/*
   * CTR: Counter mode
   *
   * (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>
   *
   * 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/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/random.h>
  #include <linux/scatterlist.h>
  #include <linux/slab.h>
  
  struct crypto_ctr_ctx {
  	struct crypto_cipher *child;
  };
  
  struct crypto_rfc3686_ctx {
  	struct crypto_ablkcipher *child;
  	u8 nonce[CTR_RFC3686_NONCE_SIZE];
  };
  
  struct crypto_rfc3686_req_ctx {
  	u8 iv[CTR_RFC3686_BLOCK_SIZE];
  	struct ablkcipher_request subreq CRYPTO_MINALIGN_ATTR;
  };
  
  static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key,
  			     unsigned int keylen)
  {
  	struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(parent);
  	struct crypto_cipher *child = ctx->child;
  	int err;
  
  	crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  	crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
  				CRYPTO_TFM_REQ_MASK);
  	err = crypto_cipher_setkey(child, key, keylen);
  	crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
  			     CRYPTO_TFM_RES_MASK);
  
  	return err;
  }
  
  static void crypto_ctr_crypt_final(struct blkcipher_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[bsize + 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(keystream, src, nbytes);
  	memcpy(dst, keystream, nbytes);
  
  	crypto_inc(ctrblk, bsize);
  }
  
  static int crypto_ctr_crypt_segment(struct blkcipher_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 blkcipher_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[bsize + 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 blkcipher_desc *desc,
  			      struct scatterlist *dst, struct scatterlist *src,
  			      unsigned int nbytes)
  {
  	struct blkcipher_walk walk;
  	struct crypto_blkcipher *tfm = desc->tfm;
  	struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm);
  	struct crypto_cipher *child = ctx->child;
  	unsigned int bsize = crypto_cipher_blocksize(child);
  	int err;
  
  	blkcipher_walk_init(&walk, dst, src, nbytes);
  	err = blkcipher_walk_virt_block(desc, &walk, bsize);
  
  	while (walk.nbytes >= bsize) {
  		if (walk.src.virt.addr == walk.dst.virt.addr)
  			nbytes = crypto_ctr_crypt_inplace(&walk, child);
  		else
  			nbytes = crypto_ctr_crypt_segment(&walk, child);
  
  		err = blkcipher_walk_done(desc, &walk, nbytes);
  	}
  
  	if (walk.nbytes) {
  		crypto_ctr_crypt_final(&walk, child);
  		err = blkcipher_walk_done(desc, &walk, 0);
  	}
  
  	return err;
  }
  
  static int crypto_ctr_init_tfm(struct crypto_tfm *tfm)
  {
  	struct crypto_instance *inst = (void *)tfm->__crt_alg;
  	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
  	struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
  	struct crypto_cipher *cipher;
  
  	cipher = crypto_spawn_cipher(spawn);
  	if (IS_ERR(cipher))
  		return PTR_ERR(cipher);
  
  	ctx->child = cipher;
  
  	return 0;
  }
  
  static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
  {
  	struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
  
  	crypto_free_cipher(ctx->child);
  }
  
  static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
  {
  	struct crypto_instance *inst;
  	struct crypto_alg *alg;
  	int err;
  
  	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
  	if (err)
  		return ERR_PTR(err);
  
  	alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
  				  CRYPTO_ALG_TYPE_MASK);
  	if (IS_ERR(alg))
  		return ERR_CAST(alg);
  
  	/* Block size must be >= 4 bytes. */
  	err = -EINVAL;
  	if (alg->cra_blocksize < 4)
  		goto out_put_alg;
  
  	/* If this is false we'd fail the alignment of crypto_inc. */
  	if (alg->cra_blocksize % 4)
  		goto out_put_alg;
  
  	inst = crypto_alloc_instance("ctr", alg);
  	if (IS_ERR(inst))
  		goto out;
  
  	inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
  	inst->alg.cra_priority = alg->cra_priority;
  	inst->alg.cra_blocksize = 1;
  	inst->alg.cra_alignmask = alg->cra_alignmask | (__alignof__(u32) - 1);
  	inst->alg.cra_type = &crypto_blkcipher_type;
  
  	inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
  	inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
  	inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
  
  	inst->alg.cra_ctxsize = sizeof(struct crypto_ctr_ctx);
  
  	inst->alg.cra_init = crypto_ctr_init_tfm;
  	inst->alg.cra_exit = crypto_ctr_exit_tfm;
  
