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/crypto.h>
  32 #include <linux/ctype.h>
  33 #include <crypto/hash.h>
  34 #include <crypto/sha.h>
  35 #include <crypto/aes.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_blkcipher *tfm;
  89
  90         tfm = crypto_alloc_blkcipher(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_blkcipher_ivsize(tfm);
  97         blksize = crypto_blkcipher_blocksize(tfm);
  98         crypto_free_blkcipher(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, u8 **master_key,
 307                                     size_t *master_keylen)
 308 {
 309         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 = ukey->payload.data;
 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 int init_blkcipher_desc(struct blkcipher_desc *desc, const u8 *key,
 405                                unsigned int key_len, const u8 *iv,
 406                                unsigned int ivsize)
 407 {
 408         int ret;
 409
 410         desc->tfm = crypto_alloc_blkcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
 411         if (IS_ERR(desc->tfm)) {
 412                 pr_err("encrypted_key: failed to load %s transform (%ld)\n",
 413                        blkcipher_alg, PTR_ERR(desc->tfm));
 414                 return PTR_ERR(desc->tfm);
 415         }
 416         desc->flags = 0;
 417
 418         ret = crypto_blkcipher_setkey(desc->tfm, key, key_len);
 419         if (ret < 0) {
 420                 pr_err("encrypted_key: failed to setkey (%d)\n", ret);
 421                 crypto_free_blkcipher(desc->tfm);
 422                 return ret;
 423         }
 424         crypto_blkcipher_set_iv(desc->tfm, iv, ivsize);
 425         return 0;
 426 }
 427
 428 static struct key *request_master_key(struct encrypted_key_payload *epayload,
 429                                       u8 **master_key, size_t *master_keylen)
 430 {
 431         struct key *mkey = NULL;
 432
 433         if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
 434                      KEY_TRUSTED_PREFIX_LEN)) {
 435                 mkey = request_trusted_key(epayload->master_desc +
 436                                            KEY_TRUSTED_PREFIX_LEN,
 437                                            master_key, master_keylen);
 438         } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
 439                             KEY_USER_PREFIX_LEN)) {
 440                 mkey = request_user_key(epayload->master_desc +
 441                                         KEY_USER_PREFIX_LEN,
 442                                         master_key, master_keylen);
 443         } else
 444                 goto out;
 445
 446         if (IS_ERR(mkey)) {
 447                 int ret = PTR_ERR(mkey);
 448
 449                 if (ret == -ENOTSUPP)
 450                         pr_info("encrypted_key: key %s not supported",
 451                                 epayload->master_desc);
 452                 else
 453                         pr_info("encrypted_key: key %s not found",
 454                                 epayload->master_desc);
 455                 goto out;
 456         }
 457
 458         dump_master_key(*master_key, *master_keylen);
 459 out:
 460         return mkey;
 461 }
 462
 463 /* Before returning data to userspace, encrypt decrypted data. */
 464 static int derived_key_encrypt(struct encrypted_key_payload *epayload,
 465                                const u8 *derived_key,
 466                                unsigned int derived_keylen)
 467 {
 468         struct scatterlist sg_in[2];
 469         struct scatterlist sg_out[1];
 470         struct blkcipher_desc desc;
 471         unsigned int encrypted_datalen;
 472         unsigned int padlen;
 473         char pad[16];
 474         int ret;
 475
 476         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 477         padlen = encrypted_datalen - epayload->decrypted_datalen;
 478
 479         ret = init_blkcipher_desc(&desc, derived_key, derived_keylen,
 480                                   epayload->iv, ivsize);
 481         if (ret < 0)
 482                 goto out;
 483         dump_decrypted_data(epayload);
 484
 485         memset(pad, 0, sizeof pad);
 486         sg_init_table(sg_in, 2);
 487         sg_set_buf(&sg_in[0], epayload->decrypted_data,
 488                    epayload->decrypted_datalen);
 489         sg_set_buf(&sg_in[1], pad, padlen);
 490
 491         sg_init_table(sg_out, 1);
 492         sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
 493
 494         ret = crypto_blkcipher_encrypt(&desc, sg_out, sg_in, encrypted_datalen);
 495         crypto_free_blkcipher(desc.tfm);
 496         if (ret < 0)
 497                 pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
 498         else
 499                 dump_encrypted_data(epayload, encrypted_datalen);
 500 out:
 501         return ret;
 502 }
 503
 504 static int datablob_hmac_append(struct encrypted_key_payload *epayload,
 505                                 const u8 *master_key, size_t master_keylen)
 506 {
 507         u8 derived_key[HASH_SIZE];
 508         u8 *digest;
 509         int ret;
 510
 511         ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 512         if (ret < 0)
 513                 goto out;
