1abb32c623
To do this mount all ESP partitions and check all the binaries there to see if they match any entries in the new dbx. If we applied the update when a hash matched, we would unintentially 'brick' the users machine, as the grub and shim binaries *have* to be updated first. This functionality does reimplement the PE hashing functionality found in sbsigntools and pesign. This was done for 4 main reasons: * There were some memory safety issues found when fuzzing random binaries * Executing the tools hundreds of times was a lot of overhead * Operating from a blob of immutable mmap'd memory is much faster * We only need a very small amount of functionality from both tools |
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|---|---|---|
| .. | ||
| fuzzing | ||
| tests | ||
| create-fuzzing-targets.py | ||
| fu-dbxtool.c | ||
| fu-efi-image.c | ||
| fu-efi-image.h | ||
| fu-efi-signature-common.c | ||
| fu-efi-signature-common.h | ||
| fu-efi-signature-list.c | ||
| fu-efi-signature-list.h | ||
| fu-efi-signature-parser.c | ||
| fu-efi-signature-parser.h | ||
| fu-efi-signature.c | ||
| fu-efi-signature.h | ||
| fu-fuzzer.c | ||
| fu-plugin-uefi-dbx.c | ||
| fu-self-test.c | ||
| fu-uefi-dbx-common.c | ||
| fu-uefi-dbx-common.h | ||
| fu-uefi-dbx-device.c | ||
| fu-uefi-dbx-device.h | ||
| meson.build | ||
| README.md | ||
UEFI dbx Support
Introduction
Updating the UEFI revocation database prevents starting EFI binaries with known security issues, and is typically no longer done from a firmware update due to the risk of the machine being "bricked" if the bootloader is not updated first.
This plugin also checks if the UEFI dbx contains all the most recent revoked checksums. The result will be stored in an security attribute for HSI.
Firmware Format
The daemon will decompress the cabinet archive and extract a firmware blob in EFI_SIGNATURE_LIST format.
See https://www.uefi.org/sites/default/files/resources/UEFI%20Spec%202_6.pdf for details.
This plugin supports the following protocol ID:
- org.uefi.dbx
GUID Generation
These devices use the GUID constructed of the uppercase SHA256 of the X509 certificates found in the system KEK and optionally the EFI architecture. e.g.
UEFI\CRT_{sha256}UEFI\CRT_{sha256}&ARCH_{arch}
...where arch is typically one of IA32, X64, ARM or AA64
Vendor ID Security
The vendor ID is hardcoded to UEFI:Microsoft for all devices.