View source for Factory defaults

Resetting a device to factory defaults is a security-critical functionality as it overwrites protection mechanisms like user-set passwords. This can usually be done by pressing a special key combination on the printer's control panel. Performing such a cold reset only takes seconds and therefore is a realistic scenario for local attackers or penetration testers, who can for example sneak into the copy room at lunchtime. However, physical access to the device is not always an option. The question comes up, if printer vendors have implemented the possibility to perform factory resets on-line using printer control or page description languages. They have, as discussed in this article.

== SNMP ==

The Printer-MIB <ref>''[https://www.ietf.org/rfc/rfc3805.txt RFC3805: Printer MIB v2]'', R. Bergman, I. McDonald and H. Lewis, 2004</ref> defines the ''prtGeneralReset'' Object (OID 1.3.6.1.2.1.43.5.1.1.3.1) which allows an attacker to restart the device (''powerCycleReset(4)''), reset the NVRAM settings (''resetToNVRAM(5)'') or restore factory defaults (''resetToFactoryDefaults(6)'') using [[SNMP]]. This feature/attack is supported by a large variety of printers and removes all protection mechanisms like user-set passwords for the embedded web server. While protection mechanisms can be efficiently bypassed, a practical drawback of this approach is that all static IP address configuration will be lost. If no [https://de.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol DHCP] service is available, the attacker will not be able to reconnect to the device anymore after resetting it to factory defaults.

'''How to test for this attack?'''

Resetting the device to factory default can be accomplished using ''snmpset'' command as shown below:

<syntaxhighlight lang=sh>
snmpset -v1 -c public printer 1.3.6.1.2.1.43.5.1.1.3.1 i 6
</syntaxhighlight>

'''Who can perform this attack?'''

Anyone who can send network packets to port 161/udp of the printer device.

== PML/PJL ==

In many scenarios an attacker does not have the capabilities to perform SNMP requests because of firewalls or unknown SNMP community strings. On HP devices however, SNMP can be transformed into its [[PML]] representation and embed the request within a legitimate print job. This allows an attacker to restart and/or reset the device to factory defaults within ordinary print jobs as shown below:

 @PJL DMCMD ASCIIHEX="040006020501010301040106"

'''How to test for this attack?'''

On HP printers, restarting or resetting the device can easily be reproduced using [[PRET]]:

 ./pret.py -q printer pjl
 Connection to printer established
 
 Welcome to the pret shell. Type help or ? to list commands.
 printer:/> reset
 printer:/> restart

'''Who can perform this attack?'''

Anyone who can print, for example through [[USB drive or cable]], [[Port 9100 printing]] or [[Cross-site printing]].

== PostScript ==

PostScript offers a similar feature: The ''FactoryDefaults'' system parameter, ‘a flag that, if set to true immediately before the printer is turned off, causes all nonvolatile parameters to revert to their factory default values at the next power-on’ <ref>''[https://www.adobe.com/products/postscript/pdfs/PLRM.pdf PostScript Language Reference Manual, 3rd Edition]'', Adobe Systems Inc., 1999, p. 751</ref>. Restarting the printer on the other hand can be accomplished by SNMP and PML as described above. It must be noted that PostScript itself also has the capability to restart its environment but it requires a [[Credential disclosure|valid password]]. The PostScript interpreter however can be put into an infinite loop as discussed in [[document processing]] DoS attacks which forces the user to manually restart the device and thus reset the PostScript password.

Reset PostScript system parameters to factory defaults:

<syntaxhighlight lang=postscript>
<< /FactoryDefaults true >> setsystemparams
</syntaxhighlight>

Restart the PostScript interpreter and virtual memory:

<syntaxhighlight lang=postscript>
true 0 startjob systemdict /quit get exec
</syntaxhighlight>

'''How to test for this attack?'''

Restarting or resetting a printer's PostScript interpreter can easily be reproduced using [[PRET]]:

 ./pret.py -q printer ps
 Connection to printer established
 
 Welcome to the pret shell. Type help or ? to list commands.
 printer:/> reset
 printer:/> restart

'''Who can perform this attack?'''

Anyone who can print, for example through [[USB drive or cable]], [[Port 9100 printing]] or [[Cross-site printing]].

== PRESCRIBE ==

For Kyocera devices, the PRESCRIBE page description languages may be used to reset the device to factory default from within ordinary print jobs using one of the commands shown below: <!-- may autorize first, using default machine passwords: !R! ACNT "ADMN", "5200"; -->

 !R! KSUS "AUIO", "CUSTOM:Admin Password = 'admin00'";  CMMT "Drop the security level, reset password";
 !R! ACNT "REST";                                       CMMT "Reset account code admin password";
 !R! EGRE;                                              CMMT "Reset the engine board to factory defaults";
 !R! SIOP0,"RESET:0";                                   CMMT "Reset configuration settings";

'''How to test for this attack?'''

Open a raw network connection (using ''netcat'' <ref>''[http://nc110.sourceforge.net/ Netcat – TCP/IP Swiss Army Knife]'', Hobbit, 1996</ref>, for example) to port 9100/tcp of the printer and send the commands documented above.

'''Who can perform this attack?'''

Anyone who can print, for example through [[USB drive or cable]], [[Port 9100 printing]] or [[Cross-site printing]].


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