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 if (err) 166 return err; 167 168 iv = (__be32 *)w.iv; 169 counter[0] = be32_to_cpu(iv[3]); 170 counter[1] = be32_to_cpu(iv[2]); 171 counter[2] = be32_to_cpu(iv[1]); 172 counter[3] = be32_to_cpu(iv[0]); 173 174 while (w.nbytes) { 175 unsigned int avail = w.nbytes; 176 be128 *wsrc; 177 be128 *wdst; 178 179 wsrc = w.src.virt.addr; 180 wdst = w.dst.virt.addr; 181 182 do { 183 be128_xor(wdst++, &t, wsrc++); 184 185 /* T <- I*Key2, using the optimization 186 * discussed in the specification */ 187 be128_xor(&t, &t, &ctx->mulinc[next_index(counter)]); 188 } while ((avail -= bs) >= bs); 189 190 if (second_pass && w.nbytes == w.total) { 191 iv[0] = cpu_to_be32(counter[3]); 192 iv[1] = cpu_to_be32(counter[2]); 193 iv[2] = cpu_to_be32(counter[1]); 194 iv[3] = cpu_to_be32(counter[0]); 195 } 196 197 err = skcipher_walk_done(&w, avail); 198 } 199 200 return err; 201 } 202 203 static int xor_tweak_pre(struct skcipher_request *req) 204 { 205 return xor_tweak(req, false); 206 } 207 208 static int xor_tweak_post(struct skcipher_request *req) 209 { 210 return xor_tweak(req, true); 211 } 212 213 static void crypt_done(struct crypto_async_request *areq, int err) 214 { 215 struct skcipher_request *req = areq->data; 216 217 if (!err) { 218 struct rctx *rctx = skcipher_request_ctx(req); 219 220 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP; 221 err = xor_tweak_post(req); 222 } 223 224 skcipher_request_complete(req, err); 225 } 226 227 static void init_crypt(struct skcipher_request *req) 228 { 229 struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req)); 230 struct rctx *rctx = skcipher_request_ctx(req); 231 struct skcipher_request *subreq = &rctx->subreq; 232 233 skcipher_request_set_tfm(subreq, ctx->child); 234 skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req); 235 /* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */ 236 skcipher_request_set_crypt(subreq, req->dst, req->dst, 237 req->cryptlen, req->iv); 238 239 /* calculate first value of T */ 240 memcpy(&rctx->t, req->iv, sizeof(rctx->t)); 241 242 /* T <- I*Key2 */ 243 gf128mul_64k_bbe(&rctx->t, ctx->table); 244 } 245 246 static int encrypt(struct skcipher_request *req) 247 { 248 struct rctx *rctx = skcipher_request_ctx(req); 249 struct skcipher_request *subreq = &rctx->subreq; 250 251 init_crypt(req); 252 return xor_tweak_pre(req) ?: 253 crypto_skcipher_encrypt(subreq) ?: 254 xor_tweak_post(req); 255 } 256 257 static int decrypt(struct skcipher_request *req) 258 { 259 struct rctx *rctx = skcipher_request_ctx(req); 260 struct skcipher_request *subreq = &rctx->subreq; 261 262 init_crypt(req); 263 return xor_tweak_pre(req) ?: 264 crypto_skcipher_decrypt(subreq) ?: 265 xor_tweak_post(req); 266 } 267 268 static int init_tfm(struct crypto_skcipher *tfm) 269 { 270 struct skcipher_instance *inst = skcipher_alg_instance(tfm); 271 struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst); 272 struct priv *ctx = crypto_skcipher_ctx(tfm); 273 struct crypto_skcipher *cipher; 274 275 cipher = crypto_spawn_skcipher(spawn); 276 if (IS_ERR(cipher)) 277 return PTR_ERR(cipher); 278 279 ctx->child = cipher; 280 281 crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) + 282 sizeof(struct rctx)); 283 284 return 0; 285 } 286 287 static void exit_tfm(struct crypto_skcipher *tfm) 288 { 289 struct priv *ctx = crypto_skcipher_ctx(tfm); 290 291 if (ctx->table) 292 gf128mul_free_64k(ctx->table); 293 crypto_free_skcipher(ctx->child); 294 } 295 296 static void free(struct skcipher_instance *inst) 297 { 298 crypto_drop_skcipher(skcipher_instance_ctx(inst)); 299 kfree(inst); 300 } 301 302 static int create(struct crypto_template *tmpl, struct rtattr **tb) 