security/integrity/ima/ima_crypto.c

   1 /*
   2  * Copyright (C) 2005,2006,2007,2008 IBM Corporation
   3  *
   4  * Authors:
   5  * Mimi Zohar <zohar@us.ibm.com>
   6  * Kylene Hall <kjhall@us.ibm.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation, version 2 of the License.
  11  *
  12  * File: ima_crypto.c
  13  *      Calculates md5/sha1 file hash, template hash, boot-aggreate hash
  14  */
  15
  16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17
  18 #include <linux/kernel.h>
  19 #include <linux/moduleparam.h>
  20 #include <linux/ratelimit.h>
  21 #include <linux/file.h>
  22 #include <linux/crypto.h>
  23 #include <linux/scatterlist.h>
  24 #include <linux/err.h>
  25 #include <linux/slab.h>
  26 #include <crypto/hash.h>
  27
  28 #include "ima.h"
  29
  30 /* minimum file size for ahash use */
  31 static unsigned long ima_ahash_minsize;
  32 module_param_named(ahash_minsize, ima_ahash_minsize, ulong, 0644);
  33 MODULE_PARM_DESC(ahash_minsize, "Minimum file size for ahash use");
  34
  35 /* default is 0 - 1 page. */
  36 static int ima_maxorder;
  37 static unsigned int ima_bufsize = PAGE_SIZE;
  38
  39 static int param_set_bufsize(const char *val, const struct kernel_param *kp)
  40 {
  41         unsigned long long size;
  42         int order;
  43
  44         size = memparse(val, NULL);
  45         order = get_order(size);
  46         if (order >= MAX_ORDER)
  47                 return -EINVAL;
  48         ima_maxorder = order;
  49         ima_bufsize = PAGE_SIZE << order;
  50         return 0;
  51 }
  52
  53 static const struct kernel_param_ops param_ops_bufsize = {
  54         .set = param_set_bufsize,
  55         .get = param_get_uint,
  56 };
  57 #define param_check_bufsize(name, p) __param_check(name, p, unsigned int)
  58
  59 module_param_named(ahash_bufsize, ima_bufsize, bufsize, 0644);
  60 MODULE_PARM_DESC(ahash_bufsize, "Maximum ahash buffer size");
  61
  62 static struct crypto_shash *ima_shash_tfm;
  63 static struct crypto_ahash *ima_ahash_tfm;
  64
  65 int __init ima_init_crypto(void)
  66 {
  67         long rc;
  68
  69         ima_shash_tfm = crypto_alloc_shash(hash_algo_name[ima_hash_algo], 0, 0);
  70         if (IS_ERR(ima_shash_tfm)) {
  71                 rc = PTR_ERR(ima_shash_tfm);
  72                 pr_err("Can not allocate %s (reason: %ld)\n",
  73                        hash_algo_name[ima_hash_algo], rc);
  74                 return rc;
  75         }
  76         pr_info("Allocated hash algorithm: %s\n",
  77                 hash_algo_name[ima_hash_algo]);
  78         return 0;
  79 }
  80
  81 static struct crypto_shash *ima_alloc_tfm(enum hash_algo algo)
  82 {
  83         struct crypto_shash *tfm = ima_shash_tfm;
  84         int rc;
  85
  86         if (algo < 0 || algo >= HASH_ALGO__LAST)
  87                 algo = ima_hash_algo;
  88
  89         if (algo != ima_hash_algo) {
  90                 tfm = crypto_alloc_shash(hash_algo_name[algo], 0, 0);
  91                 if (IS_ERR(tfm)) {
  92                         rc = PTR_ERR(tfm);
  93                         pr_err("Can not allocate %s (reason: %d)\n",
  94                                hash_algo_name[algo], rc);
  95                 }
  96         }
  97         return tfm;
  98 }
  99
 100 static void ima_free_tfm(struct crypto_shash *tfm)
 101 {
 102         if (tfm != ima_shash_tfm)
 103                 crypto_free_shash(tfm);
 104 }
 105
 106 /**
 107  * ima_alloc_pages() - Allocate contiguous pages.
 108  * @max_size:       Maximum amount of memory to allocate.
 109  * @allocated_size: Returned size of actual allocation.
 110  * @last_warn:      Should the min_size allocation warn or not.
