/* LRW: as defined by Cyril Guyot in
 *      http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
 *
 * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
 *
 * Based on ecb.c
 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
 *
 * 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/stds-p1619@listserv.ieee.org/msg00173.html
 *
 * The test vectors are included in the testing module tcrypt.[ch] */

#include <crypto/internal/skcipher.h>
#include <crypto/scatterwalk.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>

#define LRW_BUFFER_SIZE 128u

#define LRW_BLOCK_SIZE 16

struct priv {
        struct crypto_skcipher *child;

        /*
         * optimizes multiplying a random (non incrementing, as at the
         * start of a new sector) value with key2, we could also have
         * used 4k optimization tables or no optimization at all. In the
         * latter case we would have to store key2 here
         */
        struct gf128mul_64k *table;

        /*
         * stores:
         *  key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
         *  key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
         *  key2*{ 0,0,...1,1,1,1,1 }, etc
         * needed for optimized multiplication of incrementing values
         * with key2
         */
        be128 mulinc[128];
};

struct rctx {
        be128 buf[LRW_BUFFER_SIZE / sizeof(be128)];

        be128 t;

        be128 *ext;

        struct scatterlist srcbuf[2];
        struct scatterlist dstbuf[2];
        struct scatterlist *src;
        struct scatterlist *dst;

        unsigned int left;

        struct skcipher_request subreq;
};

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);
}

static int setkey(struct crypto_skcipher *parent, const u8 *key,
                  unsigned int keylen)
{
        struct priv *ctx = crypto_skcipher_ctx(parent);
        struct crypto_skcipher *child = ctx->child;
        int err, bsize = LRW_BLOCK_SIZE;
        const u8 *tweak = key + keylen - bsize;
        be128 tmp = { 0 };
        int i;

        crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
        crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
                                         CRYPTO_TFM_REQ_MASK);
        err = crypto_skcipher_setkey(child, key, keylen - bsize);
        crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
                                          CRYPTO_TFM_RES_MASK);
        if (err)
                return err;

        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;
}

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

/* 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 post_crypt(struct skcipher_request *req)
{
        struct rctx *rctx = skcipher_request_ctx(req);
        be128 *buf = rctx->ext ?: rctx->buf;
        struct skcipher_request *subreq;
        const int bs = LRW_BLOCK_SIZE;
        struct skcipher_walk w;
        struct scatterlist *sg;
        unsigned offset;
        int err;

        subreq = &rctx->subreq;
        err = skcipher_walk_virt(&w, subreq, false);

        while (w.nbytes) {
                unsigned int avail = w.nbytes;
                be128 *wdst;

                wdst = w.dst.virt.addr;

                do {
                        be128_xor(wdst, buf++, wdst);
                        wdst++;
                } while ((avail -= bs) >= bs);

                err = skcipher_walk_done(&w, avail);
        }

        rctx->left -= subreq->cryptlen;

        if (err || !rctx->left)
                goto out;

        rctx->dst = rctx->dstbuf;

        scatterwalk_done(&w.out, 0, 1);
        sg = w.out.sg;
        offset = w.out.offset;

        if (rctx->dst != sg) {
                rctx->dst[0] = *sg;
                sg_unmark_end(rctx->dst);
                scatterwalk_crypto_chain(rctx->dst, sg_next(sg), 0, 2);
        }
        rctx->dst[0].length -= offset - sg->offset;
        rctx->dst[0].offset = offset;

out:
        return err;
}

static int pre_crypt(struct skcipher_request *req)
{
        struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
        struct rctx *rctx = skcipher_request_ctx(req);
        struct priv *ctx = crypto_skcipher_ctx(tfm);
        be128 *buf = rctx->ext ?: rctx->buf;
        struct skcipher_request *subreq;
        const int bs = LRW_BLOCK_SIZE;
        struct skcipher_walk w;
        struct scatterlist *sg;
        unsigned cryptlen;
        unsigned offset;
        be128 *iv;
        bool more;
        int err;

        subreq = &rctx->subreq;
        skcipher_request_set_tfm(subreq, tfm);

        cryptlen = subreq->cryptlen;
        more = rctx->left > cryptlen;
        if (!more)
                cryptlen = rctx->left;

        skcipher_request_set_crypt(subreq, rctx->src, rctx->dst,
                                   cryptlen, req->iv);

        err = skcipher_walk_virt(&w, subreq, false);
        iv = w.iv;

        while (w.nbytes) {
                unsigned int avail = w.nbytes;
                be128 *wsrc;
                be128 *wdst;

