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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
* 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.
- Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
- **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/hacktricks_live)**.**
- **Share your hacking tricks by submitting PRs to the [hacktricks repo](https://github.com/carlospolop/hacktricks) and [hacktricks-cloud repo](https://github.com/carlospolop/hacktricks-cloud)**.
