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