linux/crypto/michael_mic.c
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   1/*
   2 * Cryptographic API
   3 *
   4 * Michael MIC (IEEE 802.11i/TKIP) keyed digest
   5 *
   6 * Copyright (c) 2004 Jouni Malinen <j@w1.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 <asm/byteorder.h>
  14#include <linux/init.h>
  15#include <linux/module.h>
  16#include <linux/string.h>
  17#include <linux/crypto.h>
  18#include <linux/types.h>
  19
  20
  21struct michael_mic_ctx {
  22        u8 pending[4];
  23        size_t pending_len;
  24
  25        u32 l, r;
  26};
  27
  28
  29static inline u32 xswap(u32 val)
  30{
  31        return ((val & 0x00ff00ff) << 8) | ((val & 0xff00ff00) >> 8);
  32}
  33
  34
  35#define michael_block(l, r)     \
  36do {                            \
  37        r ^= rol32(l, 17);      \
  38        l += r;                 \
  39        r ^= xswap(l);          \
  40        l += r;                 \
  41        r ^= rol32(l, 3);       \
  42        l += r;                 \
  43        r ^= ror32(l, 2);       \
  44        l += r;                 \
  45} while (0)
  46
  47
  48static void michael_init(struct crypto_tfm *tfm)
  49{
  50        struct michael_mic_ctx *mctx = crypto_tfm_ctx(tfm);
  51        mctx->pending_len = 0;
  52}
  53
  54
  55static void michael_update(struct crypto_tfm *tfm, const u8 *data,
  56                           unsigned int len)
  57{
  58        struct michael_mic_ctx *mctx = crypto_tfm_ctx(tfm);
  59        const __le32 *src;
  60
  61        if (mctx->pending_len) {
  62                int flen = 4 - mctx->pending_len;
  63                if (flen > len)
  64                        flen = len;
  65                memcpy(&mctx->pending[mctx->pending_len], data, flen);
  66                mctx->pending_len += flen;
  67                data += flen;
  68                len -= flen;
  69
  70                if (mctx->pending_len < 4)
  71                        return;
  72
  73                src = (const __le32 *)mctx->pending;
  74                mctx->l ^= le32_to_cpup(src);
  75                michael_block(mctx->l, mctx->r);
  76                mctx->pending_len = 0;
  77        }
  78
  79        src = (const __le32 *)data;
  80
  81        while (len >= 4) {
  82                mctx->l ^= le32_to_cpup(src++);
  83                michael_block(mctx->l, mctx->r);
  84                len -= 4;
  85        }
  86
  87        if (len > 0) {
  88                mctx->pending_len = len;
  89                memcpy(mctx->pending, src, len);
  90        }
  91}
  92
  93
  94static void michael_final(struct crypto_tfm *tfm, u8 *out)
  95{
  96        struct michael_mic_ctx *mctx = crypto_tfm_ctx(tfm);
  97        u8 *data = mctx->pending;
  98        __le32 *dst = (__le32 *)out;
  99
 100        /* Last block and padding (0x5a, 4..7 x 0) */
 101        switch (mctx->pending_len) {
 102        case 0:
 103                mctx->l ^= 0x5a;
 104                break;
 105        case 1:
 106                mctx->l ^= data[0] | 0x5a00;
 107                break;
 108        case 2:
 109                mctx->l ^= data[0] | (data[1] << 8) | 0x5a0000;
 110                break;
 111        case 3:
 112                mctx->l ^= data[0] | (data[1] << 8) | (data[2] << 16) |
 113                        0x5a000000;
 114                break;
 115        }
 116        michael_block(mctx->l, mctx->r);
 117        /* l ^= 0; */
 118        michael_block(mctx->l, mctx->r);
 119
 120        dst[0] = cpu_to_le32(mctx->l);
 121        dst[1] = cpu_to_le32(mctx->r);
 122}
 123
 124
 125static int michael_setkey(struct crypto_tfm *tfm, const u8 *key,
 126                          unsigned int keylen)
 127{
 128        struct michael_mic_ctx *mctx = crypto_tfm_ctx(tfm);
 129        const __le32 *data = (const __le32 *)key;
 130
 131        if (keylen != 8) {
 132                tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
 133                return -EINVAL;
 134        }
 135
 136        mctx->l = le32_to_cpu(data[0]);
 137        mctx->r = le32_to_cpu(data[1]);
 138        return 0;
 139}
 140
 141
 142static struct crypto_alg michael_mic_alg = {
 143        .cra_name       = "michael_mic",
 144        .cra_flags      = CRYPTO_ALG_TYPE_DIGEST,
 145        .cra_blocksize  = 8,
 146        .cra_ctxsize    = sizeof(struct michael_mic_ctx),
 147        .cra_module     = THIS_MODULE,
 148        .cra_alignmask  = 3,
 149        .cra_list       = LIST_HEAD_INIT(michael_mic_alg.cra_list),
 150        .cra_u          = { .digest = {
 151        .dia_digestsize = 8,
 152        .dia_init       = michael_init,
 153        .dia_update     = michael_update,
 154        .dia_final      = michael_final,
 155        .dia_setkey     = michael_setkey } }
 156};
 157
 158
 159static int __init michael_mic_init(void)
 160{
 161        return crypto_register_alg(&michael_mic_alg);
 162}
 163
 164
 165static void __exit michael_mic_exit(void)
 166{
 167        crypto_unregister_alg(&michael_mic_alg);
 168}
 169
 170
 171module_init(michael_mic_init);
 172module_exit(michael_mic_exit);
 173
 174MODULE_LICENSE("GPL v2");
 175MODULE_DESCRIPTION("Michael MIC");
 176MODULE_AUTHOR("Jouni Malinen <j@w1.fi>");
 177