首选项 & javax.crypto.BadPaddingException：给定的最终块未正确填充

Question

我已经盯着这段代码看了好几个小时了，我一定漏掉了一些愚蠢的东西。因此，非常感谢有人在这里提供帮助。

下面是示例代码，我能得到的最简单的代码来重现这个问题。该代码在第一次运行时运行良好，但在为 IV 创建首选项之后，它就失败了。

我的真实代码在首选项中存储的比这个多得多，我在故障排除中对其进行了很多简化，使其更容易隔离。

我的目标是创建一个 class，它允许我存储使用 AES 128 加密的首选项以及从用户提供的密码派生的密钥。例如安全偏好。我在故障排除中删除了所有用户提供的密码内容。

package com.test;

import java.io.UnsupportedEncodingException;
import java.security.AlgorithmParameters;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidParameterSpecException;
import java.util.Random;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.prefs.Preferences;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import org.apache.commons.codec.binary.Base64;

public class Settings {
    private Preferences prefs = null;
    private byte[] iv = null;
    private SecretKey secret = null;
    Cipher cipher = null;

    public static void main(String[] args){
       Settings t = new Settings();
       String encText = t.encryptText("HELLO");//Encrypt a value
       String output = t.decryptText(encText);//Decrypt the value
       System.out.println(output); //Display the decrypted value.
    }

    public Settings(){
        try {
            String parentClass = new Exception().getStackTrace()[1].getClassName();//Really only controls where the prefs go, shouldn't matter.
            this.prefs = Preferences.userNodeForPackage(Class.forName(parentClass));
            Random r = new SecureRandom();
            KeyGenerator keyGen = KeyGenerator.getInstance("AES");
            keyGen.init(128); // 128 bit key
            this.secret = keyGen.generateKey();

            cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        } catch (NoSuchAlgorithmException ex) {
            Logger.getLogger(this.getClass().getName()).log(Level.SEVERE, null, ex);
        } catch (Exception ex) {
            Logger.getLogger(this.getClass().getName()).log(Level.SEVERE, null, ex);
        }
    }
        private String encryptText(String plainText){
        try {
            cipher.init(Cipher.ENCRYPT_MODE, this.secret);
            AlgorithmParameters params = cipher.getParameters();

            this.iv = prefs.getByteArray("IV", null);
            if(this.iv == null){
                this.iv = params.getParameterSpec(IvParameterSpec.class).getIV();
                prefs.putByteArray("IV", this.iv);
            }
            byte[] ciphertext = cipher.doFinal(plainText.getBytes("UTF-8"));
            String ret = new String(Base64.encodeBase64(ciphertext));
            return ret;
        } catch (InvalidParameterSpecException | IllegalBlockSizeException | BadPaddingException | UnsupportedEncodingException | InvalidKeyException ex) {
            Logger.getLogger(this.getClass().getName()).log(Level.SEVERE, null, ex);
        }
        return "";
   }
    private String decryptText(String cipherText){
        try {
            this.iv = prefs.getByteArray("IV", null);
            byte[] cText = Base64.decodeBase64(cipherText); 
            cipher.init(Cipher.DECRYPT_MODE, this.secret, new IvParameterSpec(this.iv));
            String ret = new String(cipher.doFinal(cText), "UTF-8");
            return ret;
        } catch (IllegalBlockSizeException | BadPaddingException | UnsupportedEncodingException | InvalidKeyException | InvalidAlgorithmParameterException ex) {
            Logger.getLogger(this.getClass().getName()).log(Level.SEVERE, null, ex);
        }
        return "";
   }
}

仅在 2 次以上运行时收到的堆栈跟踪：

Feb 07, 2015 9:02:46 PM com.test.Settings decryptText

SEVERE: null
javax.crypto.BadPaddingException: Given final block not properly padded
    at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:811)
    at com.sun.crypto.provider.CipherCore.doFinal(CipherCore.java:676)
    at com.sun.crypto.provider.AESCipher.engineDoFinal(AESCipher.java:313)
    at javax.crypto.Cipher.doFinal(Cipher.java:2087)
    at com.test.Settings.decryptText(Settings.java:77)
    at com.test.Settings.main(Settings.java:34)

------------ 编辑正确答案------------ 正如 GregS 指出的那样，当存在首选项时，我没有将 IV 加载到加密例程中，因此存在不匹配。以下是问题修复后更新的加密函数。

    private String encryptText(String plainText){
        try {
            this.iv = prefs.getByteArray("IV", null);
            if(this.iv == null) { //If not set, set the IV
                cipher.init(Cipher.ENCRYPT_MODE, this.secret);
                AlgorithmParameters params = cipher.getParameters();
                this.iv = params.getParameterSpec(IvParameterSpec.class).getIV();
                prefs.putByteArray("IV", this.iv);
            } else {
                cipher.init(Cipher.ENCRYPT_MODE, this.secret, new IvParameterSpec(this.iv));
            }

            byte[] ciphertext = cipher.doFinal(plainText.getBytes("UTF-8"));
            String ret = new String(Base64.encodeBase64(ciphertext));
            return ret;
        } catch (InvalidParameterSpecException | IllegalBlockSizeException | BadPaddingException | UnsupportedEncodingException | InvalidKeyException ex) {
            Logger.getLogger(this.getClass().getName()).log(Level.SEVERE, null, ex);
        } catch (InvalidAlgorithmParameterException ex) {
            Logger.getLogger(Settings.class.getName()).log(Level.SEVERE, null, ex);
        }
        return "";
   }

Answer 1

正如 GregS 指出的那样，当存在首选项时，我没有将 IV 加载到加密例程中，结果出现了不匹配。以下是问题修复后更新的加密函数。

private String encryptText(String plainText){
    try {
        this.iv = prefs.getByteArray("IV", null);
        if(this.iv == null) { //If not set, set the IV
            cipher.init(Cipher.ENCRYPT_MODE, this.secret);
            AlgorithmParameters params = cipher.getParameters();
            this.iv = params.getParameterSpec(IvParameterSpec.class).getIV();
            prefs.putByteArray("IV", this.iv);
        } else {
            cipher.init(Cipher.ENCRYPT_MODE, this.secret, new IvParameterSpec(this.iv));
        }

        byte[] ciphertext = cipher.doFinal(plainText.getBytes("UTF-8"));
        String ret = new String(Base64.encodeBase64(ciphertext));
        return ret;
    } catch (InvalidParameterSpecException | IllegalBlockSizeException | BadPaddingException | UnsupportedEncodingException | InvalidKeyException ex) {
        Logger.getLogger(this.getClass().getName()).log(Level.SEVERE, null, ex);
    } catch (InvalidAlgorithmParameterException ex) {
        Logger.getLogger(Settings.class.getName()).log(Level.SEVERE, null, ex);
    }
    return "";
   }

首选项 & javax.crypto.BadPaddingException：给定的最终块未正确填充

Preferences & javax.crypto.BadPaddingException: Given final block not properly padded

java

encryption

aes

preferences