# UnforgottenBits | PicoCTF 2023

Author: LT 'syreal' Jones
Description
Download this disk image and find the flag. Note: if you are using the webshell, download and extract the disk image into /tmp not your home directory.

There are no hints here, but there are plenty on the disk!

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I will work in Flare Os
I import the image in Autopsy.

## Analizing with Autopsy


Interesting files


**Notes**
chizazerite
guldulheen
I keep forgetting this, but it starts like: yasuoaatrox...

**Email with interessting data**

subject: Deleting emails
to: Sten Walker <[e-mail]>
from: Bob Bobberson <[e-mail]>

Yone,

This is just a reminder to delete all of our emails and scrub your trash can as well. We don't want our precious light falling into the wrong hands. You know the punishment for such 'crimes'.

To the Light and All it reveals,
- The Azerite Master

**Interesting data**
[e-mail]

Inspecting this particular email on keywordHints leads us to a interesing email with a link
https://xkcd.com/936/
This website talks about password strengt and how to use 4 random common words as a password


This challenges is about finding a password first

In the disk i also find
A log with a conversation with intersteing information

[08:12] <yone786> Ok, let me give you the keys for the light.
[08:12] <avidreader13> I’m ready.
[08:15] <yone786> First it’s steghide.
[08:15] <yone786> Use password: akalibardzyratrundle
[08:16] <avidreader13> Huh, is that a different language?
[08:18] <yone786> Not really, don’t worry about it.
[08:18] <yone786> The next is the encryption. Use openssl, AES, cbc.
[08:19] <yone786> salt=0f3fa17eeacd53a9 key=58593a7522257f2a95cce9a68886ff78546784ad7db4473dbd91aecd9eefd508 iv=7a12fd4dc1898efcd997a1b9496e7591
[08:19] <avidreader13> Damn! Ever heard of passphrases?
[08:19] <yone786> Don’t trust em. I seed my crypto keys with uuids.
[08:20] <avidreader13> Ok, I get it, you’re paranoid.
[08:20] <avidreader13> But I have no idea if that would work.
[08:21] <yone786> Haha, I’m not paranoid. I know you’re not a good hacker dude.
[08:21] <avidreader13> Is there a better way?
[08:22] * yone786 yawns.
[08:24] <yone786> You’re ok at hacking. I’m good at writing code and using it
[08:24] <avidreader13> What language are you writing in?
[08:26] <yone786> C
[08:26] <avidreader13> Oh, I see.
[08:26] <yone786> I’m glad you like it. I’m sure you wouldn’t understand half of what I was doing.
[08:28] <avidreader13> I understand enough, but I do wish you wouldn’t take so much time with it.
[08:28] <yone786> Sorry. Well, I wish you could learn some things.
[08:29] <avidreader13> But it’s an incredible amount of time you spend on it.
[08:29] <yone786> Haha, don’t take it like that.

**Interessting**
**Aes Key with the salt
salt=0f3fa17eeacd53a9 key=58593a7522257f2a95cce9a68886ff78546784ad7db4473dbd91aecd9eefd508 iv=7a12fd4dc1898efcd997a1b9496e7591
password: akalibardzyratrundle**

#leagueoflegends
0x00000030: 2E 6C 6F 67 00 00 00 00 00 00 00 00 00 00 00 00 .log
Seams like it is a login to leage of legends account

<yone786> First it’s steghide.
It seems like there are a set of instructions

I also found theese pictures, they are in bmp format, the the ones in this writeup are not the original


I will try steghide on them, for that i switch over to Kali

## Extractring with Steghide

I extracted 3 encrypted files

-rw-r--r-- 1 root root      56784 Nov 17 04:27 dracula.txt.enc
-rw-r--r-- 1 root root      55024 Nov 17 04:28 frankenstein.txt.enc
-rw-r--r-- 1 root root      26464 Nov 17 04:25 les-mis.txt.enc

Theese where extracted from
1.bmp, 154-2.bmp, 156-3.bmp the las picture that looks like a book requiere another password.

root@kali:~/Documents/CTF/pico2023/inforgottenBits# steghide extract -sf 1.bmp
Enter passphrase: 
wrote extracted data to "les-mis.txt.enc".
root@kali:~/Documents/CTF/pico2023/inforgottenBits# steghide extract -sf 154-2.bmp
Enter passphrase: 
wrote extracted data to "dracula.txt.enc".
root@kali:~/Documents/CTF/pico2023/inforgottenBits# steghide extract -sf 156-3.bmp
Enter passphrase: 
wrote extracted data to "frankenstein.txt.enc".
root@kali:~/Documents/CTF/pico2023/inforgottenBits# steghide extract -sf 158-7.bmp
Enter passphrase: 
steghide: could not extract any data with that passphrase!

