net/mac80211/michael.c

   1 /*
   2  * Michael MIC implementation - optimized for TKIP MIC operations
   3  * Copyright 2002-2003, Instant802 Networks, Inc.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9 #include <linux/types.h>
  10 #include <linux/bitops.h>
  11 #include <asm/unaligned.h>
  12
  13 #include "michael.h"
  14
  15 static void michael_block(struct michael_mic_ctx *mctx, u32 val)
  16 {
  17         mctx->l ^= val;
  18         mctx->r ^= rol32(mctx->l, 17);
  19         mctx->l += mctx->r;
  20         mctx->r ^= ((mctx->l & 0xff00ff00) >> 8) |
  21                    ((mctx->l & 0x00ff00ff) << 8);
  22         mctx->l += mctx->r;
  23         mctx->r ^= rol32(mctx->l, 3);
  24         mctx->l += mctx->r;
  25         mctx->r ^= ror32(mctx->l, 2);
  26         mctx->l += mctx->r;
  27 }
  28
  29 static void michael_mic_hdr(struct michael_mic_ctx *mctx,
  30                         const u8 *key, const u8 *da, const u8 *sa, u8 priority)
  31 {
  32         mctx->l = get_unaligned_le32(key);
  33         mctx->r = get_unaligned_le32(key + 4);
  34
  35         /*
  36          * A pseudo header (DA, SA, Priority, 0, 0, 0) is used in Michael MIC
  37          * calculation, but it is _not_ transmitted
  38          */
  39         michael_block(mctx, get_unaligned_le32(da));
  40         michael_block(mctx, get_unaligned_le16(&da[4]) |
  41                             (get_unaligned_le16(sa) << 16));
  42         michael_block(mctx, get_unaligned_le32(&sa[2]));
  43         michael_block(mctx, priority);
  44 }
  45
  46 void michael_mic(const u8 *key, const u8 *da, const u8 *sa, u8 priority,
  47                  const u8 *data, size_t data_len, u8 *mic)
  48 {
  49         u32 val;
  50         size_t block, blocks, left;
  51         struct michael_mic_ctx mctx;
  52
  53         michael_mic_hdr(&mctx, key, da, sa, priority);
  54
  55         /* Real data */
  56         blocks = data_len / 4;
  57         left = data_len % 4;
  58
  59         for (block = 0; block < blocks; block++)
  60                 michael_block(&mctx, get_unaligned_le32(&data[block * 4]));
  61
  62         /* Partial block of 0..3 bytes and padding: 0x5a + 4..7 zeros to make
  63          * total length a multiple of 4. */
  64         val = 0x5a;
  65         while (left > 0) {
  66                 val <<= 8;
  67                 left--;
  68                 val |= data[blocks * 4 + left];
  69         }
  70
  71         michael_block(&mctx, val);
  72         michael_block(&mctx, 0);
  73
  74         put_unaligned_le32(mctx.l, mic);
  75         put_unaligned_le32(mctx.r, mic + 4);
  76 }