[RFC] add support for secure partition (SPM-like) #3973

apalos · 2020-07-15T20:38:07Z

Secure variable storage for EFI variables is critical for enabling and
protecting UEFI Secure Boot. Unfortunately due to the fact that SPD and
SPM are mutually exclusive, we can't run StMM from EDK2 and OP-TEE.
An advantage of doing so is that different firmware implementations
can leverage EDK2's StandAloneMM and in cooperation with OP-TEE RPMB
APIs can store UEFI variables in a secure storage.
This makes the variable storage quite generic in any device with an RPMB
partition.

Using a well debugged application is preferable over rewriting the whole
application as a TA. Another advantage is that this inherits the Fault
Tolerant Writes (FTW) functionality built-in on StMM to protect
variables against corruptions during writing. Considering the FFA
changes of the future Arm architectures using an SP that includes
everything seems like a better choice at the moment.
The 'SPM emulation' currently added into OP-TEE only supports
a single SP to be launched. This means that the StMM embedded
application has the RPMB driver built in at the moment. In the future we
can add code (evolving FFA) to launch multiple SPs. So the StMM variable
handling can be decoupled from the RPMB driver, which will reside in a
different SP.

So let's add a user mode secure partition context and support loading
"Standalone MM" of EDK2 into it. A separate syscall handling is added to
serve as different kind of ABI and syscall IDs. The secure partition has
a TA like interface towards normal world, but requests are routed into
the StMM partition instead.

CFG_STMM_PATH is assigned the path of BL32_AP_MM.fd, for instance:
CFG_STMM_PATH=...Build/QemuVirtMmStandalone/DEBUG_GCC5/FV/BL32_AP_MM.fd

Since this is quite tricky to compile and test you can use this [1].
Just clone the repo and run ./build.sh. The script will pick up edk2,
edk2-platforms, op-tee, atf and U-boot and compile all the necessary
binaries for QEMU. A patch (awful hack) has been added to U-boot to
allow RPMB emulation through it's supplicant, since QEMU RPMB emulation
is not yet available.
After compiling and launching QEMU the usual U-boot commands for EFI
variable management will store the variables on an RPMB device.

[1] https://git.linaro.org/people/ilias.apalodimas/efi_optee_variables.git/

Changes Since RFC:

Addressed @jenswi-linaro comments
Moved I/EMSG to DMSG
Removed pointless register restoring
Restoring x0-x7 in return_helper() (needed for FFA)
cherry picked FFA changes, so those are not included in the current patchset
Using mobj_inc_map() to map memory instead of the custom function
Added sp_svc_get_mem_attr() to get a page attributes properly (instead of assuming RWX we did in the RFC).
Also added vm_get_attrs() helper function.
Removed the weird masking flags used in sp_svc_set_mem_attr(). This was a result of using hardcoded (RWX flags for reading the current pages attributes)
Moved comment to /* .... */ format
Used return_helper() when appropriate, instead of manually defining the error flags
Masked x3-x7, with 0xffffffff when used for FFA

Changes since v1:

renamed vm_get_attrs() -> vm_get_prot() and masked the output. This was also placed on a separate commit.
Don't mask x3-x7 with 0xffffffff as it's not needed
Initialized all stack variables
removed stale thread_[g|s]et_cntkctl_el1 functions
Fixed a bug on unti16_t shifting
Added a shippable build target
removed reduntant checks before reading/writing a file

core/arch/arm/include/ffa.h

core/arch/arm/kernel/secure_partition.c

core/arch/arm/include/kernel/secure_partition.h

core/arch/arm/kernel/secure_partition.c

core/arch/arm/kernel/thread_a64.S

core/arch/arm/kernel/thread_private.h

core/arch/arm/mm/tee_mmu.c

jenswi-linaro · 2020-07-21T10:26:05Z

We should probably have Shippable target for StMM in .shippable.yml to make sure that the code always compiles.
It should be OK to piggyback on the first PLATFORM=vexpress-qemu_armv8a target.

apalos · 2020-07-21T13:22:36Z

We should probably have Shippable target for StMM in .shippable.yml to make sure that the code always compiles.
It should be OK to piggyback on the first PLATFORM=vexpress-qemu_armv8a target.

