security/keys/encrypted.c

   1 /*
   2  * Copyright (C) 2010 IBM Corporation
   3  *
   4  * Author:
   5  * Mimi Zohar <zohar@us.ibm.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation, version 2 of the License.
  10  *
  11  * See Documentation/keys-trusted-encrypted.txt
  12  */
  13
  14 #include <linux/uaccess.h>
  15 #include <linux/module.h>
  16 #include <linux/init.h>
  17 #include <linux/slab.h>
  18 #include <linux/parser.h>
  19 #include <linux/string.h>
  20 #include <linux/err.h>
  21 #include <keys/user-type.h>
  22 #include <keys/trusted-type.h>
  23 #include <keys/encrypted-type.h>
  24 #include <linux/key-type.h>
  25 #include <linux/random.h>
  26 #include <linux/rcupdate.h>
  27 #include <linux/scatterlist.h>
  28 #include <linux/crypto.h>
  29 #include <crypto/hash.h>
  30 #include <crypto/sha.h>
  31 #include <crypto/aes.h>
  32
  33 #include "encrypted.h"
  34
  35 static const char KEY_TRUSTED_PREFIX[] = "trusted:";
  36 static const char KEY_USER_PREFIX[] = "user:";
  37 static const char hash_alg[] = "sha256";
  38 static const char hmac_alg[] = "hmac(sha256)";
  39 static const char blkcipher_alg[] = "cbc(aes)";
  40 static unsigned int ivsize;
  41 static int blksize;
  42
  43 #define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
  44 #define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
  45 #define HASH_SIZE SHA256_DIGEST_SIZE
  46 #define MAX_DATA_SIZE 4096
  47 #define MIN_DATA_SIZE  20
  48
  49 struct sdesc {
  50         struct shash_desc shash;
  51         char ctx[];
  52 };
  53
  54 static struct crypto_shash *hashalg;
  55 static struct crypto_shash *hmacalg;
  56
  57 enum {
  58         Opt_err = -1, Opt_new, Opt_load, Opt_update
  59 };
  60
  61 static const match_table_t key_tokens = {
  62         {Opt_new, "new"},
  63         {Opt_load, "load"},
  64         {Opt_update, "update"},
  65         {Opt_err, NULL}
  66 };
  67
  68 static int aes_get_sizes(void)
  69 {
  70         struct crypto_blkcipher *tfm;
  71
  72         tfm = crypto_alloc_blkcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
  73         if (IS_ERR(tfm)) {
  74                 pr_err("encrypted_key: failed to alloc_cipher (%ld)\n",
  75                        PTR_ERR(tfm));
  76                 return PTR_ERR(tfm);
  77         }
  78         ivsize = crypto_blkcipher_ivsize(tfm);
  79         blksize = crypto_blkcipher_blocksize(tfm);
  80         crypto_free_blkcipher(tfm);
  81         return 0;
  82 }
  83
  84 /*
  85  * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key
  86  *
  87  * key-type:= "trusted:" | "encrypted:"
  88  * desc:= master-key description
  89  *
  90  * Verify that 'key-type' is valid and that 'desc' exists. On key update,
  91  * only the master key description is permitted to change, not the key-type.
  92  * The key-type remains constant.
  93  *
  94  * On success returns 0, otherwise -EINVAL.
  95  */
  96 static int valid_master_desc(const char *new_desc, const char *orig_desc)
  97 {
  98         if (!memcmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN)) {
  99                 if (strlen(new_desc) == KEY_TRUSTED_PREFIX_LEN)
 100                         goto out;
 101                 if (orig_desc)
 102                         if (memcmp(new_desc, orig_desc, KEY_TRUSTED_PREFIX_LEN))
 103                                 goto out;
 104         } else if (!memcmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN)) {
 105                 if (strlen(new_desc) == KEY_USER_PREFIX_LEN)
 106                         goto out;
 107                 if (orig_desc)
 108                         if (memcmp(new_desc, orig_desc, KEY_USER_PREFIX_LEN))
 109                                 goto out;
 110         } else
 111                 goto out;
 112         return 0;
 113 out:
 114         return -EINVAL;
 115 }
 116
 117 /*
 118  * datablob_parse - parse the keyctl data
 119  *
 120  * datablob format:
 121  * new <master-key name> <decrypted data length>
 122  * load <master-key name> <decrypted data length> <encrypted iv + data>
 123  * update <new-master-key name>
 124  *
 125  * Tokenizes a copy of the keyctl data, returning a pointer to each token,
 126  * which is null terminated.
