crypto/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 on 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
  20 #include <crypto/internal/skcipher.h>
  21 #include <crypto/scatterwalk.h>
  22 #include <linux/err.h>
  23 #include <linux/init.h>
  24 #include <linux/kernel.h>
  25 #include <linux/module.h>
  26 #include <linux/scatterlist.h>
  27 #include <linux/slab.h>
  28
  29 #include <crypto/b128ops.h>
  30 #include <crypto/gf128mul.h>
  31
  32 #define LRW_BLOCK_SIZE 16
  33
  34 struct priv {
  35         struct crypto_skcipher *child;
  36
  37         /*
  38          * optimizes multiplying a random (non incrementing, as at the
  39          * start of a new sector) value with key2, we could also have
  40          * used 4k optimization tables or no optimization at all. In the
  41          * latter case we would have to store key2 here
  42          */
  43         struct gf128mul_64k *table;
  44
  45         /*
  46          * stores:
  47          *  key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
  48          *  key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
  49          *  key2*{ 0,0,...1,1,1,1,1 }, etc
  50          * needed for optimized multiplication of incrementing values
  51          * with key2
  52          */
  53         be128 mulinc[128];
  54 };
  55
  56 struct rctx {
  57         be128 t;
  58         struct skcipher_request subreq;
  59 };
  60
  61 static inline void setbit128_bbe(void *b, int bit)
  62 {
  63         __set_bit(bit ^ (0x80 -
  64 #ifdef __BIG_ENDIAN
  65                          BITS_PER_LONG
  66 #else
  67                          BITS_PER_BYTE
  68 #endif
  69                         ), b);
  70 }
  71
  72 static int setkey(struct crypto_skcipher *parent, const u8 *key,
  73                   unsigned int keylen)
  74 {
  75         struct priv *ctx = crypto_skcipher_ctx(parent);
  76         struct crypto_skcipher *child = ctx->child;
  77         int err, bsize = LRW_BLOCK_SIZE;
  78         const u8 *tweak = key + keylen - bsize;
  79         be128 tmp = { 0 };
  80         int i;
  81
  82         crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  83         crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
  84                                          CRYPTO_TFM_REQ_MASK);
  85         err = crypto_skcipher_setkey(child, key, keylen - bsize);
  86         crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
  87                                           CRYPTO_TFM_RES_MASK);
  88         if (err)
  89                 return err;
  90
  91         if (ctx->table)
  92                 gf128mul_free_64k(ctx->table);
  93
  94         /* initialize multiplication table for Key2 */
  95         ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
  96         if (!ctx->table)
  97                 return -ENOMEM;
  98
  99         /* initialize optimization table */
 100         for (i = 0; i < 128; i++) {
 101                 setbit128_bbe(&tmp, i);
 102                 ctx->mulinc[i] = tmp;
 103                 gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
 104         }
 105
 106         return 0;
 107 }
 108
 109 /*
 110  * Returns the number of trailing '1' bits in the words of the counter, which is
 111  * represented by 4 32-bit words, arranged from least to most significant.
 112  * At the same time, increments the counter by one.
 113  *
 114  * For example:
 115  *
 116  * u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
 117  * int i = next_index(&counter);
 118  * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
 119  */
 120 static int next_index(u32 *counter)
 121 {
 122         int i, res = 0;
 123
 124         for (i = 0; i < 4; i++) {
 125                 if (counter[i] + 1 != 0)
 126                         return res + ffz(counter[i]++);
 127
 128                 counter[i] = 0;
 129                 res += 32;
 130         }
 131
 132         /*
 133          * If we get here, then x == 128 and we are incrementing the counter
 134          * from all ones to all zeros. This means we must return index 127, i.e.
 135          * the one corresponding to key2*{ 1,...,1 }.
 136          */
 137         return 127;
 138 }
 139
 140 /*
 141  * We compute the tweak masks twice (both before and after the ECB encryption or
 142  * decryption) to avoid having to allocate a temporary buffer and/or make
 143  * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
 144  * just doing the next_index() calls again.
