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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Crypto API wrappers for the ChaCha20, XChaCha20, and XChaCha12 stream ciphers
*
* Copyright (C) 2015 Martin Willi
* Copyright (C) 2018 Google LLC
*/
#include <linux/unaligned.h>
#include <crypto/algapi.h>
#include <crypto/chacha.h>
#include <crypto/internal/skcipher.h>
#include <linux/module.h>
struct chacha_ctx {
u32 key[8];
int nrounds;
};
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;
}
static int chacha20_setkey(struct crypto_skcipher *tfm,
const u8 *key, unsigned int keysize)
{
return chacha_setkey(tfm, key, keysize, 20);
}
static int chacha12_setkey(struct crypto_skcipher *tfm,
const u8 *key, unsigned int keysize)
{
return chacha_setkey(tfm, key, keysize, 12);
}
static int chacha_stream_xor(struct skcipher_request *req,
const struct chacha_ctx *ctx,
const u8 iv[CHACHA_IV_SIZE])
{
struct skcipher_walk walk;
struct chacha_state state;
int err;
err = skcipher_walk_virt(&walk, req, false);
chacha_init(&state, ctx->key, iv);
while (walk.nbytes > 0) {
unsigned int nbytes = walk.nbytes;
if (nbytes < walk.total)
nbytes = round_down(nbytes, CHACHA_BLOCK_SIZE);
chacha_crypt(&state, walk.dst.virt.addr, walk.src.virt.addr,
nbytes, ctx->nrounds);
err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
}
return err;
}
static int crypto_chacha_crypt(struct skcipher_request *req)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
const struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
return chacha_stream_xor(req, ctx, req->iv);
}
static int crypto_xchacha_crypt(struct skcipher_request *req)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
const struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
struct chacha_ctx subctx;
struct chacha_state state;
u8 real_iv[16];
/* Compute the subkey given the original key and first 128 nonce bits */
chacha_init(&state, ctx->key, req->iv);
hchacha_block(&state, subctx.key, ctx->nrounds);
subctx.nrounds = ctx->nrounds;
/* Build the real IV */
memcpy(&real_iv[0], req->iv + 24, 8); /* stream position */
memcpy(&real_iv[8], req->iv + 16, 8); /* remaining 64 nonce bits */
/* Generate the stream and XOR it with the data */
return chacha_stream_xor(req, &subctx, real_iv);
}
static struct skcipher_alg algs[] = {
{
.base.cra_name = "chacha20",
.base.cra_driver_name = "chacha20-lib",
.base.cra_priority = 300,
.base.cra_blocksize = 1,
.base.cra_ctxsize = sizeof(struct chacha_ctx),
.base.cra_module = THIS_MODULE,
.min_keysize = CHACHA_KEY_SIZE,
.max_keysize = CHACHA_KEY_SIZE,
.ivsize = CHACHA_IV_SIZE,
.chunksize = CHACHA_BLOCK_SIZE,
.setkey = chacha20_setkey,
.encrypt = crypto_chacha_crypt,
.decrypt = crypto_chacha_crypt,
},
{
.base.cra_name = "xchacha20",
.base.cra_driver_name = "xchacha20-lib",
.base.cra_priority = 300,
.base.cra_blocksize = 1,
.base.cra_ctxsize = sizeof(struct chacha_ctx),
.base.cra_module = THIS_MODULE,
.min_keysize = CHACHA_KEY_SIZE,
.max_keysize = CHACHA_KEY_SIZE,
.ivsize = XCHACHA_IV_SIZE,
.chunksize = CHACHA_BLOCK_SIZE,
.setkey = chacha20_setkey,
.encrypt = crypto_xchacha_crypt,
.decrypt = crypto_xchacha_crypt,
},
{
.base.cra_name = "xchacha12",
.base.cra_driver_name = "xchacha12-lib",
.base.cra_priority = 300,
.base.cra_blocksize = 1,
.base.cra_ctxsize = sizeof(struct chacha_ctx),
.base.cra_module = THIS_MODULE,
.min_keysize = CHACHA_KEY_SIZE,
.max_keysize = CHACHA_KEY_SIZE,
.ivsize = XCHACHA_IV_SIZE,
.chunksize = CHACHA_BLOCK_SIZE,
.setkey = chacha12_setkey,
.encrypt = crypto_xchacha_crypt,
.decrypt = crypto_xchacha_crypt,
}
};
static int __init crypto_chacha_mod_init(void)
{
return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
}
static void __exit crypto_chacha_mod_fini(void)
{
crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
}
module_init(crypto_chacha_mod_init);
module_exit(crypto_chacha_mod_fini);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
MODULE_DESCRIPTION("Crypto API wrappers for the ChaCha20, XChaCha20, and XChaCha12 stream ciphers");
MODULE_ALIAS_CRYPTO("chacha20");
MODULE_ALIAS_CRYPTO("chacha20-lib");
MODULE_ALIAS_CRYPTO("xchacha20");
MODULE_ALIAS_CRYPTO("xchacha20-lib");
MODULE_ALIAS_CRYPTO("xchacha12");
MODULE_ALIAS_CRYPTO("xchacha12-lib");
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