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This directory contains a reference implementation for Chrome OS
verified boot in firmware.
Directory Structure
include/ - Contains all the code headers. firmware_image.h and
kernel_image.h contains the structures that represent a verified boot
firmware and kernel image. Note that the
crypto/ - Contains the implementation for the crypto library. This
includes implementations for SHA1, SHA256, SHA512, and RSA signature
verification (for PKCS #1 v1.5 signatures).
common/ - Contains some utility functions and stub implementations for
certain wrapper functions used in the verification code. Some of these
(for example Free(), Malloc()) will need to be replaced with
appropriate firmware-land equivalent.
utils/ - This contains the implementation of kernel and firmware image
verification (see firmware_image.c and kernel_image.c) and some
utilities (e.g. firmware_utility - for generating verified boot
firmware images).
tests/ - User-land tests and benchmarks that test the reference
implementation. Please have a look at these if you'd like to
understand how to use the reference implementation.
Some useful utilities:
firmware_utility.c To generate verified boot firmware images.
dumpRSAPublicKey.c Dump RSA Public key (from a DER-encoded X509
certificate) in a format suitable for
use by RSAVerify* functions in
verify_data.c Verify a given signature on a given file.
Here's what is required for a minimal verified boot implementation
1) Crypto implementation from crypto/. The verified boot code should
use the wrappers from rsa_utility.h and sha_utility.h - RSAVerify_f()
and Digest*() functions.
2) Verified Firmware and Kernel image verification functions - only
functions that work on binary blobs (VerifyFirmware() and
VerifyKernel()) are required. The functions that work on Firmware and
Kernel images (e.g. VerifyFirmwareImage()) are only useful for
user-land utilities that manipulate signed firmware and kernel images.