/*
   * PCBC: Propagating Cipher Block Chaining mode
   *
   * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * Derived from cbc.c
   * - Copyright (c) 2006 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/internal/skcipher.h>

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

  #include <linux/slab.h>

  #include <linux/compiler.h>

  
  struct crypto_pcbc_ctx {
  	struct crypto_cipher *child;

  };

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

  			      unsigned int keylen)
  {

  	struct crypto_pcbc_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 int crypto_pcbc_encrypt_segment(struct skcipher_request *req,
  				       struct skcipher_walk *walk,

  				       struct crypto_cipher *tfm)

  {

  	int bsize = crypto_cipher_blocksize(tfm);
  	unsigned int nbytes = walk->nbytes;
  	u8 *src = walk->src.virt.addr;
  	u8 *dst = walk->dst.virt.addr;

  	u8 * const iv = walk->iv;

  
  	do {

  		crypto_xor(iv, src, bsize);

  		crypto_cipher_encrypt_one(tfm, dst, iv);

  		crypto_xor_cpy(iv, dst, src, bsize);

  
  		src += bsize;
  		dst += bsize;
  	} while ((nbytes -= bsize) >= bsize);
  
  	return nbytes;
  }

  static int crypto_pcbc_encrypt_inplace(struct skcipher_request *req,
  				       struct skcipher_walk *walk,

  				       struct crypto_cipher *tfm)

  {

  	int bsize = crypto_cipher_blocksize(tfm);
  	unsigned int nbytes = walk->nbytes;
  	u8 *src = walk->src.virt.addr;

  	u8 * const iv = walk->iv;

  	u8 tmpbuf[MAX_CIPHER_BLOCKSIZE];

  
  	do {
  		memcpy(tmpbuf, src, bsize);

  		crypto_xor(iv, src, bsize);

  		crypto_cipher_encrypt_one(tfm, src, iv);

  		crypto_xor_cpy(iv, tmpbuf, src, bsize);

  
  		src += bsize;
  	} while ((nbytes -= bsize) >= bsize);

  	return nbytes;
  }

  static int crypto_pcbc_encrypt(struct skcipher_request *req)

  {

  	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  	struct crypto_pcbc_ctx *ctx = crypto_skcipher_ctx(tfm);

  	struct crypto_cipher *child = ctx->child;

  	struct skcipher_walk walk;
  	unsigned int nbytes;

  	int err;

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

  
  	while ((nbytes = walk.nbytes)) {
  		if (walk.src.virt.addr == walk.dst.virt.addr)

  			nbytes = crypto_pcbc_encrypt_inplace(req, &walk,

  							     child);

  		else

  			nbytes = crypto_pcbc_encrypt_segment(req, &walk,

  							     child);

  		err = skcipher_walk_done(&walk, nbytes);

  	}
  
  	return err;
  }

  static int crypto_pcbc_decrypt_segment(struct skcipher_request *req,
  				       struct skcipher_walk *walk,

  				       struct crypto_cipher *tfm)

  {

  	int bsize = crypto_cipher_blocksize(tfm);
  	unsigned int nbytes = walk->nbytes;
  	u8 *src = walk->src.virt.addr;
  	u8 *dst = walk->dst.virt.addr;

  	u8 * const iv = walk->iv;

  
  	do {

  		crypto_cipher_decrypt_one(tfm, dst, src);

  		crypto_xor(dst, iv, bsize);

  		crypto_xor_cpy(iv, dst, src, bsize);

  
  		src += bsize;
  		dst += bsize;
  	} while ((nbytes -= bsize) >= bsize);

  	return nbytes;
  }

  static int crypto_pcbc_decrypt_inplace(struct skcipher_request *req,
  				       struct skcipher_walk *walk,

  				       struct crypto_cipher *tfm)