 127  *
 128  * On success returns 0, otherwise -EINVAL.
 129  */
 130 static int datablob_parse(char *datablob, char **master_desc,
 131                           char **decrypted_datalen, char **hex_encoded_iv)
 132 {
 133         substring_t args[MAX_OPT_ARGS];
 134         int ret = -EINVAL;
 135         int key_cmd;
 136         char *p;
 137
 138         p = strsep(&datablob, " \t");
 139         if (!p)
 140                 return ret;
 141         key_cmd = match_token(p, key_tokens, args);
 142
 143         *master_desc = strsep(&datablob, " \t");
 144         if (!*master_desc)
 145                 goto out;
 146
 147         if (valid_master_desc(*master_desc, NULL) < 0)
 148                 goto out;
 149
 150         if (decrypted_datalen) {
 151                 *decrypted_datalen = strsep(&datablob, " \t");
 152                 if (!*decrypted_datalen)
 153                         goto out;
 154         }
 155
 156         switch (key_cmd) {
 157         case Opt_new:
 158                 if (!decrypted_datalen)
 159                         break;
 160                 ret = 0;
 161                 break;
 162         case Opt_load:
 163                 if (!decrypted_datalen)
 164                         break;
 165                 *hex_encoded_iv = strsep(&datablob, " \t");
 166                 if (!*hex_encoded_iv)
 167                         break;
 168                 ret = 0;
 169                 break;
 170         case Opt_update:
 171                 if (decrypted_datalen)
 172                         break;
 173                 ret = 0;
 174                 break;
 175         case Opt_err:
 176                 break;
 177         }
 178 out:
 179         return ret;
 180 }
 181
 182 /*
 183  * datablob_format - format as an ascii string, before copying to userspace
 184  */
 185 static char *datablob_format(struct encrypted_key_payload *epayload,
 186                              size_t asciiblob_len)
 187 {
 188         char *ascii_buf, *bufp;
 189         u8 *iv = epayload->iv;
 190         int len;
 191         int i;
 192
 193         ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL);
 194         if (!ascii_buf)
 195                 goto out;
 196
 197         ascii_buf[asciiblob_len] = '\0';
 198
 199         /* copy datablob master_desc and datalen strings */
 200         len = sprintf(ascii_buf, "%s %s ", epayload->master_desc,
 201                       epayload->datalen);
 202
 203         /* convert the hex encoded iv, encrypted-data and HMAC to ascii */
 204         bufp = &ascii_buf[len];
 205         for (i = 0; i < (asciiblob_len - len) / 2; i++)
 206                 bufp = pack_hex_byte(bufp, iv[i]);
 207 out:
 208         return ascii_buf;
 209 }
 210
 211 /*
 212  * request_trusted_key - request the trusted key
 213  *
 214  * Trusted keys are sealed to PCRs and other metadata. Although userspace
 215  * manages both trusted/encrypted key-types, like the encrypted key type
 216  * data, trusted key type data is not visible decrypted from userspace.
 217  */
 218 static struct key *request_trusted_key(const char *trusted_desc,
 219                                        u8 **master_key, size_t *master_keylen)
 220 {
 221         struct trusted_key_payload *tpayload;
 222         struct key *tkey;
 223
 224         tkey = request_key(&key_type_trusted, trusted_desc, NULL);
 225         if (IS_ERR(tkey))
 226                 goto error;
 227
 228         down_read(&tkey->sem);
 229         tpayload = rcu_dereference(tkey->payload.data);
 230         *master_key = tpayload->key;
 231         *master_keylen = tpayload->key_len;
 232 error:
 233         return tkey;
 234 }
 235
 236 /*
 237  * request_user_key - request the user key
 238  *
 239  * Use a user provided key to encrypt/decrypt an encrypted-key.
