// SPDX-License-Identifier: GPL-2.0-or-later
/* XTS: as defined in IEEE1619/D16
 *      http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
 *
 * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
 *
 * Based on ecb.c
 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
 */
#include <crypto/internal/cipher.h>
#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/xts.h>
#include <crypto/b128ops.h>
#include <crypto/gf128mul.h>

struct xts_tfm_ctx {
        struct crypto_skcipher *child;
        struct crypto_cipher *tweak;
};

struct xts_instance_ctx {
        struct crypto_skcipher_spawn spawn;
        struct crypto_cipher_spawn tweak_spawn;
};

struct xts_request_ctx {
        le128 t;
        struct scatterlist *tail;
        struct scatterlist sg[2];
        struct skcipher_request subreq;
};

static int xts_setkey(struct crypto_skcipher *parent, const u8 *key,
                      unsigned int keylen)
{
        struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(parent);
        struct crypto_skcipher *child;
        struct crypto_cipher *tweak;
        int err;

        err = xts_verify_key(parent, key, keylen);
        if (err)
                return err;

        keylen /= 2;

        /* we need two cipher instances: one to compute the initial 'tweak'
         * by encrypting the IV (usually the 'plain' iv) and the other
         * one to encrypt and decrypt the data */

        /* tweak cipher, uses Key2 i.e. the second half of *key */
        tweak = ctx->tweak;
        crypto_cipher_clear_flags(tweak, CRYPTO_TFM_REQ_MASK);
        crypto_cipher_set_flags(tweak, crypto_skcipher_get_flags(parent) &
                                       CRYPTO_TFM_REQ_MASK);
        err = crypto_cipher_setkey(tweak, key + keylen, keylen);
        if (err)
                return err;

        /* data cipher, uses Key1 i.e. the first half of *key */
        child = ctx->child;
        crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
        crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
                                         CRYPTO_TFM_REQ_MASK);
        return crypto_skcipher_setkey(child, key, keylen);
}

/*
 * We compute the tweak masks twice (both before and after the ECB encryption or
 * decryption) to avoid having to allocate a temporary buffer and/or make
 * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
 * just doing the gf128mul_x_ble() calls again.
 */
static int xts_xor_tweak(struct skcipher_request *req, bool second_pass,
                         bool enc)
{
        struct xts_request_ctx *rctx = skcipher_request_ctx(req);
        struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
        const bool cts = (req->cryptlen % XTS_BLOCK_SIZE);
        const int bs = XTS_BLOCK_SIZE;
        struct skcipher_walk w;
        le128 t = rctx->t;
        int err;

        if (second_pass) {
                req = &rctx->subreq;
                /* set to our TFM to enforce correct alignment: */
                skcipher_request_set_tfm(req, tfm);
        }
        err = skcipher_walk_virt(&w, req, false);

        while (w.nbytes) {
                unsigned int avail = w.nbytes;
                const le128 *wsrc;
                le128 *wdst;

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

                do {
                        if (unlikely(cts) &&
                            w.total - w.nbytes + avail < 2 * XTS_BLOCK_SIZE) {
                                if (!enc) {
                                        if (second_pass)
                                                rctx->t = t;
                                        gf128mul_x_ble(&t, &t);
                                }
                                le128_xor(wdst, &t, wsrc);
                                if (enc && second_pass)
                                        gf128mul_x_ble(&rctx->t, &t);
                                skcipher_walk_done(&w, avail - bs);
                                return 0;
                        }

                        le128_xor(wdst++, &t, wsrc++);
                        gf128mul_x_ble(&t, &t);
                } while ((avail -= bs) >= bs);

                err = skcipher_walk_done(&w, avail);
        }

        return err;
}

static int xts_xor_tweak_pre(struct skcipher_request *req, bool enc)
{
        return xts_xor_tweak(req, false, enc);
}

static int xts_xor_tweak_post(struct skcipher_request *req, bool enc)
{
        return xts_xor_tweak(req, true, enc);
}

static void xts_cts_done(void *data, int err)
{
        struct skcipher_request *req = data;
        le128 b;

        if (!err) {
                struct xts_request_ctx *rctx = skcipher_request_ctx(req);

                scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
                le128_xor(&b, &rctx->t, &b);
                scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 1);
        }

