On Fri, May 31, 2024 at 03:50:34PM +0200, Caleb Connolly wrote:
As more boards adopt support for the EFI CapsuleUpdate mechanism, there is a growing issue of being able to target updates to them properly. The current mechanism of hardcoding UUIDs for each board at compile time is unsustainable, and maintaining lists of GUIDs is similarly cumbersome.
In this series, I propose that we adopt v5 GUIDs, these are generated by using a well-known salt GUID as well as board specific information (like the model/revision), these are hashed together and the result is truncated to form a new UUID.
Dear Caleb,
Thank you for working on this proposal, this looks very useful. Indeed, we found out during SystemReady certifications that it is easy for unique ids to be inadvertently re-used, making them thus non-unique.
I have a doubt regarding the format of the generated UUIDs, which end up in the ESRT, though.
Here is a quick experiment on the sandbox booting with a DTB using the efidebug command.
With the patch series, rebased on the master branch:
$ make sandbox_defconfig $ make $ ./u-boot --default_fdt ... U-Boot 2024.07-rc4-00028-g1c96225b0b3 (Jun 19 2024 - 15:29:04 +0200) ... Model: sandbox ... Hit any key to stop autoboot: 0 => efidebug capsule esrt ... ======================================== ESRT: fw_resource_count=2 ESRT: fw_resource_count_max=2 ESRT: fw_resource_version=1 [entry 0]============================== ESRT: fw_class=FD5DB83C-12F3-A46B-80A9-E3007C7FF56E ... [entry 1]============================== ESRT: fw_class=935FE837-FAC8-4394-C008-737D8852C60D ... ========================================
$ uuid -d FD5DB83C-12F3-A46B-80A9-E3007C7FF56E encode: STR: fd5db83c-12f3-a46b-80a9-e3007c7ff56e SIV: 336781303264349553179461347850802165102 decode: variant: DCE 1.1, ISO/IEC 11578:1996 version: 10 (unknown) content: FD:5D:B8:3C:12:F3:04:6B:00:A9:E3:00:7C:7F:F5:6E (not decipherable: unknown UUID version)
Version 10 does not look right.
$ uuid -d 935FE837-FAC8-4394-C008-737D8852C60D encode: STR: 935fe837-fac8-4394-c008-737d8852c60d SIV: 195894493536133784175416063449172723213 decode: variant: reserved (Microsoft GUID) version: 4 (random data based) content: 93:5F:E8:37:FA:C8:03:94:00:08:73:7D:88:52:C6:0D (no semantics: random data only)
A reserved Microsoft GUID variant does not look right.
With the master branch, the (hardcoded) GUIDs are ok:
$ ./u-boot --default_fdt ... U-Boot 2024.07-rc4-00021-gfe2ce09a075 (Jun 19 2024 - 15:35:08 +0200) ... Model: sandbox ... => efidebug capsule esrt ... ======================================== ESRT: fw_resource_count=2 ESRT: fw_resource_count_max=2 ESRT: fw_resource_version=1 [entry 0]============================== ESRT: fw_class=09D7CF52-0720-4710-91D1-08469B7FE9C8 ... [entry 1]============================== ESRT: fw_class=5A7021F5-FEF2-48B4-AABA-832E777418C0 ... ========================================
$ uuid -d 09D7CF52-0720-4710-91D1-08469B7FE9C8 encode: STR: 09d7cf52-0720-4710-91d1-08469b7fe9c8 SIV: 13083600744351929150374221048734280136 decode: variant: DCE 1.1, ISO/IEC 11578:1996 version: 4 (random data based) content: 09:D7:CF:52:07:20:07:10:11:D1:08:46:9B:7F:E9:C8 (no semantics: random data only)
$ uuid -d 5A7021F5-FEF2-48B4-AABA-832E777418C0 encode: STR: 5a7021f5-fef2-48b4-aaba-832e777418c0 SIV: 120212745678117161641696128857923655872 decode: variant: DCE 1.1, ISO/IEC 11578:1996 version: 4 (random data based) content: 5A:70:21:F5:FE:F2:08:B4:2A:BA:83:2E:77:74:18:C0 (no semantics: random data only)
Also, this is what to expect for a v5 UUID [1]:
$ uuid -d a8f6ae40-d8a7-58f0-be05-a22f94eca9ec encode: STR: a8f6ae40-d8a7-58f0-be05-a22f94eca9ec SIV: 224591142595989943290477237735758014956 decode: variant: DCE 1.1, ISO/IEC 11578:1996 version: 5 (name based, SHA-1) content: A8:F6:AE:40:D8:A7:08:F0:3E:05:A2:2F:94:EC:A9:EC (not decipherable: truncated SHA-1 message digest only)
Best regards, Vincent.
