[ 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. Also, anyone please let me know if you're interested in helping with the Qualcomm driver changes.] 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 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, and changes to fscrypt to allow the fscrypt master keys to be hardware-wrapped. Key generation and import, as well as the conversion of keys from long-term wrapped form to ephemerally-wrapped form, are currently considered out-of-scope. An open question is if/how the kernel can provide a generic UAPI for these parts (new block ioctls that call through to new methods in blk_ksm_ll_ops, maybe)? 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. - Patches 2-3 are cleanups to fscrypt documentation and key validation. These aren't specific to hardware-wrapped keys per se, so these don't need to wait for the rest of the patches. - Patch 4 adds the fscrypt support and documentation. This patchset applies to v5.14-rc7. It can also be retrieved from tag "wrapped-keys-v1" of https://git.kernel.org/pub/scm/fs/fscrypt/fscrypt.git. Eric Biggers (4): block: add hardware-wrapped key support fscrypt: improve documentation for inline encryption fscrypt: allow 256-bit master keys with AES-256-XTS fscrypt: add support for hardware-wrapped keys Documentation/block/inline-encryption.rst | 222 ++++++++++++++++++++- Documentation/filesystems/fscrypt.rst | 223 ++++++++++++++++++---- block/blk-crypto-fallback.c | 5 +- block/blk-crypto-internal.h | 1 + block/blk-crypto.c | 45 ++++- block/keyslot-manager.c | 67 +++++-- drivers/md/dm-table.c | 1 + drivers/mmc/host/cqhci-crypto.c | 2 + drivers/scsi/ufs/ufshcd-crypto.c | 1 + fs/crypto/fscrypt_private.h | 88 ++++++++- fs/crypto/hkdf.c | 15 +- fs/crypto/inline_crypt.c | 64 ++++++- fs/crypto/keyring.c | 119 ++++++++---- fs/crypto/keysetup.c | 131 +++++++++++-- fs/crypto/keysetup_v1.c | 5 +- fs/crypto/policy.c | 11 +- include/linux/blk-crypto.h | 70 ++++++- include/linux/keyslot-manager.h | 20 ++ include/uapi/linux/fscrypt.h | 7 +- 19 files changed, 959 insertions(+), 138 deletions(-) base-commit: e22ce8eb631bdc47a4a4ea7ecf4e4ba499db4f93 -- 2.32.0
