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#include <crypto/internal/hash.h>
  13#include <asm/byteorder.h>
  14#include <linux/init.h>
  15#include <linux/module.h>
  16#include <linux/string.h>
  17#include <linux/types.h>
  18
  19
  20struct michael_mic_ctx {
  21        u32 l, r;
  22};
  23
  24struct michael_mic_desc_ctx {
  25        u8 pending[4];
  26        size_t pending_len;
  27
  28        u32 l, r;
  29};
  30
  31static inline u32 xswap(u32 val)
  32{
  33        return ((val & 0x00ff00ff) << 8) | ((val & 0xff00ff00) >> 8);
  34}
  35
  36
  37#define michael_block(l, r)     \
  38do {                            \
  39        r ^= rol32(l, 17);      \
  40        l += r;                 \
  41        r ^= xswap(l);          \
  42        l += r;                 \
  43        r ^= rol32(l, 3);       \
  44        l += r;                 \
  45        r ^= ror32(l, 2);       \
  46        l += r;                 \
  47} while (0)
  48
  49
  50static int michael_init(struct shash_desc *desc)
  51{
  52        struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);
  53        struct michael_mic_ctx *ctx = crypto_shash_ctx(desc->tfm);
  54        mctx->pending_len = 0;
  55        mctx->l = ctx->l;
  56        mctx->r = ctx->r;
  57
  58        return 0;
  59}
  60
  61
  62static int michael_update(struct shash_desc *desc, const u8 *data,
  63                           unsigned int len)
  64{
  65        struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);
  66        const __le32 *src;
  67
  68        if (mctx->pending_len) {
  69                int flen = 4 - mctx->pending_len;
  70                if (flen > len)
  71                        flen = len;
  72                memcpy(&mctx->pending[mctx->pending_len], data, flen);
  73                mctx->pending_len += flen;
  74                data += flen;
  75                len -= flen;
  76
  77                if (mctx->pending_len < 4)
  78                        return 0;
  79
  80                src = (const __le32 *)mctx->pending;
  81                mctx->l ^= le32_to_cpup(src);
  82                michael_block(mctx->l, mctx->r);
  83                mctx->pending_len = 0;
  84        }
  85
  86        src = (const __le32 *)data;
  87
  88        while (len >= 4) {
  89                mctx->l ^= le32_to_cpup(src++);
  90                michael_block(mctx->l, mctx->r);
  91                len -= 4;
  92        }
  93
  94        if (len > 0) {
  95                mctx->pending_len = len;
  96                memcpy(mctx->pending, src, len);
  97        }
  98
  99        return 0;
 100}
 101
 102
 103static int michael_final(struct shash_desc *desc, u8 *out)
 104{
 105        struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);
 106        u8 *data = mctx->pending;
 107        __le32 *dst = (__le32 *)out;
 108
 109        /* Last block and padding (0x5a, 4..7 x 0) */
 110        switch (mctx->pending_len) {
 111        case 0:
 112                mctx->l ^= 0x5a;
 113                break;
 114        case 1:
 115                mctx->l ^= data[0] | 0x5a00;
 116                break;
 117        case 2:
 118                mctx->l ^= data[0] | (data[1] << 8) | 0x5a0000;
 119                break;
 120        case 3:
 121                mctx->l ^= data[0] | (data[1] << 8) | (data[2] << 16) |
 122                        0x5a000000;
 123                break;
 124        }
 125        michael_block(mctx->l, mctx->r);
 126        /* l ^= 0; */
 127        michael_block(mctx->l, mctx->r);
 128
 129        dst[0] = cpu_to_le32(mctx->l);
 130        dst[1] = cpu_to_le32(mctx->r);
 131
 132        return 0;
 133}
 134
 135
 136static int michael_setkey(struct crypto_shash *tfm, const u8 *key,
 137                          unsigned int keylen)
 138{
 139        struct michael_mic_ctx *mctx = crypto_shash_ctx(tfm);
 140
 141        const __le32 *data = (const __le32 *)key;
 142
 143        if (keylen != 8) {
 144                crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
 145                return -EINVAL;
 146        }
 147
 148        mctx->l = le32_to_cpu(data[0]);
 149        mctx->r = le32_to_cpu(data[1]);
 150        return 0;
 151}
 152
 153static struct shash_alg alg = {
 154        .digestsize             =       8,
 155        .setkey                 =       michael_setkey,
 156        .init                   =       michael_init,
 157        .update                 =       michael_update,
 158        .final                  =       michael_final,
 159        .descsize               =       sizeof(struct michael_mic_desc_ctx),
 160        .base                   =       {
 161                .cra_name               =       "michael_mic",
 162                .cra_blocksize          =       8,
 163                .cra_alignmask          =       3,
 164                .cra_ctxsize            =       sizeof(struct michael_mic_ctx),
 165                .cra_module             =       THIS_MODULE,
 166        }
 167};
 168
 169static int __init michael_mic_init(void)
 170{
 171        return crypto_register_shash(&alg);
 172}
 173
 174
 175static void __exit michael_mic_exit(void)
 176{
 177        crypto_unregister_shash(&alg);
 178}
 179
 180
 181module_init(michael_mic_init);
 182module_exit(michael_mic_exit);
 183
 184MODULE_LICENSE("GPL v2");
 185MODULE_DESCRIPTION("Michael MIC");
 186MODULE_AUTHOR("Jouni Malinen <j@w1.fi>");
 187
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