## Possibly Fake rabbithole here

I made a script tha decrypts the files

from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends import default_backend
import base64

# Replace these with your actual key, salt, and iv values
salt = bytes.fromhex("0f3fa17eeacd53a9")
key = bytes.fromhex("58593a7522257f2a95cce9a68886ff78546784ad7db4473dbd91aecd9eefd508 ")
iv = bytes.fromhex("7a12fd4dc1898efcd997a1b9496e7591")

# Function to decrypt data
def decrypt(data, key, iv):
    backend = default_backend()
    cipher = Cipher(algorithms.AES(key), modes.CBC(iv), backend=backend)
    decryptor = cipher.decryptor()
    return decryptor.update(data) + decryptor.finalize()

# just change the name of encrypted files 
with open("dracula.txt.enc", "rb") as file:
    encrypted_data = file.read()

# Decrypt the data
decrypted_data = decrypt(encrypted_data, key, iv)

# Write the decrypted data to a file
with open("dracula.txt", "wb") as file:
    file.write(decrypted_data)

print("Decryption complete. Output written to output.txt")

This gave me the frankenstein, dracula and les-miserables book.

For example the book frankenstein had hidden text at the end, i found the missing part with help of **"El Chat"**.

Frankenstein 
    
Before this I was not unacquainted with the more obvious laws of
electricity. On this occasion a man of great research in natural
philosophy was with us, and excited by this catastrophe, he entered on
the explanation of a theory which he had formed on the subject of
electricity and galvanism, which was at once new and astonishing to me.
All that he said threw greatly into the shade Cornelius Agrippa,
Albertus Magnus, and Paracelsus, the lords of my imagination; but by
some fatality the overthrow of these men disinclined me to pursue my
 
xxxxxxxxxxx = accostomed studies.

    
Dracula 
When I had finished, he said:--

"I am glad that it is old and big. I myself am of an old family, and to
live in a new house would kill me. A house cannot be made habitable in a
day; and, after all, how few days go to make up a century. I rejoice
also that there is a chapel of old times. We Transylvanian nobles love
not to think that our bones may lie amongst the common dead. I seek not
gaiety nor mirth, not the bright voluptuousness of much sunshine and
sparkling waters which please the young and gay. I am no longer young;
and my heart, through weary years of mourning over the dead, is not
attuned to mirth. Moreover, the walls of my castle are broken; the
shadows are many, and the wind breathes cold through the broken
battlements and casements. I love the shade and the shadow, and would
be alone with my thoughts when I may." Somehow his words and his look
did not seem to accord, or else it was that his cast of face made his
smile look malignant and saturnine.

 
xxxxxxxxxxxx
Presently he got up and said; — 
'For tonight I am your guest—we will remain in all night, and we shall both be happy in each other's company.'"    

Les miserables
    
About the epoch of the coronation, some petty affair connected with his
curacy—just what, is not precisely known—took him to Paris. Among other
powerful persons to whom he went to solicit aid for his parishioners
was M. le Cardinal Fesch. One day, when the Emperor had come to visit
his uncle, the worthy Curé, who was waiting in the anteroom, found
himself present when His Majesty passed. Napoleon, on finding himself
observed with a certain curiosity by this old man, turned round and
said abruptly:—

    xxxxxxxx
    “— 'What is this?' said the Emperor briskly, 'who is this man?'”

## Back to Autopsy

Seems like yone likes Leage of Legends

we have this
**I keep forgetting this, but it starts like: yasuoaatrox...**

yasuo aatrox  chizazerite  guldulheen
    
yasuoaatroxchizazeriteguldulheen

Seems like a 4 word password

root@kali:~/Documents/CTF/pico2023/inforgottenBits# steghide extract -sf 158-7.bmp
Enter passphrase: 
steghide: could not extract any data with that passphrase!

## Another rabbithole :(

Lets look at the names

- > yasuo google says its a Leage of Legends champ
- > aatrox google says its a Leage of legends champ
- > chizazerite Google finds nothing
- > guldulheen Google finds nothing

I am missing two leage of legends names to have a 4 word password.

## Using Stegcracker
I came across a tool named stegcracker that launch a dictionary attack on the bmp file and extract the data.

https://github.com/Paradoxis/StegCracker

The tool can be installed easy in Kali.

For that i ned to create a dictionary and i need a list.

I have **yasuo and aatrox** that are two champeons of Leage of Legends.
I found a list if 160 champeons in a reddit.

That list i save as **champs.txt**

Then i use a script that will concatenate the two champeons with the other 160 and make 25600 combiantions.