 514
 515         digest = epayload->format + epayload->datablob_len;
 516         ret = calc_hmac(digest, derived_key, sizeof derived_key,
 517                         epayload->format, epayload->datablob_len);
 518         if (!ret)
 519                 dump_hmac(NULL, digest, HASH_SIZE);
 520 out:
 521         return ret;
 522 }
 523
 524 /* verify HMAC before decrypting encrypted key */
 525 static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
 526                                 const u8 *format, const u8 *master_key,
 527                                 size_t master_keylen)
 528 {
 529         u8 derived_key[HASH_SIZE];
 530         u8 digest[HASH_SIZE];
 531         int ret;
 532         char *p;
 533         unsigned short len;
 534
 535         ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 536         if (ret < 0)
 537                 goto out;
 538
 539         len = epayload->datablob_len;
 540         if (!format) {
 541                 p = epayload->master_desc;
 542                 len -= strlen(epayload->format) + 1;
 543         } else
 544                 p = epayload->format;
 545
 546         ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
 547         if (ret < 0)
 548                 goto out;
 549         ret = memcmp(digest, epayload->format + epayload->datablob_len,
 550                      sizeof digest);
 551         if (ret) {
 552                 ret = -EINVAL;
 553                 dump_hmac("datablob",
 554                           epayload->format + epayload->datablob_len,
 555                           HASH_SIZE);
 556                 dump_hmac("calc", digest, HASH_SIZE);
 557         }
 558 out:
 559         return ret;
 560 }
 561
 562 static int derived_key_decrypt(struct encrypted_key_payload *epayload,
 563                                const u8 *derived_key,
 564                                unsigned int derived_keylen)
 565 {
 566         struct scatterlist sg_in[1];
 567         struct scatterlist sg_out[2];
 568         struct blkcipher_desc desc;
 569         unsigned int encrypted_datalen;
 570         char pad[16];
 571         int ret;
 572
 573         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 574         ret = init_blkcipher_desc(&desc, derived_key, derived_keylen,
 575                                   epayload->iv, ivsize);
 576         if (ret < 0)
 577                 goto out;
 578         dump_encrypted_data(epayload, encrypted_datalen);
 579
 580         memset(pad, 0, sizeof pad);
 581         sg_init_table(sg_in, 1);
 582         sg_init_table(sg_out, 2);
 583         sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
 584         sg_set_buf(&sg_out[0], epayload->decrypted_data,
 585                    epayload->decrypted_datalen);
 586         sg_set_buf(&sg_out[1], pad, sizeof pad);
 587
 588         ret = crypto_blkcipher_decrypt(&desc, sg_out, sg_in, encrypted_datalen);
 589         crypto_free_blkcipher(desc.tfm);
 590         if (ret < 0)
 591                 goto out;
 592         dump_decrypted_data(epayload);
 593 out:
 594         return ret;
 595 }
 596
 597 /* Allocate memory for decrypted key and datablob. */
 598 static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
 599                                                          const char *format,
 600                                                          const char *master_desc,
 601                                                          const char *datalen)
 602 {
 603         struct encrypted_key_payload *epayload = NULL;
 604         unsigned short datablob_len;
 605         unsigned short decrypted_datalen;
 606         unsigned short payload_datalen;
 607         unsigned int encrypted_datalen;
 608         unsigned int format_len;
 609         long dlen;
 610         int ret;
 611
 612         ret = strict_strtol(datalen, 10, &dlen);
 613         if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
 614                 return ERR_PTR(-EINVAL);
 615
 616         format_len = (!format) ? strlen(key_format_default) : strlen(format);
 617         decrypted_datalen = dlen;
 618         payload_datalen = decrypted_datalen;
 619         if (format && !strcmp(format, key_format_ecryptfs)) {
 620                 if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
 621                         pr_err("encrypted_key: keylen for the ecryptfs format "
 622                                "must be equal to %d bytes\n",
 623                                ECRYPTFS_MAX_KEY_BYTES);
 624                         return ERR_PTR(-EINVAL);
 625                 }
 626                 decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
 627                 payload_datalen = sizeof(struct ecryptfs_auth_tok);
 628         }
 629
 630         encrypted_datalen = roundup(decrypted_datalen, blksize);
 631
 632         datablob_len = format_len + 1 + strlen(master_desc) + 1
 633             + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
 634
 635         ret = key_payload_reserve(key, payload_datalen + datablob_len
 636                                   + HASH_SIZE + 1);
 637         if (ret < 0)
 638                 return ERR_PTR(ret);
 639
 640         epayload = kzalloc(sizeof(*epayload) + payload_datalen +
