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Eric Biggers aa7624093c crypto: chacha - add XChaCha12 support
Now that the generic implementation of ChaCha20 has been refactored to
allow varying the number of rounds, add support for XChaCha12, which is
the XSalsa construction applied to ChaCha12.  ChaCha12 is one of the
three ciphers specified by the original ChaCha paper
(https://cr.yp.to/chacha/chacha-20080128.pdf: "ChaCha, a variant of
Salsa20"), alongside ChaCha8 and ChaCha20.  ChaCha12 is faster than
ChaCha20 but has a lower, but still large, security margin.

We need XChaCha12 support so that it can be used in the Adiantum
encryption mode, which enables disk/file encryption on low-end mobile
devices where AES-XTS is too slow as the CPUs lack AES instructions.

We'd prefer XChaCha20 (the more popular variant), but it's too slow on
some of our target devices, so at least in some cases we do need the
XChaCha12-based version.  In more detail, the problem is that Adiantum
is still much slower than we're happy with, and encryption still has a
quite noticeable effect on the feel of low-end devices.  Users and
vendors push back hard against encryption that degrades the user
experience, which always risks encryption being disabled entirely.  So
we need to choose the fastest option that gives us a solid margin of
security, and here that's XChaCha12.  The best known attack on ChaCha
breaks only 7 rounds and has 2^235 time complexity, so ChaCha12's
security margin is still better than AES-256's.  Much has been learned
about cryptanalysis of ARX ciphers since Salsa20 was originally designed
in 2005, and it now seems we can be comfortable with a smaller number of
rounds.  The eSTREAM project also suggests the 12-round version of
Salsa20 as providing the best balance among the different variants:
combining very good performance with a "comfortable margin of security".

Note that it would be trivial to add vanilla ChaCha12 in addition to
XChaCha12.  However, it's unneeded for now and therefore is omitted.

As discussed in the patch that introduced XChaCha20 support, I
considered splitting the code into separate chacha-common, chacha20,
xchacha20, and xchacha12 modules, so that these algorithms could be
enabled/disabled independently.  However, since nearly all the code is
shared anyway, I ultimately decided there would have been little benefit
to the added complexity.

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2018-11-20 14:26:55 +08:00
..
asymmetric_keys KEYS: asym_tpm: Add support for the sign operation [ver #2] 2018-10-26 09:30:47 +01:00
async_tx async_pq: Remove VLA usage 2018-06-18 20:17:38 +05:30
842.c crypto: acomp - add support for 842 via scomp 2016-10-25 11:08:33 +08:00
Kconfig crypto: chacha - add XChaCha12 support 2018-11-20 14:26:55 +08:00
Makefile crypto: chacha20-generic - refactor to allow varying number of rounds 2018-11-20 14:26:55 +08:00
ablkcipher.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
acompress.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
aead.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
aegis.h crypto: aegis/generic - fix for big endian systems 2018-10-08 13:44:53 +08:00
aegis128.c crypto: aead - remove useless setting of type flags 2018-07-09 00:30:26 +08:00
aegis128l.c crypto: aead - remove useless setting of type flags 2018-07-09 00:30:26 +08:00
aegis256.c crypto: aead - remove useless setting of type flags 2018-07-09 00:30:26 +08:00
aes_generic.c crypto: arm/aes - add some hardening against cache-timing attacks 2018-11-09 17:36:48 +08:00
