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         crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
  83                                           CRYPTO_TFM_RES_MASK);
  84         if (err)
  85                 return err;
  86
  87         if (ctx->table)
  88                 gf128mul_free_64k(ctx->table);
  89
  90         /* initialize multiplication table for Key2 */
  91         ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
  92         if (!ctx->table)
  93                 return -ENOMEM;
  94
  95         /* initialize optimization table */
  96         for (i = 0; i < 128; i++) {
  97                 setbit128_bbe(&tmp, i);
  98                 ctx->mulinc[i] = tmp;
  99                 gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
 100         }
 101
 102         return 0;
 103 }
 104
 105 /*
 106  * Returns the number of trailing '1' bits in the words of the counter, which is
 107  * represented by 4 32-bit words, arranged from least to most significant.
 108  * At the same time, increments the counter by one.
 109  *
 110  * For example:
 111  *
 112  * u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
 113  * int i = next_index(&counter);
 114  * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
 115  */
 116 static int next_index(u32 *counter)
 117 {
 118         int i, res = 0;
 119
 120         for (i = 0; i < 4; i++) {
 121                 if (counter[i] + 1 != 0)
 122                         return res + ffz(counter[i]++);
 123
 124                 counter[i] = 0;
 125                 res += 32;
 126         }
 127
 128         /*
 129          * If we get here, then x == 128 and we are incrementing the counter
 130          * from all ones to all zeros. This means we must return index 127, i.e.
 131          * the one corresponding to key2*{ 1,...,1 }.
 132          */
 133         return 127;
 134 }
 135
 136 /*
 137  * We compute the tweak masks twice (both before and after the ECB encryption or
 138  * decryption) to avoid having to allocate a temporary buffer and/or make
 139  * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
 140  * just doing the next_index() calls again.
 141  */
 142 static int xor_tweak(struct skcipher_request *req, bool second_pass)
 143 {
 144         const int bs = LRW_BLOCK_SIZE;
 145         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 146         struct priv *ctx = crypto_skcipher_ctx(tfm);
 147         struct rctx *rctx = skcipher_request_ctx(req);
 148         be128 t = rctx->t;
 149         struct skcipher_walk w;
 150         __be32 *iv;
 151         u32 counter[4];
 152         int err;
 153
 154         if (second_pass) {
 155                 req = &rctx->subreq;
 156                 /* set to our TFM to enforce correct alignment: */
 157                 skcipher_request_set_tfm(req, tfm);
 158         }
 159
 160         err = skcipher_walk_virt(&w, req, false);
 161         if (err)
 162                 return err;
 163
 164         iv = (__be32 *)w.iv;
 165         counter[0] = be32_to_cpu(iv[3]);
 166         counter[1] = be32_to_cpu(iv[2]);
 167         counter[2] = be32_to_cpu(iv[1]);
 168         counter[3] = be32_to_cpu(iv[0]);
 169
 170         while (w.nbytes) {
 171                 unsigned int avail = w.nbytes;
 172                 be128 *wsrc;
 173                 be128 *wdst;
 174
 175                 wsrc = w.src.virt.addr;
 176                 wdst = w.dst.virt.addr;
 177
 178                 do {
 179                         be128_xor(wdst++, &t, wsrc++);
 180
 181                         /* T <- I*Key2, using the optimization
 182                          * discussed in the specification */
 183                         be128_xor(&t, &t, &ctx->mulinc[next_index(counter)]);
 184                 } while ((avail -= bs) >= bs);
 185
 186                 if (second_pass && w.nbytes == w.total) {
 187                         iv[0] = cpu_to_be32(counter[3]);
 188                         iv[1] = cpu_to_be32(counter[2]);
 189                         iv[2] = cpu_to_be32(counter[1]);
 190                         iv[3] = cpu_to_be32(counter[0]);
 191                 }
 192
 193                 err = skcipher_walk_done(&w, avail);
 194         }
 195
 196         return err;
