From Sales Pitch we discover the server has some internal bound services, most notably telnet (port 23) - These are listed on the internal management page. It is only accessible from inside the network however.

Fortunately, telnet is a text based protocol, so we can easily just do a proxyHTTP CONNECT to it via the proxy.

$> telnet 3128

We need to authenticate (token is found on the backend management page)

Token: 7e8e816557776037a15f

We are now connected to the home baked shell implementation. We need to break out. Get root.

We realise it has a ping command, which uses system ping and takes arguments. We tell ping to only execute once, and chain another command to it -> bash.

$> ping -c1 && bash

We now have a shell. From here we can:

$> cat flag.txt

And thus revealing the flag.

After we found the flag, a hint was revealed:

Maybe try ping “and”