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 = "<root><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name></root>";
String encrypted = aesTool.encrypt(xml, key);
System.out.println("encrypted: \n" + encrypted);
System.out.println("encrypted length: \n" + encrypted.length());
String decrypted = aesTool.decrypt(encrypted, key);
System.out.println("decrypted: \n" + decrypted);
System.out.println("decrypted length: \n" + decrypted.length());
boolean isSuccessful = StringUtils.equals(decrypted, xml);
System.out.println(isSuccessful);
}
}
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; <br/>
* @param encName
* , the algorithm name will be used, dafault to "MD5"; <br/>
* @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<String> srcList = new ArrayList<String>();
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: <br/>
* 1.根据appid获取该渠道的token;<br/>
* 2.根据appid、token、lol以及时间戳计算一次签名;<br/>
* 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 = "<root><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name><name>test</name></root>";
System.out.println(xmlString.getBytes().length);
String digest = generator.digest(xmlString, "MD5");
System.out.println(digest);
System.out.println(digest.getBytes().length);
String appid = "canairport001";
String token = generator.findTokenById(appid);
long millis = System.currentTimeMillis();
String signature = generator.generateSignature(appid, token, digest,
millis);
System.out.println(signature);
boolean isValid = generator.isValid(signature, appid, digest, millis);
System.out.println(isValid);
}
}
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<String, String> 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<Entry<String, String>> iterator = paraMap.entrySet()
.iterator();
while (iterator.hasNext()) {
Map.Entry<String, String> 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<String, String> 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 = "<dependency><groupId>commons-lang</groupId><artifactId>commons-lang</artifactId><version>2.5</version></dependency>";
xml = aes.encrypt(xml, key);
String lol = signatureUtil.digest(xml, "MD5");
String signature = signatureUtil.generateSignature(appid, token, lol,
millis);
log.info("lol: \n" + lol);
log.info("signature: \n" + signature);
String uri = "http://127.0.0.1:8080/demo/psginfo.do";
Map<String, String> paraMap = new HashMap<String, String>();
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：
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcprov-jdk16</artifactId>
<version>1.46</version>
</dependency>
<dependency>
<groupId>commons-lang</groupId>
<artifactId>commons-lang</artifactId>
<version>2.5</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.2.5</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpmime</artifactId>
<version>4.2.5</version>
</dependency>
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/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