security/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 = pack_hex_byte(bufp, iv[i]);
 297 out:
 298         return ascii_buf;
 299 }
 300
 301 /*
 302  * request_trusted_key - request the trusted key
 303  *
 304  * Trusted keys are sealed to PCRs and other metadata. Although userspace
 305  * manages both trusted/encrypted key-types, like the encrypted key type
 306  * data, trusted key type data is not visible decrypted from userspace.
 307  */
 308 static struct key *request_trusted_key(const char *trusted_desc,
 309                                        u8 **master_key, size_t *master_keylen)
 310 {
 311         struct trusted_key_payload *tpayload;
 312         struct key *tkey;
 313
 314         tkey = request_key(&key_type_trusted, trusted_desc, NULL);
 315         if (IS_ERR(tkey))
 316                 goto error;
 317
 318         down_read(&tkey->sem);
 319         tpayload = rcu_dereference(tkey->payload.data);
 320         *master_key = tpayload->key;
 321         *master_keylen = tpayload->key_len;
 322 error:
 323         return tkey;
 324 }
 325
 326 /*
 327  * request_user_key - request the user key
 328  *
 329  * Use a user provided key to encrypt/decrypt an encrypted-key.
 330  */
 331 static struct key *request_user_key(const char *master_desc, u8 **master_key,
 332                                     size_t *master_keylen)
 333 {
 334         struct user_key_payload *upayload;
 335         struct key *ukey;
 336
 337         ukey = request_key(&key_type_user, master_desc, NULL);
 338         if (IS_ERR(ukey))
 339                 goto error;
 340
 341         down_read(&ukey->sem);
 342         upayload = rcu_dereference(ukey->payload.data);
 343         *master_key = upayload->data;
 344         *master_keylen = upayload->datalen;
 345 error:
 346         return ukey;
 347 }
 348
 349 static struct sdesc *alloc_sdesc(struct crypto_shash *alg)
 350 {
 351         struct sdesc *sdesc;
 352         int size;
 353
 354         size = sizeof(struct shash_desc) + crypto_shash_descsize(alg);
 355         sdesc = kmalloc(size, GFP_KERNEL);
 356         if (!sdesc)
 357                 return ERR_PTR(-ENOMEM);
 358         sdesc->shash.tfm = alg;
 359         sdesc->shash.flags = 0x0;
 360         return sdesc;
 361 }
 362
 363 static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
 364                      const u8 *buf, unsigned int buflen)
 365 {
 366         struct sdesc *sdesc;
 367         int ret;
 368
 369         sdesc = alloc_sdesc(hmacalg);
 370         if (IS_ERR(sdesc)) {
 371                 pr_info("encrypted_key: can't alloc %s\n", hmac_alg);
 372                 return PTR_ERR(sdesc);
 373         }
 374
 375         ret = crypto_shash_setkey(hmacalg, key, keylen);
 376         if (!ret)
 377                 ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest);
 378         kfree(sdesc);
 379         return ret;
 380 }
 381
 382 static int calc_hash(u8 *digest, const u8 *buf, unsigned int buflen)
 383 {
 384         struct sdesc *sdesc;
 385         int ret;
 386
 387         sdesc = alloc_sdesc(hashalg);
 388         if (IS_ERR(sdesc)) {
 389                 pr_info("encrypted_key: can't alloc %s\n", hash_alg);
 390                 return PTR_ERR(sdesc);
 391         }
 392
 393         ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest);
 394         kfree(sdesc);
 395         return ret;
 396 }
 397
 398 enum derived_key_type { ENC_KEY, AUTH_KEY };
 399
 400 /* Derive authentication/encryption key from trusted key */
 401 static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
 402                            const u8 *master_key, size_t master_keylen)
 403 {
 404         u8 *derived_buf;
 405         unsigned int derived_buf_len;
 406         int ret;
 407
 408         derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
 409         if (derived_buf_len < HASH_SIZE)
 410                 derived_buf_len = HASH_SIZE;
 411
 412         derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
 413         if (!derived_buf) {
 414                 pr_err("encrypted_key: out of memory\n");
 415                 return -ENOMEM;
 416         }
 417         if (key_type)
 418                 strcpy(derived_buf, "AUTH_KEY");
 419         else
 420                 strcpy(derived_buf, "ENC_KEY");
 421
 422         memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
 423                master_keylen);
 424         ret = calc_hash(derived_key, derived_buf, derived_buf_len);
 425         kfree(derived_buf);
 426         return ret;
 427 }
 428
 429 static int init_blkcipher_desc(struct blkcipher_desc *desc, const u8 *key,
 430                                unsigned int key_len, const u8 *iv,
 431                                unsigned int ivsize)
 432 {