 111  *
 112  * Tries to do opportunistic allocation for memory first trying to allocate
 113  * max_size amount of memory and then splitting that until zero order is
 114  * reached. Allocation is tried without generating allocation warnings unless
 115  * last_warn is set. Last_warn set affects only last allocation of zero order.
 116  *
 117  * By default, ima_maxorder is 0 and it is equivalent to kmalloc(GFP_KERNEL)
 118  *
 119  * Return pointer to allocated memory, or NULL on failure.
 120  */
 121 static void *ima_alloc_pages(loff_t max_size, size_t *allocated_size,
 122                              int last_warn)
 123 {
 124         void *ptr;
 125         int order = ima_maxorder;
 126         gfp_t gfp_mask = __GFP_RECLAIM | __GFP_NOWARN | __GFP_NORETRY;
 127
 128         if (order)
 129                 order = min(get_order(max_size), order);
 130
 131         for (; order; order--) {
 132                 ptr = (void *)__get_free_pages(gfp_mask, order);
 133                 if (ptr) {
 134                         *allocated_size = PAGE_SIZE << order;
 135                         return ptr;
 136                 }
 137         }
 138
 139         /* order is zero - one page */
 140
 141         gfp_mask = GFP_KERNEL;
 142
 143         if (!last_warn)
 144                 gfp_mask |= __GFP_NOWARN;
 145
 146         ptr = (void *)__get_free_pages(gfp_mask, 0);
 147         if (ptr) {
 148                 *allocated_size = PAGE_SIZE;
 149                 return ptr;
 150         }
 151
 152         *allocated_size = 0;
 153         return NULL;
 154 }
 155
 156 /**
 157  * ima_free_pages() - Free pages allocated by ima_alloc_pages().
 158  * @ptr:  Pointer to allocated pages.
 159  * @size: Size of allocated buffer.
 160  */
 161 static void ima_free_pages(void *ptr, size_t size)
 162 {
 163         if (!ptr)
 164                 return;
 165         free_pages((unsigned long)ptr, get_order(size));
 166 }
 167
 168 static struct crypto_ahash *ima_alloc_atfm(enum hash_algo algo)
 169 {
 170         struct crypto_ahash *tfm = ima_ahash_tfm;
 171         int rc;
 172
 173         if (algo < 0 || algo >= HASH_ALGO__LAST)
 174                 algo = ima_hash_algo;
 175
 176         if (algo != ima_hash_algo || !tfm) {
 177                 tfm = crypto_alloc_ahash(hash_algo_name[algo], 0, 0);
 178                 if (!IS_ERR(tfm)) {
 179                         if (algo == ima_hash_algo)
 180                                 ima_ahash_tfm = tfm;
 181                 } else {
 182                         rc = PTR_ERR(tfm);
 183                         pr_err("Can not allocate %s (reason: %d)\n",
 184                                hash_algo_name[algo], rc);
 185                 }
 186         }
 187         return tfm;
 188 }
 189
 190 static void ima_free_atfm(struct crypto_ahash *tfm)
 191 {
 192         if (tfm != ima_ahash_tfm)
 193                 crypto_free_ahash(tfm);
 194 }
 195
 196 static inline int ahash_wait(int err, struct crypto_wait *wait)
 197 {
 198
 199         err = crypto_wait_req(err, wait);
 200
 201         if (err)
 202                 pr_crit_ratelimited("ahash calculation failed: err: %d\n", err);
 203
 204         return err;
 205 }
 206
 207 static int ima_calc_file_hash_atfm(struct file *file,
 208                                    struct ima_digest_data *hash,
 209                                    struct crypto_ahash *tfm)
 210 {
 211         loff_t i_size, offset;
 212         char *rbuf[2] = { NULL, };
 213         int rc, rbuf_len, active = 0, ahash_rc = 0;
 214         struct ahash_request *req;
 215         struct scatterlist sg[1];
 216         struct crypto_wait wait;
 217         size_t rbuf_size[2];
 218
 219         hash->length = crypto_ahash_digestsize(tfm);
 220
 221         req = ahash_request_alloc(tfm, GFP_KERNEL);
 222         if (!req)
 223                 return -ENOMEM;
 224
 225         crypto_init_wait(&wait);
 226         ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
 227                                    CRYPTO_TFM_REQ_MAY_SLEEP,
 228                                    crypto_req_done, &wait);
 229
 230         rc = ahash_wait(crypto_ahash_init(req), &wait);
 231         if (rc)
 232                 goto out1;
 233
 234         i_size = i_size_read(file_inode(file));
 235
 236         if (i_size == 0)
 237                 goto out2;
 238
 239         /*
 240          * Try to allocate maximum size of memory.
