Use a common function for fscrypt warning and error messages so that all
the messages are consistently ratelimited, include the "fscrypt:"
prefix, and include the filesystem name if applicable.
Also fix up a few of the log messages to be more descriptive.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
skcipher_request_alloc() can only fail due to lack of memory, and in
that case the memory allocator will have already printed a detailed
error message. Thus, remove the redundant error messages from fscrypt.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Now that all filesystems have been converted to use
fscrypt_prepare_lookup(), we can remove the fscrypt_set_d_op() and
fscrypt_set_encrypted_dentry() functions as well as un-export
fscrypt_d_ops.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Improve fscrypt read performance by switching the decryption workqueue
from bound to unbound. With the bound workqueue, when multiple bios
completed on the same CPU, they were decrypted on that same CPU. But
with the unbound queue, they are now decrypted in parallel on any CPU.
Although fscrypt read performance can be tough to measure due to the
many sources of variation, this change is most beneficial when
decryption is slow, e.g. on CPUs without AES instructions. For example,
I timed tarring up encrypted directories on f2fs. On x86 with AES-NI
instructions disabled, the unbound workqueue improved performance by
about 25-35%, using 1 to NUM_CPUs jobs with 4 or 8 CPUs available. But
with AES-NI enabled, performance was unchanged to within ~2%.
I also did the same test on a quad-core ARM CPU using xts-speck128-neon
encryption. There performance was usually about 10% better with the
unbound workqueue, bringing it closer to the unencrypted speed.
The unbound workqueue may be worse in some cases due to worse locality,
but I think it's still the better default. dm-crypt uses an unbound
workqueue by default too, so this change makes fscrypt match.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Currently, fscrypt provides fscrypt_decrypt_bio_pages() which decrypts a
bio's pages asynchronously, then unlocks them afterwards. But, this
assumes that decryption is the last "postprocessing step" for the bio,
so it's incompatible with additional postprocessing steps such as
authenticity verification after decryption.
Therefore, rename the existing fscrypt_decrypt_bio_pages() to
fscrypt_enqueue_decrypt_bio(). Then, add fscrypt_decrypt_bio() which
decrypts the pages in the bio synchronously without unlocking the pages,
nor setting them Uptodate; and add fscrypt_enqueue_decrypt_work(), which
enqueues work on the fscrypt_read_workqueue. The new functions will be
used by filesystems that support both fscrypt and fs-verity.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
fscrypt.h included way too many other headers, given that it is included
by filesystems both with and without encryption support. Trim down the
includes list by moving the needed includes into more appropriate
places, and removing the unneeded ones.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
fscrypt starts several async. crypto ops and waiting for them to
complete. Move it over to generic code doing the same.
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
fscrypt_initialize(), which allocates the global bounce page pool when
an encrypted file is first accessed, uses "double-checked locking" to
try to avoid locking fscrypt_init_mutex. However, it doesn't use any
memory barriers, so it's theoretically possible for a thread to observe
a bounce page pool which has not been fully initialized. This is a
classic bug with "double-checked locking".
While "only a theoretical issue" in the latest kernel, in pre-4.8
kernels the pointer that was checked was not even the last to be
initialized, so it was easily possible for a crash (NULL pointer
dereference) to happen. This was changed only incidentally by the large
refactor to use fs/crypto/.
Solve both problems in a trivial way that can easily be backported: just
always take the mutex. It's theoretically less efficient, but it
shouldn't be noticeable in practice as the mutex is only acquired very
briefly once per encrypted file.
Later I'd like to make this use a helper macro like DO_ONCE(). However,
DO_ONCE() runs in atomic context, so we'd need to add a new macro that
allows blocking.
Cc: stable@vger.kernel.org # v4.1+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
IS_ENCRYPTED() now gives the same information as
i_sb->s_cop->is_encrypted() but is more efficient, since IS_ENCRYPTED()
is just a simple flag check. Prepare to remove ->is_encrypted() by
switching all callers to IS_ENCRYPTED().
Acked-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
fscrypt provides facilities to use different encryption algorithms which
are selectable by userspace when setting the encryption policy. Currently,
only AES-256-XTS for file contents and AES-256-CBC-CTS for file names are
implemented. This is a clear case of kernel offers the mechanism and
userspace selects a policy. Similar to what dm-crypt and ecryptfs have.
This patch adds support for using AES-128-CBC for file contents and
AES-128-CBC-CTS for file name encryption. To mitigate watermarking
attacks, IVs are generated using the ESSIV algorithm. While AES-CBC is
actually slightly less secure than AES-XTS from a security point of view,
there is more widespread hardware support. Using AES-CBC gives us the
acceptable performance while still providing a moderate level of security
for persistent storage.
Especially low-powered embedded devices with crypto accelerators such as
CAAM or CESA often only support AES-CBC. Since using AES-CBC over AES-XTS
is basically thought of a last resort, we use AES-128-CBC over AES-256-CBC
since it has less encryption rounds and yields noticeable better
performance starting from a file size of just a few kB.
Signed-off-by: Daniel Walter <dwalter@sigma-star.at>
[david@sigma-star.at: addressed review comments]
Signed-off-by: David Gstir <david@sigma-star.at>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Filesystem encryption ostensibly supported revoking a keyring key that
had been used to "unlock" encrypted files, causing those files to become
"locked" again. This was, however, buggy for several reasons, the most
severe of which was that when key revocation happened to be detected for
an inode, its fscrypt_info was immediately freed, even while other
threads could be using it for encryption or decryption concurrently.
This could be exploited to crash the kernel or worse.
This patch fixes the use-after-free by removing the code which detects
the keyring key having been revoked, invalidated, or expired. Instead,
an encrypted inode that is "unlocked" now simply remains unlocked until
it is evicted from memory. Note that this is no worse than the case for
block device-level encryption, e.g. dm-crypt, and it still remains
possible for a privileged user to evict unused pages, inodes, and
dentries by running 'sync; echo 3 > /proc/sys/vm/drop_caches', or by
simply unmounting the filesystem. In fact, one of those actions was
already needed anyway for key revocation to work even somewhat sanely.
This change is not expected to break any applications.
In the future I'd like to implement a real API for fscrypt key
revocation that interacts sanely with ongoing filesystem operations ---
waiting for existing operations to complete and blocking new operations,
and invalidating and sanitizing key material and plaintext from the VFS
caches. But this is a hard problem, and for now this bug must be fixed.
This bug affected almost all versions of ext4, f2fs, and ubifs
encryption, and it was potentially reachable in any kernel configured
with encryption support (CONFIG_EXT4_ENCRYPTION=y,
CONFIG_EXT4_FS_ENCRYPTION=y, CONFIG_F2FS_FS_ENCRYPTION=y, or
CONFIG_UBIFS_FS_ENCRYPTION=y). Note that older kernels did not use the
shared fs/crypto/ code, but due to the potential security implications
of this bug, it may still be worthwhile to backport this fix to them.
Fixes: b7236e21d5 ("ext4 crypto: reorganize how we store keys in the inode")
Cc: stable@vger.kernel.org # v4.2+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: Michael Halcrow <mhalcrow@google.com>
fscrypt:
- fs/crypto/bio.c changes
f2fs:
- fscrypt: use ENOKEY when file cannot be created w/o key
- fscrypt: split supp and notsupp declarations into their own headers
- fscrypt: make fscrypt_operations.key_prefix a string
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
