/Achilles

A checkm8 utility for A7-A11 devices

Primary LanguageCGNU General Public License v3.0GPL-3.0

Achilles

Exploiting the Achilles Heel of the SecureROM.

Time spent on Achilles

What is Achilles?

Achilles is a project that aims to provide a easy way to harness the power of the checkm8 BootROM exploit. It has three prominent features:

  • Exploitation using gaster payloads to patch signature checks
  • Booting PongoOS as a drop-in replacement for checkra1n 1337
  • Jailbreaking rootless with palera1n

This project is nowhere near the maturity of the original versions of these projects, but was only created as a personal project to learn more about the BootROM and iOS bootchain. As such, I am in no way denouncing the above projects, and would in fact recommend using them over Achilles at the moment, as they are much more mature and stable. The project is still much in development, and so I do not recommend using it unless you know what you are doing.

Achilles has support for both IOKit and libusb as a USB backend. To compile with IOKit, ensure you are on a Mac and run make. For libusb, run make libusb. At the moment, macOS is the only supported operating system, but I plan to add support for Linux and Windows in the future - however, I do not have a Windows or Linux machine to test on, so this may take a while. If you want to help with this, please submit a pull request.

Jailbreaking with palera1n is experimental and Achilles does not support certain options that the palera1n program provides support for (such as --force-revert), but so far has worked fine for my device.

Usage

➜  ~ Achilles -h
Usage: Achilles [options]
Options:
	-v, --verbosity: Verbosity level, maximum of 2 (e.g. -vv, --verbosity 2)
	-d, --debug: Enable debug logging
	-h, --help: Show this help message
	-q, --quick: Don't ask for confirmation during the program
	-e, --exploit: Exploit with checkm8 and exit
	-p, --pongo: Boot to PongoOS and exit
	-j, --jailbreak: Jailbreak rootless using palera1n kpf, ramdisk and overlay
	-V, --verbose-boot: Boot device with verbose boot
	-s, --serial: Enable serial output from the device when booting
	-b, --boot-args: Boot arguments to pass to PongoOS
	-k, --override-pongo: Use a custom Pongo.bin file
	-K, --custom-kpf: Use a custom kernel patchfinder file
	-R, --custom-ramdisk: Use a custom ramdisk file
	-O, --custom-overlay: Use a custom overlay file
  • -v, --verbosity VERBOSITY - Sets the verbosity level of the program. This can be set to 0, 1 or 2, with 0 being no verbose output, 1 being verbose output and 2 being verbose output with extra information (function name, file). This can also be set by using -v or -vv instead of --verbosity 1 or --verbosity 2 respectively.
  • -d, --debug - Enables debug logging, which will print out extra information about the program's execution. This is useful if you are editing the code yourself and are trying to debug an issue.
  • -q, --quick - Disables confirmation prompts during the program, such as the prompt to enter recovery mode or to start the exploit.
  • -e, --exploit - Runs the checkm8 exploit and then exits. This is used if you want to use the exploit to patch signature checks on a checkm8 device.
  • -p, --pongo - Boots to the PongoOS environment only.
  • -j, --jailbreak - Boots to the PongoOS environment and then jailbreaks rootless using palera1n.
  • -V, --verbose-boot - Boots the device with verbose boot. This is useful if you want to see the boot logs of the device, but also just looks pretty cool.
  • -s, --serial - Enables serial output from the device when booting. This is useful if you are debugging PongoOS/YoloDFU mode and need extra output, and also enables verbose logs during the boot process.
  • -b, --boot-args BOOT_ARGS - Passes boot arguments to PongoOS. This is useful if you want to boot with a custom boot argument, such as wdt=-1 to disable the watchdog timer.
  • -k, --override-pongo PONGO_PATH - Uses a custom Pongo.bin file instead of the one included in the program.
  • -K, --custom-kpf KPF_PATH - Uses a custom kernel patchfinder file instead of the one included in the program.
  • -R, --custom-ramdisk RAMDISK_PATH - Uses a custom ramdisk file instead of the one included in the program.
  • -O, --custom-overlay OVERLAY_PATH - Uses a custom overlay file instead of the one included in the program.

If compiled with make DEBUG=-DDEBUG, Achilles features two extra arguments:

-o, --custom-overwrite: Use a custom overwrite file
-P, --custom-payload: Use a custom payload file

By using these, you are on your own and I cannot guarantee that the exploit will work as expected, and as such will not offer any support. If you are booting YoloDFU using a custom overwrite and payload, you will need to pass -p as well, so that the program knows not to send certain transfers that will cause the YoloDFU payload to not work. You can see this inside the checkm8SendPayload() function in src/exploit/exploit.c.

Dependencies

The easiest ways to install these dependencies on macOS are as follows:

  • brew install libimobiledevice

  • brew install binutils

  • ln -s /path/to/homebrew/opt/binutils/bin/gobjcopy /usr/local/bin/gobjcopy

You have to symlink gobjcopy to /usr/local/bin as the binutils installation is not symlinked by default (as it can cause conflicts with built-in binaries from Apple).

