/* XTS: as defined in IEEE1619/D16
   *	http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
   *	(sector sizes which are not a multiple of 16 bytes are,
   *	however currently unsupported)
   *
   * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
   *

   * Based on ecb.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/internal/skcipher.h>
  #include <crypto/scatterwalk.h>

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

  #include <crypto/xts.h>

  #include <crypto/b128ops.h>
  #include <crypto/gf128mul.h>

  #define XTS_BUFFER_SIZE 128u

  struct priv {

  	struct crypto_skcipher *child;

  	struct crypto_cipher *tweak;
  };

  struct xts_instance_ctx {
  	struct crypto_skcipher_spawn spawn;
  	char name[CRYPTO_MAX_ALG_NAME];
  };
  
  struct rctx {

  	le128 buf[XTS_BUFFER_SIZE / sizeof(le128)];

  	le128 t;

  	le128 *ext;

  
  	struct scatterlist srcbuf[2];
  	struct scatterlist dstbuf[2];
  	struct scatterlist *src;
  	struct scatterlist *dst;
  
  	unsigned int left;
  
  	struct skcipher_request subreq;
  };
  
  static int setkey(struct crypto_skcipher *parent, const u8 *key,

  		  unsigned int keylen)
  {

  	struct priv *ctx = crypto_skcipher_ctx(parent);
  	struct crypto_skcipher *child;
  	struct crypto_cipher *tweak;

  	int err;

  	err = xts_verify_key(parent, key, keylen);

  	if (err)
  		return err;

  	keylen /= 2;

  	/* we need two cipher instances: one to compute the initial 'tweak'

  	 * by encrypting the IV (usually the 'plain' iv) and the other
  	 * one to encrypt and decrypt the data */
  
  	/* tweak cipher, uses Key2 i.e. the second half of *key */

  	tweak = ctx->tweak;
  	crypto_cipher_clear_flags(tweak, CRYPTO_TFM_REQ_MASK);
  	crypto_cipher_set_flags(tweak, crypto_skcipher_get_flags(parent) &

  				       CRYPTO_TFM_REQ_MASK);

  	err = crypto_cipher_setkey(tweak, key + keylen, keylen);
  	crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(tweak) &
  					  CRYPTO_TFM_RES_MASK);

  	if (err)
  		return err;

  	/* data cipher, uses Key1 i.e. the first half of *key */

  	child = ctx->child;

  	crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
  					 CRYPTO_TFM_REQ_MASK);
  	err = crypto_skcipher_setkey(child, key, keylen);
  	crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
  					  CRYPTO_TFM_RES_MASK);

  	return err;
  }

  static int post_crypt(struct skcipher_request *req)
  {
  	struct rctx *rctx = skcipher_request_ctx(req);

  	le128 *buf = rctx->ext ?: rctx->buf;

  	struct skcipher_request *subreq;
  	const int bs = XTS_BLOCK_SIZE;
  	struct skcipher_walk w;
  	struct scatterlist *sg;
  	unsigned offset;
  	int err;

  	subreq = &rctx->subreq;
  	err = skcipher_walk_virt(&w, subreq, false);

  	while (w.nbytes) {
  		unsigned int avail = w.nbytes;

  		le128 *wdst;

  		wdst = w.dst.virt.addr;
  
  		do {

  			le128_xor(wdst, buf++, wdst);

  			wdst++;
  		} while ((avail -= bs) >= bs);
  
  		err = skcipher_walk_done(&w, avail);
  	}
  
  	rctx->left -= subreq->cryptlen;
  
  	if (err || !rctx->left)
  		goto out;
  
  	rctx->dst = rctx->dstbuf;
  
  	scatterwalk_done(&w.out, 0, 1);
  	sg = w.out.sg;
  	offset = w.out.offset;
  
  	if (rctx->dst != sg) {
  		rctx->dst[0] = *sg;
  		sg_unmark_end(rctx->dst);

  		scatterwalk_crypto_chain(rctx->dst, sg_next(sg), 2);

  	}
  	rctx->dst[0].length -= offset - sg->offset;
  	rctx->dst[0].offset = offset;
  
  out:
  	return err;

  }

  static int pre_crypt(struct skcipher_request *req)

  {

  	struct rctx *rctx = skcipher_request_ctx(req);

  	le128 *buf = rctx->ext ?: rctx->buf;

  	struct skcipher_request *subreq;

  	const int bs = XTS_BLOCK_SIZE;

  	struct skcipher_walk w;
  	struct scatterlist *sg;
  	unsigned cryptlen;
  	unsigned offset;
  	bool more;
  	int err;

  	subreq = &rctx->subreq;
  	cryptlen = subreq->cryptlen;

  	more = rctx->left > cryptlen;
  	if (!more)
  		cryptlen = rctx->left;

  	skcipher_request_set_crypt(subreq, rctx->src, rctx->dst,
  				   cryptlen, NULL);

  	err = skcipher_walk_virt(&w, subreq, false);

  	while (w.nbytes) {
  		unsigned int avail = w.nbytes;

  		le128 *wsrc;
  		le128 *wdst;

  		wsrc = w.src.virt.addr;
  		wdst = w.dst.virt.addr;

  		do {
  			*buf++ = rctx->t;

  			le128_xor(wdst++, &rctx->t, wsrc++);

  			gf128mul_x_ble(&rctx->t, &rctx->t);

