[PATCH v11 0/7] Support for hardware-wrapped inline encryption keys

Eric Biggers
2025-02-04T06:03:21Z

This patchset is based on v6.14-rc1 and is also available at:

git fetch https://git.kernel.org/pub/scm/fs/fscrypt/linux.git wrapped-keys-v11

This patchset adds support for hardware-wrapped inline encryption keys,
a security feature supported by some SoCs. It adds the block and
fscrypt framework for the feature as well as support for it with UFS on
Qualcomm SoCs.

This feature is described in full detail in the included Documentation
changes. But to summarize, hardware-wrapped keys are inline encryption
keys that are wrapped (encrypted) by a key internal to the hardware so
that they can only be unwrapped (decrypted) by the hardware. Initially
keys are wrapped with a permanent hardware key, but during actual use
they are re-wrapped with a per-boot ephemeral key for improved security.
The hardware supports importing keys as well as generating keys itself.

This differs from the existing support for hardware-wrapped keys in the
kernel crypto API (also called "hardware-bound keys" in some places) in
the same way that the crypto API differs from blk-crypto: the crypto API
is for general crypto operations, whereas blk-crypto is for inline
storage encryption.

This feature is already being used by Android downstream for several
years
(https://source.android.com/docs/security/features/encryption/hw-wrapped-keys),
but on other platforms userspace support will be provided via fscryptctl
and tests via xfstests. The tests have been merged into xfstests, and
they pass on the SM8650 HDK with the upstream kernel plus this patchset.

This is targeting 6.15. As per the suggestion from Jens
(https://lore.kernel.org/linux-block/c3407d1c-6c5c-42ee-b446-ccbab1643a62@kernel.dk/),
I'd like patches 1-3 to be queued up into a branch that gets pulled into
the block tree. I'll then take patches 4-7 through the fscrypt tree,
also for 6.15. If I end up with too many merge conflicts by trying to
take patches 5-7 (given that this is a cross-subsystem feature), my
fallback plan will be to wait until 6.16 to land patches 5-7, when they
will finally be unblocked by the block patches having landed.

Changed in v11:
- Rebased onto v6.14-rc1. Dropped the patches that were upstreamed in
6.14, and put the block patches first in the series again.
- Significantly cleaned up the patch "soc: qcom: ice: add HWKM support
to the ICE driver". Some of the notable changes were dropping the
unnecessary support for HWKM v1, and replacing qcom_ice_using_hwkm()
with qcom_ice_get_supported_key_type().
- Consistently used and documented the EBADMSG error code for invalid
hardware-wrapped keys.
- Other minor cleanups.

Changed in v10:
- Fixed bugs in qcom_scm_derive_sw_secret() and cqhci_crypto_init().
- Added "ufs: qcom: fix crypto key eviction" and
"mmc: sdhci-msm: fix crypto key eviction".
- Split removing ufs_hba_variant_ops::program_key into its own patch.
- Minor cleanups.
- Added Tested-by.

Changed in v9 (relative to v7 patchset from Bartosz Golaszewski):
- ufs-qcom and sdhci-msm now just initialize the blk_crypto_profile
themselves, like what ufs-exynos was doing. This avoids needing to
add all the host-specific hooks for wrapped key support to the MMC
and UFS core drivers.
- When passing the blk_crypto_key further down the stack, it now
replaces parameters like the algorithm ID, to avoid creating two
sources of truth.
- The module parameter qcom_ice.use_wrapped_keys should work correctly now.
- The fscrypt support no longer uses a policy flag to indicate when a
file is protected by a HW-wrapped key, since it was already implied
by the file's key identifier being that of a HW-wrapped key.
Originally there was an issue where raw and HW-wrapped keys could
share key identifiers, but I had fixed that earlier by introducing a
new HKDF context byte.
- The term "standard keys" is no longer used. Now "raw keys" is
consistently used instead. I've found that people find the term
"raw keys" to be more intuitive. Also HW-wrapped keys could in
principle be standardized.
- I've reordered the patchset to place preparatory patches that don't
depend on the actual HW-wrapped key support first.

For older changelogs, see
https://lore.kernel.org/r/20241202-wrapped-keys-v7-0-67c3ca3f3282@linaro.org and
https://lore.kernel.org/r/20231104211259.17448-1-ebiggers@kernel.org

Eric Biggers (6):
blk-crypto: add basic hardware-wrapped key support
blk-crypto: show supported key types in sysfs
blk-crypto: add ioctls to create and prepare hardware-wrapped keys
fscrypt: add support for hardware-wrapped keys
soc: qcom: ice: make qcom_ice_program_key() take struct blk_crypto_key
ufs: qcom: add support for wrapped keys

Gaurav Kashyap (1):
soc: qcom: ice: add HWKM support to the ICE driver

Documentation/ABI/stable/sysfs-block | 20 +
Documentation/block/inline-encryption.rst | 255 ++++++++++++-
Documentation/filesystems/fscrypt.rst | 200 ++++++++--
.../userspace-api/ioctl/ioctl-number.rst | 2 +
block/blk-crypto-fallback.c | 7 +-
block/blk-crypto-internal.h | 10 +
block/blk-crypto-profile.c | 101 +++++
block/blk-crypto-sysfs.c | 35 ++
block/blk-crypto.c | 204 +++++++++-
block/ioctl.c | 5 +
drivers/md/dm-table.c | 1 +
drivers/mmc/host/cqhci-crypto.c | 8 +-
drivers/mmc/host/sdhci-msm.c | 17 +-
drivers/soc/qcom/ice.c | 349 ++++++++++++++++--
drivers/ufs/core/ufshcd-crypto.c | 7 +-
drivers/ufs/host/ufs-exynos.c | 3 +-
drivers/ufs/host/ufs-qcom.c | 56 ++-
fs/crypto/fscrypt_private.h | 75 +++-
fs/crypto/hkdf.c | 4 +-
fs/crypto/inline_crypt.c | 42 ++-
fs/crypto/keyring.c | 157 ++++++--
fs/crypto/keysetup.c | 63 +++-
fs/crypto/keysetup_v1.c | 4 +-
include/linux/blk-crypto-profile.h | 73 ++++
include/linux/blk-crypto.h | 73 +++-
include/soc/qcom/ice.h | 34 +-
include/uapi/linux/blk-crypto.h | 44 +++
include/uapi/linux/fs.h | 6 +-
include/uapi/linux/fscrypt.h | 7 +-
29 files changed, 1654 insertions(+), 208 deletions(-)
create mode 100644 include/uapi/linux/blk-crypto.h

base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b
--
2.48.1