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/* XTS: as defined in IEEE1619/D16
* http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
* (sector sizes which are not a multiple of 16 bytes are,
* however currently unsupported)
*
* Copyright (c) 2007 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.
*/
#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>
#define XTS_BUFFER_SIZE 128u
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 buf[XTS_BUFFER_SIZE / sizeof(le128)];
le128 t;
le128 *ext;
struct scatterlist srcbuf[2];
struct scatterlist dstbuf[2];
struct scatterlist *src;
struct scatterlist *dst;
unsigned int left;
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;
}
static int post_crypt(struct skcipher_request *req)
{
struct rctx *rctx = skcipher_request_ctx(req);
le128 *buf = rctx->ext ?: rctx->buf;
struct skcipher_request *subreq;
const int bs = XTS_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;
le128 *wdst;
wdst = w.dst.virt.addr;
do {
le128_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 rctx *rctx = skcipher_request_ctx(req);
le128 *buf = rctx->ext ?: rctx->buf;
struct skcipher_request *subreq;
const int bs = XTS_BLOCK_SIZE;
struct skcipher_walk w;
struct scatterlist *sg;
unsigned cryptlen;
unsigned offset;
bool more;
int err;
subreq = &rctx->subreq;
cryptlen = subreq->cryptlen;
more = rctx->left > cryptlen;
if (!more)
cryptlen = rctx->left;
skcipher_request_set_crypt(subreq, rctx->src, rctx->dst,
cryptlen, NULL);
err = skcipher_walk_virt(&w, subreq, false);
while (w.nbytes) {
unsigned int avail = w.nbytes;
le128 *wsrc;
le128 *wdst;
wsrc = w.src.virt.addr;
wdst = w.dst.virt.addr;
do {
*buf++ = rctx->t;
le128_xor(wdst++, &rctx->t, wsrc++);
gf128mul_x_ble(&rctx->t, &rctx->t);
} while ((avail -= bs) >= bs);
err = skcipher_walk_done(&w, avail);
}
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_tfm(subreq, ctx->child);
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 = XTS_BUFFER_SIZE;
if (req->cryptlen > XTS_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 */
crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv);
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 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);
}
module_init(crypto_module_init);
module_exit(crypto_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("XTS block cipher mode");
MODULE_ALIAS_CRYPTO("xts");