security/keys/encrypted-keys/encrypted.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2010 IBM Corporation
   4  * Copyright (C) 2010 Politecnico di Torino, Italy
   5  *                    TORSEC group -- https://security.polito.it
   6  *
   7  * Authors:
   8  * Mimi Zohar <zohar@us.ibm.com>
   9  * Roberto Sassu <roberto.sassu@polito.it>
  10  *
  11  * See Documentation/security/keys/trusted-encrypted.rst
  12  */
  13
  14 #include <linux/uaccess.h>
  15 #include <linux/module.h>
  16 #include <linux/init.h>
  17 #include <linux/slab.h>
  18 #include <linux/parser.h>
  19 #include <linux/string.h>
  20 #include <linux/err.h>
  21 #include <keys/user-type.h>
  22 #include <keys/trusted-type.h>
  23 #include <keys/encrypted-type.h>
  24 #include <linux/key-type.h>
  25 #include <linux/random.h>
  26 #include <linux/rcupdate.h>
  27 #include <linux/scatterlist.h>
  28 #include <linux/ctype.h>
  29 #include <crypto/aes.h>
  30 #include <crypto/algapi.h>
  31 #include <crypto/hash.h>
  32 #include <crypto/sha2.h>
  33 #include <crypto/skcipher.h>
  34
  35 #include "encrypted.h"
  36 #include "ecryptfs_format.h"
  37
  38 static const char KEY_TRUSTED_PREFIX[] = "trusted:";
  39 static const char KEY_USER_PREFIX[] = "user:";
  40 static const char hash_alg[] = "sha256";
  41 static const char hmac_alg[] = "hmac(sha256)";
  42 static const char blkcipher_alg[] = "cbc(aes)";
  43 static const char key_format_default[] = "default";
  44 static const char key_format_ecryptfs[] = "ecryptfs";
  45 static const char key_format_enc32[] = "enc32";
  46 static unsigned int ivsize;
  47 static int blksize;
  48
  49 #define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
  50 #define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
  51 #define KEY_ECRYPTFS_DESC_LEN 16
  52 #define HASH_SIZE SHA256_DIGEST_SIZE
  53 #define MAX_DATA_SIZE 4096
  54 #define MIN_DATA_SIZE  20
  55 #define KEY_ENC32_PAYLOAD_LEN 32
  56
  57 static struct crypto_shash *hash_tfm;
  58
  59 enum {
  60         Opt_new, Opt_load, Opt_update, Opt_err
  61 };
  62
  63 enum {
  64         Opt_default, Opt_ecryptfs, Opt_enc32, Opt_error
  65 };
  66
  67 static const match_table_t key_format_tokens = {
  68         {Opt_default, "default"},
  69         {Opt_ecryptfs, "ecryptfs"},
  70         {Opt_enc32, "enc32"},
  71         {Opt_error, NULL}
  72 };
  73
  74 static const match_table_t key_tokens = {
  75         {Opt_new, "new"},
  76         {Opt_load, "load"},
  77         {Opt_update, "update"},
  78         {Opt_err, NULL}
  79 };
  80
  81 static int aes_get_sizes(void)
  82 {
  83         struct crypto_skcipher *tfm;
  84
  85         tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
  86         if (IS_ERR(tfm)) {
  87                 pr_err("encrypted_key: failed to alloc_cipher (%ld)\n",
  88                        PTR_ERR(tfm));
  89                 return PTR_ERR(tfm);
  90         }
  91         ivsize = crypto_skcipher_ivsize(tfm);
  92         blksize = crypto_skcipher_blocksize(tfm);
  93         crypto_free_skcipher(tfm);
  94         return 0;
  95 }
  96
  97 /*
  98  * valid_ecryptfs_desc - verify the description of a new/loaded encrypted key
  99  *
 100  * The description of a encrypted key with format 'ecryptfs' must contain
 101  * exactly 16 hexadecimal characters.
 102  *
 103  */
 104 static int valid_ecryptfs_desc(const char *ecryptfs_desc)
 105 {
 106         int i;
 107
 108         if (strlen(ecryptfs_desc) != KEY_ECRYPTFS_DESC_LEN) {
 109                 pr_err("encrypted_key: key description must be %d hexadecimal "
 110                        "characters long\n", KEY_ECRYPTFS_DESC_LEN);
 111                 return -EINVAL;
 112         }
 113
 114         for (i = 0; i < KEY_ECRYPTFS_DESC_LEN; i++) {
 115                 if (!isxdigit(ecryptfs_desc[i])) {
 116                         pr_err("encrypted_key: key description must contain "
 117                                "only hexadecimal characters\n");
 118                         return -EINVAL;
 119                 }
 120         }
 121
 122         return 0;
 123 }
 124
 125 /*
 126  * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key
 127  *
 128  * key-type:= "trusted:" | "user:"
 129  * desc:= master-key description
 130  *
 131  * Verify that 'key-type' is valid and that 'desc' exists. On key update,
 132  * only the master key description is permitted to change, not the key-type.
