Machine Synopsis

Gofer is a Hard Difficulty Linux machine featuring a web proxy secured by Basic HTTP authentication, which can be circumvented through an unfiltered method. The web proxy permits select protocols, including HTTP/HTTPS and gopher—a vintage rival of HTTP that some tools like `cURL` still support. Its key advantage lies in facilitating interaction with internal services such as FTP, SSH, and SMTP. With the presence of an SSRF vulnerability and the utility of gopher, the machine allows us to engage with these internal services as though we were part of the network. The aim is to exploit this by sending a malicious `OpenDocument` via email to an employee known for opening all received documents, capitalizing on the SSRF flaw. After gaining our initial shell, further network sniffing reveals a developer testing the proxy without encryption, exposing clear-text credentials. The final step involves exploiting a binary through a "Use after free" vulnerability to escalate privileges.