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 <zohar@us.ibm.com>
   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, struct ima_iint_cache *iint)
  88 {
  89         int rc, offset;
  90         u8 algo = iint->ima_hash->algo;
  91
  92         if (algo <= HASH_ALGO_SHA1) {
  93                 offset = 1;
  94                 iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST;
  95         } else {
  96                 offset = 0;
  97                 iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG;
  98                 iint->ima_hash->xattr.ng.algo = algo;
  99         }
 100         rc = __vfs_setxattr_noperm(&nop_mnt_idmap, dentry, XATTR_NAME_IMA,
 101                                    &iint->ima_hash->xattr.data[offset],
 102                                    (sizeof(iint->ima_hash->xattr) - offset) +
 103                                    iint->ima_hash->length, 0);
 104         return rc;
 105 }
 106
 107 /* Return specific func appraised cached result */
 108 enum integrity_status ima_get_cache_status(struct ima_iint_cache *iint,
 109                                            enum ima_hooks func)
 110 {
 111         switch (func) {
 112         case MMAP_CHECK:
 113         case MMAP_CHECK_REQPROT:
 114                 return iint->ima_mmap_status;
 115         case BPRM_CHECK:
 116                 return iint->ima_bprm_status;
 117         case CREDS_CHECK:
 118                 return iint->ima_creds_status;
 119         case FILE_CHECK:
 120         case POST_SETATTR:
 121                 return iint->ima_file_status;
 122         case MODULE_CHECK ... MAX_CHECK - 1:
 123         default:
 124                 return iint->ima_read_status;
 125         }
 126 }
 127
 128 static void ima_set_cache_status(struct ima_iint_cache *iint,
 129                                  enum ima_hooks func,
 130                                  enum integrity_status status)
 131 {
 132         switch (func) {
 133         case MMAP_CHECK:
 134         case MMAP_CHECK_REQPROT:
 135                 iint->ima_mmap_status = status;
 136                 break;
 137         case BPRM_CHECK:
 138                 iint->ima_bprm_status = status;
 139                 break;
 140         case CREDS_CHECK:
 141                 iint->ima_creds_status = status;
 142                 break;
 143         case FILE_CHECK:
 144         case POST_SETATTR:
 145                 iint->ima_file_status = status;
 146                 break;
 147         case MODULE_CHECK ... MAX_CHECK - 1:
 148         default:
 149                 iint->ima_read_status = status;
 150                 break;
 151         }
 152 }
 153
 154 static void ima_cache_flags(struct ima_iint_cache *iint, enum ima_hooks func)
 155 {
 156         switch (func) {
 157         case MMAP_CHECK:
 158         case MMAP_CHECK_REQPROT:
 159                 iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
 160                 break;
 161         case BPRM_CHECK:
 162                 iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
 163                 break;
 164         case CREDS_CHECK:
 165                 iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED);
 166                 break;
 167         case FILE_CHECK:
 168         case POST_SETATTR:
 169                 iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
 170                 break;
 171         case MODULE_CHECK ... MAX_CHECK - 1:
 172         default:
 173                 iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED);
 174                 break;
 175         }
 176 }
 177
 178 enum hash_algo ima_get_hash_algo(const struct evm_ima_xattr_data *xattr_value,
 179                                  int xattr_len)
 180 {
 181         struct signature_v2_hdr *sig;