 240  */
 241 static struct key *request_user_key(const char *master_desc, u8 **master_key,
 242                                     size_t *master_keylen)
 243 {
 244         struct user_key_payload *upayload;
 245         struct key *ukey;
 246
 247         ukey = request_key(&key_type_user, master_desc, NULL);
 248         if (IS_ERR(ukey))
 249                 goto error;
 250
 251         down_read(&ukey->sem);
 252         upayload = rcu_dereference(ukey->payload.data);
 253         *master_key = upayload->data;
 254         *master_keylen = upayload->datalen;
 255 error:
 256         return ukey;
 257 }
 258
 259 static struct sdesc *alloc_sdesc(struct crypto_shash *alg)
 260 {
 261         struct sdesc *sdesc;
 262         int size;
 263
 264         size = sizeof(struct shash_desc) + crypto_shash_descsize(alg);
 265         sdesc = kmalloc(size, GFP_KERNEL);
 266         if (!sdesc)
 267                 return ERR_PTR(-ENOMEM);
 268         sdesc->shash.tfm = alg;
 269         sdesc->shash.flags = 0x0;
 270         return sdesc;
 271 }
 272
 273 static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen,
 274                      const u8 *buf, unsigned int buflen)
 275 {
 276         struct sdesc *sdesc;
 277         int ret;
 278
 279         sdesc = alloc_sdesc(hmacalg);
 280         if (IS_ERR(sdesc)) {
 281                 pr_info("encrypted_key: can't alloc %s\n", hmac_alg);
 282                 return PTR_ERR(sdesc);
 283         }
 284
 285         ret = crypto_shash_setkey(hmacalg, key, keylen);
 286         if (!ret)
 287                 ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest);
 288         kfree(sdesc);
 289         return ret;
 290 }
 291
 292 static int calc_hash(u8 *digest, const u8 *buf, unsigned int buflen)
 293 {
 294         struct sdesc *sdesc;
 295         int ret;
 296
 297         sdesc = alloc_sdesc(hashalg);
 298         if (IS_ERR(sdesc)) {
 299                 pr_info("encrypted_key: can't alloc %s\n", hash_alg);
 300                 return PTR_ERR(sdesc);
 301         }
 302
 303         ret = crypto_shash_digest(&sdesc->shash, buf, buflen, digest);
 304         kfree(sdesc);
 305         return ret;
 306 }
 307
 308 enum derived_key_type { ENC_KEY, AUTH_KEY };
 309
 310 /* Derive authentication/encryption key from trusted key */
 311 static int get_derived_key(u8 *derived_key, enum derived_key_type key_type,
 312                            const u8 *master_key, size_t master_keylen)
 313 {
 314         u8 *derived_buf;
 315         unsigned int derived_buf_len;
 316         int ret;
 317
 318         derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen;
 319         if (derived_buf_len < HASH_SIZE)
 320                 derived_buf_len = HASH_SIZE;
 321
 322         derived_buf = kzalloc(derived_buf_len, GFP_KERNEL);
 323         if (!derived_buf) {
 324                 pr_err("encrypted_key: out of memory\n");
 325                 return -ENOMEM;
 326         }
 327         if (key_type)
 328                 strcpy(derived_buf, "AUTH_KEY");
 329         else
 330                 strcpy(derived_buf, "ENC_KEY");
 331
 332         memcpy(derived_buf + strlen(derived_buf) + 1, master_key,
 333                master_keylen);
 334         ret = calc_hash(derived_key, derived_buf, derived_buf_len);
 335         kfree(derived_buf);
 336         return ret;
 337 }
 338
 339 static int init_blkcipher_desc(struct blkcipher_desc *desc, const u8 *key,
 340                                unsigned int key_len, const u8 *iv,
 341                                unsigned int ivsize)
 342 {
 343         int ret;
 344
 345         desc->tfm = crypto_alloc_blkcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
 346         if (IS_ERR(desc->tfm)) {
 347                 pr_err("encrypted_key: failed to load %s transform (%ld)\n",
 348                        blkcipher_alg, PTR_ERR(desc->tfm));