[1] https://uuid.ramsey.dev/en/stable/rfc4122/version5.html
The well-known salt GUID can be specific to the architecture (SoC vendor), or OEM. It is defined in the board defconfig so that vendors can easily bring their own.
Specifically, the following fields are used to generate a GUID for a particular fw_image:
- namespace salt
- board compatible (usually the first entry in the dt root compatible array).
- fw_image name (the string identifying the specific image, especially relevant for board that can update multiple images).
== Usage ==
Boards can integrate dynamic UUID support as follows:
- Adjust Kconfig to depend on EFI_CAPSULE_DYNAMIC_UUIDS if EFI_HAVE_CAPSULE_SUPPORT.
- Skip setting the fw_images image_type_id property.
- Generate a UUID and set CONFIG_EFI_CAPSULE_NAMESPACE_UUID in your defconfig.
== Limitations ==
- Changing GUIDs
The primary limitation with this approach is that if any of the source fields change, so will the GUID for the board. It is therefore pretty important to ensure that GUID changes are caught during development.
- Supporting multiple boards with a single image
This now requires having an entry with the GUID for every board which might lead to larger UpdateCapsule images.
== Tooling ==
This series introduces a new tool: genguid. This can be used to generate the same GUIDs that the board would at runtime.
This series follows a related discussion started by Ilias: https://lore.kernel.org/u-boot/CAC_iWjJNHa4gMF897MqYZNdbgjFG8K4kwGsTXWuy72Wk...
Changes in v3:
- Add manpage for genguid
- Add dedicated CONFIG_TOOLS_GENGUID option
- Minor code fixes addressing v2 feedback
- Link to v2: https://lore.kernel.org/r/20240529-b4-dynamic-uuid-v2-0-c26f31057bbe@linaro....
Changes in v2:
- Move namespace UUID to be defined in defconfig
- Add tests and tooling
- Only use the first board compatible to generate UUID.
- Link to v1: https://lore.kernel.org/r/20240426-b4-dynamic-uuid-v1-0-e8154e00ec44@linaro....
Caleb Connolly (7): lib: uuid: add UUID v5 support efi: add a helper to generate dynamic UUIDs doc: uefi: document dynamic UUID generation sandbox: switch to dynamic UUIDs lib: uuid: supporting building as part of host tools tools: add genguid tool test: lib/uuid: add unit tests for dynamic UUIDs
arch/Kconfig | 1 + board/sandbox/sandbox.c | 16 --- configs/sandbox_defconfig | 1 + configs/sandbox_flattree_defconfig | 1 + doc/develop/uefi/uefi.rst | 31 +++++ doc/genguid.1 | 52 +++++++ include/sandbox_efi_capsule.h | 6 +- include/uuid.h | 21 ++- lib/Kconfig | 8 ++ lib/efi_loader/Kconfig | 23 +++ lib/efi_loader/efi_capsule.c | 1 + lib/efi_loader/efi_firmware.c | 66 +++++++++ lib/uuid.c | 81 +++++++++-- test/lib/uuid.c | 88 ++++++++++++ .../test_efi_capsule/test_capsule_firmware_fit.py | 2 +- .../test_efi_capsule/test_capsule_firmware_raw.py | 8 +- .../test_capsule_firmware_signed_fit.py | 2 +- .../test_capsule_firmware_signed_raw.py | 4 +- test/py/tests/test_efi_capsule/version.dts | 6 +- tools/Kconfig | 7 + tools/Makefile | 3 + tools/binman/etype/efi_capsule.py | 2 +- tools/binman/ftest.py | 2 +- tools/genguid.c | 154 +++++++++++++++++++++ 24 files changed, 538 insertions(+), 48 deletions(-)
change-id: 20240422-b4-dynamic-uuid-1a5ab1486c27 base-commit: 2e682a4a406fc81ef32e05c28542cc8067f1e15f
// Caleb (they/them)