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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Fri, 8 Nov 2019 13:22:08 +0100
Subject: [PATCH] crypto: chacha - move existing library code into lib/crypto
commit 5fb8ef25803ef33e2eb60b626435828b937bed75 upstream.
Currently, our generic ChaCha implementation consists of a permute
function in lib/chacha.c that operates on the 64-byte ChaCha state
directly [and which is always included into the core kernel since it
is used by the /dev/random driver], and the crypto API plumbing to
expose it as a skcipher.
In order to support in-kernel users that need the ChaCha streamcipher
but have no need [or tolerance] for going through the abstractions of
the crypto API, let's expose the streamcipher bits via a library API
as well, in a way that permits the implementation to be superseded by
an architecture specific one if provided.
So move the streamcipher code into a separate module in lib/crypto,
and expose the init() and crypt() routines to users of the library.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
arch/arm/crypto/chacha-neon-glue.c | 2 +-
arch/arm64/crypto/chacha-neon-glue.c | 2 +-
arch/x86/crypto/chacha_glue.c | 2 +-
crypto/Kconfig | 1 +
crypto/chacha_generic.c | 60 ++--------------------
include/crypto/chacha.h | 77 ++++++++++++++++++++++------
include/crypto/internal/chacha.h | 53 +++++++++++++++++++
lib/Makefile | 3 +-
lib/crypto/Kconfig | 26 ++++++++++
lib/crypto/Makefile | 4 ++
lib/{ => crypto}/chacha.c | 20 ++++----
lib/crypto/libchacha.c | 35 +++++++++++++
12 files changed, 199 insertions(+), 86 deletions(-)
create mode 100644 include/crypto/internal/chacha.h
rename lib/{ => crypto}/chacha.c (88%)
create mode 100644 lib/crypto/libchacha.c
--- a/arch/arm/crypto/chacha-neon-glue.c
+++ b/arch/arm/crypto/chacha-neon-glue.c
@@ -20,7 +20,7 @@
*/
#include <crypto/algapi.h>
-#include <crypto/chacha.h>
+#include <crypto/internal/chacha.h>
#include <crypto/internal/simd.h>
#include <crypto/internal/skcipher.h>
#include <linux/kernel.h>
--- a/arch/arm64/crypto/chacha-neon-glue.c
+++ b/arch/arm64/crypto/chacha-neon-glue.c
@@ -20,7 +20,7 @@
*/
#include <crypto/algapi.h>
-#include <crypto/chacha.h>
+#include <crypto/internal/chacha.h>
#include <crypto/internal/simd.h>
#include <crypto/internal/skcipher.h>
#include <linux/kernel.h>
--- a/arch/x86/crypto/chacha_glue.c
+++ b/arch/x86/crypto/chacha_glue.c
@@ -7,7 +7,7 @@
*/
#include <crypto/algapi.h>
-#include <crypto/chacha.h>
+#include <crypto/internal/chacha.h>
#include <crypto/internal/simd.h>
#include <crypto/internal/skcipher.h>
#include <linux/kernel.h>
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -1393,6 +1393,7 @@ config CRYPTO_SALSA20
config CRYPTO_CHACHA20
tristate "ChaCha stream cipher algorithms"
+ select CRYPTO_LIB_CHACHA_GENERIC
select CRYPTO_BLKCIPHER
help
The ChaCha20, XChaCha20, and XChaCha12 stream cipher algorithms.