 133  * The key-type remains constant.
 134  *
 135  * On success returns 0, otherwise -EINVAL.
 136  */
 137 static int valid_master_desc(const char *new_desc, const char *orig_desc)
 138 {
 139         int prefix_len;
 140
 141         if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN))
 142                 prefix_len = KEY_TRUSTED_PREFIX_LEN;
 143         else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN))
 144                 prefix_len = KEY_USER_PREFIX_LEN;
 145         else
 146                 return -EINVAL;
 147
 148         if (!new_desc[prefix_len])
 149                 return -EINVAL;
 150
 151         if (orig_desc && strncmp(new_desc, orig_desc, prefix_len))
 152                 return -EINVAL;
 153
 154         return 0;
 155 }
 156
 157 /*
 158  * datablob_parse - parse the keyctl data
 159  *
 160  * datablob format:
 161  * new [<format>] <master-key name> <decrypted data length>
 162  * load [<format>] <master-key name> <decrypted data length>
 163  *     <encrypted iv + data>
 164  * update <new-master-key name>
 165  *
 166  * Tokenizes a copy of the keyctl data, returning a pointer to each token,
 167  * which is null terminated.
 168  *
 169  * On success returns 0, otherwise -EINVAL.
 170  */
 171 static int datablob_parse(char *datablob, const char **format,
 172                           char **master_desc, char **decrypted_datalen,
 173                           char **hex_encoded_iv)
 174 {
 175         substring_t args[MAX_OPT_ARGS];
 176         int ret = -EINVAL;
 177         int key_cmd;
 178         int key_format;
 179         char *p, *keyword;
 180
 181         keyword = strsep(&datablob, " \t");
 182         if (!keyword) {
 183                 pr_info("encrypted_key: insufficient parameters specified\n");
 184                 return ret;
 185         }
 186         key_cmd = match_token(keyword, key_tokens, args);
 187
 188         /* Get optional format: default | ecryptfs */
 189         p = strsep(&datablob, " \t");
 190         if (!p) {
 191                 pr_err("encrypted_key: insufficient parameters specified\n");
 192                 return ret;
 193         }
 194
 195         key_format = match_token(p, key_format_tokens, args);
 196         switch (key_format) {
 197         case Opt_ecryptfs:
 198         case Opt_enc32:
 199         case Opt_default:
 200                 *format = p;
 201                 *master_desc = strsep(&datablob, " \t");
 202                 break;
 203         case Opt_error:
 204                 *master_desc = p;
 205                 break;
 206         }
 207
 208         if (!*master_desc) {
 209                 pr_info("encrypted_key: master key parameter is missing\n");
 210                 goto out;
 211         }
 212
 213         if (valid_master_desc(*master_desc, NULL) < 0) {
 214                 pr_info("encrypted_key: master key parameter \'%s\' "
 215                         "is invalid\n", *master_desc);
 216                 goto out;
 217         }
 218
 219         if (decrypted_datalen) {
 220                 *decrypted_datalen = strsep(&datablob, " \t");
 221                 if (!*decrypted_datalen) {
 222                         pr_info("encrypted_key: keylen parameter is missing\n");
 223                         goto out;
 224                 }
 225         }
 226
 227         switch (key_cmd) {
 228         case Opt_new:
 229                 if (!decrypted_datalen) {
 230                         pr_info("encrypted_key: keyword \'%s\' not allowed "
 231                                 "when called from .update method\n", keyword);
 232                         break;
 233                 }
 234                 ret = 0;
 235                 break;
 236         case Opt_load:
 237                 if (!decrypted_datalen) {
 238                         pr_info("encrypted_key: keyword \'%s\' not allowed "
 239                                 "when called from .update method\n", keyword);
 240                         break;
 241                 }
 242                 *hex_encoded_iv = strsep(&datablob, " \t");
 243                 if (!*hex_encoded_iv) {
 244                         pr_info("encrypted_key: hex blob is missing\n");
 245                         break;
 246                 }
 247                 ret = 0;
 248                 break;
 249         case Opt_update:
 250                 if (decrypted_datalen) {
 251                         pr_info("encrypted_key: keyword \'%s\' not allowed "
 252                                 "when called from .instantiate method\n",
 253                                 keyword);
 254                         break;
 255                 }
 256                 ret = 0;
 257                 break;
 258         case Opt_err:
 259                 pr_info("encrypted_key: keyword \'%s\' not recognized\n",