 641                            datablob_len + HASH_SIZE + 1, GFP_KERNEL);
 642         if (!epayload)
 643                 return ERR_PTR(-ENOMEM);
 644
 645         epayload->payload_datalen = payload_datalen;
 646         epayload->decrypted_datalen = decrypted_datalen;
 647         epayload->datablob_len = datablob_len;
 648         return epayload;
 649 }
 650
 651 static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
 652                                  const char *format, const char *hex_encoded_iv)
 653 {
 654         struct key *mkey;
 655         u8 derived_key[HASH_SIZE];
 656         u8 *master_key;
 657         u8 *hmac;
 658         const char *hex_encoded_data;
 659         unsigned int encrypted_datalen;
 660         size_t master_keylen;
 661         size_t asciilen;
 662         int ret;
 663
 664         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 665         asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
 666         if (strlen(hex_encoded_iv) != asciilen)
 667                 return -EINVAL;
 668
 669         hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
 670         ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize);
 671         if (ret < 0)
 672                 return -EINVAL;
 673         ret = hex2bin(epayload->encrypted_data, hex_encoded_data,
 674                       encrypted_datalen);
 675         if (ret < 0)
 676                 return -EINVAL;
 677
 678         hmac = epayload->format + epayload->datablob_len;
 679         ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2),
 680                       HASH_SIZE);
 681         if (ret < 0)
 682                 return -EINVAL;
 683
 684         mkey = request_master_key(epayload, &master_key, &master_keylen);
 685         if (IS_ERR(mkey))
 686                 return PTR_ERR(mkey);
 687
 688         ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
 689         if (ret < 0) {
 690                 pr_err("encrypted_key: bad hmac (%d)\n", ret);
 691                 goto out;
 692         }
 693
 694         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 695         if (ret < 0)
 696                 goto out;
 697
 698         ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
 699         if (ret < 0)
 700                 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
 701 out:
 702         up_read(&mkey->sem);
 703         key_put(mkey);
 704         return ret;
 705 }
 706
 707 static void __ekey_init(struct encrypted_key_payload *epayload,
 708                         const char *format, const char *master_desc,
 709                         const char *datalen)
 710 {
 711         unsigned int format_len;
 712
 713         format_len = (!format) ? strlen(key_format_default) : strlen(format);
 714         epayload->format = epayload->payload_data + epayload->payload_datalen;
 715         epayload->master_desc = epayload->format + format_len + 1;
 716         epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
 717         epayload->iv = epayload->datalen + strlen(datalen) + 1;
 718         epayload->encrypted_data = epayload->iv + ivsize + 1;
 719         epayload->decrypted_data = epayload->payload_data;
 720
 721         if (!format)
 722                 memcpy(epayload->format, key_format_default, format_len);
 723         else {
 724                 if (!strcmp(format, key_format_ecryptfs))
 725                         epayload->decrypted_data =
 726                                 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
 727
 728                 memcpy(epayload->format, format, format_len);
 729         }
 730
 731         memcpy(epayload->master_desc, master_desc, strlen(master_desc));
 732         memcpy(epayload->datalen, datalen, strlen(datalen));
 733 }
 734
 735 /*
 736  * encrypted_init - initialize an encrypted key
 737  *
 738  * For a new key, use a random number for both the iv and data
 739  * itself.  For an old key, decrypt the hex encoded data.
 740  */
 741 static int encrypted_init(struct encrypted_key_payload *epayload,
 742                           const char *key_desc, const char *format,
 743                           const char *master_desc, const char *datalen,
 744                           const char *hex_encoded_iv)
 745 {
 746         int ret = 0;
 747
 748         if (format && !strcmp(format, key_format_ecryptfs)) {
 749                 ret = valid_ecryptfs_desc(key_desc);
 750                 if (ret < 0)
 751                         return ret;
 752
 753                 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
 754                                        key_desc);
 755         }
 756
 757         __ekey_init(epayload, format, master_desc, datalen);
 758         if (!hex_encoded_iv) {
 759                 get_random_bytes(epayload->iv, ivsize);
 760
 761                 get_random_bytes(epayload->decrypted_data,
 762                                  epayload->decrypted_datalen);
 763         } else
 764                 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
 765         return ret;
 766 }
 767
 768 /*
 769  * encrypted_instantiate - instantiate an encrypted key
 770  *
 771  * Decrypt an existing encrypted datablob or create a new encrypted key
 772  * based on a kernel random number.
