// SPDX-License-Identifier: GPL-2.0-or-later

/* 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 implementation is checked against the test vectors in the above

* document and by a test vector provided by Ken Buchanan at

* https://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_BLOCK_SIZE 16

struct lrw_tfm_ctx {

};

struct lrw_request_ctx {

be128 t;

struct skcipher_request subreq;

};

static inline void lrw_setbit128_bbe(void *b, int bit)

{

__set_bit(bit ^ (0x80 -

#ifdef __BIG_ENDIAN

BITS_PER_LONG

#else

BITS_PER_BYTE

#endif

), b);

}

static int lrw_setkey(struct crypto_skcipher *parent, const u8 *key,

unsigned int keylen)

{

struct lrw_tfm_ctx *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);

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++) {

lrw_setbit128_bbe(&tmp, i);

ctx->mulinc[i] = tmp;

gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);

}

return 0;

}

/*

* Returns the number of trailing '1' bits in the words of the counter, which is

* represented by 4 32-bit words, arranged from least to most significant.

* At the same time, increments the counter by one.

*

* For example:

*

* u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };

* int i = lrw_next_index(&counter);

* // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }

*/

static int lrw_next_index(u32 *counter)

{

int i, res = 0;

for (i = 0; i < 4; i++) {

if (counter[i] + 1 != 0)

return res + ffz(counter[i]++);

counter[i] = 0;

res += 32;

}

/*

* If we get here, then x == 128 and we are incrementing the counter

* from all ones to all zeros. This means we must return index 127, i.e.

* the one corresponding to key2*{ 1,...,1 }.

*/

return 127;

}

/*

* 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 lrw_next_index() calls again.

*/

static int lrw_xor_tweak(struct skcipher_request *req, bool second_pass)

{

const int bs = LRW_BLOCK_SIZE;

struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);

const struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);

struct lrw_request_ctx *rctx = skcipher_request_ctx(req);

be128 t = rctx->t;

struct skcipher_walk w;

__be32 *iv;

u32 counter[4];

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);

if (err)

return err;

iv = (__be32 *)w.iv;

counter[0] = be32_to_cpu(iv[3]);

counter[1] = be32_to_cpu(iv[2]);

counter[2] = be32_to_cpu(iv[1]);

counter[3] = be32_to_cpu(iv[0]);

while (w.nbytes) {

unsigned int avail = w.nbytes;

be128 *wsrc;

be128 *wdst;

wsrc = w.src.virt.addr;

wdst = w.dst.virt.addr;

do {

be128_xor(wdst++, &t, wsrc++);

/* T <- I*Key2, using the optimization

* discussed in the specification */

be128_xor(&t, &t,

&ctx->mulinc[lrw_next_index(counter)]);

} while ((avail -= bs) >= bs);

if (second_pass && w.nbytes == w.total) {

iv[0] = cpu_to_be32(counter[3]);

iv[1] = cpu_to_be32(counter[2]);

iv[2] = cpu_to_be32(counter[1]);

iv[3] = cpu_to_be32(counter[0]);

}

err = skcipher_walk_done(&w, avail);

}

return err;

}

static int lrw_xor_tweak_pre(struct skcipher_request *req)

{

return lrw_xor_tweak(req, false);

}

static int lrw_xor_tweak_post(struct skcipher_request *req)

{

return lrw_xor_tweak(req, true);

}

static void lrw_crypt_done(struct crypto_async_request *areq, int err)

{

struct skcipher_request *req = areq->data;

if (!err) {

struct lrw_request_ctx *rctx = skcipher_request_ctx(req);

rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;

err = lrw_xor_tweak_post(req);

}

skcipher_request_complete(req, err);

}

static void lrw_init_crypt(struct skcipher_request *req)

{

const struct lrw_tfm_ctx *ctx =

crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));

struct lrw_request_ctx *rctx = skcipher_request_ctx(req);

struct skcipher_request *subreq = &rctx->subreq;

skcipher_request_set_tfm(subreq, ctx->child);

skcipher_request_set_callback(subreq, req->base.flags, lrw_crypt_done,

req);

/* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */

skcipher_request_set_crypt(subreq, req->dst, req->dst,

req->cryptlen, req->iv);

/* calculate first value of T */

memcpy(&rctx->t, req->iv, sizeof(rctx->t));

/* T <- I*Key2 */

gf128mul_64k_bbe(&rctx->t, ctx->table);

}

static int lrw_encrypt(struct skcipher_request *req)

{

struct lrw_request_ctx *rctx = skcipher_request_ctx(req);

struct skcipher_request *subreq = &rctx->subreq;

lrw_init_crypt(req);

return lrw_xor_tweak_pre(req) ?:

crypto_skcipher_encrypt(subreq) ?:

lrw_xor_tweak_post(req);

}

static int lrw_decrypt(struct skcipher_request *req)

{

struct lrw_request_ctx *rctx = skcipher_request_ctx(req);

struct skcipher_request *subreq = &rctx->subreq;

lrw_init_crypt(req);

return lrw_xor_tweak_pre(req) ?:

crypto_skcipher_decrypt(subreq) ?:

lrw_xor_tweak_post(req);

}

static int lrw_init_tfm(struct crypto_skcipher *tfm)

{

struct skcipher_instance *inst = skcipher_alg_instance(tfm);

struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);

struct lrw_tfm_ctx *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 lrw_request_ctx));

return 0;

}

static void lrw_exit_tfm(struct crypto_skcipher *tfm)

{

struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);

if (ctx->table)

gf128mul_free_64k(ctx->table);

crypto_free_skcipher(ctx->child);

}

static void lrw_free_instance(struct skcipher_instance *inst)

{

crypto_drop_skcipher(skcipher_instance_ctx(inst));

kfree(inst);

}

static int lrw_create(struct crypto_template *tmpl, struct rtattr **tb)

{

struct crypto_skcipher_spawn *spawn;

struct skcipher_instance *inst;

struct skcipher_alg *alg;

const char *cipher_name;

char ecb_name[CRYPTO_MAX_ALG_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(*spawn), GFP_KERNEL);

if (!inst)

return -ENOMEM;

spawn = skcipher_instance_ctx(inst);

err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),

cipher_name, 0, 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,

skcipher_crypto_instance(inst),

ecb_name, 0, 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_free_inst;

if (crypto_skcipher_alg_ivsize(alg))

goto err_free_inst;

err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",

&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 (!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_free_inst;

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

goto err_free_inst;

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_free_inst;

}

} else

goto err_free_inst;

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__(be128) - 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 lrw_tfm_ctx);

inst->alg.init = lrw_init_tfm;

inst->alg.exit = lrw_exit_tfm;

inst->alg.setkey = lrw_setkey;

inst->alg.encrypt = lrw_encrypt;

inst->alg.decrypt = lrw_decrypt;

inst->free = lrw_free_instance;

err = skcipher_register_instance(tmpl, inst);

if (err) {

err_free_inst:

lrw_free_instance(inst);

}

return err;

}

static struct crypto_template lrw_tmpl = {

.name = "lrw",

.create = lrw_create,

.module = THIS_MODULE,

};

static int __init lrw_module_init(void)

{

return crypto_register_template(&lrw_tmpl);

}

static void __exit lrw_module_exit(void)

{

crypto_unregister_template(&lrw_tmpl);

}

subsys_initcall(lrw_module_init);

module_exit(lrw_module_exit);

MODULE_LICENSE("GPL");

MODULE_DESCRIPTION("LRW block cipher mode");

MODULE_ALIAS_CRYPTO("lrw");