crypto/lrw.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* LRW: as defined by Cyril Guyot in
   3  *      http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
   4  *
   5  * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
   6  *
   7  * Based on ecb.c
   8  * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
   9  */
  10 /* This implementation is checked against the test vectors in the above
  11  * document and by a test vector provided by Ken Buchanan at
  12  * http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
  13  *
  14  * The test vectors are included in the testing module tcrypt.[ch] */
  15
  16 #include <crypto/internal/skcipher.h>
  17 #include <crypto/scatterwalk.h>
  18 #include <linux/err.h>
  19 #include <linux/init.h>
  20 #include <linux/kernel.h>
  21 #include <linux/module.h>
  22 #include <linux/scatterlist.h>
  23 #include <linux/slab.h>
  24
  25 #include <crypto/b128ops.h>
  26 #include <crypto/gf128mul.h>
  27
  28 #define LRW_BLOCK_SIZE 16
  29
  30 struct priv {
  31         struct crypto_skcipher *child;
  32
  33         /*
  34          * optimizes multiplying a random (non incrementing, as at the
  35          * start of a new sector) value with key2, we could also have
  36          * used 4k optimization tables or no optimization at all. In the
  37          * latter case we would have to store key2 here
  38          */
  39         struct gf128mul_64k *table;
  40
  41         /*
  42          * stores:
  43          *  key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
  44          *  key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
  45          *  key2*{ 0,0,...1,1,1,1,1 }, etc
  46          * needed for optimized multiplication of incrementing values
  47          * with key2
  48          */
  49         be128 mulinc[128];
  50 };
  51
  52 struct rctx {
  53         be128 t;
  54         struct skcipher_request subreq;
  55 };
  56
  57 static inline void setbit128_bbe(void *b, int bit)
  58 {
  59         __set_bit(bit ^ (0x80 -
  60 #ifdef __BIG_ENDIAN
  61                          BITS_PER_LONG
  62 #else
  63                          BITS_PER_BYTE
  64 #endif
  65                         ), b);
  66 }
  67
  68 static int setkey(struct crypto_skcipher *parent, const u8 *key,
  69                   unsigned int keylen)
  70 {
  71         struct priv *ctx = crypto_skcipher_ctx(parent);
  72         struct crypto_skcipher *child = ctx->child;
  73         int err, bsize = LRW_BLOCK_SIZE;
  74         const u8 *tweak = key + keylen - bsize;
  75         be128 tmp = { 0 };
  76         int i;
  77
  78         crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  79         crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
  80                                          CRYPTO_TFM_REQ_MASK);
  81         err = crypto_skcipher_setkey(child, key, keylen - bsize);
  82         if (err)
  83                 return err;
  84
  85         if (ctx->table)
  86                 gf128mul_free_64k(ctx->table);
  87
  88         /* initialize multiplication table for Key2 */
  89         ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
  90         if (!ctx->table)
  91                 return -ENOMEM;
  92
  93         /* initialize optimization table */
  94         for (i = 0; i < 128; i++) {
  95                 setbit128_bbe(&tmp, i);
  96                 ctx->mulinc[i] = tmp;
  97                 gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
  98         }
  99
 100         return 0;
 101 }
 102
 103 /*
 104  * Returns the number of trailing '1' bits in the words of the counter, which is
 105  * represented by 4 32-bit words, arranged from least to most significant.
 106  * At the same time, increments the counter by one.
 107  *
 108  * For example:
 109  *
 110  * u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
 111  * int i = next_index(&counter);
 112  * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
 113  */
 114 static int next_index(u32 *counter)
 115 {
 116         int i, res = 0;
 117
 118         for (i = 0; i < 4; i++) {
 119                 if (counter[i] + 1 != 0)
 120                         return res + ffz(counter[i]++);
 121
 122                 counter[i] = 0;
 123                 res += 32;
 124         }
 125
 126         /*
 127          * If we get here, then x == 128 and we are incrementing the counter
 128          * from all ones to all zeros. This means we must return index 127, i.e.
 129          * the one corresponding to key2*{ 1,...,1 }.
 130          */
 131         return 127;
 132 }
 133
 134 /*
 135  * We compute the tweak masks twice (both before and after the ECB encryption or
 136  * decryption) to avoid having to allocate a temporary buffer and/or make
 137  * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
 138  * just doing the next_index() calls again.
