security/keys/encrypted-keys/encrypted.c

   1 /*
   2  * Copyright (C) 2010 IBM Corporation
   3  * Copyright (C) 2010 Politecnico di Torino, Italy
   4  *                    TORSEC group -- http://security.polito.it
   5  *
   6  * Authors:
   7  * Mimi Zohar <zohar@us.ibm.com>
   8  * Roberto Sassu <roberto.sassu@polito.it>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License as published by
  12  * the Free Software Foundation, version 2 of the License.
  13  *
  14  * See Documentation/security/keys/trusted-encrypted.rst
  15  */
  16
  17 #include <linux/uaccess.h>
  18 #include <linux/module.h>
  19 #include <linux/init.h>
  20 #include <linux/slab.h>
  21 #include <linux/parser.h>
  22 #include <linux/string.h>
  23 #include <linux/err.h>
  24 #include <keys/user-type.h>
  25 #include <keys/trusted-type.h>
  26 #include <keys/encrypted-type.h>
  27 #include <linux/key-type.h>
  28 #include <linux/random.h>
  29 #include <linux/rcupdate.h>
  30 #include <linux/scatterlist.h>
  31 #include <linux/ctype.h>
  32 #include <crypto/aes.h>
  33 #include <crypto/algapi.h>
  34 #include <crypto/hash.h>
  35 #include <crypto/sha.h>
  36 #include <crypto/skcipher.h>
  37
  38 #include "encrypted.h"
  39 #include "ecryptfs_format.h"
  40
  41 static const char KEY_TRUSTED_PREFIX[] = "trusted:";
  42 static const char KEY_USER_PREFIX[] = "user:";
  43 static const char hash_alg[] = "sha256";
  44 static const char hmac_alg[] = "hmac(sha256)";
  45 static const char blkcipher_alg[] = "cbc(aes)";
  46 static const char key_format_default[] = "default";
  47 static const char key_format_ecryptfs[] = "ecryptfs";
  48 static unsigned int ivsize;
  49 static int blksize;
  50
  51 #define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
  52 #define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
  53 #define KEY_ECRYPTFS_DESC_LEN 16
  54 #define HASH_SIZE SHA256_DIGEST_SIZE
  55 #define MAX_DATA_SIZE 4096
  56 #define MIN_DATA_SIZE  20
  57
  58 static struct crypto_shash *hash_tfm;
  59
  60 enum {
  61         Opt_err = -1, Opt_new, Opt_load, Opt_update
  62 };
  63
  64 enum {
  65         Opt_error = -1, Opt_default, Opt_ecryptfs
  66 };
  67
  68 static const match_table_t key_format_tokens = {
  69         {Opt_default, "default"},
  70         {Opt_ecryptfs, "ecryptfs"},
  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_default:
 199                 *format = p;
 200                 *master_desc = strsep(&datablob, " \t");
 201                 break;
 202         case Opt_error:
 203                 *master_desc = p;
 204                 break;
 205         }
 206
 207         if (!*master_desc) {
 208                 pr_info("encrypted_key: master key parameter is missing\n");
 209                 goto out;
 210         }
 211
 212         if (valid_master_desc(*master_desc, NULL) < 0) {
 213                 pr_info("encrypted_key: master key parameter \'%s\' "
 214                         "is invalid\n", *master_desc);
 215                 goto out;
 216         }
 217
 218         if (decrypted_datalen) {
 219                 *decrypted_datalen = strsep(&datablob, " \t");
 220                 if (!*decrypted_datalen) {
 221                         pr_info("encrypted_key: keylen parameter is missing\n");
 222                         goto out;
 223                 }
 224         }
 225
 226         switch (key_cmd) {
 227         case Opt_new:
 228                 if (!decrypted_datalen) {
 229                         pr_info("encrypted_key: keyword \'%s\' not allowed "
 230                                 "when called from .update method\n", keyword);
 231                         break;
 232                 }
 233                 ret = 0;
 234                 break;
 235         case Opt_load:
 236                 if (!decrypted_datalen) {
 237                         pr_info("encrypted_key: keyword \'%s\' not allowed "
 238                                 "when called from .update method\n", keyword);
 239                         break;
 240                 }
 241                 *hex_encoded_iv = strsep(&datablob, " \t");
 242                 if (!*hex_encoded_iv) {
 243                         pr_info("encrypted_key: hex blob is missing\n");
