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(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 */
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(&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
198static int lrw_xor_tweak_pre(struct skcipher_request *req)
199{
200	return lrw_xor_tweak(req, false);
201}
202
203static int lrw_xor_tweak_post(struct skcipher_request *req)
204{
205	return lrw_xor_tweak(req, 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(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
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(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(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(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
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(ctx->table);
290	crypto_free_skcipher(ctx->child);
291}
292
293static void lrw_free_instance(struct skcipher_instance *inst)
294{
295	crypto_drop_skcipher(skcipher_instance_ctx(inst));
296	kfree(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);
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_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(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		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(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 = 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(&lrw_tmpl);
416}
417
418static void __exit lrw_module_exit(void)
419{
420	crypto_unregister_template(&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