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 err = xor_tweak_post(req); 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__(__be32) - 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 module_init(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"); 442