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 #include <crypto/hash_info.h>
  28 #include "ima.h"
  29
  30 struct ahash_completion {
  31         struct completion completion;
  32         int err;
  33 };
  34
  35 /* minimum file size for ahash use */
  36 static unsigned long ima_ahash_minsize;
  37 module_param_named(ahash_minsize, ima_ahash_minsize, ulong, 0644);
  38 MODULE_PARM_DESC(ahash_minsize, "Minimum file size for ahash use");
  39
  40 /* default is 0 - 1 page. */
  41 static int ima_maxorder;
  42 static unsigned int ima_bufsize = PAGE_SIZE;
  43
  44 static int param_set_bufsize(const char *val, const struct kernel_param *kp)
  45 {
  46         unsigned long long size;
  47         int order;
  48
  49         size = memparse(val, NULL);
  50         order = get_order(size);
  51         if (order >= MAX_ORDER)
  52                 return -EINVAL;
  53         ima_maxorder = order;
  54         ima_bufsize = PAGE_SIZE << order;
  55         return 0;
  56 }
  57
  58 static struct kernel_param_ops param_ops_bufsize = {
  59         .set = param_set_bufsize,
  60         .get = param_get_uint,
  61 };
  62 #define param_check_bufsize(name, p) __param_check(name, p, unsigned int)
  63
  64 module_param_named(ahash_bufsize, ima_bufsize, bufsize, 0644);
  65 MODULE_PARM_DESC(ahash_bufsize, "Maximum ahash buffer size");
  66
  67 static struct crypto_shash *ima_shash_tfm;
  68 static struct crypto_ahash *ima_ahash_tfm;
  69
  70 /**
  71  * ima_kernel_read - read file content
  72  *
  73  * This is a function for reading file content instead of kernel_read().
  74  * It does not perform locking checks to ensure it cannot be blocked.
  75  * It does not perform security checks because it is irrelevant for IMA.
  76  *
  77  */
  78 static int ima_kernel_read(struct file *file, loff_t offset,
  79                            char *addr, unsigned long count)
  80 {
  81         mm_segment_t old_fs;
  82         char __user *buf = addr;
  83         ssize_t ret;
  84
  85         if (!(file->f_mode & FMODE_READ))
  86                 return -EBADF;
  87         if (!file->f_op->read && !file->f_op->aio_read)
  88                 return -EINVAL;
  89
  90         old_fs = get_fs();
  91         set_fs(get_ds());
  92         if (file->f_op->read)
  93                 ret = file->f_op->read(file, buf, count, &offset);
  94         else
  95                 ret = do_sync_read(file, buf, count, &offset);
  96         set_fs(old_fs);
  97         return ret;
  98 }
  99
 100 int ima_init_crypto(void)
 101 {
 102         long rc;
 103
 104         ima_shash_tfm = crypto_alloc_shash(hash_algo_name[ima_hash_algo], 0, 0);
 105         if (IS_ERR(ima_shash_tfm)) {
 106                 rc = PTR_ERR(ima_shash_tfm);
 107                 pr_err("Can not allocate %s (reason: %ld)\n",
 108                        hash_algo_name[ima_hash_algo], rc);
 109                 return rc;
 110         }
 111         return 0;
 112 }
 113
 114 static struct crypto_shash *ima_alloc_tfm(enum hash_algo algo)
 115 {
 116         struct crypto_shash *tfm = ima_shash_tfm;
 117         int rc;
 118
 119         if (algo != ima_hash_algo && algo < HASH_ALGO__LAST) {
 120                 tfm = crypto_alloc_shash(hash_algo_name[algo], 0, 0);
 121                 if (IS_ERR(tfm)) {
 122                         rc = PTR_ERR(tfm);
 123                         pr_err("Can not allocate %s (reason: %d)\n",
 124                                hash_algo_name[algo], rc);
 125                 }
 126         }
 127         return tfm;
 128 }
 129
 130 static void ima_free_tfm(struct crypto_shash *tfm)
 131 {
 132         if (tfm != ima_shash_tfm)
 133                 crypto_free_shash(tfm);
 134 }
 135
 136 /**
 137  * ima_alloc_pages() - Allocate contiguous pages.
 138  * @max_size:       Maximum amount of memory to allocate.
