109 lines
3.4 KiB
Go
109 lines
3.4 KiB
Go
// 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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package trie
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import (
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"hash"
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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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)
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var secureKeyPrefix = []byte("secure-key-")
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// SecureTrie wraps a trie with key hashing. In a secure trie, all
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// access operations hash the key using keccak256. This prevents
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// calling code from creating long chains of nodes that
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// increase the access time.
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//
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// Contrary to a regular trie, a SecureTrie can only be created with
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// New and must have an attached database. The database also stores
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// the preimage of each key.
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//
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// SecureTrie is not safe for concurrent use.
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type SecureTrie struct {
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*Trie
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hash hash.Hash
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secKeyBuf []byte
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hashKeyBuf []byte
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}
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// NewSecure creates a trie with an existing root node from db.
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//
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// If root is the zero hash or the sha3 hash of an empty string, the
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// trie is initially empty. Otherwise, New will panics if db is nil
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// and returns ErrMissingRoot if the root node cannpt be found.
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// Accessing the trie loads nodes from db on demand.
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func NewSecure(root common.Hash, db Database) (*SecureTrie, error) {
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if db == nil {
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panic("NewSecure called with nil database")
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}
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trie, err := New(root, db)
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if err != nil {
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return nil, err
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}
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return &SecureTrie{Trie: trie}, nil
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}
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// Get returns the value for key stored in the trie.
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// The value bytes must not be modified by the caller.
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func (t *SecureTrie) Get(key []byte) []byte {
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return t.Trie.Get(t.hashKey(key))
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}
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// Update associates key with value in the trie. Subsequent calls to
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// Get will return value. If value has length zero, any existing value
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// is deleted from the trie and calls to Get will return nil.
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//
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// The value bytes must not be modified by the caller while they are
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// stored in the trie.
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func (t *SecureTrie) Update(key, value []byte) {
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hk := t.hashKey(key)
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t.Trie.Update(hk, value)
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t.Trie.db.Put(t.secKey(hk), key)
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}
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// Delete removes any existing value for key from the trie.
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func (t *SecureTrie) Delete(key []byte) {
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t.Trie.Delete(t.hashKey(key))
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}
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// GetKey returns the sha3 preimage of a hashed key that was
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// previously used to store a value.
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func (t *SecureTrie) GetKey(shaKey []byte) []byte {
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key, _ := t.Trie.db.Get(t.secKey(shaKey))
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return key
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}
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func (t *SecureTrie) secKey(key []byte) []byte {
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t.secKeyBuf = append(t.secKeyBuf[:0], secureKeyPrefix...)
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t.secKeyBuf = append(t.secKeyBuf, key...)
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return t.secKeyBuf
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}
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func (t *SecureTrie) hashKey(key []byte) []byte {
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if t.hash == nil {
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t.hash = sha3.NewKeccak256()
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t.hashKeyBuf = make([]byte, 32)
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}
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t.hash.Reset()
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t.hash.Write(key)
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t.hashKeyBuf = t.hash.Sum(t.hashKeyBuf[:0])
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return t.hashKeyBuf
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}
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