 260                         keyword);
 261                 break;
 262         }
 263 out:
 264         return ret;
 265 }
 266
 267 /*
 268  * datablob_format - format as an ascii string, before copying to userspace
 269  */
 270 static char *datablob_format(struct encrypted_key_payload *epayload,
 271                              size_t asciiblob_len)
 272 {
 273         char *ascii_buf, *bufp;
 274         u8 *iv = epayload->iv;
 275         int len;
 276         int i;
 277
 278         ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
 279         if (!ascii_buf)
 280                 goto out;
 281
 282         ascii_buf[asciiblob_len] = '\0';
 283
 284         /* copy datablob master_desc and datalen strings */
 285         len = sprintf(ascii_buf, "%s %s %s ", epayload->format,
 286                       epayload->master_desc, epayload->datalen);
 287
 288         /* convert the hex encoded iv, encrypted-data and HMAC to ascii */
 289         bufp = &ascii_buf[len];
 290         for (i = 0; i < (asciiblob_len - len) / 2; i++)
 291                 bufp = hex_byte_pack(bufp, iv[i]);
 292 out:
 293         return ascii_buf;
 294 }
 295
 296 /*
 297  * request_user_key - request the user key
 298  *
 299  * Use a user provided key to encrypt/decrypt an encrypted-key.
 300  */
 301 static struct key *request_user_key(const char *master_desc, const u8 **master_key,
 302                                     size_t *master_keylen)
 303 {
 304         const struct user_key_payload *upayload;
 305         struct key *ukey;
 306
 307         ukey = request_key(&key_type_user, master_desc, NULL);
 308         if (IS_ERR(ukey))
 309                 goto error;
 310
 311         down_read(&ukey->sem);
 312         upayload = user_key_payload_locked(ukey);
 313         if (!upayload) {
 314                 /* key was revoked before we acquired its semaphore */
 315                 up_read(&ukey->sem);
 316                 key_put(ukey);
 317                 ukey = ERR_PTR(-EKEYREVOKED);
 318                 goto error;
 319         }
 320         *master_key = upayload->data;
 321         *master_keylen = upayload->datalen;
 322 error:
 323         return ukey;
 324 }
 325
 326 static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
 327                      const u8 *buf, unsigned int buflen)
 328 {
 329         struct crypto_shash *tfm;
 330         int err;
 331
 332         tfm = crypto_alloc_shash(hmac_alg, 0, 0);
 333         if (IS_ERR(tfm)) {
 334                 pr_err("encrypted_key: can't alloc %s transform: %ld\n",
 335                        hmac_alg, PTR_ERR(tfm));
 336                 return PTR_ERR(tfm);
 337         }
 338
 339         err = crypto_shash_setkey(tfm, key, keylen);
 340         if (!err)
 341                 err = crypto_shash_tfm_digest(tfm, buf, buflen, digest);
 342         crypto_free_shash(tfm);
 343         return err;
 344 }
 345
 346 enum derived_key_type { ENC_KEY, AUTH_KEY };
 347
 348 /* Derive authentication/encryption key from trusted key */
 349 static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
 350                            const u8 *master_key, size_t master_keylen)
 351 {
 352         u8 *derived_buf;
 353         unsigned int derived_buf_len;
 354         int ret;
 355
 356         derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
 357         if (derived_buf_len < HASH_SIZE)
 358                 derived_buf_len = HASH_SIZE;
 359
 360         derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
 361         if (!derived_buf)
 362                 return -ENOMEM;
 363
 364         if (key_type)
 365                 strcpy(derived_buf, "AUTH_KEY");
 366         else
 367                 strcpy(derived_buf, "ENC_KEY");
 368
 369         memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
 370                master_keylen);
 371         ret = crypto_shash_tfm_digest(hash_tfm, derived_buf, derived_buf_len,
 372                                       derived_key);
 373         kfree_sensitive(derived_buf);
 374         return ret;
 375 }
 376
 377 static struct skcipher_request *init_skcipher_req(const u8 *key,
 378                                                   unsigned int key_len)
 379 {
 380         struct skcipher_request *req;
 381         struct crypto_skcipher *tfm;
 382         int ret;
 383
 384         tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
 385         if (IS_ERR(tfm)) {
 386                 pr_err("encrypted_key: failed to load %s transform (%ld)\n",
 387                        blkcipher_alg, PTR_ERR(tfm));
 388                 return ERR_CAST(tfm);
 389         }
 390
 391         ret = crypto_skcipher_setkey(tfm, key, key_len);
 392         if (ret < 0) {
 393                 pr_err("encrypted_key: failed to setkey (%d)\n", ret);
