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// 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/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 priv {
struct crypto_skcipher *child;
struct crypto_cipher *tweak;
};
struct xts_instance_ctx {
struct crypto_skcipher_spawn spawn;
char name[CRYPTO_MAX_ALG_NAME];
};
struct rctx {
le128 t;
struct scatterlist *tail;
struct scatterlist sg[2];
struct skcipher_request subreq;
};
static int setkey(struct crypto_skcipher *parent, const u8 *key,
unsigned int keylen)
{
struct priv *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);
crypto_skcipher_set_flags(parent, crypto_cipher_get_flags(tweak) &
CRYPTO_TFM_RES_MASK);
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);
err = crypto_skcipher_setkey(child, key, keylen);
crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
CRYPTO_TFM_RES_MASK);
return err;
}
/*
* 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 xor_tweak(struct skcipher_request *req, bool second_pass, bool enc)
{
struct rctx *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;
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 xor_tweak_pre(struct skcipher_request *req, bool enc)
{
return xor_tweak(req, false, enc);
}
static int xor_tweak_post(struct skcipher_request *req, bool enc)
{
return xor_tweak(req, true, enc);
}
static void cts_done(struct crypto_async_request *areq, int err)
{
struct skcipher_request *req = areq->data;
le128 b;
if (!err) {
struct rctx *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 cts_final(struct skcipher_request *req,
int (*crypt)(struct skcipher_request *req))
{
struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
int offset = req->cryptlen & ~(XTS_BLOCK_SIZE - 1);
struct rctx *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);
memcpy(b + 1, b, tail);
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, 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 encrypt_done(struct crypto_async_request *areq, int err)
{
struct skcipher_request *req = areq->data;
if (!err) {
struct rctx *rctx = skcipher_request_ctx(req);
rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
err = xor_tweak_post(req, true);
if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
err = cts_final(req, crypto_skcipher_encrypt);
if (err == -EINPROGRESS)
return;
}
}
skcipher_request_complete(req, err);
}
static void decrypt_done(struct crypto_async_request *areq, int err)
{
struct skcipher_request *req = areq->data;
if (!err) {
struct rctx *rctx = skcipher_request_ctx(req);
rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
err = xor_tweak_post(req, false);
if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
err = cts_final(req, crypto_skcipher_decrypt);
if (err == -EINPROGRESS)
return;
}
}
skcipher_request_complete(req, err);
}
static int init_crypt(struct skcipher_request *req, crypto_completion_t compl)
{
struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
struct rctx *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 encrypt(struct skcipher_request *req)
{
struct rctx *rctx = skcipher_request_ctx(req);
struct skcipher_request *subreq = &rctx->subreq;
int err;
err = init_crypt(req, encrypt_done) ?:
xor_tweak_pre(req, true) ?:
crypto_skcipher_encrypt(subreq) ?:
xor_tweak_post(req, true);
if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
return err;
return cts_final(req, crypto_skcipher_encrypt);
}
static int decrypt(struct skcipher_request *req)
{
struct rctx *rctx = skcipher_request_ctx(req);
struct skcipher_request *subreq = &rctx->subreq;
int err;
err = init_crypt(req, decrypt_done) ?:
xor_tweak_pre(req, false) ?:
crypto_skcipher_decrypt(subreq) ?:
xor_tweak_post(req, false);
if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
return err;
return cts_final(req, crypto_skcipher_decrypt);
}
static int init_tfm(struct crypto_skcipher *tfm)
{
struct skcipher_instance *inst = skcipher_alg_instance(tfm);
struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
struct priv *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_alloc_cipher(ictx->name, 0, 0);
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 rctx));
return 0;
}
static void exit_tfm(struct crypto_skcipher *tfm)
{
struct priv *ctx = crypto_skcipher_ctx(tfm);
crypto_free_skcipher(ctx->child);
crypto_free_cipher(ctx->tweak);
}
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 skcipher_instance *inst;
struct crypto_attr_type *algt;
struct xts_instance_ctx *ctx;
struct skcipher_alg *alg;
const char *cipher_name;
u32 mask;
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(*ctx), GFP_KERNEL);
if (!inst)
return -ENOMEM;
ctx = skcipher_instance_ctx(inst);
crypto_set_skcipher_spawn(&ctx->spawn, skcipher_crypto_instance(inst));
mask = crypto_requires_off(algt->type, algt->mask,
CRYPTO_ALG_NEED_FALLBACK |
CRYPTO_ALG_ASYNC);
err = crypto_grab_skcipher(&ctx->spawn, cipher_name, 0, mask);
if (err == -ENOENT) {
err = -ENAMETOOLONG;
if (snprintf(ctx->name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
cipher_name) >= CRYPTO_MAX_ALG_NAME)
goto err_free_inst;
err = crypto_grab_skcipher(&ctx->spawn, ctx->name, 0, mask);
}
if (err)
goto err_free_inst;
alg = crypto_skcipher_spawn_alg(&ctx->spawn);
err = -EINVAL;
if (alg->base.cra_blocksize != XTS_BLOCK_SIZE)
goto err_drop_spawn;
if (crypto_skcipher_alg_ivsize(alg))
goto err_drop_spawn;
err = crypto_inst_setname(skcipher_crypto_instance(inst), "xts",
&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(ctx->name, cipher_name + 4, sizeof(ctx->name));
if (len < 2 || len >= sizeof(ctx->name))
goto err_drop_spawn;
if (ctx->name[len - 1] != ')')
goto err_drop_spawn;
ctx->name[len - 1] = 0;
if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
"xts(%s)", ctx->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 = 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 = crypto_skcipher_alg_min_keysize(alg) * 2;
inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2;
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(&ctx->spawn);
err_free_inst:
kfree(inst);
goto out;
}
static struct crypto_template crypto_tmpl = {
.name = "xts",
.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);
}
subsys_initcall(crypto_module_init);
module_exit(crypto_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("XTS block cipher mode");
MODULE_ALIAS_CRYPTO("xts");
|