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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
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
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 if (err)
83 return err;
84
85 if (ctx->table)
86 gf128mul_free_64k(ctx->table);
87
88 /* initialize multiplication table for Key2 */
89 ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
90 if (!ctx->table)
91 return -ENOMEM;
92
93 /* initialize optimization table */
94 for (i = 0; i < 128; i++) {
95 setbit128_bbe(&tmp, i);
96 ctx->mulinc[i] = tmp;
97 gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
98 }
99
100 return 0;
101 }
102
103 /*
104 * Returns the number of trailing '1' bits in the words of the counter, which is
105 * represented by 4 32-bit words, arranged from least to most significant.
106 * At the same time, increments the counter by one.
107 *
108 * For example:
109 *
110 * u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
111 * int i = next_index(&counter);
112 * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
113 */
114 static int next_index(u32 *counter)
115 {
116 int i, res = 0;
117
118 for (i = 0; i < 4; i++) {
119 if (counter[i] + 1 != 0)
120 return res + ffz(counter[i]++);
121
122 counter[i] = 0;
123 res += 32;
124 }
125
126 /*
127 * If we get here, then x == 128 and we are incrementing the counter
128 * from all ones to all zeros. This means we must return index 127, i.e.
129 * the one corresponding to key2*{ 1,...,1 }.
130 */
131 return 127;
132 }
133
134 /*
135 * We compute the tweak masks twice (both before and after the ECB encryption or
136 * decryption) to avoid having to allocate a temporary buffer and/or make
137 * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
138 * just doing the next_index() calls again.
139 */
140 static int xor_tweak(struct skcipher_request *req, bool second_pass)
141 {
142 const int bs = LRW_BLOCK_SIZE;
143 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
144 struct priv *ctx = crypto_skcipher_ctx(tfm);
145 struct rctx *rctx = skcipher_request_ctx(req);
146 be128 t = rctx->t;
147 struct skcipher_walk w;
148 __be32 *iv;
149 u32 counter[4];
150 int err;
151
152 if (second_pass) {
153 req = &rctx->subreq;
154 /* set to our TFM to enforce correct alignment: */
155 skcipher_request_set_tfm(req, tfm);
156 }
157
158 err = skcipher_walk_virt(&w, req, false);
159 if (err)
160 return err;
161
162 iv = (__be32 *)w.iv;
163 counter[0] = be32_to_cpu(iv[3]);
164 counter[1] = be32_to_cpu(iv[2]);
165 counter[2] = be32_to_cpu(iv[1]);
166 counter[3] = be32_to_cpu(iv[0]);
167
168 while (w.nbytes) {
169 unsigned int avail = w.nbytes;
170 be128 *wsrc;
171 be128 *wdst;
172
173 wsrc = w.src.virt.addr;
174 wdst = w.dst.virt.addr;
175
176 do {
177 be128_xor(wdst++, &t, wsrc++);
178
179 /* T <- I*Key2, using the optimization
180 * discussed in the specification */
181 be128_xor(&t, &t, &ctx->mulinc[next_index(counter)]);
182 } while ((avail -= bs) >= bs);
183
184 if (second_pass && w.nbytes == w.total) {
185 iv[0] = cpu_to_be32(counter[3]);
186 iv[1] = cpu_to_be32(counter[2]);
187 iv[2] = cpu_to_be32(counter[1]);
188 iv[3] = cpu_to_be32(counter[0]);
189 }
190
191 err = skcipher_walk_done(&w, avail);
192 }
193
194 return err;
195 }
196
197 static int xor_tweak_pre(struct skcipher_request *req)
198 {
199 return xor_tweak(req, false);
200 }
201
202 static int xor_tweak_post(struct skcipher_request *req)
203 {
204 return xor_tweak(req, true);
205 }
206
207 static void crypt_done(struct crypto_async_request *areq, int err)
208 {
209 struct skcipher_request *req = areq->data;
210
211 if (!err) {
212 struct rctx *rctx = skcipher_request_ctx(req);
213
214 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
215 err = xor_tweak_post(req);
216 }
217
218 skcipher_request_complete(req, err);
219 }
220
221 static void init_crypt(struct skcipher_request *req)
222 {
223 struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
224 struct rctx *rctx = skcipher_request_ctx(req);
225 struct skcipher_request *subreq = &rctx->subreq;
226
227 skcipher_request_set_tfm(subreq, ctx->child);
228 skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req);
229 /* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
230 skcipher_request_set_crypt(subreq, req->dst, req->dst,
231 req->cryptlen, req->iv);
232
233 /* calculate first value of T */
234 memcpy(&rctx->t, req->iv, sizeof(rctx->t));
235
236 /* T <- I*Key2 */
237 gf128mul_64k_bbe(&rctx->t, ctx->table);
238 }
239
240 static int encrypt(struct skcipher_request *req)
241 {
242 struct rctx *rctx = skcipher_request_ctx(req);
243 struct skcipher_request *subreq = &rctx->subreq;
244
245 init_crypt(req);
246 return xor_tweak_pre(req) ?:
247 crypto_skcipher_encrypt(subreq) ?:
248 xor_tweak_post(req);
249 }
250