 139  * @allocated_size: Returned size of actual allocation.
 140  * @last_warn:      Should the min_size allocation warn or not.
 141  *
 142  * Tries to do opportunistic allocation for memory first trying to allocate
 143  * max_size amount of memory and then splitting that until zero order is
 144  * reached. Allocation is tried without generating allocation warnings unless
 145  * last_warn is set. Last_warn set affects only last allocation of zero order.
 146  *
 147  * By default, ima_maxorder is 0 and it is equivalent to kmalloc(GFP_KERNEL)
 148  *
 149  * Return pointer to allocated memory, or NULL on failure.
 150  */
 151 static void *ima_alloc_pages(loff_t max_size, size_t *allocated_size,
 152                              int last_warn)
 153 {
 154         void *ptr;
 155         int order = ima_maxorder;
 156         gfp_t gfp_mask = __GFP_WAIT | __GFP_NOWARN | __GFP_NORETRY;
 157
 158         if (order)
 159                 order = min(get_order(max_size), order);
 160
 161         for (; order; order--) {
 162                 ptr = (void *)__get_free_pages(gfp_mask, order);
 163                 if (ptr) {
 164                         *allocated_size = PAGE_SIZE << order;
 165                         return ptr;
 166                 }
 167         }
 168
 169         /* order is zero - one page */
 170
 171         gfp_mask = GFP_KERNEL;
 172
 173         if (!last_warn)
 174                 gfp_mask |= __GFP_NOWARN;
 175
 176         ptr = (void *)__get_free_pages(gfp_mask, 0);
 177         if (ptr) {
 178                 *allocated_size = PAGE_SIZE;
 179                 return ptr;
 180         }
 181
 182         *allocated_size = 0;
 183         return NULL;
 184 }
 185
 186 /**
 187  * ima_free_pages() - Free pages allocated by ima_alloc_pages().
 188  * @ptr:  Pointer to allocated pages.
 189  * @size: Size of allocated buffer.
 190  */
 191 static void ima_free_pages(void *ptr, size_t size)
 192 {
 193         if (!ptr)
 194                 return;
 195         free_pages((unsigned long)ptr, get_order(size));
 196 }
 197
 198 static struct crypto_ahash *ima_alloc_atfm(enum hash_algo algo)
 199 {
 200         struct crypto_ahash *tfm = ima_ahash_tfm;
 201         int rc;
 202
 203         if ((algo != ima_hash_algo && algo < HASH_ALGO__LAST) || !tfm) {
 204                 tfm = crypto_alloc_ahash(hash_algo_name[algo], 0, 0);
 205                 if (!IS_ERR(tfm)) {
 206                         if (algo == ima_hash_algo)
 207                                 ima_ahash_tfm = tfm;
 208                 } else {
 209                         rc = PTR_ERR(tfm);
 210                         pr_err("Can not allocate %s (reason: %d)\n",
 211                                hash_algo_name[algo], rc);
 212                 }
 213         }
 214         return tfm;
 215 }
 216
 217 static void ima_free_atfm(struct crypto_ahash *tfm)
 218 {
 219         if (tfm != ima_ahash_tfm)
 220                 crypto_free_ahash(tfm);
 221 }
 222
 223 static void ahash_complete(struct crypto_async_request *req, int err)
 224 {
 225         struct ahash_completion *res = req->data;
 226
 227         if (err == -EINPROGRESS)
 228                 return;
 229         res->err = err;
 230         complete(&res->completion);
 231 }
 232
 233 static int ahash_wait(int err, struct ahash_completion *res)
 234 {
 235         switch (err) {
 236         case 0:
 237                 break;
 238         case -EINPROGRESS:
 239         case -EBUSY:
 240                 wait_for_completion(&res->completion);
 241                 reinit_completion(&res->completion);
 242                 err = res->err;
 243                 /* fall through */
 244         default:
 245                 pr_crit_ratelimited("ahash calculation failed: err: %d\n", err);
 246         }
 247
 248         return err;
 249 }
 250
 251 static int ima_calc_file_hash_atfm(struct file *file,
 252                                    struct ima_digest_data *hash,
 253                                    struct crypto_ahash *tfm)
 254 {
 255         loff_t i_size, offset;
 256         char *rbuf[2] = { NULL, };
 257         int rc, read = 0, rbuf_len, active = 0, ahash_rc = 0;
 258         struct ahash_request *req;
 259         struct scatterlist sg[1];
 260         struct ahash_completion res;
 261         size_t rbuf_size[2];
 262
 263         hash->length = crypto_ahash_digestsize(tfm);
 264
 265         req = ahash_request_alloc(tfm, GFP_KERNEL);
 266         if (!req)
 267                 return -ENOMEM;
 268
 269         init_completion(&res.completion);
 270         ahash_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
 271                                    CRYPTO_TFM_REQ_MAY_SLEEP,
 272                                    ahash_complete, &res);
 273
 274         rc = ahash_wait(crypto_ahash_init(req), &res);
 275         if (rc)
 276                 goto out1;
 277
 278         i_size = i_size_read(file_inode(file));
 279
 280         if (i_size == 0)
 281                 goto out2;
 282
 283         /*
 284          * Try to allocate maximum size of memory.
