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.txt
  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/hash.h>
  34 #include <crypto/sha.h>
  35 #include <crypto/skcipher.h>
  36
  37 #include "encrypted.h"
  38 #include "ecryptfs_format.h"
  39
  40 static const char KEY_TRUSTED_PREFIX[] = "trusted:";
  41 static const char KEY_USER_PREFIX[] = "user:";
  42 static const char hash_alg[] = "sha256";
  43 static const char hmac_alg[] = "hmac(sha256)";
  44 static const char blkcipher_alg[] = "cbc(aes)";
  45 static const char key_format_default[] = "default";
  46 static const char key_format_ecryptfs[] = "ecryptfs";
  47 static unsigned int ivsize;
  48 static int blksize;
  49
  50 #define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
  51 #define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
  52 #define KEY_ECRYPTFS_DESC_LEN 16
  53 #define HASH_SIZE SHA256_DIGEST_SIZE
  54 #define MAX_DATA_SIZE 4096
  55 #define MIN_DATA_SIZE  20
  56
  57 struct sdesc {
  58         struct shash_desc shash;
  59         char ctx[];
  60 };
  61
  62 static struct crypto_shash *hashalg;
  63 static struct crypto_shash *hmacalg;
  64
  65 enum {
  66         Opt_err = -1, Opt_new, Opt_load, Opt_update
  67 };
  68
  69 enum {
  70         Opt_error = -1, Opt_default, Opt_ecryptfs
  71 };
  72
  73 static const match_table_t key_format_tokens = {
  74         {Opt_default, "default"},
  75         {Opt_ecryptfs, "ecryptfs"},
  76         {Opt_error, NULL}
  77 };
  78
  79 static const match_table_t key_tokens = {
  80         {Opt_new, "new"},
  81         {Opt_load, "load"},
  82         {Opt_update, "update"},
  83         {Opt_err, NULL}
  84 };
  85
  86 static int aes_get_sizes(void)
  87 {
  88         struct crypto_skcipher *tfm;
  89
  90         tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
  91         if (IS_ERR(tfm)) {
  92                 pr_err("encrypted_key: failed to alloc_cipher (%ld)\n",
  93                        PTR_ERR(tfm));
  94                 return PTR_ERR(tfm);
  95         }
  96         ivsize = crypto_skcipher_ivsize(tfm);
  97         blksize = crypto_skcipher_blocksize(tfm);
  98         crypto_free_skcipher(tfm);
  99         return 0;
 100 }
 101
 102 /*
 103  * valid_ecryptfs_desc - verify the description of a new/loaded encrypted key
 104  *
 105  * The description of a encrypted key with format 'ecryptfs' must contain
 106  * exactly 16 hexadecimal characters.
 107  *
 108  */
 109 static int valid_ecryptfs_desc(const char *ecryptfs_desc)
 110 {
 111         int i;
 112
 113         if (strlen(ecryptfs_desc) != KEY_ECRYPTFS_DESC_LEN) {
 114                 pr_err("encrypted_key: key description must be %d hexadecimal "
 115                        "characters long\n", KEY_ECRYPTFS_DESC_LEN);
 116                 return -EINVAL;
 117         }
 118
 119         for (i = 0; i < KEY_ECRYPTFS_DESC_LEN; i++) {
 120                 if (!isxdigit(ecryptfs_desc[i])) {
 121                         pr_err("encrypted_key: key description must contain "
 122                                "only hexadecimal characters\n");
 123                         return -EINVAL;
 124                 }
 125         }
 126
 127         return 0;
 128 }
 129
 130 /*
 131  * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key
 132  *
 133  * key-type:= "trusted:" | "user:"
 134  * desc:= master-key description
 135  *
 136  * Verify that 'key-type' is valid and that 'desc' exists. On key update,
 137  * only the master key description is permitted to change, not the key-type.
 138  * The key-type remains constant.
 139  *
 140  * On success returns 0, otherwise -EINVAL.
 141  */
 142 static int valid_master_desc(const char *new_desc, const char *orig_desc)
 143 {
 144         int prefix_len;
 145
 146         if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN))
 147                 prefix_len = KEY_TRUSTED_PREFIX_LEN;
 148         else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN))
 149                 prefix_len = KEY_USER_PREFIX_LEN;
 150         else
 151                 return -EINVAL;
 152
 153         if (!new_desc[prefix_len])
 154                 return -EINVAL;
 155
 156         if (orig_desc && strncmp(new_desc, orig_desc, prefix_len))
 157                 return -EINVAL;
 158
 159         return 0;
 160 }
 161
 162 /*
 163  * datablob_parse - parse the keyctl data
 164  *
 165  * datablob format:
 166  * new [<format>] <master-key name> <decrypted data length>
 167  * load [<format>] <master-key name> <decrypted data length>
 168  *     <encrypted iv + data>
 169  * update <new-master-key name>
 170  *
 171  * Tokenizes a copy of the keyctl data, returning a pointer to each token,
 172  * which is null terminated.
 173  *
 174  * On success returns 0, otherwise -EINVAL.
 175  */
 176 static int datablob_parse(char *datablob, const char **format,
 177                           char **master_desc, char **decrypted_datalen,
 178                           char **hex_encoded_iv)
 179 {
 180         substring_t args[MAX_OPT_ARGS];
 181         int ret = -EINVAL;
 182         int key_cmd;
 183         int key_format;
 184         char *p, *keyword;
 185
 186         keyword = strsep(&datablob, " \t");
 187         if (!keyword) {
 188                 pr_info("encrypted_key: insufficient parameters specified\n");
 189                 return ret;
 190         }
 191         key_cmd = match_token(keyword, key_tokens, args);
 192
 193         /* Get optional format: default | ecryptfs */
 194         p = strsep(&datablob, " \t");
 195         if (!p) {
 196                 pr_err("encrypted_key: insufficient parameters specified\n");
 197                 return ret;
 198         }
 199
 200         key_format = match_token(p, key_format_tokens, args);
 201         switch (key_format) {
 202         case Opt_ecryptfs:
 203         case Opt_default:
 204                 *format = p;
 205                 *master_desc = strsep(&datablob, " \t");
 206                 break;
 207         case Opt_error:
 208                 *master_desc = p;
 209                 break;
 210         }
 211
 212         if (!*master_desc) {
 213                 pr_info("encrypted_key: master key parameter is missing\n");
 214                 goto out;
 215         }
 216
 217         if (valid_master_desc(*master_desc, NULL) < 0) {
 218                 pr_info("encrypted_key: master key parameter \'%s\' "
 219                         "is invalid\n", *master_desc);
 220                 goto out;
 221         }
 222
 223         if (decrypted_datalen) {
 224                 *decrypted_datalen = strsep(&datablob, " \t");
 225                 if (!*decrypted_datalen) {
 226                         pr_info("encrypted_key: keylen parameter is missing\n");
 227                         goto out;
 228                 }
 229         }
 230
 231         switch (key_cmd) {
 232         case Opt_new:
 233                 if (!decrypted_datalen) {
 234                         pr_info("encrypted_key: keyword \'%s\' not allowed "
 235                                 "when called from .update method\n", keyword);
 236                         break;
 237                 }
 238                 ret = 0;
 239                 break;
 240         case Opt_load:
 241                 if (!decrypted_datalen) {
 242                         pr_info("encrypted_key: keyword \'%s\' not allowed "
 243                                 "when called from .update method\n", keyword);
 244                         break;
 245                 }
 246                 *hex_encoded_iv = strsep(&datablob, " \t");
 247                 if (!*hex_encoded_iv) {
 248                         pr_info("encrypted_key: hex blob is missing\n");
 249                         break;
 250                 }
 251                 ret = 0;
 252                 break;
 253         case Opt_update:
 254                 if (decrypted_datalen) {
 255                         pr_info("encrypted_key: keyword \'%s\' not allowed "
 256                                 "when called from .instantiate method\n",
 257                                 keyword);
 258                         break;
 259                 }
 260                 ret = 0;
 261                 break;
 262         case Opt_err:
 263                 pr_info("encrypted_key: keyword \'%s\' not recognized\n",
 264                         keyword);
 265                 break;
 266         }
 267 out:
 268         return ret;
 269 }
 270
 271 /*
 272  * datablob_format - format as an ascii string, before copying to userspace
 273  */
 274 static char *datablob_format(struct encrypted_key_payload *epayload,
 275                              size_t asciiblob_len)
 276 {
 277         char *ascii_buf, *bufp;
 278         u8 *iv = epayload->iv;
 279         int len;
 280         int i;
 281
 282         ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
 283         if (!ascii_buf)
 284                 goto out;
 285
 286         ascii_buf[asciiblob_len] = '\0';
 287
 288         /* copy datablob master_desc and datalen strings */
 289         len = sprintf(ascii_buf, "%s %s %s ", epayload->format,
 290                       epayload->master_desc, epayload->datalen);
 291
 292         /* convert the hex encoded iv, encrypted-data and HMAC to ascii */
 293         bufp = &ascii_buf[len];
 294         for (i = 0; i < (asciiblob_len - len) / 2; i++)
 295                 bufp = hex_byte_pack(bufp, iv[i]);
 296 out:
 297         return ascii_buf;
 298 }
 299
 300 /*
 301  * request_user_key - request the user key
 302  *
 303  * Use a user provided key to encrypt/decrypt an encrypted-key.
 304  */
 305 static struct key *request_user_key(const char *master_desc, const u8 **master_key,
 306                                     size_t *master_keylen)
 307 {
 308         const struct user_key_payload *upayload;
 309         struct key *ukey;
 310
 311         ukey = request_key(&key_type_user, master_desc, NULL);
 312         if (IS_ERR(ukey))
 313                 goto error;
 314
 315         down_read(&ukey->sem);
 316         upayload = user_key_payload(ukey);
 317         if (!upayload) {
 318                 /* key was revoked before we acquired its semaphore */
 319                 up_read(&ukey->sem);
 320                 key_put(ukey);
 321                 ukey = ERR_PTR(-EKEYREVOKED);
 322                 goto error;
 323         }
 324         *master_key = upayload->data;
 325         *master_keylen = upayload->datalen;
 326 error:
 327         return ukey;
 328 }
 329
 330 static struct sdesc *alloc_sdesc(struct crypto_shash *alg)
 331 {
 332         struct sdesc *sdesc;
 333         int size;
 334
 335         size = sizeof(struct shash_desc) + crypto_shash_descsize(alg);
 336         sdesc = kmalloc(size, GFP_KERNEL);
 337         if (!sdesc)
 338                 return ERR_PTR(-ENOMEM);
 339         sdesc->shash.tfm = alg;
 340         sdesc->shash.flags = 0x0;
 341         return sdesc;
 342 }
 343
 344 static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
 345                      const u8 *buf, unsigned int buflen)
 346 {
 347         struct sdesc *sdesc;
 348         int ret;
 349
 350         sdesc = alloc_sdesc(hmacalg);
 351         if (IS_ERR(sdesc)) {
 352                 pr_info("encrypted_key: can't alloc %s\n", hmac_alg);
 353                 return PTR_ERR(sdesc);
 354         }
 355
 356         ret = crypto_shash_setkey(hmacalg, key, keylen);
 357         if (!ret)
 358                 ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest);
 359         kfree(sdesc);
 360         return ret;
 361 }
 362
 363 static int calc_hash(u8 *digest, const u8 *buf, unsigned int buflen)
 364 {
 365         struct sdesc *sdesc;
 366         int ret;
 367
 368         sdesc = alloc_sdesc(hashalg);
 369         if (IS_ERR(sdesc)) {
 370                 pr_info("encrypted_key: can't alloc %s\n", hash_alg);
 371                 return PTR_ERR(sdesc);
 372         }
 373
 374         ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest);
 375         kfree(sdesc);
 376         return ret;
 377 }
 378
 379 enum derived_key_type { ENC_KEY, AUTH_KEY };
 380
 381 /* Derive authentication/encryption key from trusted key */
 382 static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
 383                            const u8 *master_key, size_t master_keylen)
 384 {
 385         u8 *derived_buf;
 386         unsigned int derived_buf_len;
 387         int ret;
 388
 389         derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
 390         if (derived_buf_len < HASH_SIZE)
 391                 derived_buf_len = HASH_SIZE;
 392
 393         derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
 394         if (!derived_buf) {
 395                 pr_err("encrypted_key: out of memory\n");
 396                 return -ENOMEM;
 397         }
 398         if (key_type)
 399                 strcpy(derived_buf, "AUTH_KEY");
 400         else
 401                 strcpy(derived_buf, "ENC_KEY");
 402
 403         memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
 404                master_keylen);
 405         ret = calc_hash(derived_key, derived_buf, derived_buf_len);
 406         kfree(derived_buf);
 407         return ret;
 408 }
 409
 410 static struct skcipher_request *init_skcipher_req(const u8 *key,
 411                                                   unsigned int key_len)
 412 {
 413         struct skcipher_request *req;
 414         struct crypto_skcipher *tfm;
 415         int ret;
 416
 417         tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
 418         if (IS_ERR(tfm)) {
 419                 pr_err("encrypted_key: failed to load %s transform (%ld)\n",
 420                        blkcipher_alg, PTR_ERR(tfm));
 421                 return ERR_CAST(tfm);
 422         }
 423
 424         ret = crypto_skcipher_setkey(tfm, key, key_len);
 425         if (ret < 0) {
 426                 pr_err("encrypted_key: failed to setkey (%d)\n", ret);
 427                 crypto_free_skcipher(tfm);
 428                 return ERR_PTR(ret);
 429         }
 430
 431         req = skcipher_request_alloc(tfm, GFP_KERNEL);
 432         if (!req) {
 433                 pr_err("encrypted_key: failed to allocate request for %s\n",
 434                        blkcipher_alg);
 435                 crypto_free_skcipher(tfm);
 436                 return ERR_PTR(-ENOMEM);
 437         }
 438
 439         skcipher_request_set_callback(req, 0, NULL, NULL);
