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 <linux/ieee80211.h>
  12 #include <asm/unaligned.h>
  13
  14 #include "michael.h"
  15
  16 static void michael_block(struct michael_mic_ctx *mctx, u32 val)
  17 {
  18         mctx->l ^= val;
  19         mctx->r ^= rol32(mctx->l, 17);
  20         mctx->l += mctx->r;
  21         mctx->r ^= ((mctx->l & 0xff00ff00) >> 8) |
  22                    ((mctx->l & 0x00ff00ff) << 8);
  23         mctx->l += mctx->r;
  24         mctx->r ^= rol32(mctx->l, 3);
  25         mctx->l += mctx->r;
  26         mctx->r ^= ror32(mctx->l, 2);
  27         mctx->l += mctx->r;
  28 }
  29
  30 static void michael_mic_hdr(struct michael_mic_ctx *mctx, const u8 *key,
  31                             struct ieee80211_hdr *hdr)
  32 {
  33         u8 *da, *sa, tid;
  34
  35         da = ieee80211_get_DA(hdr);
  36         sa = ieee80211_get_SA(hdr);
  37         if (ieee80211_is_data_qos(hdr->frame_control))
  38                 tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
  39         else
  40                 tid = 0;
  41
  42         mctx->l = get_unaligned_le32(key);
  43         mctx->r = get_unaligned_le32(key + 4);
  44
  45         /*
  46          * A pseudo header (DA, SA, Priority, 0, 0, 0) is used in Michael MIC
  47          * calculation, but it is _not_ transmitted
  48          */
  49         michael_block(mctx, get_unaligned_le32(da));
  50         michael_block(mctx, get_unaligned_le16(&da[4]) |
  51                             (get_unaligned_le16(sa) << 16));
  52         michael_block(mctx, get_unaligned_le32(&sa[2]));
  53         michael_block(mctx, tid);
  54 }
  55
  56 void michael_mic(const u8 *key, struct ieee80211_hdr *hdr,
  57                  const u8 *data, size_t data_len, u8 *mic)
  58 {
  59         u32 val;
  60         size_t block, blocks, left;
  61         struct michael_mic_ctx mctx;
  62
  63         michael_mic_hdr(&mctx, key, hdr);
  64
  65         /* Real data */
  66         blocks = data_len / 4;
  67         left = data_len % 4;
  68
  69         for (block = 0; block < blocks; block++)
  70                 michael_block(&mctx, get_unaligned_le32(&data[block * 4]));
  71
  72         /* Partial block of 0..3 bytes and padding: 0x5a + 4..7 zeros to make
  73          * total length a multiple of 4. */
  74         val = 0x5a;
  75         while (left > 0) {
  76                 val <<= 8;
  77                 left--;
  78                 val |= data[blocks * 4 + left];
  79         }
  80
  81         michael_block(&mctx, val);
  82         michael_block(&mctx, 0);
  83
  84         put_unaligned_le32(mctx.l, mic);
  85         put_unaligned_le32(mctx.r, mic + 4);
  86 }