1/* LRW: as defined by Cyril Guyot in
2 *	http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
3 *
4 * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
5 *
6 * Based om ecb.c
7 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
8 *
9 * This program is free software; you can redistribute it and/or modify it
10 * under the terms of the GNU General Public License as published by the Free
11 * Software Foundation; either version 2 of the License, or (at your option)
12 * any later version.
13 */
14/* This implementation is checked against the test vectors in the above
15 * document and by a test vector provided by Ken Buchanan at
16 * http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
17 *
18 * The test vectors are included in the testing module tcrypt.[ch] */
19#include <crypto/algapi.h>
20#include <linux/err.h>
21#include <linux/init.h>
22#include <linux/kernel.h>
23#include <linux/module.h>
24#include <linux/scatterlist.h>
25#include <linux/slab.h>
26
27#include <crypto/b128ops.h>
28#include <crypto/gf128mul.h>
29
30struct priv {
31	struct crypto_cipher *child;
32	/* optimizes multiplying a random (non incrementing, as at the
33	 * start of a new sector) value with key2, we could also have
34	 * used 4k optimization tables or no optimization at all. In the
35	 * latter case we would have to store key2 here */
36	struct gf128mul_64k *table;
37	/* stores:
38	 *  key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
39	 *  key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
40	 *  key2*{ 0,0,...1,1,1,1,1 }, etc
41	 * needed for optimized multiplication of incrementing values
42	 * with key2 */
43	be128 mulinc[128];
44};
45
46static inline void setbit128_bbe(void *b, int bit)
47{
48	__set_bit(bit ^ (0x80 -
49#ifdef __BIG_ENDIAN
50			 BITS_PER_LONG
51#else
52			 BITS_PER_BYTE
53#endif
54			), b);
55}
56
57static int setkey(struct crypto_tfm *parent, const u8 *key,
58		  unsigned int keylen)
59{
60	struct priv *ctx = crypto_tfm_ctx(parent);
61	struct crypto_cipher *child = ctx->child;
62	int err, i;
63	be128 tmp = { 0 };
64	int bsize = crypto_cipher_blocksize(child);
65
66	crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
67	crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
68				       CRYPTO_TFM_REQ_MASK);
69	if ((err = crypto_cipher_setkey(child, key, keylen - bsize)))
70		return err;
71	crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
72				     CRYPTO_TFM_RES_MASK);
73
74	if (ctx->table)
75		gf128mul_free_64k(ctx->table);
76
77	/* initialize multiplication table for Key2 */
78	ctx->table = gf128mul_init_64k_bbe((be128 *)(key + keylen - bsize));
79	if (!ctx->table)
80		return -ENOMEM;
81
82	/* initialize optimization table */
83	for (i = 0; i < 128; i++) {
84		setbit128_bbe(&tmp, i);
85		ctx->mulinc[i] = tmp;
86		gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
87	}
88
89	return 0;
90}
91
92struct sinfo {
93	be128 t;
94	struct crypto_tfm *tfm;
95	void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
96};
97
98static inline void inc(be128 *iv)
99{
100	be64_add_cpu(&iv->b, 1);
101	if (!iv->b)
102		be64_add_cpu(&iv->a, 1);
103}
104
105static inline void lrw_round(struct sinfo *s, void *dst, const void *src)
106{
107	be128_xor(dst, &s->t, src);		/* PP <- T xor P */
108	s->fn(s->tfm, dst, dst);		/* CC <- E(Key2,PP) */
109	be128_xor(dst, dst, &s->t);		/* C <- T xor CC */
110}
111
112/* this returns the number of consequative 1 bits starting
113 * from the right, get_index128(00 00 00 00 00 00 ... 00 00 10 FB) = 2 */
114static inline int get_index128(be128 *block)
115{
116	int x;
117	__be32 *p = (__be32 *) block;
118
119	for (p += 3, x = 0; x < 128; p--, x += 32) {
120		u32 val = be32_to_cpup(p);
121
122		if (!~val)
123			continue;
124
125		return x + ffz(val);
126	}
127
128	return x;
129}
130
131static int crypt(struct blkcipher_desc *d,
132		 struct blkcipher_walk *w, struct priv *ctx,
133		 void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
134{
135	int err;
136	unsigned int avail;
137	const int bs = crypto_cipher_blocksize(ctx->child);
138	struct sinfo s = {
139		.tfm = crypto_cipher_tfm(ctx->child),
140		.fn = fn
141	};
142	be128 *iv;
143	u8 *wsrc;
144	u8 *wdst;
145
146	err = blkcipher_walk_virt(d, w);
147	if (!(avail = w->nbytes))
148		return err;
149
150	wsrc = w->src.virt.addr;
