This is a write-up for Alkatraz challenge from NahamCon CTF.
Here is another service running on port 50024, so lets connect to that port.
After connecting, nothing is displayed but the connection still open, So what could be guessed here is that it’s a shell. So by running ls command to list files, a flag.txt file is listed. But when I tried to display it’s contents, it gave me the below error.
it shows that the shell is /bin/rbash which is a restricted shell, that restricts some of the capabilities available to an interactive user session.
More info about Restricted shells: https://en.wikipedia.org/wiki/Restricted_shell
After spending a lot of time googling to bypass the restricted shell to read the contents of the flag.txt file, all the techniques failed but the below one just worked and I finally got the flag
flag{congrats_you_just_escaped_alkatraz}