 773  *
 774  * On success, return 0. Otherwise return errno.
 775  */
 776 static int encrypted_instantiate(struct key *key, const void *data,
 777                                  size_t datalen)
 778 {
 779         struct encrypted_key_payload *epayload = NULL;
 780         char *datablob = NULL;
 781         const char *format = NULL;
 782         char *master_desc = NULL;
 783         char *decrypted_datalen = NULL;
 784         char *hex_encoded_iv = NULL;
 785         int ret;
 786
 787         if (datalen <= 0 || datalen > 32767 || !data)
 788                 return -EINVAL;
 789
 790         datablob = kmalloc(datalen + 1, GFP_KERNEL);
 791         if (!datablob)
 792                 return -ENOMEM;
 793         datablob[datalen] = 0;
 794         memcpy(datablob, data, datalen);
 795         ret = datablob_parse(datablob, &format, &master_desc,
 796                              &decrypted_datalen, &hex_encoded_iv);
 797         if (ret < 0)
 798                 goto out;
 799
 800         epayload = encrypted_key_alloc(key, format, master_desc,
 801                                        decrypted_datalen);
 802         if (IS_ERR(epayload)) {
 803                 ret = PTR_ERR(epayload);
 804                 goto out;
 805         }
 806         ret = encrypted_init(epayload, key->description, format, master_desc,
 807                              decrypted_datalen, hex_encoded_iv);
 808         if (ret < 0) {
 809                 kfree(epayload);
 810                 goto out;
 811         }
 812
 813         rcu_assign_keypointer(key, epayload);
 814 out:
 815         kfree(datablob);
 816         return ret;
 817 }
 818
 819 static void encrypted_rcu_free(struct rcu_head *rcu)
 820 {
 821         struct encrypted_key_payload *epayload;
 822
 823         epayload = container_of(rcu, struct encrypted_key_payload, rcu);
 824         memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
 825         kfree(epayload);
 826 }
 827
 828 /*
 829  * encrypted_update - update the master key description
 830  *
 831  * Change the master key description for an existing encrypted key.
 832  * The next read will return an encrypted datablob using the new
 833  * master key description.
 834  *
 835  * On success, return 0. Otherwise return errno.
 836  */
 837 static int encrypted_update(struct key *key, const void *data, size_t datalen)
 838 {
 839         struct encrypted_key_payload *epayload = key->payload.data;
 840         struct encrypted_key_payload *new_epayload;
 841         char *buf;
 842         char *new_master_desc = NULL;
 843         const char *format = NULL;
 844         int ret = 0;
 845
 846         if (datalen <= 0 || datalen > 32767 || !data)
 847                 return -EINVAL;
 848
 849         buf = kmalloc(datalen + 1, GFP_KERNEL);
 850         if (!buf)
 851                 return -ENOMEM;
 852
 853         buf[datalen] = 0;
 854         memcpy(buf, data, datalen);
 855         ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
 856         if (ret < 0)
 857                 goto out;
 858
 859         ret = valid_master_desc(new_master_desc, epayload->master_desc);
 860         if (ret < 0)
 861                 goto out;
 862
 863         new_epayload = encrypted_key_alloc(key, epayload->format,
 864                                            new_master_desc, epayload->datalen);
 865         if (IS_ERR(new_epayload)) {
 866                 ret = PTR_ERR(new_epayload);
 867                 goto out;
 868         }
 869
 870         __ekey_init(new_epayload, epayload->format, new_master_desc,
 871                     epayload->datalen);
 872
 873         memcpy(new_epayload->iv, epayload->iv, ivsize);
 874         memcpy(new_epayload->payload_data, epayload->payload_data,
 875                epayload->payload_datalen);
 876
 877         rcu_assign_keypointer(key, new_epayload);
 878         call_rcu(&epayload->rcu, encrypted_rcu_free);
 879 out:
 880         kfree(buf);
 881         return ret;
 882 }
 883
 884 /*
 885  * encrypted_read - format and copy the encrypted data to userspace
 886  *
 887  * The resulting datablob format is:
 888  * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
 889  *
 890  * On success, return to userspace the encrypted key datablob size.
