/*
   * Cryptographic API.
   *
   * HMAC: Keyed-Hashing for Message Authentication (RFC2104).
   *
   * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>

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

   *
   * The HMAC implementation is derived from USAGI.
   * Copyright (c) 2002 Kazunori Miyazawa <miyazawa@linux-ipv6.org> / USAGI
   *
   * 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 <linux/err.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/module.h>

  #include <linux/scatterlist.h>

  #include <linux/slab.h>
  #include <linux/string.h>
  
  struct hmac_ctx {
  	struct crypto_hash *child;
  };

  static inline void *align_ptr(void *p, unsigned int align)
  {
  	return (void *)ALIGN((unsigned long)p, align);
  }
  
  static inline struct hmac_ctx *hmac_ctx(struct crypto_hash *tfm)
  {
  	return align_ptr(crypto_hash_ctx_aligned(tfm) +
  			 crypto_hash_blocksize(tfm) * 2 +
  			 crypto_hash_digestsize(tfm), sizeof(void *));
  }
  
  static int hmac_setkey(struct crypto_hash *parent,
  		       const u8 *inkey, unsigned int keylen)
  {
  	int bs = crypto_hash_blocksize(parent);
  	int ds = crypto_hash_digestsize(parent);
  	char *ipad = crypto_hash_ctx_aligned(parent);
  	char *opad = ipad + bs;
  	char *digest = opad + bs;
  	struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
  	struct crypto_hash *tfm = ctx->child;
  	unsigned int i;
  
  	if (keylen > bs) {
  		struct hash_desc desc;
  		struct scatterlist tmp;
  		int err;
  
  		desc.tfm = tfm;
  		desc.flags = crypto_hash_get_flags(parent);
  		desc.flags &= CRYPTO_TFM_REQ_MAY_SLEEP;

  		sg_init_one(&tmp, inkey, keylen);

  
  		err = crypto_hash_digest(&desc, &tmp, keylen, digest);
  		if (err)
  			return err;
  
  		inkey = digest;
  		keylen = ds;
  	}
  
  	memcpy(ipad, inkey, keylen);
  	memset(ipad + keylen, 0, bs - keylen);
  	memcpy(opad, ipad, bs);
  
  	for (i = 0; i < bs; i++) {
  		ipad[i] ^= 0x36;
  		opad[i] ^= 0x5c;
  	}
  
  	return 0;
  }
  
  static int hmac_init(struct hash_desc *pdesc)
  {
  	struct crypto_hash *parent = pdesc->tfm;
  	int bs = crypto_hash_blocksize(parent);
  	int ds = crypto_hash_digestsize(parent);
  	char *ipad = crypto_hash_ctx_aligned(parent);
  	struct hmac_ctx *ctx = align_ptr(ipad + bs * 2 + ds, sizeof(void *));
  	struct hash_desc desc;
  	struct scatterlist tmp;

  	int err;

  
  	desc.tfm = ctx->child;
  	desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;

  	sg_init_one(&tmp, ipad, bs);

  	err = crypto_hash_init(&desc);
  	if (unlikely(err))
  		return err;
  
  	return crypto_hash_update(&desc, &tmp, bs);

  }
  
  static int hmac_update(struct hash_desc *pdesc,
  		       struct scatterlist *sg, unsigned int nbytes)
  {
  	struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
  	struct hash_desc desc;
  
  	desc.tfm = ctx->child;
  	desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
  
  	return crypto_hash_update(&desc, sg, nbytes);
  }
  
  static int hmac_final(struct hash_desc *pdesc, u8 *out)
  {
  	struct crypto_hash *parent = pdesc->tfm;
  	int bs = crypto_hash_blocksize(parent);
  	int ds = crypto_hash_digestsize(parent);
  	char *opad = crypto_hash_ctx_aligned(parent) + bs;
  	char *digest = opad + bs;
  	struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
  	struct hash_desc desc;
  	struct scatterlist tmp;

  	int err;

  
  	desc.tfm = ctx->child;
  	desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;

  	sg_init_one(&tmp, opad, bs + ds);

  	err = crypto_hash_final(&desc, digest);
  	if (unlikely(err))
  		return err;
  
  	return crypto_hash_digest(&desc, &tmp, bs + ds, out);

