In this article, we’ll cover Hash cracking - You wanna know what happens to your hashes? write-up as the Day 23 challenge of the Advent of Cyber event challenge. It involved hash functions and hash values, saving hashed passwords, cracking hashes, and finding the password of a password-protected document using tools like JohnRipper. We’re still at Wareville for SOC-mas!
Data Breach and Hash Values
Mayor Malware had an online account in a now-defunct forum that was breached, and all its user data was leaked. After checking online, we were able to retrieve the Mayor’s password in hashed format. It is listed below.
| Username | Password Hash |
mayor@email.thm | d956a72c83a895cb767bb5be8dba791395021dcece002b689cf3b5bf5aaa20ac |
We want to discover the original password. The first step in our approach is to figure out the type of the hash function. Then, we will try to hash different passwords from a password list until we find a match.
We have saved the above hash value in the /home/user/AOC2024/hash1.txt file for your convenience.
First, we will go to the AOC2024 directory and then display the content of hash1.txt.
Copy the displayed hash. Selecting the text in the split view will copy it for you.
Next, we start one tool that helps identify hashes by issuing the command python hash-id.py.
Paste the copied hash. Right-clicking with your mouse will paste the copied text in split view.
Finally, we quit the tool using CTRL+C.
The interaction is shown in the terminal output below:
VMTerminal
user@machine:~$ cd AOC2024/
user@machine:~/AOC2024$ cat hash1.txt
d956a72c83a895cb767bb5be8dba791395021dcece002b689cf3b5bf5aaa20ac
user@machine:~/AOC2024$ python hash-id.py
--------------------------------------------------
HASH: d956a72c83a895cb767bb5be8dba791395021dcece002b689cf3b5bf5aaa20ac
Possible Hashs:
[+] SHA-256
[+] Haval-256
Least Possible Hashs:
[+] GOST R 34.11-94
[+] RipeMD-256
[+] SNEFRU-256
[+] SHA-256(HMAC)
[+] Haval-256(HMAC)
[+] RipeMD-256(HMAC)
[+] SNEFRU-256(HMAC)
[+] SHA-256(md5($pass))
[+] SHA-256(sha1($pass))
--------------------------------------------------
HASH: ^C
Bye!
Next, we will try passwords from rockyou.txt, a popular password wordlist from a real data breach. The command is as follows:
john --format=raw-sha256 --wordlist=/usr/share/wordlists/rockyou.txt hash1.txt
john starts John the Ripper; the jumbo edition is installed on the machine
--format=raw-sha256 specifies the hash format, which we have figured out earlier that it is most likely a SHA-256
--wordlist=/usr/share/wordlists/rockyou.txt sets the wordlist that we will use
hash1.txt is the text file containing the hash value we are trying to crack
In our first attempt, john calculated the SHA-256 hash value for every password in rockyou.txt and compared it with the hash value in hash1.txt. Unfortunately, no password was found, as shown in the terminal output below:
VMTerminal
user@machine:~/AOC2024$ john --format=raw-sha256 --wordlist=/usr/share/wordlists/rockyou.txt hash1.txt
Using default input encoding: UTF-8
Loaded 1 password hash (Raw-SHA256 [SHA256 256/256 AVX2 8x])
Warning: poor OpenMP scalability for this hash type, consider --fork=2
Will run 2 OpenMP threads
Note: Passwords longer than 18 [worst case UTF-8] to 55 [ASCII] rejected
Press 'q' or Ctrl-C to abort, 'h' for help, almost any other key for status
0g 0:00:00:03 DONE (2024-11-03 09:49) 0g/s 4765Kp/s 4765Kc/s 4765KC/s (4510458faruk)..*7¡Vamos!
Session completed.
There is a high chance that Mayor Malware has made some transformation to his password. For example, he might have replaced a with 4 or added a couple of digits to his password. John can start from a long password list and attempt various common derivations from each of the passwords to increase its chances of success. This behaviour can be triggered through the use of rules. Various rules come bundled with John the Ripper’s configuration files; one is suited for lengthy wordlists, --rules=wordlist.
