一、关键词
HTTP，HTTPS，AES，SHA-1，MD5，消息摘要，数字签名，数字加密，Java，Servlet，Bouncy Castle
二、名词解释
数字摘要：是将任意长度的消息变成固定长度的短消息，它类似于一个自变量是消息的函数，也就是Hash函数。数字摘要就是采用单项Hash函数将需要加密的明文“摘要”成一串固定长度（128位）的密文这一串密文又称为数字指纹，它有固定的长度，而且不同的明文摘要成密文，其结果总是不同的，而同样的明文其摘要必定一致。
AES：密码学中的高级加密标准（Advanced Encryption Standard，AES），又称Rijndael加密法，是美国联邦政府采用的一种区块加密标准。这个标准用来替代原先的DES，已经被多方分析且广为全世界所使用。是一种对称加密算法。
SHA-1：安全哈希算法（Secure Hash Algorithm）主要适用于数字签名标准 （Digital Signature Standard DSS）里面定义的数字签名算法（Digital Signature Algorithm DSA）。 SHA1有如下特性：不可以从消息摘要中复原信息；两个不同的消息不会产生同样的消息摘要。
MD5：Message Digest Algorithm MD5（中文名为消息摘要算法第五版）为计算机安全领域广泛使用的一种散列函数，用以提供消息的完整性保护。
三、项目背景
某合作公司需要通过互联网向我司传递一些用户数据，但是我所在项目组的外网服务器上并无部署https，只能基于http进行数据传输。为了保护双方共同的用户数据，必须对在互联网上传输的信息进行加密处理。
四、方案设计
这里涉及到两个问题，一是采用什么样的远程消息传递框架，二是如何对传输的数据进行加密。
本人平时开发所用的语言主要是Java，对于Jsp/Servlet还比较熟悉，结合去年参加过所在公司的微信公众号开发的经验，设计出了如下方案：
1.在客户端采用构造http post请求，把用户数据加密后放入request body中，并在http参数中放入调用方的签名；
2.服务端接收到请求，提取参数进行签名校验，通过后从request body中提取密文进行解密，然后进行后续处理，最终生成响应返回给客户端。
以下是具体处理的流程图：
在数据加密阶段，基于性能以及效率考虑，采用了Bouncy Castle提供的AES算法，而生成签名则采用了jdk提供的SHA-1，值得注意的是，基于安全考虑，消息密文的消息摘要也被列入到参与数字签名的参数之一。
五、代码实现
1.AES加密工具类：
import org.apache.commons.lang.StringUtils;
import org.apache.log4j.Logger;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.engines.AESFastEngine;
import org.bouncycastle.crypto.modes.CBCBlockCipher;
import org.bouncycastle.crypto.paddings.PaddedBufferedBlockCipher;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;
import org.bouncycastle.util.encoders.Hex;
/**
* AES encryption and decryption tool.
*
* @author ben
* @creation 2014年3月20日
*/
public class AESTool {
protected static final Logger log = Logger.getLogger(AESTool.class);
private byte[] initVector = { 0x32, 0x37, 0x36, 0x35, 0x34, 0x33, 0x32, 0x31,
0x38, 0x27, 0x36, 0x35, 0x33, 0x23, 0x32, 0x31 };
/**
* FIXME For demo only, should rewrite this method in your product environment!
*
* @param appid
* @return
*/
public String findKeyById(String appid) {
// Fake key.
String key = "123456789012345678901234567890~!";
return key;
}
/**
* Encrypt the content with a given key using aes algorithm.
*
* @param content
* @param key
* must contain exactly 32 characters
* @return
* @throws Exception
*/
public String encrypt(String content, String key) throws Exception {
if (key == null) {
throw new IllegalArgumentException("Key cannot be null!");
}
String encrypted = null;
byte[] keyBytes = key.getBytes();
if (keyBytes.length != 32 && keyBytes.length != 24
&& keyBytes.length != 16) {
throw new IllegalArgumentException(
"Key length must be 128/192/256 bits!");
}
byte[] encryptedBytes = null;
encryptedBytes = encrypt(content.getBytes(), keyBytes, initVector);
encrypted = new String(Hex.encode(encryptedBytes));
return encrypted;
}
/**
* Decrypt the content with a given key using aes algorithm.
