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Howto Enable TPM Support on a Raspberry PI (0, 0W, 1, 2, 3, 3b+) and make it work with the LetsTrust TPM

UPDATE: Works for Pi 3b+, too!

Due to the recent inclusion of the TPM_TIS_SPI patches to the mainline kernel
and the consequent backports to v4.9.x and 4.11.x it's now much easier to get
the support for the LetsTrust TPM up and running.
No more patching necessary!

tldr: Enable CONFIG_TCG_TIS_SPI in your Kernel Config, and modify your
device tree accordingly.

This tutorial will show you how to perform these steps for your Raspberry PI
(0, 0W, 1, 2, 3).

It is assumed that you are cross-compiling from your desktop PC (i.e. not
building the kernel on the raspberry itself) and create everything in your home directory (~).

For more details please also read the excellent guide from the Raspberry Pi
Foundation on howto compile your kernel.

On a Ubuntu system you should install the following packages

First download the toolchain you need for cross compilation
$ git clone
and add the tools to your executable search path
$ export PATH=$PATH:~/tools

Then grab the kernel sources
$ git clone --depth=1
and enter the directory
$ cd linux

Next step is to get the default kernel configuration:

For Pi 1, Pi 0, Pi 0 W, or Compute Module:
$ KERNEL=kernel
$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- bcmrpi_defconfig

For Pi 2, Pi 3, or Compute Module 3:
$ KERNEL=kernel7
$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- bcm2709_defconfig

Then we have to enable the TPM Support in the Kernel via make menuconfig
$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- menuconfig
In this gui navigate to
Device Drivers
---> Character devices
---> TPM Hardware Support

and press M (for Module) or Y (for build-in support)
Then press enter to get into the subdirectory and select
---> TPM Interface Specification 1.3 Interface / TPM 2.0 FIFO Interface - (SPI)
also again either via M or Y

If you want to use the TPM's HardwareNumberGenerator feature, please select
---> Hardware Random Number Generator Core support
---> TPM HW Random Number Generator support

Save and exit the menuconfig.

If this is too much hassle for you, you can also edit your .config file and
add these 5 lines to it.

Next step is to add our DeviceTree Overlay to our kernel sources.
Simply download letstrust-tpm-overlay.dts and copy it to arch/arm/boot/dts/overlays/letstrust-tpm-overlay.dts
$ wget -O arch/arm/boot/dts/overlays/letstrust-tpm-overlay.dts

Now build your kernel and device tree blob
$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- zImage modules dtbs overlays/letstrust-tpm.dtbo -j8
please note the additional overlays/letstrust-tpm.dtbo

Now deploy your kernel and modules (standard rpi way, see howto above)
$ mkdir mnt/fat32
$ mkdir mnt/ext4
$ sudo mount /dev/sdb1 mnt/fat32
$ sudo mount /dev/sdb2 mnt/ext4
$ sudo make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- INSTALL_MOD_PATH=mnt/ext4 modules_install
$ sudo cp mnt/fat32/$KERNEL.img mnt/fat32/$KERNEL-backup.img
$ sudo cp arch/arm/boot/zImage mnt/fat32/$KERNEL.img
$ sudo cp arch/arm/boot/dts/*.dtb mnt/fat32/
$ sudo cp arch/arm/boot/dts/overlays/*.dtb* mnt/fat32/overlays/
$ sudo cp arch/arm/boot/dts/overlays/README mnt/fat32/overlays/

Before you unmount your RPI SD Card, open mnt/fat32/config.txt
and ensure the line dtparam=spi=on isn't commented out (so no # at the beginning of the line)
and add
just beneath it.

More Details:
Of course we uploaded a reference config.txt for you

Unmount your SD card,
$ sudo umount mnt/fat32
$ sudo umount mnt/ext4

Put it into your PI and boot your raspberry pi.

After booting, on a shell do
sudo modprobe tpm_tis_spi and /dev/tpm0 should be visible.
(We are looking into it why it does not autoload)

You can tryout the functionality of your TPM with

Happy Hacking

p.s.: If you just want to try it out without compiling:
Download boot-v4.9.33.tpm.tar.bz2 (kernel, dtb, overlays) + modules-v4.9.33.tpm.tar.bz2

Extract the boot-v4.9.33.tpm.tar.bz2 into the boot partition of your rpi (e.g. sdb1) and the modules-v4.9.33.tpm.tar.bz2 into the second partition.(e.g. sdb2)

$ wget -O /tmp/boot-v4.9.33.tpm.tar.bz2
$ wget -O /tmp/modules-v4.9.33.tpm.tar.bz2
$ sudo mount /dev/sdb1 mnt/fat32
$ sudo mount /dev/sdb2 mnt/ext4
$ cd mnt/fat32
$ sudo tar -xvf /tmp/boot-v4.9.33.tpm.tar.bz2
$ cd ../ext4
$ sudo tar -xvf /tmp/modules-v4.9.33.tpm.tar.bz2
$ cd ..
$ sudo umount /dev/sdb1
$ sudo umount /dev/sdb2

Categories: TPM

was lange währt wird endlich gut.

Neues Plug&Play Image und diesmal: Eines für alle RaspberryPi´s!

Es handelt sich hierbei um ein frisches "Jessie" Image vom 21.06.2017 mit dem Kernel 4.9.33.
Der Pinguin hat freundlicherweise ein ungestartetes Jessie wie in diesem Post beschrieben modifiziert.

Lade dir das Image herunter.
Entpacke es und spiele das Image auf eine SD-Karte.
(Hierbei wird alles auf der SD-Karte vernichtet!)

Einfacher gehts nun fast nicht mehr.

Ist das LetsTrust-TPM an der richtigen Stelle und vor dem Booten gesteckt solltest du mit:
ls /dev/tpm0
dich vergewissern, dass das TPM erkannt wurde.

Nun zum ersten Kommando zum TPM
Im home Verzeichnis findet ihr im Ordner "TPM-Tools" das eltt2.

Öffnet ein Terminal:
cd /TPM-Tools/eltt2/
sudo ./eltt2 -G 20

Ihr habt nun 20 Byte Zufallszahlen vom LetsTrust-TPM erhalten!

Bis bald!