Re: vulnerabilities of postscript printers
From: Ian Farquhar - Network Security Group (Ian.Farquhar_at_Sun.COM)
Date: Wed, 28 Jan 2004 09:12:58 +1100 To: der Mouse <mouse@Rodents.Montreal.QC.CA>
der Mouse wrote:
> Third, it would not be easy to usurp control of the printer's CPU to
> start with. PostScript jobs are run in a relatively restricted
> virtual-machine environment, and it is difficult for a job to affect
> the environment provided for future jobs - generally, it needs to
> provide the correct value for a 32-bit "password". (Such things can be
> set insecurely, certainly, but that's no different, really, from having
> a Unix box with root's password set to "root": it's admin error.)
The undocumented, machine-specific cexec interface allows the
downloading and execution of binary images which are run by the RIP CPU.
It's purpose, I was told, was to allow drivers to patch bugs in the
firmware if needed, but it's most (in)famous use was Apple's Laserwriter
bitmap smoothing code which ran natively on the LW's 68000 for speed.
If you could figured out the cexec encryption - and I'd bet money it was
very similar to the now-documented eexec encryption - running code
natively on the RIP's CPU would be fairly easy.
It's been several years since I looked, but cexec was present on most
"genuine Adobe" firmwares I investigated.
-- Ian Farquhar Senior Network Security Engineer Network Security Group Sun Microsystems Level 2, 828 Pacific Hwy Gordon, NSW, 2072 Australia Email: firstname.lastname@example.org Phone: +61 2 9498 0470 (External) Phone: 57470 (Sun Internal) Mobile: +61 414 967 178 Fax: +61 2 9498 0460