 244                         break;
 245                 }
 246                 ret = 0;
 247                 break;
 248         case Opt_update:
 249                 if (decrypted_datalen) {
 250                         pr_info("encrypted_key: keyword \'%s\' not allowed "
 251                                 "when called from .instantiate method\n",
 252                                 keyword);
 253                         break;
 254                 }
 255                 ret = 0;
 256                 break;
 257         case Opt_err:
 258                 pr_info("encrypted_key: keyword \'%s\' not recognized\n",
 259                         keyword);
 260                 break;
 261         }
 262 out:
 263         return ret;
 264 }
 265
 266 /*
 267  * datablob_format - format as an ascii string, before copying to userspace
 268  */
 269 static char *datablob_format(struct encrypted_key_payload *epayload,
 270                              size_t asciiblob_len)
 271 {
 272         char *ascii_buf, *bufp;
 273         u8 *iv = epayload->iv;
 274         int len;
 275         int i;
 276
 277         ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
 278         if (!ascii_buf)
 279                 goto out;
 280
 281         ascii_buf[asciiblob_len] = '\0';
 282
 283         /* copy datablob master_desc and datalen strings */
 284         len = sprintf(ascii_buf, "%s %s %s ", epayload->format,
 285                       epayload->master_desc, epayload->datalen);
 286
 287         /* convert the hex encoded iv, encrypted-data and HMAC to ascii */
 288         bufp = &ascii_buf[len];
 289         for (i = 0; i < (asciiblob_len - len) / 2; i++)
 290                 bufp = hex_byte_pack(bufp, iv[i]);
 291 out:
 292         return ascii_buf;
 293 }
 294
 295 /*
 296  * request_user_key - request the user key
 297  *
 298  * Use a user provided key to encrypt/decrypt an encrypted-key.
 299  */
 300 static struct key *request_user_key(const char *master_desc, const u8 **master_key,
 301                                     size_t *master_keylen)
 302 {
 303         const struct user_key_payload *upayload;
 304         struct key *ukey;
 305
 306         ukey = request_key(&key_type_user, master_desc, NULL);
 307         if (IS_ERR(ukey))
 308                 goto error;
 309
 310         down_read(&ukey->sem);
 311         upayload = user_key_payload_locked(ukey);
 312         if (!upayload) {
 313                 /* key was revoked before we acquired its semaphore */
 314                 up_read(&ukey->sem);
 315                 key_put(ukey);
 316                 ukey = ERR_PTR(-EKEYREVOKED);
 317                 goto error;
 318         }
 319         *master_key = upayload->data;
 320         *master_keylen = upayload->datalen;
 321 error:
 322         return ukey;
 323 }
 324
 325 static int calc_hash(struct crypto_shash *tfm, u8 *digest,
 326                      const u8 *buf, unsigned int buflen)
 327 {
 328         SHASH_DESC_ON_STACK(desc, tfm);
 329         int err;
 330
 331         desc->tfm = tfm;
 332         desc->flags = 0;
 333
 334         err = crypto_shash_digest(desc, buf, buflen, digest);
 335         shash_desc_zero(desc);
 336         return err;
 337 }
 338
 339 static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
 340                      const u8 *buf, unsigned int buflen)
 341 {
 342         struct crypto_shash *tfm;
 343         int err;
 344
 345         tfm = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC);
 346         if (IS_ERR(tfm)) {
 347                 pr_err("encrypted_key: can't alloc %s transform: %ld\n",
 348                        hmac_alg, PTR_ERR(tfm));
 349                 return PTR_ERR(tfm);
 350         }
 351
 352         err = crypto_shash_setkey(tfm, key, keylen);
 353         if (!err)
 354                 err = calc_hash(tfm, digest, buf, buflen);
 355         crypto_free_shash(tfm);
 356         return err;
 357 }
 358
 359 enum derived_key_type { ENC_KEY, AUTH_KEY };
 360
 361 /* Derive authentication/encryption key from trusted key */
 362 static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
 363                            const u8 *master_key, size_t master_keylen)
 364 {
 365         u8 *derived_buf;