Supported devices

The regular gaster exploit should support A7-11 as well as T2, and booting PongoOS should work on A8-11 - with that, I have confirmed that the following devices work on my setup (M1 MacBook Air + IOKit):

  • iPhone X (A11) - regular exploit, PongoOS
  • iPad Pro 10.5" (A10X) - regular exploit, PongoOS
  • iPad Pro 12.9" (A10X) - regular exploit, PongoOS
  • iPhone 7 (A10) - regular exploit, PongoOS
  • iPad Pro 9.7" (A9X) - regular exploit, PongoOS
  • iPhone 6 (A8) - regular exploit, PongoOS

SoCs that still need testing are as follows:

  • T2 (Macs) - regular exploit
  • A9 (iPhone 6S (Plus), iPhone SE, iPad 5) - regular exploit, PongoOS
  • A8X (iPad Air 2) - regular exploit, PongoOS
  • A7 (iPhone 5S, iPad Air, iPad Mini 2/3) - regular exploit

If you want to test with your device, please do so and then submit an issue or pull request with your results. Make sure to include information about your host machine (OS version, model, USB backend), device (model, SoC) and iOS version (only necessary if having issues with PongoOS).

If anyone else has successes or failures with other devices, please let me know so I can update this list and/or try to fix any issues you may experience.

What is planned for the future?

At the moment, Achilles can boot PongoOS, and is able to patch signature checks on checkm8 devices using the gaster payloads, but I haven't tested all devices. However, in the future, I plan to gear the project more towards a checkra1n-like experience. This includes booting a pre-boot execution environment (such as PongoOS), and jailbreaking the device. However, the option for regular checkm8 exploitation will always be available.

First of all, I want to write my own jailbreaking tool off of the back of Achilles. This will likely be a developer-oriented rootless jailbreak, as palera1n should suffice for most users. Doing so will involve writing a custom program that performs a similar job to jbinit as well as a loader application and package installation.

As part of the general plan for Achilles in the future, I plan on creating an alternative to PongoOS. While this is a difficult task, and one that I certainly do not have the knowledge to take up at the moment, I hope that I can learn enough to be able to do this in the future. Thanks to the brilliant efforts of the checkra1n team and their open-source PongoOS, I have a great starting point to learn from and hopefully something that can aid me in this complex project.

Furthermore, I am looking to take a shot at SEP exploitation with blackbird, which will allow for downgrades and dualboots on checkm8 devices, as well as bypassing the SEP mitigations seen in recent major iOS versions.

For improvements planned for this project, check the to-do list to see what is in the works and what I plan to work on next.

Known issues

Entering recovery mode programmatically can be rather hit or miss, so if you device continuously fails to enter recovery mode, enter it manually and then run Achilles. This is a known issue and I am working on a fix for it, however the error seems to be related to libimobiledevice, so may be difficult to debug.

There also seems to be an issue with the libusb build of Achilles, when booting PongoOS, where a segmentation fault will occasionally occur when the USB handle is opened again after the device enters download mode. I have not figured out how to deterministically trigger this issue, and as such cannot fix it at this time. As a work-around, use the IOKit build or just simple place the device back into DFU from download mode and run the program again.

Finally, these success rate of the exploit on libusb seems to be lower. The exploit can sometimes fail, and will quite frequently hang while trying to stall the endpoint while spraying the heap. The cause of this is not known, but if you would like to avoid this, use the IOKit build.

Documentation

I have made an effort to document the code as much as possible, and in all header files you will find a description of a function's purpose, parameters and return value for each function exported in the header. Hopefully this can help anyone who wants to learn more about the BootROM and iOS bootchain understand what is going on a bit better.

Furthermore, I have included a detailed writeup on the vulnerabilities exploited in the checkm8 exploit, including the not very well documented memory leak and subsequent exploitation of it. I tried my best to provide definitions where possible and explain the process as clearly as I could in the effort to make it simple for anyone with a basic understanding of vulnerability exploitation to understand. Head over to the docs directory to check out the writeup.

If you find any issues with the documentation, please open an issue or submit a pull request to help improve it.

Disclaimer

Any damage caused to your device is your own responsibility. I am not responsible for any damage caused to your device by using this software, and by using this software you agree to this and are running the acute risk of damaging your device. Please be careful. I have so far not had any issues with my device, but that does not mean that you will not - however, due to the nature of the checkm8 exploit, it is very unlikely that you will damage your device in a way that cannot be fixed by a DFU restore.

Additionally, this project is not affiliated with any other projects listed at the bottom of this page, or in other/licenses - including (but not limited to) checkra1n, palera1n, gaster, ipwndfu, openra1n and ra1npoc. Achilles is a completely seperate project, and any issues encountered with it should be reported in this repository, not the to developers of the credited projects.

Finally, you may find that there are similarities in here to other projects like this - and that is true. This was just a personal project for me to learn more about the BootROM and iOS bootchain. As a result, I relied a lot on open-source solutions such as ipwndfu, gaster and PongoOS to help me along the way. Check the credits section for more information.

Credits

The following projects, people and their open-source work has been instrumental in the development of this project:

All licenses for any code used in this project that is not my own can be found in the other/licenses directory.