Adding the option --rules=wordlist to your john command line generates multiple passwords from each one. For instance, it appends and prepends single digits. It does various common substitutions; for example, a can be replaced with @, i can be replaced with !, and s can be replaced with $. Many more mutations and transformations are part of these rules. You can check all the underlying rules by checking the [List.Rules:Wordlist] section in /etc/john/john.conf, John’s configuration file. Unlike the first attempt, using John with this option should crack the hash for you:
john --format=raw-sha256 --rules=wordlist --wordlist=/usr/share/wordlists/rockyou.txt hash1.txt
We should note that john will not spend computing resources to crack an already-cracked password hash. Consequently, if you repeat a command that has successfully found a password earlier, you will get a message like “No password hashes left to crack (see FAQ)”. Let’s say that you executed the command listed above and you recovered the password; then, the next time you want to see that password, you would use john with the --show option, for example, john --format=raw-sha256 --show hash1.txt.
Data Breach and Hash Values
Glitch has discovered Mayor Malware’s password used on the breached online forum. Although there is a high chance that this password will be used to access other online accounts created by the Mayor, Glitch does not want to go that route as it would violate the local laws and regulations. Instead of attempting anything illegal, he focused on the data he discovered in the Mayor’s trash. There is one interesting-looking PDF file that happens to be password-protected. You can help Glitch break it.
The first thing you need to do is to convert the password-protected file into a format that john can attack. Luckily, John the Ripper jumbo edition comes with the necessary tools. The different tools follow the naming style “format2john”. The terminal below shows a few examples.
VMTerminal
user@machine:~/AOC2024$ ls /opt/john/*2john*
/opt/john/1password2john.py /opt/john/ethereum2john.py /opt/john/openssl2john.py
/opt/john/7z2john.pl /opt/john/filezilla2john.py /opt/john/padlock2john.py
/opt/john/DPAPImk2john.py /opt/john/geli2john.py /opt/john/pcap2john.py
/opt/john/adxcsouf2john.py /opt/john/gpg2john /opt/john/pdf2john.pl
/opt/john/aem2john.py /opt/john/hccap2john /opt/john/pdf2john.py
/opt/john/aix2john.pl /opt/john/hccapx2john.py /opt/john/pem2john.py
/opt/john/aix2john.py /opt/john/htdigest2john.py /opt/john/pfx2john.py
[...]
You are interested in a password-protected PDF; therefore, pdf2john.pl should do the job perfectly for you. In the terminal below, you can see how to create a hash challenge from a PDF file. This hash value can later be fed to john to crack it.
VMTerminal
user@machine:~/AOC2024$ pdf2john.pl private.pdf > pdf.hash
user@machine:~/AOC2024$ cat pdf.hash
private.pdf:$pdf$2*3*128*-1028*1*16*c1e77e30a0456552cb8a5327241559bd*32*3dc175eae491edc29b937e4fdbda766c00000000000000000000000000000000*32*6a1b5158d8d6dd9e8380f87b624da6cc936075fd41dc3c76acf2d90db62e4a27
The first step to consider would be trying a long wordlist such as rockyou.txt; moreover, you might even use a rule such as --rules=wordlist to test derived passwords. In this case, neither approach works; Mayor Malware has picked a password that does not exist in these public wordlists and is not derived from any word found there. Knowing Mayor Malware, we see what he holds dear, which can hint at what he would consider for his password. Therefore, you need to create your own wordlist with the following words:
Fluffy
FluffyCat
Mayor
Malware
MayorMalware
And save it as wordlist.txt. We have saved the above words in the /home/user/AOC2024/wordlist.txt file for your convenience. Consequently, our command would be:
john --rules=single --wordlist=wordlist.txt pdf.hash
--rules=single covers more modification rules and transformations on the wordlist
--wordlist=wordlist.txt is the custom and personalized wordlist that we created
pdf.hash is the hash generated from the password-protected document
Now, you have gained all the necessary knowledge to tackle the questions below and uncover what Mayor Malware has been hiding in his password-protected document.
Crack the hash value stored in hash1.txt. What was the password? fluffycat12
What is the flag at the top of the private.pdf file? THM{do_not_GET_CAUGHT}
To learn more about cryptography, we recommend the Cryptography module. If you want to practice more hash cracking, please consider the John the Ripper: The Basics room.
Thank you for reading this article. Please leave a comment with your thoughts, areas for improvement, other suggestions, and questions. Stay secure until the next one!
