/*
   * seqiv: Sequence Number IV Generator
   *
   * This generator generates an IV based on a sequence number by xoring it
   * with a salt.  This algorithm is mainly useful for CTR and similar modes.
   *
   * Copyright (c) 2007 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/aead.h>

  #include <crypto/internal/skcipher.h>

  #include <crypto/rng.h>

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

  #include <linux/slab.h>

  #include <linux/spinlock.h>
  #include <linux/string.h>
  
  struct seqiv_ctx {
  	spinlock_t lock;
  	u8 salt[] __attribute__ ((aligned(__alignof__(u32))));
  };
  
  static void seqiv_complete2(struct skcipher_givcrypt_request *req, int err)
  {
  	struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
  	struct crypto_ablkcipher *geniv;
  
  	if (err == -EINPROGRESS)
  		return;
  
  	if (err)
  		goto out;
  
  	geniv = skcipher_givcrypt_reqtfm(req);
  	memcpy(req->creq.info, subreq->info, crypto_ablkcipher_ivsize(geniv));
  
  out:
  	kfree(subreq->info);
  }
  
  static void seqiv_complete(struct crypto_async_request *base, int err)
  {
  	struct skcipher_givcrypt_request *req = base->data;
  
  	seqiv_complete2(req, err);
  	skcipher_givcrypt_complete(req, err);
  }

  static void seqiv_aead_complete2(struct aead_givcrypt_request *req, int err)
  {
  	struct aead_request *subreq = aead_givcrypt_reqctx(req);
  	struct crypto_aead *geniv;
  
  	if (err == -EINPROGRESS)
  		return;
  
  	if (err)
  		goto out;
  
  	geniv = aead_givcrypt_reqtfm(req);
  	memcpy(req->areq.iv, subreq->iv, crypto_aead_ivsize(geniv));
  
  out:
  	kfree(subreq->iv);
  }
  
  static void seqiv_aead_complete(struct crypto_async_request *base, int err)
  {
  	struct aead_givcrypt_request *req = base->data;
  
  	seqiv_aead_complete2(req, err);
  	aead_givcrypt_complete(req, err);
  }
  
  static void seqiv_geniv(struct seqiv_ctx *ctx, u8 *info, u64 seq,
  			unsigned int ivsize)
  {
  	unsigned int len = ivsize;
  
  	if (ivsize > sizeof(u64)) {
  		memset(info, 0, ivsize - sizeof(u64));
  		len = sizeof(u64);
  	}
  	seq = cpu_to_be64(seq);
  	memcpy(info + ivsize - len, &seq, len);
  	crypto_xor(info, ctx->salt, ivsize);
  }

  static int seqiv_givencrypt(struct skcipher_givcrypt_request *req)
  {
  	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
  	struct seqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
  	struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);

  	crypto_completion_t compl;

  	void *data;
  	u8 *info;

  	unsigned int ivsize;

  	int err;
  
  	ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));

  	compl = req->creq.base.complete;

  	data = req->creq.base.data;
  	info = req->creq.info;
  
  	ivsize = crypto_ablkcipher_ivsize(geniv);
  
  	if (unlikely(!IS_ALIGNED((unsigned long)info,
  				 crypto_ablkcipher_alignmask(geniv) + 1))) {
  		info = kmalloc(ivsize, req->creq.base.flags &
  				       CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL:
  								  GFP_ATOMIC);
  		if (!info)
  			return -ENOMEM;

  		compl = seqiv_complete;

  		data = req;
  	}

  	ablkcipher_request_set_callback(subreq, req->creq.base.flags, compl,

  					data);
  	ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst,
  				     req->creq.nbytes, info);

  	seqiv_geniv(ctx, info, req->seq, ivsize);

  	memcpy(req->giv, info, ivsize);
  
  	err = crypto_ablkcipher_encrypt(subreq);
  	if (unlikely(info != req->creq.info))
  		seqiv_complete2(req, err);
  	return err;
  }

  static int seqiv_aead_givencrypt(struct aead_givcrypt_request *req)
  {
  	struct crypto_aead *geniv = aead_givcrypt_reqtfm(req);
  	struct seqiv_ctx *ctx = crypto_aead_ctx(geniv);
  	struct aead_request *areq = &req->areq;
  	struct aead_request *subreq = aead_givcrypt_reqctx(req);

  	crypto_completion_t compl;

  	void *data;
  	u8 *info;
  	unsigned int ivsize;
  	int err;
  
  	aead_request_set_tfm(subreq, aead_geniv_base(geniv));

  	compl = areq->base.complete;

  	data = areq->base.data;
  	info = areq->iv;
  
  	ivsize = crypto_aead_ivsize(geniv);
  
  	if (unlikely(!IS_ALIGNED((unsigned long)info,
  				 crypto_aead_alignmask(geniv) + 1))) {
  		info = kmalloc(ivsize, areq->base.flags &
  				       CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL:
  								  GFP_ATOMIC);
  		if (!info)
  			return -ENOMEM;

  		compl = seqiv_aead_complete;

  		data = req;
  	}

  	aead_request_set_callback(subreq, areq->base.flags, compl, data);

  	aead_request_set_crypt(subreq, areq->src, areq->dst, areq->cryptlen,
  			       info);
  	aead_request_set_assoc(subreq, areq->assoc, areq->assoclen);
  
  	seqiv_geniv(ctx, info, req->seq, ivsize);
  	memcpy(req->giv, info, ivsize);
  
  	err = crypto_aead_encrypt(subreq);
  	if (unlikely(info != areq->iv))
  		seqiv_aead_complete2(req, err);
  	return err;
  }

