/*
   * GHASH: digest algorithm for GCM (Galois/Counter Mode).
   *
   * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi>
   * Copyright (c) 2009 Intel Corp.
   *   Author: Huang Ying <ying.huang@intel.com>
   *
   * The algorithm implementation is copied from gcm.c.
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 as published
   * by the Free Software Foundation.
   */
  
  #include <crypto/algapi.h>
  #include <crypto/gf128mul.h>

  #include <crypto/ghash.h>

  #include <crypto/internal/hash.h>
  #include <linux/crypto.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/module.h>

  static int ghash_init(struct shash_desc *desc)
  {
  	struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
  
  	memset(dctx, 0, sizeof(*dctx));
  
  	return 0;
  }
  
  static int ghash_setkey(struct crypto_shash *tfm,
  			const u8 *key, unsigned int keylen)
  {
  	struct ghash_ctx *ctx = crypto_shash_ctx(tfm);
  
  	if (keylen != GHASH_BLOCK_SIZE) {
  		crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
  		return -EINVAL;
  	}
  
  	if (ctx->gf128)
  		gf128mul_free_4k(ctx->gf128);
  	ctx->gf128 = gf128mul_init_4k_lle((be128 *)key);
  	if (!ctx->gf128)
  		return -ENOMEM;
  
  	return 0;
  }
  
  static int ghash_update(struct shash_desc *desc,
  			 const u8 *src, unsigned int srclen)
  {
  	struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
  	struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
  	u8 *dst = dctx->buffer;

  	if (!ctx->gf128)
  		return -ENOKEY;

  	if (dctx->bytes) {
  		int n = min(srclen, dctx->bytes);
  		u8 *pos = dst + (GHASH_BLOCK_SIZE - dctx->bytes);
  
  		dctx->bytes -= n;
  		srclen -= n;
  
  		while (n--)
  			*pos++ ^= *src++;
  
  		if (!dctx->bytes)
  			gf128mul_4k_lle((be128 *)dst, ctx->gf128);
  	}
  
  	while (srclen >= GHASH_BLOCK_SIZE) {
  		crypto_xor(dst, src, GHASH_BLOCK_SIZE);
  		gf128mul_4k_lle((be128 *)dst, ctx->gf128);
  		src += GHASH_BLOCK_SIZE;
  		srclen -= GHASH_BLOCK_SIZE;
  	}
  
  	if (srclen) {
  		dctx->bytes = GHASH_BLOCK_SIZE - srclen;
  		while (srclen--)
  			*dst++ ^= *src++;
  	}
  
  	return 0;
  }
  
  static void ghash_flush(struct ghash_ctx *ctx, struct ghash_desc_ctx *dctx)
  {
  	u8 *dst = dctx->buffer;
  
  	if (dctx->bytes) {
  		u8 *tmp = dst + (GHASH_BLOCK_SIZE - dctx->bytes);
  
  		while (dctx->bytes--)
  			*tmp++ ^= 0;
  
  		gf128mul_4k_lle((be128 *)dst, ctx->gf128);
  	}
  
  	dctx->bytes = 0;
  }
  
  static int ghash_final(struct shash_desc *desc, u8 *dst)
  {
  	struct ghash_desc_ctx *dctx = shash_desc_ctx(desc);
  	struct ghash_ctx *ctx = crypto_shash_ctx(desc->tfm);
  	u8 *buf = dctx->buffer;

  	if (!ctx->gf128)
  		return -ENOKEY;

  	ghash_flush(ctx, dctx);
  	memcpy(dst, buf, GHASH_BLOCK_SIZE);
  
  	return 0;
  }
  
  static void ghash_exit_tfm(struct crypto_tfm *tfm)
  {
  	struct ghash_ctx *ctx = crypto_tfm_ctx(tfm);
  	if (ctx->gf128)
  		gf128mul_free_4k(ctx->gf128);
  }
  
  static struct shash_alg ghash_alg = {
  	.digestsize	= GHASH_DIGEST_SIZE,
  	.init		= ghash_init,
  	.update		= ghash_update,
  	.final		= ghash_final,
  	.setkey		= ghash_setkey,
  	.descsize	= sizeof(struct ghash_desc_ctx),
  	.base		= {
  		.cra_name		= "ghash",
  		.cra_driver_name	= "ghash-generic",
  		.cra_priority		= 100,
  		.cra_flags		= CRYPTO_ALG_TYPE_SHASH,
  		.cra_blocksize		= GHASH_BLOCK_SIZE,
  		.cra_ctxsize		= sizeof(struct ghash_ctx),
  		.cra_module		= THIS_MODULE,

  		.cra_exit		= ghash_exit_tfm,
  	},
  };
  
  static int __init ghash_mod_init(void)
  {
  	return crypto_register_shash(&ghash_alg);
  }
  
  static void __exit ghash_mod_exit(void)
  {
  	crypto_unregister_shash(&ghash_alg);
  }
  
  module_init(ghash_mod_init);
  module_exit(ghash_mod_exit);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("GHASH Message Digest Algorithm");

  MODULE_ALIAS_CRYPTO("ghash");

  MODULE_ALIAS_CRYPTO("ghash-generic");