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

  /* XTS: as defined in IEEE1619/D16
   *	http://grouper.ieee.org/groups/1619/email/pdf00086.pdf

   *
   * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
   *

   * Based on ecb.c

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

   */

  #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>

  struct xts_tfm_ctx {

  	struct crypto_skcipher *child;

  	struct crypto_cipher *tweak;
  };

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

  struct xts_request_ctx {

  	le128 t;

  	struct scatterlist *tail;
  	struct scatterlist sg[2];

  	struct skcipher_request subreq;
  };

  static int xts_setkey(struct crypto_skcipher *parent, const u8 *key,
  		      unsigned int keylen)

  {

  	struct xts_tfm_ctx *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);

  	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);

  	return crypto_skcipher_setkey(child, key, keylen);

  }

  /*
   * We compute the tweak masks twice (both before and after the ECB encryption or
   * decryption) to avoid having to allocate a temporary buffer and/or make
   * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
   * just doing the gf128mul_x_ble() calls again.
   */

  static int xts_xor_tweak(struct skcipher_request *req, bool second_pass,
  			 bool enc)

  {

  	struct xts_request_ctx *rctx = skcipher_request_ctx(req);

  	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);

  	const bool cts = (req->cryptlen % XTS_BLOCK_SIZE);

  	const int bs = XTS_BLOCK_SIZE;
  	struct skcipher_walk w;

  	le128 t = rctx->t;

  	int err;

  	if (second_pass) {
  		req = &rctx->subreq;
  		/* set to our TFM to enforce correct alignment: */
  		skcipher_request_set_tfm(req, tfm);

  	}

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

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

  		le128 *wsrc;
  		le128 *wdst;

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

  		do {

  			if (unlikely(cts) &&
  			    w.total - w.nbytes + avail < 2 * XTS_BLOCK_SIZE) {
  				if (!enc) {
  					if (second_pass)
  						rctx->t = t;
  					gf128mul_x_ble(&t, &t);
  				}
  				le128_xor(wdst, &t, wsrc);
  				if (enc && second_pass)
  					gf128mul_x_ble(&rctx->t, &t);
  				skcipher_walk_done(&w, avail - bs);
  				return 0;
  			}

  			le128_xor(wdst++, &t, wsrc++);
  			gf128mul_x_ble(&t, &t);

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

  		err = skcipher_walk_done(&w, avail);
  	}

  	return err;
  }

  static int xts_xor_tweak_pre(struct skcipher_request *req, bool enc)

  {

  	return xts_xor_tweak(req, false, enc);

  }

  static int xts_xor_tweak_post(struct skcipher_request *req, bool enc)

  {

  	return xts_xor_tweak(req, true, enc);

  }

  static void xts_cts_done(struct crypto_async_request *areq, int err)

  {

  	struct skcipher_request *req = areq->data;
  	le128 b;
  
  	if (!err) {

  		struct xts_request_ctx *rctx = skcipher_request_ctx(req);

  
  		scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
  		le128_xor(&b, &rctx->t, &b);
  		scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 1);
  	}
  
  	skcipher_request_complete(req, err);
  }

  static int xts_cts_final(struct skcipher_request *req,
  			 int (*crypt)(struct skcipher_request *req))

  {

  	const struct xts_tfm_ctx *ctx =
  		crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));

  	int offset = req->cryptlen & ~(XTS_BLOCK_SIZE - 1);

  	struct xts_request_ctx *rctx = skcipher_request_ctx(req);

  	struct skcipher_request *subreq = &rctx->subreq;
  	int tail = req->cryptlen % XTS_BLOCK_SIZE;
  	le128 b[2];
  	int err;
  
  	rctx->tail = scatterwalk_ffwd(rctx->sg, req->dst,
  				      offset - XTS_BLOCK_SIZE);
  
  	scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);

  	b[1] = b[0];

  	scatterwalk_map_and_copy(b, req->src, offset, tail, 0);
  
  	le128_xor(b, &rctx->t, b);
  
  	scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE + tail, 1);
  
  	skcipher_request_set_tfm(subreq, ctx->child);

  	skcipher_request_set_callback(subreq, req->base.flags, xts_cts_done,
  				      req);

  	skcipher_request_set_crypt(subreq, rctx->tail, rctx->tail,
  				   XTS_BLOCK_SIZE, NULL);
  
  	err = crypt(subreq);
  	if (err)
  		return err;
  
  	scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
  	le128_xor(b, &rctx->t, b);
  	scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 1);
  
  	return 0;

  }

  static void xts_encrypt_done(struct crypto_async_request *areq, int err)

  {

  	struct skcipher_request *req = areq->data;
  
  	if (!err) {

  		struct xts_request_ctx *rctx = skcipher_request_ctx(req);

  
  		rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;

  		err = xts_xor_tweak_post(req, true);

  
  		if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {

  			err = xts_cts_final(req, crypto_skcipher_encrypt);

  			if (err == -EINPROGRESS)
  				return;
  		}
  	}
  
  	skcipher_request_complete(req, err);