 366         unsigned int derived_buf_len;
 367         int ret;
 368
 369         derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
 370         if (derived_buf_len < HASH_SIZE)
 371                 derived_buf_len = HASH_SIZE;
 372
 373         derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
 374         if (!derived_buf)
 375                 return -ENOMEM;
 376
 377         if (key_type)
 378                 strcpy(derived_buf, "AUTH_KEY");
 379         else
 380                 strcpy(derived_buf, "ENC_KEY");
 381
 382         memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
 383                master_keylen);
 384         ret = calc_hash(hash_tfm, derived_key, derived_buf, derived_buf_len);
 385         kzfree(derived_buf);
 386         return ret;
 387 }
 388
 389 static struct skcipher_request *init_skcipher_req(const u8 *key,
 390                                                   unsigned int key_len)
 391 {
 392         struct skcipher_request *req;
 393         struct crypto_skcipher *tfm;
 394         int ret;
 395
 396         tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
 397         if (IS_ERR(tfm)) {
 398                 pr_err("encrypted_key: failed to load %s transform (%ld)\n",
 399                        blkcipher_alg, PTR_ERR(tfm));
 400                 return ERR_CAST(tfm);
 401         }
 402
 403         ret = crypto_skcipher_setkey(tfm, key, key_len);
 404         if (ret < 0) {
 405                 pr_err("encrypted_key: failed to setkey (%d)\n", ret);
 406                 crypto_free_skcipher(tfm);
 407                 return ERR_PTR(ret);
 408         }
 409
 410         req = skcipher_request_alloc(tfm, GFP_KERNEL);
 411         if (!req) {
 412                 pr_err("encrypted_key: failed to allocate request for %s\n",
 413                        blkcipher_alg);
 414                 crypto_free_skcipher(tfm);
 415                 return ERR_PTR(-ENOMEM);
 416         }
 417
 418         skcipher_request_set_callback(req, 0, NULL, NULL);
 419         return req;
 420 }
 421
 422 static struct key *request_master_key(struct encrypted_key_payload *epayload,
 423                                       const u8 **master_key, size_t *master_keylen)
 424 {
 425         struct key *mkey = ERR_PTR(-EINVAL);
 426
 427         if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
 428                      KEY_TRUSTED_PREFIX_LEN)) {
 429                 mkey = request_trusted_key(epayload->master_desc +
 430                                            KEY_TRUSTED_PREFIX_LEN,
 431                                            master_key, master_keylen);
 432         } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
 433                             KEY_USER_PREFIX_LEN)) {
 434                 mkey = request_user_key(epayload->master_desc +
 435                                         KEY_USER_PREFIX_LEN,
 436                                         master_key, master_keylen);
 437         } else
 438                 goto out;
 439
 440         if (IS_ERR(mkey)) {
 441                 int ret = PTR_ERR(mkey);
 442
 443                 if (ret == -ENOTSUPP)
 444                         pr_info("encrypted_key: key %s not supported",
 445                                 epayload->master_desc);
 446                 else
 447                         pr_info("encrypted_key: key %s not found",
 448                                 epayload->master_desc);
 449                 goto out;
 450         }
 451
 452         dump_master_key(*master_key, *master_keylen);
 453 out:
 454         return mkey;
 455 }
 456
 457 /* Before returning data to userspace, encrypt decrypted data. */
 458 static int derived_key_encrypt(struct encrypted_key_payload *epayload,
 459                                const u8 *derived_key,
 460                                unsigned int derived_keylen)
 461 {
 462         struct scatterlist sg_in[2];
 463         struct scatterlist sg_out[1];
 464         struct crypto_skcipher *tfm;
 465         struct skcipher_request *req;
 466         unsigned int encrypted_datalen;
 467         u8 iv[AES_BLOCK_SIZE];
 468         int ret;
 469
 470         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 471