 349                 return PTR_ERR(desc->tfm);
 350         }
 351         desc->flags = 0;
 352
 353         ret = crypto_blkcipher_setkey(desc->tfm, key, key_len);
 354         if (ret < 0) {
 355                 pr_err("encrypted_key: failed to setkey (%d)\n", ret);
 356                 crypto_free_blkcipher(desc->tfm);
 357                 return ret;
 358         }
 359         crypto_blkcipher_set_iv(desc->tfm, iv, ivsize);
 360         return 0;
 361 }
 362
 363 static struct key *request_master_key(struct encrypted_key_payload *epayload,
 364                                       u8 **master_key, size_t *master_keylen)
 365 {
 366         struct key *mkey = NULL;
 367
 368         if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX,
 369                      KEY_TRUSTED_PREFIX_LEN)) {
 370                 mkey = request_trusted_key(epayload->master_desc +
 371                                            KEY_TRUSTED_PREFIX_LEN,
 372                                            master_key, master_keylen);
 373         } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX,
 374                             KEY_USER_PREFIX_LEN)) {
 375                 mkey = request_user_key(epayload->master_desc +
 376                                         KEY_USER_PREFIX_LEN,
 377                                         master_key, master_keylen);
 378         } else
 379                 goto out;
 380
 381         if (IS_ERR(mkey))
 382                 pr_info("encrypted_key: key %s not found",
 383                         epayload->master_desc);
 384         if (mkey)
 385                 dump_master_key(*master_key, *master_keylen);
 386 out:
 387         return mkey;
 388 }
 389
 390 /* Before returning data to userspace, encrypt decrypted data. */
 391 static int derived_key_encrypt(struct encrypted_key_payload *epayload,
 392                                const u8 *derived_key,
 393                                unsigned int derived_keylen)
 394 {
 395         struct scatterlist sg_in[2];
 396         struct scatterlist sg_out[1];
 397         struct blkcipher_desc desc;
 398         unsigned int encrypted_datalen;
 399         unsigned int padlen;
 400         char pad[16];
 401         int ret;
 402
 403         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 404         padlen = encrypted_datalen - epayload->decrypted_datalen;
 405
 406         ret = init_blkcipher_desc(&desc, derived_key, derived_keylen,
 407                                   epayload->iv, ivsize);
 408         if (ret < 0)
 409                 goto out;
 410         dump_decrypted_data(epayload);
 411
 412         memset(pad, 0, sizeof pad);
 413         sg_init_table(sg_in, 2);
 414         sg_set_buf(&sg_in[0], epayload->decrypted_data,
 415                    epayload->decrypted_datalen);
 416         sg_set_buf(&sg_in[1], pad, padlen);
 417
 418         sg_init_table(sg_out, 1);
 419         sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
 420
 421         ret = crypto_blkcipher_encrypt(&desc, sg_out, sg_in, encrypted_datalen);
 422         crypto_free_blkcipher(desc.tfm);
 423         if (ret < 0)
 424                 pr_err("encrypted_key: failed to encrypt (%d)\n", ret);
 425         else
 426                 dump_encrypted_data(epayload, encrypted_datalen);
 427 out:
 428         return ret;
 429 }
 430
 431 static int datablob_hmac_append(struct encrypted_key_payload *epayload,
 432                                 const u8 *master_key, size_t master_keylen)
 433 {
 434         u8 derived_key[HASH_SIZE];
 435         u8 *digest;
 436         int ret;
 437
 438         ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 439         if (ret < 0)
 440                 goto out;
 441
 442         digest = epayload->master_desc + epayload->datablob_len;
 443         ret = calc_hmac(digest, derived_key, sizeof derived_key,
 444                         epayload->master_desc, epayload->datablob_len);
