xref: /openbmc/linux/crypto/lrw.c (revision 0e01d176d5788f66dc64a7e61119edb56eb08339)
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  
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  
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   */
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   */
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  
198  static int lrw_xor_tweak_pre(struct skcipher_request *req)
199  {
200  	return lrw_xor_tweak(req, false);
201  }
202  
203  static int lrw_xor_tweak_post(struct skcipher_request *req)
204  {
205  	return lrw_xor_tweak(req, true);
206  }
207  
208  static void lrw_crypt_done(struct crypto_async_request *areq, int err)
209  {
210  	struct skcipher_request *req = areq->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  
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  
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  
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  
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  
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  
293  static void lrw_free_instance(struct skcipher_instance *inst)
294  {
295  	crypto_drop_skcipher(skcipher_instance_ctx(inst));
296  	kfree(inst);
297  }
298  
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  
415  static int __init lrw_module_init(void)
416  {
417  	return crypto_register_template(&lrw_tmpl);
418  }
419  
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