1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* LRW: as defined by Cyril Guyot in
3 * http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
4 *
5 * Copyright (c) 2006 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 /* This implementation is checked against the test vectors in the above
11 * document and by a test vector provided by Ken Buchanan at
12 * http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
13 *
14 * The test vectors are included in the testing module tcrypt.[ch] */
15
16 #include <crypto/internal/skcipher.h>
17 #include <crypto/scatterwalk.h>
18 #include <linux/err.h>
19 #include <linux/init.h>
20 #include <linux/kernel.h>
21 #include <linux/module.h>
22 #include <linux/scatterlist.h>
23 #include <linux/slab.h>
24
25 #include <crypto/b128ops.h>
26 #include <crypto/gf128mul.h>
27
28 #define LRW_BLOCK_SIZE 16
29
30 struct priv {
31 struct crypto_skcipher *child;
32
33 /*
34 * optimizes multiplying a random (non incrementing, as at the
35 * start of a new sector) value with key2, we could also have
36 * used 4k optimization tables or no optimization at all. In the
37 * latter case we would have to store key2 here
38 */
39 struct gf128mul_64k *table;
40
41 /*
42 * stores:
43 * key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
44 * key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
45 * key2*{ 0,0,...1,1,1,1,1 }, etc
46 * needed for optimized multiplication of incrementing values
47 * with key2
48 */
49 be128 mulinc[128];
50 };
51
52 struct rctx {
53 be128 t;
54 struct skcipher_request subreq;
55 };
56
setbit128_bbe(void * b,int bit)57 static inline void setbit128_bbe(void *b, int bit)
58 {
59 __set_bit(bit ^ (0x80 -
60 #ifdef __BIG_ENDIAN
61 BITS_PER_LONG
62 #else
63 BITS_PER_BYTE
64 #endif
65 ), b);
66 }
67
setkey(struct crypto_skcipher * parent,const u8 * key,unsigned int keylen)68 static int setkey(struct crypto_skcipher *parent, const u8 *key,
69 unsigned int keylen)
70 {
71 struct priv *ctx = crypto_skcipher_ctx(parent);
72 struct crypto_skcipher *child = ctx->child;
73 int err, bsize = LRW_BLOCK_SIZE;
74 const u8 *tweak = key + keylen - bsize;
75 be128 tmp = { 0 };
76 int i;
77
78 crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
79 crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
80 CRYPTO_TFM_REQ_MASK);
81 err = crypto_skcipher_setkey(child, key, keylen - bsize);
82 crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
83 CRYPTO_TFM_RES_MASK);
84 if (err)
85 return err;
86
87 if (ctx->table)
88 gf128mul_free_64k(ctx->table);
89
90 /* initialize multiplication table for Key2 */
91 ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
92 if (!ctx->table)
93 return -ENOMEM;
94
95 /* initialize optimization table */
96 for (i = 0; i < 128; i++) {
97 setbit128_bbe(&tmp, i);
98 ctx->mulinc[i] = tmp;
99 gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
100 }
101
102 return 0;
103 }
104
105 /*
106 * Returns the number of trailing '1' bits in the words of the counter, which is
107 * represented by 4 32-bit words, arranged from least to most significant.
108 * At the same time, increments the counter by one.
109 *
110 * For example:
111 *
112 * u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
113 * int i = next_index(&counter);
114 * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
115 */
next_index(u32 * counter)116 static int next_index(u32 *counter)
117 {
118 int i, res = 0;
119
120 for (i = 0; i < 4; i++) {
121 if (counter[i] + 1 != 0)
122 return res + ffz(counter[i]++);
123
124 counter[i] = 0;
125 res += 32;
126 }
127
128 /*
129 * If we get here, then x == 128 and we are incrementing the counter
130 * from all ones to all zeros. This means we must return index 127, i.e.
131 * the one corresponding to key2*{ 1,...,1 }.
132 */
133 return 127;
134 }
135
136 /*
137 * We compute the tweak masks twice (both before and after the ECB encryption or
138 * decryption) to avoid having to allocate a temporary buffer and/or make
139 * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
140 * just doing the next_index() calls again.