  	inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
  	inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
  	inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;
  
  	inst->alg.cra_blkcipher.geniv = "chainiv";
  
  out:
  	crypto_mod_put(alg);
  	return inst;
  
  out_put_alg:
  	inst = ERR_PTR(err);
  	goto out;
  }
  
  static void crypto_ctr_free(struct crypto_instance *inst)
  {
  	crypto_drop_spawn(crypto_instance_ctx(inst));
  	kfree(inst);
  }
  
  static struct crypto_template crypto_ctr_tmpl = {
  	.name = "ctr",
  	.alloc = crypto_ctr_alloc,
  	.free = crypto_ctr_free,
  	.module = THIS_MODULE,
  };
  
  static int crypto_rfc3686_setkey(struct crypto_ablkcipher *parent,
  				 const u8 *key, unsigned int keylen)
  {
  	struct crypto_rfc3686_ctx *ctx = crypto_ablkcipher_ctx(parent);
  	struct crypto_ablkcipher *child = ctx->child;
  	int err;
  
  	/* 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_ablkcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  	crypto_ablkcipher_set_flags(child, crypto_ablkcipher_get_flags(parent) &
  				    CRYPTO_TFM_REQ_MASK);
  	err = crypto_ablkcipher_setkey(child, key, keylen);
  	crypto_ablkcipher_set_flags(parent, crypto_ablkcipher_get_flags(child) &
  				    CRYPTO_TFM_RES_MASK);
  
  	return err;
  }
  
  static int crypto_rfc3686_crypt(struct ablkcipher_request *req)
  {
  	struct crypto_ablkcipher *tfm = crypto_ablkcipher_reqtfm(req);
  	struct crypto_rfc3686_ctx *ctx = crypto_ablkcipher_ctx(tfm);
  	struct crypto_ablkcipher *child = ctx->child;
  	unsigned long align = crypto_ablkcipher_alignmask(tfm);
  	struct crypto_rfc3686_req_ctx *rctx =
  		(void *)PTR_ALIGN((u8 *)ablkcipher_request_ctx(req), align + 1);
  	struct ablkcipher_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->info, CTR_RFC3686_IV_SIZE);
  
  	/* initialize counter portion of counter block */
  	*(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
  		cpu_to_be32(1);
  
  	ablkcipher_request_set_tfm(subreq, child);
  	ablkcipher_request_set_callback(subreq, req->base.flags,
  					req->base.complete, req->base.data);
  	ablkcipher_request_set_crypt(subreq, req->src, req->dst, req->nbytes,
  				     iv);
  
  	return crypto_ablkcipher_encrypt(subreq);
  }
  
  static int crypto_rfc3686_init_tfm(struct crypto_tfm *tfm)
  {
  	struct crypto_instance *inst = (void *)tfm->__crt_alg;
  	struct crypto_skcipher_spawn *spawn = crypto_instance_ctx(inst);
  	struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(tfm);
  	struct crypto_ablkcipher *cipher;
  	unsigned long align;
  
  	cipher = crypto_spawn_skcipher(spawn);
  	if (IS_ERR(cipher))
  		return PTR_ERR(cipher);
  
  	ctx->child = cipher;
  
  	align = crypto_tfm_alg_alignmask(tfm);
  	align &= ~(crypto_tfm_ctx_alignment() - 1);
  	tfm->crt_ablkcipher.reqsize = align +
  		sizeof(struct crypto_rfc3686_req_ctx) +
  		crypto_ablkcipher_reqsize(cipher);
  
  	return 0;
  }
  
  static void crypto_rfc3686_exit_tfm(struct crypto_tfm *tfm)
  {
  	struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(tfm);
  
  	crypto_free_ablkcipher(ctx->child);
  }
  
  static struct crypto_instance *crypto_rfc3686_alloc(struct rtattr **tb)
  {
  	struct crypto_attr_type *algt;
  	struct crypto_instance *inst;
  	struct crypto_alg *alg;
  	struct crypto_skcipher_spawn *spawn;
  	const char *cipher_name;
  	int err;
  
  	algt = crypto_get_attr_type(tb);
  	if (IS_ERR(algt))
  		return ERR_CAST(algt);
  
  	if ((algt->type ^ CRYPTO_ALG_TYPE_BLKCIPHER) & algt->mask)
  		return ERR_PTR(-EINVAL);
  
  	cipher_name = crypto_attr_alg_name(tb[1]);
  	if (IS_ERR(cipher_name))
  		return ERR_CAST(cipher_name);
  
