Match commitment to specification (#7544)

* fix hash

* prepend hash with byte 0x02

* fix hash to spec

* chore: update function documentation to align with implementation.

---------

Co-authored-by: DimitrisJim <[email protected]>

modules/core/04-channel/v2/keeper/keeper.go

@@ -133,7 +133,7 @@ func (k *Keeper) HasPacketReceipt(ctx context.Context, channelID string, sequenc
 // This is a public path that is standardized by the IBC V2 specification.
 func (k *Keeper) SetPacketReceipt(ctx context.Context, channelID string, sequence uint64) {
 	store := k.storeService.OpenKVStore(ctx)
-	if err := store.Set(hostv2.PacketReceiptKey(channelID, sequence), []byte{byte(1)}); err != nil {
+	if err := store.Set(hostv2.PacketReceiptKey(channelID, sequence), []byte{byte(2)}); err != nil {
 		panic(err)
 	}
 }

modules/core/04-channel/v2/types/commitment.go

@@ -7,22 +7,28 @@ import (
 )
 
 // CommitPacket returns the V2 packet commitment bytes. The commitment consists of:
-// sha256_hash(timeout) + sha256_hash(destinationChannel) + sha256_hash(payload) from a given packet.
+// 0x02 + sha256_hash(destinationChannel) + sha256_hash(timeout) + sha256_hash(payload) from a given packet.
 // This results in a fixed length preimage.
 // NOTE: A fixed length preimage is ESSENTIAL to prevent relayers from being able
 // to malleate the packet fields and create a commitment hash that matches the original packet.
 func CommitPacket(packet Packet) []byte {
-	buf := sdk.Uint64ToBigEndian(packet.GetTimeoutTimestamp())
-
+	var buf []byte
 	destIDHash := sha256.Sum256([]byte(packet.DestinationChannel))
 	buf = append(buf, destIDHash[:]...)
 
+	timeoutBytes := sdk.Uint64ToBigEndian(packet.GetTimeoutTimestamp())
+	timeoutHash := sha256.Sum256(timeoutBytes)
+	buf = append(buf, timeoutHash[:]...)
+
+	var appBytes []byte
 	for _, payload := range packet.Payloads {
-		buf = append(buf, hashPayload(payload)...)
+		appBytes = append(appBytes, hashPayload(payload)...)
 	}
+	appHash := sha256.Sum256(appBytes)
+	buf = append(buf, appHash[:]...)
 
 	hash := sha256.Sum256(buf)
-	return hash[:]
+	return append([]byte{byte(2)}, hash[:]...)
 }
 
 // hashPayload returns the hash of the payload.
@@ -32,12 +38,12 @@ func hashPayload(data Payload) []byte {
 	buf = append(buf, sourceHash[:]...)
 	destHash := sha256.Sum256([]byte(data.DestinationPort))
 	buf = append(buf, destHash[:]...)
-	payloadValueHash := sha256.Sum256(data.Value)
-	buf = append(buf, payloadValueHash[:]...)
-	payloadEncodingHash := sha256.Sum256([]byte(data.Encoding))
-	buf = append(buf, payloadEncodingHash[:]...)
 	payloadVersionHash := sha256.Sum256([]byte(data.Version))
 	buf = append(buf, payloadVersionHash[:]...)
+	payloadEncodingHash := sha256.Sum256([]byte(data.Encoding))
+	buf = append(buf, payloadEncodingHash[:]...)
+	payloadValueHash := sha256.Sum256(data.Value)
+	buf = append(buf, payloadValueHash[:]...)
 	hash := sha256.Sum256(buf)
 	return hash[:]
 }
@@ -51,5 +57,5 @@ func CommitAcknowledgement(acknowledgement Acknowledgement) []byte {
 	}
 
 	hash := sha256.Sum256(buf)
-	return hash[:]
+	return append([]byte{byte(2)}, hash[:]...)
 }