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 
30 struct 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 
52 struct lrw_request_ctx {
53 	be128 t;
54 	struct skcipher_request subreq;
55 };
56 
lrw_setbit128_bbe(void * b,int bit)57 static 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 
lrw_setkey(struct crypto_skcipher * parent,const u8 * key,unsigned int keylen)68 static int lrw_setkey(struct crypto_skcipher *parent, const u8 *key,
69 		      unsigned int keylen)
70 {
71 	struct lrw_tfm_ctx *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 		lrw_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 = lrw_next_index(&counter);
112  * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
113  */
lrw_next_index(u32 * counter)114 static 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  */
lrw_xor_tweak(struct skcipher_request * req,bool second_pass)140 static 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(&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,
182 				  &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(&w, avail);
193 	}
194 
195 	return err;
196 }
197 
lrw_xor_tweak_pre(struct skcipher_request * req)198 static int lrw_xor_tweak_pre(struct skcipher_request *req)
199 {
200 	return lrw_xor_tweak(req, false);
201 }
202 
lrw_xor_tweak_post(struct skcipher_request * req)203 static int lrw_xor_tweak_post(struct skcipher_request *req)
204 {
205 	return lrw_xor_tweak(req, true);
206 }
207 
lrw_crypt_done(void * data,int err)208 static 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 
lrw_init_crypt(struct skcipher_request * req)222 static void lrw_init_crypt(struct skcipher_request *req)
223 {
224 	const struct lrw_tfm_ctx *ctx =
225 		crypto_skcipher_ctx(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(subreq, ctx->child);
230 	skcipher_request_set_callback(subreq, req->base.flags, lrw_crypt_done,
231 				      req);
232 	/* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
233 	skcipher_request_set_crypt(subreq, req->dst, req->dst,
234 				   req->cryptlen, 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(&rctx->t, ctx->table);
241 }
242 
lrw_encrypt(struct skcipher_request * req)243 static 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(subreq) ?:
251 		lrw_xor_tweak_post(req);
252 }
253 
lrw_decrypt(struct skcipher_request * req)254 static 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(subreq) ?:
262 		lrw_xor_tweak_post(req);
263 }
264 
lrw_init_tfm(struct crypto_skcipher * tfm)265 static int lrw_init_tfm(struct crypto_skcipher *tfm)
266 {
267 	struct skcipher_instance *inst = skcipher_alg_instance(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(cipher))
274 		return PTR_ERR(cipher);
275 
276 	ctx->child = cipher;
277 
278 	crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
279 					 sizeof(struct lrw_request_ctx));
280 
281 	return 0;
282 }
283 
lrw_exit_tfm(struct crypto_skcipher * tfm)284 static 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(ctx->table);
290 	crypto_free_skcipher(ctx->child);
291 }
292 
lrw_free_instance(struct skcipher_instance * inst)293 static void lrw_free_instance(struct skcipher_instance *inst)
294 {
295 	crypto_drop_skcipher(skcipher_instance_ctx(inst));
296 	kfree(inst);
297 }
298 
lrw_create(struct crypto_template * tmpl,struct rtattr ** tb)299 static int lrw_create(struct crypto_template *tmpl, struct rtattr **tb)
300 {
301 	struct crypto_skcipher_spawn *spawn;
302 	struct skcipher_instance *inst;
303 	struct skcipher_alg *alg;
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);
310 	if (err)
311 		return err;
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 	err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),
324 				   cipher_name, 0, mask);
325 	if (err == -ENOENT) {
326 		err = -ENAMETOOLONG;
327 		if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
328 			     cipher_name) >= CRYPTO_MAX_ALG_NAME)
329 			goto err_free_inst;
330 
331 		err = crypto_grab_skcipher(spawn,
332 					   skcipher_crypto_instance(inst),
333 					   ecb_name, 0, mask);
334 	}
335 
336 	if (err)
337 		goto err_free_inst;
338 
339 	alg = crypto_skcipher_spawn_alg(spawn);
340 
341 	err = -EINVAL;
342 	if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
343 		goto err_free_inst;
344 
345 	if (crypto_skcipher_alg_ivsize(alg))
346 		goto err_free_inst;
347 
348 	err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
349 				  &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 		unsigned len;
361 
362 		len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
363 		if (len < 2 || len >= sizeof(ecb_name))
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(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
372 			     "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 = crypto_skcipher_alg_min_keysize(alg) +
386 				LRW_BLOCK_SIZE;
387 	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
388 				LRW_BLOCK_SIZE;
389 
390 	inst->alg.base.cra_ctxsize = sizeof(struct lrw_tfm_ctx);
391 
392 	inst->alg.init = lrw_init_tfm;
393 	inst->alg.exit = lrw_exit_tfm;
394 
395 	inst->alg.setkey = lrw_setkey;
396 	inst->alg.encrypt = lrw_encrypt;
397 	inst->alg.decrypt = lrw_decrypt;
398 
399 	inst->free = lrw_free_instance;
400 
401 	err = skcipher_register_instance(tmpl, inst);
402 	if (err) {
403 err_free_inst:
404 		lrw_free_instance(inst);
405 	}
406 	return err;
407 }
408 
409 static struct crypto_template lrw_tmpl = {
410 	.name = "lrw",
411 	.create = lrw_create,
412 	.module = THIS_MODULE,
413 };
414 
lrw_module_init(void)415 static int __init lrw_module_init(void)
416 {
417 	return crypto_register_template(&lrw_tmpl);
418 }
419 
lrw_module_exit(void)420 static void __exit lrw_module_exit(void)
421 {
422 	crypto_unregister_template(&lrw_tmpl);
423 }
424 
425 subsys_initcall(lrw_module_init);
426 module_exit(lrw_module_exit);
427 
428 MODULE_LICENSE("GPL");
429 MODULE_DESCRIPTION("LRW block cipher mode");
430 MODULE_ALIAS_CRYPTO("lrw");
431 MODULE_SOFTDEP("pre: ecb");
432