lrw.c

  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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Linux/crypto/lrw.c