 285          * Fail if even a single page cannot be allocated.
 286          */
 287         rbuf[0] = ima_alloc_pages(i_size, &rbuf_size[0], 1);
 288         if (!rbuf[0]) {
 289                 rc = -ENOMEM;
 290                 goto out1;
 291         }
 292
 293         /* Only allocate one buffer if that is enough. */
 294         if (i_size > rbuf_size[0]) {
 295                 /*
 296                  * Try to allocate secondary buffer. If that fails fallback to
 297                  * using single buffering. Use previous memory allocation size
 298                  * as baseline for possible allocation size.
 299                  */
 300                 rbuf[1] = ima_alloc_pages(i_size - rbuf_size[0],
 301                                           &rbuf_size[1], 0);
 302         }
 303
 304         if (!(file->f_mode & FMODE_READ)) {
 305                 file->f_mode |= FMODE_READ;
 306                 read = 1;
 307         }
 308
 309         for (offset = 0; offset < i_size; offset += rbuf_len) {
 310                 if (!rbuf[1] && offset) {
 311                         /* Not using two buffers, and it is not the first
 312                          * read/request, wait for the completion of the
 313                          * previous ahash_update() request.
 314                          */
 315                         rc = ahash_wait(ahash_rc, &res);
 316                         if (rc)
 317                                 goto out3;
 318                 }
 319                 /* read buffer */
 320                 rbuf_len = min_t(loff_t, i_size - offset, rbuf_size[active]);
 321                 rc = ima_kernel_read(file, offset, rbuf[active], rbuf_len);
 322                 if (rc != rbuf_len)
 323                         goto out3;
 324
 325                 if (rbuf[1] && offset) {
 326                         /* Using two buffers, and it is not the first
 327                          * read/request, wait for the completion of the
 328                          * previous ahash_update() request.
 329                          */
 330                         rc = ahash_wait(ahash_rc, &res);
 331                         if (rc)
 332                                 goto out3;
 333                 }
 334
 335                 sg_init_one(&sg[0], rbuf[active], rbuf_len);
 336                 ahash_request_set_crypt(req, sg, NULL, rbuf_len);
 337
 338                 ahash_rc = crypto_ahash_update(req);
 339
 340                 if (rbuf[1])
 341                         active = !active; /* swap buffers, if we use two */
 342         }
 343         /* wait for the last update request to complete */
 344         rc = ahash_wait(ahash_rc, &res);
 345 out3:
 346         if (read)
 347                 file->f_mode &= ~FMODE_READ;
 348         ima_free_pages(rbuf[0], rbuf_size[0]);
 349         ima_free_pages(rbuf[1], rbuf_size[1]);
 350 out2:
 351         if (!rc) {
 352                 ahash_request_set_crypt(req, NULL, hash->digest, 0);
 353                 rc = ahash_wait(crypto_ahash_final(req), &res);
 354         }
 355 out1:
 356         ahash_request_free(req);
 357         return rc;
 358 }
 359
 360 static int ima_calc_file_ahash(struct file *file, struct ima_digest_data *hash)
 361 {