  }

  static void xts_decrypt_done(struct crypto_async_request *areq, int err)

  {
  	struct skcipher_request *req = areq->data;

  	if (!err) {

  		struct xts_request_ctx *rctx = skcipher_request_ctx(req);

  
  		rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;

  		err = xts_xor_tweak_post(req, false);

  
  		if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {

  			err = xts_cts_final(req, crypto_skcipher_decrypt);

  			if (err == -EINPROGRESS)
  				return;
  		}

  	}

  	skcipher_request_complete(req, err);
  }

  static int xts_init_crypt(struct skcipher_request *req,
  			  crypto_completion_t compl)

  {

  	const struct xts_tfm_ctx *ctx =
  		crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
  	struct xts_request_ctx *rctx = skcipher_request_ctx(req);

  	struct skcipher_request *subreq = &rctx->subreq;

  	if (req->cryptlen < XTS_BLOCK_SIZE)
  		return -EINVAL;

  	skcipher_request_set_tfm(subreq, ctx->child);

  	skcipher_request_set_callback(subreq, req->base.flags, compl, req);

  	skcipher_request_set_crypt(subreq, req->dst, req->dst,

  				   req->cryptlen & ~(XTS_BLOCK_SIZE - 1), NULL);

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

  
  	return 0;

  }

  static int xts_encrypt(struct skcipher_request *req)

  {

  	struct xts_request_ctx *rctx = skcipher_request_ctx(req);

  	struct skcipher_request *subreq = &rctx->subreq;

  	int err;

  	err = xts_init_crypt(req, xts_encrypt_done) ?:
  	      xts_xor_tweak_pre(req, true) ?:

  	      crypto_skcipher_encrypt(subreq) ?:

  	      xts_xor_tweak_post(req, true);

  	if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
  		return err;

  	return xts_cts_final(req, crypto_skcipher_encrypt);

  }

  static int xts_decrypt(struct skcipher_request *req)

  {

  	struct xts_request_ctx *rctx = skcipher_request_ctx(req);

  	struct skcipher_request *subreq = &rctx->subreq;

  	int err;

  	err = xts_init_crypt(req, xts_decrypt_done) ?:
  	      xts_xor_tweak_pre(req, false) ?:

  	      crypto_skcipher_decrypt(subreq) ?:

  	      xts_xor_tweak_post(req, false);

  
  	if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
  		return err;

  	return xts_cts_final(req, crypto_skcipher_decrypt);

  }

  static int xts_init_tfm(struct crypto_skcipher *tfm)

  {

  	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
  	struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);

  	struct xts_tfm_ctx *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 xts_request_ctx));

  
  	return 0;
  }

  static void xts_exit_tfm(struct crypto_skcipher *tfm)

  {

  	struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);

  
  	crypto_free_skcipher(ctx->child);

  	crypto_free_cipher(ctx->tweak);
  }

  static void xts_free_instance(struct skcipher_instance *inst)

  {

  	struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
  
  	crypto_drop_skcipher(&ictx->spawn);

  	kfree(inst);
  }

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

  {

  	struct skcipher_instance *inst;

  	struct xts_instance_ctx *ctx;
  	struct skcipher_alg *alg;
  	const char *cipher_name;

  	u32 mask;

  	int err;

  	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
  	if (err)
  		return err;

  
  	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);

  	err = crypto_grab_skcipher(&ctx->spawn, skcipher_crypto_instance(inst),
  				   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,
  					   skcipher_crypto_instance(inst),
  					   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_free_inst;

  	if (crypto_skcipher_alg_ivsize(alg))

  		goto err_free_inst;

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

  		goto err_free_inst;

  	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_free_inst;

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

  			goto err_free_inst;

  		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_free_inst;

  		}

  	} else

  		goto err_free_inst;

  	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 xts_tfm_ctx);

  	inst->alg.init = xts_init_tfm;
  	inst->alg.exit = xts_exit_tfm;

  	inst->alg.setkey = xts_setkey;
  	inst->alg.encrypt = xts_encrypt;
  	inst->alg.decrypt = xts_decrypt;

  	inst->free = xts_free_instance;

  
  	err = skcipher_register_instance(tmpl, inst);

  	if (err) {

  err_free_inst:

  		xts_free_instance(inst);

  	}
  	return err;

  }

  static struct crypto_template xts_tmpl = {

  	.name = "xts",

  	.create = xts_create,

  	.module = THIS_MODULE,
  };

  static int __init xts_module_init(void)

  {

  	return crypto_register_template(&xts_tmpl);

  }

  static void __exit xts_module_exit(void)

  {

  	crypto_unregister_template(&xts_tmpl);

  }

  subsys_initcall(xts_module_init);
  module_exit(xts_module_exit);

  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("XTS block cipher mode");

  MODULE_ALIAS_CRYPTO("xts");