  {

  	int bsize = crypto_cipher_blocksize(tfm);
  	unsigned int nbytes = walk->nbytes;
  	u8 *src = walk->src.virt.addr;

  	u8 * const iv = walk->iv;

  	u8 tmpbuf[MAX_CIPHER_BLOCKSIZE] __aligned(__alignof__(u32));

  
  	do {
  		memcpy(tmpbuf, src, bsize);

  		crypto_cipher_decrypt_one(tfm, src, src);

  		crypto_xor(src, iv, bsize);

  		crypto_xor_cpy(iv, src, tmpbuf, bsize);

  
  		src += bsize;
  	} while ((nbytes -= bsize) >= bsize);

  	return nbytes;
  }

  static int crypto_pcbc_decrypt(struct skcipher_request *req)

  {

  	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  	struct crypto_pcbc_ctx *ctx = crypto_skcipher_ctx(tfm);

  	struct crypto_cipher *child = ctx->child;

  	struct skcipher_walk walk;
  	unsigned int nbytes;

  	int err;

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

  
  	while ((nbytes = walk.nbytes)) {
  		if (walk.src.virt.addr == walk.dst.virt.addr)

  			nbytes = crypto_pcbc_decrypt_inplace(req, &walk,

  							     child);

  		else

  			nbytes = crypto_pcbc_decrypt_segment(req, &walk,

  							     child);

  		err = skcipher_walk_done(&walk, nbytes);

  	}
  
  	return err;
  }

  static int crypto_pcbc_init_tfm(struct crypto_skcipher *tfm)

  {

  	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
  	struct crypto_spawn *spawn = skcipher_instance_ctx(inst);
  	struct crypto_pcbc_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_pcbc_exit_tfm(struct crypto_skcipher *tfm)

  {

  	struct crypto_pcbc_ctx *ctx = crypto_skcipher_ctx(tfm);

  	crypto_free_cipher(ctx->child);
  }

  static void crypto_pcbc_free(struct skcipher_instance *inst)
  {
  	crypto_drop_skcipher(skcipher_instance_ctx(inst));
  	kfree(inst);
  }
  
  static int crypto_pcbc_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;

  	int err;

  	algt = crypto_get_attr_type(tb);
  	if (IS_ERR(algt))
  		return PTR_ERR(algt);
  
  	if (((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask) &
  	    ~CRYPTO_ALG_INTERNAL)
  		return -EINVAL;

  	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
  	if (!inst)
  		return -ENOMEM;
  
  	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER |
  				      (algt->type & CRYPTO_ALG_INTERNAL),
  				  CRYPTO_ALG_TYPE_MASK |
  				  (algt->mask & CRYPTO_ALG_INTERNAL));
  	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);

  	if (err)

  		goto err_put_alg;

  	err = crypto_inst_setname(skcipher_crypto_instance(inst), "pcbc", alg);
  	if (err)
  		goto err_drop_spawn;

  	inst->alg.base.cra_flags = alg->cra_flags & CRYPTO_ALG_INTERNAL;
  	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_pcbc_ctx);

  	inst->alg.init = crypto_pcbc_init_tfm;
  	inst->alg.exit = crypto_pcbc_exit_tfm;

  	inst->alg.setkey = crypto_pcbc_setkey;
  	inst->alg.encrypt = crypto_pcbc_encrypt;
  	inst->alg.decrypt = crypto_pcbc_decrypt;

  	inst->free = crypto_pcbc_free;

  	err = skcipher_register_instance(tmpl, inst);
  	if (err)
  		goto err_drop_spawn;

  	crypto_mod_put(alg);

  
  out:
  	return err;
  
  err_drop_spawn:
  	crypto_drop_spawn(spawn);

  err_put_alg:
  	crypto_mod_put(alg);

  err_free_inst:

  	kfree(inst);

  	goto out;

  }
  
  static struct crypto_template crypto_pcbc_tmpl = {
  	.name = "pcbc",

  	.create = crypto_pcbc_create,

  	.module = THIS_MODULE,
  };
  
  static int __init crypto_pcbc_module_init(void)
  {
  	return crypto_register_template(&crypto_pcbc_tmpl);
  }
  
  static void __exit crypto_pcbc_module_exit(void)
  {
  	crypto_unregister_template(&crypto_pcbc_tmpl);
  }
  
  module_init(crypto_pcbc_module_init);
  module_exit(crypto_pcbc_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("PCBC block cipher algorithm");

  MODULE_ALIAS_CRYPTO("pcbc");