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Linux/crypto/lrw.c

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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         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  */
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  */
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 
199 static int xor_tweak_pre(struct skcipher_request *req)
200 {
201         return xor_tweak(req, false);
202 }
203 
204 static int xor_tweak_post(struct skcipher_request *req)
205 {
206         return xor_tweak(req, true);
207 }
208 
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 
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 
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 
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 
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 
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 
292 static void free(struct skcipher_instance *inst)
293 {
294         crypto_drop_skcipher(skcipher_instance_ctx(inst));
295         kfree(inst);
296 }
297 
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 
426 static int __init crypto_module_init(void)
427 {
428         return crypto_register_template(&crypto_tmpl);
429 }
430 
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 

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