trie: make stacktrie not mutate input values

trie/stacktrie.go

@@ -346,8 +346,7 @@ func (st *StackTrie) hash() {
 			panic(err)
 		}
 	case emptyNode:
-		st.val = st.val[:0]
-		st.val = append(st.val, emptyRoot[:]...)
+		st.val = emptyRoot.Bytes()
 		st.key = st.key[:0]
 		st.nodeType = hashedNode
 		return
@@ -357,17 +356,12 @@ func (st *StackTrie) hash() {
 	st.key = st.key[:0]
 	st.nodeType = hashedNode
 	if len(h.tmp) < 32 {
-		st.val = st.val[:0]
-		st.val = append(st.val, h.tmp...)
+		st.val = common.CopyBytes(h.tmp)
 		return
 	}
-	// Going to write the hash to the 'val'. Need to ensure it's properly sized first
-	// Typically, 'branchNode's will have no 'val', and require this allocation
-	if required := 32 - len(st.val); required > 0 {
-		buf := make([]byte, required)
-		st.val = append(st.val, buf...)
-	}
-	st.val = st.val[:32]
+	// Write the hash to the 'val'. We allocate a new val here to not mutate
+	// input values
+	st.val = make([]byte, 32)
 	h.sha.Reset()
 	h.sha.Write(h.tmp)
 	h.sha.Read(st.val)

trie/stacktrie_test.go

@@ -1,9 +1,12 @@
 package trie
 
 import (
+	"bytes"
+	"math/big"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/ethdb/memorydb"
 )
 
@@ -119,3 +122,51 @@ func TestUpdateVariableKeys(t *testing.T) {
 		t.Fatalf("error %x != %x", st.Hash(), nt.Hash())
 	}
 }
+
+// TestStacktrieNotModifyValues checks that inserting blobs of data into the
+// stacktrie does not mutate the blobs
+func TestStacktrieNotModifyValues(t *testing.T) {
+	st := NewStackTrie(nil)
+	{ // Test a very small trie
+		// Give it the value as a slice with large backing alloc,
+		// so if the stacktrie tries to append, it won't have to realloc
+		value := make([]byte, 1, 100)
+		value[0] = 0x2
+		want := common.CopyBytes(value)
+		st.TryUpdate([]byte{0x01}, value)
+		st.Hash()
+		if have := value; !bytes.Equal(have, want) {
+			t.Fatalf("tiny trie: have %#x want %#x", have, want)
+		}
+		st = NewStackTrie(nil)
+	}
+	// Test with a larger trie
+	keyB := big.NewInt(1)
+	keyDelta := big.NewInt(1)
+	var vals [][]byte
+	getValue := func(i int) []byte {
+		if i%2 == 0 { // large
+			return crypto.Keccak256(big.NewInt(int64(i)).Bytes())
+		} else { //small
+			return big.NewInt(int64(i)).Bytes()
+		}
+	}
+
+	for i := 0; i < 1000; i++ {
+		key := common.BigToHash(keyB)
+		value := getValue(i)
+		st.TryUpdate(key.Bytes(), value)
+		vals = append(vals, value)
+		keyB = keyB.Add(keyB, keyDelta)
+		keyDelta.Add(keyDelta, common.Big1)
+	}
+	st.Hash()
+	for i := 0; i < 1000; i++ {
+		want := getValue(i)
+
+		have := vals[i]
+		if !bytes.Equal(have, want) {
+			t.Fatalf("item %d, have %#x want %#x", i, have, want)
+		}
+	}
+}