  		} while ((avail -= bs) >= bs);

  		err = skcipher_walk_done(&w, avail);
  	}
  
  	skcipher_request_set_crypt(subreq, rctx->dst, rctx->dst,
  				   cryptlen, NULL);

  	if (err || !more)
  		goto out;

  	rctx->src = rctx->srcbuf;
  
  	scatterwalk_done(&w.in, 0, 1);
  	sg = w.in.sg;
  	offset = w.in.offset;
  
  	if (rctx->src != sg) {
  		rctx->src[0] = *sg;
  		sg_unmark_end(rctx->src);

  		scatterwalk_crypto_chain(rctx->src, sg_next(sg), 2);

  	}

  	rctx->src[0].length -= offset - sg->offset;
  	rctx->src[0].offset = offset;

  out:

  	return err;
  }

  static int init_crypt(struct skcipher_request *req, crypto_completion_t done)

  {

  	struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
  	struct rctx *rctx = skcipher_request_ctx(req);
  	struct skcipher_request *subreq;
  	gfp_t gfp;
  
  	subreq = &rctx->subreq;
  	skcipher_request_set_tfm(subreq, ctx->child);
  	skcipher_request_set_callback(subreq, req->base.flags, done, req);
  
  	gfp = req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL :
  							   GFP_ATOMIC;
  	rctx->ext = NULL;
  
  	subreq->cryptlen = XTS_BUFFER_SIZE;
  	if (req->cryptlen > XTS_BUFFER_SIZE) {

  		unsigned int n = min(req->cryptlen, (unsigned int)PAGE_SIZE);
  
  		rctx->ext = kmalloc(n, gfp);
  		if (rctx->ext)
  			subreq->cryptlen = n;

  	}
  
  	rctx->src = req->src;
  	rctx->dst = req->dst;
  	rctx->left = req->cryptlen;

  	/* calculate first value of T */
  	crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv);
  
  	return 0;

  }

  static void exit_crypt(struct skcipher_request *req)

  {

  	struct rctx *rctx = skcipher_request_ctx(req);
  
  	rctx->left = 0;

  	if (rctx->ext)
  		kzfree(rctx->ext);
  }
  
  static int do_encrypt(struct skcipher_request *req, int err)
  {
  	struct rctx *rctx = skcipher_request_ctx(req);
  	struct skcipher_request *subreq;
  
  	subreq = &rctx->subreq;
  
  	while (!err && rctx->left) {
  		err = pre_crypt(req) ?:
  		      crypto_skcipher_encrypt(subreq) ?:
  		      post_crypt(req);

  		if (err == -EINPROGRESS || err == -EBUSY)

  			return err;
  	}
  
  	exit_crypt(req);
  	return err;
  }
  
  static void encrypt_done(struct crypto_async_request *areq, int err)
  {
  	struct skcipher_request *req = areq->data;
  	struct skcipher_request *subreq;
  	struct rctx *rctx;
  
  	rctx = skcipher_request_ctx(req);

  
  	if (err == -EINPROGRESS) {
  		if (rctx->left != req->cryptlen)
  			return;
  		goto out;
  	}

  	subreq = &rctx->subreq;
  	subreq->base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;
  
  	err = do_encrypt(req, err ?: post_crypt(req));
  	if (rctx->left)
  		return;

  out:

  	skcipher_request_complete(req, err);
  }
  
  static int encrypt(struct skcipher_request *req)
  {
  	return do_encrypt(req, init_crypt(req, encrypt_done));
  }
  
  static int do_decrypt(struct skcipher_request *req, int err)
  {
  	struct rctx *rctx = skcipher_request_ctx(req);
  	struct skcipher_request *subreq;
  
  	subreq = &rctx->subreq;
  
  	while (!err && rctx->left) {
  		err = pre_crypt(req) ?:
  		      crypto_skcipher_decrypt(subreq) ?:
  		      post_crypt(req);

  		if (err == -EINPROGRESS || err == -EBUSY)

  			return err;
  	}
  
  	exit_crypt(req);
  	return err;
  }
  
  static void decrypt_done(struct crypto_async_request *areq, int err)
  {
  	struct skcipher_request *req = areq->data;
  	struct skcipher_request *subreq;
  	struct rctx *rctx;
  
  	rctx = skcipher_request_ctx(req);

  
  	if (err == -EINPROGRESS) {
  		if (rctx->left != req->cryptlen)
  			return;
  		goto out;
  	}

  	subreq = &rctx->subreq;
  	subreq->base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;
  
  	err = do_decrypt(req, err ?: post_crypt(req));
  	if (rctx->left)
  		return;

  out:

  	skcipher_request_complete(req, err);
  }
  
  static int decrypt(struct skcipher_request *req)
  {
  	return do_decrypt(req, init_crypt(req, decrypt_done));

  }

  static int init_tfm(struct crypto_skcipher *tfm)