 241          * Fail if even a single page cannot be allocated.
 242          */
 243         rbuf[0] = ima_alloc_pages(i_size, &rbuf_size[0], 1);
 244         if (!rbuf[0]) {
 245                 rc = -ENOMEM;
 246                 goto out1;
 247         }
 248
 249         /* Only allocate one buffer if that is enough. */
 250         if (i_size > rbuf_size[0]) {
 251                 /*
 252                  * Try to allocate secondary buffer. If that fails fallback to
 253                  * using single buffering. Use previous memory allocation size
 254                  * as baseline for possible allocation size.
 255                  */
 256                 rbuf[1] = ima_alloc_pages(i_size - rbuf_size[0],
 257                                           &rbuf_size[1], 0);
 258         }
 259
 260         for (offset = 0; offset < i_size; offset += rbuf_len) {
 261                 if (!rbuf[1] && offset) {
 262                         /* Not using two buffers, and it is not the first
 263                          * read/request, wait for the completion of the
 264                          * previous ahash_update() request.
 265                          */
 266                         rc = ahash_wait(ahash_rc, &wait);
 267                         if (rc)
 268                                 goto out3;
 269                 }
 270                 /* read buffer */
 271                 rbuf_len = min_t(loff_t, i_size - offset, rbuf_size[active]);
 272                 rc = integrity_kernel_read(file, offset, rbuf[active],
 273                                            rbuf_len);
 274                 if (rc != rbuf_len) {
 275                         if (rc >= 0)
 276                                 rc = -EINVAL;
 277                         /*
 278                          * Forward current rc, do not overwrite with return value
 279                          * from ahash_wait()
 280                          */
 281                         ahash_wait(ahash_rc, &wait);
 282                         goto out3;
 283                 }
 284
 285                 if (rbuf[1] && offset) {
 286                         /* Using two buffers, and it is not the first
 287                          * read/request, wait for the completion of the
 288                          * previous ahash_update() request.
 289                          */
 290                         rc = ahash_wait(ahash_rc, &wait);
 291                         if (rc)
 292                                 goto out3;
 293                 }
 294
 295                 sg_init_one(&sg[0], rbuf[active], rbuf_len);
 296                 ahash_request_set_crypt(req, sg, NULL, rbuf_len);
 297
 298                 ahash_rc = crypto_ahash_update(req);
 299
 300                 if (rbuf[1])
 301                         active = !active; /* swap buffers, if we use two */
 302         }
 303         /* wait for the last update request to complete */
 304         rc = ahash_wait(ahash_rc, &wait);
 305 out3:
 306         ima_free_pages(rbuf[0], rbuf_size[0]);
 307         ima_free_pages(rbuf[1], rbuf_size[1]);
 308 out2:
 309         if (!rc) {
 310                 ahash_request_set_crypt(req, NULL, hash->digest, 0);
 311                 rc = ahash_wait(crypto_ahash_final(req), &wait);
 312         }
 313 out1:
 314         ahash_request_free(req);
 315         return rc;
 316 }
 317
 318 static int ima_calc_file_ahash(struct file *file, struct ima_digest_data *hash)
 319 {
 320         struct crypto_ahash *tfm;
 321         int rc;
 322
 323         tfm = ima_alloc_atfm(hash->algo);
 324         if (IS_ERR(tfm))
 325                 return PTR_ERR(tfm);
 326
 327         rc = ima_calc_file_hash_atfm(file, hash, tfm);
 328
 329         ima_free_atfm(tfm);
 330
 331         return rc;
 332 }
 333
 334 static int ima_calc_file_hash_tfm(struct file *file,
 335                                   struct ima_digest_data *hash,
 336                                   struct crypto_shash *tfm)
 337 {
 338         loff_t i_size, offset = 0;
 339         char *rbuf;
 340         int rc;
 341         SHASH_DESC_ON_STACK(shash, tfm);
 342
 343         shash->tfm = tfm;