*
* @param content
* @param key
* must contain exactly 32 characters
* @return
* @throws Exception
*/
public String decrypt(String content, String key) throws Exception {
if (key == null) {
throw new IllegalArgumentException("Key cannot be null!");
}
String decrypted = null;
byte[] encryptedContent = Hex.decode(content);
byte[] keyBytes = key.getBytes();
byte[] decryptedBytes = null;
if (keyBytes.length != 32 && keyBytes.length != 24
&& keyBytes.length != 16) {
throw new IllegalArgumentException(
"Key length must be 128/192/256 bits!");
}
decryptedBytes = decrypt(encryptedContent, keyBytes, initVector);
decrypted = new String(decryptedBytes);
return decrypted;
}
/**
* Encrypt data.
*
* @param plain
* @param key
* @param iv
* @return
* @throws Exception
*/
public byte[] encrypt(byte[] plain, byte[] key, byte[] iv) throws Exception {
PaddedBufferedBlockCipher aes = new PaddedBufferedBlockCipher(
new CBCBlockCipher(new AESFastEngine()));
CipherParameters ivAndKey = new ParametersWithIV(new KeyParameter(key),
iv);
aes.init(true, ivAndKey);
return cipherData(aes, plain);
}
/**
* Decrypt data.
*
* @param cipher
* @param key
* @param iv
* @return
* @throws Exception
*/
public byte[] decrypt(byte[] cipher, byte[] key, byte[] iv)
throws Exception {
PaddedBufferedBlockCipher aes = new PaddedBufferedBlockCipher(
new CBCBlockCipher(new AESFastEngine()));
CipherParameters ivAndKey = new ParametersWithIV(new KeyParameter(key),
iv);
aes.init(false, ivAndKey);
return cipherData(aes, cipher);
}
/**
* Encrypt or decrypt data.
*
* @param cipher
* @param data
* @return
* @throws Exception
*/
private byte[] cipherData(PaddedBufferedBlockCipher cipher, byte[] data)
throws Exception {
int minSize = cipher.getOutputSize(data.length);
byte[] outBuf = new byte[minSize];
int length1 = cipher.processBytes(data, 0, data.length, outBuf, 0);
int length2 = cipher.doFinal(outBuf, length1);
int actualLength = length1 + length2;
byte[] result = new byte[actualLength];
System.arraycopy(outBuf, 0, result, 0, result.length);
return result;
}
public static void main(String[] args) throws Exception {
AESTool aesTool = new AESTool();
String appid = "canairport001";
String key = aesTool.findKeyById(appid);
String xml = "test test test test test test test test test test test test test test test test test
2.数字签名工具类：
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.apache.commons.lang.StringUtils;
import org.apache.log4j.Logger;
/**
* @author lixuanbin
* @creation 2013-1-30
*/
public class SignatureUtil {
protected static Logger log = Logger.getLogger(SignatureUtil.class);
private static final char[] hexArray = "0123456789ABCDEF".toCharArray();
private String encryptionAlgorithm = "SHA-1";
public String bytesToHexString(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
for (int j = 0; j < bytes.length; j++) {
int v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
public byte[] hexStringToBytes(String s) {
int len = s.length();
byte[] data = new byte[len / 2];
for (int i = 0; i < len; i += 2) {
data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character
.digit(s.charAt(i + 1), 16));
}
return data;
}
/**
* 使用指定算法生成消息摘要，默认是md5
*
* @param strSrc
* , a string will be encrypted;
* @param encName
* , the algorithm name will be used, dafault to "MD5";
* @return
*/
public String digest(String strSrc, String encName) {
MessageDigest md = null;
String strDes = null;