 433         int ret;
 434
 435         desc->tfm = crypto_alloc_blkcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
 436         if (IS_ERR(desc->tfm)) {
 437                 pr_err("encrypted_key: failed to load %s transform (%ld)\n",
 438                        blkcipher_alg, PTR_ERR(desc->tfm));
 439                 return PTR_ERR(desc->tfm);
 440         }
 441         desc->flags = 0;
 442
 443         ret = crypto_blkcipher_setkey(desc->tfm, key, key_len);
 444         if (ret < 0) {
 445                 pr_err("encrypted_key: failed to setkey (%d)\n", ret);
 446                 crypto_free_blkcipher(desc->tfm);
 447                 return ret;
 448         }
 449         crypto_blkcipher_set_iv(desc->tfm, iv, ivsize);
 450         return 0;
 451 }
 452
 453 static struct key *request_master_key(struct encrypted_key_payload *epayload,
 454                                       u8 **master_key, size_t *master_keylen)
 455 {
 456         struct key *mkey = NULL;
 457
 458         if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
 459                      KEY_TRUSTED_PREFIX_LEN)) {
 460                 mkey = request_trusted_key(epayload->master_desc +
 461                                            KEY_TRUSTED_PREFIX_LEN,
 462                                            master_key, master_keylen);
 463         } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
 464                             KEY_USER_PREFIX_LEN)) {
 465                 mkey = request_user_key(epayload->master_desc +
 466                                         KEY_USER_PREFIX_LEN,
 467                                         master_key, master_keylen);
 468         } else
 469                 goto out;
 470
 471         if (IS_ERR(mkey)) {
 472                 pr_info("encrypted_key: key %s not found",
 473                         epayload->master_desc);
 474                 goto out;
 475         }
 476
 477         dump_master_key(*master_key, *master_keylen);
 478 out:
 479         return mkey;
 480 }
 481
 482 /* Before returning data to userspace, encrypt decrypted data. */
 483 static int derived_key_encrypt(struct encrypted_key_payload *epayload,
 484                                const u8 *derived_key,
 485                                unsigned int derived_keylen)
 486 {
 487         struct scatterlist sg_in[2];
 488         struct scatterlist sg_out[1];
 489         struct blkcipher_desc desc;
 490         unsigned int encrypted_datalen;
 491         unsigned int padlen;
 492         char pad[16];
 493         int ret;
 494
 495         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 496         padlen = encrypted_datalen - epayload->decrypted_datalen;
 497
 498         ret = init_blkcipher_desc(&desc, derived_key, derived_keylen,
 499                                   epayload->iv, ivsize);
 500         if (ret < 0)
 501                 goto out;
 502         dump_decrypted_data(epayload);
 503
 504         memset(pad, 0, sizeof pad);
 505         sg_init_table(sg_in, 2);
 506         sg_set_buf(&sg_in[0], epayload->decrypted_data,
 507                    epayload->decrypted_datalen);
 508         sg_set_buf(&sg_in[1], pad, padlen);
 509
 510         sg_init_table(sg_out, 1);
 511         sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
 512
 513         ret = crypto_blkcipher_encrypt(&desc, sg_out, sg_in, encrypted_datalen);
 514         crypto_free_blkcipher(desc.tfm);
 515         if (ret < 0)
 516                 pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
 517         else
 518                 dump_encrypted_data(epayload, encrypted_datalen);
 519 out:
 520         return ret;
 521 }
 522
 523 static int datablob_hmac_append(struct encrypted_key_payload *epayload,
 524                                 const u8 *master_key, size_t master_keylen)
 525 {
 526         u8 derived_key[HASH_SIZE];
 527         u8 *digest;
 528         int ret;
 529
 530         ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 531         if (ret < 0)
 532                 goto out;
 533
 534         digest = epayload->format + epayload->datablob_len;
 535         ret = calc_hmac(digest, derived_key, sizeof derived_key,
 536                         epayload->format, epayload->datablob_len);
 537         if (!ret)
 538                 dump_hmac(NULL, digest, HASH_SIZE);
 539 out:
 540         return ret;
 541 }
 542
 543 /* verify HMAC before decrypting encrypted key */
 544 static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
 545                                 const u8 *format, const u8 *master_key,
 546                                 size_t master_keylen)
 547 {
 548         u8 derived_key[HASH_SIZE];
 549         u8 digest[HASH_SIZE];
 550         int ret;
 551         char *p;
 552         unsigned short len;
