Difference between revisions of "PCL"

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Revision as of 18:33, 8 January 2017

The Printer Command Language (PCL) as specified in [1] is a minimalist page description language supported by a wide variety of vendors and devices. Along with PostScript, PCL represents a de facto standard printer language. Similar to PostScript, it's origins date back to the early 80s with PCL 1 introduced by HP in 1984 for inkjet printers. PCL 3 and PCL 4 added support for fonts and macros which both can be permanently downloaded to the device – however only referenced to by a numeric id, not by a file name, as direct access to the file system is not intended. PCL 1 to 5 consist of escape sequences followed by one or more ASCII characters representing a command to be interpreted. PCL 6 Enhanced or ‘PCL XL’ uses a binary encoded, object-oriented protocol [2]. If not stated otherwise, traditional PCL 5e is used in this work. An example PCL document to print ‘Hello world’ is given below:

 <Esc>EHello world

Due to its limited capabilities, PCL is hard to exploit from a security perspective unless one discovers interesting proprietary commands in some printer manufacturers's PCL flavour. The PRET tool implements a virtual, PCL-based file system which uses macros to save file content and metadata in the printer's memory. This hack shows that even a device which supports only minimalist page description languages like PCL can be used to store arbitrary files like copyright infringing material. Although turning a printer into a file sharing service is not a security vulnerability per se, it may apply as ‘misuse of service’ depending on the corporate policy.



  1. PCL5 Printer Language Technical Reference Manual, HP Inc., 1992
  2. PCL XL Feature Reference Protocol Class 2.0, HP Inc., 2000