byte[] bt = strSrc.getBytes();
try {
if (encName == null || encName.equals("")) {
encName = "MD5";
}
md = MessageDigest.getInstance(encName);
md.update(bt);
strDes = bytesToHexString(md.digest()); // to HexString
} catch (NoSuchAlgorithmException e) {
log.error("Invalid algorithm: " + encName);
return null;
}
return strDes;
}
/**
* 根据appid、token、lol以及时间戳来生成签名
*
* @param appid
* @param token
* @param lol
* @param millis
* @return
*/
public String generateSignature(String appid, String token, String lol,
long millis) {
String timestamp = String.valueOf(millis);
String signature = null;
if (StringUtils.isNotBlank(token) && StringUtils.isNotBlank(timestamp)
&& StringUtils.isNotBlank(appid)) {
List srcList = new ArrayList();
srcList.add(timestamp);
srcList.add(appid);
srcList.add(token);
srcList.add(lol);
// 按照字典序逆序拼接参数
Collections.sort(srcList);
Collections.reverse(srcList);
StringBuilder sb = new StringBuilder();
for (int i = 0; i < srcList.size(); i++) {
sb.append(srcList.get(i));
}
signature = digest(sb.toString(), encryptionAlgorithm);
srcList.clear();
srcList = null;
}
return signature;
}
/**
* 验证签名:
* 1.根据appid获取该渠道的token;
* 2.根据appid、token、lol以及时间戳计算一次签名;
* 3.比较传过来的签名以及计算出的签名是否一致;
* @param signature
* @param appid
* @param lol
* @param millis
* @return
*/
public boolean isValid(String signature, String appid, String lol,
long millis) {
String token = findTokenById(appid);
String calculatedSignature = generateSignature(appid, token, lol,
millis);
log.info("calculated signature: \n" + calculatedSignature);
if (StringUtils.equals(calculatedSignature, signature)) {
return true;
} else {
return false;
}
}
/**
* FIXME For demo only, should be a different string in production.
* @param appid
* @return
*/
public String findTokenById(String appid) {
String token = "#@!1234567890!@#";
return token;
}
public static void main(String[] args) {
SignatureUtil generator = new SignatureUtil();
String xmlString = "test test test test test test test test test test test test test test test test test test test test test test test test test test test test test 3.发送方代码：
import java.io.IOException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import org.apache.commons.lang.StringUtils;
import org.apache.http.HttpEntity;
import org.apache.http.HttpHost;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.conn.params.ConnRoutePNames;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicHeader;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;
import org.apache.log4j.Logger;
/**
* @author ben
* @creation 2014年6月9日
*/
public class HttpclientUtil {
protected static final Logger log = Logger.getLogger(HttpclientUtil.class);
/**
* 根据传入的uri和参数map拼接成实际uri
*
* @param uri
* @param paraMap
* @return
*/
public String buildUri(String uri, Map paraMap) {
StringBuilder sb = new StringBuilder();
uri = StringUtils.trim(uri);
uri = StringUtils.removeEnd(uri, "/");
uri = StringUtils.removeEnd(uri, "?");
sb.append(uri);
if (paraMap != null && !paraMap.isEmpty()) {
sb.append("?");
Iterator> iterator = paraMap.entrySet()
.iterator();
while (iterator.hasNext()) {
Map.Entry pair = iterator.next();
try {
String keyString = pair.getKey();
String valueString = pair.getValue();
sb.append(keyString);
sb.append("=");
sb.append(valueString);
sb.append("&");
} catch (Exception e) {
log.error(e, e);
}
}
}
return StringUtils.removeEnd(sb.toString(), "&");
}
/**
* Post an xml string to a specific host.
