Question

我遵循了一些示例，并且在尝试实现此处引用的AES/GCM/NoPadding时：https://www.strongauth.com/samplecode/GCM.java我无法加密任何包含特殊字符（即ø）的文本。

最终它在doFinal内部失败，带有 javax.crypto.ShortBufferException: Output buffer must be (at least) 30 bytes long 但看来我一定做错了。我想念什么？

简单的POC：

public class Example {

    private static final String CIPHER_TRANSFORM = "AES/GCM/NoPadding";

    public static void main(String[] args) {

        String key = generateKey("AES", 256, "seed");
        encryptText("text containing a ø character", key, "TOKENTOKENTOKENTOKEN", "AES");
    }

    private static String generateKey(String alg, int size, String seed) {

        try {
            SecureRandom securerandom = SecureRandom.getInstance("SHA1PRNG");
            securerandom.setSeed(seed.getBytes("UTF-8"));
            KeyGenerator kg = KeyGenerator.getInstance(alg);
            kg.init(size, securerandom);
            SecretKey sk = kg.generateKey();
            return new String(Base64.getEncoder().encode(sk.getEncoded()), "UTF-8");
        }
        catch (UnsupportedEncodingException | NoSuchAlgorithmException ex) {
            System.err.println(ex);
        }
        return null;
    }

    private static String encryptText(String PLAINTEXT, String PLAINTEXTKEY, String TOKEN, String alg) {

        try {
            // Create SecretKey & Cipher
            SecretKeySpec sks = new SecretKeySpec(Base64.getDecoder().decode(PLAINTEXTKEY), alg);
            Cipher cipher = Cipher.getInstance(CIPHER_TRANSFORM);

            // Setup byte arrays
            byte[] input = PLAINTEXT.getBytes("UTF-8");
            byte[] tkb = TOKEN.getBytes("UTF-8");
            byte[] iv = new byte[12];
            System.arraycopy(tkb, 4, iv, 0, 12);
            cipher.init(Cipher.ENCRYPT_MODE, sks, new GCMParameterSpec(128, iv));
            cipher.updateAAD(tkb);
            byte[] opbytes = new byte[cipher.getOutputSize(PLAINTEXT.length())];

            // Perform crypto
            int ctlen = cipher.update(input, 0, input.length, opbytes);
            ctlen += cipher.doFinal(opbytes, ctlen);
            byte[] output = new byte[ctlen];
            System.arraycopy(opbytes, 0, output, 0, ctlen);
            return new String(Base64.getEncoder().encode(output), "UTF-8");

        }
        catch (InvalidAlgorithmParameterException | UnsupportedEncodingException |
            IllegalBlockSizeException | BadPaddingException | InvalidKeyException |
            NoSuchAlgorithmException | NoSuchPaddingException | ShortBufferException ex) {
            System.err.println(ex);
        }
        return null;
    }
}

Answer 1

您的问题是这一行：

byte[] opbytes = new byte[cipher.getOutputSize(PLAINTEXT.length())];

UTF-8符文中字符串的长度并不总是与基础字节数组的长度相同。您应该在此处使用input的长度，而不是PLAINTEXT。

Java AES / GCM / NoPadding加密失败，并带有特殊字符

1 个答案: