security/keys/encrypted-keys/encrypted.c

/* [<][>][^][v][top][bottom][index][help] */
This source file includes following definitions.
aes_get_sizes
valid_ecryptfs_desc
valid_master_desc
datablob_parse
datablob_format
request_user_key
calc_hash
calc_hmac
get_derived_key
init_skcipher_req
request_master_key
derived_key_encrypt
datablob_hmac_append
datablob_hmac_verify
derived_key_decrypt
encrypted_key_alloc
encrypted_key_decrypt
__ekey_init
encrypted_init
encrypted_instantiate
encrypted_rcu_free
encrypted_update
encrypted_read
encrypted_destroy
init_encrypted
cleanup_encrypted
   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 -- http://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/sha.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_hash(struct crypto_shash *tfm, u8 *digest,
 327                      const u8 *buf, unsigned int buflen)
 328 {
 329         SHASH_DESC_ON_STACK(desc, tfm);
 330         int err;
 331 
 332         desc->tfm = tfm;
 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, 0);
 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) {
 629                 if (!strcmp(format, key_format_ecryptfs)) {
 630                         if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
 631                                 pr_err("encrypted_key: keylen for the ecryptfs format 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                 } else if (!strcmp(format, key_format_enc32)) {
 638                         if (decrypted_datalen != KEY_ENC32_PAYLOAD_LEN) {
 639                                 pr_err("encrypted_key: enc32 key payload incorrect length: %d\n",
 640                                                 decrypted_datalen);
 641                                 return ERR_PTR(-EINVAL);
 642                         }
 643                 }
 644         }
 645 
 646         encrypted_datalen = roundup(decrypted_datalen, blksize);
 647 
 648         datablob_len = format_len + 1 + strlen(master_desc) + 1
 649             + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
 650 
 651         ret = key_payload_reserve(key, payload_datalen + datablob_len
 652                                   + HASH_SIZE + 1);
 653         if (ret < 0)
 654                 return ERR_PTR(ret);
 655 
 656         epayload = kzalloc(sizeof(*epayload) + payload_datalen +
 657                            datablob_len + HASH_SIZE + 1, GFP_KERNEL);
 658         if (!epayload)
 659                 return ERR_PTR(-ENOMEM);
 660 
 661         epayload->payload_datalen = payload_datalen;
 662         epayload->decrypted_datalen = decrypted_datalen;
 663         epayload->datablob_len = datablob_len;
 664         return epayload;
 665 }
 666 
 667 static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
 668                                  const char *format, const char *hex_encoded_iv)
 669 {
 670         struct key *mkey;
 671         u8 derived_key[HASH_SIZE];
 672         const u8 *master_key;
 673         u8 *hmac;
 674         const char *hex_encoded_data;
 675         unsigned int encrypted_datalen;
 676         size_t master_keylen;
 677         size_t asciilen;
 678         int ret;
 679 
 680         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 681         asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
 682         if (strlen(hex_encoded_iv) != asciilen)
 683                 return -EINVAL;
 684 
 685         hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
 686         ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
 687         if (ret < 0)
 688                 return -EINVAL;
 689         ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
 690                       encrypted_datalen);
 691         if (ret < 0)
 692                 return -EINVAL;
 693 
 694         hmac = epayload->format + epayload->datablob_len;
 695         ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
 696                       HASH_SIZE);
 697         if (ret < 0)
 698                 return -EINVAL;
 699 
 700         mkey = request_master_key(epayload, &master_key, &master_keylen);
 701         if (IS_ERR(mkey))
 702                 return PTR_ERR(mkey);
 703 
 704         ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
 705         if (ret < 0) {
 706                 pr_err("encrypted_key: bad hmac (%d)\n", ret);
 707                 goto out;
 708         }
 709 
 710         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 711         if (ret < 0)
 712                 goto out;
 713 
 714         ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
 715         if (ret < 0)
 716                 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
 717 out:
 718         up_read(&mkey->sem);
 719         key_put(mkey);
 720         memzero_explicit(derived_key, sizeof(derived_key));
 721         return ret;
 722 }
 723 
 724 static void __ekey_init(struct encrypted_key_payload *epayload,
 725                         const char *format, const char *master_desc,
 726                         const char *datalen)
 727 {
 728         unsigned int format_len;
 729 
 730         format_len = (!format) ? strlen(key_format_default) : strlen(format);
 731         epayload->format = epayload->payload_data + epayload->payload_datalen;
 732         epayload->master_desc = epayload->format + format_len + 1;
 733         epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
 734         epayload->iv = epayload->datalen + strlen(datalen) + 1;
 735         epayload->encrypted_data = epayload->iv + ivsize + 1;
 736         epayload->decrypted_data = epayload->payload_data;
 737 
 738         if (!format)
 739                 memcpy(epayload->format, key_format_default, format_len);
 740         else {
 741                 if (!strcmp(format, key_format_ecryptfs))
 742                         epayload->decrypted_data =
 743                                 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
 744 
 745                 memcpy(epayload->format, format, format_len);
 746         }
 747 
 748         memcpy(epayload->master_desc, master_desc, strlen(master_desc));
 749         memcpy(epayload->datalen, datalen, strlen(datalen));
 750 }
 751 
 752 /*
 753  * encrypted_init - initialize an encrypted key
 754  *
 755  * For a new key, use a random number for both the iv and data
 756  * itself.  For an old key, decrypt the hex encoded data.
 757  */
 758 static int encrypted_init(struct encrypted_key_payload *epayload,
 759                           const char *key_desc, const char *format,
 760                           const char *master_desc, const char *datalen,
 761                           const char *hex_encoded_iv)
 762 {
 763         int ret = 0;
 764 
 765         if (format && !strcmp(format, key_format_ecryptfs)) {
 766                 ret = valid_ecryptfs_desc(key_desc);
 767                 if (ret < 0)
 768                         return ret;
 769 
 770                 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
 771                                        key_desc);
 772         }
 773 
 774         __ekey_init(epayload, format, master_desc, datalen);
 775         if (!hex_encoded_iv) {
 776                 get_random_bytes(epayload->iv, ivsize);
 777 
 778                 get_random_bytes(epayload->decrypted_data,
 779                                  epayload->decrypted_datalen);
 780         } else
 781                 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
 782         return ret;
 783 }
 784 
 785 /*
 786  * encrypted_instantiate - instantiate an encrypted key
 787  *
 788  * Decrypt an existing encrypted datablob or create a new encrypted key
 789  * based on a kernel random number.
 790  *
 791  * On success, return 0. Otherwise return errno.
 792  */
 793 static int encrypted_instantiate(struct key *key,
 794                                  struct key_preparsed_payload *prep)
 795 {
 796         struct encrypted_key_payload *epayload = NULL;
 797         char *datablob = NULL;
 798         const char *format = NULL;
 799         char *master_desc = NULL;
 800         char *decrypted_datalen = NULL;
 801         char *hex_encoded_iv = NULL;
 802         size_t datalen = prep->datalen;
 803         int ret;
 804 
 805         if (datalen <= 0 || datalen > 32767 || !prep->data)
 806                 return -EINVAL;
 807 
 808         datablob = kmalloc(datalen + 1, GFP_KERNEL);
 809         if (!datablob)
 810                 return -ENOMEM;
 811         datablob[datalen] = 0;
 812         memcpy(datablob, prep->data, datalen);
 813         ret = datablob_parse(datablob, &format, &master_desc,
 814                              &decrypted_datalen, &hex_encoded_iv);
 815         if (ret < 0)
 816                 goto out;
 817 
 818         epayload = encrypted_key_alloc(key, format, master_desc,
 819                                        decrypted_datalen);
 820         if (IS_ERR(epayload)) {
 821                 ret = PTR_ERR(epayload);
 822                 goto out;
 823         }
 824         ret = encrypted_init(epayload, key->description, format, master_desc,
 825                              decrypted_datalen, hex_encoded_iv);
 826         if (ret < 0) {
 827                 kzfree(epayload);
 828                 goto out;
 829         }
 830 
 831         rcu_assign_keypointer(key, epayload);
 832 out:
 833         kzfree(datablob);
 834         return ret;
 835 }
 836 
 837 static void encrypted_rcu_free(struct rcu_head *rcu)
 838 {
 839         struct encrypted_key_payload *epayload;
 840 
 841         epayload = container_of(rcu, struct encrypted_key_payload, rcu);
 842         kzfree(epayload);
 843 }
 844 
 845 /*
 846  * encrypted_update - update the master key description
 847  *
 848  * Change the master key description for an existing encrypted key.
 849  * The next read will return an encrypted datablob using the new
 850  * master key description.
 851  *
 852  * On success, return 0. Otherwise return errno.
