Snake by Hack the box - My writeup

Edoardo (chap) — Sat, 08 Jun 2019 06:41:04 +0000

Disclaimer

If you're uncomfortable with spoilers stop reading now.

Challenge

While waiting for SwagShop's takedown in order to publish my writeup, I took a chance to solve a couple of challenges available on HackTheBox, starting from Snake.

Snake is a reversing challenge by 3XPL017, you can find it here.

After downloading and unzipping the archive with the password provided we're presented with a Python script named snake.py, we'll try and run it:

After assigning us a random number is asks for a username and a password, we'll dig into that by taking a look at the code.

We can notice that there are a lot of variables declared, the one which stands out is slither since it seems to be the one required in order to be properly identified when prompted for the username.

if user_input == slither:
    pass

Therefore we can add:

print slither

In order to print the variable slither, which is the needed username. The script part will look like this:

Once we run it we get:

Yes, anaconda makes sense and it is indeed the needed username.

Let's move on to the password, which is generated by this part of the script:

We can see that passes is compared to (chr(char))

Functions:

str() – returns a string
chr() – returns a character, after that takes in a parameter of a unicode digit

Variables:

char – one element in the array chars
chars – initialized as an empty array

The array chars contains:

chars = []

And:

for key in keys:
    keys_encrypt = lock ^ key
    chars.append(keys_encrypt)
for chain in chains:
    chains_encrypt = chain + 0xA
    chars.append(chains_encrypt)

There is also a break which terminates the loop even if a single character matches the user given input.

The simplest way to solve this is to print the characters before being asked for the password, we can do this by modifying the script:

And, if we run it we get:

The password is working, and due to the fact that keys contains the first 10 characters of the password, we can assume we need to enter them in order to properly solve the challenge.

The flag format is HTB{user:password}, so the proper way to enter it is HTB{anaconda:udvvrjwa$$}.

Solved!

DEV Community: Edoardo (chap)

Snake by Hack the box - My writeup

Disclaimer

Challenge