  static int seqiv_givencrypt_first(struct skcipher_givcrypt_request *req)
  {
  	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
  	struct seqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);

  	int err = 0;

  
  	spin_lock_bh(&ctx->lock);
  	if (crypto_ablkcipher_crt(geniv)->givencrypt != seqiv_givencrypt_first)
  		goto unlock;
  
  	crypto_ablkcipher_crt(geniv)->givencrypt = seqiv_givencrypt;

  	err = crypto_rng_get_bytes(crypto_default_rng, ctx->salt,
  				   crypto_ablkcipher_ivsize(geniv));

  
  unlock:
  	spin_unlock_bh(&ctx->lock);

  	if (err)
  		return err;

  	return seqiv_givencrypt(req);
  }

  static int seqiv_aead_givencrypt_first(struct aead_givcrypt_request *req)
  {
  	struct crypto_aead *geniv = aead_givcrypt_reqtfm(req);
  	struct seqiv_ctx *ctx = crypto_aead_ctx(geniv);

  	int err = 0;

  
  	spin_lock_bh(&ctx->lock);
  	if (crypto_aead_crt(geniv)->givencrypt != seqiv_aead_givencrypt_first)
  		goto unlock;
  
  	crypto_aead_crt(geniv)->givencrypt = seqiv_aead_givencrypt;

  	err = crypto_rng_get_bytes(crypto_default_rng, ctx->salt,
  				   crypto_aead_ivsize(geniv));

  
  unlock:
  	spin_unlock_bh(&ctx->lock);

  	if (err)
  		return err;

  	return seqiv_aead_givencrypt(req);
  }

  static int seqiv_init(struct crypto_tfm *tfm)
  {
  	struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
  	struct seqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
  
  	spin_lock_init(&ctx->lock);
  
  	tfm->crt_ablkcipher.reqsize = sizeof(struct ablkcipher_request);
  
  	return skcipher_geniv_init(tfm);
  }

  static int seqiv_aead_init(struct crypto_tfm *tfm)
  {
  	struct crypto_aead *geniv = __crypto_aead_cast(tfm);
  	struct seqiv_ctx *ctx = crypto_aead_ctx(geniv);
  
  	spin_lock_init(&ctx->lock);
  
  	tfm->crt_aead.reqsize = sizeof(struct aead_request);
  
  	return aead_geniv_init(tfm);
  }

  static struct crypto_template seqiv_tmpl;

  static struct crypto_instance *seqiv_ablkcipher_alloc(struct rtattr **tb)

  {
  	struct crypto_instance *inst;
  
  	inst = skcipher_geniv_alloc(&seqiv_tmpl, tb, 0, 0);

  	if (IS_ERR(inst))
  		goto out;
  
  	inst->alg.cra_ablkcipher.givencrypt = seqiv_givencrypt_first;
  
  	inst->alg.cra_init = seqiv_init;
  	inst->alg.cra_exit = skcipher_geniv_exit;

  	inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;
  
  out:
  	return inst;
  }

  static struct crypto_instance *seqiv_aead_alloc(struct rtattr **tb)
  {
  	struct crypto_instance *inst;
  
  	inst = aead_geniv_alloc(&seqiv_tmpl, tb, 0, 0);
  
  	if (IS_ERR(inst))
  		goto out;
  
  	inst->alg.cra_aead.givencrypt = seqiv_aead_givencrypt_first;
  
  	inst->alg.cra_init = seqiv_aead_init;
  	inst->alg.cra_exit = aead_geniv_exit;
  
  	inst->alg.cra_ctxsize = inst->alg.cra_aead.ivsize;
  
  out:
  	return inst;
  }
  
  static struct crypto_instance *seqiv_alloc(struct rtattr **tb)
  {
  	struct crypto_attr_type *algt;
  	struct crypto_instance *inst;
  	int err;
  
  	algt = crypto_get_attr_type(tb);

  	if (IS_ERR(algt))

  		return ERR_CAST(algt);

  	err = crypto_get_default_rng();
  	if (err)
  		return ERR_PTR(err);

  	if ((algt->type ^ CRYPTO_ALG_TYPE_AEAD) & CRYPTO_ALG_TYPE_MASK)
  		inst = seqiv_ablkcipher_alloc(tb);
  	else
  		inst = seqiv_aead_alloc(tb);
  
  	if (IS_ERR(inst))

  		goto put_rng;

  
  	inst->alg.cra_alignmask |= __alignof__(u32) - 1;
  	inst->alg.cra_ctxsize += sizeof(struct seqiv_ctx);
  
  out:
  	return inst;

  
  put_rng:
  	crypto_put_default_rng();
  	goto out;

  }
  
  static void seqiv_free(struct crypto_instance *inst)
  {
  	if ((inst->alg.cra_flags ^ CRYPTO_ALG_TYPE_AEAD) & CRYPTO_ALG_TYPE_MASK)
  		skcipher_geniv_free(inst);
  	else
  		aead_geniv_free(inst);

  	crypto_put_default_rng();

  }

  static struct crypto_template seqiv_tmpl = {
  	.name = "seqiv",
  	.alloc = seqiv_alloc,

  	.free = seqiv_free,

  	.module = THIS_MODULE,
  };
  
  static int __init seqiv_module_init(void)
  {
  	return crypto_register_template(&seqiv_tmpl);
  }
  
  static void __exit seqiv_module_exit(void)
  {
  	crypto_unregister_template(&seqiv_tmpl);
  }
  
  module_init(seqiv_module_init);
  module_exit(seqiv_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("Sequence Number IV Generator");