在Java中使用AES单独解密时BadPaddingException

Question

我正在使用AES进行加密/解密。我正在尝试加密文本，然后再单独解密。

我的AESEncrypt.java是：

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.spec.KeySpec;
import org.apache.commons.codec.binary.Base64;

public class AESEncrypt {
    private static final byte[] SALT = {(byte) 0xA9, (byte) 0x9B, (byte) 0xC8, (byte) 0x32, (byte) 0x56, (byte) 0x35, (byte) 0xE3, (byte) 0x03};
    private static final int ITERATION_COUNT = 65536;
    private static final int KEY_LENGTH = 256;
    private Cipher eCipher;
    private Cipher dCipher;

    AESEncrypt(String passPhrase) throws Exception {
        SecretKeyFactory secretKeyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), SALT, ITERATION_COUNT, KEY_LENGTH);
        SecretKey secretKeyTemp = secretKeyFactory.generateSecret(keySpec);
        SecretKey secretKey = new SecretKeySpec(secretKeyTemp.getEncoded(), "AES");

        eCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        eCipher.init(Cipher.ENCRYPT_MODE, secretKey);

        dCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        byte[] iv = eCipher.getParameters().getParameterSpec(IvParameterSpec.class).getIV();
        dCipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(iv));
    }

    public String encrypt(String encrypt) throws Exception {
        byte[] bytes = encrypt.getBytes("UTF8");
        byte[] encrypted = encrypt(bytes);
        return new String(Base64.encodeBase64(encrypted));
    }

    public byte[] encrypt(byte[] plain) throws Exception {
        return eCipher.doFinal(plain);
    }

    public static void main(String[] args) throws Exception {
        String passphrase = "PASSWORDPASSPHRASE";
        String password = "password123";    
        AESEncrypt aesEncrypt = new AESEncrypt(passphrase); 
        String encryptedPassword = aesEncrypt.encrypt(password);
        System.out.println("encryptedPassword = " + encryptedPassword);
    }
}

运行上面的AESEncrypt代码后，结果为：

encryptedPassword = aUkbhjFebZ9VjJ44yptlBA==

所以，现在在我的AESDecrypt.java中，我正在使用该encryptedPassword字符串进行解密：

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.spec.KeySpec;
import org.apache.commons.codec.binary.Base64;

public class AESDecrypt {
    private static final byte[] SALT = {(byte) 0xA9, (byte) 0x9B, (byte) 0xC8, (byte) 0x32, (byte) 0x56, (byte) 0x35, (byte) 0xE3, (byte) 0x03};
    private static final int ITERATION_COUNT = 65536;
    private static final int KEY_LENGTH = 256;
    private Cipher eCipher;
    private Cipher dCipher;

    AESDecrypt(String passPhrase) throws Exception {
        SecretKeyFactory secretKeyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), SALT, ITERATION_COUNT, KEY_LENGTH);
        SecretKey secretKeyTemp = secretKeyFactory.generateSecret(keySpec);
        SecretKey secretKey = new SecretKeySpec(secretKeyTemp.getEncoded(), "AES");

        eCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        eCipher.init(Cipher.ENCRYPT_MODE, secretKey);

        dCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        byte[] iv = eCipher.getParameters().getParameterSpec(IvParameterSpec.class).getIV();
        dCipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(iv));
    }

    public String decrypt(String encrypt) throws Exception {
        byte[] bytes = Base64.decodeBase64(encrypt);
        byte[] decrypted = decrypt(bytes);
        return new String(decrypted, "UTF8");
    }

    public byte[] decrypt(byte[] encrypt) throws Exception {
        return dCipher.doFinal(encrypt);
    }

    public static void main(String[] args) throws Exception {
        String passphrase = "PASSWORDPASSPHRASE";
        String encryptedPassword = "aUkbhjFebZ9VjJ44yptlBA==";        
        AESDecrypt aesDecrypt = new AESDecrypt(passphrase);
        String decryptedPassword = aesDecrypt.decrypt(encryptedPassword);
        System.out.println("decryptedPasswpord = " + decryptedPassword);
    }
}

运行AESDecrypt代码时，会返回错误：

Exception in thread "main" javax.crypto.BadPaddingException: Given final block not properly padded
    at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
    at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
    at com.sun.crypto.provider.AESCipher.engineDoFinal(DashoA13*..)
    at javax.crypto.Cipher.doFinal(DashoA13*..)
    at AESDecrypt.decrypt(AESDecrypt.java:41)
    at AESDecrypt.decrypt(AESDecrypt.java:35)
    at AESDecrypt.main(AESDecrypt.java:50)