 445         if (!ret)
 446                 dump_hmac(NULL, digest, HASH_SIZE);
 447 out:
 448         return ret;
 449 }
 450
 451 /* verify HMAC before decrypting encrypted key */
 452 static int datablob_hmac_verify(struct encrypted_key_payload *epayload,
 453                                 const u8 *master_key, size_t master_keylen)
 454 {
 455         u8 derived_key[HASH_SIZE];
 456         u8 digest[HASH_SIZE];
 457         int ret;
 458
 459         ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen);
 460         if (ret < 0)
 461                 goto out;
 462
 463         ret = calc_hmac(digest, derived_key, sizeof derived_key,
 464                         epayload->master_desc, epayload->datablob_len);
 465         if (ret < 0)
 466                 goto out;
 467         ret = memcmp(digest, epayload->master_desc + epayload->datablob_len,
 468                      sizeof digest);
 469         if (ret) {
 470                 ret = -EINVAL;
 471                 dump_hmac("datablob",
 472                           epayload->master_desc + epayload->datablob_len,
 473                           HASH_SIZE);
 474                 dump_hmac("calc", digest, HASH_SIZE);
 475         }
 476 out:
 477         return ret;
 478 }
 479
 480 static int derived_key_decrypt(struct encrypted_key_payload *epayload,
 481                                const u8 *derived_key,
 482                                unsigned int derived_keylen)
 483 {
 484         struct scatterlist sg_in[1];
 485         struct scatterlist sg_out[2];
 486         struct blkcipher_desc desc;
 487         unsigned int encrypted_datalen;
 488         char pad[16];
 489         int ret;
 490
 491         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 492         ret = init_blkcipher_desc(&desc, derived_key, derived_keylen,
 493                                   epayload->iv, ivsize);
 494         if (ret < 0)
 495                 goto out;
 496         dump_encrypted_data(epayload, encrypted_datalen);
 497
 498         memset(pad, 0, sizeof pad);
 499         sg_init_table(sg_in, 1);
 500         sg_init_table(sg_out, 2);
 501         sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
 502         sg_set_buf(&sg_out[0], epayload->decrypted_data,
 503                    epayload->decrypted_datalen);
 504         sg_set_buf(&sg_out[1], pad, sizeof pad);
 505
 506         ret = crypto_blkcipher_decrypt(&desc, sg_out, sg_in, encrypted_datalen);
 507         crypto_free_blkcipher(desc.tfm);
 508         if (ret < 0)
 509                 goto out;
 510         dump_decrypted_data(epayload);
 511 out:
 512         return ret;
 513 }
 514
 515 /* Allocate memory for decrypted key and datablob. */
 516 static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
 517                                                          const char *master_desc,
 518                                                          const char *datalen)
 519 {
 520         struct encrypted_key_payload *epayload = NULL;
 521         unsigned short datablob_len;
 522         unsigned short decrypted_datalen;
 523         unsigned int encrypted_datalen;
 524         long dlen;
 525         int ret;
 526
 527         ret = strict_strtol(datalen, 10, &dlen);
 528         if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE)
 529                 return ERR_PTR(-EINVAL);
 530
 531         decrypted_datalen = dlen;
 532         encrypted_datalen = roundup(decrypted_datalen, blksize);
 533
 534         datablob_len = strlen(master_desc) + 1 + strlen(datalen) + 1
 535             + ivsize + 1 + encrypted_datalen;
 536
 537         ret = key_payload_reserve(key, decrypted_datalen + datablob_len
 538                                   + HASH_SIZE + 1);
 539         if (ret < 0)
 540                 return ERR_PTR(ret);
 541
 542         epayload = kzalloc(sizeof(*epayload) + decrypted_datalen +