 182         enum hash_algo ret;
 183
 184         if (!xattr_value || xattr_len < 2)
 185                 /* return default hash algo */
 186                 return ima_hash_algo;
 187
 188         switch (xattr_value->type) {
 189         case IMA_VERITY_DIGSIG:
 190                 sig = (typeof(sig))xattr_value;
 191                 if (sig->version != 3 || xattr_len <= sizeof(*sig) ||
 192                     sig->hash_algo >= HASH_ALGO__LAST)
 193                         return ima_hash_algo;
 194                 return sig->hash_algo;
 195         case EVM_IMA_XATTR_DIGSIG:
 196                 sig = (typeof(sig))xattr_value;
 197                 if (sig->version != 2 || xattr_len <= sizeof(*sig)
 198                     || sig->hash_algo >= HASH_ALGO__LAST)
 199                         return ima_hash_algo;
 200                 return sig->hash_algo;
 201         case IMA_XATTR_DIGEST_NG:
 202                 /* first byte contains algorithm id */
 203                 ret = xattr_value->data[0];
 204                 if (ret < HASH_ALGO__LAST)
 205                         return ret;
 206                 break;
 207         case IMA_XATTR_DIGEST:
 208                 /* this is for backward compatibility */
 209                 if (xattr_len == 21) {
 210                         unsigned int zero = 0;
 211                         if (!memcmp(&xattr_value->data[16], &zero, 4))
 212                                 return HASH_ALGO_MD5;
 213                         else
 214                                 return HASH_ALGO_SHA1;
 215                 } else if (xattr_len == 17)
 216                         return HASH_ALGO_MD5;
 217                 break;
 218         }
 219
 220         /* return default hash algo */
 221         return ima_hash_algo;
 222 }
 223
 224 int ima_read_xattr(struct dentry *dentry,
 225                    struct evm_ima_xattr_data **xattr_value, int xattr_len)
 226 {
 227         int ret;
 228
 229         ret = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, XATTR_NAME_IMA,
 230                                  (char **)xattr_value, xattr_len, GFP_NOFS);
 231         if (ret == -EOPNOTSUPP)
 232                 ret = 0;
 233         return ret;
 234 }
 235
 236 /*
 237  * calc_file_id_hash - calculate the hash of the ima_file_id struct data
 238  * @type: xattr type [enum evm_ima_xattr_type]
 239  * @algo: hash algorithm [enum hash_algo]
 240  * @digest: pointer to the digest to be hashed
 241  * @hash: (out) pointer to the hash
 242  *
 243  * IMA signature version 3 disambiguates the data that is signed by
 244  * indirectly signing the hash of the ima_file_id structure data.
 245  *
 246  * Signing the ima_file_id struct is currently only supported for
 247  * IMA_VERITY_DIGSIG type xattrs.
 248  *
 249  * Return 0 on success, error code otherwise.
 250  */
 251 static int calc_file_id_hash(enum evm_ima_xattr_type type,
 252                              enum hash_algo algo, const u8 *digest,
 253                              struct ima_digest_data *hash)
 254 {
 255         struct ima_file_id file_id = {
 256                 .hash_type = IMA_VERITY_DIGSIG, .hash_algorithm = algo};
 257         unsigned int unused = HASH_MAX_DIGESTSIZE - hash_digest_size[algo];
 258
 259         if (type != IMA_VERITY_DIGSIG)
 260                 return -EINVAL;
 261
 262         memcpy(file_id.hash, digest, hash_digest_size[algo]);
 263
 264         hash->algo = algo;
 265         hash->length = hash_digest_size[algo];
 266
 267         return ima_calc_buffer_hash(&file_id, sizeof(file_id) - unused, hash);
 268 }
 269
 270 /*
 271  * xattr_verify - verify xattr digest or signature
 272  *
 273  * Verify whether the hash or signature matches the file contents.
 274  *
 275  * Return 0 on success, error code otherwise.
