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