 553
 554         ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 555         if (ret < 0)
 556                 goto out;
 557
 558         len = epayload->datablob_len;
 559         if (!format) {
 560                 p = epayload->master_desc;
 561                 len -= strlen(epayload->format) + 1;
 562         } else
 563                 p = epayload->format;
 564
 565         ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len);
 566         if (ret < 0)
 567                 goto out;
 568         ret = memcmp(digest, epayload->format + epayload->datablob_len,
 569                      sizeof digest);
 570         if (ret) {
 571                 ret = -EINVAL;
 572                 dump_hmac("datablob",
 573                           epayload->format + epayload->datablob_len,
 574                           HASH_SIZE);
 575                 dump_hmac("calc", digest, HASH_SIZE);
 576         }
 577 out:
 578         return ret;
 579 }
 580
 581 static int derived_key_decrypt(struct encrypted_key_payload *epayload,
 582                                const u8 *derived_key,
 583                                unsigned int derived_keylen)
 584 {
 585         struct scatterlist sg_in[1];
 586         struct scatterlist sg_out[2];
 587         struct blkcipher_desc desc;
 588         unsigned int encrypted_datalen;
 589         char pad[16];
 590         int ret;
 591
 592         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 593         ret = init_blkcipher_desc(&desc, derived_key, derived_keylen,
 594                                   epayload->iv, ivsize);
 595         if (ret < 0)
 596                 goto out;
 597         dump_encrypted_data(epayload, encrypted_datalen);
 598
 599         memset(pad, 0, sizeof pad);
 600         sg_init_table(sg_in, 1);
 601         sg_init_table(sg_out, 2);
 602         sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
 603         sg_set_buf(&sg_out[0], epayload->decrypted_data,
 604                    epayload->decrypted_datalen);
 605         sg_set_buf(&sg_out[1], pad, sizeof pad);
 606
 607         ret = crypto_blkcipher_decrypt(&desc, sg_out, sg_in, encrypted_datalen);
 608         crypto_free_blkcipher(desc.tfm);
 609         if (ret < 0)
 610                 goto out;
 611         dump_decrypted_data(epayload);
 612 out:
 613         return ret;
 614 }
 615
 616 /* Allocate memory for decrypted key and datablob. */
 617 static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
 618                                                          const char *format,
 619                                                          const char *master_desc,
 620                                                          const char *datalen)
 621 {
 622         struct encrypted_key_payload *epayload = NULL;
 623         unsigned short datablob_len;
 624         unsigned short decrypted_datalen;
 625         unsigned short payload_datalen;
 626         unsigned int encrypted_datalen;
 627         unsigned int format_len;
 628         long dlen;
 629         int ret;
 630
 631         ret = strict_strtol(datalen, 10, &dlen);
 632         if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
 633                 return ERR_PTR(-EINVAL);
 634
 635         format_len = (!format) ? strlen(key_format_default) : strlen(format);
 636         decrypted_datalen = dlen;
 637         payload_datalen = decrypted_datalen;
 638         if (format && !strcmp(format, key_format_ecryptfs)) {
 639                 if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
 640                         pr_err("encrypted_key: keylen for the ecryptfs format "
 641                                "must be equal to %d bytes\n",
 642                                ECRYPTFS_MAX_KEY_BYTES);
 643                         return ERR_PTR(-EINVAL);
 644                 }
 645                 decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
 646                 payload_datalen = sizeof(struct ecryptfs_auth_tok);
 647         }
 648
 649         encrypted_datalen = roundup(decrypted_datalen, blksize);
 650
 651         datablob_len = format_len + 1 + strlen(master_desc) + 1
 652             + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen;
 653
 654         ret = key_payload_reserve(key, payload_datalen + datablob_len
 655                                   + HASH_SIZE + 1);
 656         if (ret < 0)
 657                 return ERR_PTR(ret);
 658
 659         epayload = kzalloc(sizeof(*epayload) + payload_datalen +
 660                            datablob_len + HASH_SIZE + 1, GFP_KERNEL);
 661         if (!epayload)
 662                 return ERR_PTR(-ENOMEM);
 663
 664         epayload->payload_datalen = payload_datalen;
 665         epayload->decrypted_datalen = decrypted_datalen;
