Preferences＆javax.crypto.BadPaddingException：給定最終塊，未正確填充

Question

我已經盯着這個代碼好幾個小時了，我一定很傻。 結果，在這里有人的幫助深表感謝。

下面是示例代碼，最簡單的我可以得到它來再現此問題。 該代碼在第一次運行時運行良好，但是在為IV創建首選項之后，此后失敗。

與該代碼相比，我的真實代碼在首選項中存儲的更多，我在麻煩的拍攝過程中對其進行了很多簡化，以使其更易於隔離。

我的目標是創建一個類，該類允許我存儲使用從用戶提供的密碼派生的密鑰的，用AES 128加密加密的首選項。 例如安全首選項。 我在故障排除中取出了用戶提供的所有pwd內容。

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 "";
   }
}

僅在2次以上的運行中收到的Stacktrace：

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)

------------編輯正確答案------------正如GregS指出的那樣，當存在首選項時，我沒有將IV加載到加密例程中。結果是不匹配。 下面是解決問題的更新的加密功能。

    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指出的那樣，當存在首選項時，我沒有將IV加載到加密例程中，因此存在不匹配的情況。 下面是解決問題的更新的加密功能。

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 "";
   }