EFI_UPDATE_CAPSULE is the industry standard method for applying firmware updates. Make it a requirement in EBBR so that fwupd, Windows Update, and any other generic firmware update service can support EBBR platforms.

This is made required because the ability to update firmware is a critical part of building secure platforms.

Fixes: #69 Signed-off-by: Grant Likely grant.likely@arm.com --- source/chapter2-uefi.rst | 32 +++++++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/source/chapter2-uefi.rst b/source/chapter2-uefi.rst index 7b5eb24..b1182a8 100644 --- a/source/chapter2-uefi.rst +++ b/source/chapter2-uefi.rst @@ -167,7 +167,10 @@ are required to be implemented during boot services and runtime services. EFI_SET_VARIABLE Required Optional EFI_GET_NEXT_HIGH_MONO_COUNT N/A Optional EFI_RESET_SYSTEM Required Optional - EFI_UPDATE_CAPSULE Optional Optional + EFI_UPDATE_CAPSULE Required Optional + for in-band + firmware + update EFI_QUERY_CAPSULE_CAPABILITIES Optional Optional EFI_QUERY_VARIABLE_INFO Optional Optional ============================== ============= ================ @@ -243,6 +246,25 @@ Even when SetVariable() is not supported during runtime services, firmware should cache variable names and values in EfiRuntimeServicesData memory so that GetVariable() and GetNextVeriableName() can behave as specified.

+Firmware Update +--------------- + +Being able to update firmware to address security issues is a key feature of secure platforms. +EBBR platforms are required to implement either an in-band or an out-of-band firmware update mechanism. + +If firmware update is performed in-band (firmware on the application processor updates itself), +then the firmware shall implement EFI_UPDATE_CAPSULE and accept updates in the +"Firmware Management Protocol Data Capsule Structure" format as described in [UEFI]_ § 23.3, +"Delivering Capsules Containing Updates to Firmware Management Protocol. [#FMPNote]_ +Firmware is also required to provide an EFI System Resource Table (ESRT). [UEFI]_ § 23.4 +Every firmware image that is updated in-band must be described in the ESRT. + +If firmware update is performed out-of-band (e.g., by an independent Board Management Controller, +or firmware is provided by a hypervisor), then the platform is not required to implement EFI_UPDATE_CAPSULE. + +EFI_UPDATE_CAPSULE is only required before ExitBootServices() is called. + + .. [#OPTEESupplicant] It is worth noting that OP-TEE has a similar problem regarding secure storage. OP-TEE's chosen solution is to rely on an OS supplicant agent to perform @@ -253,3 +275,11 @@ that GetVariable() and GetNextVeriableName() can behave as specified. during runtime services.

https://optee.readthedocs.io/en/latest/architecture/secure_storage.html + +.. [#FMPNote] The `EFI_UPDATE_CAPSULE` implementation is expected to be suitable + for use by generic firmware update services like fwupd and Windows Update. + Both fwupd and Windows Update read the ESRT table to determine what firmware + can be updated, and use an EFI helper application to call `EFI_UPDATE_CAPSULE` + before ExitBootServices() is called. + + https://fwupd.org/ -- 2.20.1

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