 394                 crypto_free_skcipher(tfm);
 395                 return ERR_PTR(ret);
 396         }
 397
 398         req = skcipher_request_alloc(tfm, GFP_KERNEL);
 399         if (!req) {
 400                 pr_err("encrypted_key: failed to allocate request for %s\n",
 401                        blkcipher_alg);
 402                 crypto_free_skcipher(tfm);
 403                 return ERR_PTR(-ENOMEM);
 404         }
 405
 406         skcipher_request_set_callback(req, 0, NULL, NULL);
 407         return req;
 408 }
 409
 410 static struct key *request_master_key(struct encrypted_key_payload *epayload,
 411                                       const u8 **master_key, size_t *master_keylen)
 412 {
 413         struct key *mkey = ERR_PTR(-EINVAL);
 414
 415         if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
 416                      KEY_TRUSTED_PREFIX_LEN)) {
 417                 mkey = request_trusted_key(epayload->master_desc +
 418                                            KEY_TRUSTED_PREFIX_LEN,
 419                                            master_key, master_keylen);
 420         } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
 421                             KEY_USER_PREFIX_LEN)) {
 422                 mkey = request_user_key(epayload->master_desc +
 423                                         KEY_USER_PREFIX_LEN,
 424                                         master_key, master_keylen);
 425         } else
 426                 goto out;
 427
 428         if (IS_ERR(mkey)) {
 429                 int ret = PTR_ERR(mkey);
 430
 431                 if (ret == -ENOTSUPP)
 432                         pr_info("encrypted_key: key %s not supported",
 433                                 epayload->master_desc);
 434                 else
 435                         pr_info("encrypted_key: key %s not found",
 436                                 epayload->master_desc);
 437                 goto out;
 438         }
 439
 440         dump_master_key(*master_key, *master_keylen);
 441 out:
 442         return mkey;
 443 }
 444
 445 /* Before returning data to userspace, encrypt decrypted data. */
 446 static int derived_key_encrypt(struct encrypted_key_payload *epayload,
 447                                const u8 *derived_key,
 448                                unsigned int derived_keylen)
 449 {
 450         struct scatterlist sg_in[2];
 451         struct scatterlist sg_out[1];
 452         struct crypto_skcipher *tfm;
 453         struct skcipher_request *req;
 454         unsigned int encrypted_datalen;
 455         u8 iv[AES_BLOCK_SIZE];
 456         int ret;
 457
 458         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 459
 460         req = init_skcipher_req(derived_key, derived_keylen);
 461         ret = PTR_ERR(req);
 462         if (IS_ERR(req))
 463                 goto out;
 464         dump_decrypted_data(epayload);
 465
 466         sg_init_table(sg_in, 2);
 467         sg_set_buf(&sg_in[0], epayload->decrypted_data,
 468                    epayload->decrypted_datalen);
 469         sg_set_page(&sg_in[1], ZERO_PAGE(0), AES_BLOCK_SIZE, 0);
 470
 471         sg_init_table(sg_out, 1);
 472         sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
 473
 474         memcpy(iv, epayload->iv, sizeof(iv));
 475         skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
 476         ret = crypto_skcipher_encrypt(req);
 477         tfm = crypto_skcipher_reqtfm(req);
 478         skcipher_request_free(req);
 479         crypto_free_skcipher(tfm);
 480         if (ret < 0)
 481                 pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
 482         else
 483                 dump_encrypted_data(epayload, encrypted_datalen);
 484 out:
 485         return ret;
 486 }
 487
 488 static int datablob_hmac_append(struct encrypted_key_payload *epayload,
 489                                 const u8 *master_key, size_t master_keylen)
 490 {
 491         u8 derived_key[HASH_SIZE];
 492         u8 *digest;
 493         int ret;
 494
 495         ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 496         if (ret < 0)
 497                 goto out;
 498
 499         digest = epayload->format + epayload->datablob_len;
 500         ret = calc_hmac(digest, derived_key, sizeof derived_key,
 501                         epayload->format, epayload->datablob_len);
 502         if (!ret)
 503                 dump_hmac(NULL, digest, HASH_SIZE);
 504 out:
 505         memzero_explicit(derived_key, sizeof(derived_key));
 506         return ret;
 507 }
 508
 509 /* verify HMAC before decrypting encrypted key */
 510 static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
 511                                 const u8 *format, const u8 *master_key,
 512                                 size_t master_keylen)
 513 {
 514         u8 derived_key[HASH_SIZE];
