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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

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