 440         return req;
 441 }
 442
 443 static struct key *request_master_key(struct encrypted_key_payload *epayload,
 444                                       const u8 **master_key, size_t *master_keylen)
 445 {
 446         struct key *mkey = ERR_PTR(-EINVAL);
 447
 448         if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
 449                      KEY_TRUSTED_PREFIX_LEN)) {
 450                 mkey = request_trusted_key(epayload->master_desc +
 451                                            KEY_TRUSTED_PREFIX_LEN,
 452                                            master_key, master_keylen);
 453         } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
 454                             KEY_USER_PREFIX_LEN)) {
 455                 mkey = request_user_key(epayload->master_desc +
 456                                         KEY_USER_PREFIX_LEN,
 457                                         master_key, master_keylen);
 458         } else
 459                 goto out;
 460
 461         if (IS_ERR(mkey)) {
 462                 int ret = PTR_ERR(mkey);
 463
 464                 if (ret == -ENOTSUPP)
 465                         pr_info("encrypted_key: key %s not supported",
 466                                 epayload->master_desc);
 467                 else
 468                         pr_info("encrypted_key: key %s not found",
 469                                 epayload->master_desc);
 470                 goto out;
 471         }
 472
 473         dump_master_key(*master_key, *master_keylen);
 474 out:
 475         return mkey;
 476 }
 477
 478 /* Before returning data to userspace, encrypt decrypted data. */
 479 static int derived_key_encrypt(struct encrypted_key_payload *epayload,
 480                                const u8 *derived_key,
 481                                unsigned int derived_keylen)
 482 {
 483         struct scatterlist sg_in[2];
 484         struct scatterlist sg_out[1];
 485         struct crypto_skcipher *tfm;
 486         struct skcipher_request *req;
 487         unsigned int encrypted_datalen;
 488         u8 iv[AES_BLOCK_SIZE];
 489         int ret;
 490
 491         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 492
 493         req = init_skcipher_req(derived_key, derived_keylen);
 494         ret = PTR_ERR(req);
 495         if (IS_ERR(req))
 496                 goto out;
 497         dump_decrypted_data(epayload);
 498
 499         sg_init_table(sg_in, 2);
 500         sg_set_buf(&sg_in[0], epayload->decrypted_data,
 501                    epayload->decrypted_datalen);
 502         sg_set_page(&sg_in[1], ZERO_PAGE(0), AES_BLOCK_SIZE, 0);
 503
 504         sg_init_table(sg_out, 1);
 505         sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
 506
 507         memcpy(iv, epayload->iv, sizeof(iv));
 508         skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
 509         ret = crypto_skcipher_encrypt(req);
 510         tfm = crypto_skcipher_reqtfm(req);
 511         skcipher_request_free(req);
 512         crypto_free_skcipher(tfm);
 513         if (ret < 0)
 514                 pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
 515         else
 516                 dump_encrypted_data(epayload, encrypted_datalen);
 517 out:
 518         return ret;
 519 }
 520
 521 static int datablob_hmac_append(struct encrypted_key_payload *epayload,
 522                                 const u8 *master_key, size_t master_keylen)
 523 {
 524         u8 derived_key[HASH_SIZE];
 525         u8 *digest;
 526         int ret;
 527
 528         ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 529         if (ret < 0)
 530                 goto out;
 531
 532         digest = epayload->format + epayload->datablob_len;
 533         ret = calc_hmac(digest, derived_key, sizeof derived_key,
 534                         epayload->format, epayload->datablob_len);
 535         if (!ret)
 536                 dump_hmac(NULL, digest, HASH_SIZE);
 537 out:
 538         return ret;
 539 }
 540
 541 /* verify HMAC before decrypting encrypted key */
 542 static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
 543                                 const u8 *format, const u8 *master_key,
 544                                 size_t master_keylen)
 545 {
 546         u8 derived_key[HASH_SIZE];
 547         u8 digest[HASH_SIZE];
 548         int ret;
 549         char *p;
 550         unsigned short len;
 551
 552         ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 553         if (ret < 0)
 554                 goto out;
 555
 556         len = epayload->datablob_len;
 557         if (!format) {
 558                 p = epayload->master_desc;
 559                 len -= strlen(epayload->format) + 1;
 560         } else
 561                 p = epayload->format;
 562
 563         ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
 564         if (ret < 0)