 515         u8 digest[HASH_SIZE];
 516         int ret;
 517         char *p;
 518         unsigned short len;
 519
 520         ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 521         if (ret < 0)
 522                 goto out;
 523
 524         len = epayload->datablob_len;
 525         if (!format) {
 526                 p = epayload->master_desc;
 527                 len -= strlen(epayload->format) + 1;
 528         } else
 529                 p = epayload->format;
 530
 531         ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
 532         if (ret < 0)
 533                 goto out;
 534         ret = crypto_memneq(digest, epayload->format + epayload->datablob_len,
 535                             sizeof(digest));
 536         if (ret) {
 537                 ret = -EINVAL;
 538                 dump_hmac("datablob",
 539                           epayload->format + epayload->datablob_len,
 540                           HASH_SIZE);
 541                 dump_hmac("calc", digest, HASH_SIZE);
 542         }
 543 out:
 544         memzero_explicit(derived_key, sizeof(derived_key));
 545         return ret;
 546 }
 547
 548 static int derived_key_decrypt(struct encrypted_key_payload *epayload,
 549                                const u8 *derived_key,
 550                                unsigned int derived_keylen)
 551 {
 552         struct scatterlist sg_in[1];
 553         struct scatterlist sg_out[2];
 554         struct crypto_skcipher *tfm;
 555         struct skcipher_request *req;
 556         unsigned int encrypted_datalen;
 557         u8 iv[AES_BLOCK_SIZE];
 558         u8 *pad;
 559         int ret;
 560
 561         /* Throwaway buffer to hold the unused zero padding at the end */
 562         pad = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
 563         if (!pad)
 564                 return -ENOMEM;
 565
 566         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 567         req = init_skcipher_req(derived_key, derived_keylen);
 568         ret = PTR_ERR(req);
 569         if (IS_ERR(req))
 570                 goto out;
 571         dump_encrypted_data(epayload, encrypted_datalen);
 572
 573         sg_init_table(sg_in, 1);
 574         sg_init_table(sg_out, 2);
 575         sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
 576         sg_set_buf(&sg_out[0], epayload->decrypted_data,
 577                    epayload->decrypted_datalen);
 578         sg_set_buf(&sg_out[1], pad, AES_BLOCK_SIZE);
 579
 580         memcpy(iv, epayload->iv, sizeof(iv));
 581         skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
 582         ret = crypto_skcipher_decrypt(req);
 583         tfm = crypto_skcipher_reqtfm(req);
 584         skcipher_request_free(req);
 585         crypto_free_skcipher(tfm);
 586         if (ret < 0)
 587                 goto out;
 588         dump_decrypted_data(epayload);
 589 out:
 590         kfree(pad);
 591         return ret;
 592 }
 593
 594 /* Allocate memory for decrypted key and datablob. */
 595 static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
 596                                                          const char *format,
 597                                                          const char *master_desc,
 598                                                          const char *datalen)
 599 {
 600         struct encrypted_key_payload *epayload = NULL;
 601         unsigned short datablob_len;
 602         unsigned short decrypted_datalen;
 603         unsigned short payload_datalen;
 604         unsigned int encrypted_datalen;
 605         unsigned int format_len;
 606         long dlen;
 607         int ret;
 608
 609         ret = kstrtol(datalen, 10, &dlen);
 610         if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
 611                 return ERR_PTR(-EINVAL);
 612
 613         format_len = (!format) ? strlen(key_format_default) : strlen(format);
 614         decrypted_datalen = dlen;
 615         payload_datalen = decrypted_datalen;
 616         if (format) {
 617                 if (!strcmp(format, key_format_ecryptfs)) {
 618                         if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
 619                                 pr_err("encrypted_key: keylen for the ecryptfs format must be equal to %d bytes\n",
 620                                         ECRYPTFS_MAX_KEY_BYTES);
 621                                 return ERR_PTR(-EINVAL);
 622                         }
 623                         decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
 624                         payload_datalen = sizeof(struct ecryptfs_auth_tok);
 625                 } else if (!strcmp(format, key_format_enc32)) {
 626                         if (decrypted_datalen != KEY_ENC32_PAYLOAD_LEN) {