*
* @param targetHost
* @param targetPort
* @param protocol
* @param proxyHost
* @param proxyPort
* @param proxyUser
* @param proxyPassword
* @param uri
* @param paraMap
* @param xml
* @param charset
* @return
* @throws ClientProtocolException
* @throws IOException
*/
public String postXmlString(String targetHost, int targetPort,
String protocol, String proxyHost, int proxyPort, String proxyUser,
String proxyPassword, String uri, Map paraMap,
String xml, String charset) throws ClientProtocolException,
IOException {
String result = null;
DefaultHttpClient httpclient = new DefaultHttpClient();
if (StringUtils.isNotBlank(proxyHost) && proxyPort > 0) {
// 设置上网代理
AuthScope authScope = new AuthScope(proxyHost, proxyPort);
if (StringUtils.isNotBlank(proxyUser)
&& StringUtils.isNotBlank(proxyPassword)) {
// 设置上网代理的用户名和密码
UsernamePasswordCredentials upc = new UsernamePasswordCredentials(
proxyUser, proxyPassword);
httpclient.getCredentialsProvider().setCredentials(authScope,
upc);
}
HttpHost proxy = new HttpHost(proxyHost, proxyPort);
httpclient.getParams().setParameter(ConnRoutePNames.DEFAULT_PROXY,
proxy);
}
HttpHost host = new HttpHost(targetHost, targetPort, protocol);
uri = buildUri(uri, paraMap);
log.info("post uri: " + uri);
log.info("post content: " + xml);
HttpPost post = new HttpPost(uri);
StringEntity se = new StringEntity(xml,
StringUtils.isNotBlank(charset) ? charset : "utf-8");
se.setContentEncoding(new BasicHeader(HTTP.CONTENT_TYPE,
"application/xml"));
post.setEntity(se);
HttpResponse response = httpclient.execute(host, post);
if (HttpStatus.SC_OK == response.getStatusLine().getStatusCode()) {
HttpEntity entity = response.getEntity();
if (entity != null) {
result = EntityUtils.toString(entity);
log.info("post result: " + result);
}
} else {
log.error("post failed, status code: "
+ response.getStatusLine().getStatusCode());
}
return result;
}
public static void main(String[] args) throws Exception {
AESTool aes = new AESTool();
SignatureUtil signatureUtil = new SignatureUtil();
String appid = "canairport001";
String token = signatureUtil.findTokenById(appid);
String key = aes.findKeyById(appid);
long millis = System.currentTimeMillis();
String xml = "commons-lang commons-lang 2.5 paraMap = new HashMap();
paraMap.put("s", signature);
paraMap.put("a", appid);
paraMap.put("t", String.valueOf(millis));
paraMap.put("l", lol);
paraMap.put("o", "test");
HttpclientUtil util = new HttpclientUtil();
try {
String result = util.postXmlString("127.0.0.1", 8080, "http", null,
0, null, null, uri, paraMap, xml, "utf-8");
result = aes.decrypt(result, key);
System.out.println(result);
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
4.服务端代码：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.lang.StringUtils;
import org.apache.log4j.Logger;
import co.speedar.wechat.util.AESTool;
import co.speedar.wechat.util.SignatureUtil;
/**
* Servlet implementation class PsginfoServlet
*/
@WebServlet(urlPatterns = { "/psginfo.do" }, loadOnStartup = 1)
public class PsginfoServlet extends HttpServlet {
protected static final Logger log = Logger.getLogger(PsginfoServlet.class);
private static final long serialVersionUID = 6536688299231165548L;
private SignatureUtil signatureUtil = new SignatureUtil();
private AESTool aes = new AESTool();
/**
* @see HttpServlet#HttpServlet()
*/
public PsginfoServlet() {
super();
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
String echostr = request.getParameter("e");
log.info("echostr before echo: " + echostr);
String signature = request.getParameter("s");
String appid = request.getParameter("a");
String timestamp = request.getParameter("t");
String lol = request.getParameter("l");
long millis = Long.valueOf(timestamp);
// Need to check signature in product mode.
if (signatureUtil.isValid(signature, appid, lol, millis)) {
PrintWriter writer = response.getWriter();
log.info("echostr after echo: " + echostr);
writer.print(echostr);
writer.flush();
writer.close();
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
// Get request parameters.
String signature = request.getParameter("s");
String appid = request.getParameter("a");
String timestamp = request.getParameter("t");
String lol = request.getParameter("l");
String operation = request.getParameter("o");
long millis = Long.valueOf(timestamp);
// Get xml data.
String encoding = StringUtils
.isNotBlank(request.getCharacterEncoding()) ? request
.getCharacterEncoding() : "utf-8";
String requestXmlString = getXmlStringFromHttpRequest(request);
String digest = signatureUtil.digest(requestXmlString, "MD5");
// Check signature and digest.
if (StringUtils.equals(digest, lol)) {
if (signatureUtil.isValid(signature, appid, lol, millis)) {
try {
String key = aes.findKeyById(appid);
requestXmlString = aes.decrypt(requestXmlString, key);
log.info("received xml data:\n" + requestXmlString);
// 校验xml合法性并执行相应动作
String responseXmlString = doSomeThing(requestXmlString,
operation);
responseXmlString = aes.encrypt(responseXmlString, key);
log.info("responsed xml data:\n" + responseXmlString);
response.setCharacterEncoding(encoding);
PrintWriter writer = response.getWriter();
writer.print(responseXmlString);
writer.flush();
writer.close();
} catch (Exception e) {
log.error(e, e);
}
} else {
log.error("invalid signature");
}
} else {
log.error("invalid digest.");
}
}
/**
* TODO Write your own business here.
