On Thu, Sep 16, 2021 at 10:49:23AM -0700, Eric Biggers wrote: > [ NOTE: this patchset is an RFC that isn't ready for merging yet because > it doesn't yet include the vendor-specific UFS or eMMC driver changes > needed to actually use the feature. I.e., this patchset isn't > sufficient to actually use hardware-wrapped keys with upstream yet. > > For context, hardware-wrapped key support has been out-of-tree in the > Android kernels since early last year; upstreaming has been blocked on > hardware availability and support. However, an SoC that supports this > feature (SM8350, a.k.a. Qualcomm Snapdragon 888) finally has been > publicly released and had basic SoC support upstreamed. Also, some > other hardware will support the same feature soon. So, things should > be progressing soon. So while the driver changes are gotten into an > upstream-ready form, I wanted to get things started and give people a > chance to give early feedback on the plan for how the kernel will > support this type of hardware.] > > This patchset adds framework-level support (i.e., block and fscrypt > support) for hardware-wrapped keys when the inline encryption hardware > supports them. Hardware-wrapped keys are inline encryption keys that > are wrapped (encrypted) by a key internal to the hardware. Except at > initial unlocking time, the wrapping key is an ephemeral, per-boot key. > Hardware-wrapped keys can only be unwrapped (decrypted) by the hardware, > e.g. when a key is programmed into a keyslot. They are never visible to > software in raw form, except optionally during key generation (the > hardware supports importing keys as well as generating keys itself). > > This feature protects the encryption keys from read-only compromises of > kernel memory, such as that which can occur during a cold boot attack. > It does this without limiting the number of keys that can be used, as > would be the case with solutions that didn't use key wrapping. > > The kernel changes to support this feature basically consist of changes > to blk-crypto to allow a blk_crypto_key to be hardware-wrapped and to > allow storage drivers to support hardware-wrapped keys, new block device > ioctls for creating and preparing hardware-wrapped keys, and changes to > fscrypt to allow the fscrypt master keys to be hardware-wrapped. > > For full details, see the individual patches, especially the detailed > documentation they add to Documentation/block/inline-encryption.rst and > Documentation/filesystems/fscrypt.rst. > > This patchset is organized as follows: > > - Patch 1 adds the block support and documentation, excluding the ioctls > needed to get a key ready to be used in the first place. > > - Patch 2 adds new block device ioctls for creating and preparing > hardware-wrapped keys. > > - Patches 3-4 clean up the fscrypt documentation and key validation > logic. These aren't specific to hardware-wrapped keys per se, so > these don't need to wait for the rest of the patches. > > - Patch 5 adds the fscrypt support and documentation. > > This patchset applies to v5.15-rc1 plus my other patchset > "[PATCH v2 0/4] blk-crypto cleanups". It can also be retrieved from tag > "wrapped-keys-v2" of > https://git.kernel.org/pub/scm/fs/fscrypt/fscrypt.git. I'd greatly appreciate any feedback on this patch series; I don't know whether silence means everyone likes this, or everyone hates this, or no one cares :-) (Or maybe no one is interested until driver changes are included?) - Eric
