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Wudaosoft Commons Library
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/**
 * 对公众平台发送给公众账号的消息加解密示例代码.
 * 
 * @copyright Copyright (c) 1998-2014 Tencent Inc.
 */

// ------------------------------------------------------------------------

/**
 * 针对org.apache.commons.codec.binary.Base64，
 * 需要导入架包commons-codec-1.9（或commons-codec-1.8等其他版本）
 * 官方下载地址：http://commons.apache.org/proper/commons-codec/download_codec.cgi
 */
package com.wudaosoft.commons.aes;

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

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import com.wudaosoft.commons.utils.Base58;


/**
 * 提供接收和推送给公众平台消息的加解密接口(UTF8编码的字符串).
 * 
 * 	第三方回复加密消息给公众平台
 * 	第三方收到公众平台发送的消息，验证消息的安全性，并对消息进行解密。
 * 
 * 说明：异常java.security.InvalidKeyException:illegal Key Size的解决方案
 * 
 * 	在官方网站下载JCE无限制权限策略文件（JDK7的下载地址：
 *      http://www.oracle.com/technetwork/java/javase/downloads/jce-7-download-432124.html
 * 	下载后解压，可以看到local_policy.jar和US_export_policy.jar以及readme.txt
 * 	如果安装了JRE，将两个jar文件放到%JRE_HOME%\lib\security目录下覆盖原来的文件
 * 	如果安装了JDK，将两个jar文件放到%JDK_HOME%\jre\lib\security目录下覆盖原来文件
 * 
 */
public class MessageCrypt {
	
	private static final String RANDOM_BASE_STR = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
	private static final Charset CHARSET = Charset.forName("utf-8");

	private MessageCrypt(){
	}

	// 生成4个字节的网络字节序
	static byte[] getNetworkBytesOrder(int sourceNumber) {
		byte[] orderBytes = new byte[4];
		orderBytes[3] = (byte) (sourceNumber & 0xFF);
		orderBytes[2] = (byte) (sourceNumber >> 8 & 0xFF);
		orderBytes[1] = (byte) (sourceNumber >> 16 & 0xFF);
		orderBytes[0] = (byte) (sourceNumber >> 24 & 0xFF);
		return orderBytes;
	}

	// 还原4个字节的网络字节序
	static int recoverNetworkBytesOrder(byte[] orderBytes) {
		int sourceNumber = 0;
		for (int i = 0; i < 4; i++) {
			sourceNumber <<= 8;
			sourceNumber |= orderBytes[i] & 0xff;
		}
		return sourceNumber;
	}

	// 随机生成16位字符串
	static String getRandomStr() {
		Random random = new Random();
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < 16; i++) {
			int number = random.nextInt(RANDOM_BASE_STR.length());
			sb.append(RANDOM_BASE_STR.charAt(number));
		}
		return sb.toString();
	}

	/**
	 * 对明文进行加密.
	 * 
	 * @param text 需要加密的明文
	 * @return 加密后base64编码的字符串
	 * @throws AesException aes加密失败
	 */
	public static String encrypt(String text, byte[] aesKey) throws AesException {
		ByteGroup byteCollector = new ByteGroup();
		byte[] randomStrBytes = getRandomStr().getBytes(CHARSET);
		byte[] textBytes = text.getBytes(CHARSET);
		byte[] networkBytesOrder = getNetworkBytesOrder(textBytes.length);
//		byte[] appidBytes = CommonApi.APP_ID.getBytes(CHARSET);

		// randomStr + networkBytesOrder + text + appid
		byteCollector.addBytes(randomStrBytes);
		byteCollector.addBytes(networkBytesOrder);
		byteCollector.addBytes(textBytes);
//		byteCollector.addBytes(appidBytes);

		// ... + pad: 使用自定义的填充方式对明文进行补位填充
		byte[] padBytes = PKCS7Encoder.encode(byteCollector.size());
		byteCollector.addBytes(padBytes);

		// 获得最终的字节流, 未加密
		byte[] unencrypted = byteCollector.toBytes();

		try {
			// 设置加密模式为AES的CBC模式
			Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
			SecretKeySpec keySpec = new SecretKeySpec(aesKey, "AES");
			IvParameterSpec iv = new IvParameterSpec(aesKey, 0, 16);
			cipher.init(Cipher.ENCRYPT_MODE, keySpec, iv);

			// 加密
			byte[] encrypted = cipher.doFinal(unencrypted);

			// 使用BASE58对加密后的字符串进行编码
			String base58Encrypted = Base58.encode(encrypted);

			return base58Encrypted;
		} catch (Exception e) {
			e.printStackTrace();
			throw new AesException(AesException.EncryptAESError);
		}
	}

	/**
	 * 对密文进行解密.
	 * 
	 * @param text 需要解密的密文
	 * @return 解密得到的明文
	 * @throws AesException aes解密失败
	 */
	public static String decrypt(String text, byte[] aesKey) throws AesException {
		byte[] original;
		try {
			// 设置解密模式为AES的CBC模式
			Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
			SecretKeySpec key_spec = new SecretKeySpec(aesKey, "AES");
			IvParameterSpec iv = new IvParameterSpec(Arrays.copyOfRange(aesKey, 0, 16));
			cipher.init(Cipher.DECRYPT_MODE, key_spec, iv);

			// 使用BASE64对密文进行解码
			byte[] encrypted = Base58.decode(text);

			// 解密
			original = cipher.doFinal(encrypted);
		} catch (Exception e) {
			e.printStackTrace();
			throw new AesException(AesException.DecryptAESError);
		}

		String xmlContent;// from_appid;
		try {
			// 去除补位字符
			byte[] bytes = PKCS7Encoder.decode(original);

			// 分离16位随机字符串,网络字节序和AppId
			//byte[] networkOrder = Arrays.copyOfRange(bytes, 16, 20);

			//int xmlLength = recoverNetworkBytesOrder(networkOrder);

			xmlContent = new String(Arrays.copyOfRange(bytes, 20, bytes.length), CHARSET);
			//from_appid = new String(Arrays.copyOfRange(bytes, 20 + xmlLength, bytes.length), CHARSET);
		} catch (Exception e) {
			e.printStackTrace();
			throw new AesException(AesException.IllegalBuffer);
		}

		return xmlContent;
	}
}