crypto/xts.c

   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");