xcbc.c

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/*
 * Copyright (C)2006 USAGI/WIDE Project
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Author:
 *  Kazunori Miyazawa <[email protected]>
 */

#include <crypto/internal/hash.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/module.h>

static u_int32_t ks[12] = {0x01010101, 0x01010101, 0x01010101, 0x01010101,
               0x02020202, 0x02020202, 0x02020202, 0x02020202,
               0x03030303, 0x03030303, 0x03030303, 0x03030303};

/*
 * +------------------------
 * | <parent tfm>
 * +------------------------
 * | xcbc_tfm_ctx
 * +------------------------
 * | consts (block size * 2)
 * +------------------------
 */
struct xcbc_tfm_ctx {
    struct crypto_cipher *child;
    u8 ctx[];
};

/*
 * +------------------------
 * | <shash desc>
 * +------------------------
 * | xcbc_desc_ctx
 * +------------------------
 * | odds (block size)
 * +------------------------
 * | prev (block size)
 * +------------------------
 */
struct xcbc_desc_ctx {
    unsigned int len;
    u8 ctx[];
};

static int crypto_xcbc_digest_setkey(struct crypto_shash *parent,
                     const u8 *inkey, unsigned int keylen)
{
    unsigned long alignmask = crypto_shash_alignmask(parent);
    struct xcbc_tfm_ctx *ctx = crypto_shash_ctx(parent);
    int bs = crypto_shash_blocksize(parent);
    u8 *consts = PTR_ALIGN(&ctx->ctx[0], alignmask + 1);
    int err = 0;
    u8 key1[bs];

    if ((err = crypto_cipher_setkey(ctx->child, inkey, keylen)))
        return err;

    crypto_cipher_encrypt_one(ctx->child, consts, (u8 *)ks + bs);
    crypto_cipher_encrypt_one(ctx->child, consts + bs, (u8 *)ks + bs * 2);
    crypto_cipher_encrypt_one(ctx->child, key1, (u8 *)ks);

    return crypto_cipher_setkey(ctx->child, key1, bs);

}

static int crypto_xcbc_digest_init(struct shash_desc *pdesc)
{
    unsigned long alignmask = crypto_shash_alignmask(pdesc->tfm);
    struct xcbc_desc_ctx *ctx = shash_desc_ctx(pdesc);
    int bs = crypto_shash_blocksize(pdesc->tfm);
    u8 *prev = PTR_ALIGN(&ctx->ctx[0], alignmask + 1) + bs;

    ctx->len = 0;
    memset(prev, 0, bs);

    return 0;
}

static int crypto_xcbc_digest_update(struct shash_desc *pdesc, const u8 *p,
                     unsigned int len)
{
    struct crypto_shash *parent = pdesc->tfm;
    unsigned long alignmask = crypto_shash_alignmask(parent);
    struct xcbc_tfm_ctx *tctx = crypto_shash_ctx(parent);
    struct xcbc_desc_ctx *ctx = shash_desc_ctx(pdesc);
    struct crypto_cipher *tfm = tctx->child;
    int bs = crypto_shash_blocksize(parent);
    u8 *odds = PTR_ALIGN(&ctx->ctx[0], alignmask + 1);
    u8 *prev = odds + bs;

    /* checking the data can fill the block */
    if ((ctx->len + len) <= bs) {
        memcpy(odds + ctx->len, p, len);
        ctx->len += len;
        return 0;
    }

    /* filling odds with new data and encrypting it */
    memcpy(odds + ctx->len, p, bs - ctx->len);
    len -= bs - ctx->len;
    p += bs - ctx->len;

    crypto_xor(prev, odds, bs);
    crypto_cipher_encrypt_one(tfm, prev, prev);

    /* clearing the length */
    ctx->len = 0;

    /* encrypting the rest of data */
    while (len > bs) {
        crypto_xor(prev, p, bs);
        crypto_cipher_encrypt_one(tfm, prev, prev);
        p += bs;
        len -= bs;
    }