aes_ti.c crypto: aes_ti - disable interrupts while accessing S-box 2018-11-09 17:36:48 +08:00
af_alg.c Revert "net: simplify sock_poll_wait" 2018-10-23 10:57:06 -07:00
ahash.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
akcipher.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
algapi.c crypto: user - Implement a generic crypto statistics 2018-09-28 12:46:25 +08:00
algboss.c crypto: api - Introduce notifier for new crypto algorithms 2018-09-04 11:37:04 +08:00
algif_aead.c crypto: null - Remove VLA usage of skcipher 2018-09-28 12:46:08 +08:00
algif_hash.c crypto: hash - Remove VLA usage 2018-09-04 11:35:03 +08:00
algif_rng.c net: remove sock_no_poll 2018-05-26 09:16:44 +02:00
algif_skcipher.c Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL 2018-06-28 10:40:47 -07:00
ansi_cprng.c crypto: ansi_cprng - Convert to new rng interface 2015-04-22 09:30:18 +08:00
anubis.c crypto: prefix module autoloading with "crypto-" 2014-11-24 22:43:57 +08:00
api.c evm: Don't deadlock if a crypto algorithm is unavailable 2018-07-18 07:27:22 -04:00
arc4.c crypto: prefix module autoloading with "crypto-" 2014-11-24 22:43:57 +08:00
authenc.c crypto: null - Remove VLA usage of skcipher 2018-09-28 12:46:08 +08:00
authencesn.c crypto: null - Remove VLA usage of skcipher 2018-09-28 12:46:08 +08:00
blkcipher.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
blowfish_common.c crypto: blowfish - split generic and common c code 2011-09-22 21:25:25 +10:00
blowfish_generic.c crypto: add missing crypto module aliases 2015-01-13 22:29:11 +11:00
camellia_generic.c crypto: replace FSF address with web source in license notices 2017-11-29 17:33:25 +11:00
cast5_generic.c crypto: replace FSF address with web source in license notices 2017-11-29 17:33:25 +11:00
cast6_generic.c crypto: replace FSF address with web source in license notices 2017-11-29 17:33:25 +11:00
cast_common.c crypto: make tables used from assembler __visible 2013-08-14 20:42:03 +10:00
cbc.c crypto: cbc - Propagate NEED_FALLBACK bit 2017-03-09 18:34:39 +08:00
ccm.c crypto: ccm - Remove VLA usage 2018-09-04 11:35:03 +08:00
cfb.c crypto: cfb - fix decryption 2018-11-09 17:40:59 +08:00
chacha20poly1305.c crypto: chacha20-generic - refactor to allow varying number of rounds 2018-11-20 14:26:55 +08:00
chacha_generic.c crypto: chacha - add XChaCha12 support 2018-11-20 14:26:55 +08:00
cipher.c crypto: remove several VLAs 2018-04-21 00:58:34 +08:00
cmac.c crypto: algapi - make crypto_xor() and crypto_inc() alignment agnostic 2017-02-11 17:52:28 +08:00
compress.c crypto: api - Remove no-op exit_ops code 2016-10-21 11:03:42 +08:00
crc32_generic.c crypto: crc32-generic - remove __crc32_le() 2018-05-27 00:12:09 +08:00
crc32c_generic.c crypto: crc32c-generic - remove cra_alignmask 2018-05-27 00:12:08 +08:00
crct10dif_common.c crypto: crct10dif - Add fallback for broken initrds 2013-09-12 15:31:34 +10:00
crct10dif_generic.c crypto: squash lines for simple wrapper functions 2016-09-13 20:27:26 +08:00
cryptd.c crypto: cryptd - Remove VLA usage of skcipher 2018-09-28 12:46:08 +08:00
crypto_engine.c crypto: engine - Permit to enqueue all async requests 2018-02-15 23:26:50 +08:00
crypto_null.c crypto: null - Remove VLA usage of skcipher 2018-09-28 12:46:08 +08:00
crypto_user_base.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
crypto_user_stat.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
crypto_wq.c crypto: crypto_wq - Fix late crypto work queue initialization 2014-03-21 21:54:28 +08:00
ctr.c crypto: remove several VLAs 2018-04-21 00:58:34 +08:00
