{% hint style="success" %}
Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\
Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[**HackTricks Training GCP Red Team Expert (GRTE)**<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)

<details>

<summary>Support HackTricks</summary>

* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks\_live)**.**
* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.

</details>
{% endhint %}

The following steps are recommended for modifying device startup configurations and bootloaders like U-boot:

1. **Access Bootloader's Interpreter Shell**:
   - During boot, press "0", space, or other identified "magic codes" to access the bootloader's interpreter shell.

2. **Modify Boot Arguments**:
   - Execute the following commands to append '`init=/bin/sh`' to the boot arguments, allowing execution of a shell command:
     %%%
     #printenv
     #setenv bootargs=console=ttyS0,115200 mem=63M root=/dev/mtdblock3 mtdparts=sflash:<partitiionInfo> rootfstype=<fstype> hasEeprom=0 5srst=0 init=/bin/sh
     #saveenv
     #boot
     %%%

3. **Setup TFTP Server**:
   - Configure a TFTP server to load images over a local network:
     %%%
     #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 network access
     #tftp ${loadaddr} uImage-3.6.35 #loadaddr takes the address to load the file into and the filename of the image on the TFTP server
     %%%

4. **Utilize `ubootwrite.py`**:
   - Use `ubootwrite.py` to write the U-boot image and push a modified firmware to gain root access.

5. **Check Debug Features**:
   - Verify if debug features like verbose logging, loading arbitrary kernels, or booting from untrusted sources are enabled.

6. **Cautionary Hardware Interference**:
   - Be cautious when connecting one pin to ground and interacting with SPI or NAND flash chips during the device boot-up sequence, particularly before the kernel decompresses. Consult the NAND flash chip's datasheet before shorting pins.

7. **Configure Rogue DHCP Server**:
   - Set up a rogue DHCP server with malicious parameters for a device to ingest during a PXE boot. Utilize tools like Metasploit's (MSF) DHCP auxiliary server. Modify the 'FILENAME' parameter with command injection commands such as `'a";/bin/sh;#'` to test input validation for device startup procedures.

**Note**: The steps involving physical interaction with device pins (*marked with asterisks) should be approached with extreme caution to avoid damaging the device.


## References
* [https://scriptingxss.gitbook.io/firmware-security-testing-methodology/](https://scriptingxss.gitbook.io/firmware-security-testing-methodology/)


{% hint style="success" %}
Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\
Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[**HackTricks Training GCP Red Team Expert (GRTE)**<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)

<details>

<summary>Support HackTricks</summary>

* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks\_live)**.**
* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.

</details>
{% endhint %}