 197 }
 198
 199 static int xor_tweak_pre(struct skcipher_request *req)
 200 {
 201         return xor_tweak(req, false);
 202 }
 203
 204 static int xor_tweak_post(struct skcipher_request *req)
 205 {
 206         return xor_tweak(req, true);
 207 }
 208
 209 static void crypt_done(struct crypto_async_request *areq, int err)
 210 {
 211         struct skcipher_request *req = areq->data;
 212
 213         if (!err) {
 214                 struct rctx *rctx = skcipher_request_ctx(req);
 215
 216                 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
 217                 err = xor_tweak_post(req);
 218         }
 219
 220         skcipher_request_complete(req, err);
 221 }
 222
 223 static void init_crypt(struct skcipher_request *req)
 224 {
 225         struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
 226         struct rctx *rctx = skcipher_request_ctx(req);
 227         struct skcipher_request *subreq = &rctx->subreq;
 228
 229         skcipher_request_set_tfm(subreq, ctx->child);
 230         skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req);
 231         /* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
 232         skcipher_request_set_crypt(subreq, req->dst, req->dst,
 233                                    req->cryptlen, req->iv);
 234
 235         /* calculate first value of T */
 236         memcpy(&rctx->t, req->iv, sizeof(rctx->t));
 237
 238         /* T <- I*Key2 */
 239         gf128mul_64k_bbe(&rctx->t, ctx->table);
 240 }
 241
 242 static int encrypt(struct skcipher_request *req)
 243 {
 244         struct rctx *rctx = skcipher_request_ctx(req);
 245         struct skcipher_request *subreq = &rctx->subreq;
 246
 247         init_crypt(req);
 248         return xor_tweak_pre(req) ?:
 249                 crypto_skcipher_encrypt(subreq) ?:
 250                 xor_tweak_post(req);
 251 }
 252
 253 static int decrypt(struct skcipher_request *req)
 254 {
 255         struct rctx *rctx = skcipher_request_ctx(req);
 256         struct skcipher_request *subreq = &rctx->subreq;
 257
 258         init_crypt(req);
 259         return xor_tweak_pre(req) ?:
 260                 crypto_skcipher_decrypt(subreq) ?:
 261                 xor_tweak_post(req);
 262 }
 263
 264 static int init_tfm(struct crypto_skcipher *tfm)
 265 {
 266         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 267         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 268         struct priv *ctx = crypto_skcipher_ctx(tfm);
 269         struct crypto_skcipher *cipher;
 270
 271         cipher = crypto_spawn_skcipher(spawn);
 272         if (IS_ERR(cipher))
 273                 return PTR_ERR(cipher);
 274
 275         ctx->child = cipher;
 276
 277         crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
 278                                          sizeof(struct rctx));
 279
 280         return 0;
 281 }
 282
 283 static void exit_tfm(struct crypto_skcipher *tfm)
 284 {
 285         struct priv *ctx = crypto_skcipher_ctx(tfm);
 286
 287         if (ctx->table)
 288                 gf128mul_free_64k(ctx->table);
 289         crypto_free_skcipher(ctx->child);
 290 }
 291
 292 static void free(struct skcipher_instance *inst)
 293 {
 294         crypto_drop_skcipher(skcipher_instance_ctx(inst));
 295         kfree(inst);
 296 }
 297
 298 static int create(struct crypto_template *tmpl, struct rtattr **tb)
 299 {
 300         struct crypto_skcipher_spawn *spawn;
 301         struct skcipher_instance *inst;
 302         struct crypto_attr_type *algt;
 303         struct skcipher_alg *alg;
 304         const char *cipher_name;
 305         char ecb_name[CRYPTO_MAX_ALG_NAME];
 306         int err;
 307
 308         algt = crypto_get_attr_type(tb);
 309         if (IS_ERR(algt))
 310                 return PTR_ERR(algt);
 311
 312         if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 313                 return -EINVAL;
 314
 315         cipher_name = crypto_attr_alg_name(tb[1]);
 316         if (IS_ERR(cipher_name))
 317                 return PTR_ERR(cipher_name);
 318
 319         inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
 320         if (!inst)
 321                 return -ENOMEM;
 322
 323         spawn = skcipher_instance_ctx(inst);
