Let's start a second web challenge on HTB, this one is called Emdee five for life. It's only worth 20 points too, so it should be an easy one...

The only description we have before starting the challenge instance is :

Can you encrypt fast enough?

After starting the challenge instance, we land on this webpage :

The webpage provide us a string, and the purpose is to send the MD5 hash of this string.

Easy, let's go to this website to encrypt the string : https://md5decrypt.net/

Ok, we now know that the MD5 hash of mKLopMuyMYtWvvflbpNi is 8eb5f6b4e268fcb945adae6e5b07947e, so let's validate the challenge !

Aoutch ! It was too easy to be real, the webpage tell us that we were too slow and give us a new string to encrypt.

Let's see what happen when we click on Submit button with BurpSuite :

A POST request with data "hash=ourhash" is sent, and we can see that the POST request contain a Cookie header PHPSESSID=tgr5iis70c01731l6h9o1masr7.

Now that we have these information we can create a python script that will send the POST request with the MD5 hash of the string and without forgetting the cookie.

import requests, hashlib
from bs4 import BeautifulSoup

url = "http://docker.hackthebox.eu:30966"

s = requests.session()
response = s.get(url)

soup = BeautifulSoup(response.content, "lxml")

str = soup.h3.string
hash = hashlib.md5(str.encode()).hexdigest()

myobj = {'hash': hash}

flag = s.post(url, data = myobj)


I use requests.session() to use the cookie in the POST request, I also use the python library BeautifulSoup which allows to get the html of the webpage. Then I use hashlib which allows to encrypt the string into MD5. And finaly I send the POST request and print the server response who contain the flag.

Don't forget to add execution right to the python script :

chmod +x md5_chall.py

And let's execute it :

python md5_chall.py

BINGO ! The flag is in the html response !