lrw.c

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/* LRW: as defined by Cyril Guyot in
 *  http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
 *
 * Copyright (c) 2006 Rik Snel <[email protected]>
 *
 * Based on ecb.c
 * Copyright (c) 2006 Herbert Xu <[email protected]>
 *
 * 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 implementation is checked against the test vectors in the above
 * document and by a test vector provided by Ken Buchanan at
 * http://www.mail-archive.com/[email protected]/msg00173.html
 *
 * The test vectors are included in the testing module tcrypt.[ch] */

#include <crypto/algapi.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>

#include <crypto/b128ops.h>
#include <crypto/gf128mul.h>
#include <crypto/lrw.h>

struct priv {
    struct crypto_cipher *child;
    struct lrw_table_ctx table;
};

static inline void setbit128_bbe(void *b, int bit)
{
    __set_bit(bit ^ (0x80 -
#ifdef __BIG_ENDIAN
             BITS_PER_LONG
#else
             BITS_PER_BYTE
#endif
            ), b);
}

int lrw_init_table(struct lrw_table_ctx *ctx, const u8 *tweak)
{
    be128 tmp = { 0 };
    int i;

    if (ctx->table)
        gf128mul_free_64k(ctx->table);

    /* initialize multiplication table for Key2 */
    ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
    if (!ctx->table)
        return -ENOMEM;

    /* initialize optimization table */
    for (i = 0; i < 128; i++) {
        setbit128_bbe(&tmp, i);
        ctx->mulinc[i] = tmp;
        gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
    }

    return 0;
}
EXPORT_SYMBOL_GPL(lrw_init_table);

void lrw_free_table(struct lrw_table_ctx *ctx)
{
    if (ctx->table)
        gf128mul_free_64k(ctx->table);
}
EXPORT_SYMBOL_GPL(lrw_free_table);

static int setkey(struct crypto_tfm *parent, const u8 *key,
          unsigned int keylen)
{
    struct priv *ctx = crypto_tfm_ctx(parent);
    struct crypto_cipher *child = ctx->child;
    int err, bsize = LRW_BLOCK_SIZE;
    const u8 *tweak = key + keylen - bsize;

    crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
    crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
                       CRYPTO_TFM_REQ_MASK);
    err = crypto_cipher_setkey(child, key, keylen - bsize);
    if (err)
        return err;
    crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
                     CRYPTO_TFM_RES_MASK);

    return lrw_init_table(&ctx->table, tweak);
}

struct sinfo {
    be128 t;
    struct crypto_tfm *tfm;
    void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
};

static inline void inc(be128 *iv)
{
    be64_add_cpu(&iv->b, 1);
    if (!iv->b)
        be64_add_cpu(&iv->a, 1);
}

static inline void lrw_round(struct sinfo *s, void *dst, const void *src)
{
    be128_xor(dst, &s->t, src);     /* PP <- T xor P */
    s->fn(s->tfm, dst, dst);        /* CC <- E(Key2,PP) */
    be128_xor(dst, dst, &s->t);     /* C <- T xor CC */
}

/* this returns the number of consequative 1 bits starting
 * from the right, get_index128(00 00 00 00 00 00 ... 00 00 10 FB) = 2 */
static inline int get_index128(be128 *block)
{
    int x;
    __be32 *p = (__be32 *) block;

    for (p += 3, x = 0; x < 128; p--, x += 32) {
        u32 val = be32_to_cpup(p);

        if (!~val)
            continue;

        return x + ffz(val);
    }

    return x;
}

static int crypt(struct blkcipher_desc *d,
         struct blkcipher_walk *w, struct priv *ctx,
         void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
{
    int err;
    unsigned int avail;
    const int bs = LRW_BLOCK_SIZE;
    struct sinfo s = {
        .tfm = crypto_cipher_tfm(ctx->child),
        .fn = fn
    };
    be128 *iv;
    u8 *wsrc;
    u8 *wdst;

    err = blkcipher_walk_virt(d, w);
    if (!(avail = w->nbytes))
        return err;

    wsrc = w->src.virt.addr;
    wdst = w->dst.virt.addr;

    /* calculate first value of T */
    iv = (be128 *)w->iv;
    s.t = *iv;

    /* T <- I*Key2 */
    gf128mul_64k_bbe(&s.t, ctx->table.table);

    goto first;

    for (;;) {
        do {
            /* T <- I*Key2, using the optimization
             * discussed in the specification */
            be128_xor(&s.t, &s.t,
                  &ctx->table.mulinc[get_index128(iv)]);
            inc(iv);

first:
            lrw_round(&s, wdst, wsrc);

            wsrc += bs;
            wdst += bs;
        } while ((avail -= bs) >= bs);

        err = blkcipher_walk_done(d, w, avail);
        if (!(avail = w->nbytes))
            break;

        wsrc = w->src.virt.addr;
        wdst = w->dst.virt.addr;
    }

    return err;
}

static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
           struct scatterlist *src, unsigned int nbytes)
{
    struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
    struct blkcipher_walk w;

    blkcipher_walk_init(&w, dst, src, nbytes);
    return crypt(desc, &w, ctx,
             crypto_cipher_alg(ctx->child)->cia_encrypt);
}

static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
           struct scatterlist *src, unsigned int nbytes)
{
    struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
    struct blkcipher_walk w;

    blkcipher_walk_init(&w, dst, src, nbytes);
    return crypt(desc, &w, ctx,
             crypto_cipher_alg(ctx->child)->cia_decrypt);
}

int lrw_crypt(struct blkcipher_desc *desc, struct scatterlist *sdst,
          struct scatterlist *ssrc, unsigned int nbytes,
          struct lrw_crypt_req *req)
{
    const unsigned int bsize = LRW_BLOCK_SIZE;
    const unsigned int max_blks = req->tbuflen / bsize;
    struct lrw_table_ctx *ctx = req->table_ctx;
    struct blkcipher_walk walk;
    unsigned int nblocks;
    be128 *iv, *src, *dst, *t;
    be128 *t_buf = req->tbuf;
    int err, i;