 565                 goto out;
 566         ret = memcmp(digest, epayload->format + epayload->datablob_len,
 567                      sizeof digest);
 568         if (ret) {
 569                 ret = -EINVAL;
 570                 dump_hmac("datablob",
 571                           epayload->format + epayload->datablob_len,
 572                           HASH_SIZE);
 573                 dump_hmac("calc", digest, HASH_SIZE);
 574         }
 575 out:
 576         return ret;
 577 }
 578
 579 static int derived_key_decrypt(struct encrypted_key_payload *epayload,
 580                                const u8 *derived_key,
 581                                unsigned int derived_keylen)
 582 {
 583         struct scatterlist sg_in[1];
 584         struct scatterlist sg_out[2];
 585         struct crypto_skcipher *tfm;
 586         struct skcipher_request *req;
 587         unsigned int encrypted_datalen;
 588         u8 iv[AES_BLOCK_SIZE];
 589         u8 *pad;
 590         int ret;
 591
 592         /* Throwaway buffer to hold the unused zero padding at the end */
 593         pad = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
 594         if (!pad)
 595                 return -ENOMEM;
 596
 597         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 598         req = init_skcipher_req(derived_key, derived_keylen);
 599         ret = PTR_ERR(req);
 600         if (IS_ERR(req))
 601                 goto out;
 602         dump_encrypted_data(epayload, encrypted_datalen);
 603
 604         sg_init_table(sg_in, 1);
 605         sg_init_table(sg_out, 2);
 606         sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
 607         sg_set_buf(&sg_out[0], epayload->decrypted_data,
 608                    epayload->decrypted_datalen);
 609         sg_set_buf(&sg_out[1], pad, AES_BLOCK_SIZE);
 610
 611         memcpy(iv, epayload->iv, sizeof(iv));
 612         skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
 613         ret = crypto_skcipher_decrypt(req);
 614         tfm = crypto_skcipher_reqtfm(req);
 615         skcipher_request_free(req);
 616         crypto_free_skcipher(tfm);
 617         if (ret < 0)
 618                 goto out;
 619         dump_decrypted_data(epayload);
 620 out:
 621         kfree(pad);
 622         return ret;
 623 }
 624
 625 /* Allocate memory for decrypted key and datablob. */
 626 static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
 627                                                          const char *format,
 628                                                          const char *master_desc,
 629                                                          const char *datalen)
 630 {
 631         struct encrypted_key_payload *epayload = NULL;
 632         unsigned short datablob_len;
 633         unsigned short decrypted_datalen;
 634         unsigned short payload_datalen;
 635         unsigned int encrypted_datalen;
 636         unsigned int format_len;
 637         long dlen;
 638         int ret;
 639
 640         ret = kstrtol(datalen, 10, &dlen);
 641         if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
 642                 return ERR_PTR(-EINVAL);
 643
 644         format_len = (!format) ? strlen(key_format_default) : strlen(format);
 645         decrypted_datalen = dlen;
 646         payload_datalen = decrypted_datalen;
 647         if (format && !strcmp(format, key_format_ecryptfs)) {
 648                 if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
 649                         pr_err("encrypted_key: keylen for the ecryptfs format "
 650                                "must be equal to %d bytes\n",
 651                                ECRYPTFS_MAX_KEY_BYTES);
 652                         return ERR_PTR(-EINVAL);
 653                 }
 654                 decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
 655                 payload_datalen = sizeof(struct ecryptfs_auth_tok);
 656         }
 657
 658         encrypted_datalen = roundup(decrypted_datalen, blksize);
 659
 660         datablob_len = format_len + 1 + strlen(master_desc) + 1
 661             + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
 662
 663         ret = key_payload_reserve(key, payload_datalen + datablob_len
 664                                   + HASH_SIZE + 1);
 665         if (ret < 0)
 666                 return ERR_PTR(ret);
 667
 668         epayload = kzalloc(sizeof(*epayload) + payload_datalen +
 669                            datablob_len + HASH_SIZE + 1, GFP_KERNEL);
 670         if (!epayload)
 671                 return ERR_PTR(-ENOMEM);
 672
 673         epayload->payload_datalen = payload_datalen;
 674         epayload->decrypted_datalen = decrypted_datalen;
 675         epayload->datablob_len = datablob_len;
 676         return epayload;
 677 }
 678
 679 static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
