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
  14 static inline u32 rotr(u32 val, int bits)
  15 {
  16         return (val >> bits) | (val << (32 - bits));
  17 }
  18
  19
  20 static inline u32 rotl(u32 val, int bits)
  21 {
  22         return (val << bits) | (val >> (32 - bits));
  23 }
  24
  25
  26 static inline u32 xswap(u32 val)
  27 {
  28         return ((val & 0xff00ff00) >> 8) | ((val & 0x00ff00ff) << 8);
  29 }
  30
  31
  32 #define michael_block(l, r) \
  33 do { \
  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
  45 static inline u32 michael_get32(u8 *data)
  46 {
  47         return data[0] | (data[1] << 8) | (data[2] << 16) | (data[3] << 24);
  48 }
  49
  50
  51 static 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
  60 void 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 }