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                 struct rctx *rctx = skcipher_request_ctx(req);
 217
 218                 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
 219                 err = xor_tweak_post(req);
 220         }
 221
 222         skcipher_request_complete(req, err);
 223 }
 224
 225 static void init_crypt(struct skcipher_request *req)
 226 {
 227         struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
 228         struct rctx *rctx = skcipher_request_ctx(req);
 229         struct skcipher_request *subreq = &rctx->subreq;
 230
 231         skcipher_request_set_tfm(subreq, ctx->child);
 232         skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req);
 233         /* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
 234         skcipher_request_set_crypt(subreq, req->dst, req->dst,
 235                                    req->cryptlen, req->iv);
 236
 237         /* calculate first value of T */
 238         memcpy(&rctx->t, req->iv, sizeof(rctx->t));
 239
 240         /* T <- I*Key2 */
 241         gf128mul_64k_bbe(&rctx->t, ctx->table);
 242 }
 243
 244 static int encrypt(struct skcipher_request *req)
 245 {
 246         struct rctx *rctx = skcipher_request_ctx(req);
 247         struct skcipher_request *subreq = &rctx->subreq;
 248
 249         init_crypt(req);
 250         return xor_tweak_pre(req) ?:
 251                 crypto_skcipher_encrypt(subreq) ?:
 252                 xor_tweak_post(req);
 253 }
 254
 255 static int decrypt(struct skcipher_request *req)
 256 {
 257         struct rctx *rctx = skcipher_request_ctx(req);
 258         struct skcipher_request *subreq = &rctx->subreq;
 259
 260         init_crypt(req);
 261         return xor_tweak_pre(req) ?:
 262                 crypto_skcipher_decrypt(subreq) ?:
 263                 xor_tweak_post(req);
 264 }
 265
 266 static int init_tfm(struct crypto_skcipher *tfm)
 267 {
 268         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 269         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 270         struct priv *ctx = crypto_skcipher_ctx(tfm);
 271         struct crypto_skcipher *cipher;
 272
 273         cipher = crypto_spawn_skcipher(spawn);
 274         if (IS_ERR(cipher))
 275                 return PTR_ERR(cipher);
 276
 277         ctx->child = cipher;
 278
 279         crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
 280                                          sizeof(struct rctx));
 281
 282         return 0;
 283 }
 284
 285 static void exit_tfm(struct crypto_skcipher *tfm)
 286 {
 287         struct priv *ctx = crypto_skcipher_ctx(tfm);
 288
 289         if (ctx->table)
 290                 gf128mul_free_64k(ctx->table);
 291         crypto_free_skcipher(ctx->child);
 292 }
 293
 294 static void free(struct skcipher_instance *inst)
 295 {
 296         crypto_drop_skcipher(skcipher_instance_ctx(inst));
 297         kfree(inst);
 298 }
 299
 300 static int create(struct crypto_template *tmpl, struct rtattr **tb)
 301 {
 302         struct crypto_skcipher_spawn *spawn;
 303         struct skcipher_instance *inst;
 304         struct crypto_attr_type *algt;
 305         struct skcipher_alg *alg;
 306         const char *cipher_name;
 307         char ecb_name[CRYPTO_MAX_ALG_NAME];
 308         int err;
 309
 310         algt = crypto_get_attr_type(tb);
 311         if (IS_ERR(algt))
 312                 return PTR_ERR(algt);
 313
 314         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 315                 return -EINVAL;
 316
 317         cipher_name = crypto_attr_alg_name(tb[1]);
 318         if (IS_ERR(cipher_name))
 319                 return PTR_ERR(cipher_name);
 320
 321         inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
 322         if (!inst)
 323                 return -ENOMEM;
 324
 325         spawn = skcipher_instance_ctx(inst);
 326
 327         crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
 328         err = crypto_grab_skcipher(spawn, cipher_name, 0,
 329                                    crypto_requires_sync(algt->type,
 330                                                         algt->mask));
 331         if (err == -ENOENT) {
 332                 err = -ENAMETOOLONG;
 333                 if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
 334                              cipher_name) >= CRYPTO_MAX_ALG_NAME)
 335                         goto err_free_inst;
 336
 337                 err = crypto_grab_skcipher(spawn, ecb_name, 0,
 338                                            crypto_requires_sync(algt->type,
 339                                                                 algt->mask));
 340         }
 341
 342         if (err)
 343                 goto err_free_inst;
 344
 345         alg = crypto_skcipher_spawn_alg(spawn);
 346
 347         err = -EINVAL;
 348         if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
 349                 goto err_drop_spawn;
 350
 351         if (crypto_skcipher_alg_ivsize(alg))
 352                 goto err_drop_spawn;
 353
 354         err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
 355                                   &alg->base);
 356         if (err)
 357                 goto err_drop_spawn;
 358
 359         err = -EINVAL;
 360         cipher_name = alg->base.cra_name;
 361
 362         /* Alas we screwed up the naming so we have to mangle the
 363          * cipher name.
 364          */
 365         if (!strncmp(cipher_name, "ecb(", 4)) {
 366                 unsigned len;
 367
 368                 len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
 369                 if (len < 2 || len >= sizeof(ecb_name))
 370                         goto err_drop_spawn;
 371
 372                 if (ecb_name[len - 1] != ')')
 373                         goto err_drop_spawn;
 374
 375                 ecb_name[len - 1] = 0;
 376
 377                 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 378                              "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
 379                         err = -ENAMETOOLONG;
 380                         goto err_drop_spawn;
 381                 }
 382         } else
 383                 goto err_drop_spawn;
 384
 385         inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
 386         inst->alg.base.cra_priority = alg->base.cra_priority;
 387         inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
 388         inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
 389                                        (__alignof__(__be32) - 1);
 390
 391         inst->alg.ivsize = LRW_BLOCK_SIZE;
 392         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
 393                                 LRW_BLOCK_SIZE;
 394         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
 395                                 LRW_BLOCK_SIZE;
 396
 397         inst->alg.base.cra_ctxsize = sizeof(struct priv);
 398
 399         inst->alg.init = init_tfm;
 400         inst->alg.exit = exit_tfm;
 401
 402         inst->alg.setkey = setkey;
 403         inst->alg.encrypt = encrypt;
 404         inst->alg.decrypt = decrypt;
 405
 406         inst->free = free;
 407
 408         err = skcipher_register_instance(tmpl, inst);
 409         if (err)
 410                 goto err_drop_spawn;
 411
 412 out:
 413         return err;
 414
 415 err_drop_spawn:
 416         crypto_drop_skcipher(spawn);
 417 err_free_inst:
 418         kfree(inst);
 419         goto out;
 420 }
 421
 422 static struct crypto_template crypto_tmpl = {
 423         .name = "lrw",
 424         .create = create,
 425         .module = THIS_MODULE,
 426 };
 427
 428 static int __init crypto_module_init(void)
 429 {
 430         return crypto_register_template(&crypto_tmpl);
 431 }
 432
 433 static void __exit crypto_module_exit(void)
 434 {
 435         crypto_unregister_template(&crypto_tmpl);
 436 }
 437
 438 module_init(crypto_module_init);
 439 module_exit(crypto_module_exit);
 440
 441 MODULE_LICENSE("GPL");
 442 MODULE_DESCRIPTION("LRW block cipher mode");
 443 MODULE_ALIAS_CRYPTO("lrw");