使用 Java 的 AES-256-GCM 解密中的标签不匹配错误

2022-01-10 00:00:00 cryptography javascript aes-gcm java

我有以下用 Javascript 编写的函数，用于使用 aes-256-gcm 进行加密:

I have the following function written in Javascript for encryption using aes-256-gcm:

encrypt: function (text, masterkey){
    try {
        // random initialization vector
        var iv = crypto.randomBytes(12);

        // random salt
        var salt = crypto.randomBytes(64);

        // derive key: 32 byte key length - in assumption the masterkey is a cryptographic and NOT a password there is no need for
        // a large number of iterations. It may can replaced by HKDF
        var key = crypto.pbkdf2Sync(masterkey, salt, 2145, 32, 'sha512');

        // AES 256 GCM Mode
        var cipher = crypto.createCipheriv('aes-256-gcm', key, iv);

        // encrypt the given text
        var encrypted = Buffer.concat([cipher.update(text, 'utf8'), cipher.final()]);

        // extract the auth tag
        var tag = cipher.getAuthTag();

        // generate output
        return Buffer.concat([salt, iv, tag, encrypted]).toString('base64');

    }catch(e){
    }

    // error
    return null;
}

上述函数的加密文本使用以下函数成功解密回来:

The encrypted text by the above function is successfully decrypted back using the following function:

decrypt: function (data, masterkey){
    try {
        // base64 decoding
        var bData = new Buffer(data, 'base64');
        var salt = bData.slice(0, 64);
        var iv = bData.slice(64, 76);
        var tag = bData.slice(76, 92);
        var text = bData.slice(92);

        // derive key using; 32 byte key length
        var key = crypto.pbkdf2Sync(masterkey, salt , 2145, 32, 'sha512');
        // AES 256 GCM Mode
        var decipher = crypto.createDecipheriv('aes-256-gcm', key, iv);
        decipher.setAuthTag(tag);

        // decrypt the given text
        var decrypted = decipher.update(text, 'binary', 'utf8') + decipher.final('utf8');

        return decrypted;

    }catch(e){
    }

    // error
    return null;
}

现在，我需要一个 Java 中的解密方法，它相当于上面的 Javascript 解密函数.以下是我为解密编写的Java代码:

Now, I need a method in Java for decryption which is the equivalent of the above Javascript decrypt function. Following is the Java code I have written for decryption:

public void decrypt(byte[] nkb, String crKey){
    //nkb is byte array formed by Base64 decoding of 'data' variable in the Javascript code
    //crKey corresponds to the 'masterkey' variable

    byte[] salt = Arrays.copyOfRange(nkb, 0, 64);
    byte[] iv = Arrays.copyOfRange(nkb, 64, 76);
    byte[] tag = Arrays.copyOfRange(nkb, 76, 92);
    byte[] text = Arrays.copyOfRange(nkb, 92, nkb.length);

    PBEKeySpec ks = new PBEKeySpec(crKey.toCharArray(), salt, iterations, 256);
    SecretKeyFactory skf = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA512");
    SecretKey pbeKey = skf.generateSecret(ks);

    byte[] decrypted = decrypt(iv, pbeKey.getEncoded(), text, tag);
}
    public static byte[] decrypt(byte[] ivBytes, byte[] keyBytes, byte[] textBytes, byte[] tagBytes)
        throws java.io.UnsupportedEncodingException,
        NoSuchAlgorithmException,
        NoSuchPaddingException,
        InvalidKeyException,
        InvalidAlgorithmParameterException,
        IllegalBlockSizeException,
        BadPaddingException,
        NoSuchProviderException {

        GCMParameterSpec ivSpec = new GCMParameterSpec(tagBytes.length*Byte.SIZE, ivBytes);

        SecretKeySpec newKey = new SecretKeySpec(keyBytes, "AES");

        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
        cipher.init(Cipher.DECRYPT_MODE, newKey, ivSpec);
        return cipher.doFinal(textBytes); //getting tag mismatch error here
    }

正如我在上面的代码中所评论的，我在最后一行得到了一个标签不匹配错误.如果能帮助我找出我做错了什么，我将不胜感激.

As I have commented in the above code, I get a Tag mismatch error in the last line. I would appreciate some help in finding out what I am doing wrong.

我在这行代码中有错误:

I have error in this line code:

cipher.init(Cipher.DECRYPT_MODE, newKey, ivSpec)
java.security.InvalidKeyException: Illegal key size
at javax.crypto.Cipher.checkCryptoPerm(Cipher.java:1039)
at javax.crypto.Cipher.implInit(Cipher.java:805)
at javax.crypto.Cipher.chooseProvider(Cipher.java:864)
at javax.crypto.Cipher.init(Cipher.java:1396)
at javax.crypto.Cipher.init(Cipher.java:1327)
at com.micropro.namwebservice.utils.CryptoUtils.decrypt(CryptoUtils.java:93)
at com.micropro.namwebservice.utils.CryptoUtils.decrypt(CryptoUtils.java:82)

推荐答案

您需要将标签提供给 Java GCM 代码，以便它可以检查消息是否真实.Java API 期望将标签附加到密文中.更改代码以执行此操作的最简单方法是替换该行

You need to provide the tag to the Java GCM code so that it can check that the message is authentic. The Java API expects the tag to be appended to the ciphertext. The simplest way to change your code to do that would be to replace the line

return cipher.doFinal(textBytes);

两行:

cipher.update(textBytes);
return cipher.doFinal(tagBytes);

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