 472         req = init_skcipher_req(derived_key, derived_keylen);
 473         ret = PTR_ERR(req);
 474         if (IS_ERR(req))
 475                 goto out;
 476         dump_decrypted_data(epayload);
 477
 478         sg_init_table(sg_in, 2);
 479         sg_set_buf(&sg_in[0], epayload->decrypted_data,
 480                    epayload->decrypted_datalen);
 481         sg_set_page(&sg_in[1], ZERO_PAGE(0), AES_BLOCK_SIZE, 0);
 482
 483         sg_init_table(sg_out, 1);
 484         sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
 485
 486         memcpy(iv, epayload->iv, sizeof(iv));
 487         skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
 488         ret = crypto_skcipher_encrypt(req);
 489         tfm = crypto_skcipher_reqtfm(req);
 490         skcipher_request_free(req);
 491         crypto_free_skcipher(tfm);
 492         if (ret < 0)
 493                 pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
 494         else
 495                 dump_encrypted_data(epayload, encrypted_datalen);
 496 out:
 497         return ret;
 498 }
 499
 500 static int datablob_hmac_append(struct encrypted_key_payload *epayload,
 501                                 const u8 *master_key, size_t master_keylen)
 502 {
 503         u8 derived_key[HASH_SIZE];
 504         u8 *digest;
 505         int ret;
 506
 507         ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 508         if (ret < 0)
 509                 goto out;
 510
 511         digest = epayload->format + epayload->datablob_len;
 512         ret = calc_hmac(digest, derived_key, sizeof derived_key,
 513                         epayload->format, epayload->datablob_len);
 514         if (!ret)
 515                 dump_hmac(NULL, digest, HASH_SIZE);
 516 out:
 517         memzero_explicit(derived_key, sizeof(derived_key));
 518         return ret;
 519 }
 520
 521 /* verify HMAC before decrypting encrypted key */
 522 static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
 523                                 const u8 *format, const u8 *master_key,
 524                                 size_t master_keylen)
 525 {
 526         u8 derived_key[HASH_SIZE];
 527         u8 digest[HASH_SIZE];
 528         int ret;
 529         char *p;
 530         unsigned short len;
 531
 532         ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 533         if (ret < 0)
 534                 goto out;
 535
 536         len = epayload->datablob_len;
 537         if (!format) {
 538                 p = epayload->master_desc;
 539                 len -= strlen(epayload->format) + 1;
 540         } else
 541                 p = epayload->format;
 542
 543         ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
 544         if (ret < 0)
 545                 goto out;
 546         ret = crypto_memneq(digest, epayload->format + epayload->datablob_len,
 547                             sizeof(digest));
 548         if (ret) {
 549                 ret = -EINVAL;
 550                 dump_hmac("datablob",
 551                           epayload->format + epayload->datablob_len,
 552                           HASH_SIZE);
 553                 dump_hmac("calc", digest, HASH_SIZE);
 554         }
 555 out:
 556         memzero_explicit(derived_key, sizeof(derived_key));
 557         return ret;
 558 }
 559
 560 static int derived_key_decrypt(struct encrypted_key_payload *epayload,
 561                                const u8 *derived_key,
 562                                unsigned int derived_keylen)
 563 {
 564         struct scatterlist sg_in[1];
 565         struct scatterlist sg_out[2];
 566         struct crypto_skcipher *tfm;
 567         struct skcipher_request *req;
 568         unsigned int encrypted_datalen;
 569         u8 iv[AES_BLOCK_SIZE];
 570         u8 *pad;
 571         int ret;
 572
 573         /* Throwaway buffer to hold the unused zero padding at the end */
 574         pad = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
 575         if (!pad)
 576                 return -ENOMEM;
 577
 578         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 579         req = init_skcipher_req(derived_key, derived_keylen);
 580         ret = PTR_ERR(req);
 581         if (IS_ERR(req))
