Deterministic hashes for ETH lockups

We're missing a nonce for truly unique hashes - for now, two
identical transfers will only be executed once.

bridge/cmd/guardiand/main.go

@@ -141,6 +141,7 @@ func main() {
 						zap.String("source", hex.EncodeToString(k.SourceAddress[:])),
 						zap.String("target", hex.EncodeToString(k.TargetAddress[:])),
 						zap.String("amount", k.Amount.String()),
+						zap.String("hash", hex.EncodeToString(k.Hash())),
 					)
 				}
 			}

bridge/pkg/common/bridgewatcher.go

@@ -0,0 +1,5 @@
+package common
+
+type BridgeWatcher interface {
+	WatchLockups(events chan *ChainLock) error
+}

bridge/pkg/common/chainlock.go

@@ -0,0 +1,46 @@
+package common
+
+import (
+	"crypto/sha256"
+	"encoding/json"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+
+	"github.com/certusone/wormhole/bridge/pkg/vaa"
+)
+
+type ChainLock struct {
+	TxHash common.Hash
+
+	SourceAddress vaa.Address
+	TargetAddress vaa.Address
+
+	SourceChain vaa.ChainID
+	TargetChain vaa.ChainID
+
+	TokenChain   vaa.ChainID
+	TokenAddress vaa.Address
+
+	Amount *big.Int
+}
+
+// Hash returns a deterministic hash of the given ChainLock, meant to be used
+// as primary key for the distributed round of signing.
+//
+// TODO: the ETH contract is missing a nonce, so it's not yet deterministic
+func (l *ChainLock) Hash() []byte {
+
+	// TODO: json.Marshal being deterministic is an implementation detail - what guarantees do we need?
+	// We do not necessarily need stable serialization across releases, but they do need to be unique.
+
+	b, err := json.Marshal(l)
+	if err != nil {
+		panic(err)
+	}
+
+	h := sha256.New()
+	h.Write(b)
+
+	return h.Sum(nil)
+}

bridge/pkg/common/types.go

@@ -1,25 +0,0 @@
-package common
-
-import (
-	"github.com/certusone/wormhole/bridge/pkg/vaa"
-	"math/big"
-)
-
-type (
-	BridgeWatcher interface {
-		WatchLockups(events chan *ChainLock) error
-	}
-
-	ChainLock struct {
-		SourceAddress vaa.Address
-		TargetAddress vaa.Address
-
-		SourceChain vaa.ChainID
-		TargetChain vaa.ChainID
-
-		TokenChain   vaa.ChainID
-		TokenAddress vaa.Address
-
-		Amount *big.Int
-	}
-)

bridge/pkg/ethereum/watcher.go

@@ -3,17 +3,19 @@ package ethereum
 import (
 	"context"
 	"fmt"
-	"github.com/certusone/wormhole/bridge/pkg/common"
+	"sync"
-	"github.com/certusone/wormhole/bridge/pkg/ethereum/abi"
+	"time"
-	"github.com/certusone/wormhole/bridge/pkg/supervisor"
+
-	"github.com/certusone/wormhole/bridge/pkg/vaa"
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	eth_common "github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethclient"
 	"go.uber.org/zap"
-	"sync"
+
-	"time"
+	"github.com/certusone/wormhole/bridge/pkg/common"
+	"github.com/certusone/wormhole/bridge/pkg/ethereum/abi"
+	"github.com/certusone/wormhole/bridge/pkg/supervisor"
+	"github.com/certusone/wormhole/bridge/pkg/vaa"
 )
 
 type (
@@ -30,8 +32,6 @@ type (
 
 	pendingLock struct {
 		lock *common.ChainLock
-
-		txHash eth_common.Hash
 		height uint64
 	}
 )
@@ -73,6 +73,7 @@ func (e *EthBridgeWatcher) Run(ctx context.Context) error {
 				return
 			case ev := <-sink:
 				lock := &common.ChainLock{
+					TxHash:        ev.Raw.TxHash,
 					SourceAddress: ev.Sender,
 					TargetAddress: ev.Recipient,
 					SourceChain:   vaa.ChainIDEthereum,
@@ -87,7 +88,6 @@ func (e *EthBridgeWatcher) Run(ctx context.Context) error {
 				e.pendingLocksGuard.Lock()
 				e.pendingLocks[ev.Raw.TxHash] = &pendingLock{
 					lock:   lock,
-					txHash: ev.Raw.TxHash,
 					height: ev.Raw.BlockNumber,
 				}
 				e.pendingLocksGuard.Unlock()
@@ -121,7 +121,7 @@ func (e *EthBridgeWatcher) Run(ctx context.Context) error {
 
 					// Transaction was dropped and never picked up again
 					if pLock.height+4*e.minConfirmations <= blockNumberU {
-						logger.Debug("lockup timed out", zap.Stringer("tx", pLock.txHash),
+						logger.Debug("lockup timed out", zap.Stringer("tx", pLock.lock.TxHash),
 							zap.Stringer("number", ev.Number))
 						delete(e.pendingLocks, hash)
 						continue
@@ -129,7 +129,7 @@ func (e *EthBridgeWatcher) Run(ctx context.Context) error {
 
 					// Transaction is now ready
 					if pLock.height+e.minConfirmations <= ev.Number.Uint64() {
-						logger.Debug("lockup confirmed", zap.Stringer("tx", pLock.txHash),
+						logger.Debug("lockup confirmed", zap.Stringer("tx", pLock.lock.TxHash),
 							zap.Stringer("number", ev.Number))
 						delete(e.pendingLocks, hash)
 						e.evChan <- pLock.lock

ethereum/contracts/Wormhole.sol

@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: Apache 2
 
 // TODO(hendrik): reentrancy protection for all methods
+// TODO(hendrik): switch-over feature
 
 pragma solidity ^0.6.0;
 pragma experimental ABIEncoderV2;
@@ -197,6 +198,7 @@ contract Wormhole {
         isWrappedAsset[asset] = true;
     }
 
+    // TODO(hendrik): nonce
     function lockAssets(
         address asset,
         uint256 amount,