 324
 325         crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
 326         err = crypto_grab_skcipher(spawn, cipher_name, 0,
 327                                    crypto_requires_sync(algt->type,
 328                                                         algt->mask));
 329         if (err == -ENOENT) {
 330                 err = -ENAMETOOLONG;
 331                 if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
 332                              cipher_name) >= CRYPTO_MAX_ALG_NAME)
 333                         goto err_free_inst;
 334
 335                 err = crypto_grab_skcipher(spawn, ecb_name, 0,
 336                                            crypto_requires_sync(algt->type,
 337                                                                 algt->mask));
 338         }
 339
 340         if (err)
 341                 goto err_free_inst;
 342
 343         alg = crypto_skcipher_spawn_alg(spawn);
 344
 345         err = -EINVAL;
 346         if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
 347                 goto err_drop_spawn;
 348
 349         if (crypto_skcipher_alg_ivsize(alg))
 350                 goto err_drop_spawn;
 351
 352         err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
 353                                   &alg->base);
 354         if (err)
 355                 goto err_drop_spawn;
 356
 357         err = -EINVAL;
 358         cipher_name = alg->base.cra_name;
 359
 360         /* Alas we screwed up the naming so we have to mangle the
 361          * cipher name.
 362          */
 363         if (!strncmp(cipher_name, "ecb(", 4)) {
 364                 unsigned len;
 365
 366                 len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
 367                 if (len < 2 || len >= sizeof(ecb_name))
 368                         goto err_drop_spawn;
 369
 370                 if (ecb_name[len - 1] != ')')
 371                         goto err_drop_spawn;
 372
 373                 ecb_name[len - 1] = 0;
 374
 375                 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 376                              "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
 377                         err = -ENAMETOOLONG;
 378                         goto err_drop_spawn;
 379                 }
 380         } else
 381                 goto err_drop_spawn;
 382
 383         inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
 384         inst->alg.base.cra_priority = alg->base.cra_priority;
 385         inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
 386         inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
 387                                        (__alignof__(be128) - 1);
 388
 389         inst->alg.ivsize = LRW_BLOCK_SIZE;
 390         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
 391                                 LRW_BLOCK_SIZE;
 392         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
 393                                 LRW_BLOCK_SIZE;
 394
 395         inst->alg.base.cra_ctxsize = sizeof(struct priv);
 396
 397         inst->alg.init = init_tfm;
 398         inst->alg.exit = exit_tfm;
 399
 400         inst->alg.setkey = setkey;
 401         inst->alg.encrypt = encrypt;
 402         inst->alg.decrypt = decrypt;
 403
 404         inst->free = free;
 405
 406         err = skcipher_register_instance(tmpl, inst);
 407         if (err)
 408                 goto err_drop_spawn;
 409
 410 out:
 411         return err;
 412
 413 err_drop_spawn:
 414         crypto_drop_skcipher(spawn);
 415 err_free_inst:
 416         kfree(inst);
 417         goto out;
 418 }
 419
 420 static struct crypto_template crypto_tmpl = {
 421         .name = "lrw",
 422         .create = create,
 423         .module = THIS_MODULE,
 424 };
 425
 426 static int __init crypto_module_init(void)
 427 {
 428         return crypto_register_template(&crypto_tmpl);
 429 }
 430
 431 static void __exit crypto_module_exit(void)
 432 {
 433         crypto_unregister_template(&crypto_tmpl);
 434 }
 435
 436 subsys_initcall(crypto_module_init);
 437 module_exit(crypto_module_exit);
 438
 439 MODULE_LICENSE("GPL");
 440 MODULE_DESCRIPTION("LRW block cipher mode");
 441 MODULE_ALIAS_CRYPTO("lrw");