Pull fscrypt updates from Ted Ts'o: "Add Adiantum support for fscrypt" * tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt: fscrypt: add Adiantum support
Add support for the Adiantum encryption mode to fscrypt. Adiantum is a
tweakable, length-preserving encryption mode with security provably
reducible to that of XChaCha12 and AES-256, subject to a security bound.
It's also a true wide-block mode, unlike XTS. See the paper
"Adiantum: length-preserving encryption for entry-level processors"
(https://eprint.iacr.org/2018/720.pdf) for more details. Also see
commit 059c2a4d8e16 ("crypto: adiantum - add Adiantum support").
On sufficiently long messages, Adiantum's bottlenecks are XChaCha12 and
the NH hash function. These algorithms are fast even on processors
without dedicated crypto instructions. Adiantum makes it feasible to
enable storage encryption on low-end mobile devices that lack AES
instructions; currently such devices are unencrypted. On ARM Cortex-A7,
on 4096-byte messages Adiantum encryption is about 4 times faster than
AES-256-XTS encryption; decryption is about 5 times faster.
In fscrypt, Adiantum is suitable for encrypting both file contents and
names. With filenames, it fixes a known weakness: when two filenames in
a directory share a common prefix of >= 16 bytes, with CTS-CBC their
encrypted filenames share a common prefix too, leaking information.
Adiantum does not have this problem.
Since Adiantum also accepts long tweaks (IVs), it's also safe to use the
master key directly for Adiantum encryption rather than deriving
per-file keys, provided that the per-file nonce is included in the IVs
and the master key isn't used for any other encryption mode. This
configuration saves memory and improves performance. A new fscrypt
policy flag is added to allow users to opt-in to this configuration.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Only the mount namespace code that implements mount(2) should be using the MS_* flags. Suppress them inside the kernel unless uapi/linux/mount.h is included. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Reviewed-by: David Howells <dhowells@redhat.com>
These are unused, undesired, and have never actually been used by anybody. The original authors of this code have changed their mind about its inclusion. While originally proposed for disk encryption on low-end devices, the idea was discarded [1] in favor of something else before that could really get going. Therefore, this patch removes Speck. [1] https://marc.info/?l=linux-crypto-vger&m=153359499015659 Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Acked-by: Eric Biggers <ebiggers@google.com> Cc: stable@vger.kernel.org Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Pull fscrypt updates from Ted Ts'o: "Add bunch of cleanups, and add support for the Speck128/256 algorithms. Yes, Speck is contrversial, but the intention is to use them only for the lowest end Android devices, where the alternative *really* is no encryption at all for data stored at rest" * tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt: fscrypt: log the crypto algorithm implementations fscrypt: add Speck128/256 support fscrypt: only derive the needed portion of the key fscrypt: separate key lookup from key derivation fscrypt: use a common logging function fscrypt: remove internal key size constants fscrypt: remove unnecessary check for non-logon key type fscrypt: make fscrypt_operations.max_namelen an integer fscrypt: drop empty name check from fname_decrypt() fscrypt: drop max_namelen check from fname_decrypt() fscrypt: don't special-case EOPNOTSUPP from fscrypt_get_encryption_info() fscrypt: don't clear flags on crypto transform fscrypt: remove stale comment from fscrypt_d_revalidate() fscrypt: remove error messages for skcipher_request_alloc() failure fscrypt: remove unnecessary NULL check when allocating skcipher fscrypt: clean up after fscrypt_prepare_lookup() conversions fs, fscrypt: only define ->s_cop when FS_ENCRYPTION is enabled fscrypt: use unbound workqueue for decryption
fscrypt currently only supports AES encryption. However, many low-end mobile devices have older CPUs that don't have AES instructions, e.g. the ARMv8 Cryptography Extensions. Currently, user data on such devices is not encrypted at rest because AES is too slow, even when the NEON bit-sliced implementation of AES is used. Unfortunately, it is infeasible to encrypt these devices at all when AES is the only option. Therefore, this patch updates fscrypt to support the Speck block cipher, which was recently added to the crypto API. The C implementation of Speck is not especially fast, but Speck can be implemented very efficiently with general-purpose vector instructions, e.g. ARM NEON. For example, on an ARMv7 processor, we measured the NEON-accelerated Speck128/256-XTS at 69 MB/s for both encryption and decryption, while AES-256-XTS with the NEON bit-sliced implementation was only 22 MB/s encryption and 19 MB/s decryption. There are multiple variants of Speck. This patch only adds support for Speck128/256, which is the variant with a 128-bit block size and 256-bit key size -- the same as AES-256. This is believed to be the most secure variant of Speck, and it's only about 6% slower than Speck128/128. Speck64/128 would be at least 20% faster because it has 20% rounds, and it can be even faster on CPUs that can't efficiently do the 64-bit operations needed for Speck128. However, Speck64's 64-bit block size is not preferred security-wise. ARM