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

  /* LRW: as defined by Cyril Guyot in
   *	http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
   *
   * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
   *

   * Based on ecb.c

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

   */
  /* This implementation is checked against the test vectors in the above
   * document and by a test vector provided by Ken Buchanan at
   * http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
   *
   * The test vectors are included in the testing module tcrypt.[ch] */

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

  #define LRW_BLOCK_SIZE 16

  struct priv {

  	struct crypto_skcipher *child;

  
  	/*
  	 * optimizes multiplying a random (non incrementing, as at the
  	 * start of a new sector) value with key2, we could also have
  	 * used 4k optimization tables or no optimization at all. In the
  	 * latter case we would have to store key2 here
  	 */
  	struct gf128mul_64k *table;
  
  	/*
  	 * stores:
  	 *  key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
  	 *  key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
  	 *  key2*{ 0,0,...1,1,1,1,1 }, etc
  	 * needed for optimized multiplication of incrementing values
  	 * with key2
  	 */
  	be128 mulinc[128];

  };

  struct rctx {

  	be128 t;

  	struct skcipher_request subreq;
  };

  static inline void setbit128_bbe(void *b, int bit)
  {

  	__set_bit(bit ^ (0x80 -
  #ifdef __BIG_ENDIAN
  			 BITS_PER_LONG
  #else
  			 BITS_PER_BYTE
  #endif
  			), b);

  }

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

  {

  	struct priv *ctx = crypto_skcipher_ctx(parent);
  	struct crypto_skcipher *child = ctx->child;
  	int err, bsize = LRW_BLOCK_SIZE;
  	const u8 *tweak = key + keylen - bsize;

  	be128 tmp = { 0 };

  	int i;

  	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 - bsize);
  	crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
  					  CRYPTO_TFM_RES_MASK);
  	if (err)
  		return err;

  	if (ctx->table)
  		gf128mul_free_64k(ctx->table);
  
  	/* initialize multiplication table for Key2 */

  	ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);

  	if (!ctx->table)
  		return -ENOMEM;
  
  	/* initialize optimization table */
  	for (i = 0; i < 128; i++) {
  		setbit128_bbe(&tmp, i);
  		ctx->mulinc[i] = tmp;
  		gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
  	}
  
  	return 0;
  }

  /*
   * Returns the number of trailing '1' bits in the words of the counter, which is
   * represented by 4 32-bit words, arranged from least to most significant.
   * At the same time, increments the counter by one.
   *
   * For example:
   *
   * u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
   * int i = next_index(&counter);
   * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
   */
  static int next_index(u32 *counter)

  {

  	int i, res = 0;

  	for (i = 0; i < 4; i++) {

  		if (counter[i] + 1 != 0)
  			return res + ffz(counter[i]++);

  		counter[i] = 0;
  		res += 32;

  	}

  	/*
  	 * If we get here, then x == 128 and we are incrementing the counter
  	 * from all ones to all zeros. This means we must return index 127, i.e.
  	 * the one corresponding to key2*{ 1,...,1 }.
  	 */
  	return 127;

  }

  /*
   * 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 next_index() calls again.
   */
  static int xor_tweak(struct skcipher_request *req, bool second_pass)

  {

  	const int bs = LRW_BLOCK_SIZE;

  	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);

  	struct priv *ctx = crypto_skcipher_ctx(tfm);

  	struct rctx *rctx = skcipher_request_ctx(req);
  	be128 t = rctx->t;

  	struct skcipher_walk w;

  	__be32 *iv;
  	u32 counter[4];

  	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);

  	if (err)
  		return err;

  	iv = (__be32 *)w.iv;

  	counter[0] = be32_to_cpu(iv[3]);
  	counter[1] = be32_to_cpu(iv[2]);
  	counter[2] = be32_to_cpu(iv[1]);
  	counter[3] = be32_to_cpu(iv[0]);

  	while (w.nbytes) {
  		unsigned int avail = w.nbytes;
  		be128 *wsrc;
  		be128 *wdst;
  
  		wsrc = w.src.virt.addr;
  		wdst = w.dst.virt.addr;

  		do {

  			be128_xor(wdst++, &t, wsrc++);

  			/* T <- I*Key2, using the optimization
  			 * discussed in the specification */

  			be128_xor(&t, &t, &ctx->mulinc[next_index(counter)]);

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

  		if (second_pass && w.nbytes == w.total) {

  			iv[0] = cpu_to_be32(counter[3]);
  			iv[1] = cpu_to_be32(counter[2]);
  			iv[2] = cpu_to_be32(counter[1]);
  			iv[3] = cpu_to_be32(counter[0]);
  		}

  		err = skcipher_walk_done(&w, avail);
  	}

  	return err;
  }

  static int xor_tweak_pre(struct skcipher_request *req)

  {

  	return xor_tweak(req, false);

  }

  static int xor_tweak_post(struct skcipher_request *req)

  {

  	return xor_tweak(req, true);

