crypto: blake2b - add blake2b generic implementation

The patch brings support of several BLAKE2 variants (2b with various
digest lengths).  The keyed digest is supported, using tfm->setkey call.
The in-tree user will be btrfs (for checksumming), we're going to use
the BLAKE2b-256 variant.

The code is reference implementation taken from the official sources and
modified in terms of kernel coding style (whitespace, comments, uintXX_t
-> uXX types, removed unused prototypes and #ifdefs, removed testing
code, changed secure_zero_memory -> memzero_explicit, used own helpers
for unaligned reads/writes and rotations).

Further changes removed sanity checks of key length or output size,
these values are verified in the crypto API callbacks or hardcoded in
shash_alg and not exposed to users.

Signed-off-by: David Sterba <[email protected]>
Signed-off-by: Herbert Xu <[email protected]>

crypto/Kconfig

@@ -639,6 +639,23 @@ config CRYPTO_XXHASH
 	  xxHash non-cryptographic hash algorithm. Extremely fast, working at
 	  speeds close to RAM limits.
 
+config CRYPTO_BLAKE2B
+	tristate "BLAKE2b digest algorithm"
+	select CRYPTO_HASH
+	help
+	  Implementation of cryptographic hash function BLAKE2b (or just BLAKE2),
+	  optimized for 64bit platforms and can produce digests of any size
+	  between 1 to 64.  The keyed hash is also implemented.
+
+	  This module provides the following algorithms:
+
+	  - blake2b-160
+	  - blake2b-256
+	  - blake2b-384
+	  - blake2b-512
+
+	  See https://blake2.net for further information.
+
 config CRYPTO_CRCT10DIF
 	tristate "CRCT10DIF algorithm"
 	select CRYPTO_HASH

crypto/Makefile

@@ -74,6 +74,7 @@ obj-$(CONFIG_CRYPTO_STREEBOG) += streebog_generic.o
 obj-$(CONFIG_CRYPTO_WP512) += wp512.o
 CFLAGS_wp512.o := $(call cc-option,-fno-schedule-insns)  # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79149
 obj-$(CONFIG_CRYPTO_TGR192) += tgr192.o
+obj-$(CONFIG_CRYPTO_BLAKE2B) += blake2b_generic.o
 obj-$(CONFIG_CRYPTO_GF128MUL) += gf128mul.o
 obj-$(CONFIG_CRYPTO_ECB) += ecb.o
 obj-$(CONFIG_CRYPTO_CBC) += cbc.o