Official Go implementation of the Ethereum protocol
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go-ethereum/trie/proof.go

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// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package trie
import (
"bytes"
"errors"
"fmt"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/ethdb/memorydb"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/rlp"
)
// Prove constructs a merkle proof for key. The result contains all encoded nodes
// on the path to the value at key. The value itself is also included in the last
// node and can be retrieved by verifying the proof.
//
// If the trie does not contain a value for key, the returned proof contains all
// nodes of the longest existing prefix of the key (at least the root node), ending
// with the node that proves the absence of the key.
func (t *Trie) Prove(key []byte, fromLevel uint, proofDb ethdb.KeyValueWriter) error {
// Collect all nodes on the path to key.
key = keybytesToHex(key)
var nodes []node
tn := t.root
for len(key) > 0 && tn != nil {
switch n := tn.(type) {
case *shortNode:
if len(key) < len(n.Key) || !bytes.Equal(n.Key, key[:len(n.Key)]) {
// The trie doesn't contain the key.
tn = nil
} else {
tn = n.Val
key = key[len(n.Key):]
}
nodes = append(nodes, n)
case *fullNode:
tn = n.Children[key[0]]
key = key[1:]
nodes = append(nodes, n)
case hashNode:
var err error
tn, err = t.resolveHash(n, nil)
if err != nil {
log.Error(fmt.Sprintf("Unhandled trie error: %v", err))
return err
}
default:
panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
}
}
hasher := newHasher(false)
defer returnHasherToPool(hasher)
for i, n := range nodes {
if fromLevel > 0 {
fromLevel--
continue
}
var hn node
n, hn = hasher.proofHash(n)
if hash, ok := hn.(hashNode); ok || i == 0 {
// If the node's database encoding is a hash (or is the
// root node), it becomes a proof element.
enc, _ := rlp.EncodeToBytes(n)
if !ok {
hash = hasher.hashData(enc)
}
proofDb.Put(hash, enc)
}
}
return nil
}
// Prove constructs a merkle proof for key. The result contains all encoded nodes
// on the path to the value at key. The value itself is also included in the last
// node and can be retrieved by verifying the proof.
//
// If the trie does not contain a value for key, the returned proof contains all
// nodes of the longest existing prefix of the key (at least the root node), ending
// with the node that proves the absence of the key.
func (t *SecureTrie) Prove(key []byte, fromLevel uint, proofDb ethdb.KeyValueWriter) error {
return t.trie.Prove(key, fromLevel, proofDb)
}
// VerifyProof checks merkle proofs. The given proof must contain the value for
// key in a trie with the given root hash. VerifyProof returns an error if the
// proof contains invalid trie nodes or the wrong value.
func VerifyProof(rootHash common.Hash, key []byte, proofDb ethdb.KeyValueReader) (value []byte, err error) {
key = keybytesToHex(key)
wantHash := rootHash
for i := 0; ; i++ {
buf, _ := proofDb.Get(wantHash[:])
if buf == nil {
return nil, fmt.Errorf("proof node %d (hash %064x) missing", i, wantHash)
}
n, err := decodeNode(wantHash[:], buf)
if err != nil {
return nil, fmt.Errorf("bad proof node %d: %v", i, err)
}
keyrest, cld := get(n, key, true)
switch cld := cld.(type) {
case nil:
// The trie doesn't contain the key.
return nil, nil
case hashNode:
key = keyrest
copy(wantHash[:], cld)
case valueNode:
return cld, nil
}
}
}
// proofToPath converts a merkle proof to trie node path.
// The main purpose of this function is recovering a node
// path from the merkle proof stream. All necessary nodes
// will be resolved and leave the remaining as hashnode.
func proofToPath(rootHash common.Hash, root node, key []byte, proofDb ethdb.KeyValueReader) (node, error) {
// resolveNode retrieves and resolves trie node from merkle proof stream
resolveNode := func(hash common.Hash) (node, error) {
buf, _ := proofDb.Get(hash[:])
if buf == nil {
return nil, fmt.Errorf("proof node (hash %064x) missing", hash)
}
n, err := decodeNode(hash[:], buf)
if err != nil {
return nil, fmt.Errorf("bad proof node %v", err)
}
return n, err
}
// If the root node is empty, resolve it first
if root == nil {
n, err := resolveNode(rootHash)
if err != nil {
return nil, err
}
root = n
}
var (
err error
child, parent node
keyrest []byte
terminate bool
)
key, parent = keybytesToHex(key), root
for {
keyrest, child = get(parent, key, false)
switch cld := child.(type) {
case nil:
// The trie doesn't contain the key.
return nil, errors.New("the node is not contained in trie")
case *shortNode:
key, parent = keyrest, child // Already resolved
continue
case *fullNode:
key, parent = keyrest, child // Already resolved
continue
case hashNode:
child, err = resolveNode(common.BytesToHash(cld))
if err != nil {
return nil, err
}
case valueNode:
terminate = true
}
// Link the parent and child.
switch pnode := parent.(type) {
case *shortNode:
pnode.Val = child
case *fullNode:
pnode.Children[key[0]] = child
default:
panic(fmt.Sprintf("%T: invalid node: %v", pnode, pnode))
}
if terminate {
return root, nil // The whole path is resolved
}
key, parent = keyrest, child
}
}
// unsetInternal removes all internal node references(hashnode, embedded node).