 666         epayload->datablob_len = datablob_len;
 667         return epayload;
 668 }
 669
 670 static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
 671                                  const char *format, const char *hex_encoded_iv)
 672 {
 673         struct key *mkey;
 674         u8 derived_key[HASH_SIZE];
 675         u8 *master_key;
 676         u8 *hmac;
 677         const char *hex_encoded_data;
 678         unsigned int encrypted_datalen;
 679         size_t master_keylen;
 680         size_t asciilen;
 681         int ret;
 682
 683         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 684         asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
 685         if (strlen(hex_encoded_iv) != asciilen)
 686                 return -EINVAL;
 687
 688         hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
 689         hex2bin(epayload->iv, hex_encoded_iv, ivsize);
 690         hex2bin(epayload->encrypted_data, hex_encoded_data, encrypted_datalen);
 691
 692         hmac = epayload->format + epayload->datablob_len;
 693         hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2), HASH_SIZE);
 694
 695         mkey = request_master_key(epayload, &master_key, &master_keylen);
 696         if (IS_ERR(mkey))
 697                 return PTR_ERR(mkey);
 698
 699         ret = datablob_hmac_verify(epayload, format, master_key, master_keylen);
 700         if (ret < 0) {
 701                 pr_err("encrypted_key: bad hmac (%d)\n", ret);
 702                 goto out;
 703         }
 704
 705         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 706         if (ret < 0)
 707                 goto out;
 708
 709         ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
 710         if (ret < 0)
 711                 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
 712 out:
 713         up_read(&mkey->sem);
 714         key_put(mkey);
 715         return ret;
 716 }
 717
 718 static void __ekey_init(struct encrypted_key_payload *epayload,
 719                         const char *format, const char *master_desc,
 720                         const char *datalen)
 721 {
 722         unsigned int format_len;
 723
 724         format_len = (!format) ? strlen(key_format_default) : strlen(format);
 725         epayload->format = epayload->payload_data + epayload->payload_datalen;
 726         epayload->master_desc = epayload->format + format_len + 1;
 727         epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
 728         epayload->iv = epayload->datalen + strlen(datalen) + 1;
 729         epayload->encrypted_data = epayload->iv + ivsize + 1;
 730         epayload->decrypted_data = epayload->payload_data;
 731
 732         if (!format)
 733                 memcpy(epayload->format, key_format_default, format_len);
 734         else {
 735                 if (!strcmp(format, key_format_ecryptfs))
 736                         epayload->decrypted_data =
 737                                 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data);
 738
 739                 memcpy(epayload->format, format, format_len);
 740         }
 741
 742         memcpy(epayload->master_desc, master_desc, strlen(master_desc));
 743         memcpy(epayload->datalen, datalen, strlen(datalen));
 744 }
 745
 746 /*
 747  * encrypted_init - initialize an encrypted key
 748  *
 749  * For a new key, use a random number for both the iv and data
 750  * itself.  For an old key, decrypt the hex encoded data.
 751  */
 752 static int encrypted_init(struct encrypted_key_payload *epayload,
 753                           const char *key_desc, const char *format,
 754                           const char *master_desc, const char *datalen,
 755                           const char *hex_encoded_iv)
 756 {
 757         int ret = 0;
 758
 759         if (format && !strcmp(format, key_format_ecryptfs)) {
 760                 ret = valid_ecryptfs_desc(key_desc);
 761                 if (ret < 0)
 762                         return ret;
 763
 764                 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data,
 765                                        key_desc);
 766         }
 767
 768         __ekey_init(epayload, format, master_desc, datalen);
 769         if (!hex_encoded_iv) {
 770                 get_random_bytes(epayload->iv, ivsize);
 771
 772                 get_random_bytes(epayload->decrypted_data,
 773                                  epayload->decrypted_datalen);
 774         } else
 775                 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv);
 776         return ret;
 777 }
 778
 779 /*
 780  * encrypted_instantiate - instantiate an encrypted key
 781  *
 782  * Decrypt an existing encrypted datablob or create a new encrypted key
 783  * based on a kernel random number.