 582                 goto out;
 583         dump_encrypted_data(epayload, encrypted_datalen);
 584
 585         sg_init_table(sg_in, 1);
 586         sg_init_table(sg_out, 2);
 587         sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
 588         sg_set_buf(&sg_out[0], epayload->decrypted_data,
 589                    epayload->decrypted_datalen);
 590         sg_set_buf(&sg_out[1], pad, AES_BLOCK_SIZE);
 591
 592         memcpy(iv, epayload->iv, sizeof(iv));
 593         skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
 594         ret = crypto_skcipher_decrypt(req);
 595         tfm = crypto_skcipher_reqtfm(req);
 596         skcipher_request_free(req);
 597         crypto_free_skcipher(tfm);
 598         if (ret < 0)
 599                 goto out;
 600         dump_decrypted_data(epayload);
 601 out:
 602         kfree(pad);
 603         return ret;
 604 }
 605
 606 /* Allocate memory for decrypted key and datablob. */
 607 static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
 608                                                          const char *format,
 609                                                          const char *master_desc,
 610                                                          const char *datalen)
 611 {
 612         struct encrypted_key_payload *epayload = NULL;
 613         unsigned short datablob_len;
 614         unsigned short decrypted_datalen;
 615         unsigned short payload_datalen;
 616         unsigned int encrypted_datalen;
 617         unsigned int format_len;
 618         long dlen;
 619         int ret;
 620
 621         ret = kstrtol(datalen, 10, &dlen);
 622         if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
 623                 return ERR_PTR(-EINVAL);
 624
 625         format_len = (!format) ? strlen(key_format_default) : strlen(format);
 626         decrypted_datalen = dlen;
 627         payload_datalen = decrypted_datalen;
 628         if (format && !strcmp(format, key_format_ecryptfs)) {
 629                 if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
 630                         pr_err("encrypted_key: keylen for the ecryptfs format "
 631                                "must be equal to %d bytes\n",
 632                                ECRYPTFS_MAX_KEY_BYTES);
 633                         return ERR_PTR(-EINVAL);
 634                 }
 635                 decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
 636                 payload_datalen = sizeof(struct ecryptfs_auth_tok);
 637         }
 638
 639         encrypted_datalen = roundup(decrypted_datalen, blksize);
 640
 641         datablob_len = format_len + 1 + strlen(master_desc) + 1
 642             + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
 643
 644         ret = key_payload_reserve(key, payload_datalen + datablob_len
 645                                   + HASH_SIZE + 1);
 646         if (ret < 0)
 647                 return ERR_PTR(ret);
 648
 649         epayload = kzalloc(sizeof(*epayload) + payload_datalen +
 650                            datablob_len + HASH_SIZE + 1, GFP_KERNEL);
 651         if (!epayload)
 652                 return ERR_PTR(-ENOMEM);
 653
 654         epayload->payload_datalen = payload_datalen;
 655         epayload->decrypted_datalen = decrypted_datalen;
 656         epayload->datablob_len = datablob_len;
 657         return epayload;
 658 }
 659
 660 static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
 661                                  const char *format, const char *hex_encoded_iv)
 662 {
 663         struct key *mkey;
 664         u8 derived_key[HASH_SIZE];
 665         const u8 *master_key;
 666         u8 *hmac;
 667         const char *hex_encoded_data;
 668         unsigned int encrypted_datalen;
 669         size_t master_keylen;
 670         size_t asciilen;
 671         int ret;
 672
 673         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 674         asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
 675         if (strlen(hex_encoded_iv) != asciilen)
 676                 return -EINVAL;
 677
 678         hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
 679         ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
