On 8/21/23 13:18, Jens Wiklander wrote: > On Mon, Aug 21, 2023 at 12:03 PM Sumit Garg <sumit.garg@xxxxxxxxxx> wrote: >> >> On Mon, 21 Aug 2023 at 15:19, Jerome Forissier >> <jerome.forissier@xxxxxxxxxx> wrote: >>> >>> >>> >>> On 8/17/23 01:31, Shyam Saini wrote: >>>> >>>> Hi Ulf, >>>> >>>>> On Sat, 22 Jul 2023 at 03:41, Shyam Saini >>>>> <shyamsaini@xxxxxxxxxxxxxxxxxxx> wrote: >>>>>> >>>>>> From: Alex Bennée <alex.bennee@xxxxxxxxxx> >>>>>> >>>>>> [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. > > +1 > >> >>>> [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. > > Another option is for OP-TEE to iterate over all RPMBs with a > programmed key and test if the key OP-TEE would use works. That should > avoid the problem of provisioning a device-unique secure DTB. I'd > expect that the RPMB key is programmed by a trusted provisioning tool > since allowing OP-TEE to program the RPMB key has never been secure, > not unless the OP-TEE binary is rollback protected. +1 if we can assume the same key won't be used for several devices, which is probably reasonable. > > Cheers, > Jens > >> >> -Sumit >> >>> >>> -- >>> Jerome
