LXR linux/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
  10#include <linux/types.h>
  11
  12#include "michael.h"
  13
  14static inline u32 rotr(u32 val, int bits)
  15{
  16        return (val >> bits) | (val << (32 - bits));
  17}
  18
  19
  20static inline u32 rotl(u32 val, int bits)
  21{
  22        return (val << bits) | (val >> (32 - bits));
  23}
  24
  25
  26static inline u32 xswap(u32 val)
  27{
  28        return ((val & 0xff00ff00) >> 8) | ((val & 0x00ff00ff) << 8);
  29}
  30
  31
  32#define michael_block(l, r) \
  33do { \
  34        r ^= rotl(l, 17); \
  35        l += r; \
  36        r ^= xswap(l); \
  37        l += r; \
  38        r ^= rotl(l, 3); \
  39        l += r; \
  40        r ^= rotr(l, 2); \
  41        l += r; \
  42} while (0)
  43
  44
  45static inline u32 michael_get32(u8 *data)
  46{
  47        return data[0] | (data[1] << 8) | (data[2] << 16) | (data[3] << 24);
  48}
  49
  50
  51static inline void michael_put32(u32 val, u8 *data)
  52{
  53        data[0] = val & 0xff;
  54        data[1] = (val >> 8) & 0xff;
  55        data[2] = (val >> 16) & 0xff;
  56        data[3] = (val >> 24) & 0xff;
  57}
  58
  59
  60void michael_mic(u8 *key, u8 *da, u8 *sa, u8 priority,
  61                 u8 *data, size_t data_len, u8 *mic)
  62{
  63        u32 l, r, val;
  64        size_t block, blocks, left;
  65
  66        l = michael_get32(key);
  67        r = michael_get32(key + 4);
  68
  69        /* A pseudo header (DA, SA, Priority, 0, 0, 0) is used in Michael MIC
  70         * calculation, but it is _not_ transmitted */
  71        l ^= michael_get32(da);
  72        michael_block(l, r);
  73        l ^= da[4] | (da[5] << 8) | (sa[0] << 16) | (sa[1] << 24);
  74        michael_block(l, r);
  75        l ^= michael_get32(&sa[2]);
  76        michael_block(l, r);
  77        l ^= priority;
  78        michael_block(l, r);
  79
  80        /* Real data */
  81        blocks = data_len / 4;
  82        left = data_len % 4;
  83
  84        for (block = 0; block < blocks; block++) {
  85                l ^= michael_get32(&data[block * 4]);
  86                michael_block(l, r);
  87        }
  88
  89        /* Partial block of 0..3 bytes and padding: 0x5a + 4..7 zeros to make
  90         * total length a multiple of 4. */
  91        val = 0x5a;
  92        while (left > 0) {
  93                val <<= 8;
  94                left--;
  95                val |= data[blocks * 4 + left];
  96        }
  97        l ^= val;
  98        michael_block(l, r);
  99        /* last block is zero, so l ^ 0 = l */
 100        michael_block(l, r);
 101
 102        michael_put32(l, mic);
 103        michael_put32(r, mic + 4);
 104}
 105