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 xts_tfm_ctx { 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 xts_request_ctx { 34 le128 t; 35 struct scatterlist *tail; 36 struct scatterlist sg[2]; 37 struct skcipher_request subreq; 38 }; 39 40 static int xts_setkey(struct crypto_skcipher *parent, const u8 *key, 41 unsigned int keylen) 42 { 43 struct xts_tfm_ctx *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 xts_xor_tweak(struct skcipher_request *req, bool second_pass, 82 bool enc) 83 { 84 struct xts_request_ctx *rctx = skcipher_request_ctx(req); 85 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req); 86 const bool cts = (req->cryptlen % XTS_BLOCK_SIZE); 87 const int bs = XTS_BLOCK_SIZE; 88 struct skcipher_walk w; 89 le128 t = rctx->t; 90 int err; 91 92 if (second_pass) { 93 req = &rctx->subreq; 94 /* set to our TFM to enforce correct alignment: */ 95 skcipher_request_set_tfm(req, tfm); 96 } 97 err = skcipher_walk_virt(&w, req, false); 98 99 while (w.nbytes) { 100 unsigned int avail = w.nbytes; 101 le128 *wsrc; 102 le128 *wdst; 103 104 wsrc = w.src.virt.addr; 105 wdst = w.dst.virt.addr; 106 107 do { 108 if (unlikely(cts) && 109 w.total - w.nbytes + avail < 2 * XTS_BLOCK_SIZE) { 110 if (!enc) { 111 if (second_pass) 112 rctx->t = t; 113 gf128mul_x_ble(&t, &t); 114 } 115 le128_xor(wdst, &t, wsrc); 116 if (enc && second_pass) 117 gf128mul_x_ble(&rctx->t, &t); 118 skcipher_walk_done(&w, avail - bs); 119 return 0; 120 } 121 122 le128_xor(wdst++, &t, wsrc++); 123 gf128mul_x_ble(&t, &t); 124 } while ((avail -= bs) >= bs); 125 126 err = skcipher_walk_done(&w, avail); 127 } 128 129 return err; 130 } 131 132 static int xts_xor_tweak_pre(struct skcipher_request *req, bool enc) 133 { 134 return xts_xor_tweak(req, false, enc); 135 } 136 137 static int xts_xor_tweak_post(struct skcipher_request *req, bool enc) 138 { 139 return xts_xor_tweak(req, true, enc); 140 } 141 142 static void xts_cts_done(struct crypto_async_request *areq, int err) 143 { 144 struct skcipher_request *req = areq->data; 145 le128 b; 146 147 if (!err) { 148 struct xts_request_ctx *rctx = skcipher_request_ctx(req); 149 150 scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 0); 151 le128_xor(&b, &rctx->t, &b); 152 scatterwalk_map_and_copy(&b, rctx->tail, 0, XTS_BLOCK_SIZE, 1); 153 } 154 155 skcipher_request_complete(req, err); 156 } 157 158 static int xts_cts_final(struct skcipher_request *req, 159 int (*crypt)(struct skcipher_request *req)) 160 { 161 const struct xts_tfm_ctx *ctx = 162 crypto_skcipher_ctx(crypto_skcipher_reqtfm(req)); 163 int offset = req->cryptlen & ~(XTS_BLOCK_SIZE - 1); 164 struct xts_request_ctx *rctx = skcipher_request_ctx(req); 165 struct skcipher_request *subreq = &rctx->subreq; 166 int tail = req->cryptlen % XTS_BLOCK_SIZE; 167 le128 b[2]; 168 int err; 169 170 rctx->tail = scatterwalk_ffwd(rctx->sg, req->dst, 171 offset - XTS_BLOCK_SIZE); 172 173 scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0); 174 b[1] = b[0]; 175 scatterwalk_map_and_copy(b, req->src, offset, tail, 0); 176 177 le128_xor(b, &rctx->t, b); 178 179 scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE + tail, 1); 180 181 skcipher_request_set_tfm(subreq, ctx->child); 182 skcipher_request_set_callback(subreq, req->base.flags, xts_cts_done, 183 req); 184 skcipher_request_set_crypt(subreq, rctx->tail, rctx->tail, 185 XTS_BLOCK_SIZE, NULL); 186 187 err = crypt(subreq); 188 if (err) 189 return err; 190 191 scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 0); 192 le128_xor(b, &rctx->t, b); 193 scatterwalk_map_and_copy(b, rctx->tail, 0, XTS_BLOCK_SIZE, 1); 194 195 return 0; 196 } 197 198 static void xts_encrypt_done(struct crypto_async_request *areq, int err) 199 { 200 struct skcipher_request *req = areq->data; 201 202 if (!err) { 203 struct xts_request_ctx *rctx = skcipher_request_ctx(req); 204 205 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP; 206 err = xts_xor_tweak_post(req, true); 207 208 if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) { 209 err = xts_cts_final(req, crypto_skcipher_encrypt); 210 if (err == -EINPROGRESS) 211 return; 212 } 213 } 214 215 skcipher_request_complete(req, err); 216 } 217 218 static void xts_decrypt_done(struct crypto_async_request *areq, int err) 219 { 220 struct skcipher_request *req = areq->data; 221 222 if (!err) { 223 struct xts_request_ctx *rctx = skcipher_request_ctx(req); 224 225 rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP; 226 err = xts_xor_tweak_post(req, false); 227 228 if (!err && unlikely(req->cryptlen % XTS_BLOCK_SIZE)) { 229 err = xts_cts_final(req, crypto_skcipher_decrypt); 230 if (err == -EINPROGRESS) 231 return; 232 } 233 } 234 235 skcipher_request_complete(req, err); 236 } 237 238 static int xts_init_crypt(struct skcipher_request *req, 239 crypto_completion_t compl) 240 { 241 const struct xts_tfm_ctx *ctx = 242 crypto_skcipher_ctx(crypto_skcipher_reqtfm(req)); 243 struct xts_request_ctx *rctx = skcipher_request_ctx(req); 244 struct skcipher_request *subreq = &rctx->subreq; 245 246 if (req->cryptlen < XTS_BLOCK_SIZE) 247 return -EINVAL; 248 249 skcipher_request_set_tfm(subreq, ctx->child); 250 skcipher_request_set_callback(subreq, req->base.flags, compl, req); 251 skcipher_request_set_crypt(subreq, req->dst, req->dst, 252 req->cryptlen & ~(XTS_BLOCK_SIZE - 1), NULL); 253 254 /* calculate first value of T */ 255 crypto_cipher_encrypt_one(ctx->tweak, (u8 *)&rctx->t, req->iv); 256 257 return 0; 258 } 259 260 static int xts_encrypt(struct skcipher_request *req) 261 { 262 struct xts_request_ctx *rctx = skcipher_request_ctx(req); 263 struct skcipher_request *subreq = &rctx->subreq; 264 int err; 265 266 err = xts_init_crypt(req, xts_encrypt_done) ?: 267 xts_xor_tweak_pre(req, true) ?: 268 crypto_skcipher_encrypt(subreq) ?: 269 xts_xor_tweak_post(req, true); 270 271 if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0)) 272 return err; 273 274 return xts_cts_final(req, crypto_skcipher_encrypt); 275 } 276 277 static int xts_decrypt(struct skcipher_request *req) 278 { 279 struct xts_request_ctx *rctx = skcipher_request_ctx(req); 280 struct skcipher_request *subreq = &rctx->subreq; 281 int err; 282 283 err = xts_init_crypt(req, xts_decrypt_done) ?: 284 xts_xor_tweak_pre(req, false) ?: 285 crypto_skcipher_decrypt(subreq) ?: 286 xts_xor_tweak_post(req, false); 287 288 if (err || likely((req->cryptlen % XTS_BLOCK_SIZE) == 0)) 289 return err; 290 291 return xts_cts_final(req, crypto_skcipher_decrypt); 292 } 293 294 static int xts_init_tfm(struct crypto_skcipher *tfm) 295 { 296 struct skcipher_instance *inst = skcipher_alg_instance(tfm); 297 struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst); 298 struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm); 299 struct crypto_skcipher *child; 300 struct crypto_cipher *tweak; 301 302 child = crypto_spawn_skcipher(&ictx->spawn); 303 if (IS_ERR(child)) 304 return PTR_ERR(child); 305 306 ctx->child = child; 307 308 tweak = crypto_alloc_cipher(ictx->name, 0, 0); 309 if (IS_ERR(tweak)) { 310 crypto_free_skcipher(ctx->child); 311 return PTR_ERR(tweak); 312 } 313 314 ctx->tweak = tweak; 315 316 crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(child) + 317 sizeof(struct xts_request_ctx)); 318 319 return 0; 320 } 321 322 static void xts_exit_tfm(struct crypto_skcipher *tfm) 323 { 324 struct xts_tfm_ctx *ctx = crypto_skcipher_ctx(tfm); 