  	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
  	if (!inst)
  		return ERR_PTR(-ENOMEM);
  
  	spawn = crypto_instance_ctx(inst);
  
  	crypto_set_skcipher_spawn(spawn, inst);
  	err = crypto_grab_skcipher(spawn, cipher_name, 0,
  				   crypto_requires_sync(algt->type,
  							algt->mask));
  	if (err)
  		goto err_free_inst;
  
  	alg = crypto_skcipher_spawn_alg(spawn);
  
  	/* We only support 16-byte blocks. */
  	err = -EINVAL;
  	if (alg->cra_ablkcipher.ivsize != CTR_RFC3686_BLOCK_SIZE)
  		goto err_drop_spawn;
  
  	/* Not a stream cipher? */
  	if (alg->cra_blocksize != 1)
  		goto err_drop_spawn;
  
  	err = -ENAMETOOLONG;
  	if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME, "rfc3686(%s)",
  		     alg->cra_name) >= CRYPTO_MAX_ALG_NAME)
  		goto err_drop_spawn;
  	if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
  		     "rfc3686(%s)", alg->cra_driver_name) >=
  			CRYPTO_MAX_ALG_NAME)
  		goto err_drop_spawn;
  
  	inst->alg.cra_priority = alg->cra_priority;
  	inst->alg.cra_blocksize = 1;
  	inst->alg.cra_alignmask = alg->cra_alignmask;
  
  	inst->alg.cra_flags = CRYPTO_ALG_TYPE_ABLKCIPHER |
  			      (alg->cra_flags & CRYPTO_ALG_ASYNC);
  	inst->alg.cra_type = &crypto_ablkcipher_type;
  
  	inst->alg.cra_ablkcipher.ivsize = CTR_RFC3686_IV_SIZE;
  	inst->alg.cra_ablkcipher.min_keysize =
  		alg->cra_ablkcipher.min_keysize + CTR_RFC3686_NONCE_SIZE;
  	inst->alg.cra_ablkcipher.max_keysize =
  		alg->cra_ablkcipher.max_keysize + CTR_RFC3686_NONCE_SIZE;
  
  	inst->alg.cra_ablkcipher.geniv = "seqiv";
  
  	inst->alg.cra_ablkcipher.setkey = crypto_rfc3686_setkey;
  	inst->alg.cra_ablkcipher.encrypt = crypto_rfc3686_crypt;
  	inst->alg.cra_ablkcipher.decrypt = crypto_rfc3686_crypt;
  
  	inst->alg.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);
  
  	inst->alg.cra_init = crypto_rfc3686_init_tfm;
  	inst->alg.cra_exit = crypto_rfc3686_exit_tfm;
  
  	return inst;
  
  err_drop_spawn:
  	crypto_drop_skcipher(spawn);
  err_free_inst:
  	kfree(inst);
  	return ERR_PTR(err);
  }
  
  static void crypto_rfc3686_free(struct crypto_instance *inst)
  {
  	struct crypto_skcipher_spawn *spawn = crypto_instance_ctx(inst);
  
  	crypto_drop_skcipher(spawn);
  	kfree(inst);
  }
  
  static struct crypto_template crypto_rfc3686_tmpl = {
  	.name = "rfc3686",
  	.alloc = crypto_rfc3686_alloc,
  	.free = crypto_rfc3686_free,
  	.module = THIS_MODULE,
  };
  
  static int __init crypto_ctr_module_init(void)
  {
  	int err;
  
  	err = crypto_register_template(&crypto_ctr_tmpl);
  	if (err)
  		goto out;
  
  	err = crypto_register_template(&crypto_rfc3686_tmpl);
  	if (err)
  		goto out_drop_ctr;
  
  out:
  	return err;
  
  out_drop_ctr:
  	crypto_unregister_template(&crypto_ctr_tmpl);
  	goto out;
  }
  
  static void __exit crypto_ctr_module_exit(void)
  {
  	crypto_unregister_template(&crypto_rfc3686_tmpl);
  	crypto_unregister_template(&crypto_ctr_tmpl);
  }
  
  module_init(crypto_ctr_module_init);
  module_exit(crypto_ctr_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("CTR Counter block mode");
  MODULE_ALIAS("rfc3686");