security/integrity/ima/ima_appraise.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2011 IBM Corporation
   4  *
   5  * Author:
   6  * Mimi Zohar <[email protected]>
   7  */
   8 #include <linux/module.h>
   9 #include <linux/init.h>
  10 #include <linux/file.h>
  11 #include <linux/fs.h>
  12 #include <linux/xattr.h>
  13 #include <linux/magic.h>
  14 #include <linux/ima.h>
  15 #include <linux/evm.h>
  16 #include <linux/fsverity.h>
  17 #include <keys/system_keyring.h>
  18 #include <uapi/linux/fsverity.h>
  19
  20 #include "ima.h"
  21
  22 #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
  23 static char *ima_appraise_cmdline_default __initdata;
  24 core_param(ima_appraise, ima_appraise_cmdline_default, charp, 0);
  25
  26 void __init ima_appraise_parse_cmdline(void)
  27 {
  28         const char *str = ima_appraise_cmdline_default;
  29         bool sb_state = arch_ima_get_secureboot();
  30         int appraisal_state = ima_appraise;
  31
  32         if (!str)
  33                 return;
  34
  35         if (strncmp(str, "off", 3) == 0)
  36                 appraisal_state = 0;
  37         else if (strncmp(str, "log", 3) == 0)
  38                 appraisal_state = IMA_APPRAISE_LOG;
  39         else if (strncmp(str, "fix", 3) == 0)
  40                 appraisal_state = IMA_APPRAISE_FIX;
  41         else if (strncmp(str, "enforce", 7) == 0)
  42                 appraisal_state = IMA_APPRAISE_ENFORCE;
  43         else
  44                 pr_err("invalid \"%s\" appraise option", str);
  45
  46         /* If appraisal state was changed, but secure boot is enabled,
  47          * keep its default */
  48         if (sb_state) {
  49                 if (!(appraisal_state & IMA_APPRAISE_ENFORCE))
  50                         pr_info("Secure boot enabled: ignoring ima_appraise=%s option",
  51                                 str);
  52         } else {
  53                 ima_appraise = appraisal_state;
  54         }
  55 }
  56 #endif
  57
  58 /*
  59  * is_ima_appraise_enabled - return appraise status
  60  *
  61  * Only return enabled, if not in ima_appraise="fix" or "log" modes.
  62  */
  63 bool is_ima_appraise_enabled(void)
  64 {
  65         return ima_appraise & IMA_APPRAISE_ENFORCE;
  66 }
  67
  68 /*
  69  * ima_must_appraise - set appraise flag
  70  *
  71  * Return 1 to appraise or hash
  72  */
  73 int ima_must_appraise(struct mnt_idmap *idmap, struct inode *inode,
  74                       int mask, enum ima_hooks func)
  75 {
  76         u32 secid;
  77
  78         if (!ima_appraise)
  79                 return 0;
  80
  81         security_current_getsecid_subj(&secid);
  82         return ima_match_policy(idmap, inode, current_cred(), secid,
  83                                 func, mask, IMA_APPRAISE | IMA_HASH, NULL,
  84                                 NULL, NULL, NULL);
  85 }
  86
  87 static int ima_fix_xattr(struct dentry *dentry,
  88                          struct integrity_iint_cache *iint)
  89 {
  90         int rc, offset;
  91         u8 algo = iint->ima_hash->algo;
  92
  93         if (algo <= HASH_ALGO_SHA1) {
  94                 offset = 1;
  95                 iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST;
  96         } else {
  97                 offset = 0;
  98                 iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG;
  99                 iint->ima_hash->xattr.ng.algo = algo;
 100         }
 101         rc = __vfs_setxattr_noperm(&nop_mnt_idmap, dentry, XATTR_NAME_IMA,
 102                                    &iint->ima_hash->xattr.data[offset],
 103                                    (sizeof(iint->ima_hash->xattr) - offset) +
 104                                    iint->ima_hash->length, 0);
 105         return rc;
 106 }
 107
 108 /* Return specific func appraised cached result */
 109 enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
 110                                            enum ima_hooks func)
 111 {
 112         switch (func) {
 113         case MMAP_CHECK:
 114         case MMAP_CHECK_REQPROT:
 115                 return iint->ima_mmap_status;
 116         case BPRM_CHECK:
 117                 return iint->ima_bprm_status;
 118         case CREDS_CHECK:
 119                 return iint->ima_creds_status;
 120         case FILE_CHECK:
 121         case POST_SETATTR:
 122                 return iint->ima_file_status;
 123         case MODULE_CHECK ... MAX_CHECK - 1:
 124         default:
 125                 return iint->ima_read_status;
 126         }
 127 }
 128
 129 static void ima_set_cache_status(struct integrity_iint_cache *iint,
