OverTheWire - Bandit - Level 22 to Level 23

Description:

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.
NOTE: Looking at shell scripts written by other people is a very useful skill. The script for this level is intentionally made easy to read. If you are having problems understanding what it does, try executing it to see the debug information it prints.

Commands you may need to solve this level

cron, crontab, crontab(5) (use "man 5 crontab" to access this)

Solution:

1. [Comment] Using SSH to connect the server
2. sp@simple-plan:~|=> ssh bandit22@bandit.labs.overthewire.org
   ...
   bandit22@bandit.labs.overthewire.org's password: Yk7owGAcWjwMVRwrTesJEwB7WVOiILLI
3. [Comment] Using cd command to change the shell working directory
4. bandit22@melinda:~$ cd /etc/cron.d/ 
5. [Comment] Using ls command to list directory contents
6. bandit22@melinda:/etc/cron.d$ ls
   

   boobiesbot-check	cronjob_bandit24	manpage3_resetpw_job	natas26_cleanup	semtex0-ppc	semtex6	vortex0
   cron-apt	eloi0	natas-session-toucher	php5	semtex10	semtex8	vortex20
   cronjob_bandit22	eloi1	natas-stats	semtex0-32	semtex12	semtex9	vulnbot0-check
   cronjob_bandit23	hintbot-check	natas25_cleanup	semtex0-64	semtex5	sysstat	vulnbot1-check

7. [Comment] Using cat command to output file's contents
8. bandit22@melinda:/etc/cron.d$ cat cronjob_bandit23
   * * * * * bandit23 /usr/bin/cronjob_bandit23.sh  &> /dev/null
9. [Comment] Using cat command to check the script content
10. bandit22@melinda:/etc/cron.d$ cat /usr/bin/cronjob_bandit23.sh
    #!/bin/bash
    
    myname=$(whoami)
    mytarget=$(echo I am user $myname | md5sum | cut -d ' ' -f 1)
    
    echo "Copying passwordfile /etc/bandit_pass/$myname to /tmp/$mytarget"
    
    cat /etc/bandit_pass/$myname > /tmp/$mytarget
    
11. [Comment] Try to execute the script to see the information it prints
12. bandit22@melinda:/etc/cron.d$ /usr/bin/cronjob_bandit23.sh 
    Copying passwordfile /etc/bandit_pass/bandit22 to /tmp/8169b67bd894ddbb4412f91573b38db3
13. [Comment] What we need to do is to find out which file would be used to store the password for next level
14. [Comment] Forge username for generating appropriate filename
15. bandit22@melinda:/etc/cron.d$ echo I am user bandit23 | md5sum | cut -d ' ' -f 1
    8ca319486bfbbc3663ea0fbe81326349
16. [Comment] Using cat command to fetch out the password
17. bandit22@melinda:/etc/cron.d$ cat /tmp/8ca319486bfbbc3663ea0fbe81326349
    jc1udXuA1tiHqjIsL8yaapX5XIAI6i0n
18. [Comment] Using exit command to disconnect connection to server
19. bandit22@melinda:/etc/cron.d$ exit
    logout
    Connection to bandit.labs.overthewire.org closed.
20. [Comment] It's done! Saving the password for next level.

Reference:

ssh	http://linuxcommand.org/man_pages/ssh1.html
ls	http://linuxcommand.org/man_pages/ls1.html
cat	http://linuxcommand.org/man_pages/cat1.html
exit	http://linuxcommand.org/man_pages/exit1.html
cd	http://linuxcommand.org/lc3_man_pages/cdh.html
find	http://linuxcommand.org/man_pages/find1.html
grep	http://linuxcommand.org/lc3_man_pages/grep1.html
sort	http://linuxcommand.org/lc3_man_pages/sort1.html
uniq	http://linuxcommand.org/man_pages/uniq1.html
strings	http://linuxcommand.org/man_pages/strings1.html
base64	http://linux.die.net/man/1/base64
tr	http://linuxcommand.org/man_pages/tr1.html
alias	http://linuxcommand.org/man_pages/alias1.html
mkdir	http://linuxcommand.org/man_pages/mkdir1.html
cp	http://linuxcommand.org/man_pages/cp1.html
xxd	http://linuxcommand.org/man_pages/xxd1.html
file	http://linuxcommand.org/man_pages/file1.html
mv	http://linuxcommand.org/man_pages/mv1.html
gzip	http://linuxcommand.org/man_pages/gzip1.html
bzip2	http://linuxcommand.org/man_pages/bzip21.html
tar	http://linuxcommand.org/man_pages/tar1.html
echo	http://linuxcommand.org/man_pages/echo1.html
nc	http://linuxcommand.org/man_pages/nc1.html
openssl	http://linuxcommand.org/man_pages/openssl1.html
diff	http://linuxcommand.org/man_pages/diff1.html
env	http://linuxcommand.org/man_pages/env1.html
cron	http://linuxcommand.org/man_pages/cron8.html
crontab	http://linuxcommand.org/man_pages/crontab1.html
cut	http://linuxcommand.org/man_pages/cut1.html
md5sum	http://linuxcommand.org/man_pages/md5sum1.html