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TOMOYO Linux Cross Reference
Linux/crypto/lrw.c

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  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 
 34 struct 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 
 56 struct rctx {
 57         be128 t;
 58         struct skcipher_request subreq;
 59 };
 60 
 61 static 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 
 72 static 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  */
120 static 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  */
146 static 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 
201 static int xor_tweak_pre(struct skcipher_request *req)
202 {
203         return xor_tweak(req, false);
204 }
205 
206 static int xor_tweak_post(struct skcipher_request *req)
207 {
208         return xor_tweak(req, true);
209 }
210 
211 static 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 
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(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         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 
408 out:
409         return err;
410 
411 err_drop_spawn:
412         crypto_drop_skcipher(spawn);
413 err_free_inst:
414         kfree(inst);
415         goto out;
416 }
417 
418 static struct crypto_template crypto_tmpl = {
419         .name = "lrw",
420         .create = create,
421         .module = THIS_MODULE,
422 };
423 
424 static int __init crypto_module_init(void)
425 {
426         return crypto_register_template(&crypto_tmpl);
427 }
428 
429 static void __exit crypto_module_exit(void)
430 {
431         crypto_unregister_template(&crypto_tmpl);
432 }
433 
434 module_init(crypto_module_init);
435 module_exit(crypto_module_exit);
436 
437 MODULE_LICENSE("GPL");
438 MODULE_DESCRIPTION("LRW block cipher mode");
439 MODULE_ALIAS_CRYPTO("lrw");
440 

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