"Invalid AES Block Size" SJCL解密

Question

尝试使用 RNCryptor-js which uses SJCL. After logging all the steps on each end, (other end is RNCryptor-python) 密钥、盐、HMAC 哈希来解密 AES，一切都匹配。但是当我进行到最后一步时：

var aes = new sjcl.cipher.aes(encryption_key);
sjcl.beware["CBC mode is dangerous because it doesn't protect message integrity."]()
var decrypted = aes.decrypt(ciphertext, iv);

我收到错误：

 sjcl.exception.invalid {toString: function, message: "invalid aes block size"}

完整代码如下：

PBKDF2:

this.KeyForPassword = function(password, salt) {

  var hmacSHA256 = function (password) {
      var hasher = new sjcl.misc.hmac(password, sjcl.hash.sha256);
      this.encrypt = function () {
          return hasher.encrypt.apply(hasher, arguments);
      };
  };
  return sjcl.misc.pbkdf2(password, salt, 10000, 32 * 8, hmacSHA256);
};

解密（输入十六进制）：

this.decrypt = function(password, message, options) {

  message = sjcl.codec.hex.toBits(message);

  options = options || {};

  var version = sjcl.bitArray.extract(message, 0 * 8, 8);
  var options = sjcl.bitArray.extract(message, 1 * 8, 8);

  var encryption_salt = sjcl.bitArray.bitSlice(message, 2 * 8, 10 * 8);
  var encryption_key = _this.KeyForPassword(password, encryption_salt, "decryption");

  var hmac_salt = sjcl.bitArray.bitSlice(message, 10 * 8, 18 * 8);
  var hmac_key = _this.KeyForPassword(password, hmac_salt, "decryption");

  var iv = sjcl.bitArray.bitSlice(message, 18 * 8, 34 * 8);

  var ciphertext_end = sjcl.bitArray.bitLength(message) - (32 * 8);
  var ciphertext = sjcl.bitArray.bitSlice(message, 34 * 8, ciphertext_end);

  var hmac = sjcl.bitArray.bitSlice(message, ciphertext_end);
  var expected_hmac = new sjcl.misc.hmac(hmac_key).encrypt(sjcl.bitArray.bitSlice(message, 0, ciphertext_end));

  if (! sjcl.bitArray.equal(hmac, expected_hmac)) {
    throw new sjcl.exception.corrupt("HMAC mismatch or bad password.");
  }

  var aes = new sjcl.cipher.aes(encryption_key);
  sjcl.beware["CBC mode is dangerous because it doesn't protect message integrity."]()
  var decrypted = aes.decrypt(ciphertext, iv);

  return decrypted;
}

在定义 decrypted 的倒数第二个语句中抛出错误。

我查看了 sjcl 异常，看起来它正在寻找长度为 4 的输入，我猜它是一个 WordArray。我只是不知道如何获得有效输入。就像我说的，密文、iv、hmac 标签、盐都在 javascript 端被正确切割。可能只是编码问题。

这个错误似乎也只发生在 json（格式：'{"key":"value"}'），当我尝试像 "Hello, world" 我得到一个没有错误的 4 字数组。

有什么建议吗？

Answer 1

 var decrypted = aes.decrypt(ciphertext, iv);

应该是

 var decrypted = sjcl.mode.cbc.decrypt(aes, ciphertext, iv);

我在 cbc.js (link to source) and it turned out that I hadn't included bitArray.js (link) 中也遇到了填充问题，其中包含一个重要的 xor 函数（不要与简单的 ^ 运算符混淆）。

所以：包括bitArray.js

输出也应该被编码：

return sjcl.codec.utf8String.fromBits(decrypted);

"Invalid AES Block Size" SJCL解密

"Invalid AES Block Size" SJCL Decryption

javascript

python

encryption

sjcl

rncryptor