如何解密AES加密文件与'-no盐'参数

Question

我是加密新手。这个问题是我上一个问题的子问题。我有一个用OpenSSL util加密的文件：

openssl aes-256-cbc -in fileIn -out fileOUT -p -k KEY

我用这个代码来解密它：

        byte[] encrypted = IOUtils.toByteArray(inputStream);
        Security.addProvider(new BouncyCastleProvider());

        String password = "abc";

        Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding", "BC");

        // Openssl puts SALTED__ then the 8 byte salt at the start of the
        // file. We simply copy it out.
        byte[] salt = new byte[8];
        System.arraycopy(encrypted, 8, salt, 0, 8);
        SecretKeyFactory fact = SecretKeyFactory.getInstance(
                "PBEWITHMD5AND256BITAES-CBC-OPENSSL", "BC");
        c.init(Cipher.DECRYPT_MODE, fact.generateSecret(new PBEKeySpec(
                password.toCharArray(), salt, 100)));

        // Decrypt the rest of the byte array (after stripping off the salt)
        byte[] data = c.doFinal(encrypted, 16, encrypted.length - 16);

而且很有效。但这是一个测试案例。实际情况是，我用以下参数对文件进行了加密：

openssl aes-256-cbc-nosalt-in fileIn-out fileOUT-p-k KEY

请注意，出现了'-no盐'参数。问题是PBEKeySpec需要不为空，也不为空的盐和迭代计数参数。它也有没有这些参数的构造函数，但是如果我使用它，我会得到一个错误：

02-11 11:25:06.108:W/系统。err（2155）：java。安全InvalidKeyException:PBE要求设置PBE参数。

问题是如何解密这些文件？如何正确处理'-nosalt'参数？

Answer 1

使用空盐而不是空盐，并相应地设置偏移量

Security.addProvider(new BouncyCastleProvider());

final char[] password = "pass".toCharArray();
final int saltLength = 8;
final String saltedPrefix = "Salted__";

String[] files = { "file0.txt.enc", "file0.txt.enc.nosalt" };
for (String file : files) {
    byte[] encrypted = Files.readAllBytes(Paths.get("testData", "openssl", file));

    byte[] salt = new byte[0];
    int offset = 0;
    if (new String(encrypted, 0, saltLength, "ASCII").equals(saltedPrefix)) {
        salt = new byte[saltLength];
        System.arraycopy(encrypted, saltedPrefix.length(), salt, 0, saltLength);
        offset = saltedPrefix.length() + saltLength;
    }

    SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWITHMD5AND256BITAES-CBC-OPENSSL", "BC");
    PBEKeySpec keySpec = new PBEKeySpec(password);
    PBEParameterSpec paramSpec = new PBEParameterSpec(salt, 0);
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding", "BC");
    cipher.init(Cipher.DECRYPT_MODE, keyFactory.generateSecret(keySpec), paramSpec);

    byte[] data = cipher.doFinal(encrypted, offset, encrypted.length- offset);
    System.out.println(new String(data));
}