  }

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

  {
  	struct skcipher_request *req = areq->data;

  	if (!err) {
  		struct rctx *rctx = skcipher_request_ctx(req);
  
  		rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;

  		err = xor_tweak_post(req);

  	}

  
  	skcipher_request_complete(req, err);
  }

  static void init_crypt(struct skcipher_request *req)

  {

  	struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));

  	struct rctx *rctx = skcipher_request_ctx(req);

  	struct skcipher_request *subreq = &rctx->subreq;

  	skcipher_request_set_tfm(subreq, ctx->child);
  	skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req);
  	/* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
  	skcipher_request_set_crypt(subreq, req->dst, req->dst,
  				   req->cryptlen, req->iv);

  	/* calculate first value of T */
  	memcpy(&rctx->t, req->iv, sizeof(rctx->t));

  	/* T <- I*Key2 */
  	gf128mul_64k_bbe(&rctx->t, ctx->table);

  }

  static int encrypt(struct skcipher_request *req)

  {

  	struct rctx *rctx = skcipher_request_ctx(req);
  	struct skcipher_request *subreq = &rctx->subreq;

  	init_crypt(req);
  	return xor_tweak_pre(req) ?:
  		crypto_skcipher_encrypt(subreq) ?:
  		xor_tweak_post(req);

  }
  
  static int decrypt(struct skcipher_request *req)
  {

  	struct rctx *rctx = skcipher_request_ctx(req);
  	struct skcipher_request *subreq = &rctx->subreq;
  
  	init_crypt(req);
  	return xor_tweak_pre(req) ?:
  		crypto_skcipher_decrypt(subreq) ?:
  		xor_tweak_post(req);

  }

  static int init_tfm(struct crypto_skcipher *tfm)

  {

  	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
  	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
  	struct priv *ctx = crypto_skcipher_ctx(tfm);
  	struct crypto_skcipher *cipher;

  	cipher = crypto_spawn_skcipher(spawn);

  	if (IS_ERR(cipher))
  		return PTR_ERR(cipher);

  	ctx->child = cipher;

  
  	crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
  					 sizeof(struct rctx));

  	return 0;
  }

  static void exit_tfm(struct crypto_skcipher *tfm)

  {

  	struct priv *ctx = crypto_skcipher_ctx(tfm);

  	if (ctx->table)
  		gf128mul_free_64k(ctx->table);

  	crypto_free_skcipher(ctx->child);
  }

  static void free_inst(struct skcipher_instance *inst)

  {
  	crypto_drop_skcipher(skcipher_instance_ctx(inst));
  	kfree(inst);

  }

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

  {

  	struct crypto_skcipher_spawn *spawn;
  	struct skcipher_instance *inst;
  	struct crypto_attr_type *algt;
  	struct skcipher_alg *alg;
  	const char *cipher_name;
  	char ecb_name[CRYPTO_MAX_ALG_NAME];

  	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(*spawn), GFP_KERNEL);
  	if (!inst)
  		return -ENOMEM;
  
  	spawn = skcipher_instance_ctx(inst);
  
  	crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
  	err = crypto_grab_skcipher(spawn, cipher_name, 0,
  				   crypto_requires_sync(algt->type,
  							algt->mask));
  	if (err == -ENOENT) {
  		err = -ENAMETOOLONG;
  		if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
  			     cipher_name) >= CRYPTO_MAX_ALG_NAME)
  			goto err_free_inst;
  
  		err = crypto_grab_skcipher(spawn, ecb_name, 0,
  					   crypto_requires_sync(algt->type,
  								algt->mask));
  	}

  	if (err)

  		goto err_free_inst;

  	alg = crypto_skcipher_spawn_alg(spawn);

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

  	if (crypto_skcipher_alg_ivsize(alg))
  		goto err_drop_spawn;

  	err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
  				  &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(ecb_name, cipher_name + 4, sizeof(ecb_name));
  		if (len < 2 || len >= sizeof(ecb_name))
  			goto err_drop_spawn;

  		if (ecb_name[len - 1] != ')')
  			goto err_drop_spawn;

  		ecb_name[len - 1] = 0;

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

  			     "lrw(%s)", ecb_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 = LRW_BLOCK_SIZE;
  	inst->alg.base.cra_alignmask = alg->base.cra_alignmask |

  				       (__alignof__(be128) - 1);

  
  	inst->alg.ivsize = LRW_BLOCK_SIZE;
  	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
  				LRW_BLOCK_SIZE;
  	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
  				LRW_BLOCK_SIZE;
  
  	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_inst;

  
  	err = skcipher_register_instance(tmpl, inst);
  	if (err)
  		goto err_drop_spawn;
  
  out:
  	return err;
  
  err_drop_spawn:
  	crypto_drop_skcipher(spawn);
  err_free_inst:

  	kfree(inst);

  	goto out;

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

  	.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);
  }

  subsys_initcall(crypto_module_init);

  module_exit(crypto_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("LRW block cipher mode");

  MODULE_ALIAS_CRYPTO("lrw");