// 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 <[email protected]>
*
* Based on ecb.c
* Copyright (c) 2006 Herbert Xu <[email protected]>
*/
/* 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/[email protected]/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 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 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(void *data, int err)
{
struct skcipher_request *req = 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_alg_common *alg;
struct skcipher_instance *inst;
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_spawn_skcipher_alg_common(spawn);
err = -EINVAL;
if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
goto err_free_inst;
if (alg->ivsize)
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)) {
int len;
len = strscpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
if (len < 2)
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 = alg->min_keysize + LRW_BLOCK_SIZE;
inst->alg.max_keysize = alg->max_keysize + 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");
MODULE_SOFTDEP("pre: ecb");
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