/*
   * Copyright (C)2006 USAGI/WIDE Project
   *
   * 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.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License

   * along with this program.  If not, see <http://www.gnu.org/licenses/>.

   *
   * Author:
   * 	Kazunori Miyazawa <miyazawa@linux-ipv6.org>
   */

  #include <crypto/internal/hash.h>

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

  #include <linux/module.h>

  static u_int32_t ks[12] = {0x01010101, 0x01010101, 0x01010101, 0x01010101,
  			   0x02020202, 0x02020202, 0x02020202, 0x02020202,
  			   0x03030303, 0x03030303, 0x03030303, 0x03030303};

  /*
   * +------------------------
   * | <parent tfm>
   * +------------------------

   * | xcbc_tfm_ctx

   * +------------------------

   * | consts (block size * 2)

   * +------------------------

   */
  struct xcbc_tfm_ctx {
  	struct crypto_cipher *child;
  	u8 ctx[];
  };
  
  /*

   * +------------------------

   * | <shash desc>

   * +------------------------

   * | xcbc_desc_ctx
   * +------------------------
   * | odds (block size)
   * +------------------------
   * | prev (block size)

   * +------------------------
   */

  struct xcbc_desc_ctx {

  	unsigned int len;

  	u8 ctx[];

  };

  static int crypto_xcbc_digest_setkey(struct crypto_shash *parent,
  				     const u8 *inkey, unsigned int keylen)

  {

  	unsigned long alignmask = crypto_shash_alignmask(parent);
  	struct xcbc_tfm_ctx *ctx = crypto_shash_ctx(parent);

  	int bs = crypto_shash_blocksize(parent);

  	u8 *consts = PTR_ALIGN(&ctx->ctx[0], alignmask + 1);

  	int err = 0;
  	u8 key1[bs];

  	if ((err = crypto_cipher_setkey(ctx->child, inkey, keylen)))
  		return err;

  	crypto_cipher_encrypt_one(ctx->child, consts, (u8 *)ks + bs);
  	crypto_cipher_encrypt_one(ctx->child, consts + bs, (u8 *)ks + bs * 2);
  	crypto_cipher_encrypt_one(ctx->child, key1, (u8 *)ks);

  
  	return crypto_cipher_setkey(ctx->child, key1, bs);

  }

  static int crypto_xcbc_digest_init(struct shash_desc *pdesc)

  {

  	unsigned long alignmask = crypto_shash_alignmask(pdesc->tfm);
  	struct xcbc_desc_ctx *ctx = shash_desc_ctx(pdesc);

  	int bs = crypto_shash_blocksize(pdesc->tfm);

  	u8 *prev = PTR_ALIGN(&ctx->ctx[0], alignmask + 1) + bs;

  
  	ctx->len = 0;

  	memset(prev, 0, bs);

  
  	return 0;
  }

  static int crypto_xcbc_digest_update(struct shash_desc *pdesc, const u8 *p,
  				     unsigned int len)

  {

  	struct crypto_shash *parent = pdesc->tfm;

  	unsigned long alignmask = crypto_shash_alignmask(parent);
  	struct xcbc_tfm_ctx *tctx = crypto_shash_ctx(parent);
  	struct xcbc_desc_ctx *ctx = shash_desc_ctx(pdesc);
  	struct crypto_cipher *tfm = tctx->child;

  	int bs = crypto_shash_blocksize(parent);

  	u8 *odds = PTR_ALIGN(&ctx->ctx[0], alignmask + 1);
  	u8 *prev = odds + bs;

  
  	/* checking the data can fill the block */
  	if ((ctx->len + len) <= bs) {

  		memcpy(odds + ctx->len, p, len);

  		ctx->len += len;
  		return 0;

  	}

  	/* filling odds with new data and encrypting it */

  	memcpy(odds + ctx->len, p, bs - ctx->len);

  	len -= bs - ctx->len;
  	p += bs - ctx->len;

  	crypto_xor(prev, odds, bs);
  	crypto_cipher_encrypt_one(tfm, prev, prev);

  
  	/* clearing the length */
  	ctx->len = 0;
  
  	/* encrypting the rest of data */
  	while (len > bs) {

  		crypto_xor(prev, p, bs);
  		crypto_cipher_encrypt_one(tfm, prev, prev);

  		p += bs;
  		len -= bs;
  	}
  
  	/* keeping the surplus of blocksize */
  	if (len) {

  		memcpy(odds, p, len);

  		ctx->len = len;
  	}
  
  	return 0;

  }

  static int crypto_xcbc_digest_final(struct shash_desc *pdesc, u8 *out)