--- a/crypto/chacha_generic.c
+++ b/crypto/chacha_generic.c
@@ -8,29 +8,10 @@
#include <asm/unaligned.h>
#include <crypto/algapi.h>
-#include <crypto/chacha.h>
+#include <crypto/internal/chacha.h>
#include <crypto/internal/skcipher.h>
#include <linux/module.h>
-static void chacha_docrypt(u32 *state, u8 *dst, const u8 *src,
- unsigned int bytes, int nrounds)
-{
- /* aligned to potentially speed up crypto_xor() */
- u8 stream[CHACHA_BLOCK_SIZE] __aligned(sizeof(long));
-
- while (bytes >= CHACHA_BLOCK_SIZE) {
- chacha_block(state, stream, nrounds);
- crypto_xor_cpy(dst, src, stream, CHACHA_BLOCK_SIZE);
- bytes -= CHACHA_BLOCK_SIZE;
- dst += CHACHA_BLOCK_SIZE;
- src += CHACHA_BLOCK_SIZE;
- }
- if (bytes) {
- chacha_block(state, stream, nrounds);
- crypto_xor_cpy(dst, src, stream, bytes);
- }
-}
-
static int chacha_stream_xor(struct skcipher_request *req,
const struct chacha_ctx *ctx, const u8 *iv)
{
@@ -48,8 +29,8 @@ static int chacha_stream_xor(struct skci
if (nbytes < walk.total)
nbytes = round_down(nbytes, CHACHA_BLOCK_SIZE);
- chacha_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
- nbytes, ctx->nrounds);
+ chacha_crypt_generic(state, walk.dst.virt.addr,
+ walk.src.virt.addr, nbytes, ctx->nrounds);
err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
}
@@ -58,41 +39,10 @@ static int chacha_stream_xor(struct skci
void crypto_chacha_init(u32 *state, const struct chacha_ctx *ctx, const u8 *iv)
{
- state[0] = 0x61707865; /* "expa" */
- state[1] = 0x3320646e; /* "nd 3" */
- state[2] = 0x79622d32; /* "2-by" */
- state[3] = 0x6b206574; /* "te k" */
- state[4] = ctx->key[0];
- state[5] = ctx->key[1];
- state[6] = ctx->key[2];
- state[7] = ctx->key[3];
- state[8] = ctx->key[4];
- state[9] = ctx->key[5];
- state[10] = ctx->key[6];
- state[11] = ctx->key[7];
- state[12] = get_unaligned_le32(iv + 0);
- state[13] = get_unaligned_le32(iv + 4);
- state[14] = get_unaligned_le32(iv + 8);
- state[15] = get_unaligned_le32(iv + 12);
+ chacha_init_generic(state, ctx->key, iv);
}
EXPORT_SYMBOL_GPL(crypto_chacha_init);
-static int chacha_setkey(struct crypto_skcipher *tfm, const u8 *key,
- unsigned int keysize, int nrounds)
-{
- struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
- int i;
-
- if (keysize != CHACHA_KEY_SIZE)
- return -EINVAL;
-
- for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
- ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32));
-
- ctx->nrounds = nrounds;
- return 0;
-}
-
int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
unsigned int keysize)
{
@@ -126,7 +76,7 @@ int crypto_xchacha_crypt(struct skcipher
/* Compute the subkey given the original key and first 128 nonce bits */
crypto_chacha_init(state, ctx, req->iv);
- hchacha_block(state, subctx.key, ctx->nrounds);
+ hchacha_block_generic(state, subctx.key, ctx->nrounds);
subctx.nrounds = ctx->nrounds;
/* Build the real IV */
--- a/include/crypto/chacha.h
+++ b/include/crypto/chacha.h
@@ -15,9 +15,8 @@
#ifndef _CRYPTO_CHACHA_H
#define _CRYPTO_CHACHA_H
-#include <crypto/skcipher.h>
+#include <asm/unaligned.h>
#include <linux/types.h>
-#include <linux/crypto.h>
/* 32-bit stream position, then 96-bit nonce (RFC7539 convention) */
#define CHACHA_IV_SIZE 16
@@ -29,26 +28,70 @@
/* 192-bit nonce, then 64-bit stream position */
#define XCHACHA_IV_SIZE 32
-struct chacha_ctx {
- u32 key[8];
- int nrounds;
-};
-
-void chacha_block(u32 *state, u8 *stream, int nrounds);
+void chacha_block_generic(u32 *state, u8 *stream, int nrounds);
static inline void chacha20_block(u32 *state, u8 *stream)
{
- chacha_block(state, stream, 20);
+ chacha_block_generic(state, stream, 20);
}
-void hchacha_block(const u32 *in, u32 *out, int nrounds);
-void crypto_chacha_init(u32 *state, const struct chacha_ctx *ctx, const u8 *iv);
+void hchacha_block_arch(const u32 *state, u32 *out, int nrounds);
+void hchacha_block_generic(const u32 *state, u32 *out, int nrounds);
+
+static inline void hchacha_block(const u32 *state, u32 *out, int nrounds)
+{
+ if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
