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

  /*
   * CTR: Counter mode
   *
   * (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>

   */
  
  #include <crypto/algapi.h>

  #include <crypto/ctr.h>

  #include <crypto/internal/skcipher.h>

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

  #include <linux/slab.h>

  struct crypto_rfc3686_ctx {

  	struct crypto_skcipher *child;

  	u8 nonce[CTR_RFC3686_NONCE_SIZE];

  };

  struct crypto_rfc3686_req_ctx {
  	u8 iv[CTR_RFC3686_BLOCK_SIZE];

  	struct skcipher_request subreq CRYPTO_MINALIGN_ATTR;

  };

  static void crypto_ctr_crypt_final(struct skcipher_walk *walk,

  				   struct crypto_cipher *tfm)

  {
  	unsigned int bsize = crypto_cipher_blocksize(tfm);

  	unsigned long alignmask = crypto_cipher_alignmask(tfm);
  	u8 *ctrblk = walk->iv;

  	u8 tmp[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];

  	u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);

  	u8 *src = walk->src.virt.addr;
  	u8 *dst = walk->dst.virt.addr;
  	unsigned int nbytes = walk->nbytes;
  
  	crypto_cipher_encrypt_one(tfm, keystream, ctrblk);

  	crypto_xor_cpy(dst, keystream, src, nbytes);

  
  	crypto_inc(ctrblk, bsize);

  }

  static int crypto_ctr_crypt_segment(struct skcipher_walk *walk,

  				    struct crypto_cipher *tfm)

  {
  	void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  		   crypto_cipher_alg(tfm)->cia_encrypt;
  	unsigned int bsize = crypto_cipher_blocksize(tfm);

  	u8 *ctrblk = walk->iv;

  	u8 *src = walk->src.virt.addr;
  	u8 *dst = walk->dst.virt.addr;
  	unsigned int nbytes = walk->nbytes;
  
  	do {
  		/* create keystream */

  		fn(crypto_cipher_tfm(tfm), dst, ctrblk);
  		crypto_xor(dst, src, bsize);

  
  		/* increment counter in counterblock */

  		crypto_inc(ctrblk, bsize);

  		src += bsize;
  		dst += bsize;

  	} while ((nbytes -= bsize) >= bsize);

  	return nbytes;

  }

  static int crypto_ctr_crypt_inplace(struct skcipher_walk *walk,

  				    struct crypto_cipher *tfm)

  {
  	void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  		   crypto_cipher_alg(tfm)->cia_encrypt;
  	unsigned int bsize = crypto_cipher_blocksize(tfm);

  	unsigned long alignmask = crypto_cipher_alignmask(tfm);

  	unsigned int nbytes = walk->nbytes;

  	u8 *ctrblk = walk->iv;

  	u8 *src = walk->src.virt.addr;

  	u8 tmp[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];

  	u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);

  
  	do {
  		/* create keystream */
  		fn(crypto_cipher_tfm(tfm), keystream, ctrblk);

  		crypto_xor(src, keystream, bsize);

  
  		/* increment counter in counterblock */

  		crypto_inc(ctrblk, bsize);

  		src += bsize;

  	} while ((nbytes -= bsize) >= bsize);

  	return nbytes;

  }

  static int crypto_ctr_crypt(struct skcipher_request *req)

  {

  	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  	struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
  	const unsigned int bsize = crypto_cipher_blocksize(cipher);
  	struct skcipher_walk walk;
  	unsigned int nbytes;

  	int err;

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

  	while (walk.nbytes >= bsize) {

  		if (walk.src.virt.addr == walk.dst.virt.addr)

  			nbytes = crypto_ctr_crypt_inplace(&walk, cipher);

  		else

  			nbytes = crypto_ctr_crypt_segment(&walk, cipher);

  		err = skcipher_walk_done(&walk, nbytes);

  	}

  
  	if (walk.nbytes) {

  		crypto_ctr_crypt_final(&walk, cipher);
  		err = skcipher_walk_done(&walk, 0);

  	}

  	return err;
  }

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

  {

  	struct skcipher_instance *inst;

  	struct crypto_alg *alg;

  	int err;

  	inst = skcipher_alloc_instance_simple(tmpl, tb);

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

  	alg = skcipher_ialg_simple(inst);

  	/* Block size must be >= 4 bytes. */

  	err = -EINVAL;

  	if (alg->cra_blocksize < 4)

  		goto out_free_inst;

  	/* If this is false we'd fail the alignment of crypto_inc. */

  	if (alg->cra_blocksize % 4)

  		goto out_free_inst;

  	/* CTR mode is a stream cipher. */
  	inst->alg.base.cra_blocksize = 1;

  	/*
  	 * To simplify the implementation, configure the skcipher walk to only
  	 * give a partial block at the very end, never earlier.
  	 */
  	inst->alg.chunksize = alg->cra_blocksize;

  	inst->alg.encrypt = crypto_ctr_crypt;
  	inst->alg.decrypt = crypto_ctr_crypt;

  	err = skcipher_register_instance(tmpl, inst);

  	if (err) {

  out_free_inst:

  		inst->free(inst);
  	}

  	return err;

  }

  static int crypto_rfc3686_setkey(struct crypto_skcipher *parent,

  				 const u8 *key, unsigned int keylen)

  {

  	struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(parent);
  	struct crypto_skcipher *child = ctx->child;

  
  	/* the nonce is stored in bytes at end of key */
  	if (keylen < CTR_RFC3686_NONCE_SIZE)
  		return -EINVAL;
  
  	memcpy(ctx->nonce, key + (keylen - CTR_RFC3686_NONCE_SIZE),
  	       CTR_RFC3686_NONCE_SIZE);
  
  	keylen -= CTR_RFC3686_NONCE_SIZE;