 276  */
 277 static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
 278                         struct evm_ima_xattr_data *xattr_value, int xattr_len,
 279                         enum integrity_status *status, const char **cause)
 280 {
 281         struct ima_max_digest_data hash;
 282         struct signature_v2_hdr *sig;
 283         int rc = -EINVAL, hash_start = 0;
 284         int mask;
 285
 286         switch (xattr_value->type) {
 287         case IMA_XATTR_DIGEST_NG:
 288                 /* first byte contains algorithm id */
 289                 hash_start = 1;
 290                 fallthrough;
 291         case IMA_XATTR_DIGEST:
 292                 if (*status != INTEGRITY_PASS_IMMUTABLE) {
 293                         if (iint->flags & IMA_DIGSIG_REQUIRED) {
 294                                 if (iint->flags & IMA_VERITY_REQUIRED)
 295                                         *cause = "verity-signature-required";
 296                                 else
 297                                         *cause = "IMA-signature-required";
 298                                 *status = INTEGRITY_FAIL;
 299                                 break;
 300                         }
 301                         clear_bit(IMA_DIGSIG, &iint->atomic_flags);
 302                 } else {
 303                         set_bit(IMA_DIGSIG, &iint->atomic_flags);
 304                 }
 305                 if (xattr_len - sizeof(xattr_value->type) - hash_start >=
 306                                 iint->ima_hash->length)
 307                         /*
 308                          * xattr length may be longer. md5 hash in previous
 309                          * version occupied 20 bytes in xattr, instead of 16
 310                          */
 311                         rc = memcmp(&xattr_value->data[hash_start],
 312                                     iint->ima_hash->digest,
 313                                     iint->ima_hash->length);
 314                 else
 315                         rc = -EINVAL;
 316                 if (rc) {
 317                         *cause = "invalid-hash";
 318                         *status = INTEGRITY_FAIL;
 319                         break;
 320                 }
 321                 *status = INTEGRITY_PASS;
 322                 break;
 323         case EVM_IMA_XATTR_DIGSIG:
 324                 set_bit(IMA_DIGSIG, &iint->atomic_flags);
 325
 326                 mask = IMA_DIGSIG_REQUIRED | IMA_VERITY_REQUIRED;
 327                 if ((iint->flags & mask) == mask) {
 328                         *cause = "verity-signature-required";
 329                         *status = INTEGRITY_FAIL;
 330                         break;
 331                 }
 332
 333                 sig = (typeof(sig))xattr_value;
 334                 if (sig->version >= 3) {
 335                         *cause = "invalid-signature-version";
 336                         *status = INTEGRITY_FAIL;
 337                         break;
 338                 }
 339                 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
 340                                              (const char *)xattr_value,
 341                                              xattr_len,
 342                                              iint->ima_hash->digest,
 343                                              iint->ima_hash->length);
 344                 if (rc == -EOPNOTSUPP) {
 345                         *status = INTEGRITY_UNKNOWN;
 346                         break;
 347                 }
 348                 if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
 349                     func == KEXEC_KERNEL_CHECK)
 350                         rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
 351                                                      (const char *)xattr_value,
 352                                                      xattr_len,
 353                                                      iint->ima_hash->digest,
 354                                                      iint->ima_hash->length);
 355                 if (rc) {
 356                         *cause = "invalid-signature";
 357                         *status = INTEGRITY_FAIL;
 358                 } else {
 359                         *status = INTEGRITY_PASS;
 360                 }
 361                 break;
 362         case IMA_VERITY_DIGSIG:
 363                 set_bit(IMA_DIGSIG, &iint->atomic_flags);
 364
 365                 if (iint->flags & IMA_DIGSIG_REQUIRED) {
 366                         if (!(iint->flags & IMA_VERITY_REQUIRED)) {
 367                                 *cause = "IMA-signature-required";
 368                                 *status = INTEGRITY_FAIL;
 369                                 break;
 370                         }
 371                 }
 372
 373                 sig = (typeof(sig))xattr_value;
 374                 if (sig->version != 3) {
 375                         *cause = "invalid-signature-version";
 376                         *status = INTEGRITY_FAIL;
 377                         break;
 378                 }
 379
 380                 rc = calc_file_id_hash(IMA_VERITY_DIGSIG, iint->ima_hash->algo,
 381                                        iint->ima_hash->digest, &hash.hdr);
 382                 if (rc) {
 383                         *cause = "sigv3-hashing-error";
 384                         *status = INTEGRITY_FAIL;
 385                         break;
 386                 }
 387
 388                 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
 389                                              (const char *)xattr_value,
 390                                              xattr_len, hash.digest,
 391                                              hash.hdr.length);
 392                 if (rc) {
 393                         *cause = "invalid-verity-signature";
 394                         *status = INTEGRITY_FAIL;
 395                 } else {
 396                         *status = INTEGRITY_PASS;
 397                 }
 398
 399                 break;
 400         default:
 401                 *status = INTEGRITY_UNKNOWN;
 402                 *cause = "unknown-ima-data";
 403                 break;
 404         }
 405
 406         return rc;
 407 }
 408
 409 /*
 410  * modsig_verify - verify modsig signature
 411  *
 412  * Verify whether the signature matches the file contents.