cts.c crypto: remove several VLAs 2018-04-21 00:58:34 +08:00
deflate.c crypto: scomp - add support for deflate rfc1950 (zlib) 2017-04-24 18:11:08 +08:00
des_generic.c crypto: add missing crypto module aliases 2015-01-13 22:29:11 +11:00
dh.c crypto: dh - fix memory leak 2018-07-20 13:51:21 +08:00
dh_helper.c crypto: dh - make crypto_dh_encode_key() make robust 2018-08-03 18:06:06 +08:00
drbg.c crypto: drbg - in-place cipher operation for CTR 2018-08-03 18:05:48 +08:00
ecb.c crypto: include crypto- module prefix in template 2014-11-26 20:06:30 +08:00
ecc.c crypto: ecc - regularize scalar for scalar multiplication 2018-11-16 14:11:04 +08:00
ecc.h crypto: ecc - Actually remove stack VLA usage 2018-04-21 00:58:29 +08:00
ecc_curve_defs.h crypto: ecdh - fix typo of P-192 b value 2018-07-20 13:51:22 +08:00
ecdh.c crypto: ecc - Actually remove stack VLA usage 2018-04-21 00:58:29 +08:00
ecdh_helper.c crypto: ecdh - return unsigned value for crypto_ecdh_key_len() 2017-10-12 22:55:00 +08:00
echainiv.c crypto: null - Remove VLA usage of skcipher 2018-09-28 12:46:08 +08:00
fcrypt.c crypto: prefix module autoloading with "crypto-" 2014-11-24 22:43:57 +08:00
fips.c crypto: fips - Move fips_enabled sysctl into fips.c 2015-04-23 14:18:09 +08:00
gcm.c crypto: null - Remove VLA usage of skcipher 2018-09-28 12:46:08 +08:00
gf128mul.c crypto: gf128mul - remove incorrect comment 2017-12-22 19:52:40 +11:00
ghash-generic.c crypto: shash - remove useless setting of type flags 2018-07-09 00:30:24 +08:00
hash_info.c crypto: streebog - register Streebog in hash info for IMA 2018-11-16 14:09:40 +08:00
hmac.c crypto: hmac - require that the underlying hash algorithm is unkeyed 2017-11-29 13:39:15 +11:00
internal.h crypto: api - Introduce notifier for new crypto algorithms 2018-09-04 11:37:04 +08:00
jitterentropy-kcapi.c crypto: jitterentropy - drop duplicate header module.h 2016-11-17 23:34:52 +08:00
jitterentropy.c crypto: jitterentropy - Delete unnecessary checks before the function call "kzfree" 2015-06-25 23:18:33 +08:00
keywrap.c crypto: keywrap - Add missing ULL suffixes for 64-bit constants 2017-11-29 17:33:26 +11:00
khazad.c crypto: prefix module autoloading with "crypto-" 2014-11-24 22:43:57 +08:00
kpp.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
lrw.c crypto: lrw - fix rebase error after out of bounds fix 2018-10-05 10:22:48 +08:00
lz4.c crypto: remove useless initializations of cra_list 2018-11-20 14:26:55 +08:00
lz4hc.c crypto: remove useless initializations of cra_list 2018-11-20 14:26:55 +08:00
lzo.c treewide: use kv[mz]alloc* rather than opencoded variants 2017-05-08 17:15:13 -07:00
md4.c crypto: shash - remove useless setting of type flags 2018-07-09 00:30:24 +08:00
md5.c crypto: shash - remove useless setting of type flags 2018-07-09 00:30:24 +08:00
memneq.c crypto: memneq - fix for archs without efficient unaligned access 2013-12-09 20:09:12 +08:00
michael_mic.c crypto: prefix module autoloading with "crypto-" 2014-11-24 22:43:57 +08:00
morus640.c crypto: morus/generic - fix for big endian systems 2018-10-08 13:44:53 +08:00
morus1280.c crypto: morus/generic - fix for big endian systems 2018-10-08 13:44:53 +08:00
ofb.c crypto: ofb - add output feedback mode 2018-09-28 12:46:26 +08:00
pcbc.c crypto: remove several VLAs 2018-04-21 00:58:34 +08:00
pcrypt.c pcrypt: use format specifier in kobject_add 2018-11-09 17:41:39 +08:00
poly1305_generic.c crypto: shash - remove useless setting of type flags 2018-07-09 00:30:24 +08:00
proc.c proc: introduce proc_create_seq{,_data} 2018-05-16 07:23:35 +02:00