 680         if (ret < 0)
 681                 return -EINVAL;
 682         ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
 683                       encrypted_datalen);
 684         if (ret < 0)
 685                 return -EINVAL;
 686
 687         hmac = epayload->format + epayload->datablob_len;
 688         ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
 689                       HASH_SIZE);
 690         if (ret < 0)
 691                 return -EINVAL;
 692
 693         mkey = request_master_key(epayload, &master_key, &master_keylen);
 694         if (IS_ERR(mkey))
 695                 return PTR_ERR(mkey);
 696
 697         ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
 698         if (ret < 0) {
 699                 pr_err("encrypted_key: bad hmac (%d)\n", ret);
 700                 goto out;
 701         }
 702
 703         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 704         if (ret < 0)
 705                 goto out;
 706
 707         ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
 708         if (ret < 0)
 709                 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
 710 out:
 711         up_read(&mkey->sem);
 712         key_put(mkey);
 713         memzero_explicit(derived_key, sizeof(derived_key));
 714         return ret;
 715 }
 716
 717 static void __ekey_init(struct encrypted_key_payload *epayload,
 718                         const char *format, const char *master_desc,
 719                         const char *datalen)
 720 {
 721         unsigned int format_len;
 722
 723         format_len = (!format) ? strlen(key_format_default) : strlen(format);
 724         epayload->format = epayload->payload_data + epayload->payload_datalen;
 725         epayload->master_desc = epayload->format + format_len + 1;
 726         epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
 727         epayload->iv = epayload->datalen + strlen(datalen) + 1;
 728         epayload->encrypted_data = epayload->iv + ivsize + 1;
 729         epayload->decrypted_data = epayload->payload_data;
 730
 731         if (!format)
 732                 memcpy(epayload->format, key_format_default, format_len);
 733         else {
 734                 if (!strcmp(format, key_format_ecryptfs))
 735                         epayload->decrypted_data =
 736                                 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
 737
 738                 memcpy(epayload->format, format, format_len);
 739         }
 740
 741         memcpy(epayload->master_desc, master_desc, strlen(master_desc));
 742         memcpy(epayload->datalen, datalen, strlen(datalen));
 743 }
 744
 745 /*
 746  * encrypted_init - initialize an encrypted key
 747  *
 748  * For a new key, use a random number for both the iv and data
 749  * itself.  For an old key, decrypt the hex encoded data.
 750  */
 751 static int encrypted_init(struct encrypted_key_payload *epayload,
 752                           const char *key_desc, const char *format,
 753                           const char *master_desc, const char *datalen,
 754                           const char *hex_encoded_iv)
 755 {
 756         int ret = 0;
 757
 758         if (format && !strcmp(format, key_format_ecryptfs)) {
 759                 ret = valid_ecryptfs_desc(key_desc);
 760                 if (ret < 0)
 761                         return ret;
 762
 763                 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
 764                                        key_desc);
 765         }
 766
 767         __ekey_init(epayload, format, master_desc, datalen);
 768         if (!hex_encoded_iv) {
 769                 get_random_bytes(epayload->iv, ivsize);
 770
 771                 get_random_bytes(epayload->decrypted_data,
 772                                  epayload->decrypted_datalen);
 773         } else
 774                 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
 775         return ret;
 776 }
 777
 778 /*
 779  * encrypted_instantiate - instantiate an encrypted key
 780  *
 781  * Decrypt an existing encrypted datablob or create a new encrypted key
 782  * based on a kernel random number.
 783  *
 784  * On success, return 0. Otherwise return errno.
