/*
   * Cryptographic API
   *
   * Michael MIC (IEEE 802.11i/TKIP) keyed digest
   *

   * Copyright (c) 2004 Jouni Malinen <j@w1.fi>

   *
   * 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 <asm/byteorder.h>

  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/string.h>
  #include <linux/crypto.h>

  #include <linux/types.h>

  
  
  struct michael_mic_ctx {
  	u8 pending[4];
  	size_t pending_len;
  
  	u32 l, r;
  };
  
  
  static inline u32 xswap(u32 val)
  {
  	return ((val & 0x00ff00ff) << 8) | ((val & 0xff00ff00) >> 8);
  }
  
  
  #define michael_block(l, r)	\
  do {				\
  	r ^= rol32(l, 17);	\
  	l += r;			\
  	r ^= xswap(l);		\
  	l += r;			\
  	r ^= rol32(l, 3);	\
  	l += r;			\
  	r ^= ror32(l, 2);	\
  	l += r;			\
  } while (0)

  static void michael_init(struct crypto_tfm *tfm)

  {

  	struct michael_mic_ctx *mctx = crypto_tfm_ctx(tfm);

  	mctx->pending_len = 0;
  }

  static void michael_update(struct crypto_tfm *tfm, const u8 *data,
  			   unsigned int len)

  {

  	struct michael_mic_ctx *mctx = crypto_tfm_ctx(tfm);

  	const __le32 *src;

  
  	if (mctx->pending_len) {
  		int flen = 4 - mctx->pending_len;
  		if (flen > len)
  			flen = len;
  		memcpy(&mctx->pending[mctx->pending_len], data, flen);
  		mctx->pending_len += flen;
  		data += flen;
  		len -= flen;
  
  		if (mctx->pending_len < 4)
  			return;

  		src = (const __le32 *)mctx->pending;
  		mctx->l ^= le32_to_cpup(src);

  		michael_block(mctx->l, mctx->r);
  		mctx->pending_len = 0;
  	}

  	src = (const __le32 *)data;

  	while (len >= 4) {

  		mctx->l ^= le32_to_cpup(src++);

  		michael_block(mctx->l, mctx->r);

  		len -= 4;
  	}
  
  	if (len > 0) {
  		mctx->pending_len = len;

  		memcpy(mctx->pending, src, len);

  	}
  }

  static void michael_final(struct crypto_tfm *tfm, u8 *out)

  {

  	struct michael_mic_ctx *mctx = crypto_tfm_ctx(tfm);

  	u8 *data = mctx->pending;

  	__le32 *dst = (__le32 *)out;

  
  	/* Last block and padding (0x5a, 4..7 x 0) */
  	switch (mctx->pending_len) {
  	case 0:
  		mctx->l ^= 0x5a;
  		break;
  	case 1:
  		mctx->l ^= data[0] | 0x5a00;
  		break;
  	case 2:
  		mctx->l ^= data[0] | (data[1] << 8) | 0x5a0000;
  		break;
  	case 3:
  		mctx->l ^= data[0] | (data[1] << 8) | (data[2] << 16) |
  			0x5a000000;
  		break;
  	}
  	michael_block(mctx->l, mctx->r);
  	/* l ^= 0; */
  	michael_block(mctx->l, mctx->r);

  	dst[0] = cpu_to_le32(mctx->l);
  	dst[1] = cpu_to_le32(mctx->r);

  }

  static int michael_setkey(struct crypto_tfm *tfm, const u8 *key,

  			  unsigned int keylen)

  {

  	struct michael_mic_ctx *mctx = crypto_tfm_ctx(tfm);

  	const __le32 *data = (const __le32 *)key;

  	if (keylen != 8) {

  		tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;

  		return -EINVAL;
  	}

  
  	mctx->l = le32_to_cpu(data[0]);
  	mctx->r = le32_to_cpu(data[1]);

  	return 0;
  }
  
  
  static struct crypto_alg michael_mic_alg = {
  	.cra_name	= "michael_mic",
  	.cra_flags	= CRYPTO_ALG_TYPE_DIGEST,
  	.cra_blocksize	= 8,
  	.cra_ctxsize	= sizeof(struct michael_mic_ctx),
  	.cra_module	= THIS_MODULE,

  	.cra_alignmask	= 3,

  	.cra_list	= LIST_HEAD_INIT(michael_mic_alg.cra_list),
  	.cra_u		= { .digest = {
  	.dia_digestsize	= 8,
  	.dia_init	= michael_init,
  	.dia_update	= michael_update,
  	.dia_final	= michael_final,
  	.dia_setkey	= michael_setkey } }
  };
  
  
  static int __init michael_mic_init(void)
  {
  	return crypto_register_alg(&michael_mic_alg);
  }
  
  
  static void __exit michael_mic_exit(void)
  {
  	crypto_unregister_alg(&michael_mic_alg);
  }
  
  
  module_init(michael_mic_init);
  module_exit(michael_mic_exit);
  
  MODULE_LICENSE("GPL v2");
  MODULE_DESCRIPTION("Michael MIC");

  MODULE_AUTHOR("Jouni Malinen <j@w1.fi>");