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

                do {
                        *buf++ = rctx->t;
                        be128_xor(wdst++, &rctx->t, wsrc++);

                        /* T <- I*Key2, using the optimization
                         * discussed in the specification */
                        be128_xor(&rctx->t, &rctx->t,
                                  &ctx->mulinc[get_index128(iv)]);
                        inc(iv);
                } while ((avail -= bs) >= bs);

                err = skcipher_walk_done(&w, avail);
        }

        skcipher_request_set_tfm(subreq, ctx->child);
        skcipher_request_set_crypt(subreq, rctx->dst, rctx->dst,
                                   cryptlen, NULL);

        if (err || !more)
                goto out;

        rctx->src = rctx->srcbuf;

        scatterwalk_done(&w.in, 0, 1);
        sg = w.in.sg;
        offset = w.in.offset;

        if (rctx->src != sg) {
                rctx->src[0] = *sg;
                sg_unmark_end(rctx->src);
                scatterwalk_crypto_chain(rctx->src, sg_next(sg), 0, 2);
        }
        rctx->src[0].length -= offset - sg->offset;
        rctx->src[0].offset = offset;

out:
        return err;
}

static int init_crypt(struct skcipher_request *req, crypto_completion_t done)
{
        struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
        struct rctx *rctx = skcipher_request_ctx(req);
        struct skcipher_request *subreq;
        gfp_t gfp;

        subreq = &rctx->subreq;
        skcipher_request_set_callback(subreq, req->base.flags, done, req);

        gfp = req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL :
                                                           GFP_ATOMIC;
        rctx->ext = NULL;

        subreq->cryptlen = LRW_BUFFER_SIZE;
        if (req->cryptlen > LRW_BUFFER_SIZE) {
                unsigned int n = min(req->cryptlen, (unsigned int)PAGE_SIZE);

                rctx->ext = kmalloc(n, gfp);
                if (rctx->ext)
                        subreq->cryptlen = n;
        }

        rctx->src = req->src;
        rctx->dst = req->dst;
        rctx->left = req->cryptlen;

        /* calculate first value of T */
        memcpy(&rctx->t, req->iv, sizeof(rctx->t));

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

        return 0;
}

static void exit_crypt(struct skcipher_request *req)
{
        struct rctx *rctx = skcipher_request_ctx(req);

        rctx->left = 0;

        if (rctx->ext)
                kzfree(rctx->ext);
}

static int do_encrypt(struct skcipher_request *req, int err)
{
        struct rctx *rctx = skcipher_request_ctx(req);
        struct skcipher_request *subreq;

        subreq = &rctx->subreq;

        while (!err && rctx->left) {
                err = pre_crypt(req) ?:
                      crypto_skcipher_encrypt(subreq) ?:
                      post_crypt(req);

                if (err == -EINPROGRESS || err == -EBUSY)
                        return err;
        }

        exit_crypt(req);
        return err;
}

static void encrypt_done(struct crypto_async_request *areq, int err)
{
        struct skcipher_request *req = areq->data;
        struct skcipher_request *subreq;
        struct rctx *rctx;

        rctx = skcipher_request_ctx(req);

        if (err == -EINPROGRESS) {
                if (rctx->left != req->cryptlen)
                        return;
                goto out;
        }

        subreq = &rctx->subreq;
        subreq->base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;

        err = do_encrypt(req, err ?: post_crypt(req));
        if (rctx->left)
                return;

out:
        skcipher_request_complete(req, err);
}

static int encrypt(struct skcipher_request *req)
{
        return do_encrypt(req, init_crypt(req, encrypt_done));
}

static int do_decrypt(struct skcipher_request *req, int err)
{
        struct rctx *rctx = skcipher_request_ctx(req);
        struct skcipher_request *subreq;

        subreq = &rctx->subreq;

        while (!err && rctx->left) {
                err = pre_crypt(req) ?:
                      crypto_skcipher_decrypt(subreq) ?:
                      post_crypt(req);

                if (err == -EINPROGRESS || err == -EBUSY)
                        return err;
        }

        exit_crypt(req);
        return err;
}

static void decrypt_done(struct crypto_async_request *areq, int err)
{
        struct skcipher_request *req = areq->data;
        struct skcipher_request *subreq;
        struct rctx *rctx;