 130                                  enum ima_hooks func,
 131                                  enum integrity_status status)
 132 {
 133         switch (func) {
 134         case MMAP_CHECK:
 135         case MMAP_CHECK_REQPROT:
 136                 iint->ima_mmap_status = status;
 137                 break;
 138         case BPRM_CHECK:
 139                 iint->ima_bprm_status = status;
 140                 break;
 141         case CREDS_CHECK:
 142                 iint->ima_creds_status = status;
 143                 break;
 144         case FILE_CHECK:
 145         case POST_SETATTR:
 146                 iint->ima_file_status = status;
 147                 break;
 148         case MODULE_CHECK ... MAX_CHECK - 1:
 149         default:
 150                 iint->ima_read_status = status;
 151                 break;
 152         }
 153 }
 154
 155 static void ima_cache_flags(struct integrity_iint_cache *iint,
 156                              enum ima_hooks func)
 157 {
 158         switch (func) {
 159         case MMAP_CHECK:
 160         case MMAP_CHECK_REQPROT:
 161                 iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
 162                 break;
 163         case BPRM_CHECK:
 164                 iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
 165                 break;
 166         case CREDS_CHECK:
 167                 iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED);
 168                 break;
 169         case FILE_CHECK:
 170         case POST_SETATTR:
 171                 iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
 172                 break;
 173         case MODULE_CHECK ... MAX_CHECK - 1:
 174         default:
 175                 iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED);
 176                 break;
 177         }
 178 }
 179
 180 enum hash_algo ima_get_hash_algo(const struct evm_ima_xattr_data *xattr_value,
 181                                  int xattr_len)
 182 {
 183         struct signature_v2_hdr *sig;
 184         enum hash_algo ret;
 185
 186         if (!xattr_value || xattr_len < 2)
 187                 /* return default hash algo */
 188                 return ima_hash_algo;
 189
 190         switch (xattr_value->type) {
 191         case IMA_VERITY_DIGSIG:
 192                 sig = (typeof(sig))xattr_value;
 193                 if (sig->version != 3 || xattr_len <= sizeof(*sig) ||
 194                     sig->hash_algo >= HASH_ALGO__LAST)
 195                         return ima_hash_algo;
 196                 return sig->hash_algo;
 197         case EVM_IMA_XATTR_DIGSIG:
 198                 sig = (typeof(sig))xattr_value;
 199                 if (sig->version != 2 || xattr_len <= sizeof(*sig)
 200                     || sig->hash_algo >= HASH_ALGO__LAST)
 201                         return ima_hash_algo;
 202                 return sig->hash_algo;
 203         case IMA_XATTR_DIGEST_NG:
 204                 /* first byte contains algorithm id */
 205                 ret = xattr_value->data[0];
 206                 if (ret < HASH_ALGO__LAST)
 207                         return ret;
 208                 break;
 209         case IMA_XATTR_DIGEST:
 210                 /* this is for backward compatibility */
 211                 if (xattr_len == 21) {
 212                         unsigned int zero = 0;
 213                         if (!memcmp(&xattr_value->data[16], &zero, 4))
 214                                 return HASH_ALGO_MD5;
 215                         else
 216                                 return HASH_ALGO_SHA1;
 217                 } else if (xattr_len == 17)
 218                         return HASH_ALGO_MD5;
 219                 break;
 220         }
 221
 222         /* return default hash algo */
 223         return ima_hash_algo;
 224 }
 225
 226 int ima_read_xattr(struct dentry *dentry,
 227                    struct evm_ima_xattr_data **xattr_value, int xattr_len)
 228 {
 229         int ret;
 230
 231         ret = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, XATTR_NAME_IMA,
 232                                  (char **)xattr_value, xattr_len, GFP_NOFS);
 233         if (ret == -EOPNOTSUPP)
 234                 ret = 0;
 235         return ret;
 236 }
 237
 238 /*
 239  * calc_file_id_hash - calculate the hash of the ima_file_id struct data
 240  * @type: xattr type [enum evm_ima_xattr_type]
 241  * @algo: hash algorithm [enum hash_algo]
 242  * @digest: pointer to the digest to be hashed
 243  * @hash: (out) pointer to the hash
 244  *
 245  * IMA signature version 3 disambiguates the data that is signed by
 246  * indirectly signing the hash of the ima_file_id structure data.