251 static int decrypt(struct skcipher_request *req)
252 {
253 struct rctx *rctx = skcipher_request_ctx(req);
254 struct skcipher_request *subreq = &rctx->subreq;
255
256 init_crypt(req);
257 return xor_tweak_pre(req) ?:
258 crypto_skcipher_decrypt(subreq) ?:
259 xor_tweak_post(req);
260 }
261
262 static int init_tfm(struct crypto_skcipher *tfm)
263 {
264 struct skcipher_instance *inst = skcipher_alg_instance(tfm);
265 struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
266 struct priv *ctx = crypto_skcipher_ctx(tfm);
267 struct crypto_skcipher *cipher;
268
269 cipher = crypto_spawn_skcipher(spawn);
270 if (IS_ERR(cipher))
271 return PTR_ERR(cipher);
272
273 ctx->child = cipher;
274
275 crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
276 sizeof(struct rctx));
277
278 return 0;
279 }
280
281 static void exit_tfm(struct crypto_skcipher *tfm)
282 {
283 struct priv *ctx = crypto_skcipher_ctx(tfm);
284
285 if (ctx->table)
286 gf128mul_free_64k(ctx->table);
287 crypto_free_skcipher(ctx->child);
288 }
289
290 static void free_inst(struct skcipher_instance *inst)
291 {
292 crypto_drop_skcipher(skcipher_instance_ctx(inst));
293 kfree(inst);
294 }
295
296 static int create(struct crypto_template *tmpl, struct rtattr **tb)
297 {
298 struct crypto_skcipher_spawn *spawn;
299 struct skcipher_instance *inst;
300 struct crypto_attr_type *algt;
301 struct skcipher_alg *alg;
302 const char *cipher_name;
303 char ecb_name[CRYPTO_MAX_ALG_NAME];
304 u32 mask;
305 int err;
306
307 algt = crypto_get_attr_type(tb);
308 if (IS_ERR(algt))
309 return PTR_ERR(algt);
310
311 if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
312 return -EINVAL;
313
314 mask = crypto_requires_sync(algt->type, algt->mask);
315
316 cipher_name = crypto_attr_alg_name(tb[1]);
317 if (IS_ERR(cipher_name))
318 return PTR_ERR(cipher_name);
319
320 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
321 if (!inst)
322 return -ENOMEM;
323
324 spawn = skcipher_instance_ctx(inst);
325
326 err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),
327 cipher_name, 0, mask);
328 if (err == -ENOENT) {
329 err = -ENAMETOOLONG;
330 if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
331 cipher_name) >= CRYPTO_MAX_ALG_NAME)
332 goto err_free_inst;
333
334 err = crypto_grab_skcipher(spawn,
335 skcipher_crypto_instance(inst),
336 ecb_name, 0, mask);
337 }
338
339 if (err)
340 goto err_free_inst;
341
342 alg = crypto_skcipher_spawn_alg(spawn);
343
344 err = -EINVAL;
345 if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
346 goto err_free_inst;
347
348 if (crypto_skcipher_alg_ivsize(alg))
349 goto err_free_inst;
350
351 err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
352 &alg->base);
353 if (err)
354 goto err_free_inst;
355
356 err = -EINVAL;
357 cipher_name = alg->base.cra_name;
358
359 /* Alas we screwed up the naming so we have to mangle the
360 * cipher name.
361 */
362 if (!strncmp(cipher_name, "ecb(", 4)) {
363 unsigned len;
364
365 len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
366 if (len < 2 || len >= sizeof(ecb_name))
367 goto err_free_inst;
368
369 if (ecb_name[len - 1] != ')')
370 goto err_free_inst;
371
372 ecb_name[len - 1] = 0;
373
374 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
375 "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
376 err = -ENAMETOOLONG;
377 goto err_free_inst;
378 }
379 } else
380 goto err_free_inst;
381
382 inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
383 inst->alg.base.cra_priority = alg->base.cra_priority;
384 inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
385 inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
386 (__alignof__(be128) - 1);
387
388 inst->alg.ivsize = LRW_BLOCK_SIZE;
389 inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
390 LRW_BLOCK_SIZE;
391 inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
392 LRW_BLOCK_SIZE;
393
394 inst->alg.base.cra_ctxsize = sizeof(struct priv);
395
396 inst->alg.init = init_tfm;
397 inst->alg.exit = exit_tfm;
398
399 inst->alg.setkey = setkey;
400 inst->alg.encrypt = encrypt;
401 inst->alg.decrypt = decrypt;
402
403 inst->free = free_inst;
404
405 err = skcipher_register_instance(tmpl, inst);
406 if (err) {
407 err_free_inst:
408 free_inst(inst);
409 }
410 return err;
411 }
412
413 static struct crypto_template crypto_tmpl = {
414 .name = "lrw",
415 .create = create,
416 .module = THIS_MODULE,
417 };
418
419 static int __init crypto_module_init(void)
420 {
421 return crypto_register_template(&crypto_tmpl);
422 }
423
424 static void __exit crypto_module_exit(void)
425 {
426 crypto_unregister_template(&crypto_tmpl);
427 }
428
429 subsys_initcall(crypto_module_init);
430 module_exit(crypto_module_exit);
431
432 MODULE_LICENSE("GPL");
433 MODULE_DESCRIPTION("LRW block cipher mode");
434 MODULE_ALIAS_CRYPTO("lrw");