为什么会出错？有人可以提供帮助和建议吗？非常感谢你！

Answer 1

使用CBC（密码块链接）模式时，您必须提取InitializationVector并附加到加密消息，或者找到另一种方法将相同的IV传递给解密代码。

CBC模式是一种比ECB更安全的模式，它不使用IV。 CBC使用随机IV，确保加密两次的相同数据不会产生相同的密文。

所以你的代码应该是这样的：

import java.security.spec.KeySpec;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.binary.Base64;


public class AESEncrypt {
    private static final byte[] SALT = {(byte) 0xA9, (byte) 0x9B, (byte) 0xC8, (byte) 0x32, (byte) 0x56, (byte) 0x35, (byte) 0xE3, (byte) 0x03};
    private static final int ITERATION_COUNT = 65536;
    private static final int KEY_LENGTH = 128;
    private Cipher eCipher;
    private Cipher dCipher;
    private byte[] iv;

    AESEncrypt(String passPhrase) throws Exception {
        SecretKeyFactory secretKeyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), SALT, ITERATION_COUNT, KEY_LENGTH);
        SecretKey secretKeyTemp = secretKeyFactory.generateSecret(keySpec);
        SecretKey secretKey = new SecretKeySpec(secretKeyTemp.getEncoded(), "AES");

        eCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        eCipher.init(Cipher.ENCRYPT_MODE, secretKey);

        dCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        iv = eCipher.getParameters().getParameterSpec(IvParameterSpec.class).getIV();
        dCipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(iv));
    }

    public String encrypt(String encrypt) throws Exception {
        byte[] bytes = encrypt.getBytes("UTF8");
        byte[] encrypted = encrypt(bytes);
        byte[] cipherText = new byte[encrypted.length + iv.length];
        System.arraycopy(iv, 0, cipherText, 0, iv.length);
        System.arraycopy(encrypted, 0, cipherText, iv.length, encrypted.length);
        return new String(Base64.encodeBase64(cipherText));
    }

    public byte[] encrypt(byte[] plain) throws Exception {
        return eCipher.doFinal(plain);
    }

    public static void main(String[] args) throws Exception {
        String passphrase = "PASSWORDPASSPHRASE";
        String password = "password123";    
        AESEncrypt aesEncrypt = new AESEncrypt(passphrase); 
        String encryptedPassword = aesEncrypt.encrypt(password);
        System.out.println("encryptedPassword = " + encryptedPassword);
    }
}

并且：

 import java.security.spec.KeySpec;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.binary.Base64;


public class AESDecrypt {
    private static final byte[] SALT = {(byte) 0xA9, (byte) 0x9B, (byte) 0xC8, (byte) 0x32, (byte) 0x56, (byte) 0x35, (byte) 0xE3, (byte) 0x03};
    private static final int ITERATION_COUNT = 65536;
    private static final int KEY_LENGTH = 128;
    private static final int IV_LENGTH = 16;
    private Cipher eCipher;
    private Cipher dCipher;
    private byte[] encrypt;

    AESDecrypt(String passPhrase, String encryptedString) throws Exception {
        SecretKeyFactory secretKeyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        KeySpec keySpec = new PBEKeySpec(passPhrase.toCharArray(), SALT, ITERATION_COUNT, KEY_LENGTH);
        SecretKey secretKeyTemp = secretKeyFactory.generateSecret(keySpec);
        SecretKey secretKey = new SecretKeySpec(secretKeyTemp.getEncoded(), "AES");

        encrypt = Base64.decodeBase64(encryptedString);

        eCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        eCipher.init(Cipher.ENCRYPT_MODE, secretKey);

        byte[] iv = extractIV();
        dCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        dCipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(iv));
    }


    private byte[] extractIV() {
        byte[] iv = new byte[IV_LENGTH];
        System.arraycopy(encrypt, 0, iv, 0, iv.length);
        return iv;
    }

    public String decrypt() throws Exception {
        byte[] bytes = extractCipherText();

        byte[] decrypted = decrypt(bytes);
        return new String(decrypted, "UTF8");
    }

    private byte[] extractCipherText() {
        byte[] ciphertext = new byte[encrypt.length - IV_LENGTH];
        System.arraycopy(encrypt, 16, ciphertext, 0, ciphertext.length);
        return ciphertext;
    }

    public byte[] decrypt(byte[] encrypt) throws Exception {
        return dCipher.doFinal(encrypt);
    }

    public static void main(String[] args) throws Exception {
        String passphrase = "PASSWORDPASSPHRASE";
        String encryptedPassword = "LiN1KmaB2Pl7cooe3qvuImbAKXsVJt5oxt+ajuVZ5n4=";        
        AESDecrypt aesDecrypt = new AESDecrypt(passphrase, encryptedPassword);
        String decryptedPassword = aesDecrypt.decrypt();
        System.out.println("decryptedPasswpord = " + decryptedPassword);
    }
}