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/*
* ChaCha20 256-bit cipher algorithm, RFC7539
*
* Copyright (C) 2015 Martin Willi
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*/
#include <linux/byteorder.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/scatterlist.h>
#include <asm/unaligned.h>
#include <linux/crypto.h>
#include <crypto/algapi.h>
#include <crypto/chacha.h>
#include <crypto/skcipher.h>
#include <sodium/crypto_stream_chacha20.h>
static struct skcipher_alg alg;
struct chacha20_tfm {
struct crypto_skcipher tfm;
u32 key[8];
};
static int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
unsigned int keysize)
{
struct chacha20_tfm *ctx =
container_of(tfm, struct chacha20_tfm, 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));
return 0;
}
static int crypto_chacha20_crypt(struct skcipher_request *req)
{
struct chacha20_tfm *ctx =
container_of(req->tfm, struct chacha20_tfm, tfm.base);
struct scatterlist *sg = req->src;
unsigned nbytes = req->cryptlen;
u32 iv[4];
int ret;
BUG_ON(req->src != req->dst);
memcpy(iv, req->iv, sizeof(iv));
while (1) {
ret = crypto_stream_chacha20_xor_ic(sg_virt(sg),
sg_virt(sg),
sg->length,
(void *) &iv[2],
iv[0] | ((u64) iv[1] << 32),
(void *) ctx->key);
BUG_ON(ret);
nbytes -= sg->length;
if (sg_is_last(sg))
break;
BUG_ON(sg->length % CHACHA_BLOCK_SIZE);
iv[0] += sg->length / CHACHA_BLOCK_SIZE;
sg = sg_next(sg);
};
BUG_ON(nbytes);
return 0;
}
static void *crypto_chacha20_alloc_tfm(void)
{
struct chacha20_tfm *tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
if (!tfm)
return NULL;
tfm->tfm.base.alg = &alg.base;
tfm->tfm.setkey = crypto_chacha20_setkey;
tfm->tfm.encrypt = crypto_chacha20_crypt;
tfm->tfm.decrypt = crypto_chacha20_crypt;
tfm->tfm.ivsize = CHACHA_IV_SIZE;
tfm->tfm.keysize = CHACHA_KEY_SIZE;
return tfm;
}
static struct skcipher_alg alg = {
.base.cra_name = "chacha20",
.base.alloc_tfm = crypto_chacha20_alloc_tfm,
};
__attribute__((constructor(110)))
static int chacha20_generic_mod_init(void)
{
return crypto_register_skcipher(&alg);
}
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