**Python script for wordlist**

    # Starting string
strStart = "yasuoaatrox"

# File names
strInputFileName = "champs.txt"
strOutputFileName = "newChampsDictionary.txt"

# Open the file containing the names
with open(strInputFileName, "r") as fileInput:
    lstNames = fileInput.readlines()

with open(strOutputFileName, "w") as fileOutput:
    for strName1 in lstNames:
        for strName2 in lstNames:
            
            strCombined = strStart + strName1.strip().lower() + strName2.strip().lower() + "\n"
            fileOutput.write(strCombined)

print(f"Data written to {strOutputFileName}")

**Result**

root@kali:~/Documents/CTF/pico2023/inforgottenBits# python3 wordlist.py
Data written to newChampsDictionary.txt

Now i can run the Stegcracker with this .txt file and and possible get a passoword or even crack the bmp igame an extract its data.

## It worked!!


The password is

Your file has been written to: 158-7.bmp.out
yasuoaatroxashecassiopeia

Now i can try to open the file with the aes key i get in autopsy.

I try this command:

root@kali:~/Documents/CTF/pico2023/inforgottenBits# 
openssl aes-256-cbc d -S 0f3fa17eeacd53a9 -K 58593a7522257f2a95cce9a68886ff78546784ad7db4473dbd91aecd9eefd508 
-iv 7a12fd4dc1898efcd997a1b9496e7591 -in 158-7.bmp.out -out resultFlag.txt
aes-256-cbc: Use -help for summary.

And it dont work :(
This is because its not the right key.
I need to find the key in autopsy

## Back to Autopsy again...Slack Data or Hidden metadata
Where to start.. i was stuck here for a long time, digging for info on the web, the chat.
Understanding the name of the challenge and then i came across discovering hidden metadata in autopsy.
For example: If there is a process in a text file, som bits can still be pressent. Like temp files on windows, they are not visible but we need to enable them. This is called enabling Slack Data. This can be enabled in options.

And i came across some data content in


It looks like binary data, but i dont get much if i try to decode it with a normal decoder.

Digging for a while, i came across the browsing history


https://en.wikipedia.org/wiki/Church_encoding
https://cs.lmu.edu/~ray/notes/numenc/
https://www.wikiwand.com/en/Golden_ratio_base

https://www.wikiwand.com/en/Golden_ratio_base

What is the Golden Ratio?
The Golden Ratio, often symbolized by the Greek letter φ (phi), is a special number approximately equal to 1.61803399. It's found by solving the equation φ = 1 + 1/φ, which can also be expressed as φ = (1 + √5) / 2. This number has unique mathematical properties and appears in various areas of art, architecture, and nature.

What is Base-φ or the Golden Ratio Base?
Base-φ is a numeral system that uses the Golden Ratio (φ) as its base. In this system, the position of each digit affects its value based on powers of φ, similar to how in base-10 the position is based on powers of 10.

In essence, the Golden Ratio base is a unique way of representing numbers using the Golden Ratio as the base. It's an unusual system compared to our standard decimal system because it operates on different mathematical principles and uses only two digits.

## Decrypting the Slack Data

With the help of el Papi Chat i made a python script that takes the slack data from a text file and runs it through a golden ratio algorythm.

**The Script**

import sys
from math import sqrt

# Check if a filename is provided as a command-line argument
if len(sys.argv) < 2:
    print("Usage: python script.py filename")
    sys.exit(1)

# Get the file name from the command-line argument
strFilename = sys.argv[1]

# Calculate the Golden Ratio
fPhi = (1 + sqrt(5)) / 2

# Read the data from the file and strip the newline at the end
with open(strFilename, "r") as file:
    strSlack = file.readlines()[0].strip()

# Initialize the answer string
strAns = ''

# Loop over the numbers, each having 11 digits, a decimal point, then 3 digits (15 chars in total)
for j in range(len(strSlack) // 15):
    # Grab the current segment
    strFirst = strSlack[j * 15 : (j + 1) * 15]

    # Split the segment into parts before and after the decimal point
    strB4 = strFirst[:-4]
    strAft = strFirst[-3:]
    fSum = 0

    # Add the powers of φ for each digit before the decimal point
    for i in range(len(strB4)):
        if strB4[i] == '1':
            fSum += pow(fPhi, 10 - i)

    # Add the powers of φ for each digit after the decimal point
    for i in range(len(strAft)):
        if strAft[i] == '1':
            fSum += pow(fPhi, -(i + 1))

    # Round to the nearest integer and convert to ASCII
    strAns += chr(int(fSum + 0.5))

# Print the result
print(strAns)
                     

## It worked
I run the script and get the key


salt=2350e88cbeaf16c9
key=a9f86b874bd927057a05408d274ee3a88a83ad972217b81fdc2bb8e8ca8736da
iv=908458e48fc8db1c5a46f18f0feb119f

## The flag

I tried the openssl command but it didnt work, so i used the python script extract.py that i used earlier and i just replaced the keys.

root@kali:~/Documents/CTF/pico2023/inforgottenBits# python extract.py
Decryption complete. Output written to decryptedFlag.txt


What a ride.

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