  }
  
  static int hmac_digest(struct hash_desc *pdesc, struct scatterlist *sg,
  		       unsigned int nbytes, u8 *out)
  {
  	struct crypto_hash *parent = pdesc->tfm;
  	int bs = crypto_hash_blocksize(parent);
  	int ds = crypto_hash_digestsize(parent);
  	char *ipad = crypto_hash_ctx_aligned(parent);
  	char *opad = ipad + bs;
  	char *digest = opad + bs;
  	struct hmac_ctx *ctx = align_ptr(digest + ds, sizeof(void *));
  	struct hash_desc desc;
  	struct scatterlist sg1[2];
  	struct scatterlist sg2[1];

  	int err;

  
  	desc.tfm = ctx->child;
  	desc.flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;

  	sg_init_table(sg1, 2);

  	sg_set_buf(sg1, ipad, bs);

  	sg_set_page(&sg1[1], (void *) sg, 0, 0);

  	sg_init_table(sg2, 1);

  	sg_set_buf(sg2, opad, bs + ds);

  	err = crypto_hash_digest(&desc, sg1, nbytes + bs, digest);
  	if (unlikely(err))
  		return err;
  
  	return crypto_hash_digest(&desc, sg2, bs + ds, out);

  }
  
  static int hmac_init_tfm(struct crypto_tfm *tfm)
  {

  	struct crypto_hash *hash;

  	struct crypto_instance *inst = (void *)tfm->__crt_alg;
  	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
  	struct hmac_ctx *ctx = hmac_ctx(__crypto_hash_cast(tfm));

  	hash = crypto_spawn_hash(spawn);
  	if (IS_ERR(hash))
  		return PTR_ERR(hash);

  	ctx->child = hash;

  	return 0;
  }
  
  static void hmac_exit_tfm(struct crypto_tfm *tfm)
  {
  	struct hmac_ctx *ctx = hmac_ctx(__crypto_hash_cast(tfm));
  	crypto_free_hash(ctx->child);
  }
  
  static void hmac_free(struct crypto_instance *inst)
  {
  	crypto_drop_spawn(crypto_instance_ctx(inst));
  	kfree(inst);
  }

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

  {
  	struct crypto_instance *inst;
  	struct crypto_alg *alg;

  	int err;
  
  	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_HASH);
  	if (err)
  		return ERR_PTR(err);

  	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_HASH,
  				  CRYPTO_ALG_TYPE_HASH_MASK);

  	if (IS_ERR(alg))
  		return ERR_PTR(PTR_ERR(alg));
  
  	inst = crypto_alloc_instance("hmac", alg);
  	if (IS_ERR(inst))
  		goto out_put_alg;
  
  	inst->alg.cra_flags = CRYPTO_ALG_TYPE_HASH;
  	inst->alg.cra_priority = alg->cra_priority;
  	inst->alg.cra_blocksize = alg->cra_blocksize;
  	inst->alg.cra_alignmask = alg->cra_alignmask;
  	inst->alg.cra_type = &crypto_hash_type;
  
  	inst->alg.cra_hash.digestsize =
  		(alg->cra_flags & CRYPTO_ALG_TYPE_MASK) ==
  		CRYPTO_ALG_TYPE_HASH ? alg->cra_hash.digestsize :
  				       alg->cra_digest.dia_digestsize;
  
  	inst->alg.cra_ctxsize = sizeof(struct hmac_ctx) +
  				ALIGN(inst->alg.cra_blocksize * 2 +
  				      inst->alg.cra_hash.digestsize,
  				      sizeof(void *));
  
  	inst->alg.cra_init = hmac_init_tfm;
  	inst->alg.cra_exit = hmac_exit_tfm;
  
  	inst->alg.cra_hash.init = hmac_init;
  	inst->alg.cra_hash.update = hmac_update;
  	inst->alg.cra_hash.final = hmac_final;
  	inst->alg.cra_hash.digest = hmac_digest;
  	inst->alg.cra_hash.setkey = hmac_setkey;
  
  out_put_alg:
  	crypto_mod_put(alg);
  	return inst;
  }
  
  static struct crypto_template hmac_tmpl = {
  	.name = "hmac",
  	.alloc = hmac_alloc,
  	.free = hmac_free,
  	.module = THIS_MODULE,
  };
  
  static int __init hmac_module_init(void)
  {
  	return crypto_register_template(&hmac_tmpl);
  }
  
  static void __exit hmac_module_exit(void)
  {
  	crypto_unregister_template(&hmac_tmpl);
  }
  
  module_init(hmac_module_init);
  module_exit(hmac_module_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("HMAC hash algorithm");