 785  */
 786 static int encrypted_instantiate(struct key *key,
 787                                  struct key_preparsed_payload *prep)
 788 {
 789         struct encrypted_key_payload *epayload = NULL;
 790         char *datablob = NULL;
 791         const char *format = NULL;
 792         char *master_desc = NULL;
 793         char *decrypted_datalen = NULL;
 794         char *hex_encoded_iv = NULL;
 795         size_t datalen = prep->datalen;
 796         int ret;
 797
 798         if (datalen <= 0 || datalen > 32767 || !prep->data)
 799                 return -EINVAL;
 800
 801         datablob = kmalloc(datalen + 1, GFP_KERNEL);
 802         if (!datablob)
 803                 return -ENOMEM;
 804         datablob[datalen] = 0;
 805         memcpy(datablob, prep->data, datalen);
 806         ret = datablob_parse(datablob, &format, &master_desc,
 807                              &decrypted_datalen, &hex_encoded_iv);
 808         if (ret < 0)
 809                 goto out;
 810
 811         epayload = encrypted_key_alloc(key, format, master_desc,
 812                                        decrypted_datalen);
 813         if (IS_ERR(epayload)) {
 814                 ret = PTR_ERR(epayload);
 815                 goto out;
 816         }
 817         ret = encrypted_init(epayload, key->description, format, master_desc,
 818                              decrypted_datalen, hex_encoded_iv);
 819         if (ret < 0) {
 820                 kzfree(epayload);
 821                 goto out;
 822         }
 823
 824         rcu_assign_keypointer(key, epayload);
 825 out:
 826         kzfree(datablob);
 827         return ret;
 828 }
 829
 830 static void encrypted_rcu_free(struct rcu_head *rcu)
 831 {
 832         struct encrypted_key_payload *epayload;
 833
 834         epayload = container_of(rcu, struct encrypted_key_payload, rcu);
 835         kzfree(epayload);
 836 }
 837
 838 /*
 839  * encrypted_update - update the master key description
 840  *
 841  * Change the master key description for an existing encrypted key.
 842  * The next read will return an encrypted datablob using the new
 843  * master key description.
 844  *
 845  * On success, return 0. Otherwise return errno.
 846  */
 847 static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
 848 {
 849         struct encrypted_key_payload *epayload = key->payload.data[0];
 850         struct encrypted_key_payload *new_epayload;
 851         char *buf;
 852         char *new_master_desc = NULL;
 853         const char *format = NULL;
 854         size_t datalen = prep->datalen;
 855         int ret = 0;
 856
 857         if (key_is_negative(key))
 858                 return -ENOKEY;
 859         if (datalen <= 0 || datalen > 32767 || !prep->data)
 860                 return -EINVAL;
 861
 862         buf = kmalloc(datalen + 1, GFP_KERNEL);
 863         if (!buf)
 864                 return -ENOMEM;
 865
 866         buf[datalen] = 0;
 867         memcpy(buf, prep->data, datalen);
 868         ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
 869         if (ret < 0)
 870                 goto out;
 871
 872         ret = valid_master_desc(new_master_desc, epayload->master_desc);
 873         if (ret < 0)
 874                 goto out;
 875
 876         new_epayload = encrypted_key_alloc(key, epayload->format,
 877                                            new_master_desc, epayload->datalen);
 878         if (IS_ERR(new_epayload)) {
 879                 ret = PTR_ERR(new_epayload);
 880                 goto out;
 881         }
 882
 883         __ekey_init(new_epayload, epayload->format, new_master_desc,
 884                     epayload->datalen);
 885
 886         memcpy(new_epayload->iv, epayload->iv, ivsize);
 887         memcpy(new_epayload->payload_data, epayload->payload_data,
 888                epayload->payload_datalen);
 889
 890         rcu_assign_keypointer(key, new_epayload);
 891         call_rcu(&epayload->rcu, encrypted_rcu_free);
 892 out:
 893         kzfree(buf);
 894         return ret;
 895 }
 896
 897 /*
 898  * encrypted_read - format and copy the encrypted data to userspace
 899  *
 900  * The resulting datablob format is:
 901  * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
 902  *
 903  * On success, return to userspace the encrypted key datablob size.