*
* @param xml
* @param operation
* @return
*/
private String doSomeThing(String xml, String operation) {
return "done";
}
/**
* Extract xml string form http request.
*
* @param request
* @return
* @throws IOException
*/
private String getXmlStringFromHttpRequest(HttpServletRequest request) {
String requestXmlString = "";
try {
InputStream inputStream = request.getInputStream();
String encoding = StringUtils.isNotBlank(request
.getCharacterEncoding()) ? request.getCharacterEncoding()
: "utf-8";
requestXmlString = getXmlStringFromInputStream(inputStream,
encoding);
encoding = null;
inputStream.close();
inputStream = null;
} catch (IOException e) {
log.error(e, e);
}
return requestXmlString;
}
/**
* Extract xml string from the inputStream.
*
* @param inputStream
* @param charsetName
* @return
*/
private String getXmlStringFromInputStream(InputStream inputStream,
String charsetName) {
String resultXmlString = "";
String tempString = null;
BufferedReader bufferedReader;
try {
bufferedReader = new BufferedReader(new InputStreamReader(
inputStream, charsetName));
tempString = bufferedReader.readLine();
while (tempString != null) {
resultXmlString += tempString;
tempString = bufferedReader.readLine();
}
tempString = null;
bufferedReader.close();
bufferedReader = null;
} catch (UnsupportedEncodingException e) {
log.error(e, e);
} catch (IOException e) {
log.error(e, e);
}
return StringUtils.trim(resultXmlString);
}
}
5.maven配置：
org.bouncycastle bcprov-jdk16 1.46 commons-lang commons-lang 2.5 org.apache.httpcomponents httpclient 4.2.5 org.apache.httpcomponents httpmime 4.2.5
六、结语
在本方案设计实现过程中，消息传递的框架采用的是Java开发者所熟悉的Servlet技术，摘要、签名、加密所采用的算法，以及所依赖的第三方jar也是比较有口碑又大众化的货，对于有类似需要的开发者来说，本方案具有一定的参考意义。远程传递消息框架以及生成签名的环节，主要是模仿了微信公众平台的消息交互方式以及生成签名的思路，而有所创新的一小点是，把消息密文的MD5值也参与到了签名运算中，增加了被仿冒的难度，同时也便于服务方校验消息在传递过程中是否有被第三方所篡改。
基于简化工程配置的考虑，本示例项目中没有使用spring，您可以在您的生产项目中把本示例中的代码改造成春哥的单例业务bean。密钥、token建议别直接写到春哥的context配置文件中，而是写在您的生产容器的环境变量中，防止被窃取。
另外，在本方案中生成签名的参数您可以酌情增减并调换顺序，替换签名所采用的算法，或者根据您的实际需要“个性化”一下您的加密算法，以期达到更好的安全效果。
Last but not the least，在密钥以及token交换的阶段，请采取您所认可的安全有效的方式进行，譬如面对面，微信，qq，微薄私信，电话，短信，邮件（可以参考本人之前写过的一篇文章：http://lixuanbin.iteye.com/blog/1544344）
七、参考资料
【Java加密与解密的艺术】——作者：梁栋，出版日期：2010年12月，ISBN：978-7-111-29762-8
http://stackoverflow.com/questions/4243650/aes-encryption-decryption-with-bouncycastle-example-in-j2me
http://stackoverflow.com/questions/6729834/need-solution-for-wrong-iv-length-in-aes
http://baike.baidu.com/view/941329.htm?fr=aladdin
http://baike.baidu.com/subview/133041/5358738.htm?fr=aladdin
http://baike.baidu.com/view/1228622.htm?fr=aladdin
http://baike.baidu.com/view/7636.htm?fr=aladdin