 413  *
 414  * Return 0 on success, error code otherwise.
 415  */
 416 static int modsig_verify(enum ima_hooks func, const struct modsig *modsig,
 417                          enum integrity_status *status, const char **cause)
 418 {
 419         int rc;
 420
 421         rc = integrity_modsig_verify(INTEGRITY_KEYRING_IMA, modsig);
 422         if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
 423             func == KEXEC_KERNEL_CHECK)
 424                 rc = integrity_modsig_verify(INTEGRITY_KEYRING_PLATFORM,
 425                                              modsig);
 426         if (rc) {
 427                 *cause = "invalid-signature";
 428                 *status = INTEGRITY_FAIL;
 429         } else {
 430                 *status = INTEGRITY_PASS;
 431         }
 432
 433         return rc;
 434 }
 435
 436 /*
 437  * ima_check_blacklist - determine if the binary is blacklisted.
 438  *
 439  * Add the hash of the blacklisted binary to the measurement list, based
 440  * on policy.
 441  *
 442  * Returns -EPERM if the hash is blacklisted.
 443  */
 444 int ima_check_blacklist(struct ima_iint_cache *iint,
 445                         const struct modsig *modsig, int pcr)
 446 {
 447         enum hash_algo hash_algo;
 448         const u8 *digest = NULL;
 449         u32 digestsize = 0;
 450         int rc = 0;
 451
 452         if (!(iint->flags & IMA_CHECK_BLACKLIST))
 453                 return 0;
 454
 455         if (iint->flags & IMA_MODSIG_ALLOWED && modsig) {
 456                 ima_get_modsig_digest(modsig, &hash_algo, &digest, &digestsize);
 457
 458                 rc = is_binary_blacklisted(digest, digestsize);
 459         } else if (iint->flags & IMA_DIGSIG_REQUIRED && iint->ima_hash)
 460                 rc = is_binary_blacklisted(iint->ima_hash->digest, iint->ima_hash->length);
 461
 462         if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
 463                 process_buffer_measurement(&nop_mnt_idmap, NULL, digest, digestsize,
 464                                            "blacklisted-hash", NONE,
 465                                            pcr, NULL, false, NULL, 0);
 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, struct ima_iint_cache *iint,
 479                              struct file *file, const unsigned char *filename,
 480                              struct evm_ima_xattr_data *xattr_value,
 481                              int xattr_len, const struct modsig *modsig)
 482 {
 483         static const char op[] = "appraise_data";
 484         const char *cause = "unknown";
 485         struct dentry *dentry = file_dentry(file);
 486         struct inode *inode = d_backing_inode(dentry);
 487         enum integrity_status status = INTEGRITY_UNKNOWN;
 488         int rc = xattr_len;
 489         bool try_modsig = iint->flags & IMA_MODSIG_ALLOWED && modsig;
 490
 491         /* If not appraising a modsig, we need an xattr. */
 492         if (!(inode->i_opflags & IOP_XATTR) && !try_modsig)
 493                 return INTEGRITY_UNKNOWN;
 494
 495         /* If reading the xattr failed and there's no modsig, error out. */
 496         if (rc <= 0 && !try_modsig) {
 497                 if (rc && rc != -ENODATA)
 498                         goto out;
 499
 500                 if (iint->flags & IMA_DIGSIG_REQUIRED) {
 501                         if (iint->flags & IMA_VERITY_REQUIRED)
 502                                 cause = "verity-signature-required";
 503                         else
 504                                 cause = "IMA-signature-required";
 505                 } else {
