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

  /*
   * 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>

   */

  #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>

  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_cipher *cipher = skcipher_cipher_simple(tfm);

  	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,

  							     cipher);

  		else

  			nbytes = crypto_pcbc_encrypt_segment(req, &walk,

  							     cipher);

  		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_cipher *cipher = skcipher_cipher_simple(tfm);

  	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,

  							     cipher);

  		else

  			nbytes = crypto_pcbc_decrypt_segment(req, &walk,

  							     cipher);

  		err = skcipher_walk_done(&walk, nbytes);

  	}
  
  	return err;
  }

  static int crypto_pcbc_create(struct crypto_template *tmpl, struct rtattr **tb)

  {

  	struct skcipher_instance *inst;

  	int err;

  	inst = skcipher_alloc_instance_simple(tmpl, tb);

  	if (IS_ERR(inst))
  		return PTR_ERR(inst);

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

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

  		inst->free(inst);

  	return err;

  }
  
  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);
  }

  subsys_initcall(crypto_pcbc_module_init);

  module_exit(crypto_pcbc_module_exit);
  
  MODULE_LICENSE("GPL");

  MODULE_DESCRIPTION("PCBC block cipher mode of operation");

  MODULE_ALIAS_CRYPTO("pcbc");