303 { 304 struct crypto_skcipher_spawn *spawn; 305 struct skcipher_instance *inst; 306 struct crypto_attr_type *algt; 307 struct skcipher_alg *alg; 308 const char *cipher_name; 309 char ecb_name[CRYPTO_MAX_ALG_NAME]; 310 int err; 311 312 algt = crypto_get_attr_type(tb); 313 if (IS_ERR(algt)) 314 return PTR_ERR(algt); 315 316 if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask) 317 return -EINVAL; 318 319 cipher_name = crypto_attr_alg_name(tb[1]); 320 if (IS_ERR(cipher_name)) 321 return PTR_ERR(cipher_name); 322 323 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL); 324 if (!inst) 325 return -ENOMEM; 326 327 spawn = skcipher_instance_ctx(inst); 328 329 crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst)); 330 err = crypto_grab_skcipher(spawn, cipher_name, 0, 331 crypto_requires_sync(algt->type, 332 algt->mask)); 333 if (err == -ENOENT) { 334 err = -ENAMETOOLONG; 335 if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)", 336 cipher_name) >= CRYPTO_MAX_ALG_NAME) 337 goto err_free_inst; 338 339 err = crypto_grab_skcipher(spawn, ecb_name, 0, 340 crypto_requires_sync(algt->type, 341 algt->mask)); 342 } 343 344 if (err) 345 goto err_free_inst; 346 347 alg = crypto_skcipher_spawn_alg(spawn); 348 349 err = -EINVAL; 350 if (alg->base.cra_blocksize != LRW_BLOCK_SIZE) 351 goto err_drop_spawn; 352 353 if (crypto_skcipher_alg_ivsize(alg)) 354 goto err_drop_spawn; 355 356 err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw", 357 &alg->base); 358 if (err) 359 goto err_drop_spawn; 360 361 err = -EINVAL; 362 cipher_name = alg->base.cra_name; 363 364 /* Alas we screwed up the naming so we have to mangle the 365 * cipher name. 366 */ 367 if (!strncmp(cipher_name, "ecb(", 4)) { 368 unsigned len; 369 370 len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name)); 371 if (len < 2 || len >= sizeof(ecb_name)) 372 goto err_drop_spawn; 373 374 if (ecb_name[len - 1] != ')') 375 goto err_drop_spawn; 376 377 ecb_name[len - 1] = 0; 378 379 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME, 380 "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) { 381 err = -ENAMETOOLONG; 382 goto err_drop_spawn; 383 } 384 } else 385 goto err_drop_spawn; 386 387 inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC; 388 inst->alg.base.cra_priority = alg->base.cra_priority; 389 inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE; 390 inst->alg.base.cra_alignmask = alg->base.cra_alignmask | 391 (__alignof__(__be32) - 1); 392 393 inst->alg.ivsize = LRW_BLOCK_SIZE; 394 inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) + 395 LRW_BLOCK_SIZE; 396 inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) + 397 LRW_BLOCK_SIZE; 398 399 inst->alg.base.cra_ctxsize = sizeof(struct priv); 400 401 inst->alg.init = init_tfm; 402 inst->alg.exit = exit_tfm; 403 404 inst->alg.setkey = setkey; 405 inst->alg.encrypt = encrypt; 406 inst->alg.decrypt = decrypt; 407 408 inst->free = free; 409 410 err = skcipher_register_instance(tmpl, inst); 411 if (err) 412 goto err_drop_spawn; 413 414 out: 415 return err; 416 417 err_drop_spawn: 418 crypto_drop_skcipher(spawn); 419 err_free_inst: 420 kfree(inst); 421 goto out; 422 } 423 424 static struct crypto_template crypto_tmpl = { 425 .name = "lrw", 426 .create = create, 427 .module = THIS_MODULE, 428 }; 429 430 static int __init crypto_module_init(void) 431 { 432 return crypto_register_template(&crypto_tmpl); 433 } 434 435 static void __exit crypto_module_exit(void) 436 { 437 crypto_unregister_template(&crypto_tmpl); 438 } 439 440 subsys_initcall(crypto_module_init); 441 module_exit(crypto_module_exit); 442 443 MODULE_LICENSE("GPL"); 444 MODULE_DESCRIPTION("LRW block cipher mode"); 445 MODULE_ALIAS_CRYPTO("lrw"); 446