Heads: the other side of TAILS

Heads is a configuration for laptops and servers that tries to bring more security to commodity hardware. Among its goals are:

• Use free software on the boot path
• Move the root of trust into hardware (or at least the ROM bootblock)
• Measure and attest to the state of the firmware
• Measure and verify all filesystems

NOTE: It is a work in progress and not yet ready for non-technical users. If you're interested in contributing, please get in touch. Installation requires disassembly of your laptop or server, external SPI flash programmers, possible risk of destruction and significant frustration.

More information is available in the 33C3 presentation of building "Slightly more secure systems".

Documentation

Please refer to Heads-wiki for your Heads' documentation needs.

Building heads

In order to build reproducible firmware images, Heads builds a specific version of gcc and uses it to compile the Linux kernel and various tools that go into the initrd. Unfortunately this means the first step is a little slow since it will clone the musl-cross tree and build gcc...

Once that is done, the top level Makefile will handle most of the remaining details -- it downloads the various packages, verifies the hashes, applies Heads specific patches, configures and builds them with the cross compiler, and then copies the necessary parts into the initrd directory.

There are still dependencies on the build system's coreutils in /bin and /usr/bin/, but any problems should be detectable if you end up with a different hash than the official builds.

The various components that are downloaded are in the ./modules directory and include:

• musl-libc
• busybox
• kexec
• mbedtls
• tpmtotp
• coreboot
• cryptsetup
• lvm2
• gnupg
• Linux kernel
• Xen hypervisor

We also recommend installing Qubes OS, although there Heads can kexec into any Linux or multiboot kernel.

Notes:

• Building coreboot's cross compilers can take a while. Luckily this is only done once.
• Builds are finally reproducible! The reproduciblebuilds tag tracks any regressions.
• Currently only tested in QEMU, the Thinkpad x230 and the Chell Chromebook. ** Xen and the TPM do not work in QEMU, so it is only for testing the initrd image.
• Building for the Lenovo X220 requires binary blobs to be placed in the blobs/x220/ folder. See the readme.md file in that folder
• Building for the Librem 13 v2/v3 or Librem 15 v3/v4 requires binary blobs to be placed in the blobs/librem_skl folder. See the readme.md file in that folder

coreboot console messages

The coreboot console messages are stored in the CBMEM region and can be read by the Linux payload with the cbmem --console | less command. There is lots of interesting data about the state of the system.