linux/net/mac80211/michael.c
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   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
  16static 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
  30static 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
  56void 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}
  87
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