1/* LRW: as defined by Cyril Guyot in
2 * http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
3 *
4 * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
5 *
6 * Based on ecb.c
7 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
8 *
9 * This program is free software; you can redistribute it and/or modify it
10 * under the terms of the GNU General Public License as published by the Free
11 * Software Foundation; either version 2 of the License, or (at your option)
12 * any later version.
13 */
14/* This implementation is checked against the test vectors in the above
15 * document and by a test vector provided by Ken Buchanan at
16 * http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
17 *
18 * The test vectors are included in the testing module tcrypt.[ch] */
19
20#include <crypto/internal/skcipher.h>
21#include <crypto/scatterwalk.h>
22#include <linux/err.h>
23#include <linux/init.h>
24#include <linux/kernel.h>
25#include <linux/module.h>
26#include <linux/scatterlist.h>
27#include <linux/slab.h>
28
29#include <crypto/b128ops.h>
30#include <crypto/gf128mul.h>
31
32#define LRW_BLOCK_SIZE 16
33
34struct priv {
35 struct crypto_skcipher *child;
36
37 /*
38 * optimizes multiplying a random (non incrementing, as at the
39 * start of a new sector) value with key2, we could also have
40 * used 4k optimization tables or no optimization at all. In the
41 * latter case we would have to store key2 here
42 */
43 struct gf128mul_64k *table;
44
45 /*
46 * stores:
47 * key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
48 * key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
49 * key2*{ 0,0,...1,1,1,1,1 }, etc
50 * needed for optimized multiplication of incrementing values
51 * with key2
52 */
53 be128 mulinc[128];
54};
55
56struct rctx {
57 be128 t;
58 struct skcipher_request subreq;
59};
60
61static inline void setbit128_bbe(void *b, int bit)
62{
63 __set_bit(bit ^ (0x80 -
64#ifdef __BIG_ENDIAN
65 BITS_PER_LONG
66#else
67 BITS_PER_BYTE
68#endif
69 ), b);
70}
71
72static int setkey(struct crypto_skcipher *parent, const u8 *key,
73 unsigned int keylen)
74{
75 struct priv *ctx = crypto_skcipher_ctx(parent);
76 struct crypto_skcipher *child = ctx->child;
77 int err, bsize = LRW_BLOCK_SIZE;
78 const u8 *tweak = key + keylen - bsize;
79 be128 tmp = { 0 };
80 int i;
81
82 crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
83 crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
84 CRYPTO_TFM_REQ_MASK);
85 err = crypto_skcipher_setkey(child, key, keylen - bsize);
86 crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
87 CRYPTO_TFM_RES_MASK);
88 if (err)
89 return err;
90
91 if (ctx->table)
92 gf128mul_free_64k(ctx->table);
93
94 /* initialize multiplication table for Key2 */
95 ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
96 if (!ctx->table)
97 return -ENOMEM;
98
99 /* initialize optimization table */
100 for (i = 0; i < 128; i++) {
101 setbit128_bbe(&tmp, i);
102 ctx->mulinc[i] = tmp;
103 gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
104 }
105
106 return 0;
107}
108
109/*
110 * Returns the number of trailing '1' bits in the words of the counter, which is
111 * represented by 4 32-bit words, arranged from least to most significant.
112 * At the same time, increments the counter by one.
113 *
114 * For example:
115 *
116 * u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
117 * int i = next_index(&counter);
118 * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
119 */
120static int next_index(u32 *counter)
121{
122 int i, res = 0;
123
124 for (i = 0; i < 4; i++) {
125 if (counter[i] + 1 != 0)
126 return res + ffz(counter[i]++);
127
128 counter[i] = 0;
129 res += 32;
130 }
131
132 /*
133 * If we get here, then x == 128 and we are incrementing the counter
134 * from all ones to all zeros. This means we must return index 127, i.e.
135 * the one corresponding to key2*{ 1,...,1 }.
136 */
137 return 127;
138}
139
140/*
141 * We compute the tweak masks twice (both before and after the ECB encryption or
142 * decryption) to avoid having to allocate a temporary buffer and/or make
143 * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
144 * just doing the next_index() calls again.