  {

  	struct crypto_shash *parent = pdesc->tfm;

  	unsigned long alignmask = crypto_shash_alignmask(parent);
  	struct xcbc_tfm_ctx *tctx = crypto_shash_ctx(parent);
  	struct xcbc_desc_ctx *ctx = shash_desc_ctx(pdesc);
  	struct crypto_cipher *tfm = tctx->child;

  	int bs = crypto_shash_blocksize(parent);

  	u8 *consts = PTR_ALIGN(&tctx->ctx[0], alignmask + 1);
  	u8 *odds = PTR_ALIGN(&ctx->ctx[0], alignmask + 1);
  	u8 *prev = odds + bs;
  	unsigned int offset = 0;

  	if (ctx->len != bs) {

  		unsigned int rlen;

  		u8 *p = odds + ctx->len;

  		*p = 0x80;
  		p++;
  
  		rlen = bs - ctx->len -1;
  		if (rlen)
  			memset(p, 0, rlen);

  		offset += bs;
  	}

  	crypto_xor(prev, odds, bs);
  	crypto_xor(prev, consts + offset, bs);

  	crypto_cipher_encrypt_one(tfm, out, prev);

  
  	return 0;
  }

  static int xcbc_init_tfm(struct crypto_tfm *tfm)
  {

  	struct crypto_cipher *cipher;

  	struct crypto_instance *inst = (void *)tfm->__crt_alg;
  	struct crypto_spawn *spawn = crypto_instance_ctx(inst);

  	struct xcbc_tfm_ctx *ctx = crypto_tfm_ctx(tfm);

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

  	ctx->child = cipher;

  
  	return 0;
  };
  
  static void xcbc_exit_tfm(struct crypto_tfm *tfm)
  {

  	struct xcbc_tfm_ctx *ctx = crypto_tfm_ctx(tfm);

  	crypto_free_cipher(ctx->child);
  }

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

  {

  	struct shash_instance *inst;

  	struct crypto_alg *alg;

  	unsigned long alignmask;

  	int err;

  	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);

  	if (err)

  		return err;

  
  	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
  				  CRYPTO_ALG_TYPE_MASK);

  	if (IS_ERR(alg))

  		return PTR_ERR(alg);

  
  	switch(alg->cra_blocksize) {
  	case 16:
  		break;
  	default:

  		goto out_put_alg;

  	}

  	inst = shash_alloc_instance("xcbc", alg);

  	err = PTR_ERR(inst);

  	if (IS_ERR(inst))
  		goto out_put_alg;

  	err = crypto_init_spawn(shash_instance_ctx(inst), alg,
  				shash_crypto_instance(inst),
  				CRYPTO_ALG_TYPE_MASK);
  	if (err)
  		goto out_free_inst;

  	alignmask = alg->cra_alignmask | 3;
  	inst->alg.base.cra_alignmask = alignmask;

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

  
  	inst->alg.digestsize = alg->cra_blocksize;

  	inst->alg.descsize = ALIGN(sizeof(struct xcbc_desc_ctx),
  				   crypto_tfm_ctx_alignment()) +

  			     (alignmask &

  			      ~(crypto_tfm_ctx_alignment() - 1)) +
  			     alg->cra_blocksize * 2;
  
  	inst->alg.base.cra_ctxsize = ALIGN(sizeof(struct xcbc_tfm_ctx),

  					   alignmask + 1) +

  				     alg->cra_blocksize * 2;

  	inst->alg.base.cra_init = xcbc_init_tfm;
  	inst->alg.base.cra_exit = xcbc_exit_tfm;
  
  	inst->alg.init = crypto_xcbc_digest_init;
  	inst->alg.update = crypto_xcbc_digest_update;
  	inst->alg.final = crypto_xcbc_digest_final;
  	inst->alg.setkey = crypto_xcbc_digest_setkey;
  
  	err = shash_register_instance(tmpl, inst);
  	if (err) {
  out_free_inst:
  		shash_free_instance(shash_crypto_instance(inst));
  	}

  
  out_put_alg:
  	crypto_mod_put(alg);

  	return err;

  }
  
  static struct crypto_template crypto_xcbc_tmpl = {
  	.name = "xcbc",

  	.create = xcbc_create,
  	.free = shash_free_instance,

  	.module = THIS_MODULE,
  };
  
  static int __init crypto_xcbc_module_init(void)
  {
  	return crypto_register_template(&crypto_xcbc_tmpl);
  }
  
  static void __exit crypto_xcbc_module_exit(void)
  {
  	crypto_unregister_template(&crypto_xcbc_tmpl);
  }
  
  module_init(crypto_xcbc_module_init);
  module_exit(crypto_xcbc_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("XCBC keyed hash algorithm");

  MODULE_ALIAS_CRYPTO("xcbc");