1// SPDX-License-Identifier: GPL-2.0-or-later
2/* XTS: as defined in IEEE1619/D16
3 * http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
4 *
5 * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
6 *
7 * Based on ecb.c
8 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
9 */
10#include <crypto/internal/cipher.h>
11#include <crypto/internal/skcipher.h>
12#include <crypto/scatterwalk.h>
13#include <linux/err.h>
14#include <linux/init.h>
15#include <linux/kernel.h>
16#include <linux/module.h>
17#include <linux/scatterlist.h>
18#include <linux/slab.h>
19
20#include <crypto/xts.h>
21#include <crypto/b128ops.h>
22#include <crypto/gf128mul.h>
23
24struct xts_tfm_ctx {
25 struct crypto_skcipher *child;
26 struct crypto_cipher *tweak;
27};
28
29struct xts_instance_ctx {
30 struct crypto_skcipher_spawn spawn;
31 struct crypto_cipher_spawn tweak_spawn;
32};
33
34struct xts_request_ctx {
35 le128 t;
36 struct scatterlist *tail;
37 struct scatterlist sg[2];
38 struct skcipher_request subreq;
39};
40
41static int xts_setkey(struct crypto_skcipher *parent, const u8 *key,
42 unsigned int keylen)
43{
44 struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm: parent);
45 struct crypto_skcipher *child;
46 struct crypto_cipher *tweak;
47 int err;
48
49 err = xts_verify_key(tfm: parent, key, keylen);
50 if (err)
51 return err;
52
53 keylen /= 2;
54
55 /* we need two cipher instances: one to compute the initial 'tweak'
56 * by encrypting the IV (usually the 'plain' iv) and the other
57 * one to encrypt and decrypt the data */
58
59 /* tweak cipher, uses Key2 i.e. the second half of *key */
60 tweak = ctx->tweak;
61 crypto_cipher_clear_flags(tfm: tweak, CRYPTO_TFM_REQ_MASK);
62 crypto_cipher_set_flags(tfm: tweak, flags: crypto_skcipher_get_flags(tfm: parent) &
63 CRYPTO_TFM_REQ_MASK);
64 err = crypto_cipher_setkey(tfm: tweak, key: key + keylen, keylen);
65 if (err)
66 return err;
67
68 /* data cipher, uses Key1 i.e. the first half of *key */
69 child = ctx->child;
70 crypto_skcipher_clear_flags(tfm: child, CRYPTO_TFM_REQ_MASK);
71 crypto_skcipher_set_flags(tfm: child, flags: crypto_skcipher_get_flags(tfm: parent) &
72 CRYPTO_TFM_REQ_MASK);
73 return crypto_skcipher_setkey(tfm: child, key, keylen);
74}
75
76/*
77 * We compute the tweak masks twice (both before and after the ECB encryption or
78 * decryption) to avoid having to allocate a temporary buffer and/or make
79 * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
80 * just doing the gf128mul_x_ble() calls again.
81 */
82static int xts_xor_tweak(struct skcipher_request *req, bool second_pass,
83 bool enc)
84{
85 struct xts_request_ctx *rctx = skcipher_request_ctx(req);
86 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
87 const bool cts = (req->cryptlen % XTS_BLOCK_SIZE);
88 const int bs = XTS_BLOCK_SIZE;
89 struct skcipher_walk w;
90 le128 t = rctx->t;
91 int err;
92
93 if (second_pass) {
94 req = &rctx->subreq;
95 /* set to our TFM to enforce correct alignment: */
96 skcipher_request_set_tfm(req, tfm);
97 }
98 err = skcipher_walk_virt(walk: &w, req, atomic: false);
99
100 while (w.nbytes) {
101 unsigned int avail = w.nbytes;
102 const le128 *wsrc;
103 le128 *wdst;
104
105 wsrc = w.src.virt.addr;
106 wdst = w.dst.virt.addr;
107
108 do {
109 if (unlikely(cts) &&
110 w.total - w.nbytes + avail < 2 * XTS_BLOCK_SIZE) {
111 if (!enc) {
112 if (second_pass)
113 rctx->t = t;
114 gf128mul_x_ble(r: &t, x: &t);
115 }
116 le128_xor(r: wdst, p: &t, q: wsrc);
117 if (enc && second_pass)
118 gf128mul_x_ble(r: &rctx->t, x: &t);
