plugeth/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/>.
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package trie
import (
"bytes"
"fmt"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/log"
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"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.
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//
// 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.Writer) error {
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// Collect all nodes on the path to key.
key = keybytesToHex(key)
var nodes []node
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tn := t.root
for len(key) > 0 && tn != nil {
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switch n := tn.(type) {
case *shortNode:
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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):]
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}
nodes = append(nodes, n)
case *fullNode:
tn = n.Children[key[0]]
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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
}
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default:
panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
}
}
hasher := newHasher(nil)
defer returnHasherToPool(hasher)
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for i, n := range nodes {
// Don't bother checking for errors here since hasher panics
// if encoding doesn't work and we're not writing to any database.
n, _, _ = hasher.hashChildren(n, nil)
hn, _ := hasher.store(n, nil, false)
if hash, ok := hn.(hashNode); ok || i == 0 {
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// If the node's database encoding is a hash (or is the
// root node), it becomes a proof element.
if fromLevel > 0 {
fromLevel--
} else {
enc, _ := rlp.EncodeToBytes(n)
if !ok {
hash = hasher.makeHashNode(enc)
}
proofDb.Put(hash, enc)
}
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}
}
return nil
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}
// 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.Writer) 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.
//
// Note, the method assumes that all key-values in proofDb satisfy key = hash(value).
func VerifyProof(rootHash common.Hash, key []byte, proofDb ethdb.Reader) (value []byte, nodes int, err error) {
key = keybytesToHex(key)
wantHash := rootHash
for i := 0; ; i++ {
buf, _ := proofDb.Get(wantHash[:])
if buf == nil {
return nil, i, fmt.Errorf("proof node %d (hash %064x) missing", i, wantHash)
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}
n, err := decodeNode(wantHash[:], buf)
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if err != nil {
return nil, i, fmt.Errorf("bad proof node %d: %v", i, err)
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}
keyrest, cld := get(n, key)
switch cld := cld.(type) {
case nil:
// The trie doesn't contain the key.
return nil, i, nil
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case hashNode:
key = keyrest
copy(wantHash[:], cld)
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case valueNode:
return cld, i + 1, nil
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}
}
}
func get(tn node, key []byte) ([]byte, node) {
for {
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switch n := tn.(type) {
case *shortNode:
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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):]
case *fullNode:
tn = n.Children[key[0]]
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key = key[1:]
case hashNode:
return key, n
case nil:
return key, nil
case valueNode:
return nil, n
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default:
panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
}
}
}