Lab: Authentication bypass via information disclosure

APPRENTICE

This lab's administration interface has an authentication bypass vulnerability, but it is impractical to exploit without knowledge of a custom HTTP header used by the front-end.

To solve the lab, obtain the header name then use it to bypass the lab's authentication. Access the admin interface and delete Carlos's account.

You can log in to your own account using the following credentials: wiener:peter

Access the lab

Solution

In Burp Repeater, browse to GET /admin. The response discloses that the admin panel is only accessible if logged in as an administrator, or if requested from a local IP.
Send the request again, but this time use the TRACE method:
TRACE /admin
Study the response. Notice that the X-Custom-IP-Authorization header, containing your IP address, was automatically appended to your request. This is used to determine whether or not the request came from the localhost IP address.
Go to "Proxy" > "Options", scroll down to the "Match and Replace" section, and click "Add". Leave the match condition blank, but in the "Replace" field, enter:
X-Custom-IP-Authorization: 127.0.0.1
Burp Proxy will now add this header to every request you send.
Browse to the home page. Notice that you now have access to the admin panel, where you can delete Carlos.