119 skcipher_walk_done(walk: &w, res: avail - bs);
120 return 0;
121 }
122
123 le128_xor(r: wdst++, p: &t, q: wsrc++);
124 gf128mul_x_ble(r: &t, x: &t);
125 } while ((avail -= bs) >= bs);
126
127 err = skcipher_walk_done(walk: &w, res: avail);
128 }
129
130 return err;
131}
132
133static int xts_xor_tweak_pre(struct skcipher_request *req, bool enc)
134{
135 return xts_xor_tweak(req, second_pass: false, enc);
136}
137
138static int xts_xor_tweak_post(struct skcipher_request *req, bool enc)
139{
140 return xts_xor_tweak(req, second_pass: true, enc);
141}
142
143static void xts_cts_done(void *data, int err)
144{
145 struct skcipher_request *req = data;
146 le128 b;
147
148 if (!err) {
149 struct xts_request_ctx *rctx = skcipher_request_ctx(req);
150
151 scatterwalk_map_and_copy(buf: &b, sg: rctx->tail, start: 0, XTS_BLOCK_SIZE, out: 0);
152 le128_xor(r: &b, p: &rctx->t, q: &b);
153 scatterwalk_map_and_copy(buf: &b, sg: rctx->tail, start: 0, XTS_BLOCK_SIZE, out: 1);
154 }
155
156 skcipher_request_complete(req, err);
157}
158
159static int xts_cts_final(struct skcipher_request *req,
160 int (*crypt)(struct skcipher_request *req))
161{
162 const struct xts_tfm_ctx *ctx =
163 crypto_skcipher_ctx(tfm: crypto_skcipher_reqtfm(req));
164 int offset = req->cryptlen & ~(XTS_BLOCK_SIZE - 1);
165 struct xts_request_ctx *rctx = skcipher_request_ctx(req);
166 struct skcipher_request *subreq = &rctx->subreq;
167 int tail = req->cryptlen % XTS_BLOCK_SIZE;
168 le128 b[2];
169 int err;
170
171 rctx->tail = scatterwalk_ffwd(dst: rctx->sg, src: req->dst,
172 len: offset - XTS_BLOCK_SIZE);
173
174 scatterwalk_map_and_copy(buf: b, sg: rctx->tail, start: 0, XTS_BLOCK_SIZE, out: 0);
175 b[1] = b[0];
176 scatterwalk_map_and_copy(buf: b, sg: req->src, start: offset, nbytes: tail, out: 0);
177
178 le128_xor(r: b, p: &rctx->t, q: b);
179
180 scatterwalk_map_and_copy(buf: b, sg: rctx->tail, start: 0, XTS_BLOCK_SIZE + tail, out: 1);
181
182 skcipher_request_set_tfm(req: subreq, tfm: ctx->child);
183 skcipher_request_set_callback(req: subreq, flags: req->base.flags, compl: xts_cts_done,
184 data: req);
185 skcipher_request_set_crypt(req: subreq, src: rctx->tail, dst: rctx->tail,
186 XTS_BLOCK_SIZE, NULL);
187
188 err = crypt(subreq);
189 if (err)
190 return err;
191
192 scatterwalk_map_and_copy(buf: b, sg: rctx->tail, start: 0, XTS_BLOCK_SIZE, out: 0);
193 le128_xor(r: b, p: &rctx->t, q: b);
194 scatterwalk_map_and_copy(buf: b, sg: rctx->tail, start: 0, XTS_BLOCK_SIZE, out: 1);
195
196 return 0;
197}
198
199static void xts_encrypt_done(void *data, int err)
200{
201 struct skcipher_request *req = data;
202
203 if (!err) {
204 struct xts_request_ctx *rctx = skcipher_request_ctx(req);
205
206 rctx->subreq.base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;
207 err = xts_xor_tweak_post(req, enc: true);
208
209 if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
210 err = xts_cts_final(req, crypt: crypto_skcipher_encrypt);
211 if (err == -EINPROGRESS || err == -EBUSY)
212 return;
213 }
214 }
215
216 skcipher_request_complete(req, err);
217}
218
219static void xts_decrypt_done(void *data, int err)
220{
221 struct skcipher_request *req = data;
222
223 if (!err) {
224 struct xts_request_ctx *rctx = skcipher_request_ctx(req);
225
226 rctx->subreq.base.flags &= CRYPTO_TFM_REQ_MAY_BACKLOG;
227 err = xts_xor_tweak_post(req, enc: false);
228
229 if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) {
230 err = xts_cts_final(req, crypt: crypto_skcipher_decrypt);
231 if (err == -EINPROGRESS || err == -EBUSY)
