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 * https://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
30struct lrw_tfm_ctx {
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
52struct lrw_request_ctx {
53 be128 t;
54 struct skcipher_request subreq;
55};
56
57static inline void lrw_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
68static int lrw_setkey(struct crypto_skcipher *parent, const u8 *key,
69 unsigned int keylen)
70{
71 struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(tfm: 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(tfm: child, CRYPTO_TFM_REQ_MASK);
79 crypto_skcipher_set_flags(tfm: child, flags: crypto_skcipher_get_flags(tfm: parent) &
80 CRYPTO_TFM_REQ_MASK);
81 err = crypto_skcipher_setkey(tfm: child, key, keylen: keylen - bsize);
82 if (err)
83 return err;
84
85 if (ctx->table)
86 gf128mul_free_64k(t: ctx->table);
87
88 /* initialize multiplication table for Key2 */
89 ctx->table = gf128mul_init_64k_bbe(g: (be128 *)tweak);
90 if (!ctx->table)
91 return -ENOMEM;
92
93 /* initialize optimization table */
94 for (i = 0; i < 128; i++) {
95 lrw_setbit128_bbe(b: &tmp, bit: i);
96 ctx->mulinc[i] = tmp;
97 gf128mul_64k_bbe(a: &ctx->mulinc[i], t: 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 = lrw_next_index(&counter);
112 * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
113 */
114static int lrw_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 lrw_next_index() calls again.
139 */
140static int lrw_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 const struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
145 struct lrw_request_ctx *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(walk: &w, req, atomic: 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(r: wdst++, p: &t, q: wsrc++);
178
179 /* T <- I*Key2, using the optimization
180 * discussed in the specification */
181 be128_xor(r: &t, p: &t,
182 q: &ctx->mulinc[lrw_next_index(counter)]);
183 } while ((avail -= bs) >= bs);
184
185 if (second_pass && w.nbytes == w.total) {
186 iv[0] = cpu_to_be32(counter[3]);
187 iv[1] = cpu_to_be32(counter[2]);
188 iv[2] = cpu_to_be32(counter[1]);
189 iv[3] = cpu_to_be32(counter[0]);
190 }
191
192 err = skcipher_walk_done(walk: &w, err: avail);
193 }
194
195 return err;
196}
197
198static int lrw_xor_tweak_pre(struct skcipher_request *req)
199{
200 return lrw_xor_tweak(req, second_pass: false);
201}
202
203static int lrw_xor_tweak_post(struct skcipher_request *req)
204{
205 return lrw_xor_tweak(req, second_pass: true);
206}
207
208static void lrw_crypt_done(void *data, int err)
209{
210 struct skcipher_request *req = data;
211
212 if (!err) {
213 struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
214
215 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
216 err = lrw_xor_tweak_post(req);
217 }
218
219 skcipher_request_complete(req, err);
220}
221
222static void lrw_init_crypt(struct skcipher_request *req)
223{
224 const struct lrw_tfm_ctx *ctx =
225 crypto_skcipher_ctx(tfm: crypto_skcipher_reqtfm(req));
226 struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
227 struct skcipher_request *subreq = &rctx->subreq;
228
229 skcipher_request_set_tfm(req: subreq, tfm: ctx->child);
230 skcipher_request_set_callback(req: subreq, flags: req->base.flags, compl: lrw_crypt_done,
231 data: req);
232 /* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
233 skcipher_request_set_crypt(req: subreq, src: req->dst, dst: req->dst,
234 cryptlen: req->cryptlen, iv: req->iv);
235
236 /* calculate first value of T */
237 memcpy(&rctx->t, req->iv, sizeof(rctx->t));
238
239 /* T <- I*Key2 */
240 gf128mul_64k_bbe(a: &rctx->t, t: ctx->table);
241}
242
243static int lrw_encrypt(struct skcipher_request *req)
244{
245 struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
246 struct skcipher_request *subreq = &rctx->subreq;
247
248 lrw_init_crypt(req);
249 return lrw_xor_tweak_pre(req) ?:
250 crypto_skcipher_encrypt(req: subreq) ?:
251 lrw_xor_tweak_post(req);
252}
253
254static int lrw_decrypt(struct skcipher_request *req)
255{
256 struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
257 struct skcipher_request *subreq = &rctx->subreq;
258
259 lrw_init_crypt(req);
260 return lrw_xor_tweak_pre(req) ?:
261 crypto_skcipher_decrypt(req: subreq) ?:
262 lrw_xor_tweak_post(req);
263}
264
265static int lrw_init_tfm(struct crypto_skcipher *tfm)
266{
267 struct skcipher_instance *inst = skcipher_alg_instance(skcipher: tfm);
