root/crypto/michael_mic.c

/*
 * Cryptographic API
 *
 * Michael MIC (IEEE 802.11i/TKIP) keyed digest
 *
 * Copyright (c) 2004 Jouni Malinen <jkmaline@cc.hut.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 <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/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 <jkmaline@cc.hut.fi>");