// SPDX-License-Identifier: GPL-2.0-or-later

  /*

   * ChaCha and XChaCha stream ciphers, including ChaCha20 (RFC7539)

   *
   * Copyright (C) 2015 Martin Willi

   * Copyright (C) 2018 Google LLC

   */

  #include <asm/unaligned.h>

  #include <crypto/algapi.h>

  #include <crypto/internal/chacha.h>

  #include <crypto/internal/skcipher.h>
  #include <linux/module.h>

  static int chacha_stream_xor(struct skcipher_request *req,

  			     const struct chacha_ctx *ctx, const u8 *iv)

  {
  	struct skcipher_walk walk;
  	u32 state[16];
  	int err;
  
  	err = skcipher_walk_virt(&walk, req, false);

  	chacha_init_generic(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_generic(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);

  	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);

  	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
  	struct chacha_ctx subctx;

  	u32 state[16];
  	u8 real_iv[16];

  	/* Compute the subkey given the original key and first 128 nonce bits */

  	chacha_init_generic(state, ctx->key, req->iv);

  	hchacha_block_generic(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-generic",
  		.base.cra_priority	= 100,
  		.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-generic",
  		.base.cra_priority	= 100,
  		.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-generic",
  		.base.cra_priority	= 100,
  		.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 chacha_generic_mod_init(void)

  {

  	return crypto_register_skciphers(algs, ARRAY_SIZE(algs));

  }

  static void __exit chacha_generic_mod_fini(void)

  {

  	crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));

  }

  subsys_initcall(chacha_generic_mod_init);

  module_exit(chacha_generic_mod_fini);

  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");

  MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (generic)");

  MODULE_ALIAS_CRYPTO("chacha20");
  MODULE_ALIAS_CRYPTO("chacha20-generic");

  MODULE_ALIAS_CRYPTO("xchacha20");
  MODULE_ALIAS_CRYPTO("xchacha20-generic");

  MODULE_ALIAS_CRYPTO("xchacha12");
  MODULE_ALIAS_CRYPTO("xchacha12-generic");