Add tests to demonstrate we follow the RFC

crypto/merkle/rfc6962_test.go

@@ -0,0 +1,99 @@
+package merkle
+
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// These tests were taken from https://github.com/google/trillian/blob/master/merkle/rfc6962/rfc6962.go,
+// and consequently fall under the above license.
+
+import (
+	"bytes"
+	"encoding/hex"
+	"testing"
+
+	"github.com/tendermint/tendermint/crypto/tmhash"
+)
+
+func TestRFC6962Hasher(t *testing.T) {
+	_, leafHashTrail := trailsFromByteSlices([][]byte{[]byte("L123456")})
+	leafHash := leafHashTrail.Hash
+	_, leafHashTrail = trailsFromByteSlices([][]byte{[]byte{}})
+	emptyLeafHash := leafHashTrail.Hash
+
+	for _, tc := range []struct {
+		desc string
+		got  []byte
+		want string
+	}{
+		// Check that the empty hash is not the same as the hash of an empty leaf.
+		// echo -n 00 | xxd -r -p | sha256sum
+		{
+			desc: "RFC6962 Empty Leaf",
+			want: "6e340b9cffb37a989ca544e6bb780a2c78901d3fb33738768511a30617afa01d"[:tmhash.Size*2],
+			got:  emptyLeafHash,
+		},
+		// echo -n 004C313233343536 | xxd -r -p | sha256sum
+		{
+			desc: "RFC6962 Leaf",
+			want: "395aa064aa4c29f7010acfe3f25db9485bbd4b91897b6ad7ad547639252b4d56"[:tmhash.Size*2],
+			got:  leafHash,
+		},
+		// echo -n 014E3132334E343536 | xxd -r -p | sha256sum
+		{
+			desc: "RFC6962 Node",
+			want: "aa217fe888e47007fa15edab33c2b492a722cb106c64667fc2b044444de66bbb"[:tmhash.Size*2],
+			got:  SimpleHashFromTwoHashes([]byte("N123"), []byte("N456")),
+		},
+	} {
+		t.Run(tc.desc, func(t *testing.T) {
+			wantBytes, err := hex.DecodeString(tc.want)
+			if err != nil {
+				t.Fatalf("hex.DecodeString(%x): %v", tc.want, err)
+			}
+			if got, want := tc.got, wantBytes; !bytes.Equal(got, want) {
+				t.Errorf("got %x, want %x", got, want)
+			}
+		})
+	}
+}
+
+func TestRFC6962HasherCollisions(t *testing.T) {
+	// Check that different leaves have different hashes.
+	leaf1, leaf2 := []byte("Hello"), []byte("World")
+	_, leafHashTrail := trailsFromByteSlices([][]byte{leaf1})
+	hash1 := leafHashTrail.Hash
+	_, leafHashTrail = trailsFromByteSlices([][]byte{leaf2})
+	hash2 := leafHashTrail.Hash
+	if bytes.Equal(hash1, hash2) {
+		t.Errorf("Leaf hashes should differ, but both are %x", hash1)
+	}
+
+	// Compute an intermediate subtree hash.
+	_, subHash1Trail := trailsFromByteSlices([][]byte{hash1, hash2})
+	subHash1 := subHash1Trail.Hash
+	// Check that this is not the same as a leaf hash of their concatenation.
+	preimage := append(hash1, hash2...)
+	_, forgedHashTrail := trailsFromByteSlices([][]byte{preimage})
+	forgedHash := forgedHashTrail.Hash
+	if bytes.Equal(subHash1, forgedHash) {
+		t.Errorf("Hasher is not second-preimage resistant")
+	}
+
+	// Swap the order of nodes and check that the hash is different.
+	_, subHash2Trail := trailsFromByteSlices([][]byte{hash2, hash1})
+	subHash2 := subHash2Trail.Hash
+	if bytes.Equal(subHash1, subHash2) {
+		t.Errorf("Subtree hash does not depend on the order of leaves")
+	}
+}

crypto/merkle/simple_proof.go

@@ -12,7 +12,7 @@ type SimpleProof struct {
 	Aunts [][]byte `json:"aunts"` // Hashes from leaf's sibling to a root's child.
 }
 
-// SimpleProofsFromHashers computes inclusion proof for given items.
+// SimpleProofsFromByteSlices computes inclusion proof for given items.
 // proofs[0] is the proof for items[0].
 func SimpleProofsFromByteSlices(items [][]byte) (rootHash []byte, proofs []*SimpleProof) {
 	trails, rootSPN := trailsFromByteSlices(items)

crypto/merkle/simple_tree.go

@@ -10,7 +10,7 @@ import (
 // SimpleHashFromTwoHashes is the basic operation of the Merkle tree: Hash(left | right).
 func SimpleHashFromTwoHashes(left, right []byte) []byte {
 	var hasher = tmhash.New()
-	_, err := hasher.Write([]byte{1})
+	_, err := hasher.Write(InnerHashPrefix)
 	if err != nil {
 		panic(err)
 	}

crypto/merkle/simple_tree_test.go

@@ -3,11 +3,12 @@ package merkle
 import (
 	"bytes"
 	"crypto/rand"
+	"testing"
+
+	"github.com/stretchr/testify/require"
 
 	cmn "github.com/tendermint/tendermint/libs/common"
 	. "github.com/tendermint/tendermint/libs/test"
-
-	"testing"
 )
 
 func TestSimpleProof(t *testing.T) {
@@ -81,3 +82,26 @@ func TestSimpleProof(t *testing.T) {
 		}
 	}
 }
+
+func Test_getSplitPoint(t *testing.T) {
+	tests := []struct {
+		length int
+		want   int
+	}{
+		{1, 0},
+		{2, 1},
+		{3, 2},
+		{4, 2},
+		{5, 4},
+		{10, 8},
+		{20, 16},
+		{100, 64},
+		{255, 128},
+		{256, 128},
+		{257, 256},
+	}
+	for _, tt := range tests {
+		got := getSplitPoint(tt.length)
+		require.Equal(t, tt.want, got, "getSplitPoint(%d) = %v, want %v", tt.length, got, tt.want)
+	}
+}