 891  */
 892 static long encrypted_read(const struct key *key, char __user *buffer,
 893                            size_t buflen)
 894 {
 895         struct encrypted_key_payload *epayload;
 896         struct key *mkey;
 897         u8 *master_key;
 898         size_t master_keylen;
 899         char derived_key[HASH_SIZE];
 900         char *ascii_buf;
 901         size_t asciiblob_len;
 902         int ret;
 903
 904         epayload = rcu_dereference_key(key);
 905
 906         /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
 907         asciiblob_len = epayload->datablob_len + ivsize + 1
 908             + roundup(epayload->decrypted_datalen, blksize)
 909             + (HASH_SIZE * 2);
 910
 911         if (!buffer || buflen < asciiblob_len)
 912                 return asciiblob_len;
 913
 914         mkey = request_master_key(epayload, &master_key, &master_keylen);
 915         if (IS_ERR(mkey))
 916                 return PTR_ERR(mkey);
 917
 918         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 919         if (ret < 0)
 920                 goto out;
 921
 922         ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
 923         if (ret < 0)
 924                 goto out;
 925
 926         ret = datablob_hmac_append(epayload, master_key, master_keylen);
 927         if (ret < 0)
 928                 goto out;
 929
 930         ascii_buf = datablob_format(epayload, asciiblob_len);
 931         if (!ascii_buf) {
 932                 ret = -ENOMEM;
 933                 goto out;
 934         }
 935
 936         up_read(&mkey->sem);
 937         key_put(mkey);
 938
 939         if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0)
 940                 ret = -EFAULT;
 941         kfree(ascii_buf);
 942
 943         return asciiblob_len;
 944 out:
 945         up_read(&mkey->sem);
 946         key_put(mkey);
 947         return ret;
 948 }
 949
 950 /*
 951  * encrypted_destroy - before freeing the key, clear the decrypted data
 952  *
 953  * Before freeing the key, clear the memory containing the decrypted
 954  * key data.
 955  */
 956 static void encrypted_destroy(struct key *key)
 957 {
 958         struct encrypted_key_payload *epayload = key->payload.data;
 959
 960         if (!epayload)
 961                 return;
 962
 963         memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
 964         kfree(key->payload.data);
 965 }
 966
 967 struct key_type key_type_encrypted = {
 968         .name = "encrypted",
 969         .instantiate = encrypted_instantiate,
 970         .update = encrypted_update,
 971         .match = user_match,
 972         .destroy = encrypted_destroy,
 973         .describe = user_describe,
 974         .read = encrypted_read,
 975 };
 976 EXPORT_SYMBOL_GPL(key_type_encrypted);
 977
 978 static void encrypted_shash_release(void)
 979 {
 980         if (hashalg)
 981                 crypto_free_shash(hashalg);
 982         if (hmacalg)
 983                 crypto_free_shash(hmacalg);
 984 }
 985
 986 static int __init encrypted_shash_alloc(void)
 987 {
 988         int ret;
 989
 990         hmacalg = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC);
 991         if (IS_ERR(hmacalg)) {
 992                 pr_info("encrypted_key: could not allocate crypto %s\n",
 993                         hmac_alg);
 994                 return PTR_ERR(hmacalg);
 995         }
 996
 997         hashalg = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC);
 998         if (IS_ERR(hashalg)) {
 999                 pr_info("encrypted_key: could not allocate crypto %s\n",
1000                         hash_alg);
1001                 ret = PTR_ERR(hashalg);
1002                 goto hashalg_fail;
1003         }
1004
1005         return 0;
1006
1007 hashalg_fail:
1008         crypto_free_shash(hmacalg);
1009         return ret;
1010 }
1011
1012 static int __init init_encrypted(void)
1013 {
1014         int ret;
1015
1016         ret = encrypted_shash_alloc();
1017         if (ret < 0)
1018                 return ret;
1019         ret = register_key_type(&key_type_encrypted);
1020         if (ret < 0)
1021                 goto out;
1022         return aes_get_sizes();
1023 out:
1024         encrypted_shash_release();
1025         return ret;
1026
1027 }
1028
1029 static void __exit cleanup_encrypted(void)
1030 {
1031         encrypted_shash_release();
1032         unregister_key_type(&key_type_encrypted);
1033 }
1034
1035 late_initcall(init_encrypted);
1036 module_exit(cleanup_encrypted);
1037
1038 MODULE_LICENSE("GPL");