 247  *
 248  * Signing the ima_file_id struct is currently only supported for
 249  * IMA_VERITY_DIGSIG type xattrs.
 250  *
 251  * Return 0 on success, error code otherwise.
 252  */
 253 static int calc_file_id_hash(enum evm_ima_xattr_type type,
 254                              enum hash_algo algo, const u8 *digest,
 255                              struct ima_digest_data *hash)
 256 {
 257         struct ima_file_id file_id = {
 258                 .hash_type = IMA_VERITY_DIGSIG, .hash_algorithm = algo};
 259         unsigned int unused = HASH_MAX_DIGESTSIZE - hash_digest_size[algo];
 260
 261         if (type != IMA_VERITY_DIGSIG)
 262                 return -EINVAL;
 263
 264         memcpy(file_id.hash, digest, hash_digest_size[algo]);
 265
 266         hash->algo = algo;
 267         hash->length = hash_digest_size[algo];
 268
 269         return ima_calc_buffer_hash(&file_id, sizeof(file_id) - unused, hash);
 270 }
 271
 272 /*
 273  * xattr_verify - verify xattr digest or signature
 274  *
 275  * Verify whether the hash or signature matches the file contents.
 276  *
 277  * Return 0 on success, error code otherwise.
 278  */
 279 static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
 280                         struct evm_ima_xattr_data *xattr_value, int xattr_len,
 281                         enum integrity_status *status, const char **cause)
 282 {
 283         struct ima_max_digest_data hash;
 284         struct signature_v2_hdr *sig;
 285         int rc = -EINVAL, hash_start = 0;
 286         int mask;
 287
 288         switch (xattr_value->type) {
 289         case IMA_XATTR_DIGEST_NG:
 290                 /* first byte contains algorithm id */
 291                 hash_start = 1;
 292                 fallthrough;
 293         case IMA_XATTR_DIGEST:
 294                 if (*status != INTEGRITY_PASS_IMMUTABLE) {
 295                         if (iint->flags & IMA_DIGSIG_REQUIRED) {
 296                                 if (iint->flags & IMA_VERITY_REQUIRED)
 297                                         *cause = "verity-signature-required";
 298                                 else
 299                                         *cause = "IMA-signature-required";
 300                                 *status = INTEGRITY_FAIL;
 301                                 break;
 302                         }
 303                         clear_bit(IMA_DIGSIG, &iint->atomic_flags);
 304                 } else {
 305                         set_bit(IMA_DIGSIG, &iint->atomic_flags);
 306                 }
 307                 if (xattr_len - sizeof(xattr_value->type) - hash_start >=
 308                                 iint->ima_hash->length)
 309                         /*
 310                          * xattr length may be longer. md5 hash in previous
 311                          * version occupied 20 bytes in xattr, instead of 16
 312                          */
 313                         rc = memcmp(&xattr_value->data[hash_start],
 314                                     iint->ima_hash->digest,
 315                                     iint->ima_hash->length);
 316                 else
 317                         rc = -EINVAL;
 318                 if (rc) {
 319                         *cause = "invalid-hash";
 320                         *status = INTEGRITY_FAIL;
 321                         break;
 322                 }
 323                 *status = INTEGRITY_PASS;
 324                 break;
 325         case EVM_IMA_XATTR_DIGSIG:
 326                 set_bit(IMA_DIGSIG, &iint->atomic_flags);
 327
 328                 mask = IMA_DIGSIG_REQUIRED | IMA_VERITY_REQUIRED;
 329                 if ((iint->flags & mask) == mask) {
 330                         *cause = "verity-signature-required";
 331                         *status = INTEGRITY_FAIL;
 332                         break;
 333                 }
 334
 335                 sig = (typeof(sig))xattr_value;
 336                 if (sig->version >= 3) {
 337                         *cause = "invalid-signature-version";
 338                         *status = INTEGRITY_FAIL;
 339                         break;
 340                 }
 341                 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
 342                                              (const char *)xattr_value,
