/*
   * chainiv: Chain IV Generator
   *
   * Generate IVs simply be using the last block of the previous encryption.
   * This is mainly useful for CBC with a synchronous algorithm.
   *
   * 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/skcipher.h>
  #include <crypto/rng.h>
  #include <crypto/crypto_wq.h>
  #include <linux/err.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/spinlock.h>
  #include <linux/string.h>
  #include <linux/workqueue.h>
  
  enum {
  	CHAINIV_STATE_INUSE = 0,
  };
  
  struct chainiv_ctx {
  	spinlock_t lock;
  	char iv[];
  };
  
  struct async_chainiv_ctx {
  	unsigned long state;
  
  	spinlock_t lock;
  	int err;
  
  	struct crypto_queue queue;
  	struct work_struct postponed;
  
  	char iv[];
  };
  
  static int chainiv_givencrypt(struct skcipher_givcrypt_request *req)
  {
  	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
  	struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
  	struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
  	unsigned int ivsize;
  	int err;
  
  	ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
  	ablkcipher_request_set_callback(subreq, req->creq.base.flags &
  						~CRYPTO_TFM_REQ_MAY_SLEEP,
  					req->creq.base.complete,
  					req->creq.base.data);
  	ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst,
  				     req->creq.nbytes, req->creq.info);
  
  	spin_lock_bh(&ctx->lock);
  
  	ivsize = crypto_ablkcipher_ivsize(geniv);
  
  	memcpy(req->giv, ctx->iv, ivsize);
  	memcpy(subreq->info, ctx->iv, ivsize);
  
  	err = crypto_ablkcipher_encrypt(subreq);
  	if (err)
  		goto unlock;
  
  	memcpy(ctx->iv, subreq->info, ivsize);
  
  unlock:
  	spin_unlock_bh(&ctx->lock);
  
  	return err;
  }
  
  static int chainiv_givencrypt_first(struct skcipher_givcrypt_request *req)
  {
  	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
  	struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
  	int err = 0;
  
  	spin_lock_bh(&ctx->lock);
  	if (crypto_ablkcipher_crt(geniv)->givencrypt !=
  	    chainiv_givencrypt_first)
  		goto unlock;
  
  	crypto_ablkcipher_crt(geniv)->givencrypt = chainiv_givencrypt;
  	err = crypto_rng_get_bytes(crypto_default_rng, ctx->iv,
  				   crypto_ablkcipher_ivsize(geniv));
  
  unlock:
  	spin_unlock_bh(&ctx->lock);
  
  	if (err)
  		return err;
  
  	return chainiv_givencrypt(req);
  }
  
  static int chainiv_init_common(struct crypto_tfm *tfm)
  {
  	tfm->crt_ablkcipher.reqsize = sizeof(struct ablkcipher_request);
  
  	return skcipher_geniv_init(tfm);
  }
  
  static int chainiv_init(struct crypto_tfm *tfm)
  {
  	struct chainiv_ctx *ctx = crypto_tfm_ctx(tfm);
  
  	spin_lock_init(&ctx->lock);
  
  	return chainiv_init_common(tfm);
  }
  
  static int async_chainiv_schedule_work(struct async_chainiv_ctx *ctx)
  {
  	int queued;
  	int err = ctx->err;
  
  	if (!ctx->queue.qlen) {
  		smp_mb__before_clear_bit();
  		clear_bit(CHAINIV_STATE_INUSE, &ctx->state);
  
  		if (!ctx->queue.qlen ||
  		    test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
  			goto out;
  	}
  
  	queued = queue_work(kcrypto_wq, &ctx->postponed);
  	BUG_ON(!queued);
  
  out:
  	return err;
  }
  
  static int async_chainiv_postpone_request(struct skcipher_givcrypt_request *req)
  {
  	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
  	struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
  	int err;
  
  	spin_lock_bh(&ctx->lock);
  	err = skcipher_enqueue_givcrypt(&ctx->queue, req);
  	spin_unlock_bh(&ctx->lock);
  
  	if (test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
  		return err;
  
  	ctx->err = err;
  	return async_chainiv_schedule_work(ctx);
  }
  
  static int async_chainiv_givencrypt_tail(struct skcipher_givcrypt_request *req)
  {
  	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
  	struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
  	struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
  	unsigned int ivsize = crypto_ablkcipher_ivsize(geniv);
  
  	memcpy(req->giv, ctx->iv, ivsize);
  	memcpy(subreq->info, ctx->iv, ivsize);
  
  	ctx->err = crypto_ablkcipher_encrypt(subreq);
  	if (ctx->err)
  		goto out;
  
  	memcpy(ctx->iv, subreq->info, ivsize);
  
  out:
  	return async_chainiv_schedule_work(ctx);
  }
  
  static int async_chainiv_givencrypt(struct skcipher_givcrypt_request *req)
  {
  	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
  	struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
  	struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
  
