Hello Eric On 06/20/2024, 9:48 PM PDT, Eric Biggers wrote: > On Thu, Jun 20, 2024 at 02:57:40PM +0300, Dmitry Baryshkov wrote: > > > > > > > > > > > Is it possible to use both kind of keys when working on standard > mode? > > > > > > If not, it should be the user who selects what type of keys to be > used. > > > > > > Enforcing this via DT is not a way to go. > > > > > > > > > > > > > > > > Unfortunately, that support is not there yet. When you say user, > > > > > do you mean to have it as a filesystem mount option? > > > > > > > > During cryptsetup time. When running e.g. cryptsetup I, as a user, > > > > would like to be able to use either a hardware-wrapped key or a > standard key. > > > > > > > > > > What we are looking for with these patches is for per-file/folder > encryption using fscrypt policies. > > > Cryptsetup to my understanding supports only full-disk , and does > > > not support FBE (File-Based) > > > > I must admit, I mostly used dm-crypt beforehand, so I had to look at > > fscrypt now. Some of my previous comments might not be fully > > applicable. > > > > > Hence the idea here is that we mount an unencrypted device (with the > > > inlinecrypt option that indicates inline encryption is supported) And > specify policies (links to keys) for different folders. > > > > > > > > The way the UFS/EMMC crypto layer is designed currently is that, > > > > > this information is needed when the modules are loaded. > > > > > > > > > > https://lore.kernel.org/all/20231104211259.17448-2-ebiggers@kern > > > > > el.org /#Z31drivers:ufs:core:ufshcd-crypto.c > > > > > > > > I see that the driver lists capabilities here. E.g. that it > > > > supports HW-wrapped keys. But the line doesn't specify that standard > keys are not supported. > > > > > > > > > > Those are capabilities that are read from the storage controller. > > > However, wrapped keys Are not a standard in the ICE JEDEC > > > specification, and in most cases, is a value add coming from the SoC. > > > > > > QCOM SOC and firmware currently does not support both kinds of keys in > the HWKM mode. > > > That is something we are internally working on, but not available yet. > > > > I'd say this is a significant obstacle, at least from my point of > > view. I understand that the default might be to use hw-wrapped keys, > > but it should be possible for the user to select non-HW keys if the > > ability to recover the data is considered to be important. Note, I'm > > really pointing to the user here, not to the system integrator. So > > using DT property or specifying kernel arguments to switch between > > these modes is not really an option. > > > > But I'd really love to hear some feedback from linux-security and/or > > linux-fscrypt here. > > > > In my humble opinion the user should be able to specify that the key > > is wrapped using the hardware KMK. Then if the hardware has already > > started using the other kind of keys, it should be able to respond > > with -EINVAL / whatever else. Then the user can evict previously > > programmed key and program a desired one. > > > > > > Also, I'd have expected that hw-wrapped keys are handled using > > > > trusted keys mechanism (see security/keys/trusted-keys/). Could > > > > you please point out why that's not the case? > > > > > > > > > > I will evaluate this. > > > But my initial response is that we currently cannot communicate to > > > our TPM directly from HLOS, but goes through QTEE, and I don't think > > > our qtee currently interfaces with the open source tee driver. The > interface is through QCOM SCM driver. > > > > Note, this is just an API interface, see how it is implemented for the > > CAAM hardware. > > > > The problem is that this patchset was sent out without the patches that add > the block and filesystem-level framework for hardware-wrapped inline > encryption keys, which it depends on. So it's lacking context. The proposed > framework can be found at https://lore.kernel.org/linux- > block/20231104211259.17448-1-ebiggers@xxxxxxxxxx/T/#u > I have only been adding the fscryp patch link as part of the cover letter - as a dependency. https://lore.kernel.org/all/20240617005825.1443206-1-quic_gaurkash@xxxxxxxxxxx/ If you would like me to include it in the patch series itself, I can do that as well. > As for why "trusted keys" aren't used, they just aren't helpful here. "Trusted > keys" are based around a model where the kernel can request that keys be > sealed and unsealed using a trust source, and the kernel gets access to the > raw unsealed keys. Hardware-wrapped inline encryption keys use a > different model where the kernel never gets access to the raw keys. They > also have the concept of ephemeral wrapping which does not exist in > "trusted keys". And they need to be properly integrated with the inline > encryption framework in the block layer. > > - Eric Regards, Gaurav