 362         struct crypto_ahash *tfm;
 363         int rc;
 364
 365         tfm = ima_alloc_atfm(hash->algo);
 366         if (IS_ERR(tfm))
 367                 return PTR_ERR(tfm);
 368
 369         rc = ima_calc_file_hash_atfm(file, hash, tfm);
 370
 371         ima_free_atfm(tfm);
 372
 373         return rc;
 374 }
 375
 376 static int ima_calc_file_hash_tfm(struct file *file,
 377                                   struct ima_digest_data *hash,
 378                                   struct crypto_shash *tfm)
 379 {
 380         loff_t i_size, offset = 0;
 381         char *rbuf;
 382         int rc, read = 0;
 383         struct {
 384                 struct shash_desc shash;
 385                 char ctx[crypto_shash_descsize(tfm)];
 386         } desc;
 387
 388         desc.shash.tfm = tfm;
 389         desc.shash.flags = 0;
 390
 391         hash->length = crypto_shash_digestsize(tfm);
 392
 393         rc = crypto_shash_init(&desc.shash);
 394         if (rc != 0)
 395                 return rc;
 396
 397         i_size = i_size_read(file_inode(file));
 398
 399         if (i_size == 0)
 400                 goto out;
 401
 402         rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
 403         if (!rbuf)
 404                 return -ENOMEM;
 405
 406         if (!(file->f_mode & FMODE_READ)) {
 407                 file->f_mode |= FMODE_READ;
 408                 read = 1;
 409         }
 410
 411         while (offset < i_size) {
 412                 int rbuf_len;
 413
 414                 rbuf_len = ima_kernel_read(file, offset, rbuf, PAGE_SIZE);
 415                 if (rbuf_len < 0) {
 416                         rc = rbuf_len;
 417                         break;
 418                 }
 419                 if (rbuf_len == 0)
 420                         break;
 421                 offset += rbuf_len;
 422
 423                 rc = crypto_shash_update(&desc.shash, rbuf, rbuf_len);
 424                 if (rc)
 425                         break;
 426         }
 427         if (read)
 428                 file->f_mode &= ~FMODE_READ;
 429         kfree(rbuf);
 430 out:
 431         if (!rc)
 432                 rc = crypto_shash_final(&desc.shash, hash->digest);
 433         return rc;
 434 }
 435
 436 static int ima_calc_file_shash(struct file *file, struct ima_digest_data *hash)
 437 {
 438         struct crypto_shash *tfm;
 439         int rc;
 440
 441         tfm = ima_alloc_tfm(hash->algo);
 442         if (IS_ERR(tfm))
 443                 return PTR_ERR(tfm);
 444
 445         rc = ima_calc_file_hash_tfm(file, hash, tfm);
 446
 447         ima_free_tfm(tfm);
 448
 449         return rc;
 450 }
 451
 452 /*
 453  * ima_calc_file_hash - calculate file hash
 454  *
 455  * Asynchronous hash (ahash) allows using HW acceleration for calculating
 456  * a hash. ahash performance varies for different data sizes on different
 457  * crypto accelerators. shash performance might be better for smaller files.
 458  * The 'ima.ahash_minsize' module parameter allows specifying the best
 459  * minimum file size for using ahash on the system.
 460  *
 461  * If the ima.ahash_minsize parameter is not specified, this function uses
 462  * shash for the hash calculation.  If ahash fails, it falls back to using
 463  * shash.