 680                                  const char *format, const char *hex_encoded_iv)
 681 {
 682         struct key *mkey;
 683         u8 derived_key[HASH_SIZE];
 684         const u8 *master_key;
 685         u8 *hmac;
 686         const char *hex_encoded_data;
 687         unsigned int encrypted_datalen;
 688         size_t master_keylen;
 689         size_t asciilen;
 690         int ret;
 691
 692         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 693         asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
 694         if (strlen(hex_encoded_iv) != asciilen)
 695                 return -EINVAL;
 696
 697         hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
 698         ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
 699         if (ret < 0)
 700                 return -EINVAL;
 701         ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
 702                       encrypted_datalen);
 703         if (ret < 0)
 704                 return -EINVAL;
 705
 706         hmac = epayload->format + epayload->datablob_len;
 707         ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
 708                       HASH_SIZE);
 709         if (ret < 0)
 710                 return -EINVAL;
 711
 712         mkey = request_master_key(epayload, &master_key, &master_keylen);
 713         if (IS_ERR(mkey))
 714                 return PTR_ERR(mkey);
 715
 716         ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
 717         if (ret < 0) {
 718                 pr_err("encrypted_key: bad hmac (%d)\n", ret);
 719                 goto out;
 720         }
 721
 722         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 723         if (ret < 0)
 724                 goto out;
 725
 726         ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
 727         if (ret < 0)
 728                 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
 729 out:
 730         up_read(&mkey->sem);
 731         key_put(mkey);
 732         return ret;
 733 }
 734
 735 static void __ekey_init(struct encrypted_key_payload *epayload,
 736                         const char *format, const char *master_desc,
 737                         const char *datalen)
 738 {
 739         unsigned int format_len;
 740
 741         format_len = (!format) ? strlen(key_format_default) : strlen(format);
 742         epayload->format = epayload->payload_data + epayload->payload_datalen;
 743         epayload->master_desc = epayload->format + format_len + 1;
 744         epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
 745         epayload->iv = epayload->datalen + strlen(datalen) + 1;
 746         epayload->encrypted_data = epayload->iv + ivsize + 1;
 747         epayload->decrypted_data = epayload->payload_data;
 748
 749         if (!format)
 750                 memcpy(epayload->format, key_format_default, format_len);
 751         else {
 752                 if (!strcmp(format, key_format_ecryptfs))
 753                         epayload->decrypted_data =
 754                                 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
 755
 756                 memcpy(epayload->format, format, format_len);
 757         }
 758
 759         memcpy(epayload->master_desc, master_desc, strlen(master_desc));
 760         memcpy(epayload->datalen, datalen, strlen(datalen));
 761 }
 762
 763 /*
 764  * encrypted_init - initialize an encrypted key
 765  *
 766  * For a new key, use a random number for both the iv and data
 767  * itself.  For an old key, decrypt the hex encoded data.
 768  */
 769 static int encrypted_init(struct encrypted_key_payload *epayload,
 770                           const char *key_desc, const char *format,
 771                           const char *master_desc, const char *datalen,
 772                           const char *hex_encoded_iv)
 773 {
 774         int ret = 0;
 775
 776         if (format && !strcmp(format, key_format_ecryptfs)) {
 777                 ret = valid_ecryptfs_desc(key_desc);
 778                 if (ret < 0)
 779                         return ret;
 780
 781                 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
 782                                        key_desc);
 783         }
 784
 785         __ekey_init(epayload, format, master_desc, datalen);
 786         if (!hex_encoded_iv) {
 787                 get_random_bytes(epayload->iv, ivsize);
 788
 789                 get_random_bytes(epayload->decrypted_data,
 790                                  epayload->decrypted_datalen);
 791         } else
 792                 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
 793         return ret;
 794 }
 795
 796 /*
 797  * encrypted_instantiate - instantiate an encrypted key
 798  *
 799  * Decrypt an existing encrypted datablob or create a new encrypted key
 800  * based on a kernel random number.
