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