 343                                              xattr_len,
 344                                              iint->ima_hash->digest,
 345                                              iint->ima_hash->length);
 346                 if (rc == -EOPNOTSUPP) {
 347                         *status = INTEGRITY_UNKNOWN;
 348                         break;
 349                 }
 350                 if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
 351                     func == KEXEC_KERNEL_CHECK)
 352                         rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
 353                                                      (const char *)xattr_value,
 354                                                      xattr_len,
 355                                                      iint->ima_hash->digest,
 356                                                      iint->ima_hash->length);
 357                 if (rc) {
 358                         *cause = "invalid-signature";
 359                         *status = INTEGRITY_FAIL;
 360                 } else {
 361                         *status = INTEGRITY_PASS;
 362                 }
 363                 break;
 364         case IMA_VERITY_DIGSIG:
 365                 set_bit(IMA_DIGSIG, &iint->atomic_flags);
 366
 367                 if (iint->flags & IMA_DIGSIG_REQUIRED) {
 368                         if (!(iint->flags & IMA_VERITY_REQUIRED)) {
 369                                 *cause = "IMA-signature-required";
 370                                 *status = INTEGRITY_FAIL;
 371                                 break;
 372                         }
 373                 }
 374
 375                 sig = (typeof(sig))xattr_value;
 376                 if (sig->version != 3) {
 377                         *cause = "invalid-signature-version";
 378                         *status = INTEGRITY_FAIL;
 379                         break;
 380                 }
 381
 382                 rc = calc_file_id_hash(IMA_VERITY_DIGSIG, iint->ima_hash->algo,
 383                                        iint->ima_hash->digest, &hash.hdr);
 384                 if (rc) {
 385                         *cause = "sigv3-hashing-error";
 386                         *status = INTEGRITY_FAIL;
 387                         break;
 388                 }
 389
 390                 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
 391                                              (const char *)xattr_value,
 392                                              xattr_len, hash.digest,
 393                                              hash.hdr.length);
 394                 if (rc) {
 395                         *cause = "invalid-verity-signature";
 396                         *status = INTEGRITY_FAIL;
 397                 } else {
 398                         *status = INTEGRITY_PASS;
 399                 }
 400
 401                 break;
 402         default:
 403                 *status = INTEGRITY_UNKNOWN;
 404                 *cause = "unknown-ima-data";
 405                 break;
 406         }
 407
 408         return rc;
 409 }
 410
 411 /*
 412  * modsig_verify - verify modsig signature
 413  *
 414  * Verify whether the signature matches the file contents.
 415  *
 416  * Return 0 on success, error code otherwise.
 417  */
 418 static int modsig_verify(enum ima_hooks func, const struct modsig *modsig,
 419                          enum integrity_status *status, const char **cause)
 420 {
 421         int rc;
 422
 423         rc = integrity_modsig_verify(INTEGRITY_KEYRING_IMA, modsig);
 424         if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
 425             func == KEXEC_KERNEL_CHECK)
 426                 rc = integrity_modsig_verify(INTEGRITY_KEYRING_PLATFORM,
 427                                              modsig);
 428         if (rc) {
 429                 *cause = "invalid-signature";
 430                 *status = INTEGRITY_FAIL;
 431         } else {
 432                 *status = INTEGRITY_PASS;
 433         }
 434
 435         return rc;
 436 }
 437
 438 /*
 439  * ima_check_blacklist - determine if the binary is blacklisted.
 440  *
 441  * Add the hash of the blacklisted binary to the measurement list, based
 442  * on policy.
 443  *
 444  * Returns -EPERM if the hash is blacklisted.