        rctx = skcipher_request_ctx(req);

        if (err == -EINPROGRESS) {
                if (rctx->left != req->cryptlen)
                        return;
                goto out;
        }

        subreq = &rctx->subreq;
        subreq->base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;

        err = do_decrypt(req, err ?: post_crypt(req));
        if (rctx->left)
                return;

out:
        skcipher_request_complete(req, err);
}

static int decrypt(struct skcipher_request *req)
{
        return do_decrypt(req, init_crypt(req, decrypt_done));
}

static int init_tfm(struct crypto_skcipher *tfm)
{
        struct skcipher_instance *inst = skcipher_alg_instance(tfm);
        struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
        struct priv *ctx = crypto_skcipher_ctx(tfm);
        struct crypto_skcipher *cipher;

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

        ctx->child = cipher;

        crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
                                         sizeof(struct rctx));

        return 0;
}

static void exit_tfm(struct crypto_skcipher *tfm)
{
        struct priv *ctx = crypto_skcipher_ctx(tfm);

        if (ctx->table)
                gf128mul_free_64k(ctx->table);
        crypto_free_skcipher(ctx->child);
}

static void free(struct skcipher_instance *inst)
{
        crypto_drop_skcipher(skcipher_instance_ctx(inst));
        kfree(inst);
}

static int create(struct crypto_template *tmpl, struct rtattr **tb)
{
        struct crypto_skcipher_spawn *spawn;
        struct skcipher_instance *inst;
        struct crypto_attr_type *algt;
        struct skcipher_alg *alg;
        const char *cipher_name;
        char ecb_name[CRYPTO_MAX_ALG_NAME];
        int err;

        algt = crypto_get_attr_type(tb);
        if (IS_ERR(algt))
                return PTR_ERR(algt);

        if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
                return -EINVAL;

        cipher_name = crypto_attr_alg_name(tb[1]);
        if (IS_ERR(cipher_name))
                return PTR_ERR(cipher_name);

        inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
        if (!inst)
                return -ENOMEM;

        spawn = skcipher_instance_ctx(inst);

        crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
        err = crypto_grab_skcipher(spawn, cipher_name, 0,
                                   crypto_requires_sync(algt->type,
                                                        algt->mask));
        if (err == -ENOENT) {
                err = -ENAMETOOLONG;
                if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
                             cipher_name) >= CRYPTO_MAX_ALG_NAME)
                        goto err_free_inst;

                err = crypto_grab_skcipher(spawn, ecb_name, 0,
                                           crypto_requires_sync(algt->type,
                                                                algt->mask));
        }

        if (err)
                goto err_free_inst;

        alg = crypto_skcipher_spawn_alg(spawn);

        err = -EINVAL;
        if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
                goto err_drop_spawn;

        if (crypto_skcipher_alg_ivsize(alg))
                goto err_drop_spawn;

        err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
                                  &alg->base);
        if (err)
                goto err_drop_spawn;

        err = -EINVAL;
        cipher_name = alg->base.cra_name;

        /* Alas we screwed up the naming so we have to mangle the
         * cipher name.
         */
        if (!strncmp(cipher_name, "ecb(", 4)) {
                unsigned len;

                len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
                if (len < 2 || len >= sizeof(ecb_name))
                        goto err_drop_spawn;

                if (ecb_name[len - 1] != ')')
                        goto err_drop_spawn;

                ecb_name[len - 1] = 0;

                if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
                             "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
                        err = -ENAMETOOLONG;
                        goto err_drop_spawn;
                }
        } else
                goto err_drop_spawn;

        inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
        inst->alg.base.cra_priority = alg->base.cra_priority;
        inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
        inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
                                       (__alignof__(u64) - 1);

        inst->alg.ivsize = LRW_BLOCK_SIZE;
        inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
                                LRW_BLOCK_SIZE;
        inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
                                LRW_BLOCK_SIZE;

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

        inst->alg.init = init_tfm;
        inst->alg.exit = exit_tfm;

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

        inst->free = free;

        err = skcipher_register_instance(tmpl, inst);
        if (err)
                goto err_drop_spawn;

out:
        return err;

err_drop_spawn:
        crypto_drop_skcipher(spawn);
err_free_inst:
        kfree(inst);
        goto out;
}

static struct crypto_template crypto_tmpl = {
        .name = "lrw",
        .create = create,
        .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");
MODULE_ALIAS_CRYPTO("lrw");