On Mon, 21 Aug 2023 at 17:26, Ilias Apalodimas <ilias.apalodimas@xxxxxxxxxx> wrote: > > On Mon, 21 Aug 2023 at 14:19, Jens Wiklander <jens.wiklander@xxxxxxxxxx> 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 to that. Overall we shound't 'trust' to do the programming. For > example, in OP-TEE if you compile it with device programming > capabilities, you can easily convince OP-TEE to send you the symmetric > key by swapping the supplicant with a malicious application. > Agree, with your overall intent, that OP-TEE shouldn't expose RPMB key in plain form. But with suggested OP-TEE RPMB frames routing via kernel, tee-supplicant won't be used for RPMB accesses. -Sumit > Thanks > /Ilias > > > > Cheers, > > Jens > > > > > > > > -Sumit > > > > > > > > > > > -- > > > > Jerome