    BUG_ON(max_blks < 1);

    blkcipher_walk_init(&walk, sdst, ssrc, nbytes);

    err = blkcipher_walk_virt(desc, &walk);
    nbytes = walk.nbytes;
    if (!nbytes)
        return err;

    nblocks = min(walk.nbytes / bsize, max_blks);
    src = (be128 *)walk.src.virt.addr;
    dst = (be128 *)walk.dst.virt.addr;

    /* calculate first value of T */
    iv = (be128 *)walk.iv;
    t_buf[0] = *iv;

    /* T <- I*Key2 */
    gf128mul_64k_bbe(&t_buf[0], ctx->table);

    i = 0;
    goto first;

    for (;;) {
        do {
            for (i = 0; i < nblocks; i++) {
                /* T <- I*Key2, using the optimization
                 * discussed in the specification */
                be128_xor(&t_buf[i], t,
                        &ctx->mulinc[get_index128(iv)]);
                inc(iv);
first:
                t = &t_buf[i];

                /* PP <- T xor P */
                be128_xor(dst + i, t, src + i);
            }

            /* CC <- E(Key2,PP) */
            req->crypt_fn(req->crypt_ctx, (u8 *)dst,
                      nblocks * bsize);

            /* C <- T xor CC */
            for (i = 0; i < nblocks; i++)
                be128_xor(dst + i, dst + i, &t_buf[i]);

            src += nblocks;
            dst += nblocks;
            nbytes -= nblocks * bsize;
            nblocks = min(nbytes / bsize, max_blks);
        } while (nblocks > 0);

        err = blkcipher_walk_done(desc, &walk, nbytes);
        nbytes = walk.nbytes;
        if (!nbytes)
            break;

        nblocks = min(nbytes / bsize, max_blks);
        src = (be128 *)walk.src.virt.addr;
        dst = (be128 *)walk.dst.virt.addr;
    }

    return err;
}
EXPORT_SYMBOL_GPL(lrw_crypt);

static int 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 priv *ctx = crypto_tfm_ctx(tfm);
    u32 *flags = &tfm->crt_flags;

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

    if (crypto_cipher_blocksize(cipher) != LRW_BLOCK_SIZE) {
        *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
        crypto_free_cipher(cipher);
        return -EINVAL;
    }

    ctx->child = cipher;
    return 0;
}

static void exit_tfm(struct crypto_tfm *tfm)
{
    struct priv *ctx = crypto_tfm_ctx(tfm);

    lrw_free_table(&ctx->table);
    crypto_free_cipher(ctx->child);
}

static struct crypto_instance *alloc(struct rtattr **tb)
{
    struct crypto_instance *inst;
    struct crypto_alg *alg;
    int err;

    err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
    if (err)
        return ERR_PTR(err);

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

    inst = crypto_alloc_instance("lrw", alg);
    if (IS_ERR(inst))
        goto out_put_alg;

    inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
    inst->alg.cra_priority = alg->cra_priority;
    inst->alg.cra_blocksize = alg->cra_blocksize;

    if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7;
    else inst->alg.cra_alignmask = alg->cra_alignmask;
    inst->alg.cra_type = &crypto_blkcipher_type;

    if (!(alg->cra_blocksize % 4))
        inst->alg.cra_alignmask |= 3;
    inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
    inst->alg.cra_blkcipher.min_keysize =
        alg->cra_cipher.cia_min_keysize + alg->cra_blocksize;
    inst->alg.cra_blkcipher.max_keysize =
        alg->cra_cipher.cia_max_keysize + alg->cra_blocksize;

    inst->alg.cra_ctxsize = sizeof(struct priv);

    inst->alg.cra_init = init_tfm;
    inst->alg.cra_exit = exit_tfm;

    inst->alg.cra_blkcipher.setkey = setkey;
    inst->alg.cra_blkcipher.encrypt = encrypt;
    inst->alg.cra_blkcipher.decrypt = decrypt;

out_put_alg:
    crypto_mod_put(alg);
    return inst;
}

static void free(struct crypto_instance *inst)
{
    crypto_drop_spawn(crypto_instance_ctx(inst));
    kfree(inst);
}

static struct crypto_template crypto_tmpl = {
    .name = "lrw",
    .alloc = alloc,
    .free = free,
    .module = THIS_MODULE,
};

static int __init crypto_module_init(void)
{
    return crypto_register_template(&crypto_tmpl);
}

static void __exit crypto_module_exit(void)
{
    crypto_unregister_template(&crypto_tmpl);
}

module_init(crypto_module_init);
module_exit(crypto_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("LRW block cipher mode");