 344         shash->flags = 0;
 345
 346         hash->length = crypto_shash_digestsize(tfm);
 347
 348         rc = crypto_shash_init(shash);
 349         if (rc != 0)
 350                 return rc;
 351
 352         i_size = i_size_read(file_inode(file));
 353
 354         if (i_size == 0)
 355                 goto out;
 356
 357         rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
 358         if (!rbuf)
 359                 return -ENOMEM;
 360
 361         while (offset < i_size) {
 362                 int rbuf_len;
 363
 364                 rbuf_len = integrity_kernel_read(file, offset, rbuf, PAGE_SIZE);
 365                 if (rbuf_len < 0) {
 366                         rc = rbuf_len;
 367                         break;
 368                 }
 369                 if (rbuf_len == 0)
 370                         break;
 371                 offset += rbuf_len;
 372
 373                 rc = crypto_shash_update(shash, rbuf, rbuf_len);
 374                 if (rc)
 375                         break;
 376         }
 377         kfree(rbuf);
 378 out:
 379         if (!rc)
 380                 rc = crypto_shash_final(shash, hash->digest);
 381         return rc;
 382 }
 383
 384 static int ima_calc_file_shash(struct file *file, struct ima_digest_data *hash)
 385 {
 386         struct crypto_shash *tfm;
 387         int rc;
 388
 389         tfm = ima_alloc_tfm(hash->algo);
 390         if (IS_ERR(tfm))
 391                 return PTR_ERR(tfm);
 392
 393         rc = ima_calc_file_hash_tfm(file, hash, tfm);
 394
 395         ima_free_tfm(tfm);
 396
 397         return rc;
 398 }
 399
 400 /*
 401  * ima_calc_file_hash - calculate file hash
 402  *
 403  * Asynchronous hash (ahash) allows using HW acceleration for calculating
 404  * a hash. ahash performance varies for different data sizes on different
 405  * crypto accelerators. shash performance might be better for smaller files.
 406  * The 'ima.ahash_minsize' module parameter allows specifying the best
 407  * minimum file size for using ahash on the system.
 408  *
 409  * If the ima.ahash_minsize parameter is not specified, this function uses
 410  * shash for the hash calculation.  If ahash fails, it falls back to using
 411  * shash.
 412  */
 413 int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash)
 414 {
 415         loff_t i_size;
 416         int rc;
 417         struct file *f = file;
 418         bool new_file_instance = false, modified_mode = false;
 419
 420         /*
 421          * For consistency, fail file's opened with the O_DIRECT flag on
 422          * filesystems mounted with/without DAX option.
 423          */
 424         if (file->f_flags & O_DIRECT) {
 425                 hash->length = hash_digest_size[ima_hash_algo];
 426                 hash->algo = ima_hash_algo;
 427                 return -EINVAL;
 428         }
 429
 430         /* Open a new file instance in O_RDONLY if we cannot read */
 431         if (!(file->f_mode & FMODE_READ)) {
 432                 int flags = file->f_flags & ~(O_WRONLY | O_APPEND |
 433                                 O_TRUNC | O_CREAT | O_NOCTTY | O_EXCL);
 434                 flags |= O_RDONLY;
 435                 f = dentry_open(&file->f_path, flags, file->f_cred);
 436                 if (IS_ERR(f)) {
 437                         /*
 438                          * Cannot open the file again, lets modify f_mode
 439                          * of original and continue
 440                          */
 441                         pr_info_ratelimited("Unable to reopen file for reading.\n");
 442                         f = file;
 443                         f->f_mode |= FMODE_READ;
 444                         modified_mode = true;
 445                 } else {
 446                         new_file_instance = true;
 447                 }
 448         }
 449
 450         i_size = i_size_read(file_inode(f));
 451
 452         if (ima_ahash_minsize && i_size >= ima_ahash_minsize) {
 453                 rc = ima_calc_file_ahash(f, hash);
 454                 if (!rc)
 455                         goto out;
 456         }
 457
