100 points
Category: General Skills
Tags : #crontab
How to automate tasks to run at intervals on linux servers? Additional details will be available after launching your challenge instance.
Automating and scheduling of tasks is typically the role of cron jobs, managed by the cron table.
$ crontab -l
no crontab for picoplayer
$ crontab -e
no crontab for picoplayer - using an empty one
update-alternatives: error: no alternatives for editor
/usr/bin/sensible-editor: 25: editor: not found
/usr/bin/sensible-editor: 28: nano: not found
/usr/bin/sensible-editor: 31: nano-tiny: not found
/usr/bin/sensible-editor: 34: vi: not found
Couldn't find an editor!
Set the $EDITOR environment variable to your desired editor.
crontab: "/usr/bin/sensible-editor" exited with status 1
Ok, lets try viewing the cron table for root :
picoplayer@challenge:~$ crontab -u root -l
must be privileged to use -u
picoplayer@challenge:~$ sudo -l
[sudo] password for picoplayer:
Sorry, user picoplayer may not run sudo on challenge.
Still no luck.
Lets try viewing the system-wide crontab :
$ cat /etc/crontab
# picoCTF{........redacted........}
Actual flag value redacted for the purposes of this write up.
Whilst trying to work out the above solution during the event, I did happen to accidently view the flag visible in /challenge/metadata.json, which didn't seem like the intended solution and likely a permissions misconfiguration.