141 */
xor_tweak(struct skcipher_request * req,bool second_pass)142 static int xor_tweak(struct skcipher_request *req, bool second_pass)
143 {
144 const int bs = LRW_BLOCK_SIZE;
145 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
146 struct priv *ctx = crypto_skcipher_ctx(tfm);
147 struct rctx *rctx = skcipher_request_ctx(req);
148 be128 t = rctx->t;
149 struct skcipher_walk w;
150 __be32 *iv;
151 u32 counter[4];
152 int err;
153
154 if (second_pass) {
155 req = &rctx->subreq;
156 /* set to our TFM to enforce correct alignment: */
157 skcipher_request_set_tfm(req, tfm);
158 }
159
160 err = skcipher_walk_virt(&w, req, false);
161 if (err)
162 return err;
163
164 iv = (__be32 *)w.iv;
165 counter[0] = be32_to_cpu(iv[3]);
166 counter[1] = be32_to_cpu(iv[2]);
167 counter[2] = be32_to_cpu(iv[1]);
168 counter[3] = be32_to_cpu(iv[0]);
169
170 while (w.nbytes) {
171 unsigned int avail = w.nbytes;
172 be128 *wsrc;
173 be128 *wdst;
174
175 wsrc = w.src.virt.addr;
176 wdst = w.dst.virt.addr;
177
178 do {
179 be128_xor(wdst++, &t, wsrc++);
180
181 /* T <- I*Key2, using the optimization
182 * discussed in the specification */
183 be128_xor(&t, &t, &ctx->mulinc[next_index(counter)]);
184 } while ((avail -= bs) >= bs);
185
186 if (second_pass && w.nbytes == w.total) {
187 iv[0] = cpu_to_be32(counter[3]);
188 iv[1] = cpu_to_be32(counter[2]);
189 iv[2] = cpu_to_be32(counter[1]);
190 iv[3] = cpu_to_be32(counter[0]);
191 }
192
193 err = skcipher_walk_done(&w, avail);
194 }
195
196 return err;
197 }
198
xor_tweak_pre(struct skcipher_request * req)199 static int xor_tweak_pre(struct skcipher_request *req)
200 {
201 return xor_tweak(req, false);
202 }
203
xor_tweak_post(struct skcipher_request * req)204 static int xor_tweak_post(struct skcipher_request *req)
205 {
206 return xor_tweak(req, true);
207 }
208
crypt_done(struct crypto_async_request * areq,int err)209 static void crypt_done(struct crypto_async_request *areq, int err)
210 {
211 struct skcipher_request *req = areq->data;
212
213 if (!err) {
214 struct rctx *rctx = skcipher_request_ctx(req);
215
216 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
217 err = xor_tweak_post(req);
218 }
219
220 skcipher_request_complete(req, err);
221 }
222
init_crypt(struct skcipher_request * req)223 static void init_crypt(struct skcipher_request *req)
224 {
225 struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
226 struct rctx *rctx = skcipher_request_ctx(req);
227 struct skcipher_request *subreq = &rctx->subreq;
228
229 skcipher_request_set_tfm(subreq, ctx->child);
230 skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req);
231 /* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
232 skcipher_request_set_crypt(subreq, req->dst, req->dst,
233 req->cryptlen, req->iv);
234
235 /* calculate first value of T */
236 memcpy(&rctx->t, req->iv, sizeof(rctx->t));
237
238 /* T <- I*Key2 */
239 gf128mul_64k_bbe(&rctx->t, ctx->table);
240 }
241
encrypt(struct skcipher_request * req)242 static int encrypt(struct skcipher_request *req)
243 {
244 struct rctx *rctx = skcipher_request_ctx(req);
245 struct skcipher_request *subreq = &rctx->subreq;
246
247 init_crypt(req);
248 return xor_tweak_pre(req) ?:
249 crypto_skcipher_encrypt(subreq) ?:
250 xor_tweak_post(req);
251 }
252
decrypt(struct skcipher_request * req)253 static int decrypt(struct skcipher_request *req)
254 {
255 struct rctx *rctx = skcipher_request_ctx(req);
256 struct skcipher_request *subreq = &rctx->subreq;
257
258 init_crypt(req);
259 return xor_tweak_pre(req) ?:
260 crypto_skcipher_decrypt(subreq) ?:
261 xor_tweak_post(req);
262 }
263
init_tfm(struct crypto_skcipher * tfm)264 static int init_tfm(struct crypto_skcipher *tfm)
265 {
266 struct skcipher_instance *inst = skcipher_alg_instance(tfm);
267 struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
268 struct priv *ctx = crypto_skcipher_ctx(tfm);
269 struct crypto_skcipher *cipher;
270
271 cipher = crypto_spawn_skcipher(spawn);
272 if (IS_ERR(cipher))
273 return PTR_ERR(cipher);
274
275 ctx->child = cipher;
276
277 crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
278 sizeof(struct rctx));
279
280 return 0;
281 }
282
exit_tfm(struct crypto_skcipher * tfm)283 static void exit_tfm(struct crypto_skcipher *tfm)