 853  */
 854 static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
 855 {
 856         struct encrypted_key_payload *epayload = key->payload.data[0];
 857         struct encrypted_key_payload *new_epayload;
 858         char *buf;
 859         char *new_master_desc = NULL;
 860         const char *format = NULL;
 861         size_t datalen = prep->datalen;
 862         int ret = 0;
 863 
 864         if (key_is_negative(key))
 865                 return -ENOKEY;
 866         if (datalen <= 0 || datalen > 32767 || !prep->data)
 867                 return -EINVAL;
 868 
 869         buf = kmalloc(datalen + 1, GFP_KERNEL);
 870         if (!buf)
 871                 return -ENOMEM;
 872 
 873         buf[datalen] = 0;
 874         memcpy(buf, prep->data, datalen);
 875         ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
 876         if (ret < 0)
 877                 goto out;
 878 
 879         ret = valid_master_desc(new_master_desc, epayload->master_desc);
 880         if (ret < 0)
 881                 goto out;
 882 
 883         new_epayload = encrypted_key_alloc(key, epayload->format,
 884                                            new_master_desc, epayload->datalen);
 885         if (IS_ERR(new_epayload)) {
 886                 ret = PTR_ERR(new_epayload);
 887                 goto out;
 888         }
 889 
 890         __ekey_init(new_epayload, epayload->format, new_master_desc,
 891                     epayload->datalen);
 892 
 893         memcpy(new_epayload->iv, epayload->iv, ivsize);
 894         memcpy(new_epayload->payload_data, epayload->payload_data,
 895                epayload->payload_datalen);
 896 
 897         rcu_assign_keypointer(key, new_epayload);
 898         call_rcu(&epayload->rcu, encrypted_rcu_free);
 899 out:
 900         kzfree(buf);
 901         return ret;
 902 }
 903 
 904 /*
 905  * encrypted_read - format and copy out the encrypted data
 906  *
 907  * The resulting datablob format is:
 908  * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
 909  *
 910  * On success, return to userspace the encrypted key datablob size.
 911  */
 912 static long encrypted_read(const struct key *key, char *buffer,
 913                            size_t buflen)
 914 {
 915         struct encrypted_key_payload *epayload;
 916         struct key *mkey;
 917         const u8 *master_key;
 918         size_t master_keylen;
 919         char derived_key[HASH_SIZE];
 920         char *ascii_buf;
 921         size_t asciiblob_len;
 922         int ret;
 923 
 924         epayload = dereference_key_locked(key);
 925 
 926         /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
 927         asciiblob_len = epayload->datablob_len + ivsize + 1
 928             + roundup(epayload->decrypted_datalen, blksize)
 929             + (HASH_SIZE * 2);
 930 
 931         if (!buffer || buflen < asciiblob_len)
 932                 return asciiblob_len;
 933 
 934         mkey = request_master_key(epayload, &master_key, &master_keylen);
 935         if (IS_ERR(mkey))
 936                 return PTR_ERR(mkey);
 937 
 938         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 939         if (ret < 0)
 940                 goto out;
 941 
 942         ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
 943         if (ret < 0)
 944                 goto out;
 945 
 946         ret = datablob_hmac_append(epayload, master_key, master_keylen);
 947         if (ret < 0)
 948                 goto out;
 949 
 950         ascii_buf = datablob_format(epayload, asciiblob_len);
 951         if (!ascii_buf) {
 952                 ret = -ENOMEM;
 953                 goto out;
 954         }
 955 
 956         up_read(&mkey->sem);
 957         key_put(mkey);
 958         memzero_explicit(derived_key, sizeof(derived_key));
 959 
 960         memcpy(buffer, ascii_buf, asciiblob_len);
 961         kzfree(ascii_buf);
 962 
 963         return asciiblob_len;
 964 out:
 965         up_read(&mkey->sem);
 966         key_put(mkey);
 967         memzero_explicit(derived_key, sizeof(derived_key));
 968         return ret;
 969 }
 970 
 971 /*
 972  * encrypted_destroy - clear and free the key's payload
 973  */
 974 static void encrypted_destroy(struct key *key)
 975 {
 976         kzfree(key->payload.data[0]);
 977 }
 978 
 979 struct key_type key_type_encrypted = {
 980         .name = "encrypted",
 981         .instantiate = encrypted_instantiate,
 982         .update = encrypted_update,
 983         .destroy = encrypted_destroy,
 984         .describe = user_describe,
 985         .read = encrypted_read,
 986 };
 987 EXPORT_SYMBOL_GPL(key_type_encrypted);
 988 
 989 static int __init init_encrypted(void)
 990 {
 991         int ret;
 992 
 993         hash_tfm = crypto_alloc_shash(hash_alg, 0, 0);
 994         if (IS_ERR(hash_tfm)) {
 995                 pr_err("encrypted_key: can't allocate %s transform: %ld\n",
 996                        hash_alg, PTR_ERR(hash_tfm));
 997                 return PTR_ERR(hash_tfm);
 998         }
 999 
1000         ret = aes_get_sizes();
1001         if (ret < 0)
1002                 goto out;
1003         ret = register_key_type(&key_type_encrypted);
1004         if (ret < 0)
1005                 goto out;
1006         return 0;
1007 out:
1008         crypto_free_shash(hash_tfm);
1009         return ret;
1010 
1011 }
1012 
1013 static void __exit cleanup_encrypted(void)
1014 {
1015         crypto_free_shash(hash_tfm);
1016         unregister_key_type(&key_type_encrypted);
1017 }
1018 
1019 late_initcall(init_encrypted);
1020 module_exit(cleanup_encrypted);
1021 
1022 MODULE_LICENSE("GPL");
/* [<][>][^][v][top][bottom][index][help] */
root/security/keys/encrypted-keys/encrypted.c

DEFINITIONS
