1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* XTS: as defined in IEEE1619/D16 3 * http://grouper.ieee.org/groups/1619/email/pdf00086.pdf 4 * 5 * Copyright (c) 2007 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 #include <crypto/internal/skcipher.h> 11 #include <crypto/scatterwalk.h> 12 #include <linux/err.h> 13 #include <linux/init.h> 14 #include <linux/kernel.h> 15 #include <linux/module.h> 16 #include <linux/scatterlist.h> 17 #include <linux/slab.h> 18 19 #include <crypto/xts.h> 20 #include <crypto/b128ops.h> 21 #include <crypto/gf128mul.h> 22 23 struct priv { 24 struct crypto_skcipher *child; 25 struct crypto_cipher *tweak; 26 }; 27 28 struct xts_instance_ctx { 29 struct crypto_skcipher_spawn spawn; 30 char name[CRYPTO_MAX_ALG_NAME]; 31 }; 32 33 struct rctx { 34 le128 t; 35 struct scatterlist *tail; 36 struct scatterlist sg[2]; 37 struct skcipher_request subreq; 38 }; 39 40 static int setkey(struct crypto_skcipher *parent, const u8 *key, 41 unsigned int keylen) 42 { 43 struct priv *ctx = crypto_skcipher_ctx(parent); 44 struct crypto_skcipher *child; 45 struct crypto_cipher *tweak; 46 int err; 47 48 err = xts_verify_key(parent, key, keylen); 49 if (err) 50 return err; 51 52 keylen /= 2; 53 54 /* we need two cipher instances: one to compute the initial 'tweak' 55 * by encrypting the IV (usually the 'plain' iv) and the other 56 * one to encrypt and decrypt the data */ 57 58 /* tweak cipher, uses Key2 i.e. the second half of *key */ 59 tweak = ctx->tweak; 60 crypto_cipher_clear_flags(tweak, CRYPTO_TFM_REQ_MASK); 61 crypto_cipher_set_flags(tweak, crypto_skcipher_get_flags(parent) & 62 CRYPTO_TFM_REQ_MASK); 63 err = crypto_cipher_setkey(tweak, key + keylen, keylen); 64 if (err) 65 return err; 66 67 /* data cipher, uses Key1 i.e. the first half of *key */ 68 child = ctx->child; 69 crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK); 70 crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) & 71 CRYPTO_TFM_REQ_MASK); 72 return crypto_skcipher_setkey(child, key, keylen); 73 } 74 75 /* 76 * We compute the tweak masks twice (both before and after the ECB encryption or 77 * decryption) to avoid having to allocate a temporary buffer and/or make 78 * mutliple calls to the 'ecb(..)' instance, which usually would be slower than 79 * just doing the gf128mul_x_ble() calls again. 80 */ 81 static int xor_tweak(struct skcipher_request *req, bool second_pass, bool enc) 82 { 83 struct rctx *rctx = skcipher_request_ctx(req); 84 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); 85 const bool cts = (req->cryptlen % XTS_BLOCK_SIZE); 86 const int bs = XTS_BLOCK_SIZE; 87 struct skcipher_walk w; 88 le128 t = rctx->t; 89 int err; 90 91 if (second_pass) { 92 req = &rctx->subreq; 93 /* set to our TFM to enforce correct alignment: */ 94 skcipher_request_set_tfm(req, tfm); 95 } 96 err = skcipher_walk_virt(&w, req, false); 97 98 while (w.nbytes) { 99 unsigned int avail = w.nbytes; 100 le128 *wsrc; 101 le128 *wdst; 102 103 wsrc = w.src.virt.addr; 104 wdst = w.dst.virt.addr; 105 106 do { 107 if (unlikely(cts) && 108 w.total - w.nbytes + avail < 2 * XTS_BLOCK_SIZE) { 109 if (!enc) { 110 if (second_pass) 111 rctx->t = t; 112 gf128mul_x_ble(&t, &t); 113 } 114 le128_xor(wdst, &t, wsrc); 115 if (enc && second_pass) 116 gf128mul_x_ble(&rctx->t, &t); 117 skcipher_walk_done(&w, avail - bs); 118 return 0; 119 } 120 121 le128_xor(wdst++, &t, wsrc++); 122 gf128mul_x_ble(&t, &t); 123 } while ((avail -= bs) >= bs); 124 125 err = skcipher_walk_done(&w, avail); 126 } 127 128 return err; 129 } 130 131 static int xor_tweak_pre(struct skcipher_request *req, bool enc) 132 { 133 return xor_tweak(req, false, enc); 134 } 135 136 static int xor_tweak_post(struct skcipher_request *req, bool enc) 137 { 138 return xor_tweak(req, true, enc); 139 } 140 141 static void cts_done(struct crypto_async_request *areq, int err) 142 { 143 struct skcipher_request *req = areq->data; 144 le128 b; 145 146 if (!err) { 147 struct rctx *rctx = skcipher_request_ctx(req); 148 149 scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 0); 150 le128_xor(&b, &rctx->t, &b); 151 scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 1); 152 } 153 154 skcipher_request_complete(req, err); 155 } 156 157 static int cts_final(struct skcipher_request *req, 158 int (*crypt)(struct skcipher_request *req)) 