 458         rc = ima_calc_file_shash(f, hash);
 459 out:
 460         if (new_file_instance)
 461                 fput(f);
 462         else if (modified_mode)
 463                 f->f_mode &= ~FMODE_READ;
 464         return rc;
 465 }
 466
 467 /*
 468  * Calculate the hash of template data
 469  */
 470 static int ima_calc_field_array_hash_tfm(struct ima_field_data *field_data,
 471                                          struct ima_template_desc *td,
 472                                          int num_fields,
 473                                          struct ima_digest_data *hash,
 474                                          struct crypto_shash *tfm)
 475 {
 476         SHASH_DESC_ON_STACK(shash, tfm);
 477         int rc, i;
 478
 479         shash->tfm = tfm;
 480         shash->flags = 0;
 481
 482         hash->length = crypto_shash_digestsize(tfm);
 483
 484         rc = crypto_shash_init(shash);
 485         if (rc != 0)
 486                 return rc;
 487
 488         for (i = 0; i < num_fields; i++) {
 489                 u8 buffer[IMA_EVENT_NAME_LEN_MAX + 1] = { 0 };
 490                 u8 *data_to_hash = field_data[i].data;
 491                 u32 datalen = field_data[i].len;
 492                 u32 datalen_to_hash =
 493                     !ima_canonical_fmt ? datalen : cpu_to_le32(datalen);
 494
 495                 if (strcmp(td->name, IMA_TEMPLATE_IMA_NAME) != 0) {
 496                         rc = crypto_shash_update(shash,
 497                                                 (const u8 *) &datalen_to_hash,
 498                                                 sizeof(datalen_to_hash));
 499                         if (rc)
 500                                 break;
 501                 } else if (strcmp(td->fields[i]->field_id, "n") == 0) {
 502                         memcpy(buffer, data_to_hash, datalen);
 503                         data_to_hash = buffer;
 504                         datalen = IMA_EVENT_NAME_LEN_MAX + 1;
 505                 }
 506                 rc = crypto_shash_update(shash, data_to_hash, datalen);
 507                 if (rc)
 508                         break;
 509         }
 510
 511         if (!rc)
 512                 rc = crypto_shash_final(shash, hash->digest);
 513
 514         return rc;
 515 }
 516
 517 int ima_calc_field_array_hash(struct ima_field_data *field_data,
 518                               struct ima_template_desc *desc, int num_fields,
 519                               struct ima_digest_data *hash)
 520 {
 521         struct crypto_shash *tfm;
 522         int rc;
 523
 524         tfm = ima_alloc_tfm(hash->algo);
 525         if (IS_ERR(tfm))
 526                 return PTR_ERR(tfm);
 527
 528         rc = ima_calc_field_array_hash_tfm(field_data, desc, num_fields,
 529                                            hash, tfm);
 530
 531         ima_free_tfm(tfm);
 532
 533         return rc;
 534 }
 535
 536 static int calc_buffer_ahash_atfm(const void *buf, loff_t len,
 537                                   struct ima_digest_data *hash,
 538                                   struct crypto_ahash *tfm)
 539 {
 540         struct ahash_request *req;
 541         struct scatterlist sg;
 542         struct crypto_wait wait;
 543         int rc, ahash_rc = 0;
 544
 545         hash->length = crypto_ahash_digestsize(tfm);
 546
 547         req = ahash_request_alloc(tfm, GFP_KERNEL);
 548         if (!req)
 549                 return -ENOMEM;
 550
 551         crypto_init_wait(&wait);
 552         ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
 553                                    CRYPTO_TFM_REQ_MAY_SLEEP,
 554                                    crypto_req_done, &wait);
 555
 556         rc = ahash_wait(crypto_ahash_init(req), &wait);
 557         if (rc)
 558                 goto out;
 559
 560         sg_init_one(&sg, buf, len);
 561         ahash_request_set_crypt(req, &sg, NULL, len);
 562
 563         ahash_rc = crypto_ahash_update(req);
 564
 565         /* wait for the update request to complete */
 566         rc = ahash_wait(ahash_rc, &wait);
 567         if (!rc) {
 568                 ahash_request_set_crypt(req, NULL, hash->digest, 0);