  	ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
  	ablkcipher_request_set_callback(subreq, req->creq.base.flags,
  					req->creq.base.complete,
  					req->creq.base.data);
  	ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst,
  				     req->creq.nbytes, req->creq.info);
  
  	if (test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
  		goto postpone;
  
  	if (ctx->queue.qlen) {
  		clear_bit(CHAINIV_STATE_INUSE, &ctx->state);
  		goto postpone;
  	}
  
  	return async_chainiv_givencrypt_tail(req);
  
  postpone:
  	return async_chainiv_postpone_request(req);
  }
  
  static int async_chainiv_givencrypt_first(struct skcipher_givcrypt_request *req)
  {
  	struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
  	struct async_chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
  	int err = 0;
  
  	if (test_and_set_bit(CHAINIV_STATE_INUSE, &ctx->state))
  		goto out;
  
  	if (crypto_ablkcipher_crt(geniv)->givencrypt !=
  	    async_chainiv_givencrypt_first)
  		goto unlock;
  
  	crypto_ablkcipher_crt(geniv)->givencrypt = async_chainiv_givencrypt;
  	err = crypto_rng_get_bytes(crypto_default_rng, ctx->iv,
  				   crypto_ablkcipher_ivsize(geniv));
  
  unlock:
  	clear_bit(CHAINIV_STATE_INUSE, &ctx->state);
  
  	if (err)
  		return err;
  
  out:
  	return async_chainiv_givencrypt(req);
  }
  
  static void async_chainiv_do_postponed(struct work_struct *work)
  {
  	struct async_chainiv_ctx *ctx = container_of(work,
  						     struct async_chainiv_ctx,
  						     postponed);
  	struct skcipher_givcrypt_request *req;
  	struct ablkcipher_request *subreq;
  	int err;
  
  	/* Only handle one request at a time to avoid hogging keventd. */
  	spin_lock_bh(&ctx->lock);
  	req = skcipher_dequeue_givcrypt(&ctx->queue);
  	spin_unlock_bh(&ctx->lock);
  
  	if (!req) {
  		async_chainiv_schedule_work(ctx);
  		return;
  	}
  
  	subreq = skcipher_givcrypt_reqctx(req);
  	subreq->base.flags |= CRYPTO_TFM_REQ_MAY_SLEEP;
  
  	err = async_chainiv_givencrypt_tail(req);
  
  	local_bh_disable();
  	skcipher_givcrypt_complete(req, err);
  	local_bh_enable();
  }
  
  static int async_chainiv_init(struct crypto_tfm *tfm)
  {
  	struct async_chainiv_ctx *ctx = crypto_tfm_ctx(tfm);
  
  	spin_lock_init(&ctx->lock);
  
  	crypto_init_queue(&ctx->queue, 100);
  	INIT_WORK(&ctx->postponed, async_chainiv_do_postponed);
  
  	return chainiv_init_common(tfm);
  }
  
  static void async_chainiv_exit(struct crypto_tfm *tfm)
  {
  	struct async_chainiv_ctx *ctx = crypto_tfm_ctx(tfm);
  
  	BUG_ON(test_bit(CHAINIV_STATE_INUSE, &ctx->state) || ctx->queue.qlen);
  
  	skcipher_geniv_exit(tfm);
  }
  
  static struct crypto_template chainiv_tmpl;
  
  static struct crypto_instance *chainiv_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);
  
  	inst = skcipher_geniv_alloc(&chainiv_tmpl, tb, 0, 0);
  	if (IS_ERR(inst))
  		goto put_rng;
  
  	inst->alg.cra_ablkcipher.givencrypt = chainiv_givencrypt_first;
  
  	inst->alg.cra_init = chainiv_init;
  	inst->alg.cra_exit = skcipher_geniv_exit;
  
  	inst->alg.cra_ctxsize = sizeof(struct chainiv_ctx);
  
  	if (!crypto_requires_sync(algt->type, algt->mask)) {
  		inst->alg.cra_flags |= CRYPTO_ALG_ASYNC;
  
  		inst->alg.cra_ablkcipher.givencrypt =
  			async_chainiv_givencrypt_first;
  
  		inst->alg.cra_init = async_chainiv_init;
  		inst->alg.cra_exit = async_chainiv_exit;
  
  		inst->alg.cra_ctxsize = sizeof(struct async_chainiv_ctx);
  	}
  
  	inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize;
  
  out:
  	return inst;
  
  put_rng:
  	crypto_put_default_rng();
  	goto out;
  }
  
  static void chainiv_free(struct crypto_instance *inst)
  {
  	skcipher_geniv_free(inst);
  	crypto_put_default_rng();
  }
  
  static struct crypto_template chainiv_tmpl = {
  	.name = "chainiv",
  	.alloc = chainiv_alloc,
  	.free = chainiv_free,
  	.module = THIS_MODULE,
  };
  
  static int __init chainiv_module_init(void)
  {
  	return crypto_register_template(&chainiv_tmpl);
  }
  
  static void chainiv_module_exit(void)
  {
  	crypto_unregister_template(&chainiv_tmpl);
  }
  
  module_init(chainiv_module_init);
  module_exit(chainiv_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("Chain IV Generator");