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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 | |
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 | |
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 | |
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 | |
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 */ |
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 | |
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 | |
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 | |
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 | |
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 | |
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 | |
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 | |
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 | |
300 | static int __init crypto_module_init(void) |
301 | { |
302 | return crypto_register_template(&crypto_tmpl); |
303 | } |
304 | |
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 |
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