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