crypto/michael_mic.c

   1 /*
   2  * Cryptographic API
   3  *
   4  * Michael MIC (IEEE 802.11i/TKIP) keyed digest
   5  *
   6  * Copyright (c) 2004 Jouni Malinen <jkmaline@cc.hut.fi>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/init.h>
  14 #include <linux/module.h>
  15 #include <linux/string.h>
  16 #include <linux/crypto.h>
  17
  18
  19 struct michael_mic_ctx {
  20         u8 pending[4];
  21         size_t pending_len;
  22
  23         u32 l, r;
  24 };
  25
  26
  27 static inline u32 rotl(u32 val, int bits)
  28 {
  29         return (val << bits) | (val >> (32 - bits));
  30 }
  31
  32
  33 static inline u32 rotr(u32 val, int bits)
  34 {
  35         return (val >> bits) | (val << (32 - bits));
  36 }
  37
  38
  39 static inline u32 xswap(u32 val)
  40 {
  41         return ((val & 0x00ff00ff) << 8) | ((val & 0xff00ff00) >> 8);
  42 }
  43
  44
  45 #define michael_block(l, r)     \
  46 do {                            \
  47         r ^= rotl(l, 17);       \
  48         l += r;                 \
  49         r ^= xswap(l);          \
  50         l += r;                 \
  51         r ^= rotl(l, 3);        \
  52         l += r;                 \
  53         r ^= rotr(l, 2);        \
  54         l += r;                 \
  55 } while (0)
  56
  57
  58 static inline u32 get_le32(const u8 *p)
  59 {
  60         return p[0] | (p[1] << 8) | (p[2] << 16) | (p[3] << 24);
  61 }
  62
  63
  64 static inline void put_le32(u8 *p, u32 v)
  65 {
  66         p[0] = v;
  67         p[1] = v >> 8;
  68         p[2] = v >> 16;
  69         p[3] = v >> 24;
  70 }
  71
  72
  73 static void michael_init(void *ctx)
  74 {
  75         struct michael_mic_ctx *mctx = ctx;
  76         mctx->pending_len = 0;
  77 }
  78
  79
  80 static void michael_update(void *ctx, const u8 *data, unsigned int len)
  81 {
  82         struct michael_mic_ctx *mctx = ctx;
  83
  84         if (mctx->pending_len) {
  85                 int flen = 4 - mctx->pending_len;
  86                 if (flen > len)
  87                         flen = len;
  88                 memcpy(&mctx->pending[mctx->pending_len], data, flen);
  89                 mctx->pending_len += flen;
  90                 data += flen;
  91                 len -= flen;
  92
  93                 if (mctx->pending_len < 4)
  94                         return;
  95
  96                 mctx->l ^= get_le32(mctx->pending);
  97                 michael_block(mctx->l, mctx->r);
  98                 mctx->pending_len = 0;
  99         }
 100
 101         while (len >= 4) {
 102                 mctx->l ^= get_le32(data);
 103                 michael_block(mctx->l, mctx->r);
 104                 data += 4;
 105                 len -= 4;
 106         }
 107
 108         if (len > 0) {
 109                 mctx->pending_len = len;
 110                 memcpy(mctx->pending, data, len);
 111         }
 112 }
 113
 114
 115 static void michael_final(void *ctx, u8 *out)
 116 {
 117         struct michael_mic_ctx *mctx = ctx;
 118         u8 *data = mctx->pending;
 119
 120         /* Last block and padding (0x5a, 4..7 x 0) */
 121         switch (mctx->pending_len) {
 122         case 0:
 123                 mctx->l ^= 0x5a;
 124                 break;
 125         case 1:
 126                 mctx->l ^= data[0] | 0x5a00;
 127                 break;
 128         case 2:
 129                 mctx->l ^= data[0] | (data[1] << 8) | 0x5a0000;
 130                 break;
 131         case 3:
 132                 mctx->l ^= data[0] | (data[1] << 8) | (data[2] << 16) |
 133                         0x5a000000;
 134                 break;
 135         }
 136         michael_block(mctx->l, mctx->r);
 137         /* l ^= 0; */
 138         michael_block(mctx->l, mctx->r);
 139
 140         put_le32(out, mctx->l);
 141         put_le32(out + 4, mctx->r);
 142 }
 143
 144
 145 static int michael_setkey(void *ctx, const u8 *key, unsigned int keylen,
 146                           u32 *flags)
 147 {
 148         struct michael_mic_ctx *mctx = ctx;
 149         if (keylen != 8) {
 150                 if (flags)
 151                         *flags = CRYPTO_TFM_RES_BAD_KEY_LEN;
 152                 return -EINVAL;
 153         }
 154         mctx->l = get_le32(key);
 155         mctx->r = get_le32(key + 4);
 156         return 0;
 157 }
 158
 159
 160 static struct crypto_alg michael_mic_alg = {
 161         .cra_name       = "michael_mic",
 162         .cra_flags      = CRYPTO_ALG_TYPE_DIGEST,
 163         .cra_blocksize  = 8,
 164         .cra_ctxsize    = sizeof(struct michael_mic_ctx),
 165         .cra_module     = THIS_MODULE,
 166         .cra_list       = LIST_HEAD_INIT(michael_mic_alg.cra_list),
 167         .cra_u          = { .digest = {
 168         .dia_digestsize = 8,
 169         .dia_init       = michael_init,
 170         .dia_update     = michael_update,
 171         .dia_final      = michael_final,
 172         .dia_setkey     = michael_setkey } }
 173 };
 174
 175
 176 static int __init michael_mic_init(void)
 177 {
 178         return crypto_register_alg(&michael_mic_alg);
 179 }
 180
 181
 182 static void __exit michael_mic_exit(void)
 183 {
 184         crypto_unregister_alg(&michael_mic_alg);
 185 }
 186
 187
 188 module_init(michael_mic_init);
 189 module_exit(michael_mic_exit);
 190
 191 MODULE_LICENSE("GPL v2");
 192 MODULE_DESCRIPTION("Michael MIC");
 193 MODULE_AUTHOR("Jouni Malinen <jkmaline@cc.hut.fi>");