 464  */
 465 int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash)
 466 {
 467         loff_t i_size;
 468         int rc;
 469
 470         i_size = i_size_read(file_inode(file));
 471
 472         if (ima_ahash_minsize && i_size >= ima_ahash_minsize) {
 473                 rc = ima_calc_file_ahash(file, hash);
 474                 if (!rc)
 475                         return 0;
 476         }
 477
 478         return ima_calc_file_shash(file, hash);
 479 }
 480
 481 /*
 482  * Calculate the hash of template data
 483  */
 484 static int ima_calc_field_array_hash_tfm(struct ima_field_data *field_data,
 485                                          struct ima_template_desc *td,
 486                                          int num_fields,
 487                                          struct ima_digest_data *hash,
 488                                          struct crypto_shash *tfm)
 489 {
 490         struct {
 491                 struct shash_desc shash;
 492                 char ctx[crypto_shash_descsize(tfm)];
 493         } desc;
 494         int rc, i;
 495
 496         desc.shash.tfm = tfm;
 497         desc.shash.flags = 0;
 498
 499         hash->length = crypto_shash_digestsize(tfm);
 500
 501         rc = crypto_shash_init(&desc.shash);
 502         if (rc != 0)
 503                 return rc;
 504
 505         for (i = 0; i < num_fields; i++) {
 506                 u8 buffer[IMA_EVENT_NAME_LEN_MAX + 1] = { 0 };
 507                 u8 *data_to_hash = field_data[i].data;
 508                 u32 datalen = field_data[i].len;
 509
 510                 if (strcmp(td->name, IMA_TEMPLATE_IMA_NAME) != 0) {
 511                         rc = crypto_shash_update(&desc.shash,
 512                                                 (const u8 *) &field_data[i].len,
 513                                                 sizeof(field_data[i].len));
 514                         if (rc)
 515                                 break;
 516                 } else if (strcmp(td->fields[i]->field_id, "n") == 0) {
 517                         memcpy(buffer, data_to_hash, datalen);
 518                         data_to_hash = buffer;
 519                         datalen = IMA_EVENT_NAME_LEN_MAX + 1;
 520                 }
 521                 rc = crypto_shash_update(&desc.shash, data_to_hash, datalen);
 522                 if (rc)
 523                         break;
 524         }
 525
 526         if (!rc)
 527                 rc = crypto_shash_final(&desc.shash, hash->digest);
 528
 529         return rc;
 530 }
 531
 532 int ima_calc_field_array_hash(struct ima_field_data *field_data,
 533                               struct ima_template_desc *desc, int num_fields,
 534                               struct ima_digest_data *hash)
 535 {
 536         struct crypto_shash *tfm;
 537         int rc;
 538
 539         tfm = ima_alloc_tfm(hash->algo);
 540         if (IS_ERR(tfm))
 541                 return PTR_ERR(tfm);
 542
 543         rc = ima_calc_field_array_hash_tfm(field_data, desc, num_fields,
 544                                            hash, tfm);
 545
 546         ima_free_tfm(tfm);
 547
 548         return rc;
 549 }
 550
 551 static void __init ima_pcrread(int idx, u8 *pcr)
 552 {
 553         if (!ima_used_chip)
 554                 return;
 555
 556         if (tpm_pcr_read(TPM_ANY_NUM, idx, pcr) != 0)
 557                 pr_err("Error Communicating to TPM chip\n");
 558 }
 559
 560 /*
 561  * Calculate the boot aggregate hash
 562  */
 563 static int __init ima_calc_boot_aggregate_tfm(char *digest,
 564                                               struct crypto_shash *tfm)
 565 {
 566         u8 pcr_i[TPM_DIGEST_SIZE];
 567         int rc, i;
 568         struct {
 569                 struct shash_desc shash;
 570                 char ctx[crypto_shash_descsize(tfm)];
 571         } desc;
 572
 573         desc.shash.tfm = tfm;
 574         desc.shash.flags = 0;
 575
 576         rc = crypto_shash_init(&desc.shash);
 577         if (rc != 0)
 578                 return rc;
 579
 580         /* cumulative sha1 over tpm registers 0-7 */
 581         for (i = TPM_PCR0; i < TPM_PCR8; i++) {
 582                 ima_pcrread(i, pcr_i);
 583                 /* now accumulate with current aggregate */
 584                 rc = crypto_shash_update(&desc.shash, pcr_i, TPM_DIGEST_SIZE);
 585         }
 586         if (!rc)
 587                 crypto_shash_final(&desc.shash, digest);
 588         return rc;
 589 }
 590
 591 int __init ima_calc_boot_aggregate(struct ima_digest_data *hash)
 592 {
 593         struct crypto_shash *tfm;
 594         int rc;
 595
 596         tfm = ima_alloc_tfm(hash->algo);
 597         if (IS_ERR(tfm))
 598                 return PTR_ERR(tfm);
 599
 600         hash->length = crypto_shash_digestsize(tfm);
 601         rc = ima_calc_boot_aggregate_tfm(hash->digest, tfm);
 602
 603         ima_free_tfm(tfm);
 604
 605         return rc;
 606 }