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// Copyright 2018 The go-ethereum Authors
// This file is part of go-ethereum.
//
// go-ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// go-ethereum 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
//
package storage
import (
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"encoding/json"
"io"
"io/ioutil"
"os"
"github.com/ethereum/go-ethereum/log"
)
type storedCredential struct {
// The iv
Iv []byte `json:"iv"`
// The ciphertext
CipherText []byte `json:"c"`
}
// AESEncryptedStorage is a storage type which is backed by a json-file. The json-file contains
// key-value mappings, where the keys are _not_ encrypted, only the values are.
type AESEncryptedStorage struct {
// File to read/write credentials
filename string
// Key stored in base64
key []byte
}
// NewAESEncryptedStorage creates a new encrypted storage backed by the given file/key
func NewAESEncryptedStorage(filename string, key []byte) *AESEncryptedStorage {
return &AESEncryptedStorage{
filename: filename,
key: key,
}
}
// Put stores a value by key. 0-length keys results in no-op
func (s *AESEncryptedStorage) Put(key, value string) {
if len(key) == 0 {
return
}
data, err := s.readEncryptedStorage()
if err != nil {
log.Warn("Failed to read encrypted storage", "err", err, "file", s.filename)
return
}
ciphertext, iv, err := encrypt(s.key, []byte(value), []byte(key))
if err != nil {
log.Warn("Failed to encrypt entry", "err", err)
return
}
encrypted := storedCredential{Iv: iv, CipherText: ciphertext}
data[key] = encrypted
if err = s.writeEncryptedStorage(data); err != nil {
log.Warn("Failed to write entry", "err", err)
}
}
// Get returns the previously stored value, or the empty string if it does not exist or key is of 0-length
func (s *AESEncryptedStorage) Get(key string) string {
if len(key) == 0 {
return ""
}
data, err := s.readEncryptedStorage()
if err != nil {
log.Warn("Failed to read encrypted storage", "err", err, "file", s.filename)
return ""
}
encrypted, exist := data[key]
if !exist {
log.Warn("Key does not exist", "key", key)
return ""
}
entry, err := decrypt(s.key, encrypted.Iv, encrypted.CipherText, []byte(key))
if err != nil {
log.Warn("Failed to decrypt key", "key", key)
return ""
}
return string(entry)
}
// readEncryptedStorage reads the file with encrypted creds
func (s *AESEncryptedStorage) readEncryptedStorage() (map[string]storedCredential, error) {
creds := make(map[string]storedCredential)
raw, err := ioutil.ReadFile(s.filename)
if err != nil {
if os.IsNotExist(err) {
// Doesn't exist yet
return creds, nil
}
log.Warn("Failed to read encrypted storage", "err", err, "file", s.filename)
}
if err = json.Unmarshal(raw, &creds); err != nil {
log.Warn("Failed to unmarshal encrypted storage", "err", err, "file", s.filename)
return nil, err
}
return creds, nil
}
// writeEncryptedStorage write the file with encrypted creds
func (s *AESEncryptedStorage) writeEncryptedStorage(creds map[string]storedCredential) error {
raw, err := json.Marshal(creds)
if err != nil {
return err
}
if err = ioutil.WriteFile(s.filename, raw, 0600); err != nil {
return err
}
return nil
}
// encrypt encrypts plaintext with the given key, with additional data
// The 'additionalData' is used to place the (plaintext) KV-store key into the V,
// to prevent the possibility to alter a K, or swap two entries in the KV store with eachother.
func encrypt(key []byte, plaintext []byte, additionalData []byte) ([]byte, []byte, error) {
block, err := aes.NewCipher(key)
if err != nil {
return nil, nil, err
}
aesgcm, err := cipher.NewGCM(block)
nonce := make([]byte, aesgcm.NonceSize())
if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
return nil, nil, err
}
if err != nil {
return nil, nil, err
}
ciphertext := aesgcm.Seal(nil, nonce, plaintext, additionalData)
return ciphertext, nonce, nil
}
func decrypt(key []byte, nonce []byte, ciphertext []byte, additionalData []byte) ([]byte, error) {
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
aesgcm, err := cipher.NewGCM(block)
if err != nil {
return nil, err
}
plaintext, err := aesgcm.Open(nil, nonce, ciphertext, additionalData)
if err != nil {
return nil, err
}
return plaintext, nil
}
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