 801  *
 802  * On success, return 0. Otherwise return errno.
 803  */
 804 static int encrypted_instantiate(struct key *key,
 805                                  struct key_preparsed_payload *prep)
 806 {
 807         struct encrypted_key_payload *epayload = NULL;
 808         char *datablob = NULL;
 809         const char *format = NULL;
 810         char *master_desc = NULL;
 811         char *decrypted_datalen = NULL;
 812         char *hex_encoded_iv = NULL;
 813         size_t datalen = prep->datalen;
 814         int ret;
 815
 816         if (datalen <= 0 || datalen > 32767 || !prep->data)
 817                 return -EINVAL;
 818
 819         datablob = kmalloc(datalen + 1, GFP_KERNEL);
 820         if (!datablob)
 821                 return -ENOMEM;
 822         datablob[datalen] = 0;
 823         memcpy(datablob, prep->data, datalen);
 824         ret = datablob_parse(datablob, &format, &master_desc,
 825                              &decrypted_datalen, &hex_encoded_iv);
 826         if (ret < 0)
 827                 goto out;
 828
 829         epayload = encrypted_key_alloc(key, format, master_desc,
 830                                        decrypted_datalen);
 831         if (IS_ERR(epayload)) {
 832                 ret = PTR_ERR(epayload);
 833                 goto out;
 834         }
 835         ret = encrypted_init(epayload, key->description, format, master_desc,
 836                              decrypted_datalen, hex_encoded_iv);
 837         if (ret < 0) {
 838                 kfree(epayload);
 839                 goto out;
 840         }
 841
 842         rcu_assign_keypointer(key, epayload);
 843 out:
 844         kfree(datablob);
 845         return ret;
 846 }
 847
 848 static void encrypted_rcu_free(struct rcu_head *rcu)
 849 {
 850         struct encrypted_key_payload *epayload;
 851
 852         epayload = container_of(rcu, struct encrypted_key_payload, rcu);
 853         memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
 854         kfree(epayload);
 855 }
 856
 857 /*
 858  * encrypted_update - update the master key description
 859  *
 860  * Change the master key description for an existing encrypted key.
 861  * The next read will return an encrypted datablob using the new
 862  * master key description.
 863  *
 864  * On success, return 0. Otherwise return errno.
 865  */
 866 static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
 867 {
 868         struct encrypted_key_payload *epayload = key->payload.data[0];
 869         struct encrypted_key_payload *new_epayload;
 870         char *buf;
 871         char *new_master_desc = NULL;
 872         const char *format = NULL;
 873         size_t datalen = prep->datalen;
 874         int ret = 0;
 875
 876         if (key_is_negative(key))
 877                 return -ENOKEY;
 878         if (datalen <= 0 || datalen > 32767 || !prep->data)
 879                 return -EINVAL;
 880
 881         buf = kmalloc(datalen + 1, GFP_KERNEL);
 882         if (!buf)
 883                 return -ENOMEM;
 884
 885         buf[datalen] = 0;
 886         memcpy(buf, prep->data, datalen);
 887         ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
 888         if (ret < 0)
 889                 goto out;
 890
 891         ret = valid_master_desc(new_master_desc, epayload->master_desc);
 892         if (ret < 0)
 893                 goto out;
 894
 895         new_epayload = encrypted_key_alloc(key, epayload->format,
 896                                            new_master_desc, epayload->datalen);
 897         if (IS_ERR(new_epayload)) {
 898                 ret = PTR_ERR(new_epayload);
 899                 goto out;
 900         }
 901
 902         __ekey_init(new_epayload, epayload->format, new_master_desc,
 903                     epayload->datalen);
 904
 905         memcpy(new_epayload->iv, epayload->iv, ivsize);
 906         memcpy(new_epayload->payload_data, epayload->payload_data,
 907                epayload->payload_datalen);
 908
 909         rcu_assign_keypointer(key, new_epayload);
 910         call_rcu(&epayload->rcu, encrypted_rcu_free);
 911 out:
 912         kfree(buf);
 913         return ret;
 914 }
 915
 916 /*
 917  * encrypted_read - format and copy the encrypted data to userspace
 918  *
 919  * The resulting datablob format is:
 920  * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
 921  *
 922  * On success, return to userspace the encrypted key datablob size.