+ hchacha_block_arch(state, out, nrounds);
+ else
+ hchacha_block_generic(state, out, nrounds);
+}
-int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
- unsigned int keysize);
-int crypto_chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key,
- unsigned int keysize);
+void chacha_init_arch(u32 *state, const u32 *key, const u8 *iv);
+static inline void chacha_init_generic(u32 *state, const u32 *key, const u8 *iv)
+{
+ state[0] = 0x61707865; /* "expa" */
+ state[1] = 0x3320646e; /* "nd 3" */
+ state[2] = 0x79622d32; /* "2-by" */
+ state[3] = 0x6b206574; /* "te k" */
+ state[4] = key[0];
+ state[5] = key[1];
+ state[6] = key[2];
+ state[7] = key[3];
+ state[8] = key[4];
+ state[9] = key[5];
+ state[10] = key[6];
+ state[11] = key[7];
+ state[12] = get_unaligned_le32(iv + 0);
+ state[13] = get_unaligned_le32(iv + 4);
+ state[14] = get_unaligned_le32(iv + 8);
+ state[15] = get_unaligned_le32(iv + 12);
+}
-int crypto_chacha_crypt(struct skcipher_request *req);
-int crypto_xchacha_crypt(struct skcipher_request *req);
+static inline void chacha_init(u32 *state, const u32 *key, const u8 *iv)
+{
+ if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
+ chacha_init_arch(state, key, iv);
+ else
+ chacha_init_generic(state, key, iv);
+}
+
+void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src,
+ unsigned int bytes, int nrounds);
+void chacha_crypt_generic(u32 *state, u8 *dst, const u8 *src,
+ unsigned int bytes, int nrounds);
+
+static inline void chacha_crypt(u32 *state, u8 *dst, const u8 *src,
+ unsigned int bytes, int nrounds)
+{
+ if (IS_ENABLED(CONFIG_CRYPTO_ARCH_HAVE_LIB_CHACHA))
+ chacha_crypt_arch(state, dst, src, bytes, nrounds);
+ else
+ chacha_crypt_generic(state, dst, src, bytes, nrounds);
+}
+
+static inline void chacha20_crypt(u32 *state, u8 *dst, const u8 *src,
+ unsigned int bytes)
+{
+ chacha_crypt(state, dst, src, bytes, 20);
+}
#endif /* _CRYPTO_CHACHA_H */
--- /dev/null
+++ b/include/crypto/internal/chacha.h
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _CRYPTO_INTERNAL_CHACHA_H
+#define _CRYPTO_INTERNAL_CHACHA_H
+
+#include <crypto/chacha.h>
+#include <crypto/internal/skcipher.h>
+#include <linux/crypto.h>
+
+struct chacha_ctx {
+ u32 key[8];
+ int nrounds;
+};
+
+void crypto_chacha_init(u32 *state, const struct chacha_ctx *ctx, const u8 *iv);
+
+static inline int chacha_setkey(struct crypto_skcipher *tfm, const u8 *key,
+ unsigned int keysize, int nrounds)
+{
+ struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
+ int i;
+
+ if (keysize != CHACHA_KEY_SIZE)
+ return -EINVAL;
+
+ for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
+ ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32));
+
+ ctx->nrounds = nrounds;
+ return 0;
+}
+
+static inline int chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
+ unsigned int keysize)
+{
+ return chacha_setkey(tfm, key, keysize, 20);
+}
+
+static int inline chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key,
+ unsigned int keysize)
+{
+ return chacha_setkey(tfm, key, keysize, 12);
+}
+
+int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
+ unsigned int keysize);
+int crypto_chacha12_setkey(struct crypto_skcipher *tfm, const u8 *key,
+ unsigned int keysize);
+
+int crypto_chacha_crypt(struct skcipher_request *req);
+int crypto_xchacha_crypt(struct skcipher_request *req);
+
+#endif /* _CRYPTO_CHACHA_H */
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -26,8 +26,7 @@ endif
lib-y := ctype.o string.o vsprintf.o cmdline.o \
rbtree.o radix-tree.o timerqueue.o xarray.o \
- idr.o extable.o \
- sha1.o chacha.o irq_regs.o argv_split.o \
+ idr.o extable.o sha1.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 \
--- a/lib/crypto/Kconfig
+++ b/lib/crypto/Kconfig
@@ -8,6 +8,32 @@ config CRYPTO_LIB_AES
config CRYPTO_LIB_ARC4
tristate
+config CRYPTO_ARCH_HAVE_LIB_CHACHA
+ tristate
+ help
+ Declares whether the architecture provides an arch-specific
+ accelerated implementation of the ChaCha library interface,
+ either builtin or as a module.