NEON also supports the needed 64-bit operations even on 32-bit CPUs, resulting in Speck128 being fast enough for our targeted use cases so far. The chosen modes of operation are XTS for contents and CTS-CBC for filenames. These are the same modes of operation that fscrypt defaults to for AES. Note that as with the other fscrypt modes, Speck will not be used unless userspace chooses to use it. Nor are any of the existing modes (which are all AES-based) being removed, of course. We intentionally don't make CONFIG_FS_ENCRYPTION select CONFIG_CRYPTO_SPECK, so people will have to enable Speck support themselves if they need it. This is because we shouldn't bloat the FS_ENCRYPTION dependencies with every new cipher, especially ones that aren't recommended for most users. Moreover, CRYPTO_SPECK is just the generic implementation, which won't be fast enough for many users; in practice, they'll need to enable CRYPTO_SPECK_NEON to get acceptable performance. More details about our choice of Speck can be found in our patches that added Speck to the crypto API, and the follow-on discussion threads. We're planning a publication that explains the choice in more detail. But briefly, we can't use ChaCha20 as we previously proposed, since it would be insecure to use a stream cipher in this context, with potential IV reuse during writes on f2fs and/or on wear-leveling flash storage. We also evaluated many other lightweight and/or ARX-based block ciphers such as Chaskey-LTS, RC5, LEA, CHAM, Threefish, RC6, NOEKEON, SPARX, and XTEA. However, all had disadvantages vs. Speck, such as insufficient performance with NEON, much less published cryptanalysis, or an insufficient security level. Various design choices in Speck make it perform better with NEON than competing ciphers while still having a security margin similar to AES, and in the case of Speck128 also the same available security levels. Unfortunately, Speck does have some political baggage attached -- it's an NSA designed cipher, and was rejected from an ISO standard (though for context, as far as I know none of the above-mentioned alternatives are ISO standards either). Nevertheless, we believe it is a good solution to the problem from a technical perspective. Certain algorithms constructed from ChaCha or the ChaCha permutation, such as MEM (Masked Even-Mansour) or HPolyC, may also meet our performance requirements. However, these are new constructions that need more time to receive the cryptographic review and acceptance needed to be confident in their security. HPolyC hasn't been published yet, and we are concerned that MEM makes stronger assumptions about the underlying permutation than the ChaCha stream cipher does. In contrast, the XTS mode of operation is relatively well accepted, and Speck has over 70 cryptanalysis papers. Of course, these ChaCha-based algorithms can still be added later if they become ready. The best known attack on Speck128/256 is a differential cryptanalysis attack on 25 of 34 rounds with 2^253 time complexity and 2^125 chosen plaintexts, i.e. only marginally faster than brute force. There is no known attack on the full 34 rounds. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This retains 256 chars as the maximum size through the interface, which is the btrfs limit and AFAIK exceeds any other filesystem's maximum label size. This just copies the ioctl for now and leaves it in place for btrfs for the time being. A later patch will allow btrfs to use the new common ioctl definition, but it may be sent after this is merged. (Note, Reviewed-by's were originally given for the combined vfs+btrfs patch, some license taken here.) Signed-off-by: Eric Sandeen <sandeen@redhat.com> Reviewed-by: Andreas Dilger <adilger@dilger.ca> Reviewed-by: David Sterba <dsterba@suse.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This is the per-I/O equivalent of O_APPEND to support atomic append operations on any open file. If a file is opened with O_APPEND, pwrite() ignores the offset and always appends data to the end of the file. RWF_APPEND enables atomic append and pwrite() with offset on a single file descriptor. Signed-off-by: Jürg Billeter <j@bitron.ch> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Many user space API headers are missing licensing information, which makes it hard for compliance tools to determine the correct license. By default are files without license information under the default license of the kernel, which is GPLV2. Marking them GPLV2 would exclude them from being included in non GPLV2 code, which is obviously not intended. The user space API headers fall under the syscall exception which is in the kernels COPYING file: NOTE! This copyright does *not* cover user programs that use kernel services by normal system calls - this is merely considered normal use of the kernel, and does *not* fall under the heading of "derived work". otherwise syscall usage would not be possible. Update the files which contain no license information with an SPDX license identifier. The chosen identifier is 'GPL-2.0 WITH Linux-syscall-note' which is the officially assigned identifier for the Linux syscall exception. SPDX license identifiers are a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. See the previous patch in this series for the methodology of how this patch was researched. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[AV: added missing annotations in syscalls.h/compat.h] Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>