  	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);

  }

  static int crypto_rfc3686_crypt(struct skcipher_request *req)

  {

  	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  	struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
  	struct crypto_skcipher *child = ctx->child;
  	unsigned long align = crypto_skcipher_alignmask(tfm);

  	struct crypto_rfc3686_req_ctx *rctx =

  		(void *)PTR_ALIGN((u8 *)skcipher_request_ctx(req), align + 1);
  	struct skcipher_request *subreq = &rctx->subreq;

  	u8 *iv = rctx->iv;

  
  	/* set up counter block */
  	memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);

  	memcpy(iv + CTR_RFC3686_NONCE_SIZE, req->iv, CTR_RFC3686_IV_SIZE);

  
  	/* initialize counter portion of counter block */
  	*(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
  		cpu_to_be32(1);

  	skcipher_request_set_tfm(subreq, child);
  	skcipher_request_set_callback(subreq, req->base.flags,
  				      req->base.complete, req->base.data);
  	skcipher_request_set_crypt(subreq, req->src, req->dst,
  				   req->cryptlen, iv);

  	return crypto_skcipher_encrypt(subreq);

  }

  static int crypto_rfc3686_init_tfm(struct crypto_skcipher *tfm)

  {

  	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
  	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
  	struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
  	struct crypto_skcipher *cipher;

  	unsigned long align;

  	unsigned int reqsize;

  	cipher = crypto_spawn_skcipher(spawn);

  	if (IS_ERR(cipher))
  		return PTR_ERR(cipher);
  
  	ctx->child = cipher;

  	align = crypto_skcipher_alignmask(tfm);

  	align &= ~(crypto_tfm_ctx_alignment() - 1);

  	reqsize = align + sizeof(struct crypto_rfc3686_req_ctx) +
  		  crypto_skcipher_reqsize(cipher);
  	crypto_skcipher_set_reqsize(tfm, reqsize);

  	return 0;
  }

  static void crypto_rfc3686_exit_tfm(struct crypto_skcipher *tfm)

  {

  	struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
  
  	crypto_free_skcipher(ctx->child);
  }

  static void crypto_rfc3686_free(struct skcipher_instance *inst)
  {
  	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
  
  	crypto_drop_skcipher(spawn);
  	kfree(inst);

  }

  static int crypto_rfc3686_create(struct crypto_template *tmpl,
  				 struct rtattr **tb)

  {

  	struct skcipher_instance *inst;
  	struct skcipher_alg *alg;

  	struct crypto_skcipher_spawn *spawn;

  	u32 mask;

  	int err;

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

  	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
  	if (!inst)

  		return -ENOMEM;

  	spawn = skcipher_instance_ctx(inst);

  	err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),

  				   crypto_attr_alg_name(tb[1]), 0, mask);

  	if (err)
  		goto err_free_inst;

  	alg = crypto_spawn_skcipher_alg(spawn);

  	/* We only support 16-byte blocks. */
  	err = -EINVAL;

  	if (crypto_skcipher_alg_ivsize(alg) != CTR_RFC3686_BLOCK_SIZE)

  		goto err_free_inst;

  
  	/* Not a stream cipher? */

  	if (alg->base.cra_blocksize != 1)

  		goto err_free_inst;

  	err = -ENAMETOOLONG;

  	if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
  		     "rfc3686(%s)", alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)

  		goto err_free_inst;

  	if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
  		     "rfc3686(%s)", alg->base.cra_driver_name) >=
  	    CRYPTO_MAX_ALG_NAME)

  		goto err_free_inst;

  	inst->alg.base.cra_priority = alg->base.cra_priority;
  	inst->alg.base.cra_blocksize = 1;
  	inst->alg.base.cra_alignmask = alg->base.cra_alignmask;

  	inst->alg.ivsize = CTR_RFC3686_IV_SIZE;
  	inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
  	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
  				CTR_RFC3686_NONCE_SIZE;
  	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
  				CTR_RFC3686_NONCE_SIZE;

  	inst->alg.setkey = crypto_rfc3686_setkey;
  	inst->alg.encrypt = crypto_rfc3686_crypt;
  	inst->alg.decrypt = crypto_rfc3686_crypt;

  	inst->alg.base.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);

  	inst->alg.init = crypto_rfc3686_init_tfm;
  	inst->alg.exit = crypto_rfc3686_exit_tfm;

  	inst->free = crypto_rfc3686_free;

  	err = skcipher_register_instance(tmpl, inst);

  	if (err) {

  err_free_inst:

  		crypto_rfc3686_free(inst);
  	}
  	return err;

  }

  static struct crypto_template crypto_ctr_tmpls[] = {
  	{
  		.name = "ctr",
  		.create = crypto_ctr_create,
  		.module = THIS_MODULE,
  	}, {
  		.name = "rfc3686",
  		.create = crypto_rfc3686_create,
  		.module = THIS_MODULE,
  	},

  };

  static int __init crypto_ctr_module_init(void)
  {

  	return crypto_register_templates(crypto_ctr_tmpls,
  					 ARRAY_SIZE(crypto_ctr_tmpls));

  }
  
  static void __exit crypto_ctr_module_exit(void)
  {

  	crypto_unregister_templates(crypto_ctr_tmpls,
  				    ARRAY_SIZE(crypto_ctr_tmpls));

  }

  subsys_initcall(crypto_ctr_module_init);

  module_exit(crypto_ctr_module_exit);
  
  MODULE_LICENSE("GPL");

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

  MODULE_ALIAS_CRYPTO("rfc3686");

  MODULE_ALIAS_CRYPTO("ctr");