 543                            datablob_len + HASH_SIZE + 1, GFP_KERNEL);
 544         if (!epayload)
 545                 return ERR_PTR(-ENOMEM);
 546
 547         epayload->decrypted_datalen = decrypted_datalen;
 548         epayload->datablob_len = datablob_len;
 549         return epayload;
 550 }
 551
 552 static int encrypted_key_decrypt(struct encrypted_key_payload *epayload,
 553                                  const char *hex_encoded_iv)
 554 {
 555         struct key *mkey;
 556         u8 derived_key[HASH_SIZE];
 557         u8 *master_key;
 558         u8 *hmac;
 559         const char *hex_encoded_data;
 560         unsigned int encrypted_datalen;
 561         size_t master_keylen;
 562         size_t asciilen;
 563         int ret;
 564
 565         encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 566         asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2;
 567         if (strlen(hex_encoded_iv) != asciilen)
 568                 return -EINVAL;
 569
 570         hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2;
 571         hex2bin(epayload->iv, hex_encoded_iv, ivsize);
 572         hex2bin(epayload->encrypted_data, hex_encoded_data, encrypted_datalen);
 573
 574         hmac = epayload->master_desc + epayload->datablob_len;
 575         hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2), HASH_SIZE);
 576
 577         mkey = request_master_key(epayload, &master_key, &master_keylen);
 578         if (IS_ERR(mkey))
 579                 return PTR_ERR(mkey);
 580
 581         ret = datablob_hmac_verify(epayload, master_key, master_keylen);
 582         if (ret < 0) {
 583                 pr_err("encrypted_key: bad hmac (%d)\n", ret);
 584                 goto out;
 585         }
 586
 587         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 588         if (ret < 0)
 589                 goto out;
 590
 591         ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key);
 592         if (ret < 0)
 593                 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret);
 594 out:
 595         up_read(&mkey->sem);
 596         key_put(mkey);
 597         return ret;
 598 }
 599
 600 static void __ekey_init(struct encrypted_key_payload *epayload,
 601                         const char *master_desc, const char *datalen)
 602 {
 603         epayload->master_desc = epayload->decrypted_data
 604             + epayload->decrypted_datalen;
 605         epayload->datalen = epayload->master_desc + strlen(master_desc) + 1;
 606         epayload->iv = epayload->datalen + strlen(datalen) + 1;
 607         epayload->encrypted_data = epayload->iv + ivsize + 1;
 608
 609         memcpy(epayload->master_desc, master_desc, strlen(master_desc));
 610         memcpy(epayload->datalen, datalen, strlen(datalen));
 611 }
 612
 613 /*
 614  * encrypted_init - initialize an encrypted key
 615  *
 616  * For a new key, use a random number for both the iv and data
 617  * itself.  For an old key, decrypt the hex encoded data.
 618  */
 619 static int encrypted_init(struct encrypted_key_payload *epayload,
 620                           const char *master_desc, const char *datalen,
 621                           const char *hex_encoded_iv)
 622 {
 623         int ret = 0;
 624
 625         __ekey_init(epayload, master_desc, datalen);
 626         if (!hex_encoded_iv) {
 627                 get_random_bytes(epayload->iv, ivsize);
 628
 629                 get_random_bytes(epayload->decrypted_data,
 630                                  epayload->decrypted_datalen);
 631         } else
 632                 ret = encrypted_key_decrypt(epayload, hex_encoded_iv);
 633         return ret;
 634 }
 635
 636 /*
 637  * encrypted_instantiate - instantiate an encrypted key
 638  *
 639  * Decrypt an existing encrypted datablob or create a new encrypted key
 640  * based on a kernel random number.
 641  *
 642  * On success, return 0. Otherwise return errno.