 506                         cause = "missing-hash";
 507                 }
 508
 509                 status = INTEGRITY_NOLABEL;
 510                 if (file->f_mode & FMODE_CREATED)
 511                         iint->flags |= IMA_NEW_FILE;
 512                 if ((iint->flags & IMA_NEW_FILE) &&
 513                     (!(iint->flags & IMA_DIGSIG_REQUIRED) ||
 514                      (inode->i_size == 0)))
 515                         status = INTEGRITY_PASS;
 516                 goto out;
 517         }
 518
 519         status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value,
 520                                  rc < 0 ? 0 : rc);
 521         switch (status) {
 522         case INTEGRITY_PASS:
 523         case INTEGRITY_PASS_IMMUTABLE:
 524         case INTEGRITY_UNKNOWN:
 525                 break;
 526         case INTEGRITY_NOXATTRS:        /* No EVM protected xattrs. */
 527                 /* It's fine not to have xattrs when using a modsig. */
 528                 if (try_modsig)
 529                         break;
 530                 fallthrough;
 531         case INTEGRITY_NOLABEL:         /* No security.evm xattr. */
 532                 cause = "missing-HMAC";
 533                 goto out;
 534         case INTEGRITY_FAIL_IMMUTABLE:
 535                 set_bit(IMA_DIGSIG, &iint->atomic_flags);
 536                 cause = "invalid-fail-immutable";
 537                 goto out;
 538         case INTEGRITY_FAIL:            /* Invalid HMAC/signature. */
 539                 cause = "invalid-HMAC";
 540                 goto out;
 541         default:
 542                 WARN_ONCE(true, "Unexpected integrity status %d\n", status);
 543         }
 544
 545         if (xattr_value)
 546                 rc = xattr_verify(func, iint, xattr_value, xattr_len, &status,
 547                                   &cause);
 548
 549         /*
 550          * If we have a modsig and either no imasig or the imasig's key isn't
 551          * known, then try verifying the modsig.
 552          */
 553         if (try_modsig &&
 554             (!xattr_value || xattr_value->type == IMA_XATTR_DIGEST_NG ||
 555              rc == -ENOKEY))
 556                 rc = modsig_verify(func, modsig, &status, &cause);
 557
 558 out:
 559         /*
 560          * File signatures on some filesystems can not be properly verified.
 561          * When such filesystems are mounted by an untrusted mounter or on a
 562          * system not willing to accept such a risk, fail the file signature
 563          * verification.
 564          */
 565         if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
 566             ((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) ||
 567              (iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) {
 568                 status = INTEGRITY_FAIL;
 569                 cause = "unverifiable-signature";
 570                 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
 571                                     op, cause, rc, 0);
 572         } else if (status != INTEGRITY_PASS) {
 573                 /* Fix mode, but don't replace file signatures. */
 574                 if ((ima_appraise & IMA_APPRAISE_FIX) && !try_modsig &&
 575                     (!xattr_value ||
 576                      xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
 577                         if (!ima_fix_xattr(dentry, iint))
 578                                 status = INTEGRITY_PASS;
 579                 }
 580
 581                 /*
 582                  * Permit new files with file/EVM portable signatures, but
 583                  * without data.
