This TamaGo based unikernel acts as a primary boot loader for the USB armory Mk II, allowing boot of kernel images (e.g. Linux) from either the eMMC card or an external microSD card.
This repository also provides a command line utility to load imx executables through USB using SDP.
Build the TamaGo compiler (or use the latest binary release):
wget https://github.com/usbarmory/tamago-go/archive/refs/tags/latest.zip
unzip latest.zip
cd tamago-go-latest/src && ./all.bash
cd ../bin && export TAMAGO=`pwd`/go
The BOOT environment variable must be set to either uSD or eMMC to
configure the bootloader media for /boot/armory-boot.conf, as well as kernel
images, location.
The START environment variable must be set to the offset of the first valid
ext4 partition where /boot/armory-boot.conf is located (typically 5242880 for
USB armory Mk II default pre-compiled images).
The CONSOLE environment variable may be set to on to enable serial
logging when a debug accessory
is connected.
Build the armory-boot.imx application executable:
git clone https://github.com/usbarmory/armory-boot && cd armory-boot
make imx BOOT=uSD START=5242880
For convenience a docker configuration is provided.
Ensure docker daemon is running and build the armory-boot docker image,
this needs to be done only the first time:
docker build --build-arg UID=$UID --build-arg GID=$UID -t armory-boot docker
You can enter to the container as follows:
docker run -it --rm -v $PWD:/build armory-boot
The armory-boot.imx file can be flashed on the internal eMMC card or an
external micro SD card as shown in these instructions.
The bootloader expects a single configuration file to read information on the image and parameters to boot.
The bootloader is configured via a single configuration file, and can boot either an ARM kernel image or an ELF unikernel (e.g. tamago-example). The required elements in the configuration file differ depending on the type of image being loaded, examples for both are given below.
It is an error specify both unikernel and kernel config parameters in the same configuration file.
To load a Linux kernel, the bootloader requires that you provide the paths to the kernel image and the Device Tree Blob file, along with their respective SHA256 hashes (only used with configuration signature verification, see Secure Boot), as well as the kernel command line.
An optional initial ramdisk can be passed with the initrd parameter.
Example /boot/armory-boot.conf configuration file for loading a Linux kernel:
{
"kernel": [
"/boot/zImage-5.4.51-0-usbarmory",
"aceb3514d5ba6ac591a7d5f2cad680e83a9f848d19763563da8024f003e927c7"
],
"dtb": [
"/boot/imx6ulz-usbarmory-default-5.4.51-0.dtb",
"60d4fe465ef60042293f5723bf4a001d8e75f26e517af2b55e6efaef9c0db1f6"
],
"initrd": [
"/boot/initrd.img-5.4.51-0-usbarmory",
"64119096fd329e89f062cb5e0fc5b8e66f98081aef987e0bc7a92a05f4452540"
],
"cmdline": "console=ttymxc1,115200 root=/dev/mmcblk0p1 rootwait rw"
}
To load a TamaGo unikernel, the bootloader only needs the path to the ELF binary along with its SHA256 hash (only used with configuration signature verification, see Secure Boot).
Example /boot/armory-boot.conf configuration file for loading a TamaGo
unikernel:
{
"unikernel": [
"/boot/tamago-example",
"e6de9214249dd7989b4056372424e84b273ff4e5d2410fa12ac230ddaf22690a"
]
}
On secure booted systems the imx_signed target should be used instead with the relevant
HAB_KEYS set.
Additionally, to maintain the chain of trust, the PUBLIC_KEY environment
variable must be set with either a signify
or minisign public key to enable
configuration file signature verification.
Example key generation (signify):
signify -G -p armory-boot.pub -s armory-boot.sec
Example key generation (minisign):
minisign -G -p armory-boot.pub -s armory-boot.sec
Compilation with embedded key:
make imx_signed BOOT=uSD START=5242880 PUBLIC_KEY=<last line of armory-boot.pub> HAB_KEYS=<path>
When armory-boot is compiled with the PUBLIC_KEY variable, a signature for
the configuration file must be created in /boot/armory-boot.conf.sig using
with the corresponding secret key.
Example signature generation (signify):
signify -S -s armory-boot.sec -m armory-boot.conf -x armory-boot.conf.sig
Example signature generation (minisign):
minisign -S -s armory-boot.sec -m armory-boot.conf -x armory-boot.conf.sig
The USB armory Mk II LEDs are used, in sequence, as follows:
| Boot sequence | Blue | White |
|---|---|---|
| 0. initialization | off | off |
| 1. boot media detected | on | off |
| 2. kernel verification complete | on | on |
| 3. jumping to kernel image | off | off |
The armory-boot-usb command line utility allows to load an imx executable
through USB using SDP,
useful for testing or initial provisioning purposes.
You can automatically download, compile and install the utility, under your GOPATH, as follows:
go install github.com/usbarmory/armory-boot/cmd/armory-boot-usb@latest
Alternatively you can manually compile it from source:
git clone https://github.com/usbarmory/armory-boot
cd armory-boot && make armory-boot-usb
The utility can be cross compiled for Windows as follows:
make armory-boot-usb.exe
Pre-compiled binaries for Linux and Windows are released here.
The utility is meant to be used on devices running in USB SDP mode:
sudo armory-boot-usb -i armory-boot.imx
found device 15a2:0080 Freescale SemiConductor Inc SE Blank 6ULL
parsing armory-boot.imx
loading DCD at 0x00910000 (952 bytes)
loading imx to 0x9000f400 (2182144 bytes)
jumping to 0x9000f400
serial download complete
Andrea Barisani
andrea.barisani@withsecure.com | andrea@inversepath.com
armory-boot | https://github.com/usbarmory/armory-boot
Copyright (c) WithSecure Corporation
These source files are distributed under the BSD-style license found in the LICENSE file.