 643  */
 644 static int encrypted_instantiate(struct key *key, const void *data,
 645                                  size_t datalen)
 646 {
 647         struct encrypted_key_payload *epayload = NULL;
 648         char *datablob = NULL;
 649         char *master_desc = NULL;
 650         char *decrypted_datalen = NULL;
 651         char *hex_encoded_iv = NULL;
 652         int ret;
 653
 654         if (datalen <= 0 || datalen > 32767 || !data)
 655                 return -EINVAL;
 656
 657         datablob = kmalloc(datalen + 1, GFP_KERNEL);
 658         if (!datablob)
 659                 return -ENOMEM;
 660         datablob[datalen] = 0;
 661         memcpy(datablob, data, datalen);
 662         ret = datablob_parse(datablob, &master_desc, &decrypted_datalen,
 663                              &hex_encoded_iv);
 664         if (ret < 0)
 665                 goto out;
 666
 667         epayload = encrypted_key_alloc(key, master_desc, decrypted_datalen);
 668         if (IS_ERR(epayload)) {
 669                 ret = PTR_ERR(epayload);
 670                 goto out;
 671         }
 672         ret = encrypted_init(epayload, master_desc, decrypted_datalen,
 673                              hex_encoded_iv);
 674         if (ret < 0) {
 675                 kfree(epayload);
 676                 goto out;
 677         }
 678
 679         rcu_assign_pointer(key->payload.data, epayload);
 680 out:
 681         kfree(datablob);
 682         return ret;
 683 }
 684
 685 static void encrypted_rcu_free(struct rcu_head *rcu)
 686 {
 687         struct encrypted_key_payload *epayload;
 688
 689         epayload = container_of(rcu, struct encrypted_key_payload, rcu);
 690         memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
 691         kfree(epayload);
 692 }
 693
 694 /*
 695  * encrypted_update - update the master key description
 696  *
 697  * Change the master key description for an existing encrypted key.
 698  * The next read will return an encrypted datablob using the new
 699  * master key description.
 700  *
 701  * On success, return 0. Otherwise return errno.
 702  */
 703 static int encrypted_update(struct key *key, const void *data, size_t datalen)
 704 {
 705         struct encrypted_key_payload *epayload = key->payload.data;
 706         struct encrypted_key_payload *new_epayload;
 707         char *buf;
 708         char *new_master_desc = NULL;
 709         int ret = 0;
 710
 711         if (datalen <= 0 || datalen > 32767 || !data)
 712                 return -EINVAL;
 713
 714         buf = kmalloc(datalen + 1, GFP_KERNEL);
 715         if (!buf)
 716                 return -ENOMEM;
 717
 718         buf[datalen] = 0;
 719         memcpy(buf, data, datalen);
 720         ret = datablob_parse(buf, &new_master_desc, NULL, NULL);
 721         if (ret < 0)
 722                 goto out;
 723
 724         ret = valid_master_desc(new_master_desc, epayload->master_desc);
 725         if (ret < 0)
 726                 goto out;
 727
 728         new_epayload = encrypted_key_alloc(key, new_master_desc,
 729                                            epayload->datalen);
 730         if (IS_ERR(new_epayload)) {
 731                 ret = PTR_ERR(new_epayload);
 732                 goto out;
 733         }
 734
 735         __ekey_init(new_epayload, new_master_desc, epayload->datalen);
 736
 737         memcpy(new_epayload->iv, epayload->iv, ivsize);
 738         memcpy(new_epayload->decrypted_data, epayload->decrypted_data,
 739                epayload->decrypted_datalen);
 740
 741         rcu_assign_pointer(key->payload.data, new_epayload);
 742         call_rcu(&epayload->rcu, encrypted_rcu_free);
 743 out:
 744         kfree(buf);
 745         return ret;
 746 }
 747
 748 /*
 749  * encrypted_read - format and copy the encrypted data to userspace
 750  *
 751  * The resulting datablob format is:
 752  * <master-key name> <decrypted data length> <encrypted iv> <encrypted data>
 753  *
 754  * On success, return to userspace the encrypted key datablob size.