 445  */
 446 int ima_check_blacklist(struct integrity_iint_cache *iint,
 447                         const struct modsig *modsig, int pcr)
 448 {
 449         enum hash_algo hash_algo;
 450         const u8 *digest = NULL;
 451         u32 digestsize = 0;
 452         int rc = 0;
 453
 454         if (!(iint->flags & IMA_CHECK_BLACKLIST))
 455                 return 0;
 456
 457         if (iint->flags & IMA_MODSIG_ALLOWED && modsig) {
 458                 ima_get_modsig_digest(modsig, &hash_algo, &digest, &digestsize);
 459
 460                 rc = is_binary_blacklisted(digest, digestsize);
 461                 if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
 462                         process_buffer_measurement(&nop_mnt_idmap, NULL, digest, digestsize,
 463                                                    "blacklisted-hash", NONE,
 464                                                    pcr, NULL, false, NULL, 0);
 465         }
 466
 467         return rc;
 468 }
 469
 470 /*
 471  * ima_appraise_measurement - appraise file measurement
 472  *
 473  * Call evm_verifyxattr() to verify the integrity of 'security.ima'.
 474  * Assuming success, compare the xattr hash with the collected measurement.
 475  *
 476  * Return 0 on success, error code otherwise
 477  */
 478 int ima_appraise_measurement(enum ima_hooks func,
 479                              struct integrity_iint_cache *iint,
 480                              struct file *file, const unsigned char *filename,
 481                              struct evm_ima_xattr_data *xattr_value,
 482                              int xattr_len, const struct modsig *modsig)
 483 {
 484         static const char op[] = "appraise_data";
 485         const char *cause = "unknown";
 486         struct dentry *dentry = file_dentry(file);
 487         struct inode *inode = d_backing_inode(dentry);
 488         enum integrity_status status = INTEGRITY_UNKNOWN;
 489         int rc = xattr_len;
 490         bool try_modsig = iint->flags & IMA_MODSIG_ALLOWED && modsig;
 491
 492         /* If not appraising a modsig, we need an xattr. */
 493         if (!(inode->i_opflags & IOP_XATTR) && !try_modsig)
 494                 return INTEGRITY_UNKNOWN;
 495
 496         /* If reading the xattr failed and there's no modsig, error out. */
 497         if (rc <= 0 && !try_modsig) {
 498                 if (rc && rc != -ENODATA)
 499                         goto out;
 500
 501                 if (iint->flags & IMA_DIGSIG_REQUIRED) {
 502                         if (iint->flags & IMA_VERITY_REQUIRED)
 503                                 cause = "verity-signature-required";
 504                         else
 505                                 cause = "IMA-signature-required";
 506                 } else {
 507                         cause = "missing-hash";
 508                 }
 509
 510                 status = INTEGRITY_NOLABEL;
 511                 if (file->f_mode & FMODE_CREATED)
 512                         iint->flags |= IMA_NEW_FILE;
 513                 if ((iint->flags & IMA_NEW_FILE) &&
 514                     (!(iint->flags & IMA_DIGSIG_REQUIRED) ||
 515                      (inode->i_size == 0)))
 516                         status = INTEGRITY_PASS;
 517                 goto out;
 518         }
 519
 520         status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value,
 521                                  rc < 0 ? 0 : rc, iint);
 522         switch (status) {
 523         case INTEGRITY_PASS:
 524         case INTEGRITY_PASS_IMMUTABLE:
 525         case INTEGRITY_UNKNOWN:
 526                 break;
 527         case INTEGRITY_NOXATTRS:        /* No EVM protected xattrs. */
 528                 /* It's fine not to have xattrs when using a modsig. */
 529                 if (try_modsig)
 530                         break;
 531                 fallthrough;
 532         case INTEGRITY_NOLABEL:         /* No security.evm xattr. */
 533                 cause = "missing-HMAC";
 534                 goto out;
 535         case INTEGRITY_FAIL_IMMUTABLE:
 536                 set_bit(IMA_DIGSIG, &iint->atomic_flags);
 537                 cause = "invalid-fail-immutable";
 538                 goto out;
 539         case INTEGRITY_FAIL:            /* Invalid HMAC/signature. */
 540                 cause = "invalid-HMAC";
 541                 goto out;
 542         default:
 543                 WARN_ONCE(true, "Unexpected integrity status %d\n", status);
 544         }
 545
 546         if (xattr_value)
 547                 rc = xattr_verify(func, iint, xattr_value, xattr_len, &status,
 548                                   &cause);
 549
 550         /*
 551          * If we have a modsig and either no imasig or the imasig's key isn't
 552          * known, then try verifying the modsig.