  {

  	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
  	struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
  	struct priv *ctx = crypto_skcipher_ctx(tfm);
  	struct crypto_skcipher *child;
  	struct crypto_cipher *tweak;

  	child = crypto_spawn_skcipher(&ictx->spawn);
  	if (IS_ERR(child))
  		return PTR_ERR(child);

  	ctx->child = child;

  	tweak = crypto_alloc_cipher(ictx->name, 0, 0);
  	if (IS_ERR(tweak)) {
  		crypto_free_skcipher(ctx->child);
  		return PTR_ERR(tweak);

  	}

  	ctx->tweak = tweak;
  
  	crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) +
  					 sizeof(struct rctx));

  
  	return 0;
  }

  static void exit_tfm(struct crypto_skcipher *tfm)

  {

  	struct priv *ctx = crypto_skcipher_ctx(tfm);
  
  	crypto_free_skcipher(ctx->child);

  	crypto_free_cipher(ctx->tweak);
  }

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

  {

  	struct skcipher_instance *inst;
  	struct crypto_attr_type *algt;
  	struct xts_instance_ctx *ctx;
  	struct skcipher_alg *alg;
  	const char *cipher_name;

  	u32 mask;

  	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)
  		return -EINVAL;
  
  	cipher_name = crypto_attr_alg_name(tb[1]);
  	if (IS_ERR(cipher_name))
  		return PTR_ERR(cipher_name);
  
  	inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
  	if (!inst)
  		return -ENOMEM;
  
  	ctx = skcipher_instance_ctx(inst);
  
  	crypto_set_skcipher_spawn(&ctx->spawn, skcipher_crypto_instance(inst));

  
  	mask = crypto_requires_off(algt->type, algt->mask,
  				   CRYPTO_ALG_NEED_FALLBACK |
  				   CRYPTO_ALG_ASYNC);
  
  	err = crypto_grab_skcipher(&ctx->spawn, cipher_name, 0, mask);

  	if (err == -ENOENT) {
  		err = -ENAMETOOLONG;
  		if (snprintf(ctx->name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
  			     cipher_name) >= CRYPTO_MAX_ALG_NAME)
  			goto err_free_inst;

  		err = crypto_grab_skcipher(&ctx->spawn, ctx->name, 0, mask);

  	}

  	if (err)

  		goto err_free_inst;

  	alg = crypto_skcipher_spawn_alg(&ctx->spawn);

  	err = -EINVAL;
  	if (alg->base.cra_blocksize != XTS_BLOCK_SIZE)
  		goto err_drop_spawn;

  	if (crypto_skcipher_alg_ivsize(alg))
  		goto err_drop_spawn;

  	err = crypto_inst_setname(skcipher_crypto_instance(inst), "xts",
  				  &alg->base);
  	if (err)
  		goto err_drop_spawn;

  	err = -EINVAL;
  	cipher_name = alg->base.cra_name;

  	/* Alas we screwed up the naming so we have to mangle the
  	 * cipher name.
  	 */
  	if (!strncmp(cipher_name, "ecb(", 4)) {
  		unsigned len;

  		len = strlcpy(ctx->name, cipher_name + 4, sizeof(ctx->name));
  		if (len < 2 || len >= sizeof(ctx->name))
  			goto err_drop_spawn;

  		if (ctx->name[len - 1] != ')')
  			goto err_drop_spawn;

  		ctx->name[len - 1] = 0;

  		if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,

  			     "xts(%s)", ctx->name) >= CRYPTO_MAX_ALG_NAME) {
  			err = -ENAMETOOLONG;
  			goto err_drop_spawn;
  		}

  	} else
  		goto err_drop_spawn;

  	inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
  	inst->alg.base.cra_priority = alg->base.cra_priority;
  	inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE;
  	inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
  				       (__alignof__(u64) - 1);
  
  	inst->alg.ivsize = XTS_BLOCK_SIZE;
  	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) * 2;
  	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2;
  
  	inst->alg.base.cra_ctxsize = sizeof(struct priv);
  
  	inst->alg.init = init_tfm;
  	inst->alg.exit = exit_tfm;
  
  	inst->alg.setkey = setkey;
  	inst->alg.encrypt = encrypt;
  	inst->alg.decrypt = decrypt;
  
  	inst->free = free;
  
  	err = skcipher_register_instance(tmpl, inst);
  	if (err)
  		goto err_drop_spawn;
  
  out:
  	return err;
  
  err_drop_spawn:
  	crypto_drop_skcipher(&ctx->spawn);
  err_free_inst:

  	kfree(inst);

  	goto out;

  }
  
  static struct crypto_template crypto_tmpl = {
  	.name = "xts",

  	.create = create,

  	.module = THIS_MODULE,
  };
  
  static int __init crypto_module_init(void)
  {
  	return crypto_register_template(&crypto_tmpl);
  }
  
  static void __exit crypto_module_exit(void)
  {
  	crypto_unregister_template(&crypto_tmpl);
  }
  
  module_init(crypto_module_init);
  module_exit(crypto_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("XTS block cipher mode");

  MODULE_ALIAS_CRYPTO("xts");