325 326 crypto_free_skcipher(ctx->child); 327 crypto_free_cipher(ctx->tweak); 328 } 329 330 static void xts_free_instance(struct skcipher_instance *inst) 331 { 332 struct xts_instance_ctx *ictx = skcipher_instance_ctx(inst); 333 334 crypto_drop_skcipher(&ictx->spawn); 335 kfree(inst); 336 } 337 338 static int xts_create(struct crypto_template *tmpl, struct rtattr **tb) 339 { 340 struct skcipher_instance *inst; 341 struct xts_instance_ctx *ctx; 342 struct skcipher_alg *alg; 343 const char *cipher_name; 344 u32 mask; 345 int err; 346 347 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask); 348 if (err) 349 return err; 350 351 cipher_name = crypto_attr_alg_name(tb[1]); 352 if (IS_ERR(cipher_name)) 353 return PTR_ERR(cipher_name); 354 355 inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL); 356 if (!inst) 357 return -ENOMEM; 358 359 ctx = skcipher_instance_ctx(inst); 360 361 err = crypto_grab_skcipher(&ctx->spawn, skcipher_crypto_instance(inst), 362 cipher_name, 0, mask); 363 if (err == -ENOENT) { 364 err = -ENAMETOOLONG; 365 if (snprintf(ctx->name, CRYPTO_MAX_ALG_NAME, "ecb(%s)", 366 cipher_name) >= CRYPTO_MAX_ALG_NAME) 367 goto err_free_inst; 368 369 err = crypto_grab_skcipher(&ctx->spawn, 370 skcipher_crypto_instance(inst), 371 ctx->name, 0, mask); 372 } 373 374 if (err) 375 goto err_free_inst; 376 377 alg = crypto_skcipher_spawn_alg(&ctx->spawn); 378 379 err = -EINVAL; 380 if (alg->base.cra_blocksize != XTS_BLOCK_SIZE) 381 goto err_free_inst; 382 383 if (crypto_skcipher_alg_ivsize(alg)) 384 goto err_free_inst; 385 386 err = crypto_inst_setname(skcipher_crypto_instance(inst), "xts", 387 &alg->base); 388 if (err) 389 goto err_free_inst; 390 391 err = -EINVAL; 392 cipher_name = alg->base.cra_name; 393 394 /* Alas we screwed up the naming so we have to mangle the 395 * cipher name. 396 */ 397 if (!strncmp(cipher_name, "ecb(", 4)) { 398 unsigned len; 399 400 len = strlcpy(ctx->name, cipher_name + 4, sizeof(ctx->name)); 401 if (len < 2 || len >= sizeof(ctx->name)) 402 goto err_free_inst; 403 404 if (ctx->name[len - 1] != ')') 405 goto err_free_inst; 406 407 ctx->name[len - 1] = 0; 408 409 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME, 410 "xts(%s)", ctx->name) >= CRYPTO_MAX_ALG_NAME) { 411 err = -ENAMETOOLONG; 412 goto err_free_inst; 413 } 414 } else 415 goto err_free_inst; 416 417 inst->alg.base.cra_priority = alg->base.cra_priority; 418 inst->alg.base.cra_blocksize = XTS_BLOCK_SIZE; 419 inst->alg.base.cra_alignmask = alg->base.cra_alignmask | 420 (__alignof__(u64) - 1); 421 422 inst->alg.ivsize = XTS_BLOCK_SIZE; 423 inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) * 2; 424 inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) * 2; 425 426 inst->alg.base.cra_ctxsize = sizeof(struct xts_tfm_ctx); 427 428 inst->alg.init = xts_init_tfm; 429 inst->alg.exit = xts_exit_tfm; 430 431 inst->alg.setkey = xts_setkey; 432 inst->alg.encrypt = xts_encrypt; 433 inst->alg.decrypt = xts_decrypt; 434 435 inst->free = xts_free_instance; 436 437 err = skcipher_register_instance(tmpl, inst); 438 if (err) { 439 err_free_inst: 440 xts_free_instance(inst); 441 } 442 return err; 443 } 444 445 static struct crypto_template xts_tmpl = { 446 .name = "xts", 447 .create = xts_create, 448 .module = THIS_MODULE, 449 }; 450 451 static int __init xts_module_init(void) 452 { 453 return crypto_register_template(&xts_tmpl); 454 } 455 456 static void __exit xts_module_exit(void) 457 { 458 crypto_unregister_template(&xts_tmpl); 459 } 460 461 subsys_initcall(xts_module_init); 462 module_exit(xts_module_exit); 463 464 MODULE_LICENSE("GPL"); 465 MODULE_DESCRIPTION("XTS block cipher mode"); 466 MODULE_ALIAS_CRYPTO("xts"); 467