 904  */
 905 static long encrypted_read(const struct key *key, char __user *buffer,
 906                            size_t buflen)
 907 {
 908         struct encrypted_key_payload *epayload;
 909         struct key *mkey;
 910         const u8 *master_key;
 911         size_t master_keylen;
 912         char derived_key[HASH_SIZE];
 913         char *ascii_buf;
 914         size_t asciiblob_len;
 915         int ret;
 916
 917         epayload = dereference_key_locked(key);
 918
 919         /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
 920         asciiblob_len = epayload->datablob_len + ivsize + 1
 921             + roundup(epayload->decrypted_datalen, blksize)
 922             + (HASH_SIZE * 2);
 923
 924         if (!buffer || buflen < asciiblob_len)
 925                 return asciiblob_len;
 926
 927         mkey = request_master_key(epayload, &master_key, &master_keylen);
 928         if (IS_ERR(mkey))
 929                 return PTR_ERR(mkey);
 930
 931         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 932         if (ret < 0)
 933                 goto out;
 934
 935         ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
 936         if (ret < 0)
 937                 goto out;
 938
 939         ret = datablob_hmac_append(epayload, master_key, master_keylen);
 940         if (ret < 0)
 941                 goto out;
 942
 943         ascii_buf = datablob_format(epayload, asciiblob_len);
 944         if (!ascii_buf) {
 945                 ret = -ENOMEM;
 946                 goto out;
 947         }
 948
 949         up_read(&mkey->sem);
 950         key_put(mkey);
 951         memzero_explicit(derived_key, sizeof(derived_key));
 952
 953         if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0)
 954                 ret = -EFAULT;
 955         kzfree(ascii_buf);
 956
 957         return asciiblob_len;
 958 out:
 959         up_read(&mkey->sem);
 960         key_put(mkey);
 961         memzero_explicit(derived_key, sizeof(derived_key));
 962         return ret;
 963 }
 964
 965 /*
 966  * encrypted_destroy - clear and free the key's payload
 967  */
 968 static void encrypted_destroy(struct key *key)
 969 {
 970         kzfree(key->payload.data[0]);
 971 }
 972
 973 struct key_type key_type_encrypted = {
 974         .name = "encrypted",
 975         .instantiate = encrypted_instantiate,
 976         .update = encrypted_update,
 977         .destroy = encrypted_destroy,
 978         .describe = user_describe,
 979         .read = encrypted_read,
 980 };
 981 EXPORT_SYMBOL_GPL(key_type_encrypted);
 982
 983 static int __init init_encrypted(void)
 984 {
 985         int ret;
 986
 987         hash_tfm = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC);
 988         if (IS_ERR(hash_tfm)) {
 989                 pr_err("encrypted_key: can't allocate %s transform: %ld\n",
 990                        hash_alg, PTR_ERR(hash_tfm));
 991                 return PTR_ERR(hash_tfm);
 992         }
 993
 994         ret = aes_get_sizes();
 995         if (ret < 0)
 996                 goto out;
 997         ret = register_key_type(&key_type_encrypted);
 998         if (ret < 0)
 999                 goto out;
1000         return 0;
1001 out:
1002         crypto_free_shash(hash_tfm);
1003         return ret;
1004
1005 }
1006
1007 static void __exit cleanup_encrypted(void)
1008 {
1009         crypto_free_shash(hash_tfm);
1010         unregister_key_type(&key_type_encrypted);
1011 }
1012
1013 late_initcall(init_encrypted);
1014 module_exit(cleanup_encrypted);
1015
1016 MODULE_LICENSE("GPL");