小程序对encryptedData进行解密之javax.crypto.BadPaddingException: pad block corrupted

  代码参考链接：http://blog.youkuaiyun.com/l1028386804/article/details/79450115
  出现报错：javax.crypto.BadPaddingException: pad block corrupted。为了解决这个，心态都崩溃了。
  官方给的步骤如下 ：

1. 对称解密使用的算法为 AES-128-CBC，数据采用PKCS#7填充。
2. 对称解密的目标密文为 Base64_Decode(encryptedData)。
3. 对称解密秘钥 aeskey = Base64_Decode(session_key), aeskey 是16字节。
4. 对称解密算法初始向量 为Base64_Decode(iv)，其中iv由数据接口返回。
   主要代码如下：
   AESUtil.java

package com.ebuy.football.util;

import java.security.AlgorithmParameters;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.Security;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

/**
 * AES加密
 *
 */
public class AESUtil {

    public static boolean initialized = false;

    /**
     * AES解密
     * 
     * @param content
     *            密文
     * @return
     * @throws InvalidAlgorithmParameterException
     * @throws NoSuchProviderException
     */
    public byte[] decrypt(byte[] content, byte[] keyByte, byte[] ivByte) throws InvalidAlgorithmParameterException {
        initialize();
        try {
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding","BC");
            Key sKeySpec = new SecretKeySpec(keyByte, "AES");
            cipher.init(Cipher.DECRYPT_MODE, sKeySpec, generateIV(ivByte));// 初始化
            byte[] result = cipher.doFinal(content);
            return result;
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            e.printStackTrace();
        } catch (InvalidKeyException e) {
            e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
            e.printStackTrace();
        } catch (BadPaddingException e) {
            e.printStackTrace();
        } catch (NoSuchProviderException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }

    public static void initialize() {
        if (initialized)
            return;
        Security.addProvider(new BouncyCastleProvider());
        initialized = true;
    }

    // 生成iv
    public static AlgorithmParameters generateIV(byte[] iv) throws Exception {
        AlgorithmParameters params = AlgorithmParameters.getInstance("AES");
        params.init(new IvParameterSpec(iv));
        return params;
    }
}

WxPKCS7EncoderUtil.java

package com.ebuy.football.util;

import java.nio.charset.Charset;
import java.util.Arrays;


/**
 * 微信小程序加解密
 *
 */
public class WxPKCS7EncoderUtil {
    private static final Charset CHARSET = Charset.forName("utf-8");
    private static final int BLOCK_SIZE = 32;

    /**
     * 获得对明文进行补位填充的字节.
     *
     * @param count
     *            需要进行填充补位操作的明文字节个数
     * @return 补齐用的字节数组
     */
    public static byte[] encode(int count) {
        // 计算需要填充的位数
        int amountToPad = BLOCK_SIZE - (count % BLOCK_SIZE);
        if (amountToPad == 0) {
            amountToPad = BLOCK_SIZE;
        }
        // 获得补位所用的字符
        char padChr = chr(amountToPad);
        String tmp = new String();
        for (int index = 0; index < amountToPad; index++) {
            tmp += padChr;
        }
        return tmp.getBytes(CHARSET);
    }

    /**
     * 删除解密后明文的补位字符
     *
     * @param decrypted
     *            解密后的明文
     * @return 删除补位字符后的明文
     */
    public static byte[] decode(byte[] decrypted) {
        int pad = decrypted[decrypted.length - 1];
        if (pad < 1 || pad > 32) {
            pad = 0;
        }
        return Arrays.copyOfRange(decrypted, 0, decrypted.length - pad);
    }

    /**
     * 将数字转化成ASCII码对应的字符，用于对明文进行补码
     *
     * @param a
     *            需要转化的数字
     * @return 转化得到的字符
     */
    public static char chr(int a) {
        byte target = (byte) (a & 0xFF);
        return (char) target;
    }
}

WXCoreUtil.java

package com.ebuy.football.util;


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

public class WXCoreUtil {
    private static final String WATERMARK = "watermark";
    private static final String APPID = "appid";
    /**
     * @return
     * @throws Exception
     */
    public static String decrypt(String appId, String encryptedData, String sessionKey, String iv){
        String result = "";
        try {
            AESUtil aes = new AESUtil();  
            byte[] resultByte = aes.decrypt(Base64.decodeBase64(encryptedData), Base64.decodeBase64(sessionKey), Base64.decodeBase64(iv));  
            if(null != resultByte && resultByte.length > 0){  
                result = new String(WxPKCS7EncoderUtil.decode(resultByte));  
//              JSONObject jsonObject = JSONObject.fromObject(result);
                JSONObject jsonObject = new JSONObject(result);
                String decryptAppid = jsonObject.getJSONObject(WATERMARK).getString(APPID);
                if(!appId.equals(decryptAppid)){
                    result = "";
                }
            }  
        } catch (Exception e) {
            result = "";
            e.printStackTrace();
        }
        return result;
    }

}

执行代码：WXCoreUtil.decrypt(appid, encryptedData, sessionKey, iv);

以上问题我遇到了一个大坑：Cipher cipher = Cipher.getInstance(“AES/CBC/PKCS7Padding”,”BC”);
后面要加”BC”,就是这个原因了。太坑了。希望能解决你的问题。哪位老哥知道原因为什么要加BC，能解释下吗，lz不知道，欢迎评论！