 923  */
 924 static long encrypted_read(const struct key *key, char __user *buffer,
 925                            size_t buflen)
 926 {
 927         struct encrypted_key_payload *epayload;
 928         struct key *mkey;
 929         const u8 *master_key;
 930         size_t master_keylen;
 931         char derived_key[HASH_SIZE];
 932         char *ascii_buf;
 933         size_t asciiblob_len;
 934         int ret;
 935
 936         epayload = rcu_dereference_key(key);
 937
 938         /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
 939         asciiblob_len = epayload->datablob_len + ivsize + 1
 940             + roundup(epayload->decrypted_datalen, blksize)
 941             + (HASH_SIZE * 2);
 942
 943         if (!buffer || buflen < asciiblob_len)
 944                 return asciiblob_len;
 945
 946         mkey = request_master_key(epayload, &master_key, &master_keylen);
 947         if (IS_ERR(mkey))
 948                 return PTR_ERR(mkey);
 949
 950         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 951         if (ret < 0)
 952                 goto out;
 953
 954         ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
 955         if (ret < 0)
 956                 goto out;
 957
 958         ret = datablob_hmac_append(epayload, master_key, master_keylen);
 959         if (ret < 0)
 960                 goto out;
 961
 962         ascii_buf = datablob_format(epayload, asciiblob_len);
 963         if (!ascii_buf) {
 964                 ret = -ENOMEM;
 965                 goto out;
 966         }
 967
 968         up_read(&mkey->sem);
 969         key_put(mkey);
 970
 971         if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0)
 972                 ret = -EFAULT;
 973         kfree(ascii_buf);
 974
 975         return asciiblob_len;
 976 out:
 977         up_read(&mkey->sem);
 978         key_put(mkey);
 979         return ret;
 980 }
 981
 982 /*
 983  * encrypted_destroy - before freeing the key, clear the decrypted data
 984  *
 985  * Before freeing the key, clear the memory containing the decrypted
 986  * key data.
 987  */
 988 static void encrypted_destroy(struct key *key)
 989 {
 990         struct encrypted_key_payload *epayload = key->payload.data[0];
 991
 992         if (!epayload)
 993                 return;
 994
 995         memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
 996         kfree(key->payload.data[0]);
 997 }
 998
 999 struct key_type key_type_encrypted = {
1000         .name = "encrypted",
1001         .instantiate = encrypted_instantiate,
1002         .update = encrypted_update,
1003         .destroy = encrypted_destroy,
1004         .describe = user_describe,
1005         .read = encrypted_read,
1006 };
1007 EXPORT_SYMBOL_GPL(key_type_encrypted);
1008
1009 static void encrypted_shash_release(void)
1010 {
1011         if (hashalg)
1012                 crypto_free_shash(hashalg);
1013         if (hmacalg)
1014                 crypto_free_shash(hmacalg);
1015 }
1016
1017 static int __init encrypted_shash_alloc(void)
1018 {
1019         int ret;
1020
1021         hmacalg = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC);
1022         if (IS_ERR(hmacalg)) {
1023                 pr_info("encrypted_key: could not allocate crypto %s\n",
1024                         hmac_alg);
1025                 return PTR_ERR(hmacalg);
1026         }
1027
1028         hashalg = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC);
1029         if (IS_ERR(hashalg)) {
1030                 pr_info("encrypted_key: could not allocate crypto %s\n",
1031                         hash_alg);
1032                 ret = PTR_ERR(hashalg);
1033                 goto hashalg_fail;
1034         }
1035
1036         return 0;
1037
1038 hashalg_fail:
1039         crypto_free_shash(hmacalg);
1040         return ret;
1041 }
1042
1043 static int __init init_encrypted(void)
1044 {
1045         int ret;
1046
1047         ret = encrypted_shash_alloc();
1048         if (ret < 0)
1049                 return ret;
1050         ret = aes_get_sizes();
1051         if (ret < 0)
1052                 goto out;
1053         ret = register_key_type(&key_type_encrypted);
1054         if (ret < 0)
1055                 goto out;
1056         return 0;
1057 out:
1058         encrypted_shash_release();
1059         return ret;
1060
1061 }
1062
1063 static void __exit cleanup_encrypted(void)
1064 {
1065         encrypted_shash_release();
1066         unregister_key_type(&key_type_encrypted);
1067 }
1068
1069 late_initcall(init_encrypted);
1070 module_exit(cleanup_encrypted);
1071
1072 MODULE_LICENSE("GPL");