2016-04-14 09:18:24 -07:00
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// Copyright 2015 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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2015-09-08 18:35:41 -07:00
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package trie
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import (
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"bytes"
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"errors"
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"fmt"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/crypto/sha3"
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2015-11-25 09:28:21 -08:00
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"github.com/ethereum/go-ethereum/logger"
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"github.com/ethereum/go-ethereum/logger/glog"
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2015-09-08 18:35:41 -07:00
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"github.com/ethereum/go-ethereum/rlp"
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)
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// Prove constructs a merkle proof for key. The result contains all
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// encoded nodes on the path to the value at key. The value itself is
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// also included in the last node and can be retrieved by verifying
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// the proof.
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//
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2015-11-30 04:34:19 -08:00
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// If the trie does not contain a value for key, the returned proof
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// contains all nodes of the longest existing prefix of the key
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// (at least the root node), ending with the node that proves the
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// absence of the key.
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func (t *Trie) Prove(key []byte) []rlp.RawValue {
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// Collect all nodes on the path to key.
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key = compactHexDecode(key)
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nodes := []node{}
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tn := t.root
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for len(key) > 0 && tn != nil {
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switch n := tn.(type) {
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2016-10-14 09:04:33 -07:00
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case *shortNode:
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2015-09-08 18:35:41 -07:00
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if len(key) < len(n.Key) || !bytes.Equal(n.Key, key[:len(n.Key)]) {
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// The trie doesn't contain the key.
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tn = nil
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} else {
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tn = n.Val
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key = key[len(n.Key):]
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}
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nodes = append(nodes, n)
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case *fullNode:
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tn = n.Children[key[0]]
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key = key[1:]
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nodes = append(nodes, n)
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case hashNode:
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2015-11-25 09:28:21 -08:00
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var err error
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tn, err = t.resolveHash(n, nil, nil)
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if err != nil {
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if glog.V(logger.Error) {
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glog.Errorf("Unhandled trie error: %v", err)
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}
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return nil
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}
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default:
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panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
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}
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}
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2016-10-14 09:04:33 -07:00
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hasher := newHasher(0, 0)
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proof := make([]rlp.RawValue, 0, len(nodes))
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for i, n := range nodes {
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// Don't bother checking for errors here since hasher panics
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// if encoding doesn't work and we're not writing to any database.
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2016-09-25 11:49:02 -07:00
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n, _, _ = hasher.hashChildren(n, nil)
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hn, _ := hasher.store(n, nil, false)
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if _, ok := hn.(hashNode); ok || i == 0 {
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// If the node's database encoding is a hash (or is the
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// root node), it becomes a proof element.
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enc, _ := rlp.EncodeToBytes(n)
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proof = append(proof, enc)
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}
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}
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return proof
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}
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// VerifyProof checks merkle proofs. The given proof must contain the
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// value for key in a trie with the given root hash. VerifyProof
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// returns an error if the proof contains invalid trie nodes or the
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// wrong value.
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func VerifyProof(rootHash common.Hash, key []byte, proof []rlp.RawValue) (value []byte, err error) {
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key = compactHexDecode(key)
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sha := sha3.NewKeccak256()
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wantHash := rootHash.Bytes()
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for i, buf := range proof {
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sha.Reset()
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sha.Write(buf)
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if !bytes.Equal(sha.Sum(nil), wantHash) {
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return nil, fmt.Errorf("bad proof node %d: hash mismatch", i)
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}
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n, err := decodeNode(wantHash, buf)
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if err != nil {
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return nil, fmt.Errorf("bad proof node %d: %v", i, err)
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}
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keyrest, cld := get(n, key)
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switch cld := cld.(type) {
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case nil:
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if i != len(proof)-1 {
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return nil, fmt.Errorf("key mismatch at proof node %d", i)
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} else {
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// The trie doesn't contain the key.
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return nil, nil
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}
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case hashNode:
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key = keyrest
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wantHash = cld
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case valueNode:
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if i != len(proof)-1 {
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return nil, errors.New("additional nodes at end of proof")
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}
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return cld, nil
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}
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}
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return nil, errors.New("unexpected end of proof")
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}
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func get(tn node, key []byte) ([]byte, node) {
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for len(key) > 0 {
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switch n := tn.(type) {
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case *shortNode:
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if len(key) < len(n.Key) || !bytes.Equal(n.Key, key[:len(n.Key)]) {
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return nil, nil
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}
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tn = n.Val
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key = key[len(n.Key):]
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2016-10-14 09:04:33 -07:00
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case *fullNode:
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2016-05-19 03:24:14 -07:00
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tn = n.Children[key[0]]
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2015-09-08 18:35:41 -07:00
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key = key[1:]
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case hashNode:
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return key, n
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case nil:
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return key, nil
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default:
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panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
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}
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}
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return nil, tn.(valueNode)
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}
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