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c07d3aede2
Add support for hardware-wrapped keys to fscrypt. Such keys are protected from certain attacks, such as cold boot attacks. For more information, see the "Hardware-wrapped keys" section of Documentation/block/inline-encryption.rst. To support hardware-wrapped keys in fscrypt, we allow the fscrypt master keys to be hardware-wrapped. File contents encryption is done by passing the wrapped key to the inline encryption hardware via blk-crypto. Other fscrypt operations such as filenames encryption continue to be done by the kernel, using the "software secret" which the hardware derives. For more information, see the documentation which this patch adds to Documentation/filesystems/fscrypt.rst. Note that this feature doesn't require any filesystem-specific changes. However it does depend on inline encryption support, and thus currently it is only applicable to ext4 and f2fs. The version of this feature introduced by this patch is mostly equivalent to the version that has existed downstream in the Android Common Kernels since 2020. However, a couple fixes are included. First, the flags field in struct fscrypt_add_key_arg is now placed in the proper location. Second, key identifiers for HW-wrapped keys are now derived using a distinct HKDF context byte; this fixes a bug where a raw key could have the same identifier as a HW-wrapped key. Note that as a result of these fixes, the version of this feature introduced by this patch is not UAPI or on-disk format compatible with the version in the Android Common Kernels, though the divergence is limited to just those specific fixes. This version should be used going forwards. This patch has been heavily rewritten from the original version by Gaurav Kashyap <quic_gaurkash@quicinc.com> and Barani Muthukumaran <bmuthuku@codeaurora.org>. Tested-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> # sm8650 Link: https://lore.kernel.org/r/20250404225859.172344-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.