+
+config CRYPTO_LIB_CHACHA_GENERIC
+ tristate
+ select CRYPTO_ALGAPI
+ help
+ This symbol can be depended upon by arch implementations of the
+ ChaCha library interface that require the generic code as a
+ fallback, e.g., for SIMD implementations. If no arch specific
+ implementation is enabled, this implementation serves the users
+ of CRYPTO_LIB_CHACHA.
+
+config CRYPTO_LIB_CHACHA
+ tristate "ChaCha library interface"
+ depends on CRYPTO_ARCH_HAVE_LIB_CHACHA || !CRYPTO_ARCH_HAVE_LIB_CHACHA
+ select CRYPTO_LIB_CHACHA_GENERIC if CRYPTO_ARCH_HAVE_LIB_CHACHA=n
+ help
+ Enable the ChaCha library interface. This interface may be fulfilled
+ by either the generic implementation or an arch-specific one, if one
+ is available and enabled.
+
config CRYPTO_LIB_DES
tristate
--- a/lib/crypto/Makefile
+++ b/lib/crypto/Makefile
@@ -1,5 +1,9 @@
# SPDX-License-Identifier: GPL-2.0
+# chacha is used by the /dev/random driver which is always builtin
+obj-y += chacha.o
+obj-$(CONFIG_CRYPTO_LIB_CHACHA_GENERIC) += libchacha.o
+
obj-$(CONFIG_CRYPTO_LIB_AES) += libaes.o
libaes-y := aes.o
--- a/lib/chacha.c
+++ /dev/null
@@ -1,113 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * The "hash function" used as the core of the ChaCha stream cipher (RFC7539)
- *
- * Copyright (C) 2015 Martin Willi
- */
-
-#include <linux/kernel.h>
-#include <linux/export.h>
-#include <linux/bitops.h>
-#include <linux/cryptohash.h>
-#include <asm/unaligned.h>
-#include <crypto/chacha.h>
-
-static void chacha_permute(u32 *x, int nrounds)
-{
- int i;
-
- /* whitelist the allowed round counts */
- WARN_ON_ONCE(nrounds != 20 && nrounds != 12);
-
- 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);
- x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 16);
-
- x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 12);
- x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 12);
- x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 12);
- x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 12);
-
- x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 8);
- x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 8);
- x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 8);
- x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 8);
-
- x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 7);
- x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 7);
- x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 7);
- x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 7);
-
- x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 16);
- x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 16);
- x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 16);
- x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 16);
-
- x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 12);
- x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 12);
- x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 12);
- x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 12);
-
- x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 8);
- x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 8);
- x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 8);
- x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 8);
-
- x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 7);
- x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 7);
- x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 7);
- x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 7);
- }
-}
-
-/**
- * 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 (20 or 12; 20 is recommended)
- *
- * 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 chacha_block(u32 *state, u8 *stream, int nrounds)
-{
- u32 x[16];
- int i;
-
- memcpy(x, state, 64);
-
- 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(chacha_block);
-
-/**
- * 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 (20 or 12; 20 is recommended)
- *
- * 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 hchacha_block(const u32 *in, u32 *out, int nrounds)
-{
- u32 x[16];
-
- memcpy(x, in, 64);
-
- chacha_permute(x, nrounds);
-
- memcpy(&out[0], &x[0], 16);
- memcpy(&out[4], &x[12], 16);