ripemd.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
rmd128.c crypto: shash - remove useless setting of type flags 2018-07-09 00:30:24 +08:00
rmd160.c crypto: shash - remove useless setting of type flags 2018-07-09 00:30:24 +08:00
rmd256.c crypto: rmd256 - use swap macro in rmd256_transform 2018-07-27 19:28:36 +08:00
rmd320.c crypto: rmd320 - use swap macro in rmd320_transform 2018-07-27 19:28:36 +08:00
rng.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
rsa-pkcs1pad.c crypto: rsa-pkcs1pad: Allow hash to be optional [ver #2] 2018-10-26 09:30:46 +01:00
rsa.c crypto: rsa - Remove unneeded error assignment 2018-04-21 00:58:37 +08:00
rsa_helper.c kbuild: rename *-asn1.[ch] to *.asn1.[ch] 2018-04-07 19:04:02 +09:00
rsaprivkey.asn1 crypto: rsa - Store rest of the private key components 2016-07-05 23:05:26 +08:00
rsapubkey.asn1 crypto: akcipher - Changes to asymmetric key API 2015-10-14 22:23:16 +08:00
salsa20_generic.c crypto: salsa20 - Revert "crypto: salsa20 - export generic helpers" 2018-05-31 00:13:57 +08:00
scatterwalk.c crypto: scatterwalk - remove 'chain' argument from scatterwalk_crypto_chain() 2018-08-03 18:06:03 +08:00
scompress.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
seed.c crypto: prefix module autoloading with "crypto-" 2014-11-24 22:43:57 +08:00
seqiv.c crypto: null - Remove VLA usage of skcipher 2018-09-28 12:46:08 +08:00
serpent_generic.c crypto: serpent - improve __serpent_setkey with UBSAN 2017-08-09 20:17:54 +08:00
sha1_generic.c crypto: shash - remove useless setting of type flags 2018-07-09 00:30:24 +08:00
sha3_generic.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux 2018-08-03 17:55:12 +08:00
sha256_generic.c crypto: shash - remove useless setting of type flags 2018-07-09 00:30:24 +08:00
sha512_generic.c crypto: shash - remove useless setting of type flags 2018-07-09 00:30:24 +08:00
shash.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
simd.c crypto: simd - correctly take reqsize of wrapped skcipher into account 2018-11-09 17:35:43 +08:00
skcipher.c crypto: user - clean up report structure copying 2018-11-09 17:41:39 +08:00
sm3_generic.c crypto: shash - remove useless setting of type flags 2018-07-09 00:30:24 +08:00
sm4_generic.c crypto: sm4 - export encrypt/decrypt routines to other drivers 2018-05-05 14:52:51 +08:00
streebog_generic.c crypto: streebog - add Streebog hash function 2018-11-16 14:09:40 +08:00
tcrypt.c crypto: streebog - add Streebog test vectors 2018-11-16 14:11:02 +08:00
tcrypt.h crypto: testmgr - update sm4 test vectors 2018-09-28 12:46:26 +08:00
tea.c crypto: add missing crypto module aliases 2015-01-13 22:29:11 +11:00
testmgr.c crypto: chacha - add XChaCha12 support 2018-11-20 14:26:55 +08:00
testmgr.h crypto: chacha - add XChaCha12 support 2018-11-20 14:26:55 +08:00
tgr192.c crypto: shash - remove useless setting of type flags 2018-07-09 00:30:24 +08:00
twofish_common.c crypto: replace FSF address with web source in license notices 2017-11-29 17:33:25 +11:00
twofish_generic.c crypto: replace FSF address with web source in license notices 2017-11-29 17:33:25 +11:00
vmac.c crypto: vmac - remove insecure version with hardcoded nonce 2018-07-01 21:00:44 +08:00
wp512.c crypto: shash - remove useless setting of type flags 2018-07-09 00:30:24 +08:00
xcbc.c crypto: xcbc - Remove VLA usage 2018-09-04 11:35:03 +08:00
xor.c kmemcheck: stop using GFP_NOTRACK and SLAB_NOTRACK 2017-11-15 18:21:04 -08:00
xts.c crypto: xts - Drop use of auxiliary buffer 2018-09-21 13:24:50 +08:00
zstd.c crypto: zstd - Add zstd support 2018-04-21 00:58:30 +08:00