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authorEric Biggers <ebiggers@google.com>2018-11-16 17:26:21 -0800
committerHerbert Xu <herbert@gondor.apana.org.au>2018-11-20 14:26:55 +0800
commit1ca1b917940c24ca3d1f490118c5474168622953 (patch)
tree26cde5a85d0792a8dd709a6f5316f76af8801a35 /lib
parentde61d7ae5d3789dcba3749a418f76613fbee8414 (diff)
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crypto: chacha20-generic - refactor to allow varying number of rounds
In preparation for adding XChaCha12 support, rename/refactor chacha20-generic to support different numbers of rounds. The justification for needing XChaCha12 support is explained in more detail in the patch "crypto: chacha - add XChaCha12 support". The only difference between ChaCha{8,12,20} are the number of rounds itself; all other parts of the algorithm are the same. Therefore, remove the "20" from all definitions, structures, functions, files, etc. that will be shared by all ChaCha versions. Also make ->setkey() store the round count in the chacha_ctx (previously chacha20_ctx). The generic code then passes the round count through to chacha_block(). There will be a ->setkey() function for each explicitly allowed round count; the encrypt/decrypt functions will be the same. I decided not to do it the opposite way (same ->setkey() function for all round counts, with different encrypt/decrypt functions) because that would have required more boilerplate code in architecture-specific implementations of ChaCha and XChaCha. 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>
Diffstat (limited to 'lib')
-rw-r--r--lib/Makefile2
-rw-r--r--lib/chacha.c (renamed from lib/chacha20.c)43
2 files changed, 25 insertions, 20 deletions
diff --git a/lib/Makefile b/lib/Makefile
index db06d1237898..4c2b6fc5cde9 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -20,7 +20,7 @@ KCOV_INSTRUMENT_dynamic_debug.o := n
lib-y := ctype.o string.o vsprintf.o cmdline.o \
rbtree.o radix-tree.o timerqueue.o xarray.o \
idr.o int_sqrt.o extable.o \
- sha1.o chacha20.o irq_regs.o argv_split.o \
+ sha1.o chacha.o irq_regs.o argv_split.o \
flex_proportions.o ratelimit.o show_mem.o \
is_single_threaded.o plist.o decompress.o kobject_uevent.o \
earlycpio.o seq_buf.o siphash.o dec_and_lock.o \
diff --git a/lib/chacha20.c b/lib/chacha.c
index 6a484e16171d..1bdc688c18df 100644
--- a/lib/chacha20.c
+++ b/lib/chacha.c
@@ -1,5 +1,5 @@
/*
- * The "hash function" used as the core of the ChaCha20 stream cipher (RFC7539)
+ * The "hash function" used as the core of the ChaCha stream cipher (RFC7539)
*
* Copyright (C) 2015 Martin Willi
*
@@ -14,13 +14,16 @@
#include <linux/bitops.h>
#include <linux/cryptohash.h>
#include <asm/unaligned.h>
-#include <crypto/chacha20.h>
+#include <crypto/chacha.h>
-static void chacha20_permute(u32 *x)
+static void chacha_permute(u32 *x, int nrounds)
{
int i;
- for (i = 0; i < 20; i += 2) {
+ /* whitelist the allowed round counts */
+ WARN_ON_ONCE(nrounds != 20);
+
+ for (i = 0; i < nrounds; i += 2) {
x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 16);
x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 16);
x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 16);
@@ -64,49 +67,51 @@ static void chacha20_permute(u32 *x)
}
/**
- * chacha20_block - generate one keystream block and increment block counter
+ * chacha_block - generate one keystream block and increment block counter
* @state: input state matrix (16 32-bit words)
* @stream: output keystream block (64 bytes)
+ * @nrounds: number of rounds (currently must be 20)
*
- * This is the ChaCha20 core, a function from 64-byte strings to 64-byte
- * strings. The caller has already converted the endianness of the input. This
- * function also handles incrementing the block counter in the input matrix.
+ * This is the ChaCha core, a function from 64-byte strings to 64-byte strings.
+ * The caller has already converted the endianness of the input. This function
+ * also handles incrementing the block counter in the input matrix.
*/
-void chacha20_block(u32 *state, u8 *stream)
+void chacha_block(u32 *state, u8 *stream, int nrounds)
{
u32 x[16];
int i;
memcpy(x, state, 64);
- chacha20_permute(x);
+ chacha_permute(x, nrounds);
for (i = 0; i < ARRAY_SIZE(x); i++)
put_unaligned_le32(x[i] + state[i], &stream[i * sizeof(u32)]);
state[12]++;
}
-EXPORT_SYMBOL(chacha20_block);
+EXPORT_SYMBOL(chacha_block);
/**
- * hchacha20_block - abbreviated ChaCha20 core, for XChaCha20
+ * hchacha_block - abbreviated ChaCha core, for XChaCha
* @in: input state matrix (16 32-bit words)
* @out: output (8 32-bit words)
+ * @nrounds: number of rounds (currently must be 20)
*
- * HChaCha20 is the ChaCha equivalent of HSalsa20 and is an intermediate step
- * towards XChaCha20 (see https://cr.yp.to/snuffle/xsalsa-20081128.pdf).
- * HChaCha20 skips the final addition of the initial state, and outputs only
- * certain words of the state. It should not be used for streaming directly.
+ * HChaCha is the ChaCha equivalent of HSalsa and is an intermediate step
+ * towards XChaCha (see https://cr.yp.to/snuffle/xsalsa-20081128.pdf). HChaCha
+ * skips the final addition of the initial state, and outputs only certain words
+ * of the state. It should not be used for streaming directly.
*/
-void hchacha20_block(const u32 *in, u32 *out)
+void hchacha_block(const u32 *in, u32 *out, int nrounds)
{
u32 x[16];
memcpy(x, in, 64);
- chacha20_permute(x);
+ chacha_permute(x, nrounds);
memcpy(&out[0], &x[0], 16);
memcpy(&out[4], &x[12], 16);
}
-EXPORT_SYMBOL(hchacha20_block);
+EXPORT_SYMBOL(hchacha_block);