145 */
146static int xor_tweak(struct skcipher_request *req, bool second_pass)
147{
148 const int bs = LRW_BLOCK_SIZE;
149 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
150 struct priv *ctx = crypto_skcipher_ctx(tfm);
151 struct rctx *rctx = skcipher_request_ctx(req);
152 be128 t = rctx->t;
153 struct skcipher_walk w;
154 __be32 *iv;
155 u32 counter[4];
156 int err;
157
158 if (second_pass) {
159 req = &rctx->subreq;
160 /* set to our TFM to enforce correct alignment: */
161 skcipher_request_set_tfm(req, tfm);
162 }
163
164 err = skcipher_walk_virt(&w, req, false);
165 iv = (__be32 *)w.iv;
166
167 counter[0] = be32_to_cpu(iv[3]);
168 counter[1] = be32_to_cpu(iv[2]);
169 counter[2] = be32_to_cpu(iv[1]);
170 counter[3] = be32_to_cpu(iv[0]);
171
172 while (w.nbytes) {
173 unsigned int avail = w.nbytes;
174 be128 *wsrc;
175 be128 *wdst;
176
177 wsrc = w.src.virt.addr;
178 wdst = w.dst.virt.addr;
179
180 do {
181 be128_xor(wdst++, &t, wsrc++);
182
183 /* T <- I*Key2, using the optimization
184 * discussed in the specification */
185 be128_xor(&t, &t, &ctx->mulinc[next_index(counter)]);
186 } while ((avail -= bs) >= bs);
187
188 if (second_pass && w.nbytes == w.total) {
189 iv[0] = cpu_to_be32(counter[3]);
190 iv[1] = cpu_to_be32(counter[2]);
191 iv[2] = cpu_to_be32(counter[1]);
192 iv[3] = cpu_to_be32(counter[0]);
193 }
194
195 err = skcipher_walk_done(&w, avail);
196 }
197
198 return err;
199}
200
201static int xor_tweak_pre(struct skcipher_request *req)
202{
203 return xor_tweak(req, false);
204}
205
206static int xor_tweak_post(struct skcipher_request *req)
207{
208 return xor_tweak(req, true);
209}
210
211static void crypt_done(struct crypto_async_request *areq, int err)
212{
213 struct skcipher_request *req = areq->data;
214
215 if (!err)
216 err = xor_tweak_post(req);
217
218 skcipher_request_complete(req, err);
219}
220
221static 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
240static 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
251static 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
262static 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
281static 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
290static void free(struct skcipher_instance *inst)
291{
292 crypto_drop_skcipher(skcipher_instance_ctx(inst));
293 kfree(inst);
294}
295
296static 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 int err;
305
306 algt = crypto_get_attr_type(tb);
307 if (IS_ERR(algt))
308 return PTR_ERR(algt);
309
310 if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
311 return -EINVAL;
312
313 cipher_name = crypto_attr_alg_name(tb[1]);
314 if (IS_ERR(cipher_name))
315 return PTR_ERR(cipher_name);
316
317 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
318 if (!inst)
319 return -ENOMEM;
320
321 spawn = skcipher_instance_ctx(inst);
322
323 crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
324 err = crypto_grab_skcipher(spawn, cipher_name, 0,
325 crypto_requires_sync(algt->type,
326 algt->mask));
327 if (err == -ENOENT) {
328 err = -ENAMETOOLONG;
329 if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
330 cipher_name) >= CRYPTO_MAX_ALG_NAME)
331 goto err_free_inst;
332
333 err = crypto_grab_skcipher(spawn, ecb_name, 0,
334 crypto_requires_sync(algt->type,
335 algt->mask));
336 }
337
338 if (err)
339 goto err_free_inst;
340
341 alg = crypto_skcipher_spawn_alg(spawn);
342
343 err = -EINVAL;
344 if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
345 goto err_drop_spawn;
346
347 if (crypto_skcipher_alg_ivsize(alg))
348 goto err_drop_spawn;
349
350 err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
351 &alg->base);
352 if (err)
353 goto err_drop_spawn;
354
355 err = -EINVAL;
356 cipher_name = alg->base.cra_name;
357
358 /* Alas we screwed up the naming so we have to mangle the
359 * cipher name.
360 */
361 if (!strncmp(cipher_name, "ecb(", 4)) {
362 unsigned len;
363
364 len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
365 if (len < 2 || len >= sizeof(ecb_name))
366 goto err_drop_spawn;
367
368 if (ecb_name[len - 1] != ')')
369 goto err_drop_spawn;
370
371 ecb_name[len - 1] = 0;
372
373 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
374 "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
375 err = -ENAMETOOLONG;
376 goto err_drop_spawn;
377 }
378 } else
379 goto err_drop_spawn;
380
381 inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
382 inst->alg.base.cra_priority = alg->base.cra_priority;
383 inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
384 inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
385 (__alignof__(__be32) - 1);
386
387 inst->alg.ivsize = LRW_BLOCK_SIZE;
388 inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
389 LRW_BLOCK_SIZE;
390 inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
391 LRW_BLOCK_SIZE;
392
393 inst->alg.base.cra_ctxsize = sizeof(struct priv);
394
395 inst->alg.init = init_tfm;
396 inst->alg.exit = exit_tfm;
397
398 inst->alg.setkey = setkey;
399 inst->alg.encrypt = encrypt;
400 inst->alg.decrypt = decrypt;
401
402 inst->free = free;
403
404 err = skcipher_register_instance(tmpl, inst);
405 if (err)
406 goto err_drop_spawn;
407
408out:
409 return err;
410
411err_drop_spawn:
412 crypto_drop_skcipher(spawn);
413err_free_inst:
414 kfree(inst);
415 goto out;
416}
417
418static struct crypto_template crypto_tmpl = {
419 .name = "lrw",
420 .create = create,
421 .module = THIS_MODULE,
422};
423
424static int __init crypto_module_init(void)
425{
426 return crypto_register_template(&crypto_tmpl);
427}
428
429static void __exit crypto_module_exit(void)
430{
431 crypto_unregister_template(&crypto_tmpl);
432}
433
434module_init(crypto_module_init);
435module_exit(crypto_module_exit);
436
437MODULE_LICENSE("GPL");
438MODULE_DESCRIPTION("LRW block cipher mode");
439MODULE_ALIAS_CRYPTO("lrw");
440