javax.crypto.BadPaddingException: Given final block not properly padded. Such issues can arise if a

文章目录

• 一、发现问题
• 二、分析问题
• 三、解决问题

• 3.1 方法一：不要用openjdk
• 3.2 方法二：修改KeyGenerator.init

• 四、全部源码

一、发现问题

javax.crypto.BadPaddingException: Given final block not properly padded. Such issues can arise if a bad key is used during decryption.
	at java.base/com.sun.crypto.provider.CipherCore.unpad(CipherCore.java:977)
	at java.base/com.sun.crypto.provider.CipherCore.fillOutputBuffer(CipherCore.java:1058)
	at java.base/com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:855)
	at java.base/com.sun.crypto.provider.DESCipher.engineDoFinal(DESCipher.java:314)
	at java.base/javax.crypto.Cipher.doFinal(Cipher.java:2207)

二、分析问题

这是一个des解密的代码，在执行cipher.doFinal()的时候报错：BadPaddingException

public static String decrypt(String keyStr,String content){
    try {
        Key key = loadKey(keyStr);
        Cipher cipher = Cipher.getInstance("DES");
        cipher.init(Cipher.DECRYPT_MODE,key);
        byte[] source =Base64.getDecoder().decode(content.getBytes(StandardCharsets.UTF_8));
        return new String(cipher.doFinal(source),StandardCharsets.UTF_8);
    }catch (Exception e){
        e.printStackTrace();
        return null;
    }
}

三、解决问题

• 这边有两个方法，两个方法都能解决问题，二选一即可。

3.1 方法一：不要用openjdk

3.2 方法二：修改KeyGenerator.init

generator.init(new SecureRandom(keyStr.getBytes(StandardCharsets.UTF_8)));

修改成

SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
secureRandom.setSeed(keyStr.getBytes());
generator.init(secureRandom);

四、全部源码

private static Key loadKey(String keyStr){
        Key key = null;
        try {
            KeyGenerator generator = KeyGenerator.getInstance("DES");
//            generator.init(new SecureRandom(keyStr.getBytes(StandardCharsets.UTF_8)));

            SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
            secureRandom.setSeed(keyStr.getBytes());
            generator.init(secureRandom);

            key = generator.generateKey();
        }catch (Exception e){
            e.printStackTrace();
        }
        return key;
    }

    public static String encrypt(String keyStr,String content){
        try {
            Key key = loadKey(keyStr);
            Cipher cipher = Cipher.getInstance("DES");
            cipher.init(Cipher.ENCRYPT_MODE,key);
            byte[] source = cipher.doFinal(content.getBytes(StandardCharsets.UTF_8));
            return new String(Base64.getEncoder().encode(source),StandardCharsets.UTF_8);
        }catch (Exception e){
            e.printStackTrace();
            return null;
        }
    }

    public static String decrypt(String keyStr,String content){
        try {
            Key key = loadKey(keyStr);
            Cipher cipher = Cipher.getInstance("DES");
            cipher.init(Cipher.DECRYPT_MODE,key);
            byte[] source =Base64.getDecoder().decode(content.getBytes(StandardCharsets.UTF_8));
            return new String(cipher.doFinal(source),StandardCharsets.UTF_8);
        }catch (Exception e){
            e.printStackTrace();
            return null;
        }
    }