 145  */
 146 static int xor_tweak(struct skcipher_request *req, bool second_pass)
 147 {
 148         const int bs = LRW_BLOCK_SIZE;
 149         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 150         struct priv *ctx = crypto_skcipher_ctx(tfm);
 151         struct rctx *rctx = skcipher_request_ctx(req);
 152         be128 t = rctx->t;
 153         struct skcipher_walk w;
 154         __be32 *iv;
 155         u32 counter[4];
 156         int err;
 157
 158         if (second_pass) {
 159                 req = &rctx->subreq;
 160                 /* set to our TFM to enforce correct alignment: */
 161                 skcipher_request_set_tfm(req, tfm);
 162         }
 163
 164         err = skcipher_walk_virt(&w, req, false);
 165         iv = (__be32 *)w.iv;
 166
 167         counter[0] = be32_to_cpu(iv[3]);
 168         counter[1] = be32_to_cpu(iv[2]);
 169         counter[2] = be32_to_cpu(iv[1]);
 170         counter[3] = be32_to_cpu(iv[0]);
 171
 172         while (w.nbytes) {
 173                 unsigned int avail = w.nbytes;
 174                 be128 *wsrc;
 175                 be128 *wdst;
 176
 177                 wsrc = w.src.virt.addr;
 178                 wdst = w.dst.virt.addr;
 179
 180                 do {
 181                         be128_xor(wdst++, &t, wsrc++);
 182
 183                         /* T <- I*Key2, using the optimization
 184                          * discussed in the specification */
 185                         be128_xor(&t, &t, &ctx->mulinc[next_index(counter)]);
 186                 } while ((avail -= bs) >= bs);
 187
 188                 if (second_pass && w.nbytes == w.total) {
 189                         iv[0] = cpu_to_be32(counter[3]);
 190                         iv[1] = cpu_to_be32(counter[2]);
 191                         iv[2] = cpu_to_be32(counter[1]);
 192                         iv[3] = cpu_to_be32(counter[0]);
 193                 }
 194
 195                 err = skcipher_walk_done(&w, avail);
 196         }
 197
 198         return err;
 199 }
 200
 201 static int xor_tweak_pre(struct skcipher_request *req)
 202 {
 203         return xor_tweak(req, false);
 204 }
 205
 206 static int xor_tweak_post(struct skcipher_request *req)
 207 {
 208         return xor_tweak(req, true);
 209 }
 210
 211 static void crypt_done(struct crypto_async_request *areq, int err)
 212 {
 213         struct skcipher_request *req = areq->data;
 214
 215         if (!err)
 216                 err = xor_tweak_post(req);
 217
 218         skcipher_request_complete(req, err);
 219 }
 220
 221 static void init_crypt(struct skcipher_request *req)
 222 {
 223         struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
 224         struct rctx *rctx = skcipher_request_ctx(req);
 225         struct skcipher_request *subreq = &rctx->subreq;
 226
 227         skcipher_request_set_tfm(subreq, ctx->child);
 228         skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req);
 229         /* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
 230         skcipher_request_set_crypt(subreq, req->dst, req->dst,
 231                                    req->cryptlen, req->iv);
 232
 233         /* calculate first value of T */
 234         memcpy(&rctx->t, req->iv, sizeof(rctx->t));
 235
 236         /* T <- I*Key2 */
 237         gf128mul_64k_bbe(&rctx->t, ctx->table);
 238 }
 239
 240 static int encrypt(struct skcipher_request *req)
 241 {
 242         struct rctx *rctx = skcipher_request_ctx(req);
 243         struct skcipher_request *subreq = &rctx->subreq;
 244
 245         init_crypt(req);
 246         return xor_tweak_pre(req) ?:
 247                 crypto_skcipher_encrypt(subreq) ?:
 248                 xor_tweak_post(req);
 249 }
 250
 251 static int decrypt(struct skcipher_request *req)
 252 {
 253         struct rctx *rctx = skcipher_request_ctx(req);
 254         struct skcipher_request *subreq = &rctx->subreq;
 255
 256         init_crypt(req);
 257         return xor_tweak_pre(req) ?:
 258                 crypto_skcipher_decrypt(subreq) ?:
 259                 xor_tweak_post(req);
 260 }
 261
 262 static int init_tfm(struct crypto_skcipher *tfm)
 263 {
 264         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 265         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 266         struct priv *ctx = crypto_skcipher_ctx(tfm);
 267         struct crypto_skcipher *cipher;
 268
 269         cipher = crypto_spawn_skcipher(spawn);
 270         if (IS_ERR(cipher))
 271                 return PTR_ERR(cipher);
 272
 273         ctx->child = cipher;
 274
 275         crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
 276                                          sizeof(struct rctx));
 277
 278         return 0;
 279 }
 280
 281 static void exit_tfm(struct crypto_skcipher *tfm)
 282 {
 283         struct priv *ctx = crypto_skcipher_ctx(tfm);
 284
 285         if (ctx->table)
 286                 gf128mul_free_64k(ctx->table);
 287         crypto_free_skcipher(ctx->child);
 288 }
 289