151	wdst = w->dst.virt.addr;
152
153	/* calculate first value of T */
154	iv = (be128 *)w->iv;
155	s.t = *iv;
156
157	/* T <- I*Key2 */
158	gf128mul_64k_bbe(&s.t, ctx->table);
159
160	goto first;
161
162	for (;;) {
163		do {
164			/* T <- I*Key2, using the optimization
165			 * discussed in the specification */
166			be128_xor(&s.t, &s.t, &ctx->mulinc[get_index128(iv)]);
167			inc(iv);
168
169first:
170			lrw_round(&s, wdst, wsrc);
171
172			wsrc += bs;
173			wdst += bs;
174		} while ((avail -= bs) >= bs);
175
176		err = blkcipher_walk_done(d, w, avail);
177		if (!(avail = w->nbytes))
178			break;
179
180		wsrc = w->src.virt.addr;
181		wdst = w->dst.virt.addr;
182	}
183
184	return err;
185}
186
187static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
188		   struct scatterlist *src, unsigned int nbytes)
189{
190	struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
191	struct blkcipher_walk w;
192
193	blkcipher_walk_init(&w, dst, src, nbytes);
194	return crypt(desc, &w, ctx,
195		     crypto_cipher_alg(ctx->child)->cia_encrypt);
196}
197
198static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
199		   struct scatterlist *src, unsigned int nbytes)
200{
201	struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
202	struct blkcipher_walk w;
203
204	blkcipher_walk_init(&w, dst, src, nbytes);
205	return crypt(desc, &w, ctx,
206		     crypto_cipher_alg(ctx->child)->cia_decrypt);
207}
208
209static int init_tfm(struct crypto_tfm *tfm)
210{
211	struct crypto_cipher *cipher;
212	struct crypto_instance *inst = (void *)tfm->__crt_alg;
213	struct crypto_spawn *spawn = crypto_instance_ctx(inst);
214	struct priv *ctx = crypto_tfm_ctx(tfm);
215	u32 *flags = &tfm->crt_flags;
216
217	cipher = crypto_spawn_cipher(spawn);
218	if (IS_ERR(cipher))
219		return PTR_ERR(cipher);
220
221	if (crypto_cipher_blocksize(cipher) != 16) {
222		*flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
223		return -EINVAL;
224	}
225
226	ctx->child = cipher;
227	return 0;
228}
229
230static void exit_tfm(struct crypto_tfm *tfm)
231{
232	struct priv *ctx = crypto_tfm_ctx(tfm);
233	if (ctx->table)
234		gf128mul_free_64k(ctx->table);
235	crypto_free_cipher(ctx->child);
236}
237
238static struct crypto_instance *alloc(struct rtattr **tb)
239{
240	struct crypto_instance *inst;
241	struct crypto_alg *alg;
242	int err;
243
244	err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
245	if (err)
246		return ERR_PTR(err);
247
248	alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
249				  CRYPTO_ALG_TYPE_MASK);
250	if (IS_ERR(alg))
251		return ERR_CAST(alg);
252
253	inst = crypto_alloc_instance("lrw", alg);
254	if (IS_ERR(inst))
255		goto out_put_alg;
256
257	inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
258	inst->alg.cra_priority = alg->cra_priority;
259	inst->alg.cra_blocksize = alg->cra_blocksize;
260
261	if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7;
262	else inst->alg.cra_alignmask = alg->cra_alignmask;
263	inst->alg.cra_type = &crypto_blkcipher_type;
264
265	if (!(alg->cra_blocksize % 4))
266		inst->alg.cra_alignmask |= 3;
267	inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
268	inst->alg.cra_blkcipher.min_keysize =
269		alg->cra_cipher.cia_min_keysize + alg->cra_blocksize;
270	inst->alg.cra_blkcipher.max_keysize =
271		alg->cra_cipher.cia_max_keysize + alg->cra_blocksize;
272
273	inst->alg.cra_ctxsize = sizeof(struct priv);
274
275	inst->alg.cra_init = init_tfm;
276	inst->alg.cra_exit = exit_tfm;
277
278	inst->alg.cra_blkcipher.setkey = setkey;
279	inst->alg.cra_blkcipher.encrypt = encrypt;
280	inst->alg.cra_blkcipher.decrypt = decrypt;
281
282out_put_alg:
283	crypto_mod_put(alg);
284	return inst;
285}
286
287static void free(struct crypto_instance *inst)
288{
289	crypto_drop_spawn(crypto_instance_ctx(inst));
290	kfree(inst);
291}
292
293static struct crypto_template crypto_tmpl = {
294	.name = "lrw",
295	.alloc = alloc,
296	.free = free,
297	.module = THIS_MODULE,
298};
299
300static int __init crypto_module_init(void)
301{
302	return crypto_register_template(&crypto_tmpl);
303}
304
305static void __exit crypto_module_exit(void)
306{
307	crypto_unregister_template(&crypto_tmpl);
308}
309
310module_init(crypto_module_init);
311module_exit(crypto_module_exit);
312
313MODULE_LICENSE("GPL");
314MODULE_DESCRIPTION("LRW block cipher mode");
315