    /* keeping the surplus of blocksize */
    if (len) {
        memcpy(odds, p, len);
        ctx->len = len;
    }

    return 0;
}

static int crypto_xcbc_digest_final(struct shash_desc *pdesc, u8 *out)
{
    struct crypto_shash *parent = pdesc->tfm;
    unsigned long alignmask = crypto_shash_alignmask(parent);
    struct xcbc_tfm_ctx *tctx = crypto_shash_ctx(parent);
    struct xcbc_desc_ctx *ctx = shash_desc_ctx(pdesc);
    struct crypto_cipher *tfm = tctx->child;
    int bs = crypto_shash_blocksize(parent);
    u8 *consts = PTR_ALIGN(&tctx->ctx[0], alignmask + 1);
    u8 *odds = PTR_ALIGN(&ctx->ctx[0], alignmask + 1);
    u8 *prev = odds + bs;
    unsigned int offset = 0;

    if (ctx->len != bs) {
        unsigned int rlen;
        u8 *p = odds + ctx->len;

        *p = 0x80;
        p++;

        rlen = bs - ctx->len -1;
        if (rlen)
            memset(p, 0, rlen);

        offset += bs;
    }

    crypto_xor(prev, odds, bs);
    crypto_xor(prev, consts + offset, bs);

    crypto_cipher_encrypt_one(tfm, out, prev);

    return 0;
}

static int xcbc_init_tfm(struct crypto_tfm *tfm)
{
    struct crypto_cipher *cipher;
    struct crypto_instance *inst = (void *)tfm->__crt_alg;
    struct crypto_spawn *spawn = crypto_instance_ctx(inst);
    struct xcbc_tfm_ctx *ctx = crypto_tfm_ctx(tfm);

    cipher = crypto_spawn_cipher(spawn);
    if (IS_ERR(cipher))
        return PTR_ERR(cipher);

    ctx->child = cipher;

    return 0;
};

static void xcbc_exit_tfm(struct crypto_tfm *tfm)
{
    struct xcbc_tfm_ctx *ctx = crypto_tfm_ctx(tfm);
    crypto_free_cipher(ctx->child);
}

static int xcbc_create(struct crypto_template *tmpl, struct rtattr **tb)
{
    struct shash_instance *inst;
    struct crypto_alg *alg;
    unsigned long alignmask;
    int err;

    err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH);
    if (err)
        return err;

    alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
                  CRYPTO_ALG_TYPE_MASK);
    if (IS_ERR(alg))
        return PTR_ERR(alg);

    switch(alg->cra_blocksize) {
    case 16:
        break;
    default:
        goto out_put_alg;
    }

    inst = shash_alloc_instance("xcbc", alg);
    err = PTR_ERR(inst);
    if (IS_ERR(inst))
        goto out_put_alg;

    err = crypto_init_spawn(shash_instance_ctx(inst), alg,
                shash_crypto_instance(inst),
                CRYPTO_ALG_TYPE_MASK);
    if (err)
        goto out_free_inst;

    alignmask = alg->cra_alignmask | 3;
    inst->alg.base.cra_alignmask = alignmask;
    inst->alg.base.cra_priority = alg->cra_priority;
    inst->alg.base.cra_blocksize = alg->cra_blocksize;

    inst->alg.digestsize = alg->cra_blocksize;
    inst->alg.descsize = ALIGN(sizeof(struct xcbc_desc_ctx),
                   crypto_tfm_ctx_alignment()) +
                 (alignmask &
                  ~(crypto_tfm_ctx_alignment() - 1)) +
                 alg->cra_blocksize * 2;

    inst->alg.base.cra_ctxsize = ALIGN(sizeof(struct xcbc_tfm_ctx),
                       alignmask + 1) +
                     alg->cra_blocksize * 2;
    inst->alg.base.cra_init = xcbc_init_tfm;
    inst->alg.base.cra_exit = xcbc_exit_tfm;

    inst->alg.init = crypto_xcbc_digest_init;
    inst->alg.update = crypto_xcbc_digest_update;
    inst->alg.final = crypto_xcbc_digest_final;
    inst->alg.setkey = crypto_xcbc_digest_setkey;

    err = shash_register_instance(tmpl, inst);
    if (err) {
out_free_inst:
        shash_free_instance(shash_crypto_instance(inst));
    }

out_put_alg:
    crypto_mod_put(alg);
    return err;
}

static struct crypto_template crypto_xcbc_tmpl = {
    .name = "xcbc",
    .create = xcbc_create,
    .free = shash_free_instance,
    .module = THIS_MODULE,
};

static int __init crypto_xcbc_module_init(void)
{
    return crypto_register_template(&crypto_xcbc_tmpl);
}

static void __exit crypto_xcbc_module_exit(void)
{
    crypto_unregister_template(&crypto_xcbc_tmpl);
}

module_init(crypto_xcbc_module_init);
module_exit(crypto_xcbc_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("XCBC keyed hash algorithm");