// It should be called after a trie is constructed with two edge proofs. Also
// the given boundary keys must be the one used to construct the edge proofs.
//
// It's the key step for range proof. All visited nodes should be marked dirty
// since the node content might be modified. Besides it can happen that some
// fullnodes only have one child which is disallowed. But if the proof is valid,
// the missing children will be filled, otherwise it will be thrown anyway.
func unsetInternal(node node, left []byte, right []byte) error {
left, right = keybytesToHex(left), keybytesToHex(right)
// todo(rjl493456442) different length edge keys should be supported
if len(left) != len(right) {
return errors.New("inconsistent edge path")
}
// Step down to the fork point
prefix, pos := prefixLen(left, right), 0
for {
if pos >= prefix {
break
}
switch n := (node).(type) {
case *shortNode:
if len(left)-pos < len(n.Key) || !bytes.Equal(n.Key, left[pos:pos+len(n.Key)]) {
return errors.New("invalid edge path")
}
n.flags = nodeFlag{dirty: true}
node, pos = n.Val, pos+len(n.Key)
case *fullNode:
n.flags = nodeFlag{dirty: true}
node, pos = n.Children[left[pos]], pos+1
default:
panic(fmt.Sprintf("%T: invalid node: %v", node, node))
}
}
fn, ok := node.(*fullNode)
if !ok {
return errors.New("the fork point must be a fullnode")
}
// Find the fork point! Unset all intermediate references
for i := left[prefix] + 1; i < right[prefix]; i++ {
fn.Children[i] = nil
}
fn.flags = nodeFlag{dirty: true}
unset(fn.Children[left[prefix]], left[prefix+1:], false)
unset(fn.Children[right[prefix]], right[prefix+1:], true)
return nil
}
// unset removes all internal node references either the left most or right most.
func unset(root node, rest []byte, removeLeft bool) {
switch rn := root.(type) {
case *fullNode:
if removeLeft {
for i := 0; i < int(rest[0]); i++ {
rn.Children[i] = nil
}
rn.flags = nodeFlag{dirty: true}
} else {
for i := rest[0] + 1; i < 16; i++ {
rn.Children[i] = nil
}
rn.flags = nodeFlag{dirty: true}
}
unset(rn.Children[rest[0]], rest[1:], removeLeft)
case *shortNode:
rn.flags = nodeFlag{dirty: true}
if _, ok := rn.Val.(valueNode); ok {
rn.Val = nilValueNode
return
}
unset(rn.Val, rest[len(rn.Key):], removeLeft)
case hashNode, nil, valueNode:
panic("it shouldn't happen")
}
}
// VerifyRangeProof checks whether the given leave nodes and edge proofs
// can prove the given trie leaves range is matched with given root hash
// and the range is consecutive(no gap inside).
func VerifyRangeProof(rootHash common.Hash, keys [][]byte, values [][]byte, firstProof ethdb.KeyValueReader, lastProof ethdb.KeyValueReader) error {
if len(keys) != len(values) {
return fmt.Errorf("inconsistent proof data, keys: %d, values: %d", len(keys), len(values))
}
if len(keys) == 0 {
return fmt.Errorf("nothing to verify")
}
if len(keys) == 1 {
value, err := VerifyProof(rootHash, keys[0], firstProof)
if err != nil {
return err
}
if !bytes.Equal(value, values[0]) {
return fmt.Errorf("correct proof but invalid data")
}
return nil
}
// Convert the edge proofs to edge trie paths. Then we can
// have the same tree architecture with the original one.
root, err := proofToPath(rootHash, nil, keys[0], firstProof)
if err != nil {
return err
}
// Pass the root node here, the second path will be merged
// with the first one.
root, err = proofToPath(rootHash, root, keys[len(keys)-1], lastProof)
if err != nil {
return err
}
// Remove all internal references. All the removed parts should
// be re-filled(or re-constructed) by the given leaves range.
if err := unsetInternal(root, keys[0], keys[len(keys)-1]); err != nil {
return err
}
// Rebuild the trie with the leave stream, the shape of trie
// should be same with the original one.
newtrie := &Trie{root: root, db: NewDatabase(memorydb.New())}
for index, key := range keys {
newtrie.TryUpdate(key, values[index])
}
if newtrie.Hash() != rootHash {
return fmt.Errorf("invalid proof, wanthash %x, got %x", rootHash, newtrie.Hash())
}
return nil
}
// get returns the child of the given node. Return nil if the
// node with specified key doesn't exist at all.
//
// There is an additional flag `skipResolved`. If it's set then
// all resolved nodes won't be returned.
func get(tn node, key []byte, skipResolved bool) ([]byte, node) {
for {
switch n := tn.(type) {
case *shortNode:
if len(key) < len(n.Key) || !bytes.Equal(n.Key, key[:len(n.Key)]) {
return nil, nil
}
tn = n.Val
key = key[len(n.Key):]
if !skipResolved {
return key, tn
}
case *fullNode:
tn = n.Children[key[0]]
key = key[1:]
if !skipResolved {
return key, tn
}
case hashNode:
return key, n
case nil:
return key, nil
case valueNode:
return nil, n
default:
panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
}
}
}