        skcipher_request_complete(req, err);
}

static int xts_cts_final(struct skcipher_request *req,
                         int (*crypt)(struct skcipher_request *req))
{
        const struct xts_tfm_ctx *ctx =
                crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
        int offset = req->cryptlen & ~(XTS_BLOCK_SIZE - 1);
        struct xts_request_ctx *rctx = skcipher_request_ctx(req);
        struct skcipher_request *subreq = &rctx->subreq;
        int tail = req->cryptlen % XTS_BLOCK_SIZE;
        le128 b[2];
        int err;

        rctx->tail = scatterwalk_ffwd(rctx->sg, req->dst,
                                      offset - XTS_BLOCK_SIZE);

        scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
        b[1] = b[0];
        scatterwalk_map_and_copy(b, req->src, offset, tail, 0);

        le128_xor(b, &rctx->t, b);

        scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE + tail, 1);

        skcipher_request_set_tfm(subreq, ctx->child);
        skcipher_request_set_callback(subreq, req->base.flags, xts_cts_done,
                                      req);
        skcipher_request_set_crypt(subreq, rctx->tail, rctx->tail,
                                   XTS_BLOCK_SIZE, NULL);

        err = crypt(subreq);
        if (err)
                return err;

        scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0);
        le128_xor(b, &rctx->t, b);
        scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 1);

        return 0;
}

static void xts_encrypt_done(void *data, int err)
{
        struct skcipher_request *req = data;

        if (!err) {
                struct xts_request_ctx *rctx = skcipher_request_ctx(req);

                rctx->subreq.base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;
                err = xts_xor_tweak_post(req, true);

                if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
                        err = xts_cts_final(req, crypto_skcipher_encrypt);
                        if (err == -EINPROGRESS || err == -EBUSY)
                                return;
                }
        }

        skcipher_request_complete(req, err);
}

static void xts_decrypt_done(void *data, int err)
{
        struct skcipher_request *req = data;

        if (!err) {
                struct xts_request_ctx *rctx = skcipher_request_ctx(req);

                rctx->subreq.base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;
                err = xts_xor_tweak_post(req, false);

                if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
                        err = xts_cts_final(req, crypto_skcipher_decrypt);
                        if (err == -EINPROGRESS || err == -EBUSY)
                                return;
                }
        }

        skcipher_request_complete(req, err);
}

static int xts_init_crypt(struct skcipher_request *req,
                          crypto_completion_t compl)
{
        const struct xts_tfm_ctx *ctx =
                crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
        struct xts_request_ctx *rctx = skcipher_request_ctx(req);
        struct skcipher_request *subreq = &rctx->subreq;

        if (req->cryptlen < XTS_BLOCK_SIZE)
                return -EINVAL;

        skcipher_request_set_tfm(subreq, ctx->child);
        skcipher_request_set_callback(subreq, req->base.flags, compl, req);
        skcipher_request_set_crypt(subreq, req->dst, req->dst,
                                   req->cryptlen & ~(XTS_BLOCK_SIZE - 1), NULL);

        /* calculate first value of T */
        crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv);

        return 0;
}

static int xts_encrypt(struct skcipher_request *req)
{
        struct xts_request_ctx *rctx = skcipher_request_ctx(req);
        struct skcipher_request *subreq = &rctx->subreq;
        int err;

        err = xts_init_crypt(req, xts_encrypt_done) ?:
              xts_xor_tweak_pre(req, true) ?:
              crypto_skcipher_encrypt(subreq) ?:
              xts_xor_tweak_post(req, true);

        if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
                return err;

        return xts_cts_final(req, crypto_skcipher_encrypt);
}

static int xts_decrypt(struct skcipher_request *req)
{
        struct xts_request_ctx *rctx = skcipher_request_ctx(req);
        struct skcipher_request *subreq = &rctx->subreq;
        int err;

        err = xts_init_crypt(req, xts_decrypt_done) ?:
              xts_xor_tweak_pre(req, false) ?:
              crypto_skcipher_decrypt(subreq) ?:
              xts_xor_tweak_post(req, false);

        if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
                return err;