232 return;
233 }
234 }
235
236 skcipher_request_complete(req, err);
237}
238
239static int xts_init_crypt(struct skcipher_request *req,
240 crypto_completion_t compl)
241{
242 const struct xts_tfm_ctx *ctx =
243 crypto_skcipher_ctx(tfm: crypto_skcipher_reqtfm(req));
244 struct xts_request_ctx *rctx = skcipher_request_ctx(req);
245 struct skcipher_request *subreq = &rctx->subreq;
246
247 if (req->cryptlen < XTS_BLOCK_SIZE)
248 return -EINVAL;
249
250 skcipher_request_set_tfm(req: subreq, tfm: ctx->child);
251 skcipher_request_set_callback(req: subreq, flags: req->base.flags, compl, data: req);
252 skcipher_request_set_crypt(req: subreq, src: req->dst, dst: req->dst,
253 cryptlen: req->cryptlen & ~(XTS_BLOCK_SIZE - 1), NULL);
254
255 /* calculate first value of T */
256 crypto_cipher_encrypt_one(tfm: ctx->tweak, dst: (u8 *)&rctx->t, src: req->iv);
257
258 return 0;
259}
260
261static int xts_encrypt(struct skcipher_request *req)
262{
263 struct xts_request_ctx *rctx = skcipher_request_ctx(req);
264 struct skcipher_request *subreq = &rctx->subreq;
265 int err;
266
267 err = xts_init_crypt(req, compl: xts_encrypt_done) ?:
268 xts_xor_tweak_pre(req, enc: true) ?:
269 crypto_skcipher_encrypt(req: subreq) ?:
270 xts_xor_tweak_post(req, enc: true);
271
272 if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
273 return err;
274
275 return xts_cts_final(req, crypt: crypto_skcipher_encrypt);
276}
277
278static int xts_decrypt(struct skcipher_request *req)
279{
280 struct xts_request_ctx *rctx = skcipher_request_ctx(req);
281 struct skcipher_request *subreq = &rctx->subreq;
282 int err;
283
284 err = xts_init_crypt(req, compl: xts_decrypt_done) ?:
285 xts_xor_tweak_pre(req, enc: false) ?:
286 crypto_skcipher_decrypt(req: subreq) ?:
287 xts_xor_tweak_post(req, enc: false);
288
289 if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0))
290 return err;
291
292 return xts_cts_final(req, crypt: crypto_skcipher_decrypt);
293}
294
295static int xts_init_tfm(struct crypto_skcipher *tfm)
296{
297 struct skcipher_instance *inst = skcipher_alg_instance(skcipher: tfm);
298 struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
299 struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
300 struct crypto_skcipher *child;
301 struct crypto_cipher *tweak;
302
303 child = crypto_spawn_skcipher(spawn: &ictx->spawn);
304 if (IS_ERR(ptr: child))
305 return PTR_ERR(ptr: child);
306
307 ctx->child = child;
308
309 tweak = crypto_spawn_cipher(spawn: &ictx->tweak_spawn);
310 if (IS_ERR(ptr: tweak)) {
311 crypto_free_skcipher(tfm: ctx->child);
312 return PTR_ERR(ptr: tweak);
313 }
314
315 ctx->tweak = tweak;
316
317 crypto_skcipher_set_reqsize(skcipher: tfm, reqsize: crypto_skcipher_reqsize(tfm: child) +
318 sizeof(struct xts_request_ctx));
319
320 return 0;
321}
322
323static void xts_exit_tfm(struct crypto_skcipher *tfm)
324{
325 struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
326
327 crypto_free_skcipher(tfm: ctx->child);
328 crypto_free_cipher(tfm: ctx->tweak);
329}
330
331static void xts_free_instance(struct skcipher_instance *inst)
332{
333 struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst);
334
335 crypto_drop_skcipher(spawn: &ictx->spawn);
336 crypto_drop_cipher(spawn: &ictx->tweak_spawn);
337 kfree(objp: inst);
338}
339
340static int xts_create(struct crypto_template *tmpl, struct rtattr **tb)
341{
342 struct skcipher_alg_common *alg;
343 char name[CRYPTO_MAX_ALG_NAME];
344 struct skcipher_instance *inst;
345 struct xts_instance_ctx *ctx;