-}
-EXPORT_SYMBOL(hchacha_block);
--- /dev/null
+++ b/lib/crypto/chacha.c
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * The "hash function" used as the core of the ChaCha stream cipher (RFC7539)
+ *
+ * Copyright (C) 2015 Martin Willi
+ */
+
+#include <linux/bug.h>
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/bitops.h>
+#include <linux/string.h>
+#include <linux/cryptohash.h>
+#include <asm/unaligned.h>
+#include <crypto/chacha.h>
+
+static void chacha_permute(u32 *x, int nrounds)
+{
+ int i;
+
+ /* whitelist the allowed round counts */
+ WARN_ON_ONCE(nrounds != 20 && nrounds != 12);
+
+ 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);
+ x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 16);
+
+ x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 12);
+ x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 12);
+ x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 12);
+ x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 12);
+
+ x[0] += x[4]; x[12] = rol32(x[12] ^ x[0], 8);
+ x[1] += x[5]; x[13] = rol32(x[13] ^ x[1], 8);
+ x[2] += x[6]; x[14] = rol32(x[14] ^ x[2], 8);
+ x[3] += x[7]; x[15] = rol32(x[15] ^ x[3], 8);
+
+ x[8] += x[12]; x[4] = rol32(x[4] ^ x[8], 7);
+ x[9] += x[13]; x[5] = rol32(x[5] ^ x[9], 7);
+ x[10] += x[14]; x[6] = rol32(x[6] ^ x[10], 7);
+ x[11] += x[15]; x[7] = rol32(x[7] ^ x[11], 7);
+
+ x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 16);
+ x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 16);
+ x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 16);
+ x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 16);
+
+ x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 12);
+ x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 12);
+ x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 12);
+ x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 12);
+
+ x[0] += x[5]; x[15] = rol32(x[15] ^ x[0], 8);
+ x[1] += x[6]; x[12] = rol32(x[12] ^ x[1], 8);
+ x[2] += x[7]; x[13] = rol32(x[13] ^ x[2], 8);
+ x[3] += x[4]; x[14] = rol32(x[14] ^ x[3], 8);
+
+ x[10] += x[15]; x[5] = rol32(x[5] ^ x[10], 7);
+ x[11] += x[12]; x[6] = rol32(x[6] ^ x[11], 7);
+ x[8] += x[13]; x[7] = rol32(x[7] ^ x[8], 7);
+ x[9] += x[14]; x[4] = rol32(x[4] ^ x[9], 7);
+ }
+}
+
+/**
+ * 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 (20 or 12; 20 is recommended)
+ *
+ * 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 chacha_block_generic(u32 *state, u8 *stream, int nrounds)
+{
+ u32 x[16];
+ int i;
+
+ memcpy(x, state, 64);
+
+ 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(chacha_block_generic);
+
+/**
+ * hchacha_block_generic - abbreviated ChaCha core, for XChaCha
+ * @state: input state matrix (16 32-bit words)
+ * @out: output (8 32-bit words)
+ * @nrounds: number of rounds (20 or 12; 20 is recommended)
+ *
+ * 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 hchacha_block_generic(const u32 *state, u32 *stream, int nrounds)
+{
+ u32 x[16];
+
+ memcpy(x, state, 64);
+
+ chacha_permute(x, nrounds);
+
+ memcpy(&stream[0], &x[0], 16);
+ memcpy(&stream[4], &x[12], 16);
+}
+EXPORT_SYMBOL(hchacha_block_generic);
--- /dev/null
+++ b/lib/crypto/libchacha.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * The ChaCha stream cipher (RFC7539)
+ *
+ * Copyright (C) 2015 Martin Willi
+ */
+
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/module.h>
+
+#include <crypto/algapi.h> // for crypto_xor_cpy
+#include <crypto/chacha.h>
+
+void chacha_crypt_generic(u32 *state, u8 *dst, const u8 *src,
+ unsigned int bytes, int nrounds)
+{
+ /* aligned to potentially speed up crypto_xor() */
+ u8 stream[CHACHA_BLOCK_SIZE] __aligned(sizeof(long));
+
+ while (bytes >= CHACHA_BLOCK_SIZE) {
+ chacha_block_generic(state, stream, nrounds);
+ crypto_xor_cpy(dst, src, stream, CHACHA_BLOCK_SIZE);
+ bytes -= CHACHA_BLOCK_SIZE;
+ dst += CHACHA_BLOCK_SIZE;
+ src += CHACHA_BLOCK_SIZE;
+ }
+ if (bytes) {
+ chacha_block_generic(state, stream, nrounds);
+ crypto_xor_cpy(dst, src, stream, bytes);
+ }
+}
+EXPORT_SYMBOL(chacha_crypt_generic);
+
+MODULE_LICENSE("GPL");
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