/*
   * CBC: Cipher Block Chaining mode
   *

   * Copyright (c) 2006-2016 Herbert Xu <herbert@gondor.apana.org.au>

   *
   * 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 <crypto/algapi.h>

  #include <crypto/cbc.h>

  #include <crypto/internal/skcipher.h>

  #include <linux/err.h>
  #include <linux/init.h>
  #include <linux/kernel.h>

  #include <linux/log2.h>

  #include <linux/module.h>

  #include <linux/slab.h>
  
  struct crypto_cbc_ctx {
  	struct crypto_cipher *child;

  };

  static int crypto_cbc_setkey(struct crypto_skcipher *parent, const u8 *key,

  			     unsigned int keylen)
  {

  	struct crypto_cbc_ctx *ctx = crypto_skcipher_ctx(parent);

  	struct crypto_cipher *child = ctx->child;
  	int err;
  
  	crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);

  	crypto_cipher_set_flags(child, crypto_skcipher_get_flags(parent) &

  				       CRYPTO_TFM_REQ_MASK);
  	err = crypto_cipher_setkey(child, key, keylen);

  	crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(child) &
  					  CRYPTO_TFM_RES_MASK);

  	return err;
  }

  static inline void crypto_cbc_encrypt_one(struct crypto_skcipher *tfm,
  					  const u8 *src, u8 *dst)
  {
  	struct crypto_cbc_ctx *ctx = crypto_skcipher_ctx(tfm);
  
  	crypto_cipher_encrypt_one(ctx->child, dst, src);
  }
  
  static int crypto_cbc_encrypt(struct skcipher_request *req)

  {

  	return crypto_cbc_encrypt_walk(req, crypto_cbc_encrypt_one);
  }

  static inline void crypto_cbc_decrypt_one(struct crypto_skcipher *tfm,
  					  const u8 *src, u8 *dst)
  {
  	struct crypto_cbc_ctx *ctx = crypto_skcipher_ctx(tfm);
  
  	crypto_cipher_decrypt_one(ctx->child, dst, src);
  }
  
  static int crypto_cbc_decrypt(struct skcipher_request *req)
  {
  	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  	struct skcipher_walk walk;

  	int err;

  	err = skcipher_walk_virt(&walk, req, false);

  	while (walk.nbytes) {
  		err = crypto_cbc_decrypt_blocks(&walk, tfm,
  						crypto_cbc_decrypt_one);
  		err = skcipher_walk_done(&walk, err);

  	}
  
  	return err;
  }

  static int crypto_cbc_init_tfm(struct crypto_skcipher *tfm)

  {

  	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
  	struct crypto_spawn *spawn = skcipher_instance_ctx(inst);
  	struct crypto_cbc_ctx *ctx = crypto_skcipher_ctx(tfm);

  	struct crypto_cipher *cipher;

  	cipher = crypto_spawn_cipher(spawn);
  	if (IS_ERR(cipher))
  		return PTR_ERR(cipher);

  	ctx->child = cipher;

  	return 0;
  }

  static void crypto_cbc_exit_tfm(struct crypto_skcipher *tfm)

  {

  	struct crypto_cbc_ctx *ctx = crypto_skcipher_ctx(tfm);

  	crypto_free_cipher(ctx->child);
  }

  static void crypto_cbc_free(struct skcipher_instance *inst)

  {

  	crypto_drop_skcipher(skcipher_instance_ctx(inst));
  	kfree(inst);
  }
  
  static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb)
  {
  	struct skcipher_instance *inst;

  	struct crypto_attr_type *algt;

  	struct crypto_spawn *spawn;

  	struct crypto_alg *alg;

  	u32 mask;

  	int err;

  	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER);

  	if (err)

  		return err;
  
  	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
  	if (!inst)
  		return -ENOMEM;

  	algt = crypto_get_attr_type(tb);
  	err = PTR_ERR(algt);
  	if (IS_ERR(algt))
  		goto err_free_inst;
  
  	mask = CRYPTO_ALG_TYPE_MASK |
  		crypto_requires_off(algt->type, algt->mask,
  				    CRYPTO_ALG_NEED_FALLBACK);
  
  	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, mask);

  	err = PTR_ERR(alg);

  	if (IS_ERR(alg))

  		goto err_free_inst;

  	spawn = skcipher_instance_ctx(inst);
  	err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst),
  				CRYPTO_ALG_TYPE_MASK);
  	crypto_mod_put(alg);
  	if (err)
  		goto err_free_inst;
  
  	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cbc", alg);
  	if (err)
  		goto err_drop_spawn;

  	err = -EINVAL;
  	if (!is_power_of_2(alg->cra_blocksize))
  		goto err_drop_spawn;

  	inst->alg.base.cra_priority = alg->cra_priority;
  	inst->alg.base.cra_blocksize = alg->cra_blocksize;
  	inst->alg.base.cra_alignmask = alg->cra_alignmask;

  	inst->alg.ivsize = alg->cra_blocksize;
  	inst->alg.min_keysize = alg->cra_cipher.cia_min_keysize;
  	inst->alg.max_keysize = alg->cra_cipher.cia_max_keysize;

  	inst->alg.base.cra_ctxsize = sizeof(struct crypto_cbc_ctx);

  	inst->alg.init = crypto_cbc_init_tfm;
  	inst->alg.exit = crypto_cbc_exit_tfm;

  	inst->alg.setkey = crypto_cbc_setkey;
  	inst->alg.encrypt = crypto_cbc_encrypt;
  	inst->alg.decrypt = crypto_cbc_decrypt;

  	inst->free = crypto_cbc_free;

  	err = skcipher_register_instance(tmpl, inst);
  	if (err)
  		goto err_drop_spawn;
  
  out:
  	return err;
  
  err_drop_spawn:
  	crypto_drop_spawn(spawn);
  err_free_inst:

  	kfree(inst);

  	goto out;

  }
  
  static struct crypto_template crypto_cbc_tmpl = {
  	.name = "cbc",

  	.create = crypto_cbc_create,

  	.module = THIS_MODULE,
  };
  
  static int __init crypto_cbc_module_init(void)
  {
  	return crypto_register_template(&crypto_cbc_tmpl);
  }
  
  static void __exit crypto_cbc_module_exit(void)
  {
  	crypto_unregister_template(&crypto_cbc_tmpl);
  }
  
  module_init(crypto_cbc_module_init);
  module_exit(crypto_cbc_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("CBC block cipher algorithm");

  MODULE_ALIAS_CRYPTO("cbc");