268 struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
269 struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
270 struct crypto_skcipher *cipher;
271
272 cipher = crypto_spawn_skcipher(spawn);
273 if (IS_ERR(ptr: cipher))
274 return PTR_ERR(ptr: cipher);
275
276 ctx->child = cipher;
277
278 crypto_skcipher_set_reqsize(skcipher: tfm, reqsize: crypto_skcipher_reqsize(tfm: cipher) +
279 sizeof(struct lrw_request_ctx));
280
281 return 0;
282}
283
284static void lrw_exit_tfm(struct crypto_skcipher *tfm)
285{
286 struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
287
288 if (ctx->table)
289 gf128mul_free_64k(t: ctx->table);
290 crypto_free_skcipher(tfm: ctx->child);
291}
292
293static void lrw_free_instance(struct skcipher_instance *inst)
294{
295 crypto_drop_skcipher(spawn: skcipher_instance_ctx(inst));
296 kfree(objp: inst);
297}
298
299static int lrw_create(struct crypto_template *tmpl, struct rtattr **tb)
300{
301 struct crypto_skcipher_spawn *spawn;
302 struct skcipher_alg_common *alg;
303 struct skcipher_instance *inst;
304 const char *cipher_name;
305 char ecb_name[CRYPTO_MAX_ALG_NAME];
306 u32 mask;
307 int err;
308
309 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, mask_ret: &mask);
310 if (err)
311 return err;
312
313 cipher_name = crypto_attr_alg_name(rta: tb[1]);
314 if (IS_ERR(ptr: cipher_name))
315 return PTR_ERR(ptr: cipher_name);
316
317 inst = kzalloc(size: sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
318 if (!inst)
319 return -ENOMEM;
320
321 spawn = skcipher_instance_ctx(inst);
322
323 err = crypto_grab_skcipher(spawn, inst: skcipher_crypto_instance(inst),
324 name: cipher_name, type: 0, mask);
325 if (err == -ENOENT) {
326 err = -ENAMETOOLONG;
327 if (snprintf(buf: ecb_name, CRYPTO_MAX_ALG_NAME, fmt: "ecb(%s)",
328 cipher_name) >= CRYPTO_MAX_ALG_NAME)
329 goto err_free_inst;
330
331 err = crypto_grab_skcipher(spawn,
332 inst: skcipher_crypto_instance(inst),
333 name: ecb_name, type: 0, mask);
334 }
335
336 if (err)
337 goto err_free_inst;
338
339 alg = crypto_spawn_skcipher_alg_common(spawn);
340
341 err = -EINVAL;
342 if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
343 goto err_free_inst;
344
345 if (alg->ivsize)
346 goto err_free_inst;
347
348 err = crypto_inst_setname(inst: skcipher_crypto_instance(inst), name: "lrw",
349 alg: &alg->base);
350 if (err)
351 goto err_free_inst;
352
353 err = -EINVAL;
354 cipher_name = alg->base.cra_name;
355
356 /* Alas we screwed up the naming so we have to mangle the
357 * cipher name.
358 */
359 if (!strncmp(cipher_name, "ecb(", 4)) {
360 int len;
361
362 len = strscpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
363 if (len < 2)
364 goto err_free_inst;
365
366 if (ecb_name[len - 1] != ')')
367 goto err_free_inst;
368
369 ecb_name[len - 1] = 0;
370
371 if (snprintf(buf: inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
372 fmt: "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
373 err = -ENAMETOOLONG;
374 goto err_free_inst;
375 }
376 } else
377 goto err_free_inst;
378
379 inst->alg.base.cra_priority = alg->base.cra_priority;
380 inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
381 inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
382 (__alignof__(be128) - 1);
383
384 inst->alg.ivsize = LRW_BLOCK_SIZE;
385 inst->alg.min_keysize = alg->min_keysize + LRW_BLOCK_SIZE;
386 inst->alg.max_keysize = alg->max_keysize + LRW_BLOCK_SIZE;
387
388 inst->alg.base.cra_ctxsize = sizeof(struct lrw_tfm_ctx);
389
390 inst->alg.init = lrw_init_tfm;
391 inst->alg.exit = lrw_exit_tfm;
392
393 inst->alg.setkey = lrw_setkey;
394 inst->alg.encrypt = lrw_encrypt;
395 inst->alg.decrypt = lrw_decrypt;
396
397 inst->free = lrw_free_instance;
398
399 err = skcipher_register_instance(tmpl, inst);
400 if (err) {
401err_free_inst:
402 lrw_free_instance(inst);
403 }
404 return err;
405}
406
407static struct crypto_template lrw_tmpl = {
408 .name = "lrw",
409 .create = lrw_create,
410 .module = THIS_MODULE,
411};
412
413static int __init lrw_module_init(void)
414{
415 return crypto_register_template(tmpl: &lrw_tmpl);
416}
417
418static void __exit lrw_module_exit(void)
419{
420 crypto_unregister_template(tmpl: &lrw_tmpl);
421}
422
423subsys_initcall(lrw_module_init);
424module_exit(lrw_module_exit);
425
426MODULE_LICENSE("GPL");
427MODULE_DESCRIPTION("LRW block cipher mode");
428MODULE_ALIAS_CRYPTO("lrw");
429MODULE_SOFTDEP("pre: ecb");
430

source code of linux/crypto/lrw.c