michael_mic.c

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/*
 * Cryptographic API
 *
 * Michael MIC (IEEE 802.11i/TKIP) keyed digest
 *
 * Copyright (c) 2004 Jouni Malinen <[email protected]>
 *
 * 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 <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
//#include <linux/crypto.h>
#include "rtl_crypto.h"


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

    u32 l, r;
};


static inline u32 rotl(u32 val, int bits)
{
    return (val << bits) | (val >> (32 - bits));
}


static inline u32 rotr(u32 val, int bits)
{
    return (val >> bits) | (val << (32 - bits));
}


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


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


static inline u32 get_le32(const u8 *p)
{
    return p[0] | (p[1] << 8) | (p[2] << 16) | (p[3] << 24);
}


static inline void put_le32(u8 *p, u32 v)
{
    p[0] = v;
    p[1] = v >> 8;
    p[2] = v >> 16;
    p[3] = v >> 24;
}


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


static void michael_update(void *ctx, const u8 *data, unsigned int len)
{
    struct michael_mic_ctx *mctx = ctx;

    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;

        mctx->l ^= get_le32(mctx->pending);
        michael_block(mctx->l, mctx->r);
        mctx->pending_len = 0;
    }

    while (len >= 4) {
        mctx->l ^= get_le32(data);
        michael_block(mctx->l, mctx->r);
        data += 4;
        len -= 4;
    }

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


static void michael_final(void *ctx, u8 *out)
{
    struct michael_mic_ctx *mctx = ctx;
    u8 *data = mctx->pending;

    /* 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);

    put_le32(out, mctx->l);
    put_le32(out + 4, mctx->r);
}


static int michael_setkey(void *ctx, const u8 *key, unsigned int keylen,
              u32 *flags)
{
    struct michael_mic_ctx *mctx = ctx;
    if (keylen != 8) {
        if (flags)
            *flags = CRYPTO_TFM_RES_BAD_KEY_LEN;
        return -EINVAL;
    }
    mctx->l = get_le32(key);
    mctx->r = get_le32(key + 4);
    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_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 <[email protected]>");