 569                 rc = ahash_wait(crypto_ahash_final(req), &wait);
 570         }
 571 out:
 572         ahash_request_free(req);
 573         return rc;
 574 }
 575
 576 static int calc_buffer_ahash(const void *buf, loff_t len,
 577                              struct ima_digest_data *hash)
 578 {
 579         struct crypto_ahash *tfm;
 580         int rc;
 581
 582         tfm = ima_alloc_atfm(hash->algo);
 583         if (IS_ERR(tfm))
 584                 return PTR_ERR(tfm);
 585
 586         rc = calc_buffer_ahash_atfm(buf, len, hash, tfm);
 587
 588         ima_free_atfm(tfm);
 589
 590         return rc;
 591 }
 592
 593 static int calc_buffer_shash_tfm(const void *buf, loff_t size,
 594                                 struct ima_digest_data *hash,
 595                                 struct crypto_shash *tfm)
 596 {
 597         SHASH_DESC_ON_STACK(shash, tfm);
 598         unsigned int len;
 599         int rc;
 600
 601         shash->tfm = tfm;
 602         shash->flags = 0;
 603
 604         hash->length = crypto_shash_digestsize(tfm);
 605
 606         rc = crypto_shash_init(shash);
 607         if (rc != 0)
 608                 return rc;
 609
 610         while (size) {
 611                 len = size < PAGE_SIZE ? size : PAGE_SIZE;
 612                 rc = crypto_shash_update(shash, buf, len);
 613                 if (rc)
 614                         break;
 615                 buf += len;
 616                 size -= len;
 617         }
 618
 619         if (!rc)
 620                 rc = crypto_shash_final(shash, hash->digest);
 621         return rc;
 622 }
 623
 624 static int calc_buffer_shash(const void *buf, loff_t len,
 625                              struct ima_digest_data *hash)
 626 {
 627         struct crypto_shash *tfm;
 628         int rc;
 629
 630         tfm = ima_alloc_tfm(hash->algo);
 631         if (IS_ERR(tfm))
 632                 return PTR_ERR(tfm);
 633
 634         rc = calc_buffer_shash_tfm(buf, len, hash, tfm);
 635
 636         ima_free_tfm(tfm);
 637         return rc;
 638 }
 639
 640 int ima_calc_buffer_hash(const void *buf, loff_t len,
 641                          struct ima_digest_data *hash)
 642 {
 643         int rc;
 644
 645         if (ima_ahash_minsize && len >= ima_ahash_minsize) {
 646                 rc = calc_buffer_ahash(buf, len, hash);
 647                 if (!rc)
 648                         return 0;
 649         }
 650
 651         return calc_buffer_shash(buf, len, hash);
 652 }
 653
 654 static void __init ima_pcrread(int idx, u8 *pcr)
 655 {
 656         if (!ima_tpm_chip)
 657                 return;
 658
 659         if (tpm_pcr_read(ima_tpm_chip, idx, pcr) != 0)
 660                 pr_err("Error Communicating to TPM chip\n");
 661 }
 662
 663 /*
 664  * Calculate the boot aggregate hash
 665  */
 666 static int ima_calc_boot_aggregate_tfm(char *digest,
 667                                        struct crypto_shash *tfm)
 668 {
 669         u8 pcr_i[TPM_DIGEST_SIZE];
 670         int rc, i;
 671         SHASH_DESC_ON_STACK(shash, tfm);
 672
 673         shash->tfm = tfm;
 674         shash->flags = 0;
 675
 676         rc = crypto_shash_init(shash);
 677         if (rc != 0)
 678                 return rc;
 679
 680         /* cumulative sha1 over tpm registers 0-7 */
 681         for (i = TPM_PCR0; i < TPM_PCR8; i++) {
 682                 ima_pcrread(i, pcr_i);
 683                 /* now accumulate with current aggregate */
 684                 rc = crypto_shash_update(shash, pcr_i, TPM_DIGEST_SIZE);
 685         }
 686         if (!rc)
 687                 crypto_shash_final(shash, digest);
 688         return rc;
 689 }
 690
 691 int ima_calc_boot_aggregate(struct ima_digest_data *hash)
 692 {
 693         struct crypto_shash *tfm;
 694         int rc;
 695
 696         tfm = ima_alloc_tfm(hash->algo);
 697         if (IS_ERR(tfm))
 698                 return PTR_ERR(tfm);
 699
 700         hash->length = crypto_shash_digestsize(tfm);
 701         rc = ima_calc_boot_aggregate_tfm(hash->digest, tfm);
 702
 703         ima_free_tfm(tfm);
 704
 705         return rc;
 706 }