159 { 160 struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req)); 161 int offset = req->cryptlen & ~(XTS_BLOCK_SIZE - 1); 162 struct rctx *rctx = skcipher_request_ctx(req); 163 struct skcipher_request *subreq = &rctx->subreq; 164 int tail = req->cryptlen % XTS_BLOCK_SIZE; 165 le128 b[2]; 166 int err; 167 168 rctx->tail = scatterwalk_ffwd(rctx->sg, req->dst, 169 offset - XTS_BLOCK_SIZE); 170 171 scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0); 172 memcpy(b + 1, b, tail); 173 scatterwalk_map_and_copy(b, req->src, offset, tail, 0); 174 175 le128_xor(b, &rctx->t, b); 176 177 scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE + tail, 1); 178 179 skcipher_request_set_tfm(subreq, ctx->child); 180 skcipher_request_set_callback(subreq, req->base.flags, cts_done, req); 181 skcipher_request_set_crypt(subreq, rctx->tail, rctx->tail, 182 XTS_BLOCK_SIZE, NULL); 183 184 err = crypt(subreq); 185 if (err) 186 return err; 187 188 scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0); 189 le128_xor(b, &rctx->t, b); 190 scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 1); 191 192 return 0; 193 } 194 195 static void encrypt_done(struct crypto_async_request *areq, int err) 196 { 197 struct skcipher_request *req = areq->data; 198 199 if (!err) { 200 struct rctx *rctx = skcipher_request_ctx(req); 201 202 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP; 203 err = xor_tweak_post(req, true); 204 205 if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) { 206 err = cts_final(req, crypto_skcipher_encrypt); 207 if (err == -EINPROGRESS) 208 return; 209 } 210 } 211 212 skcipher_request_complete(req, err); 213 } 214 215 static void decrypt_done(struct crypto_async_request *areq, int err) 216 { 217 struct skcipher_request *req = areq->data; 218 219 if (!err) { 220 struct rctx *rctx = skcipher_request_ctx(req); 221 222 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP; 223 err = xor_tweak_post(req, false); 224 225 if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) { 226 err = cts_final(req, crypto_skcipher_decrypt); 227 if (err == -EINPROGRESS) 228 return; 229 } 230 } 231 232 skcipher_request_complete(req, err); 233 } 234 235 static int init_crypt(struct skcipher_request *req, crypto_completion_t compl) 236 { 237 struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req)); 238 struct rctx *rctx = skcipher_request_ctx(req); 239 struct skcipher_request *subreq = &rctx->subreq; 240 241 if (req->cryptlen < XTS_BLOCK_SIZE) 242 return -EINVAL; 243 244 skcipher_request_set_tfm(subreq, ctx->child); 245 skcipher_request_set_callback(subreq, req->base.flags, compl, req); 246 skcipher_request_set_crypt(subreq, req->dst, req->dst, 247 req->cryptlen & ~(XTS_BLOCK_SIZE - 1), NULL); 248 249 /* calculate first value of T */ 250 crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv); 251 252 return 0; 253 } 254 255 static int encrypt(struct skcipher_request *req) 256 { 257 struct rctx *rctx = skcipher_request_ctx(req); 258 struct skcipher_request *subreq = &rctx->subreq; 259 int err; 260 261 err = init_crypt(req, encrypt_done) ?: 262 xor_tweak_pre(req, true) ?: 263 crypto_skcipher_encrypt(subreq) ?: 264 xor_tweak_post(req, true); 265 266 if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0)) 267 return err; 268 269 return cts_final(req, crypto_skcipher_encrypt); 270 } 271 272 static int decrypt(struct skcipher_request *req) 273 { 274 struct rctx *rctx = skcipher_request_ctx(req); 275 struct skcipher_request *subreq = &rctx->subreq; 276 int err; 277 278 err = init_crypt(req, decrypt_done) ?: 279 xor_tweak_pre(req, false) ?: 280 crypto_skcipher_decrypt(subreq) ?: 281 xor_tweak_post(req, false); 282 283 if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0)) 284 return err; 285 286 return cts_final(req, crypto_skcipher_decrypt); 287 } 288 289 static int init_tfm(struct crypto_skcipher *tfm) 290 { 291 struct skcipher_instance *inst = skcipher_alg_instance(tfm); 292 struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst); 293 struct priv *ctx = crypto_skcipher_ctx(tfm); 294 struct crypto_skcipher *child; 295 struct crypto_cipher *tweak; 296 297 child = crypto_spawn_skcipher(&ictx->spawn); 298 if (IS_ERR(child)) 299 return PTR_ERR(child); 300 301 ctx->child = child; 302 303 tweak = crypto_alloc_cipher(ictx->name, 0, 0); 304 if (IS_ERR(tweak)) { 305 crypto_free_skcipher(ctx->child); 306 return PTR_ERR(tweak); 307 } 308 309 ctx->tweak = tweak; 310 311 crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) + 312 sizeof(struct rctx)); 313 314 return 0; 315 } 316 317 static void exit_tfm(struct crypto_skcipher *tfm) 318 { 319 struct priv *ctx = crypto_skcipher_ctx(tfm); 320 321 crypto_free_skcipher(ctx->child); 322 crypto_free_cipher(ctx->tweak); 323 } 324 325 static void free(struct skcipher_instance *inst) 326 { 327 crypto_drop_skcipher(skcipher_instance_ctx(inst)); 328 kfree(inst); 329 } 330 331 static int create(struct crypto_template *tmpl, struct rtattr **tb) 332 { 333 struct skcipher_instance *inst; 334 struct crypto_attr_type *algt; 335 struct xts_instance_ctx *ctx; 336 struct skcipher_alg *alg; 337 const char *cipher_name; 338 u32 mask; 339 int err; 340 341 algt = crypto_get_attr_type(tb); 342 if (IS_ERR(algt)) 343 return PTR_ERR(algt); 344 345 if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask) 346 return -EINVAL; 347 348 cipher_name = crypto_attr_alg_name(tb[1]); 349 if (IS_ERR(cipher_name)) 350 return PTR_ERR(cipher_name); 351 352 inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL); 353 if (!inst) 354 return -ENOMEM; 355 356 ctx = skcipher_instance_ctx(inst); 357 358 mask = crypto_requires_off(algt->type, algt->mask, 359 CRYPTO_ALG_NEED_FALLBACK | 360 CRYPTO_ALG_ASYNC); 361 362 err = crypto_grab_skcipher(&ctx->spawn, skcipher_crypto_instance(inst), 363 cipher_name, 0, mask); 364 if (err == -ENOENT) { 365 err = -ENAMETOOLONG; 366 if (snprintf(ctx->name, CRYPTO_MAX_ALG_NAME, "ecb(%s)", 367 cipher_name) >= CRYPTO_MAX_ALG_NAME) 368 goto err_free_inst; 369 370 err = crypto_grab_skcipher(&ctx->spawn, 371 skcipher_crypto_instance(inst), 372 ctx->name, 0, mask); 373 } 374 375 if (err) 376 goto err_free_inst; 377 378 alg = crypto_skcipher_spawn_alg(&ctx->spawn); 379 380 err = -EINVAL; 381 if (alg->base.cra_blocksize != XTS_BLOCK_SIZE) 382 goto err_drop_spawn; 383 384 if (crypto_skcipher_alg_ivsize(alg)) 385 goto err_drop_spawn; 386 387 err = crypto_inst_setname(skcipher_crypto_instance(inst), "xts", 388 &alg->base); 389 if (err) 390 goto err_drop_spawn; 391 392 err = -EINVAL; 393 cipher_name = alg->base.cra_name; 394 395 /* Alas we screwed up the naming so we have to mangle the 396 * cipher name. 397 */ 398 if (!strncmp(cipher_name, "ecb(", 4)) { 399 unsigned len; 400 401 len = strlcpy(ctx->name, cipher_name + 4, sizeof(ctx->name)); 402 if (len < 2 || len >= sizeof(ctx->name)) 403 goto err_drop_spawn; 404 405 if (ctx->name[len - 1] != ')') 406 goto err_drop_spawn; 407 408 ctx->name[len - 1] = 0; 409 410 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME, 411 "xts(%s)", ctx->name) >= CRYPTO_MAX_ALG_NAME) { 412 err = -ENAMETOOLONG; 413 goto err_drop_spawn; 414 } 415 } else 416 goto err_drop_spawn; 417 418 inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC; 419 inst->alg.base.cra_priority = alg->base.cra_priority; 420 inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE; 421 inst->alg.base.cra_alignmask = alg->base.cra_alignmask | 422 (__alignof__(u64) - 1); 423 424 inst->alg.ivsize = XTS_BLOCK_SIZE; 425 inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) * 2; 426 inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2; 427 428 inst->alg.base.cra_ctxsize = sizeof(struct priv); 429 430 inst->alg.init = init_tfm; 431 inst->alg.exit = exit_tfm; 432 433 inst->alg.setkey = setkey; 434 inst->alg.encrypt = encrypt; 435 inst->alg.decrypt = decrypt; 436 437 inst->free = free; 438 439 err = skcipher_register_instance(tmpl, inst); 440 if (err) 441 goto err_drop_spawn; 442 443 out: 444 return err; 445 446 err_drop_spawn: 447 crypto_drop_skcipher(&ctx->spawn); 448 err_free_inst: 449 kfree(inst); 450 goto out; 451 } 452 453 static struct crypto_template crypto_tmpl = { 454 .name = "xts", 455 .create = create, 456 .module = THIS_MODULE, 457 }; 458 459 static int __init crypto_module_init(void) 460 { 461 return crypto_register_template(&crypto_tmpl); 462 } 463 464 static void __exit crypto_module_exit(void) 465 { 466 crypto_unregister_template(&crypto_tmpl); 467 } 468 469 subsys_initcall(crypto_module_init); 470 module_exit(crypto_module_exit); 471 472 MODULE_LICENSE("GPL"); 473 MODULE_DESCRIPTION("XTS block cipher mode"); 474 MODULE_ALIAS_CRYPTO("xts"); 475