 553          */
 554         if (try_modsig &&
 555             (!xattr_value || xattr_value->type == IMA_XATTR_DIGEST_NG ||
 556              rc == -ENOKEY))
 557                 rc = modsig_verify(func, modsig, &status, &cause);
 558
 559 out:
 560         /*
 561          * File signatures on some filesystems can not be properly verified.
 562          * When such filesystems are mounted by an untrusted mounter or on a
 563          * system not willing to accept such a risk, fail the file signature
 564          * verification.
 565          */
 566         if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
 567             ((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) ||
 568              (iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) {
 569                 status = INTEGRITY_FAIL;
 570                 cause = "unverifiable-signature";
 571                 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
 572                                     op, cause, rc, 0);
 573         } else if (status != INTEGRITY_PASS) {
 574                 /* Fix mode, but don't replace file signatures. */
 575                 if ((ima_appraise & IMA_APPRAISE_FIX) && !try_modsig &&
 576                     (!xattr_value ||
 577                      xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
 578                         if (!ima_fix_xattr(dentry, iint))
 579                                 status = INTEGRITY_PASS;
 580                 }
 581
 582                 /*
 583                  * Permit new files with file/EVM portable signatures, but
 584                  * without data.
 585                  */
 586                 if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE &&
 587                     test_bit(IMA_DIGSIG, &iint->atomic_flags)) {
 588                         status = INTEGRITY_PASS;
 589                 }
 590
 591                 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
 592                                     op, cause, rc, 0);
 593         } else {
 594                 ima_cache_flags(iint, func);
 595         }
 596
 597         ima_set_cache_status(iint, func, status);
 598         return status;
 599 }
 600
 601 /*
 602  * ima_update_xattr - update 'security.ima' hash value
 603  */
 604 void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
 605 {
 606         struct dentry *dentry = file_dentry(file);
 607         int rc = 0;
 608
 609         /* do not collect and update hash for digital signatures */
 610         if (test_bit(IMA_DIGSIG, &iint->atomic_flags))
 611                 return;
 612
 613         if ((iint->ima_file_status != INTEGRITY_PASS) &&
 614             !(iint->flags & IMA_HASH))
 615                 return;
 616
 617         rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo, NULL);
 618         if (rc < 0)
 619                 return;
 620
 621         inode_lock(file_inode(file));
 622         ima_fix_xattr(dentry, iint);
 623         inode_unlock(file_inode(file));
 624 }
 625
 626 /**
 627  * ima_inode_post_setattr - reflect file metadata changes
 628  * @idmap:  idmap of the mount the inode was found from
 629  * @dentry: pointer to the affected dentry
 630  *
 631  * Changes to a dentry's metadata might result in needing to appraise.
 632  *
 633  * This function is called from notify_change(), which expects the caller
 634  * to lock the inode's i_mutex.
 635  */
 636 void ima_inode_post_setattr(struct mnt_idmap *idmap,
 637                             struct dentry *dentry)
 638 {
 639         struct inode *inode = d_backing_inode(dentry);
 640         struct integrity_iint_cache *iint;
 641         int action;
 642
 643         if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)
 644             || !(inode->i_opflags & IOP_XATTR))
 645                 return;
 646
 647         action = ima_must_appraise(idmap, inode, MAY_ACCESS, POST_SETATTR);
 648         iint = integrity_iint_find(inode);
 649         if (iint) {
 650                 set_bit(IMA_CHANGE_ATTR, &iint->atomic_flags);
 651                 if (!action)
 652                         clear_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
 653         }
 654 }
 655
 656 /*
 657  * ima_protect_xattr - protect 'security.ima'
 658  *
 659  * Ensure that not just anyone can modify or remove 'security.ima'.
 660  */
 661 static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name,
 662                              const void *xattr_value, size_t xattr_value_len)
 663 {
 664         if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
 665                 if (!capable(CAP_SYS_ADMIN))
 666                         return -EPERM;
 667                 return 1;
 668         }
 669         return 0;
 670 }
 671
 672 static void ima_reset_appraise_flags(struct inode *inode, int digsig)
 673 {
 674         struct integrity_iint_cache *iint;
 675
 676         if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode))
 677                 return;
 678
 679         iint = integrity_iint_find(inode);
 680         if (!iint)
 681                 return;
 682         iint->measured_pcrs = 0;
 683         set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags);
 684         if (digsig)
 685                 set_bit(IMA_DIGSIG, &iint->atomic_flags);
 686         else
 687                 clear_bit(IMA_DIGSIG, &iint->atomic_flags);
 688 }
 689
 690 /**
 691  * validate_hash_algo() - Block setxattr with unsupported hash algorithms
 692  * @dentry: object of the setxattr()
 693  * @xattr_value: userland supplied xattr value
 694  * @xattr_value_len: length of xattr_value
 695  *
 696  * The xattr value is mapped to its hash algorithm, and this algorithm
 697  * must be built in the kernel for the setxattr to be allowed.
