NahamCon CTF 2023
Oh, shoot, I could have sworn there was a flag here. Maybe it's still alive out there?
Connect with:
# Password is "userpass"
ssh -p 32673 [email protected]
user@zombie:~$ ls -la
total 24
drwxr-sr-x 1 user user 4096 Jun 18 12:44 .
drwxr-xr-x 1 root root 4096 Jun 14 17:52 ..
-rwxr-xr-x 1 user user 3846 Jun 14 17:52 .bashrc
-rw-r--r-- 1 user user 17 Jun 14 17:52 .profile
-rwxr-xr-x 1 root root 131 Jun 14 17:52 .user-entrypoint.sh
user@zombie:~$ cat .user-entrypoint.sh
#!/bin/bash
nohup tail -f /home/user/flag.txt >/dev/null 2>&1 & #
disown
rm -f /home/user/flag.txt 2>&1 >/dev/null
bash -i
exitIt is hinted that the contents of flag.txt, despite being deleted, is still stored somewhere in the memory since it was ran via nohup
user@zombie:~$ ps
PID USER TIME COMMAND
1 root 0:00 /usr/sbin/sshd -D -e
7 root 0:00 sshd: user [priv]
9 user 0:00 sshd: user@pts/0
10 user 0:00 {.user-entrypoin} /bin/bash /home/user/.user-entrypoint.sh
11 user 0:00 tail -f /home/user/flag.txt
13 user 0:00 bash -i
16 user 0:00 ps
user@zombie:~$ ls -la /proc/11/fd
total 0
dr-x------ 2 user user 0 Jun 18 12:49 .
dr-xr-xr-x 9 user user 0 Jun 18 12:48 ..
lr-x------ 1 user user 64 Jun 18 12:49 0 -> /dev/null
l-wx------ 1 user user 64 Jun 18 12:49 1 -> /dev/null
l-wx------ 1 user user 64 Jun 18 12:49 2 -> /dev/null
lr-x------ 1 user user 64 Jun 18 12:49 3 -> /home/user/flag.txt (deleted)user@zombie:~$ cat /proc/11/fd/3
flag{6387e800943b0b468c2622ff858bf744}