java - 将 JSON 与 AES 一起使用会引发 javax.crypto.IllegalBlockSizeException

Question

当我使用 AES/CBC/PKCS5Padding 加密普通的 String 时，没有问题。

当我使用包含典型 JSON 类型数据的 JSON String 时，它在执行解密时抛出异常:

完全异常:

Exception in thread "main" javax.crypto.IllegalBlockSizeException: Input length must be multiple of 16 when decrypting with padded cipher
    at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:936)
    at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:847)
    at com.sun.crypto.provider.AESCipher.engineDoFinal(AESCipher.java:446)
    at javax.crypto.Cipher.doFinal(Cipher.java:2165)
    at io.crypto.Crypto.doFinal(Crypto.java:60)
    at io.crypto.Crypto.decrypt(Crypto.java:50)
    at io.Controller.main(Controller.java:38)

AES 代码:

public class Crypto {

    private static final char[] HEX = new char[]{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'b', 'c', 'D', 'e', 'F'};
    private static Cipher cipher;

    public static void init() {

        try {
            cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        } catch (NoSuchPaddingException | NoSuchAlgorithmException e) {
            NetworkModule.handleException(e);
        }

    }

    public static String encrypt(String password, String message) throws Exception {

        String salt = random(16);
        String iv = random(16);
        SecretKey key = generateKey(salt, password);
        byte[] encrypted = doFinal(Cipher.ENCRYPT_MODE, key, iv, message.getBytes("UTF-8"));
        String code = Base64.getEncoder().encodeToString(encrypted);
        return salt + code.substring(0, code.length() - 2) + iv;

    }

    public static String decrypt(String password, String message) throws Exception {

        String salt = message.substring(0, 32);
        String iv = message.substring(message.length() - 32, message.length());
        String base = message.substring(32, message.length() - 32) + "==";
        SecretKey key = generateKey(salt, password);
        byte[] decrypted = doFinal(Cipher.DECRYPT_MODE, key, iv, Base64.getDecoder().decode(base));
        return new String(decrypted, "UTF-8");

    }

    private static byte[] doFinal(int encryptMode, SecretKey key, String iv, byte[] bytes) {

        try {

            cipher.init(encryptMode, key, new IvParameterSpec(hex(iv)));
            return cipher.doFinal(bytes);

        } catch (InvalidKeyException | InvalidAlgorithmParameterException | IllegalBlockSizeException | BadPaddingException e) {
            NetworkModule.handleException(e);
            return null;
        }

    }

    private static SecretKey generateKey(String salt, String passphrase) {

        try {

            SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
            KeySpec spec = new PBEKeySpec(passphrase.toCharArray(), hex(salt), 1000, 128);
            SecretKey key = new SecretKeySpec(factory.generateSecret(spec).getEncoded(), "AES");
            return key;

        } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
            NetworkModule.handleException(e);
            return null;
        }

    }

    private static String random(int length) {
        byte[] salt = new byte[length];
        new SecureRandom().nextBytes(salt);
        return hex(salt);
    }

    private static String hex(byte[] data) {

        int l = data.length;
        char[] out = new char[l << 1];
        int i = 0;

        for (int var5 = 0; i < l; ++i) {
            out[var5++] = HEX[(240 & data[i]) >>> 4];
            out[var5++] = HEX[15 & data[i]];
        }

        return new String(out);

    }

    private static byte[] hex(String hex) {

        char[] data = hex.toCharArray();
        int len = data.length;

        if ((len & 1) != 0) {
            return null;
        } else {

            byte[] out = new byte[len >> 1];
            int i = 0;

            for (int j = 0; j < len; ++i) {

                int f = Character.digit(data[j], 16) << 4;
                ++j;
                f |= Character.digit(data[j], 16);
                ++j;
                out[i] = (byte) (f & 255);

            }

            return out;

        }

    }

}

工作示例:

Crypto.init();
String password = "42cb54a0b6a89a53709301ee320f45de102dda05ccd1a49c3c62c19b7319ca73";
String message = "Hello World";
System.out.println(message);
String encrypt = Crypto.encrypt(password, message);
System.out.println(encrypt);
String decrypt = Crypto.decrypt(password, encrypt);
System.out.println(decrypt);

输出:

Hello World
3cc6b607175011Fc50bb498c8064863ebbAePnO7nmGSFLBr2KnfhQDAb84b338007b4e3e9bbFF3e35b0341A
Hello World

异常示例:

Crypto.init();
String password = "42cb54a0b6a89a53709301ee320f45de102dda05ccd1a49c3c62c19b7319ca73";
String message = new PacketBuilder("example").build();
System.out.println(message);
String encrypt = Crypto.encrypt(password, message);
System.out.println(encrypt);
String decrypt = Crypto.decrypt(password, encrypt);
System.out.println(decrypt);

输出:

{"packet":"EXAMPLE"}
6b1FbA86e4F17A21633AA12c352eAD63ebKIw+ljAx4XsqBgK5Q3KQ2Hd5w8nO4NP9sqxC+CLI0A4D2e4AbF47ecF6b6149A8F2445658F
Exception in thread "main" ... full stacktrace on the top of the post

Answer 1

好的，我已经找到问题了。

在检查变量时，我发现在加密方法中打印代码会产生一个以单个空格结尾的字符串。但是，您切断了子字符串中的两个字母，因此您需要做的第一件事就是在该方法中重写您的返回，如下所示

        return salt + code.replace("=","") + iv;

接下来，每当您要从基础解码时，您都会执行此操作

        String base = message.substring(32, message.length() - 32) + "==";

但这不是必需的，所以像这样改变它

        String base = message.substring(32, message.length() - 32);

更改这些后，您的方法应该可以工作。