Sure. What about the included binary? As you know the EDK2 code is not merged yet, so any suggestions for CFG_STMM_PATH? Touch a dummy file and use that?

jenswi-linaro · 2020-07-21T13:35:12Z

Yeah, creating a dummy file on the fly should be OK. You could try to make that file the typical size of the StMM binary so we catch eventual overflows in the binary.

core/arch/arm/kernel/secure_partition.c

core/arch/arm/include/pta_stmm.h

core/arch/arm/kernel/secure_partition.c

core/include/mm/tee_mmu.h

.shippable.yml

core/arch/arm/mm/tee_mmu.c

core/arch/arm/include/kernel/secure_partition.h

jenswi-linaro · 2020-07-23T14:18:09Z

Please fix the shippable error.

jenswi-linaro · 2020-07-23T15:23:03Z

Feel free to squash and fixup the commits. Should hopefully take care the travis errors, except the ones about extern which we'll have to accept.

jenswi-linaro · 2020-08-10T08:26:41Z

Reviewed-by: Jens Wiklander <[email protected]>
Please rebase while applying the tag.

core/arch/arm/kernel/secure_partition.c

jenswi-linaro · 2020-08-14T08:56:25Z

Looks good, please squash and rebase.

core/arch/arm/include/kernel/secure_partition.h

core/arch/arm/kernel/secure_partition.c

core/arch/arm/include/kernel/secure_partition.h

core/arch/arm/kernel/secure_partition.c

jenswi-linaro · 2020-08-20T09:02:20Z

Looks good

etienne-lms

Acked-by: Etienne Carriere <[email protected]> with the 2 "coding style to address:" comments addressed. Other comments are free to consider or not...

core/include/kernel/user_mode_ctx.h

core/arch/arm/kernel/secure_partition.c

jenswi-linaro · 2020-08-27T07:03:41Z

For commit "shippable: build secure partition code":
Acked-by: Jens Wiklander <[email protected]>

If all comments are addressed perhaps you can fix up the commits and we should be good to merge.

.shippable.yml

jforissier · 2020-08-31T12:55:14Z

For "shippable: build secure partition code":

Acked-by: Jerome Forissier <[email protected]>

apalos · 2020-09-07T05:55:38Z

@jforissier anything missing to merge this?

jforissier · 2020-09-07T06:27:37Z

@apalos yes, the Acked-by tags, please.

apalos · 2020-09-07T06:32:39Z

@apalos yes, the Acked-by tags, please.

@jforissier fixed!

jforissier · 2020-09-07T06:44:40Z

Etienne's ack is missing on the first and last commits, I think they are applicable (the commits existed when he posted them, and the commits did not evolve substentialy afterwards).

apalos · 2020-09-07T06:51:37Z

Etienne's ack is missing on the first and last commits, I think they are applicable (the commits existed when he posted them, and the commits did not evolve substentialy afterwards).

He only commented on commit patch no. 2, I can add his acked-by tag on the rest if that was what he meant

jforissier · 2020-09-07T06:58:14Z

When someone gives an ack without citing specific commits, it means all of them.

A following commit, related to the StMM functionality needs to read the current page attributes before modifying them. So let's add a function to retrieve the current attributes. Signed-off-by: Ilias Apalodimas <[email protected]> Reviewed-by: Jens Wiklander <[email protected]> Acked-by: Etienne Carriere <[email protected]>

Secure variable storage for EFI variables is critical for enabling and protecting UEFI Secure Boot. Unfortunately due to the fact that SPD and SPM are mutually exclusive, we can't run StMM from EDK2 and OP-TEE. An advantage of doing so is that different firmware implementations can leverage EDK2's StandAloneMM and in cooperation with OP-TEE RPMB APIs can store UEFI variables in a secure storage. This makes the variable storage quite generic in any device with an RPMB partition. Using a well debugged application is preferable over rewriting the whole application as a TA. Another advantage is that this inherits the Fault Tolerant Writes (FTW) functionality built-in on StMM to protect variables against corruptions during writing. Considering the FFA changes of the future Arm architectures using an SP that includes everything seems like a better choice at the moment. The 'SPM emulation' currently added into OP-TEE only supports a single SP to be launched. This means that the StMM embedded application has the RPMB driver built in at the moment. In the future we can add code (evolving FFA) to launch multiple SPs. So the StMM variable handling can be decoupled from the RPMB driver, which will reside in a different SP. So let's add a user mode secure partition context and support loading "Standalone MM" of EDK2 into it. A separate syscall handling is added to serve as different kind of ABI and syscall IDs. The secure partition has a TA like interface towards normal world, but requests are routed into the StMM partition instead. CFG_STMM_PATH is assigned the path of BL32_AP_MM.fd, for instance: CFG_STMM_PATH=...Build/QemuVirtMmStandalone/DEBUG_GCC5/FV/BL32_AP_MM.fd Since this is quite tricky to compile and test you can use this [1]. Just clone the repo and run ./build.sh. The script will pick up edk2, edk2-platforms, op-tee, atf and U-boot and compile all the necessary binaries for QEMU. A patch (awful hack) has been added to U-boot to allow RPMB emulation through it's supplicant, since QEMU RPMB emulation is not yet available. After compiling and launching QEMU the usual U-boot commands for EFI variable management will store the variables on an RPMB device. [1] https://git.linaro.org/people/ilias.apalodimas/efi_optee_variables.git/ Signed-off-by: Jens Wiklander <[email protected]> Co-developed-by: Ilias Apalodimas <[email protected]> Signed-off-by: Ilias Apalodimas <[email protected]> Co-developed-by: Pipat Methavanitpong <[email protected]> Signed-off-by: Pipat Methavanitpong <[email protected]> Co-developed-by: Miklos Balint <[email protected]> Signed-off-by: Miklos Balint <[email protected]> Reviewed-by: Jens Wiklander <[email protected]> Acked-by: Etienne Carriere <[email protected]>