 290 static void free(struct skcipher_instance *inst)
 291 {
 292         crypto_drop_skcipher(skcipher_instance_ctx(inst));
 293         kfree(inst);
 294 }
 295
 296 static int create(struct crypto_template *tmpl, struct rtattr **tb)
 297 {
 298         struct crypto_skcipher_spawn *spawn;
 299         struct skcipher_instance *inst;
 300         struct crypto_attr_type *algt;
 301         struct skcipher_alg *alg;
 302         const char *cipher_name;
 303         char ecb_name[CRYPTO_MAX_ALG_NAME];
 304         int err;
 305
 306         algt = crypto_get_attr_type(tb);
 307         if (IS_ERR(algt))
 308                 return PTR_ERR(algt);
 309
 310         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 311                 return -EINVAL;
 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         crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
 324         err = crypto_grab_skcipher(spawn, cipher_name, 0,
 325                                    crypto_requires_sync(algt->type,
 326                                                         algt->mask));
 327         if (err == -ENOENT) {
 328                 err = -ENAMETOOLONG;
 329                 if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
 330                              cipher_name) >= CRYPTO_MAX_ALG_NAME)
 331                         goto err_free_inst;
 332
 333                 err = crypto_grab_skcipher(spawn, ecb_name, 0,
 334                                            crypto_requires_sync(algt->type,
 335                                                                 algt->mask));
 336         }
 337
 338         if (err)
 339                 goto err_free_inst;
 340
 341         alg = crypto_skcipher_spawn_alg(spawn);
 342
 343         err = -EINVAL;
 344         if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
 345                 goto err_drop_spawn;
 346
 347         if (crypto_skcipher_alg_ivsize(alg))
 348                 goto err_drop_spawn;
 349
 350         err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
 351                                   &alg->base);
 352         if (err)
 353                 goto err_drop_spawn;
 354
 355         err = -EINVAL;
 356         cipher_name = alg->base.cra_name;
 357
 358         /* Alas we screwed up the naming so we have to mangle the
 359          * cipher name.
 360          */
 361         if (!strncmp(cipher_name, "ecb(", 4)) {
 362                 unsigned len;
 363
 364                 len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
 365                 if (len < 2 || len >= sizeof(ecb_name))
 366                         goto err_drop_spawn;
 367
 368                 if (ecb_name[len - 1] != ')')
 369                         goto err_drop_spawn;
 370
 371                 ecb_name[len - 1] = 0;
 372
 373                 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 374                              "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
 375                         err = -ENAMETOOLONG;
 376                         goto err_drop_spawn;
 377                 }
 378         } else
 379                 goto err_drop_spawn;
 380
 381         inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
 382         inst->alg.base.cra_priority = alg->base.cra_priority;
 383         inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
 384         inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
 385                                        (__alignof__(__be32) - 1);
 386
 387         inst->alg.ivsize = LRW_BLOCK_SIZE;
 388         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
 389                                 LRW_BLOCK_SIZE;
 390         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
 391                                 LRW_BLOCK_SIZE;
 392
 393         inst->alg.base.cra_ctxsize = sizeof(struct priv);
 394
 395         inst->alg.init = init_tfm;
 396         inst->alg.exit = exit_tfm;
 397
 398         inst->alg.setkey = setkey;
 399         inst->alg.encrypt = encrypt;
 400         inst->alg.decrypt = decrypt;
 401
 402         inst->free = free;
 403
 404         err = skcipher_register_instance(tmpl, inst);
 405         if (err)
 406                 goto err_drop_spawn;
 407
 408 out:
 409         return err;
 410
 411 err_drop_spawn:
 412         crypto_drop_skcipher(spawn);
 413 err_free_inst:
 414         kfree(inst);
 415         goto out;
 416 }
 417
 418 static struct crypto_template crypto_tmpl = {
 419         .name = "lrw",
 420         .create = create,
 421         .module = THIS_MODULE,
 422 };
 423
 424 static int __init crypto_module_init(void)
 425 {
 426         return crypto_register_template(&crypto_tmpl);
 427 }
 428
 429 static void __exit crypto_module_exit(void)
 430 {
 431         crypto_unregister_template(&crypto_tmpl);
 432 }
 433
 434 module_init(crypto_module_init);
 435 module_exit(crypto_module_exit);
 436
 437 MODULE_LICENSE("GPL");
 438 MODULE_DESCRIPTION("LRW block cipher mode");
 439 MODULE_ALIAS_CRYPTO("lrw");