        return xts_cts_final(req, crypto_skcipher_decrypt);
}

static int xts_init_tfm(struct crypto_skcipher *tfm)
{
        struct skcipher_instance *inst = skcipher_alg_instance(tfm);
        struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
        struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
        struct crypto_skcipher *child;
        struct crypto_cipher *tweak;

        child = crypto_spawn_skcipher(&ictx->spawn);
        if (IS_ERR(child))
                return PTR_ERR(child);

        ctx->child = child;

        tweak = crypto_spawn_cipher(&ictx->tweak_spawn);
        if (IS_ERR(tweak)) {
                crypto_free_skcipher(ctx->child);
                return PTR_ERR(tweak);
        }

        ctx->tweak = tweak;

        crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) +
                                         sizeof(struct xts_request_ctx));

        return 0;
}

static void xts_exit_tfm(struct crypto_skcipher *tfm)
{
        struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);

        crypto_free_skcipher(ctx->child);
        crypto_free_cipher(ctx->tweak);
}

static void xts_free_instance(struct skcipher_instance *inst)
{
        struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);

        crypto_drop_skcipher(&ictx->spawn);
        crypto_drop_cipher(&ictx->tweak_spawn);
        kfree(inst);
}

static int xts_create(struct crypto_template *tmpl, struct rtattr **tb)
{
        struct skcipher_alg_common *alg;
        char name[CRYPTO_MAX_ALG_NAME];
        struct skcipher_instance *inst;
        struct xts_instance_ctx *ctx;
        const char *cipher_name;
        u32 mask;
        int err;

        err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
        if (err)
                return err;

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

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

        ctx = skcipher_instance_ctx(inst);

        err = crypto_grab_skcipher(&ctx->spawn, skcipher_crypto_instance(inst),
                                   cipher_name, 0, mask);
        if (err == -ENOENT && memcmp(cipher_name, "ecb(", 4)) {
                err = -ENAMETOOLONG;
                if (snprintf(name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
                             cipher_name) >= CRYPTO_MAX_ALG_NAME)
                        goto err_free_inst;

                err = crypto_grab_skcipher(&ctx->spawn,
                                           skcipher_crypto_instance(inst),
                                           name, 0, mask);
        }

        if (err)
                goto err_free_inst;

        alg = crypto_spawn_skcipher_alg_common(&ctx->spawn);

        err = -EINVAL;
        if (alg->base.cra_blocksize != XTS_BLOCK_SIZE)
                goto err_free_inst;

        if (alg->ivsize)
                goto err_free_inst;

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

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

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

                len = strscpy(name, cipher_name + 4, sizeof(name));
                if (len < 2)
                        goto err_free_inst;

                if (name[len - 1] != ')')
                        goto err_free_inst;

                name[len - 1] = 0;

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

        err = crypto_grab_cipher(&ctx->tweak_spawn,
                                 skcipher_crypto_instance(inst), name, 0, mask);
        if (err)
                goto err_free_inst;

        inst->alg.base.cra_priority = alg->base.cra_priority;
        inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE;
        inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
                                       (__alignof__(u64) - 1);

        inst->alg.ivsize = XTS_BLOCK_SIZE;
        inst->alg.min_keysize = alg->min_keysize * 2;
        inst->alg.max_keysize = alg->max_keysize * 2;

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

        inst->alg.init = xts_init_tfm;
        inst->alg.exit = xts_exit_tfm;

        inst->alg.setkey = xts_setkey;
        inst->alg.encrypt = xts_encrypt;
        inst->alg.decrypt = xts_decrypt;

        inst->free = xts_free_instance;

        err = skcipher_register_instance(tmpl, inst);
        if (err) {
err_free_inst:
                xts_free_instance(inst);
        }
        return err;
}

static struct crypto_template xts_tmpl = {
        .name = "xts",
        .create = xts_create,
        .module = THIS_MODULE,
};

static int __init xts_module_init(void)
{
        return crypto_register_template(&xts_tmpl);
}

static void __exit xts_module_exit(void)
{
        crypto_unregister_template(&xts_tmpl);
}

module_init(xts_module_init);
module_exit(xts_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("XTS block cipher mode");
MODULE_ALIAS_CRYPTO("xts");
MODULE_IMPORT_NS("CRYPTO_INTERNAL");
MODULE_SOFTDEP("pre: ecb");