 584                  */
 585                 if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE &&
 586                     test_bit(IMA_DIGSIG, &iint->atomic_flags)) {
 587                         status = INTEGRITY_PASS;
 588                 }
 589
 590                 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
 591                                     op, cause, rc, 0);
 592         } else {
 593                 ima_cache_flags(iint, func);
 594         }
 595
 596         ima_set_cache_status(iint, func, status);
 597         return status;
 598 }
 599
 600 /*
 601  * ima_update_xattr - update 'security.ima' hash value
 602  */
 603 void ima_update_xattr(struct ima_iint_cache *iint, struct file *file)
 604 {
 605         struct dentry *dentry = file_dentry(file);
 606         int rc = 0;
 607
 608         /* do not collect and update hash for digital signatures */
 609         if (test_bit(IMA_DIGSIG, &iint->atomic_flags))
 610                 return;
 611
 612         if ((iint->ima_file_status != INTEGRITY_PASS) &&
 613             !(iint->flags & IMA_HASH))
 614                 return;
 615
 616         rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo, NULL);
 617         if (rc < 0)
 618                 return;
 619
 620         inode_lock(file_inode(file));
 621         ima_fix_xattr(dentry, iint);
 622         inode_unlock(file_inode(file));
 623 }
 624
 625 /**
 626  * ima_inode_post_setattr - reflect file metadata changes
 627  * @idmap:  idmap of the mount the inode was found from
 628  * @dentry: pointer to the affected dentry
 629  * @ia_valid: for the UID and GID status
 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 static void ima_inode_post_setattr(struct mnt_idmap *idmap,
 637                                    struct dentry *dentry, int ia_valid)
 638 {
 639         struct inode *inode = d_backing_inode(dentry);
 640         struct ima_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 = ima_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 ima_iint_cache *iint;
 675
 676         if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode))
 677                 return;
 678
 679         iint = ima_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 static int ima_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
 751                               const char *xattr_name, const void *xattr_value,
 752                               size_t xattr_value_len, int flags)
 753 {
 754         const struct evm_ima_xattr_data *xvalue = xattr_value;
 755         int digsig = 0;
 756         int result;
 757         int err;
 758
 759         result = ima_protect_xattr(dentry, xattr_name, xattr_value,
 760                                    xattr_value_len);
 761         if (result == 1) {
 762                 if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
 763                         return -EINVAL;
 764
 765                 err = validate_hash_algo(dentry, xvalue, xattr_value_len);
 766                 if (err)
 767                         return err;
 768
 769                 digsig = (xvalue->type == EVM_IMA_XATTR_DIGSIG);
 770         } else if (!strcmp(xattr_name, XATTR_NAME_EVM) && xattr_value_len > 0) {
 771                 digsig = (xvalue->type == EVM_XATTR_PORTABLE_DIGSIG);
 772         }
 773         if (result == 1 || evm_revalidate_status(xattr_name)) {
 774                 ima_reset_appraise_flags(d_backing_inode(dentry), digsig);
 775                 if (result == 1)
 776                         result = 0;
 777         }
 778         return result;
 779 }
 780
 781 static int ima_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
 782                              const char *acl_name, struct posix_acl *kacl)
 783 {
 784         if (evm_revalidate_status(acl_name))
 785                 ima_reset_appraise_flags(d_backing_inode(dentry), 0);
 786
 787         return 0;
 788 }
 789
 790 static int ima_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
 791                                  const char *xattr_name)
 792 {
 793         int result;
 794
 795         result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
 796         if (result == 1 || evm_revalidate_status(xattr_name)) {
 797                 ima_reset_appraise_flags(d_backing_inode(dentry), 0);
 798                 if (result == 1)
 799                         result = 0;
 800         }
 801         return result;
 802 }
 803
 804 static int ima_inode_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
 805                                 const char *acl_name)
 806 {
 807         return ima_inode_set_acl(idmap, dentry, acl_name, NULL);
 808 }
 809
 810 static struct security_hook_list ima_appraise_hooks[] __ro_after_init = {
 811         LSM_HOOK_INIT(inode_post_setattr, ima_inode_post_setattr),
 812         LSM_HOOK_INIT(inode_setxattr, ima_inode_setxattr),
 813         LSM_HOOK_INIT(inode_set_acl, ima_inode_set_acl),
 814         LSM_HOOK_INIT(inode_removexattr, ima_inode_removexattr),
 815         LSM_HOOK_INIT(inode_remove_acl, ima_inode_remove_acl),
 816 };
 817
 818 void __init init_ima_appraise_lsm(const struct lsm_id *lsmid)
 819 {
 820         security_add_hooks(ima_appraise_hooks, ARRAY_SIZE(ima_appraise_hooks),
 821                            lsmid);
 822 }