To prevent keys from being compromised if an attacker
acquires read access to kernel memory, some inline
encryption hardware supports protecting the keys in
hardware without software having access to or the
ability to set the plaintext keys. Instead, software
only sees "wrapped keys", which may differ on every boot.
'wrappedkey_v0' fileencryption flag is used to denote
that the device supports inline encryption hardware that
supports this feature. On such devices keymaster is used
to generate keys with STORAGE_KEY tag and export a
per-boot ephemerally wrapped storage key to install it in
the kernel.
The wrapped key framework in the linux kernel ensures the
wrapped key is provided to the inline encryption hardware
where it is unwrapped and the file contents key is derived
to encrypt contents without revealing the plaintext key in
the clear.
Test: FBE validation with Fscrypt v2 + inline crypt + wrapped
key changes kernel.
Bug: 147733587
Change-Id: I1f0de61b56534ec1df9baef075acb74bacd00758
aosp/1184798 has updated the kernel headers to 5.4, so we no longer need
the file fscrypt_uapi.h. In KeyUtil.cpp we also now don't need
<linux/fs.h>, but rather just the more specific <linux/fscrypt.h>.
Test: build
Bug: None
Change-Id: I56d17826eb7c3b95c74ce0435a4feae7f3cc325e
When the kernel supports the new fscrypt key management ioctls, use them
instead of add_key() and keyctl_unlink().
This will be needed in order to support v2 encryption policies, since v2
encryption policies only support the new ioctls.
The new ioctls have other advantages too. For example,
FS_IOC_REMOVE_ENCRYPTION_KEY automatically evicts exactly the necessary
kernel objects, so the drop_caches sysctl is no longer needed. This
makes evicting keys faster and more reliable.
FS_IOC_REMOVE_ENCRYPTION_KEY also detects if any files are still open
and therefore couldn't be "locked", whereas this went undetected before.
Therefore, to start out this patch adds support for using the new ioctls
for v1 encryption policies, i.e. on existing devices.
(Originally based on a patch by Satya Tangirala <satyat@google.com>)
Bug: 140500828
Test: tested that a device using v1 policies continues to work, both
with and without an updated kernel. See
If64028d8580584b2c33c614cabd5d6b93657f608 for more details.
Also checked via the log that the filesystem-level keyring is in
fact used when supported.
Change-Id: I296ef78138578a3fd773797ac0cd46af1296b959
Barani Muthukumaran
Eric Biggers