 139  */
 140 static int xor_tweak(struct skcipher_request *req, bool second_pass)
 141 {
 142         const int bs = LRW_BLOCK_SIZE;
 143         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 144         struct priv *ctx = crypto_skcipher_ctx(tfm);
 145         struct rctx *rctx = skcipher_request_ctx(req);
 146         be128 t = rctx->t;
 147         struct skcipher_walk w;
 148         __be32 *iv;
 149         u32 counter[4];
 150         int err;
 151
 152         if (second_pass) {
 153                 req = &rctx->subreq;
 154                 /* set to our TFM to enforce correct alignment: */
 155                 skcipher_request_set_tfm(req, tfm);
 156         }
 157
 158         err = skcipher_walk_virt(&w, req, false);
 159         if (err)
 160                 return err;
 161
 162         iv = (__be32 *)w.iv;
 163         counter[0] = be32_to_cpu(iv[3]);
 164         counter[1] = be32_to_cpu(iv[2]);
 165         counter[2] = be32_to_cpu(iv[1]);
 166         counter[3] = be32_to_cpu(iv[0]);
 167
 168         while (w.nbytes) {
 169                 unsigned int avail = w.nbytes;
 170                 be128 *wsrc;
 171                 be128 *wdst;
 172
 173                 wsrc = w.src.virt.addr;
 174                 wdst = w.dst.virt.addr;
 175
 176                 do {
 177                         be128_xor(wdst++, &t, wsrc++);
 178
 179                         /* T <- I*Key2, using the optimization
 180                          * discussed in the specification */
 181                         be128_xor(&t, &t, &ctx->mulinc[next_index(counter)]);
 182                 } while ((avail -= bs) >= bs);
 183
 184                 if (second_pass && w.nbytes == w.total) {
 185                         iv[0] = cpu_to_be32(counter[3]);
 186                         iv[1] = cpu_to_be32(counter[2]);
 187                         iv[2] = cpu_to_be32(counter[1]);
 188                         iv[3] = cpu_to_be32(counter[0]);
 189                 }
 190
 191                 err = skcipher_walk_done(&w, avail);
 192         }
 193
 194         return err;
 195 }
 196
 197 static int xor_tweak_pre(struct skcipher_request *req)
 198 {
 199         return xor_tweak(req, false);
 200 }
 201
 202 static int xor_tweak_post(struct skcipher_request *req)
 203 {
 204         return xor_tweak(req, true);
 205 }
 206
 207 static void crypt_done(struct crypto_async_request *areq, int err)
 208 {
 209         struct skcipher_request *req = areq->data;
 210
 211         if (!err) {
 212                 struct rctx *rctx = skcipher_request_ctx(req);
 213
 214                 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
 215                 err = xor_tweak_post(req);
 216         }
 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 crypto_lrw_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         u32 mask;
 305         int err;
 306
 307         algt = crypto_get_attr_type(tb);
 308         if (IS_ERR(algt))
 309                 return PTR_ERR(algt);
 310
 311         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 312                 return -EINVAL;
 313
 314         mask = crypto_requires_sync(algt->type, algt->mask);
 315
 316         cipher_name = crypto_attr_alg_name(tb[1]);
 317         if (IS_ERR(cipher_name))
 318                 return PTR_ERR(cipher_name);
 319
 320         inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
 321         if (!inst)
 322                 return -ENOMEM;
 323
 324         spawn = skcipher_instance_ctx(inst);
 325
 326         err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),
 327                                    cipher_name, 0, mask);
 328         if (err == -ENOENT) {
 329                 err = -ENAMETOOLONG;
 330                 if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
 331                              cipher_name) >= CRYPTO_MAX_ALG_NAME)
 332                         goto err_free_inst;
 333
 334                 err = crypto_grab_skcipher(spawn,
 335                                            skcipher_crypto_instance(inst),
 336                                            ecb_name, 0, mask);
 337         }
 338
 339         if (err)
 340                 goto err_free_inst;
 341
 342         alg = crypto_skcipher_spawn_alg(spawn);
 343
 344         err = -EINVAL;
 345         if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
 346                 goto err_free_inst;
 347
 348         if (crypto_skcipher_alg_ivsize(alg))
 349                 goto err_free_inst;
 350
 351         err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
 352                                   &alg->base);
 353         if (err)
 354                 goto err_free_inst;
 355
 356         err = -EINVAL;
 357         cipher_name = alg->base.cra_name;
 358
 359         /* Alas we screwed up the naming so we have to mangle the
 360          * cipher name.
 361          */
 362         if (!strncmp(cipher_name, "ecb(", 4)) {
 363                 unsigned len;
 364
 365                 len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
 366                 if (len < 2 || len >= sizeof(ecb_name))
 367                         goto err_free_inst;
 368
 369                 if (ecb_name[len - 1] != ')')
 370                         goto err_free_inst;
 371
 372                 ecb_name[len - 1] = 0;
 373
 374                 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 375                              "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
 376                         err = -ENAMETOOLONG;
 377                         goto err_free_inst;
 378                 }
 379         } else
 380                 goto err_free_inst;
 381
 382         inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
 383         inst->alg.base.cra_priority = alg->base.cra_priority;
 384         inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
 385         inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
 386                                        (__alignof__(be128) - 1);
 387
 388         inst->alg.ivsize = LRW_BLOCK_SIZE;
 389         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
 390                                 LRW_BLOCK_SIZE;
 391         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
 392                                 LRW_BLOCK_SIZE;
 393
 394         inst->alg.base.cra_ctxsize = sizeof(struct priv);
 395
 396         inst->alg.init = init_tfm;
 397         inst->alg.exit = exit_tfm;
 398
 399         inst->alg.setkey = setkey;
 400         inst->alg.encrypt = encrypt;
 401         inst->alg.decrypt = decrypt;
 402
 403         inst->free = crypto_lrw_free;
 404
 405         err = skcipher_register_instance(tmpl, inst);
 406         if (err) {
 407 err_free_inst:
 408                 crypto_lrw_free(inst);
 409         }
 410         return err;
 411 }
 412
 413 static struct crypto_template crypto_tmpl = {
 414         .name = "lrw",
 415         .create = create,
 416         .module = THIS_MODULE,
 417 };
 418
 419 static int __init crypto_module_init(void)
 420 {
 421         return crypto_register_template(&crypto_tmpl);
 422 }
 423
 424 static void __exit crypto_module_exit(void)
 425 {
 426         crypto_unregister_template(&crypto_tmpl);
 427 }
 428
 429 subsys_initcall(crypto_module_init);
 430 module_exit(crypto_module_exit);
 431
 432 MODULE_LICENSE("GPL");
 433 MODULE_DESCRIPTION("LRW block cipher mode");
 434 MODULE_ALIAS_CRYPTO("lrw");