// SPDX-License-Identifier: GPL-2.0-only
/*
 * Cryptographic API
 *
 * Michael MIC (IEEE 802.11i/TKIP) keyed digest
 *
 * Copyright (c) 2004 Jouni Malinen <j@w1.fi>
 */
#include <crypto/internal/hash.h>
#include <linux/unaligned.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/types.h>


struct michael_mic_ctx {
        u32 l, r;
};

struct michael_mic_desc_ctx {
        __le32 pending;
        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 int michael_init(struct shash_desc *desc)
{
        struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);
        struct michael_mic_ctx *ctx = crypto_shash_ctx(desc->tfm);
        mctx->pending_len = 0;
        mctx->l = ctx->l;
        mctx->r = ctx->r;

        return 0;
}


static int michael_update(struct shash_desc *desc, const u8 *data,
                           unsigned int len)
{
        struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);

        if (mctx->pending_len) {
                int flen = 4 - mctx->pending_len;
                if (flen > len)
                        flen = len;
                memcpy((u8 *)&mctx->pending + mctx->pending_len, data, flen);
                mctx->pending_len += flen;
                data += flen;
                len -= flen;

                if (mctx->pending_len < 4)
                        return 0;

                mctx->l ^= le32_to_cpu(mctx->pending);
                michael_block(mctx->l, mctx->r);
                mctx->pending_len = 0;
        }

        while (len >= 4) {
                mctx->l ^= get_unaligned_le32(data);
                michael_block(mctx->l, mctx->r);
                data += 4;
                len -= 4;
        }

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

        return 0;
}


static int michael_final(struct shash_desc *desc, u8 *out)
{
        struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);
        u8 *data = (u8 *)&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_unaligned_le32(mctx->l, out);
        put_unaligned_le32(mctx->r, out + 4);

        return 0;
}


static int michael_setkey(struct crypto_shash *tfm, const u8 *key,
                          unsigned int keylen)
{
        struct michael_mic_ctx *mctx = crypto_shash_ctx(tfm);

        if (keylen != 8)
                return -EINVAL;

        mctx->l = get_unaligned_le32(key);
        mctx->r = get_unaligned_le32(key + 4);
        return 0;
}

static struct shash_alg alg = {
        .digestsize             =       8,
        .setkey                 =       michael_setkey,
        .init                   =       michael_init,
        .update                 =       michael_update,
        .final                  =       michael_final,
        .descsize               =       sizeof(struct michael_mic_desc_ctx),
        .base                   =       {
                .cra_name               =       "michael_mic",
                .cra_driver_name        =       "michael_mic-generic",
                .cra_blocksize          =       8,
                .cra_ctxsize            =       sizeof(struct michael_mic_ctx),
                .cra_module             =       THIS_MODULE,
        }
};

static int __init michael_mic_init(void)
{
        return crypto_register_shash(&alg);
}


static void __exit michael_mic_exit(void)
{
        crypto_unregister_shash(&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>");
MODULE_ALIAS_CRYPTO("michael_mic");