A previous commit adds support for secure partition loading, acting similarly to SPM in order to launch StandAloneMM. Let's add this to shippable and make sure the new code at least compiles properly. Signed-off-by: Ilias Apalodimas <[email protected]> Acked-by: Jerome Forissier <[email protected]> Acked-by: Jens Wiklander <[email protected]> Acked-by: Etienne Carriere <[email protected]>

apalos · 2020-09-07T07:04:21Z

No problem, added the missing ACKs

jforissier · 2020-09-07T08:01:56Z

Thanks @apalos.

With some recent changes in OP-TEE [1] and U-Boot [2] we can compile StMM and launch it from an OP-TEE secure partition which is mimicking SPM. There's a number of advantages in this approach. In Arm world SPM, currently used for dispatching StMM, and SPD used for OP-TEE, are mutually exclusive. Since there's no application in OP-TEE for managing EFI variables, this means that one can have a secure OS or secure variable storage. By re-using StMM we have EDK2s approved application controlling variable storage and the ability to run a secure world OS. This also allows various firmware implementations to adopt EDK2 way of storing variables (including the FTW implementation), as long as OP-TEE is available on that given platform (or any other secure OS that can launch StMM and has a supplicant for handling the RPMB partition). Another advantage is that OP-TEE has the ability to access an eMMC RPMB partition to store those variables. This requires a normal world supplicant, which is implemented in U-Boot currently. The supplicant picks up the encrypted buffer from OP-TEE and wires it to the eMMC driver(s). Similar functionality can be added in EDK2 by porting the supplicant and adapt it to using the native eMMC drivers. There's is one drawback in using OP-TEE. The current SPM calls need to run to completion. This contradicts the current OP-TEE RPC call requirements, used to access the RPMB storage. Thats leads to two different SMC calls for entering secure world to access StMM. So let's add support for a platform that compiles StMM and an RPMB driver that communicates with OP-TEE to read/write the variables. For anyone interested in testing this there's repo that builds all the sources and works on QEMU [3]. [1] OP-TEE/optee_os#3973 [2] http://u-boot.10912.n7.nabble.com/PATCH-0-7-v4-EFI-variable-support-via-OP-TEE-td412499.html [3] https://git.linaro.org/people/ilias.apalodimas/efi_optee_variables.git/ Signed-off-by: Ilias Apalodimas <[email protected]>

With some recent changes in OP-TEE [1] and U-Boot [2] we can compile StMM and launch it from an OP-TEE secure partition which is mimicking SPM. There's a number of advantages in this approach. In Arm world SPM, currently used for dispatching StMM, and SPD used for OP-TEE, are mutually exclusive. Since there's no application in OP-TEE for managing EFI variables, this means that one can have a secure OS or secure variable storage. By re-using StMM we have EDK2s approved application controlling variable storage and the ability to run a secure world OS. This also allows various firmware implementations to adopt EDK2 way of storing variables (including the FTW implementation), as long as OP-TEE is available on that given platform (or any other secure OS that can launch StMM and has a supplicant for handling the RPMB partition). Another advantage is that OP-TEE has the ability to access an eMMC RPMB partition to store those variables. This requires a normal world supplicant, which is implemented in U-Boot currently. The supplicant picks up the encrypted buffer from OP-TEE and wires it to the eMMC driver(s). Similar functionality can be added in EDK2 by porting the supplicant and adapt it to using the native eMMC drivers. There's is one drawback in using OP-TEE. The current SPM calls need to run to completion. This contradicts the current OP-TEE RPC call requirements, used to access the RPMB storage. Thats leads to two different SMC calls for entering secure world to access StMM. So let's add support for a platform that compiles StMM and an RPMB driver that communicates with OP-TEE to read/write the variables. For anyone interested in testing this there's repo that builds all the sources and works on QEMU [3]. [1] OP-TEE/optee_os#3973 [2] http://u-boot.10912.n7.nabble.com/PATCH-0-7-v4-EFI-variable-support-via-OP-TEE-td412499.html [3] https://git.linaro.org/people/ilias.apalodimas/efi_optee_variables.git/ Reviewed-by: Sami Mujawar <[email protected]> Signed-off-by: Ilias Apalodimas <[email protected]>

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super119 mentioned this pull request Jul 6, 2021

OP-TEE 3.13: Is CFG_STMM_PATH still working? #4726

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[RFC] add support for secure partition (SPM-like) #3973

[RFC] add support for secure partition (SPM-like) #3973

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[RFC] add support for secure partition (SPM-like) #3973

[RFC] add support for secure partition (SPM-like) #3973

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