improve bytes of bytes hashing (#249)

core/services/ocr2/plugins/ccip/execution_reporting_plugin_test.go

@@ -1227,7 +1227,7 @@ func Test_calculateObservedMessagesConsensus(t *testing.T) {
 				f: 1,
 			},
 			want: []ObservedMessage{
-				{SeqNr: 1, MsgData: MsgData{TokenData: [][]byte{{0x1}}}},
+				{SeqNr: 1, MsgData: MsgData{TokenData: [][]byte{{0x3}}}},
 			},
 		},
 	}

core/services/ocr2/plugins/ccip/internal/hashlib/common.go

@@ -1,6 +1,8 @@
 package hashlib
 
 import (
+	"strconv"
+
 	"github.com/smartcontractkit/chainlink/v2/core/utils"
 )
 
@@ -10,9 +12,16 @@ func BytesOfBytesKeccak(b [][]byte) ([32]byte, error) {
 		return [32]byte{}, nil
 	}
 
-	h := utils.Keccak256Fixed(b[0])
-	for _, v := range b[1:] {
-		h = utils.Keccak256Fixed(append(h[:], v...))
+	joinedBytes := make([]byte, 0)
+	joinedBytes = append(joinedBytes, intToBytes(int64(len(b)))...)
+	for i := range b {
+		joinedBytes = append(joinedBytes, intToBytes(int64(len(b[i])))...)
+		joinedBytes = append(joinedBytes, b[i]...)
 	}
-	return h, nil
+
+	return utils.Keccak256Fixed(joinedBytes), nil
+}
+
+func intToBytes(v int64) []byte {
+	return []byte(strconv.FormatInt(v, 10))
 }

core/services/ocr2/plugins/ccip/internal/hashlib/common_test.go

@@ -4,16 +4,37 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+
+	"github.com/smartcontractkit/chainlink/v2/core/utils"
 )
 
 func TestBytesOfBytesKeccak(t *testing.T) {
-	h, err := BytesOfBytesKeccak(nil)
-	assert.NoError(t, err)
-	assert.Equal(t, [32]byte{}, h)
-
-	h1, err := BytesOfBytesKeccak([][]byte{{0x1}, {0x1}})
-	assert.NoError(t, err)
-	h2, err := BytesOfBytesKeccak([][]byte{{0x1, 0x1}})
-	assert.NoError(t, err)
-	assert.NotEqual(t, h1, h2)
+	t.Run("simple case", func(t *testing.T) {
+		h, err := BytesOfBytesKeccak(nil)
+		assert.NoError(t, err)
+		assert.Equal(t, [32]byte{}, h)
+
+		h1, err := BytesOfBytesKeccak([][]byte{{0x1}, {0x1}})
+		assert.NoError(t, err)
+		h2, err := BytesOfBytesKeccak([][]byte{{0x1, 0x1}})
+		assert.NoError(t, err)
+		assert.NotEqual(t, h1, h2)
+	})
+
+	t.Run("should not have collision", func(t *testing.T) {
+		s1 := utils.RandomBytes32()
+		s2 := utils.RandomBytes32()
+
+		hs1, err := BytesOfBytesKeccak([][]byte{s1[:]})
+		assert.NoError(t, err)
+
+		h1, err := BytesOfBytesKeccak([][]byte{s1[:], s2[:]})
+		assert.NoError(t, err)
+
+		h2, err := BytesOfBytesKeccak([][]byte{append(hs1[:], s2[:]...)})
+		assert.NoError(t, err)
+
+		assert.NotEqual(t, h1, h2)
+	})
+
 }