 755  */
 756 static long encrypted_read(const struct key *key, char __user *buffer,
 757                            size_t buflen)
 758 {
 759         struct encrypted_key_payload *epayload;
 760         struct key *mkey;
 761         u8 *master_key;
 762         size_t master_keylen;
 763         char derived_key[HASH_SIZE];
 764         char *ascii_buf;
 765         size_t asciiblob_len;
 766         int ret;
 767
 768         epayload = rcu_dereference_protected(key->payload.data,
 769                                   rwsem_is_locked(&((struct key *)key)->sem));
 770
 771         /* returns the hex encoded iv, encrypted-data, and hmac as ascii */
 772         asciiblob_len = epayload->datablob_len + ivsize + 1
 773             + roundup(epayload->decrypted_datalen, blksize)
 774             + (HASH_SIZE * 2);
 775
 776         if (!buffer || buflen < asciiblob_len)
 777                 return asciiblob_len;
 778
 779         mkey = request_master_key(epayload, &master_key, &master_keylen);
 780         if (IS_ERR(mkey))
 781                 return PTR_ERR(mkey);
 782
 783         ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen);
 784         if (ret < 0)
 785                 goto out;
 786
 787         ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key);
 788         if (ret < 0)
 789                 goto out;
 790
 791         ret = datablob_hmac_append(epayload, master_key, master_keylen);
 792         if (ret < 0)
 793                 goto out;
 794
 795         ascii_buf = datablob_format(epayload, asciiblob_len);
 796         if (!ascii_buf) {
 797                 ret = -ENOMEM;
 798                 goto out;
 799         }
 800
 801         up_read(&mkey->sem);
 802         key_put(mkey);
 803
 804         if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0)
 805                 ret = -EFAULT;
 806         kfree(ascii_buf);
 807
 808         return asciiblob_len;
 809 out:
 810         up_read(&mkey->sem);
 811         key_put(mkey);
 812         return ret;
 813 }
 814
 815 /*
 816  * encrypted_destroy - before freeing the key, clear the decrypted data
 817  *
 818  * Before freeing the key, clear the memory containing the decrypted
 819  * key data.
 820  */
 821 static void encrypted_destroy(struct key *key)
 822 {
 823         struct encrypted_key_payload *epayload = key->payload.data;
 824
 825         if (!epayload)
 826                 return;
 827
 828         memset(epayload->decrypted_data, 0, epayload->decrypted_datalen);
 829         kfree(key->payload.data);
 830 }
 831
 832 struct key_type key_type_encrypted = {
 833         .name = "encrypted",
 834         .instantiate = encrypted_instantiate,
 835         .update = encrypted_update,
 836         .match = user_match,
 837         .destroy = encrypted_destroy,
 838         .describe = user_describe,
 839         .read = encrypted_read,
 840 };
 841 EXPORT_SYMBOL_GPL(key_type_encrypted);
 842
 843 static void encrypted_shash_release(void)
 844 {
 845         if (hashalg)
 846                 crypto_free_shash(hashalg);
 847         if (hmacalg)
 848                 crypto_free_shash(hmacalg);
 849 }
 850
 851 static int __init encrypted_shash_alloc(void)
 852 {
 853         int ret;
 854
 855         hmacalg = crypto_alloc_shash(hmac_alg, 0, CRYPTO_ALG_ASYNC);
 856         if (IS_ERR(hmacalg)) {
 857                 pr_info("encrypted_key: could not allocate crypto %s\n",
 858                         hmac_alg);
 859                 return PTR_ERR(hmacalg);
 860         }
 861
 862         hashalg = crypto_alloc_shash(hash_alg, 0, CRYPTO_ALG_ASYNC);
 863         if (IS_ERR(hashalg)) {
 864                 pr_info("encrypted_key: could not allocate crypto %s\n",
 865                         hash_alg);
 866                 ret = PTR_ERR(hashalg);
 867                 goto hashalg_fail;
 868         }
 869
 870         return 0;
 871
 872 hashalg_fail:
 873         crypto_free_shash(hmacalg);
 874         return ret;
 875 }
 876
 877 static int __init init_encrypted(void)
 878 {
 879         int ret;
 880
 881         ret = encrypted_shash_alloc();
 882         if (ret < 0)
 883                 return ret;
 884         ret = register_key_type(&key_type_encrypted);
 885         if (ret < 0)
 886                 goto out;
 887         return aes_get_sizes();
 888 out:
 889         encrypted_shash_release();
 890         return ret;
 891
 892 }
 893
 894 static void __exit cleanup_encrypted(void)
 895 {
 896         encrypted_shash_release();
 897         unregister_key_type(&key_type_encrypted);
 898 }
 899
 900 late_initcall(init_encrypted);
 901 module_exit(cleanup_encrypted);
 902
 903 MODULE_LICENSE("GPL");