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
30 struct 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
setbit128_bbe(void * b,int bit)46 static 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
setkey(struct crypto_tfm * parent,const u8 * key,unsigned int keylen)57 static 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
92 struct sinfo {
93 be128 t;
94 struct crypto_tfm *tfm;
95 void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
96 };
97
inc(be128 * iv)98 static 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
lrw_round(struct sinfo * s,void * dst,const void * src)105 static 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 */
get_index128(be128 * block)114 static 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
crypt(struct blkcipher_desc * d,struct blkcipher_walk * w,struct priv * ctx,void (* fn)(struct crypto_tfm *,u8 *,const u8 *))131 static 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
169 first:
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
encrypt(struct blkcipher_desc * desc,struct scatterlist * dst,struct scatterlist * src,unsigned int nbytes)187 static 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
decrypt(struct blkcipher_desc * desc,struct scatterlist * dst,struct scatterlist * src,unsigned int nbytes)198 static 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
init_tfm(struct crypto_tfm * tfm)209 static 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
exit_tfm(struct crypto_tfm * tfm)230 static 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
alloc(struct rtattr ** tb)238 static 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
282 out_put_alg:
283 crypto_mod_put(alg);
284 return inst;
285 }
286
free(struct crypto_instance * inst)287 static void free(struct crypto_instance *inst)
288 {
289 crypto_drop_spawn(crypto_instance_ctx(inst));
290 kfree(inst);
291 }
292
293 static struct crypto_template crypto_tmpl = {
294 .name = "lrw",
295 .alloc = alloc,
296 .free = free,
297 .module = THIS_MODULE,
298 };
299
crypto_module_init(void)300 static int __init crypto_module_init(void)
301 {
302 return crypto_register_template(&crypto_tmpl);
303 }
304
crypto_module_exit(void)305 static void __exit crypto_module_exit(void)
306 {
307 crypto_unregister_template(&crypto_tmpl);
308 }
309
310 module_init(crypto_module_init);
311 module_exit(crypto_module_exit);
312
313 MODULE_LICENSE("GPL");
314 MODULE_DESCRIPTION("LRW block cipher mode");
315