Messages in this thread | | | Date | Tue, 22 Aug 2023 11:59:37 -0700 (PDT) | From | Shyam Saini <> | Subject | Re: [RFC, PATCH 1/1] rpmb: add Replay Protected Memory Block (RPMB) driver |
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Hi Sumit,
> On Mon, 21 Aug 2023 at 15:19, Jerome Forissier > <jerome.forissier@linaro.org> wrote: >> >> >> >> On 8/17/23 01:31, Shyam Saini wrote: >>> >>> Hi Ulf, >>> >>>> On Sat, 22 Jul 2023 at 03:41, Shyam Saini >>>> <shyamsaini@linux.microsoft.com> wrote: >>>>> >>>>> From: Alex Bennée <alex.bennee@linaro.org> >>>>> >>>>> [This is patch 1 from [1] Alex's submission and this RPMB layer was >>>>> originally proposed by [2]Thomas Winkler ] >>>>> >>>>> A number of storage technologies support a specialised hardware >>>>> partition designed to be resistant to replay attacks. The underlying >>>>> HW protocols differ but the operations are common. The RPMB partition >>>>> cannot be accessed via standard block layer, but by a set of specific >>>>> commands: WRITE, READ, GET_WRITE_COUNTER, and PROGRAM_KEY. Such a >>>>> partition provides authenticated and replay protected access, hence >>>>> suitable as a secure storage. >>>>> >>>>> The initial aim of this patch is to provide a simple RPMB Driver which >>>>> can be accessed by Linux's optee driver to facilitate fast-path for >>>>> RPMB access to optee OS(secure OS) during the boot time. [1] Currently, >>>>> Optee OS relies on user-tee supplicant to access eMMC RPMB partition. >>>>> >>>>> A TEE device driver can claim the RPMB interface, for example, via >>>>> class_interface_register(). The RPMB driver provides a series of >>>>> operations for interacting with the device. >>>> >>>> I don't quite follow this. More exactly, how will the TEE driver know >>>> what RPMB device it should use? >>> >>> I don't have complete code to for this yet, but i think OP-TEE driver >>> should register with RPMB subsystem and then we can have eMMC/UFS/NVMe >>> specific implementation for RPMB operations. >>> >>> Linux optee driver can handle RPMB frames and pass it to RPMB subsystem >>> > > It would be better to have this OP-TEE use case fully implemented. So > that we can justify it as a valid user for this proposed RPMB > subsystem. If you are looking for any further suggestions then please > let us know.
I was looking into UFS/NVMe user-space utils, it seems we may have to adapt rpmb frame data structure in optee-os to to handle NVMe/UFS specific bits.
For nvme rpmb data frame, I think we would need an extra "target" member in rpmb data frame structure, as NVMe can support upto 7 RPMB units, see [1] "struct rpmb_data_frame_t" UFS may support upto 3 or 4 RPMB regions.
So even if we use CID to uniquely identify RPMB device either from eMMC/NVMe/UFS, we still need identify which RPMB target/unit in case if the device is NVMe, and which RPMB region if the device UFS.
Also both NVMe/UFS utils have two extra RPMB operations implemented, Although new request/response operation than eMMC spec: 1) Authenticated Device Configuration Block Write 2) Authenticated Device Configuration Block Read
see [2] enum rpmb_request/response_type and [3]enum rpmb_op_type
do we need those implemented as well ?
Please let me know what you think about these.
[1] https://github.com/linux-nvme/nvme-cli/blob/master/nvme-rpmb.c#L252 [2] https://github.com/linux-nvme/nvme-cli/blob/master/nvme-rpmb.c#L230 [3] https://github.com/westerndigitalcorporation/ufs-utils/blob/dev/ufs_rpmb.c#L27
>>> [1] U-Boot has mmc specific implementation >>> >>> I think OPTEE-OS has CFG_RPMB_FS_DEV_ID option >>> CFG_RPMB_FS_DEV_ID=1 for /dev/mmcblk1rpmb, >> >> Correct. Note that tee-supplicant will ignore this device ID if --rmb-cid >> is given and use the specified RPMB instead (the CID is a non-ambiguous way >> to identify a RPMB device). >> >>> but in case if a >>> system has multiple RPMB devices such as UFS/eMMC/NVMe, one them >>> should be declared as secure storage and optee should access that one only. >> >> Indeed, that would be an equivalent of tee-supplicant's --rpmb-cid. >> >>> Sumit, do you have suggestions for this ? >> > > I would suggest having an OP-TEE secure DT property that would provide > the RPMB CID which is allocated to the secure world. > > -Sumit > >> >> -- >> Jerome >
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