ctf-writeups

Writeups for CTFs solved by DarkKnight

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Bandit Level 21 –> Level 22

Level Goal

A program is running automatically at regular intervals from cron, the time-based job scheduler. Look in /etc/cron.d/ for the configuration and see what command is being executed.

Commands you may need to solve this level

cron, crontab, crontab(5) (use “man 5 crontab” to access this)

Solution

change dir to /etc/cron.d then see its content

bandit21@bandit:~$ cd  /etc/cron.d/ 
bandit21@bandit:/etc/cron.d$ ls
cronjob_bandit15_root  cronjob_bandit22  cronjob_bandit24
cronjob_bandit17_root  cronjob_bandit23  cronjob_bandit25_root

Open cronjob_bandit22 to see the command

bandit21@bandit:/etc/cron.d$ cat cronjob_bandit22
@reboot bandit22 /usr/bin/cronjob_bandit22.sh &> /dev/null
* * * * * bandit22 /usr/bin/cronjob_bandit22.sh &> /dev/null
bandit21@bandit:/etc/cron.d$ cat /usr/bin/cronjob_bandit22.sh
#!/bin/bash
chmod 644 /tmp/t7O6lds9S0RqQh9aMcz6ShpAoZKF7fgv
cat /etc/bandit_pass/bandit22 > /tmp/t7O6lds9S0RqQh9aMcz6ShpAoZKF7fgv

this bash code mean that level pass copy to file in tmp directory at regular intervals lets open it

bandit21@bandit:/etc/cron.d$ cat /tmp/t7O6lds9S0RqQh9aMcz6ShpAoZKF7fgv
Yk7owGAcWjwMVRwrTesJEwB7WVOiILLI

Password

Yk7owGAcWjwMVRwrTesJEwB7WVOiILLI