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Secure Boot for Tegra

This project contains a set of scripts to automate the secure boot process outlined in the Nvidia L4T Development Guide

The scripts are currently hard-coded to use Jetson AGX Xavier as the target.

The scripts are for the 32.7.1 (Jetpack 4.6.1) release. To change the version, make changes to the downloadfilenames file.

CAUTION: These scripts are only known to be good and run on a bare-metal Ubuntu 18.04 system. A virtual machine or other distribution is not recommended and may lead to unexpected behavior and "brick" your board.

Downloading Packages and preparing for use

Run

./download-and-prepare-files.sh

Flashing stock image (optional)

Put your device in recovery mode, then run

./flashing-and-booting.sh

Verify your device boots successfully

Installing secureboot

Run

./installing-secureboot.sh

To install secureboot

Creating a Private Key

Following the instructions in Generating the RSA Key Pair we will generate a key file, name it rsa_priv.pem and place it in the same directory as the scripts.

Run

./gen-keys.sh

The above script also generated:

  • Secure Boot Key (SBK) sbk_hex_file
  • 256-bit Key Encryption Key (KEK256) kek2256_hex_file
  • 128-bit KEK2 kek2_hex_file
  • 128-bit user_key_hex_file
  • the public key rsa_pub.pem file

You should store these files in a secure location with access limited to only those that need them to sign and encrypt images.

Test (Not Burn) the Fuses

Put the device into Forced Reset mode.

Run

./test-sbkpkc-kek2-kek256.sh 2>&1 | tee test.log

This simulates burning the PKC, SBK, KEK2 and KEK256 fuses on the part. This will generate an odmfuse_pkc.xml file in `Linux_For_Tegra/bootloader``.

Inspect the test.log file for any errors, warnings or unexpected behavior.

Generate Factory Fuse Blob

Run

./gen-factory-sbkpkc-kek2-kek256-odmfuse-file.sh 2>&1 | tee factory.log

This will generate a fuseblob.tbz2 file in Linux_for_Tegra/

Inspect the factory.log for any errors, warnings or unexpected behavior.

Comparing the results

Extract the fuseblob.tbz2 file from above, e.g. into a directory named fuseblob. Compare the fuseblob/odmfuse_pkc.xml file to the Linux_for_Tegra/bootloader/odmfuse_pkc.xml file from the "test" script. Ensure that these files are identical.

If they are different, you probably have something wrong with the "factory" script. For example, if your device is in the unfused state, but you pass --auth SBKPKC to odmfuse.sh it will NOT generate the SBK or PKC lines. This is because the odmfuse.sh script (in off-line mode e.g. --no-flash) does not know the state of the device and makes assumptions based on the arguments passed to odmfuse.sh.

An example (correct) odmfuse_pkc.xml would look like:

<genericfuse MagicId="0x45535546" version="1.0.0">
<fuse name="SecureBootKey" size="16" value="0x94f769b99cb6903309cfda062751216b" />
<fuse name="Kek2" size="16" value="206f34b0fd5072c15e683d5a0e6e3a77" />
<fuse name="Kek256" size="32" value="0a90d71dcdfb5930ebc8e7a6a85ae80eb140b691d0c9e7751f676443d560376f" />
<fuse name="PublicKeyHash" size="32" value="0xed32eb0a8e1cb8de800361a4618a9753051285afa795881d0c9cd6dda6f17ce8" />
<fuse name="BootSecurityInfo" size="4" value="0x6" />
<fuse name="SecurityMode" size="4" value="0x1" />
</genericfuse>

Burning the fuses

NVidia recommends burning all the fuses at once, with the fuseblob.tbz2 generated previously. Assuming you extracted this to fuseblob, you are now ready to burn the fuses.

WARNING: The fuses can only be changed from a "zero" to a "one" once. The following command will permanently change the state of the fuses on your board. If anything was wrong in the prior steps, you might render your board unbootable.

Put the device into Forced Recovery mode.

Run

pushd fuseblob/bootloader
sudo ./fusecmd.sh
popd

Signing SBKPKC image

Run

./signing-sbkpkc.sh

To sign your local images.

Re-flash the device with signed images

Put your device in recovery mode.

Run

./bootloader-flash-signed.sh

To write signed images to the part

Confirm the device booted into the NVidia Ubuntu OS.

Signing and Encrypting images with meta-tegra

You can now create your own images with Secure Boot Support and sign and encrypt them at build time by putting the following in your local.conf, <distro>.conf or a <machine>.conf.

TEGRA_SIGNING_ARGS = "-u /path/to/rsa_priv.pem -v /path/to/sbk_hex_file"

The <image>.tegraflash.tgz can be expanded and installed as normal, but will include encrypted and signed artifacts.