THIS CODE IS OBSOLETE AND WILL NOT EVEN BUILD ANYMORE

This project is a proof-of-concept for secure video playback on ARM Trustzone hardware running Linux and OP-TEE. A linux application relies on OP-TEE and a Trusted Application to decrypt and display an image in a secure way.

The demo runs on Base FVP software models such as FVP_Base_AEMv8A-AEMv8A. Note that the (free) Foundation Platform can not run this demo, because it lacks LCD display emulation. See http://www.arm.com/products/tools/models/fast-models/foundation-model.php for details.

TL;DR

1. Install the required compilers, tools and libraries (I am using Ubuntu 14.04 x86_64 as my development system):

$ sudo apt-get install uuid-dev gcc-arm-linux-gnueabihf
# On x86_64 systems only #
$ sudo apt-get install libc6:i386 libstdc++6:i386 libz1:i386

2. Clone and build the demo:

$ git clone https://github.com/jforissier/secvid_demo.git
$ cd secvid_demo
$ git submodule update --init
$ make

3. Define the FVP environment in run/env.sh. Here is mine:

export [email protected]
export PATH=~/FVP_Base_AEMv8A-AEMv8A/models/Linux64_GCC-4.1:$PATH
#FVP_CMD=FVP_Base_AEMv8A-AEMv8A

4. Run the demo:

$ ./run/run.sh

In the FVP terminal:

modprobe secfb
modprobe optee_armtz
sleep 1
tee-supplicant&
secvideo_demo -h
# -ns: do not make output buffer secure, -r: read data from NS world
# This succeeds: decrypted data can be read from non-secure output buffer
# (0xff's are read which is the white background)
secvideo_demo -ns linaro-logo-web.rgba.aes -r
# Clear screen
secvideo_demo -c
# This fails: image is displayed but NS world can't read from secure
# output buffer (only 0x00's are read)
secvideo_demo linaro-logo-web.rgba.aes -r
# NOTE: BUG: once output buffer is secured it cannot be made non-secure
# unless the FVP is rebooted

More information

The demo performs the following tasks:

• The system is booted.
  • The ARM model loads the 1st level Boot Loader (BL1), which is the ARM Trusted Firmware BL1 binary, as well as the Firmware Image Package (FIP) composed of: ARM TF BL2, ARM TF BL3.1 (secure monitor), BL3.2 (OP-TEE), BL3.3 (UEFI - EDK2).
  • Control is transferred to BL1 which will start system bring-up: BL2, secure monitor initialization, OP-TEE initialization, then UEFI loads and boots the linux kernel.
  • OP-TEE initialization involves the following steps:
    • Reserve memory for the frame buffer and any other buffer required for decryption/decoding and configure the TZC400 address space controller to restrict access to the buffers to secure world and the LCD controller only
    • Initializes the display controller (width, height, frame buffer address, image format...)
  • The kernel mounts the root filesystem and drops to a shell on serial port #0.
  • The OP-TEE linux driver is loaded (modprobe optee_armtz).
  • The dummy "secure framebuffer" is loaded (modprobe secfb). It implements an ioctl() that returns the buffer used by the secure OS as a framebuffer (this is the buffer used when configuring the LCD display controller).
• The normal world TEE daemon is started (tee-supplicant&)
• The secvido_demo application is started. It uses the TEE Client library (libteec.so) to open a session with a trusted application.
  • The TEE Client calls the OP-TEE driver
  • OP-TEE Core instantiates the required trusted application (ffa39702-9ce0-47e0-a1cb-4048cfdb847d.ta): the binary is loaded by tee-supplicant and transfered to secure world through the OP-TEE driver.
• The TA decrypts the image data into secure memory, using the TEE Crypto API.
• The TA decodes/copies the image into the framebuffer for display.

The project has the following directories:

• app
  • app/host: Main Linux application, secvideo_demo
  • app/ta: Trusted side of the application
• arm-trusted-firmware
• downloads: Temporary files downloaded when project is built for the first time (BusyBox sources, compilers)
• edk2: UEFI bootloader
• gen_rootfs: Utilities to build a minimal root filesystem for Linux, based on BusyBox
• linux: The Linux kernel, including the OP-TEE driver
• optee_client: OP-TEE client library
• optee_os: OP-TEE
• run: Contains a script to launch the simulation
• toolchains: GCC cross-compilers for AArch64