 698  *
 699  * Emit an audit message when the algorithm is invalid.
 700  *
 701  * Return: 0 on success, else an error.
 702  */
 703 static int validate_hash_algo(struct dentry *dentry,
 704                               const struct evm_ima_xattr_data *xattr_value,
 705                               size_t xattr_value_len)
 706 {
 707         char *path = NULL, *pathbuf = NULL;
 708         enum hash_algo xattr_hash_algo;
 709         const char *errmsg = "unavailable-hash-algorithm";
 710         unsigned int allowed_hashes;
 711
 712         xattr_hash_algo = ima_get_hash_algo(xattr_value, xattr_value_len);
 713
 714         allowed_hashes = atomic_read(&ima_setxattr_allowed_hash_algorithms);
 715
 716         if (allowed_hashes) {
 717                 /* success if the algorithm is allowed in the ima policy */
 718                 if (allowed_hashes & (1U << xattr_hash_algo))
 719                         return 0;
 720
 721                 /*
 722                  * We use a different audit message when the hash algorithm
 723                  * is denied by a policy rule, instead of not being built
 724                  * in the kernel image
 725                  */
 726                 errmsg = "denied-hash-algorithm";
 727         } else {
 728                 if (likely(xattr_hash_algo == ima_hash_algo))
 729                         return 0;
 730
 731                 /* allow any xattr using an algorithm built in the kernel */
 732                 if (crypto_has_alg(hash_algo_name[xattr_hash_algo], 0, 0))
 733                         return 0;
 734         }
 735
 736         pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
 737         if (!pathbuf)
 738                 return -EACCES;
 739
 740         path = dentry_path(dentry, pathbuf, PATH_MAX);
 741
 742         integrity_audit_msg(AUDIT_INTEGRITY_DATA, d_inode(dentry), path,
 743                             "set_data", errmsg, -EACCES, 0);
 744
 745         kfree(pathbuf);
 746
 747         return -EACCES;
 748 }
 749
 750 int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
 751                        const void *xattr_value, size_t xattr_value_len)
 752 {
 753         const struct evm_ima_xattr_data *xvalue = xattr_value;
 754         int digsig = 0;
 755         int result;
 756         int err;
 757
 758         result = ima_protect_xattr(dentry, xattr_name, xattr_value,
 759                                    xattr_value_len);
 760         if (result == 1) {
 761                 if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
 762                         return -EINVAL;
 763
 764                 err = validate_hash_algo(dentry, xvalue, xattr_value_len);
 765                 if (err)
 766                         return err;
 767
 768                 digsig = (xvalue->type == EVM_IMA_XATTR_DIGSIG);
 769         } else if (!strcmp(xattr_name, XATTR_NAME_EVM) && xattr_value_len > 0) {
 770                 digsig = (xvalue->type == EVM_XATTR_PORTABLE_DIGSIG);
 771         }
 772         if (result == 1 || evm_revalidate_status(xattr_name)) {
 773                 ima_reset_appraise_flags(d_backing_inode(dentry), digsig);
 774                 if (result == 1)
 775                         result = 0;
 776         }
 777         return result;
 778 }
 779
 780 int ima_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
 781                       const char *acl_name, struct posix_acl *kacl)
 782 {
 783         if (evm_revalidate_status(acl_name))
 784                 ima_reset_appraise_flags(d_backing_inode(dentry), 0);
 785
 786         return 0;
 787 }
 788
 789 int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
 790 {
 791         int result;
 792
 793         result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
 794         if (result == 1 || evm_revalidate_status(xattr_name)) {
 795                 ima_reset_appraise_flags(d_backing_inode(dentry), 0);
 796                 if (result == 1)
 797                         result = 0;
 798         }
 799         return result;
 800 }