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

系统管理员 2023-10-07 20:47 8阅读 0赞

#### 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 ##

![在这里插入图片描述][67682bd432334649817b7d2161729d50.png]

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 ###

![在这里插入图片描述][55d7f1165cfa4ad4a03767af7d89f67d.png]

### 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;
            }
        }

***觉得好，就一键三连呗（点赞+收藏+关注）***

[67682bd432334649817b7d2161729d50.png]: https://img-blog.csdnimg.cn/67682bd432334649817b7d2161729d50.png
[55d7f1165cfa4ad4a03767af7d89f67d.png]: https://img-blog.csdnimg.cn/55d7f1165cfa4ad4a03767af7d89f67d.png