284 {
285 struct priv *ctx = crypto_skcipher_ctx(tfm);
286
287 if (ctx->table)
288 gf128mul_free_64k(ctx->table);
289 crypto_free_skcipher(ctx->child);
290 }
291
free(struct skcipher_instance * inst)292 static void free(struct skcipher_instance *inst)
293 {
294 crypto_drop_skcipher(skcipher_instance_ctx(inst));
295 kfree(inst);
296 }
297
create(struct crypto_template * tmpl,struct rtattr ** tb)298 static int create(struct crypto_template *tmpl, struct rtattr **tb)
299 {
300 struct crypto_skcipher_spawn *spawn;
301 struct skcipher_instance *inst;
302 struct crypto_attr_type *algt;
303 struct skcipher_alg *alg;
304 const char *cipher_name;
305 char ecb_name[CRYPTO_MAX_ALG_NAME];
306 int err;
307
308 algt = crypto_get_attr_type(tb);
309 if (IS_ERR(algt))
310 return PTR_ERR(algt);
311
312 if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
313 return -EINVAL;
314
315 cipher_name = crypto_attr_alg_name(tb[1]);
316 if (IS_ERR(cipher_name))
317 return PTR_ERR(cipher_name);
318
319 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
320 if (!inst)
321 return -ENOMEM;
322
323 spawn = skcipher_instance_ctx(inst);
324
325 crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
326 err = crypto_grab_skcipher(spawn, cipher_name, 0,
327 crypto_requires_sync(algt->type,
328 algt->mask));
329 if (err == -ENOENT) {
330 err = -ENAMETOOLONG;
331 if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
332 cipher_name) >= CRYPTO_MAX_ALG_NAME)
333 goto err_free_inst;
334
335 err = crypto_grab_skcipher(spawn, ecb_name, 0,
336 crypto_requires_sync(algt->type,
337 algt->mask));
338 }
339
340 if (err)
341 goto err_free_inst;
342
343 alg = crypto_skcipher_spawn_alg(spawn);
344
345 err = -EINVAL;
346 if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
347 goto err_drop_spawn;
348
349 if (crypto_skcipher_alg_ivsize(alg))
350 goto err_drop_spawn;
351
352 err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
353 &alg->base);
354 if (err)
355 goto err_drop_spawn;
356
357 err = -EINVAL;
358 cipher_name = alg->base.cra_name;
359
360 /* Alas we screwed up the naming so we have to mangle the
361 * cipher name.
362 */
363 if (!strncmp(cipher_name, "ecb(", 4)) {
364 unsigned len;
365
366 len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
367 if (len < 2 || len >= sizeof(ecb_name))
368 goto err_drop_spawn;
369
370 if (ecb_name[len - 1] != ')')
371 goto err_drop_spawn;
372
373 ecb_name[len - 1] = 0;
374
375 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
376 "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
377 err = -ENAMETOOLONG;
378 goto err_drop_spawn;
379 }
380 } else
381 goto err_drop_spawn;
382
383 inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
384 inst->alg.base.cra_priority = alg->base.cra_priority;
385 inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
386 inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
387 (__alignof__(be128) - 1);
388
389 inst->alg.ivsize = LRW_BLOCK_SIZE;
390 inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
391 LRW_BLOCK_SIZE;
392 inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
393 LRW_BLOCK_SIZE;
394
395 inst->alg.base.cra_ctxsize = sizeof(struct priv);
396
397 inst->alg.init = init_tfm;
398 inst->alg.exit = exit_tfm;
399
400 inst->alg.setkey = setkey;
401 inst->alg.encrypt = encrypt;
402 inst->alg.decrypt = decrypt;
403
404 inst->free = free;
405
406 err = skcipher_register_instance(tmpl, inst);
407 if (err)
408 goto err_drop_spawn;
409
410 out:
411 return err;
412
413 err_drop_spawn:
414 crypto_drop_skcipher(spawn);
415 err_free_inst:
416 kfree(inst);
417 goto out;
418 }
419
420 static struct crypto_template crypto_tmpl = {
421 .name = "lrw",
422 .create = create,
423 .module = THIS_MODULE,
424 };
425
crypto_module_init(void)426 static int __init crypto_module_init(void)
427 {
428 return crypto_register_template(&crypto_tmpl);
429 }
430
crypto_module_exit(void)431 static void __exit crypto_module_exit(void)
432 {
433 crypto_unregister_template(&crypto_tmpl);
434 }
435
436 subsys_initcall(crypto_module_init);
437 module_exit(crypto_module_exit);
438
439 MODULE_LICENSE("GPL");
440 MODULE_DESCRIPTION("LRW block cipher mode");
441 MODULE_ALIAS_CRYPTO("lrw");
442