root/crypto/michael_mic.c

DEFINITIONS

1. xswap
2. michael_init
3. michael_update
4. michael_final
5. michael_setkey
6. michael_mic_init
7. michael_mic_exit

/*
 * Cryptographic API
 *
 * Michael MIC (IEEE 802.11i/TKIP) keyed digest
 *
 * Copyright (c) 2004 Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <asm/byteorder.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/crypto.h>
#include <linux/types.h>


struct michael_mic_ctx {
        u8 pending[4];
        size_t pending_len;

        u32 l, r;
};


static inline u32 xswap(u32 val)
{
        return ((val & 0x00ff00ff) << 8) | ((val & 0xff00ff00) >> 8);
}


#define michael_block(l, r)     \
do {                            \
        r ^= rol32(l, 17);      \
        l += r;                 \
        r ^= xswap(l);          \
        l += r;                 \
        r ^= rol32(l, 3);       \
        l += r;                 \
        r ^= ror32(l, 2);       \
        l += r;                 \
} while (0)


static void michael_init(struct crypto_tfm *tfm)
{
        struct michael_mic_ctx *mctx = crypto_tfm_ctx(tfm);
        mctx->pending_len = 0;
}


static void michael_update(struct crypto_tfm *tfm, const u8 *data,
                           unsigned int len)
{
        struct michael_mic_ctx *mctx = crypto_tfm_ctx(tfm);
        const __le32 *src;

        if (mctx->pending_len) {
                int flen = 4 - mctx->pending_len;
                if (flen > len)
                        flen = len;
                memcpy(&mctx->pending[mctx->pending_len], data, flen);
                mctx->pending_len += flen;
                data += flen;
                len -= flen;

                if (mctx->pending_len < 4)
                        return;

                src = (const __le32 *)mctx->pending;
                mctx->l ^= le32_to_cpup(src);
                michael_block(mctx->l, mctx->r);
                mctx->pending_len = 0;
        }

        src = (const __le32 *)data;

        while (len >= 4) {
                mctx->l ^= le32_to_cpup(src++);
                michael_block(mctx->l, mctx->r);
                len -= 4;
        }

        if (len > 0) {
                mctx->pending_len = len;
                memcpy(mctx->pending, src, len);
        }
}


static void michael_final(struct crypto_tfm *tfm, u8 *out)
{
        struct michael_mic_ctx *mctx = crypto_tfm_ctx(tfm);
        u8 *data = mctx->pending;
        __le32 *dst = (__le32 *)out;

        /* Last block and padding (0x5a, 4..7 x 0) */
        switch (mctx->pending_len) {
        case 0:
                mctx->l ^= 0x5a;
                break;
        case 1:
                mctx->l ^= data[0] | 0x5a00;
                break;
        case 2:
                mctx->l ^= data[0] | (data[1] << 8) | 0x5a0000;
                break;
        case 3:
                mctx->l ^= data[0] | (data[1] << 8) | (data[2] << 16) |
                        0x5a000000;
                break;
        }
        michael_block(mctx->l, mctx->r);
        /* l ^= 0; */
        michael_block(mctx->l, mctx->r);

        dst[0] = cpu_to_le32(mctx->l);
        dst[1] = cpu_to_le32(mctx->r);
}


static int michael_setkey(struct crypto_tfm *tfm, const u8 *key,
                          unsigned int keylen)
{
        struct michael_mic_ctx *mctx = crypto_tfm_ctx(tfm);
        const __le32 *data = (const __le32 *)key;

        if (keylen != 8) {
                tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
                return -EINVAL;
        }

        mctx->l = le32_to_cpu(data[0]);
        mctx->r = le32_to_cpu(data[1]);
        return 0;
}


static struct crypto_alg michael_mic_alg = {
        .cra_name       = "michael_mic",
        .cra_flags      = CRYPTO_ALG_TYPE_DIGEST,
        .cra_blocksize  = 8,
        .cra_ctxsize    = sizeof(struct michael_mic_ctx),
        .cra_module     = THIS_MODULE,
        .cra_alignmask  = 3,
        .cra_list       = LIST_HEAD_INIT(michael_mic_alg.cra_list),
        .cra_u          = { .digest = {
        .dia_digestsize = 8,
        .dia_init       = michael_init,
        .dia_update     = michael_update,
        .dia_final      = michael_final,
        .dia_setkey     = michael_setkey } }
};


static int __init michael_mic_init(void)
{
        return crypto_register_alg(&michael_mic_alg);
}


static void __exit michael_mic_exit(void)
{
        crypto_unregister_alg(&michael_mic_alg);
}


module_init(michael_mic_init);
module_exit(michael_mic_exit);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Michael MIC");
MODULE_AUTHOR("Jouni Malinen <j@w1.fi>");