CrossL2Inbox{
contract: batching.NewBoundContract(abi, predeploys.CrossL2InboxAddr),
}
}
func (i *CrossL2Inbox) DecodeExecutingMessageLog(l *ethTypes.Log) (types.ExecutingMessage, error) {
if l.Address != i.contract.Addr() {
return types.ExecutingMessage{}, fmt.Errorf("%w: log not from CrossL2Inbox", ErrEventNotFound)
}
// use DecodeEvent to check the name of the event
// but the actual decoding is done manually to extract the contract identifier
name, _, err := i.contract.DecodeEvent(l)
if errors.Is(err, batching.ErrUnknownEvent) {
return types.ExecutingMessage{}, fmt.Errorf("%w: %v", ErrEventNotFound, err.Error())
} else if err != nil {
return types.ExecutingMessage{}, fmt.Errorf("failed to decode event: %w", err)
}
if name != eventExecutingMessage {
return types.ExecutingMessage{}, fmt.Errorf("%w: event %v not an ExecutingMessage event", ErrEventNotFound, name)
}
// the second topic is the hash of the payload (the first is the event ID)
msgHash := l.Topics[1]
// the first 32 bytes of the data are the msgHash, so we skip them
identifierBytes := bytes.NewReader(l.Data[32:])
identifier, err := identifierFromBytes(identifierBytes)
if err != nil {
return types.ExecutingMessage{}, fmt.Errorf("failed to read contract identifier: %w", err)
}
chainID, err := types.ChainIDFromBig(identifier.ChainId).ToUInt32()
if err != nil {
return types.ExecutingMessage{}, fmt.Errorf("failed to convert chain ID %v to uint32: %w", identifier.ChainId, err)
}
hash := payloadHashToLogHash(msgHash, identifier.Origin)
return types.ExecutingMessage{
Chain: chainID,
Hash: hash,
BlockNum: identifier.BlockNumber.Uint64(),
LogIdx: uint32(identifier.LogIndex.Uint64()),
Timestamp: identifier.Timestamp.Uint64(),
}, nil
}
// identifierFromBytes reads a contract identifier from a byte stream.
// it follows the spec and matches the CrossL2Inbox.json definition,
// rather than relying on reflection, as that can be error-prone regarding struct ordering
func identifierFromBytes(identifierBytes io.Reader) (contractIdentifier, error) {
origin, err := solabi.ReadAddress(identifierBytes)
if err != nil {
return contractIdentifier{}, fmt.Errorf("failed to read origin address: %w", err)
}
originAddr := common.BytesToAddress(origin[:])
blockNumber, err := solabi.ReadUint256(identifierBytes)
if err != nil {
return contractIdentifier{}, fmt.Errorf("failed to read block number: %w", err)
}
logIndex, err := solabi.ReadUint256(identifierBytes)
if err != nil {
return contractIdentifier{}, fmt.Errorf("failed to read log index: %w", err)
}
timestamp, err := solabi.ReadUint256(identifierBytes)
if err != nil {
return contractIdentifier{}, fmt.Errorf("failed to read timestamp: %w", err)
}
chainID, err := solabi.ReadUint256(identifierBytes)
if err != nil {
return contractIdentifier{}, fmt.Errorf("failed to read chain ID: %w", err)
}
return contractIdentifier{
Origin: originAddr,
BlockNumber: blockNumber,
LogIndex: logIndex,
Timestamp: timestamp,
ChainId: chainID,
}, nil
}
// payloadHashToLogHash converts the payload hash to the log hash
// it is the concatenation of the log's address and the hash of the log's payload,
// which is then hashed again. This is the hash that is stored in the log storage.
// The logHash can then be used to traverse from the executing message
// to the log the referenced initiating message.
// TODO(#12424): this function is duplicated between contracts and backend/source/log_processor.go
// to avoid a circular dependency. It should be reorganized to avoid this duplication.
func payloadHashToLogHash(payloadHash common.Hash, addr common.Address) common.Hash {
msg := make([]byte, 0, 2*common.HashLength)
msg = append(msg, addr.Bytes()...)
msg = append(msg, payloadHash.Bytes()...)
return crypto.Keccak256Hash(msg)
}