/*
   * 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/internal/hash.h>
  #include <crypto/scatterwalk.h>
  #include <linux/err.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/scatterlist.h>
  #include <linux/string.h>
  
  struct hmac_ctx {
  	struct crypto_shash *hash;
  };
  
  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_shash *tfm)
  {
  	return align_ptr(crypto_shash_ctx_aligned(tfm) +
  			 crypto_shash_statesize(tfm) * 2,
  			 crypto_tfm_ctx_alignment());
  }
  
  static int hmac_setkey(struct crypto_shash *parent,
  		       const u8 *inkey, unsigned int keylen)
  {
  	int bs = crypto_shash_blocksize(parent);
  	int ds = crypto_shash_digestsize(parent);
  	int ss = crypto_shash_statesize(parent);
  	char *ipad = crypto_shash_ctx_aligned(parent);
  	char *opad = ipad + ss;
  	struct hmac_ctx *ctx = align_ptr(opad + ss,
  					 crypto_tfm_ctx_alignment());
  	struct crypto_shash *hash = ctx->hash;
  	SHASH_DESC_ON_STACK(shash, hash);
  	unsigned int i;
  
  	shash->tfm = hash;
  	shash->flags = crypto_shash_get_flags(parent)
  		& CRYPTO_TFM_REQ_MAY_SLEEP;
  
  	if (keylen > bs) {
  		int err;
  
  		err = crypto_shash_digest(shash, inkey, keylen, ipad);
  		if (err)
  			return err;
  
  		keylen = ds;
  	} else
  		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 crypto_shash_init(shash) ?:
  	       crypto_shash_update(shash, ipad, bs) ?:
  	       crypto_shash_export(shash, ipad) ?:
  	       crypto_shash_init(shash) ?:
  	       crypto_shash_update(shash, opad, bs) ?:
  	       crypto_shash_export(shash, opad);
  }
  
  static int hmac_export(struct shash_desc *pdesc, void *out)
  {
  	struct shash_desc *desc = shash_desc_ctx(pdesc);
  
  	desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
  
  	return crypto_shash_export(desc, out);
  }
  
  static int hmac_import(struct shash_desc *pdesc, const void *in)
  {
  	struct shash_desc *desc = shash_desc_ctx(pdesc);
  	struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
  
  	desc->tfm = ctx->hash;
  	desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
  
  	return crypto_shash_import(desc, in);
  }
  
  static int hmac_init(struct shash_desc *pdesc)
  {
  	return hmac_import(pdesc, crypto_shash_ctx_aligned(pdesc->tfm));
  }
  
  static int hmac_update(struct shash_desc *pdesc,
  		       const u8 *data, unsigned int nbytes)
  {
  	struct shash_desc *desc = shash_desc_ctx(pdesc);
  
  	desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
  
  	return crypto_shash_update(desc, data, nbytes);
  }
  
  static int hmac_final(struct shash_desc *pdesc, u8 *out)
  {
  	struct crypto_shash *parent = pdesc->tfm;
  	int ds = crypto_shash_digestsize(parent);
  	int ss = crypto_shash_statesize(parent);
  	char *opad = crypto_shash_ctx_aligned(parent) + ss;
  	struct shash_desc *desc = shash_desc_ctx(pdesc);
  
  	desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
  
  	return crypto_shash_final(desc, out) ?:
  	       crypto_shash_import(desc, opad) ?:
  	       crypto_shash_finup(desc, out, ds, out);
  }
  
  static int hmac_finup(struct shash_desc *pdesc, const u8 *data,
  		      unsigned int nbytes, u8 *out)
  {
  
  	struct crypto_shash *parent = pdesc->tfm;
  	int ds = crypto_shash_digestsize(parent);
  	int ss = crypto_shash_statesize(parent);
  	char *opad = crypto_shash_ctx_aligned(parent) + ss;
  	struct shash_desc *desc = shash_desc_ctx(pdesc);
  
  	desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
  
  	return crypto_shash_finup(desc, data, nbytes, out) ?:
  	       crypto_shash_import(desc, opad) ?:
  	       crypto_shash_finup(desc, out, ds, out);
  }
  
  static int hmac_init_tfm(struct crypto_tfm *tfm)
  {
  	struct crypto_shash *parent = __crypto_shash_cast(tfm);
  	struct crypto_shash *hash;
  	struct crypto_instance *inst = (void *)tfm->__crt_alg;
  	struct crypto_shash_spawn *spawn = crypto_instance_ctx(inst);
  	struct hmac_ctx *ctx = hmac_ctx(parent);
  
  	hash = crypto_spawn_shash(spawn);
  	if (IS_ERR(hash))
  		return PTR_ERR(hash);
  
  	parent->descsize = sizeof(struct shash_desc) +
  			   crypto_shash_descsize(hash);
  
  	ctx->hash = hash;
  	return 0;
  }
  
  static void hmac_exit_tfm(struct crypto_tfm *tfm)
  {
  	struct hmac_ctx *ctx = hmac_ctx(__crypto_shash_cast(tfm));
  	crypto_free_shash(ctx->hash);
  }
  
  static int hmac_create(struct crypto_template *tmpl, struct rtattr **tb)
  {
  	struct shash_instance *inst;
  	struct crypto_alg *alg;
  	struct shash_alg *salg;
  	int err;
  	int ds;
  	int ss;
  
  	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);
  	if (err)
  		return err;
  
  	salg = shash_attr_alg(tb[1], 0, 0);
  	if (IS_ERR(salg))
  		return PTR_ERR(salg);
  
  	err = -EINVAL;
  	ds = salg->digestsize;
  	ss = salg->statesize;
  	alg = &salg->base;
  	if (ds > alg->cra_blocksize ||
  	    ss < alg->cra_blocksize)
  		goto out_put_alg;
  
  	inst = shash_alloc_instance("hmac", alg);
  	err = PTR_ERR(inst);
  	if (IS_ERR(inst))
  		goto out_put_alg;
  
  	err = crypto_init_shash_spawn(shash_instance_ctx(inst), salg,
  				      shash_crypto_instance(inst));
  	if (err)
  		goto out_free_inst;
  
  	inst->alg.base.cra_priority = alg->cra_priority;
  	inst->alg.base.cra_blocksize = alg->cra_blocksize;
  	inst->alg.base.cra_alignmask = alg->cra_alignmask;
  
  	ss = ALIGN(ss, alg->cra_alignmask + 1);
  	inst->alg.digestsize = ds;
  	inst->alg.statesize = ss;
  
  	inst->alg.base.cra_ctxsize = sizeof(struct hmac_ctx) +
  				     ALIGN(ss * 2, crypto_tfm_ctx_alignment());
  
  	inst->alg.base.cra_init = hmac_init_tfm;
  	inst->alg.base.cra_exit = hmac_exit_tfm;
  
  	inst->alg.init = hmac_init;
  	inst->alg.update = hmac_update;
  	inst->alg.final = hmac_final;
  	inst->alg.finup = hmac_finup;
  	inst->alg.export = hmac_export;
  	inst->alg.import = hmac_import;
  	inst->alg.setkey = hmac_setkey;
  
  	err = shash_register_instance(tmpl, inst);
  	if (err) {
  out_free_inst:
  		shash_free_instance(shash_crypto_instance(inst));
  	}
  
  out_put_alg:
  	crypto_mod_put(alg);
  	return err;
  }
  
  static struct crypto_template hmac_tmpl = {
  	.name = "hmac",
  	.create = hmac_create,
  	.free = shash_free_instance,
  	.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");
  MODULE_ALIAS_CRYPTO("hmac");