make packet commitments fixed length (#7564)

* make packet commitments fixed length

* updated docs for packet commits

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

@@ -7,8 +7,8 @@ import (
 )
 
 // CommitPacket returns the V2 packet commitment bytes. The commitment consists of:
-// 0x02 + sha256_hash(destinationChannel) + sha256_hash(timeout) + sha256_hash(payload) from a given packet.
-// This results in a fixed length preimage.
+// ha256_hash(0x02 + sha256_hash(destinationChannel) + sha256_hash(timeout) + sha256_hash(payload)) from a given packet.
+// This results in a fixed length preimage of 32 bytes.
 // 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 {
@@ -27,8 +27,10 @@ func CommitPacket(packet Packet) []byte {
 	appHash := sha256.Sum256(appBytes)
 	buf = append(buf, appHash[:]...)
 
+	buf = append([]byte{byte(2)}, buf...)
+
 	hash := sha256.Sum256(buf)
-	return append([]byte{byte(2)}, hash[:]...)
+	return hash[:]
 }
 
 // hashPayload returns the hash of the payload.
@@ -48,14 +50,17 @@ func hashPayload(data Payload) []byte {
 	return hash[:]
 }
 
-// CommitAcknowledgement returns the hash of the acknowledgement data.
+// CommitAcknowledgement returns the V2 acknowledgement commitment bytes. The commitment consists of:
+// sha256_hash(0x02 + sha256_hash(ack1) + sha256_hash(ack2) + ...) from a given acknowledgement.
 func CommitAcknowledgement(acknowledgement Acknowledgement) []byte {
 	var buf []byte
 	for _, ack := range acknowledgement.GetAppAcknowledgements() {
 		hash := sha256.Sum256(ack)
 		buf = append(buf, hash[:]...)
 	}
 
+	buf = append([]byte{byte(2)}, buf...)
+
 	hash := sha256.Sum256(buf)
-	return append([]byte{byte(2)}, hash[:]...)
+	return hash[:]
 }

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

@@ -0,0 +1,58 @@
+package types_test
+
+import (
+	"encoding/hex"
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	transfertypes "github.com/cosmos/ibc-go/v9/modules/apps/transfer/types"
+	"github.com/cosmos/ibc-go/v9/modules/core/04-channel/v2/types"
+)
+
+// TestCommitPacket is primarily used to document the expected commitment output
+// so that other implementations (such as the IBC Solidity) can replicate the
+// same commitment output. But it is also useful to catch any changes in the commitment.
+func TestCommitPacket(t *testing.T) {
+	transferData, err := json.Marshal(transfertypes.FungibleTokenPacketData{
+		Denom:    "uatom",
+		Amount:   "1000000",
+		Sender:   "sender",
+		Receiver: "receiver",
+		Memo:     "memo",
+	})
+	require.NoError(t, err)
+	packet := types.Packet{
+		Sequence:           1,
+		SourceChannel:      "channel-0",
+		DestinationChannel: "channel-1",
+		TimeoutTimestamp:   100,
+		Payloads: []types.Payload{
+			{
+				SourcePort:      transfertypes.PortID,
+				DestinationPort: transfertypes.PortID,
+				Version:         transfertypes.V1,
+				Encoding:        "application/json",
+				Value:           transferData,
+			},
+		},
+	}
+	commitment := types.CommitPacket(packet)
+	require.Equal(t, "450194f2ce25b12487f65593e106d91367a1e5c90b2efc03ed78265a54cfcebe", hex.EncodeToString(commitment))
+	require.Len(t, commitment, 32)
+}
+
+// TestCommitAcknowledgement is primarily used to document the expected commitment output
+// so that other implementations (such as the IBC Solidity) can replicate the
+// same commitment output. But it is also useful to catch any changes in the commitment.
+func TestCommitAcknowledgement(t *testing.T) {
+	ack := types.Acknowledgement{
+		AppAcknowledgements: [][]byte{
+			[]byte("some bytes"),
+		},
+	}
+
+	commitment := types.CommitAcknowledgement(ack)
+	require.Equal(t, "f03b4667413e56aaf086663267913e525c442b56fa1af4fa3f3dab9f37044c5b", hex.EncodeToString(commitment))
+}

modules/core/24-host/v2/packet_key_test.go

@@ -0,0 +1,34 @@
+package v2_test
+
+import (
+	"encoding/hex"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/cosmos/ibc-go/v9/modules/core/24-host/v2"
+)
+
+// TestPacketCommitmentKey is primarily used to document the expected key output
+// so that other implementations (such as the IBC Solidity) can replicate the
+// same key output. But it is also useful to catch any changes in the keys.
+func TestPacketCommitmentKey(t *testing.T) {
+	actual := hex.EncodeToString(v2.PacketCommitmentKey("channel-0", 1))
+	require.Equal(t, "6368616e6e656c2d30010000000000000001", actual)
+}
+
+// TestPacketReceiptKey is primarily used to document the expected key output
+// so that other implementations (such as the IBC Solidity) can replicate the
+// same key output. But it is also useful to catch any changes in the keys.
+func TestPacketReceiptKey(t *testing.T) {
+	actual := hex.EncodeToString(v2.PacketReceiptKey("channel-0", 1))
+	require.Equal(t, "6368616e6e656c2d30020000000000000001", actual)
+}
+
+// TestPacketAcknowledgementKey is primarily used to document the expected key output
+// so that other implementations (such as the IBC Solidity) can replicate the
+// same key output. But it is also useful to catch any changes in the keys.
+func TestPacketAcknowledgementKey(t *testing.T) {
+	actual := hex.EncodeToString(v2.PacketAcknowledgementKey("channel-0", 1))
+	require.Equal(t, "6368616e6e656c2d30030000000000000001", actual)
+}