 627                                 pr_err("encrypted_key: enc32 key payload incorrect length: %d\n",
 628                                                 decrypted_datalen);
 629                                 return ERR_PTR(-EINVAL);
 630                         }
 631                 }
 632         }
 633
 634         encrypted_datalen = roundup(decrypted_datalen, blksize);
 635
 636         datablob_len = format_len + 1 + strlen(master_desc) + 1
 637             + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
 638
 639         ret = key_payload_reserve(key, payload_datalen + datablob_len
 640                                   + HASH_SIZE + 1);
 641         if (ret < 0)
 642                 return ERR_PTR(ret);
 643
 644         epayload = kzalloc(sizeof(*epayload) + payload_datalen +
 645                            datablob_len + HASH_SIZE + 1, GFP_KERNEL);
 646         if (!epayload)
 647                 return ERR_PTR(-ENOMEM);
 648
 649         epayload->payload_datalen = payload_datalen;
 650         epayload->decrypted_datalen = decrypted_datalen;
 651         epayload->datablob_len = datablob_len;
 652         return epayload;
 653 }
 654
 655 static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
 656                                  const char *format, const char *hex_encoded_iv)
 657 {
 658         struct key *mkey;
 659         u8 derived_key[HASH_SIZE];
 660         const u8 *master_key;
 661         u8 *hmac;
 662         const char *hex_encoded_data;
 663         unsigned int encrypted_datalen;
 664         size_t master_keylen;
 665         size_t asciilen;
 666         int ret;
 667
 668         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 669         asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
 670         if (strlen(hex_encoded_iv) != asciilen)
 671                 return -EINVAL;
 672
 673         hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
 674         ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
 675         if (ret < 0)
 676                 return -EINVAL;
 677         ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
 678                       encrypted_datalen);
 679         if (ret < 0)
 680                 return -EINVAL;
 681
 682         hmac = epayload->format + epayload->datablob_len;
 683         ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
 684                       HASH_SIZE);
 685         if (ret < 0)
 686                 return -EINVAL;
 687
 688         mkey = request_master_key(epayload, &master_key, &master_keylen);
 689         if (IS_ERR(mkey))
 690                 return PTR_ERR(mkey);
 691
 692         ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
 693         if (ret < 0) {
 694                 pr_err("encrypted_key: bad hmac (%d)\n", ret);
 695                 goto out;
 696         }
 697
 698         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 699         if (ret < 0)
 700                 goto out;
 701
 702         ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
 703         if (ret < 0)
 704                 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
 705 out:
 706         up_read(&mkey->sem);
 707         key_put(mkey);
 708         memzero_explicit(derived_key, sizeof(derived_key));
 709         return ret;
 710 }
 711
 712 static void __ekey_init(struct encrypted_key_payload *epayload,
 713                         const char *format, const char *master_desc,
 714                         const char *datalen)
 715 {
 716         unsigned int format_len;
 717
 718         format_len = (!format) ? strlen(key_format_default) : strlen(format);
 719         epayload->format = epayload->payload_data + epayload->payload_datalen;
 720         epayload->master_desc = epayload->format + format_len + 1;
 721         epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
 722         epayload->iv = epayload->datalen + strlen(datalen) + 1;
 723         epayload->encrypted_data = epayload->iv + ivsize + 1;
 724         epayload->decrypted_data = epayload->payload_data;
 725
 726         if (!format)
 727                 memcpy(epayload->format, key_format_default, format_len);
 728         else {
 729                 if (!strcmp(format, key_format_ecryptfs))
 730                         epayload->decrypted_data =
 731                                 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
 732
 733                 memcpy(epayload->format, format, format_len);
 734         }
 735
 736         memcpy(epayload->master_desc, master_desc, strlen(master_desc));
 737         memcpy(epayload->datalen, datalen, strlen(datalen));
 738 }
 739
 740 /*
 741  * encrypted_init - initialize an encrypted key
 742  *
 743  * For a new key, use a random number for both the iv and data
 744  * itself.  For an old key, decrypt the hex encoded data.