346 const char *cipher_name;
347 u32 mask;
348 int err;
349
350 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, mask_ret: &mask);
351 if (err)
352 return err;
353
354 cipher_name = crypto_attr_alg_name(rta: tb[1]);
355 if (IS_ERR(ptr: cipher_name))
356 return PTR_ERR(ptr: cipher_name);
357
358 inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
359 if (!inst)
360 return -ENOMEM;
361
362 ctx = skcipher_instance_ctx(inst);
363
364 err = crypto_grab_skcipher(spawn: &ctx->spawn, inst: skcipher_crypto_instance(inst),
365 name: cipher_name, type: 0, mask);
366 if (err == -ENOENT && memcmp(p: cipher_name, q: "ecb(", size: 4)) {
367 err = -ENAMETOOLONG;
368 if (snprintf(buf: name, CRYPTO_MAX_ALG_NAME, fmt: "ecb(%s)",
369 cipher_name) >= CRYPTO_MAX_ALG_NAME)
370 goto err_free_inst;
371
372 err = crypto_grab_skcipher(spawn: &ctx->spawn,
373 inst: skcipher_crypto_instance(inst),
374 name, type: 0, mask);
375 }
376
377 if (err)
378 goto err_free_inst;
379
380 alg = crypto_spawn_skcipher_alg_common(spawn: &ctx->spawn);
381
382 err = -EINVAL;
383 if (alg->base.cra_blocksize != XTS_BLOCK_SIZE)
384 goto err_free_inst;
385
386 if (alg->ivsize)
387 goto err_free_inst;
388
389 err = crypto_inst_setname(skcipher_crypto_instance(inst), "xts",
390 &alg->base);
391 if (err)
392 goto err_free_inst;
393
394 err = -EINVAL;
395 cipher_name = alg->base.cra_name;
396
397 /* Alas we screwed up the naming so we have to mangle the
398 * cipher name.
399 */
400 if (!memcmp(p: cipher_name, q: "ecb(", size: 4)) {
401 int len;
402
403 len = strscpy(name, cipher_name + 4, sizeof(name));
404 if (len < 2)
405 goto err_free_inst;
406
407 if (name[len - 1] != ')')
408 goto err_free_inst;
409
410 name[len - 1] = 0;
411
412 if (snprintf(buf: inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
413 fmt: "xts(%s)", name) >= CRYPTO_MAX_ALG_NAME) {
414 err = -ENAMETOOLONG;
415 goto err_free_inst;
416 }
417 } else
418 goto err_free_inst;
419
420 err = crypto_grab_cipher(spawn: &ctx->tweak_spawn,
421 inst: skcipher_crypto_instance(inst), name, type: 0, mask);
422 if (err)
423 goto err_free_inst;
424
425 inst->alg.base.cra_priority = alg->base.cra_priority;
426 inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE;
427 inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
428 (__alignof__(u64) - 1);
429
430 inst->alg.ivsize = XTS_BLOCK_SIZE;
431 inst->alg.min_keysize = alg->min_keysize * 2;
432 inst->alg.max_keysize = alg->max_keysize * 2;
433
434 inst->alg.base.cra_ctxsize = sizeof(struct xts_tfm_ctx);
435
436 inst->alg.init = xts_init_tfm;
437 inst->alg.exit = xts_exit_tfm;
438
439 inst->alg.setkey = xts_setkey;
440 inst->alg.encrypt = xts_encrypt;
441 inst->alg.decrypt = xts_decrypt;
442
443 inst->free = xts_free_instance;
444
445 err = skcipher_register_instance(tmpl, inst);
446 if (err) {
447err_free_inst:
448 xts_free_instance(inst);
449 }
450 return err;
451}
452
453static struct crypto_template xts_tmpl = {
454 .name = "xts",
455 .create = xts_create,
456 .module = THIS_MODULE,
457};
458
459static int __init xts_module_init(void)
460{
461 return crypto_register_template(tmpl: &xts_tmpl);
462}
463
464static void __exit xts_module_exit(void)
465{
466 crypto_unregister_template(tmpl: &xts_tmpl);
467}
468
469module_init(xts_module_init);
470module_exit(xts_module_exit);
471
472MODULE_LICENSE("GPL");
473MODULE_DESCRIPTION("XTS block cipher mode");
474MODULE_ALIAS_CRYPTO("xts");
475MODULE_IMPORT_NS("CRYPTO_INTERNAL");
476MODULE_SOFTDEP("pre: ecb");
477

source code of linux/crypto/xts.c