 784  *
 785  * On success, return 0. Otherwise return errno.
 786  */
 787 static int encrypted_instantiate(struct key *key, const void *data,
 788                                  size_t datalen)
 789 {
 790         struct encrypted_key_payload *epayload = NULL;
 791         char *datablob = NULL;
 792         const char *format = NULL;
 793         char *master_desc = NULL;
 794         char *decrypted_datalen = NULL;
 795         char *hex_encoded_iv = NULL;
 796         int ret;
 797
 798         if (datalen <= 0 || datalen > 32767 || !data)
 799                 return -EINVAL;
 800
 801         datablob = kmalloc(datalen + 1, GFP_KERNEL);
 802         if (!datablob)
 803                 return -ENOMEM;
 804         datablob[datalen] = 0;
 805         memcpy(datablob, data, datalen);
 806         ret = datablob_parse(datablob, &format, &master_desc,
 807                              &decrypted_datalen, &hex_encoded_iv);
 808         if (ret < 0)
 809                 goto out;
 810
 811         epayload = encrypted_key_alloc(key, format, master_desc,
 812                                        decrypted_datalen);
 813         if (IS_ERR(epayload)) {
 814                 ret = PTR_ERR(epayload);
 815                 goto out;
 816         }
 817         ret = encrypted_init(epayload, key->description, format, master_desc,
 818                              decrypted_datalen, hex_encoded_iv);
 819         if (ret < 0) {
 820                 kfree(epayload);
 821                 goto out;
 822         }
 823
 824         rcu_assign_pointer(key->payload.data, epayload);
 825 out:
 826         kfree(datablob);
 827         return ret;
 828 }
 829
 830 static void encrypted_rcu_free(struct rcu_head *rcu)
 831 {
 832         struct encrypted_key_payload *epayload;
 833
 834         epayload = container_of(rcu, struct encrypted_key_payload, rcu);
 835         memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
 836         kfree(epayload);
 837 }
 838
 839 /*
 840  * encrypted_update - update the master key description
 841  *
 842  * Change the master key description for an existing encrypted key.
 843  * The next read will return an encrypted datablob using the new
 844  * master key description.
 845  *
 846  * On success, return 0. Otherwise return errno.
 847  */
 848 static int encrypted_update(struct key *key, const void *data, size_t datalen)
 849 {
 850         struct encrypted_key_payload *epayload = key->payload.data;
 851         struct encrypted_key_payload *new_epayload;
 852         char *buf;
 853         char *new_master_desc = NULL;
 854         const char *format = NULL;
 855         int ret = 0;
 856
 857         if (datalen <= 0 || datalen > 32767 || !data)
 858                 return -EINVAL;
 859
 860         buf = kmalloc(datalen + 1, GFP_KERNEL);
 861         if (!buf)
 862                 return -ENOMEM;
 863
 864         buf[datalen] = 0;
 865         memcpy(buf, data, datalen);
 866         ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
 867         if (ret < 0)
 868                 goto out;
 869
 870         ret = valid_master_desc(new_master_desc, epayload->master_desc);
 871         if (ret < 0)
 872                 goto out;
 873
 874         new_epayload = encrypted_key_alloc(key, epayload->format,
 875                                            new_master_desc, epayload->datalen);
 876         if (IS_ERR(new_epayload)) {
 877                 ret = PTR_ERR(new_epayload);
 878                 goto out;
 879         }
 880
 881         __ekey_init(new_epayload, epayload->format, new_master_desc,
 882                     epayload->datalen);
 883
 884         memcpy(new_epayload->iv, epayload->iv, ivsize);
 885         memcpy(new_epayload->payload_data, epayload->payload_data,
 886                epayload->payload_datalen);
 887
 888         rcu_assign_pointer(key->payload.data, new_epayload);
 889         call_rcu(&epayload->rcu, encrypted_rcu_free);
 890 out:
 891         kfree(buf);
 892         return ret;
 893 }
 894
 895 /*
 896  * encrypted_read - format and copy the encrypted data to userspace
 897  *
 898  * The resulting datablob format is:
 899  * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
 900  *
 901  * On success, return to userspace the encrypted key datablob size.