 745  */
 746 static int encrypted_init(struct encrypted_key_payload *epayload,
 747                           const char *key_desc, const char *format,
 748                           const char *master_desc, const char *datalen,
 749                           const char *hex_encoded_iv)
 750 {
 751         int ret = 0;
 752
 753         if (format && !strcmp(format, key_format_ecryptfs)) {
 754                 ret = valid_ecryptfs_desc(key_desc);
 755                 if (ret < 0)
 756                         return ret;
 757
 758                 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
 759                                        key_desc);
 760         }
 761
 762         __ekey_init(epayload, format, master_desc, datalen);
 763         if (!hex_encoded_iv) {
 764                 get_random_bytes(epayload->iv, ivsize);
 765
 766                 get_random_bytes(epayload->decrypted_data,
 767                                  epayload->decrypted_datalen);
 768         } else
 769                 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
 770         return ret;
 771 }
 772
 773 /*
 774  * encrypted_instantiate - instantiate an encrypted key
 775  *
 776  * Decrypt an existing encrypted datablob or create a new encrypted key
 777  * based on a kernel random number.
 778  *
 779  * On success, return 0. Otherwise return errno.
 780  */
 781 static int encrypted_instantiate(struct key *key,
 782                                  struct key_preparsed_payload *prep)
 783 {
 784         struct encrypted_key_payload *epayload = NULL;
 785         char *datablob = NULL;
 786         const char *format = NULL;
 787         char *master_desc = NULL;
 788         char *decrypted_datalen = NULL;
 789         char *hex_encoded_iv = NULL;
 790         size_t datalen = prep->datalen;
 791         int ret;
 792
 793         if (datalen <= 0 || datalen > 32767 || !prep->data)
 794                 return -EINVAL;
 795
 796         datablob = kmalloc(datalen + 1, GFP_KERNEL);
 797         if (!datablob)
 798                 return -ENOMEM;
 799         datablob[datalen] = 0;
 800         memcpy(datablob, prep->data, datalen);
 801         ret = datablob_parse(datablob, &format, &master_desc,
 802                              &decrypted_datalen, &hex_encoded_iv);
 803         if (ret < 0)
 804                 goto out;
 805
 806         epayload = encrypted_key_alloc(key, format, master_desc,
 807                                        decrypted_datalen);
 808         if (IS_ERR(epayload)) {
 809                 ret = PTR_ERR(epayload);
 810                 goto out;
 811         }
 812         ret = encrypted_init(epayload, key->description, format, master_desc,
 813                              decrypted_datalen, hex_encoded_iv);
 814         if (ret < 0) {
 815                 kfree_sensitive(epayload);
 816                 goto out;
 817         }
 818
 819         rcu_assign_keypointer(key, epayload);
 820 out:
 821         kfree_sensitive(datablob);
 822         return ret;
 823 }
 824
 825 static void encrypted_rcu_free(struct rcu_head *rcu)
 826 {
 827         struct encrypted_key_payload *epayload;
 828
 829         epayload = container_of(rcu, struct encrypted_key_payload, rcu);
 830         kfree_sensitive(epayload);
 831 }
 832
 833 /*
 834  * encrypted_update - update the master key description
 835  *
 836  * Change the master key description for an existing encrypted key.
 837  * The next read will return an encrypted datablob using the new
 838  * master key description.
 839  *
 840  * On success, return 0. Otherwise return errno.
 841  */
 842 static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
 843 {
 844         struct encrypted_key_payload *epayload = key->payload.data[0];
 845         struct encrypted_key_payload *new_epayload;
 846         char *buf;
 847         char *new_master_desc = NULL;
 848         const char *format = NULL;
 849         size_t datalen = prep->datalen;
 850         int ret = 0;
 851
 852         if (key_is_negative(key))
 853                 return -ENOKEY;
 854         if (datalen <= 0 || datalen > 32767 || !prep->data)
 855                 return -EINVAL;
 856
 857         buf = kmalloc(datalen + 1, GFP_KERNEL);
 858         if (!buf)
 859                 return -ENOMEM;
 860
 861         buf[datalen] = 0;
 862         memcpy(buf, prep->data, datalen);
 863         ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
 864         if (ret < 0)
 865                 goto out;
 866
 867         ret = valid_master_desc(new_master_desc, epayload->master_desc);
 868         if (ret < 0)
 869                 goto out;
 870
 871         new_epayload = encrypted_key_alloc(key, epayload->format,
 872                                            new_master_desc, epayload->datalen);
 873         if (IS_ERR(new_epayload)) {
 874                 ret = PTR_ERR(new_epayload);
 875                 goto out;
 876         }
 877
 878         __ekey_init(new_epayload, epayload->format, new_master_desc,
 879                     epayload->datalen);
 880
 881         memcpy(new_epayload->iv, epayload->iv, ivsize);
 882         memcpy(new_epayload->payload_data, epayload->payload_data,
 883                epayload->payload_datalen);
 884
 885         rcu_assign_keypointer(key, new_epayload);
 886         call_rcu(&epayload->rcu, encrypted_rcu_free);
 887 out:
 888         kfree_sensitive(buf);
 889         return ret;
 890 }
 891
 892 /*
 893  * encrypted_read - format and copy out the encrypted data
 894  *
 895  * The resulting datablob format is:
 896  * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
 897  *
 898  * On success, return to userspace the encrypted key datablob size.
