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crypto: chacha - move existing library code into lib/crypto

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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as well, in a way that permits the implementation to be superseded by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>
This commit is contained in:
Ard Biesheuvel
2019-11-08 13:22:08 +01:00
committed by Herbert Xu
parent 746b2e024c
commit 5fb8ef2580
12 changed files with 199 additions and 86 deletions
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35
lib/crypto/libchacha.c Normal file
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// 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");