 902  */
 903 static long encrypted_read(const struct key *key, char __user *buffer,
 904                            size_t buflen)
 905 {
 906         struct encrypted_key_payload *epayload;
 907         struct key *mkey;
 908         u8 *master_key;
 909         size_t master_keylen;
 910         char derived_key[HASH_SIZE];
 911         char *ascii_buf;
 912         size_t asciiblob_len;
 913         int ret;
 914
 915         epayload = rcu_dereference_key(key);
 916
 917         /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
 918         asciiblob_len = epayload->datablob_len + ivsize + 1
 919             + roundup(epayload->decrypted_datalen, blksize)
 920             + (HASH_SIZE * 2);
 921
 922         if (!buffer || buflen < asciiblob_len)
 923                 return asciiblob_len;
 924
 925         mkey = request_master_key(epayload, &master_key, &master_keylen);
 926         if (IS_ERR(mkey))
 927                 return PTR_ERR(mkey);
 928
 929         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 930         if (ret < 0)
 931                 goto out;
 932
 933         ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
 934         if (ret < 0)
 935                 goto out;
 936
 937         ret = datablob_hmac_append(epayload, master_key, master_keylen);
 938         if (ret < 0)
 939                 goto out;
 940
 941         ascii_buf = datablob_format(epayload, asciiblob_len);
 942         if (!ascii_buf) {
 943                 ret = -ENOMEM;
 944                 goto out;
 945         }
 946
 947         up_read(&mkey->sem);
 948         key_put(mkey);
 949
 950         if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0)
 951                 ret = -EFAULT;
 952         kfree(ascii_buf);
 953
 954         return asciiblob_len;
 955 out:
 956         up_read(&mkey->sem);
 957         key_put(mkey);
 958         return ret;
 959 }
 960
 961 /*
 962  * encrypted_destroy - before freeing the key, clear the decrypted data
 963  *
 964  * Before freeing the key, clear the memory containing the decrypted
 965  * key data.
 966  */
 967 static void encrypted_destroy(struct key *key)
 968 {
 969         struct encrypted_key_payload *epayload = key->payload.data;
 970
 971         if (!epayload)
 972                 return;
 973
 974         memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
 975         kfree(key->payload.data);
 976 }
 977
 978 struct key_type key_type_encrypted = {
 979         .name = "encrypted",
 980         .instantiate = encrypted_instantiate,
 981         .update = encrypted_update,
 982         .match = user_match,
 983         .destroy = encrypted_destroy,
 984         .describe = user_describe,
 985         .read = encrypted_read,
 986 };
 987 EXPORT_SYMBOL_GPL(key_type_encrypted);
 988
 989 static void encrypted_shash_release(void)
 990 {
 991         if (hashalg)
 992                 crypto_free_shash(hashalg);
 993         if (hmacalg)
 994                 crypto_free_shash(hmacalg);
 995 }
 996
 997 static int __init encrypted_shash_alloc(void)
 998 {
 999         int ret;
1000
1001         hmacalg = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC);
1002         if (IS_ERR(hmacalg)) {
1003                 pr_info("encrypted_key: could not allocate crypto %s\n",
1004                         hmac_alg);
1005                 return PTR_ERR(hmacalg);
1006         }
1007
1008         hashalg = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC);
1009         if (IS_ERR(hashalg)) {
1010                 pr_info("encrypted_key: could not allocate crypto %s\n",
1011                         hash_alg);
1012                 ret = PTR_ERR(hashalg);
1013                 goto hashalg_fail;
1014         }
1015
1016         return 0;
1017
1018 hashalg_fail:
1019         crypto_free_shash(hmacalg);
1020         return ret;
1021 }
1022
1023 static int __init init_encrypted(void)
1024 {
1025         int ret;
1026
1027         ret = encrypted_shash_alloc();
1028         if (ret < 0)
1029                 return ret;
1030         ret = register_key_type(&key_type_encrypted);
1031         if (ret < 0)
1032                 goto out;
1033         return aes_get_sizes();
1034 out:
1035         encrypted_shash_release();
1036         return ret;
1037
1038 }
1039
1040 static void __exit cleanup_encrypted(void)
1041 {
1042         encrypted_shash_release();
1043         unregister_key_type(&key_type_encrypted);
1044 }
1045
1046 late_initcall(init_encrypted);
1047 module_exit(cleanup_encrypted);
1048
1049 MODULE_LICENSE("GPL");