 899  */
 900 static long encrypted_read(const struct key *key, char *buffer,
 901                            size_t buflen)
 902 {
 903         struct encrypted_key_payload *epayload;
 904         struct key *mkey;
 905         const u8 *master_key;
 906         size_t master_keylen;
 907         char derived_key[HASH_SIZE];
 908         char *ascii_buf;
 909         size_t asciiblob_len;
 910         int ret;
 911
 912         epayload = dereference_key_locked(key);
 913
 914         /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
 915         asciiblob_len = epayload->datablob_len + ivsize + 1
 916             + roundup(epayload->decrypted_datalen, blksize)
 917             + (HASH_SIZE * 2);
 918
 919         if (!buffer || buflen < asciiblob_len)
 920                 return asciiblob_len;
 921
 922         mkey = request_master_key(epayload, &master_key, &master_keylen);
 923         if (IS_ERR(mkey))
 924                 return PTR_ERR(mkey);
 925
 926         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 927         if (ret < 0)
 928                 goto out;
 929
 930         ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
 931         if (ret < 0)
 932                 goto out;
 933
 934         ret = datablob_hmac_append(epayload, master_key, master_keylen);
 935         if (ret < 0)
 936                 goto out;
 937
 938         ascii_buf = datablob_format(epayload, asciiblob_len);
 939         if (!ascii_buf) {
 940                 ret = -ENOMEM;
 941                 goto out;
 942         }
 943
 944         up_read(&mkey->sem);
 945         key_put(mkey);
 946         memzero_explicit(derived_key, sizeof(derived_key));
 947
 948         memcpy(buffer, ascii_buf, asciiblob_len);
 949         kfree_sensitive(ascii_buf);
 950
 951         return asciiblob_len;
 952 out:
 953         up_read(&mkey->sem);
 954         key_put(mkey);
 955         memzero_explicit(derived_key, sizeof(derived_key));
 956         return ret;
 957 }
 958
 959 /*
 960  * encrypted_destroy - clear and free the key's payload
 961  */
 962 static void encrypted_destroy(struct key *key)
 963 {
 964         kfree_sensitive(key->payload.data[0]);
 965 }
 966
 967 struct key_type key_type_encrypted = {
 968         .name = "encrypted",
 969         .instantiate = encrypted_instantiate,
 970         .update = encrypted_update,
 971         .destroy = encrypted_destroy,
 972         .describe = user_describe,
 973         .read = encrypted_read,
 974 };
 975 EXPORT_SYMBOL_GPL(key_type_encrypted);
 976
 977 static int __init init_encrypted(void)
 978 {
 979         int ret;
 980
 981         hash_tfm = crypto_alloc_shash(hash_alg, 0, 0);
 982         if (IS_ERR(hash_tfm)) {
 983                 pr_err("encrypted_key: can't allocate %s transform: %ld\n",
 984                        hash_alg, PTR_ERR(hash_tfm));
 985                 return PTR_ERR(hash_tfm);
 986         }
 987
 988         ret = aes_get_sizes();
 989         if (ret < 0)
 990                 goto out;
 991         ret = register_key_type(&key_type_encrypted);
 992         if (ret < 0)
 993                 goto out;
 994         return 0;
 995 out:
 996         crypto_free_shash(hash_tfm);
 997         return ret;
 998
 999 }
1000
1001 static void __exit cleanup_encrypted(void)
1002 {
1003         crypto_free_shash(hash_tfm);
1004         unregister_key_type(&key_type_encrypted);
1005 }
1006
1007 late_initcall(init_encrypted);
1008 module_exit(cleanup_encrypted);
1009
1010 MODULE_LICENSE("GPL");