Pentest Tools

Published on February 2nd, 2017 📆 | 6445 Views ⚑

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Printer Exploitation Toolkit: PRET

iSpeech
PRET is a new tool for printer security testing developed in the scope of a Master’s Thesis at Ruhr University Bochum. It connects to a device via network or USB and exploits the features of a given printer language. Currently PostScript, PJL and PCL are supported which are spoken by most laser printers. This allows cool stuff like capturing or manipulating print jobs, accessing the printer’s file system and memory or even causing physical damage to the device. All attacks are documented in detail in the Hacking Printers Wiki.

The main idea of PRET is to facilitate the communication between the end-user and the printer. Thus, after entering a UNIX-like command, PRET translates it to PostScript, PJL or PCL, sends it to the printer, evaluates the result and translates it back to a user-friendly format. PRET offers a whole bunch of commands useful for printer attacks and fuzzing.

Installation

PRET only requires a Python2 interpreter. For colored output and SNMP support however, third party party modules need to be installed:

# pip install colorama pysnmp

If running on a Windoze console and unicode characters are not displayed correctly, install the win_unicode_console module:

# pip install win_unicode_console

For experimental, ‘driverless’ printing (see print command), ImageMagick and GhostScript need to be installed:

# apt-get install imagemagick ghostscript

Usage

usage: pret.py [-h] [-s] [-q] [-d] [-i file] [-o file] target {ps,pjl,pcl}

positional arguments:
  target                printer device or hostname
  {ps,pjl,pcl}          printing language to abuse

optional arguments:
  -h, --help            show this help message and exit
  -s, --safe            verify if language is supported
  -q, --quiet           suppress warnings and chit-chat
  -d, --debug           enter debug mode (show traffic)
  -i file, --load file  load and run commands from file
  -o file, --log file   log raw data sent to the target

PRET requires a valid target and a printer language as arguments. The target can either be the IP address/hostname of a network printer (with port 9100/tcp open) or a device like /dev/usb/lp0 for a local USB printer. To quickly discover all network printers in your subnet using SNMP broadcast, simply run PRET without arguments:

./pret.py
No target given, discovering local printers

address          device                       uptime    status                 
───────────────────────────────────────────────────────────────────────────────
192.168.1.5      hp LaserJet 4250             10:21:49   Ready                 
192.168.1.11     HP LaserJet M3027 MFP        13 days    Paper jam             
192.168.1.27     Lexmark X792                 153 days   Ready                 
192.168.1.28     Brother MFC-7860DW           16:31:17   Sleep mode         

The printer language to be abused must be one of ps, pjl or pcl. Not all languages are supported by every printer, so you may wan’t to switch languages if you don’t receive any feedback. Each printer language is mapped to a different set of PRET commands and has different capabilities to exploit.

https://hacking-printers.net/wiki/index.php/Printer_Security_Testing_Cheat_SheetInstallation

https://github.com/RUB-NDS/PRET