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/binfmts.h> 12 #include <linux/fs.h> 13 #include <linux/xattr.h> 14 #include <linux/magic.h> 15 #include <linux/ima.h> 16 #include <linux/evm.h> 17 #include <linux/fsverity.h> 18 #include <keys/system_keyring.h> 19 #include <uapi/linux/fsverity.h> 20 21 #include "ima.h" 22 23 #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM 24 static char *ima_appraise_cmdline_default __initdata; 25 core_param(ima_appraise, ima_appraise_cmdline_default, charp, 0); 26 27 void __init ima_appraise_parse_cmdline(void) 28 { 29 const char *str = ima_appraise_cmdline_default; 30 bool sb_state = arch_get_secureboot(); 31 int appraisal_state = ima_appraise; 32 33 if (!str) 34 return; 35 36 if (strncmp(str, "off", 3) == 0) 37 appraisal_state = 0; 38 else if (strncmp(str, "log", 3) == 0) 39 appraisal_state = IMA_APPRAISE_LOG; 40 else if (strncmp(str, "fix", 3) == 0) 41 appraisal_state = IMA_APPRAISE_FIX; 42 else if (strncmp(str, "enforce", 7) == 0) 43 appraisal_state = IMA_APPRAISE_ENFORCE; 44 else 45 pr_err("invalid \"%s\" appraise option", str); 46 47 /* If appraisal state was changed, but secure boot is enabled, 48 * keep its default */ 49 if (sb_state) { 50 if (!(appraisal_state & IMA_APPRAISE_ENFORCE)) 51 pr_info("Secure boot enabled: ignoring ima_appraise=%s option", 52 str); 53 } else { 54 ima_appraise = appraisal_state; 55 } 56 } 57 #endif 58 59 /* 60 * is_ima_appraise_enabled - return appraise status 61 * 62 * Only return enabled, if not in ima_appraise="fix" or "log" modes. 63 */ 64 bool is_ima_appraise_enabled(void) 65 { 66 return ima_appraise & IMA_APPRAISE_ENFORCE; 67 } 68 69 /* 70 * ima_must_appraise - set appraise flag 71 * 72 * Return 1 to appraise or hash 73 */ 74 int ima_must_appraise(struct mnt_idmap *idmap, struct inode *inode, 75 int mask, enum ima_hooks func) 76 { 77 struct lsm_prop prop; 78 79 if (!ima_appraise) 80 return 0; 81 82 security_current_getlsmprop_subj(&prop); 83 return ima_match_policy(idmap, inode, current_cred(), &prop, 84 func, mask, IMA_APPRAISE | IMA_HASH, NULL, 85 NULL, NULL, NULL); 86 } 87 88 static int ima_fix_xattr(struct dentry *dentry, struct ima_iint_cache *iint) 89 { 90 int rc, offset; 91 u8 algo = iint->ima_hash->algo; 92 93 if (IS_RDONLY(d_inode(dentry))) 94 return -EROFS; 95 if (IS_IMMUTABLE(d_inode(dentry))) 96 return -EPERM; 97 98 if (algo <= HASH_ALGO_SHA1) { 99 offset = 1; 100 iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST; 101 } else { 102 offset = 0; 103 iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG; 104 iint->ima_hash->xattr.ng.algo = algo; 105 } 106 rc = __vfs_setxattr_noperm(&nop_mnt_idmap, dentry, XATTR_NAME_IMA, 107 &iint->ima_hash->xattr.data[offset], 108 (sizeof(iint->ima_hash->xattr) - offset) + 109 iint->ima_hash->length, 0); 110 return rc; 111 } 112 113 /* Return specific func appraised cached result */ 114 enum integrity_status ima_get_cache_status(struct ima_iint_cache *iint, 115 enum ima_hooks func) 116 { 117 switch (func) { 118 case MMAP_CHECK: 119 case MMAP_CHECK_REQPROT: 120 return iint->ima_mmap_status; 121 case BPRM_CHECK: 122 return iint->ima_bprm_status; 123 case CREDS_CHECK: 124 return iint->ima_creds_status; 125 case FILE_CHECK: 126 case POST_SETATTR: 127 return iint->ima_file_status; 128 case MODULE_CHECK ... MAX_CHECK - 1: 129 default: 130 return iint->ima_read_status; 131 } 132 } 133 134 static void ima_set_cache_status(struct ima_iint_cache *iint, 135 enum ima_hooks func, 136 enum integrity_status status) 137 { 138 switch (func) { 139 case MMAP_CHECK: 140 case MMAP_CHECK_REQPROT: 141 iint->ima_mmap_status = status; 142 break; 143 case BPRM_CHECK: 144 iint->ima_bprm_status = status; 145 break; 146 case CREDS_CHECK: 147 iint->ima_creds_status = status; 148 break; 149 case FILE_CHECK: 150 case POST_SETATTR: 151 iint->ima_file_status = status; 152 break; 153 case MODULE_CHECK ... MAX_CHECK - 1: 154 default: 155 iint->ima_read_status = status; 156 break; 157 } 158 } 159 160 static void ima_cache_flags(struct ima_iint_cache *iint, enum ima_hooks func) 161 { 162 switch (func) { 163 case MMAP_CHECK: 164 case MMAP_CHECK_REQPROT: 165 iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED); 166 break; 167 case BPRM_CHECK: 168 iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED); 169 break; 170 case CREDS_CHECK: 171 iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED); 172 break; 173 case FILE_CHECK: 174 case POST_SETATTR: 175 iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED); 176 break; 177 case MODULE_CHECK ... MAX_CHECK - 1: 178 default: 179 iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED); 180 break; 181 } 182 } 183 184 enum hash_algo ima_get_hash_algo(const struct evm_ima_xattr_data *xattr_value, 185 int xattr_len) 186 { 187 struct signature_v2_hdr *sig; 188 enum hash_algo ret; 189 190 if (!xattr_value || xattr_len < 2) 191 /* return default hash algo */ 192 return ima_hash_algo; 193 194 switch (xattr_value->type) { 195 case IMA_VERITY_DIGSIG: 196 sig = (typeof(sig))xattr_value; 197 if (sig->version != 3 || xattr_len <= sizeof(*sig) || 198 sig->hash_algo >= HASH_ALGO__LAST) 199 return ima_hash_algo; 200 return sig->hash_algo; 201 case EVM_IMA_XATTR_DIGSIG: 202 sig = (typeof(sig))xattr_value; 203 if ((sig->version != 2 && sig->version != 3) || 204 xattr_len <= sizeof(*sig) || 205 sig->hash_algo >= HASH_ALGO__LAST) 206 return ima_hash_algo; 207 return sig->hash_algo; 208 case IMA_XATTR_DIGEST_NG: 209 /* first byte contains algorithm id */ 210 ret = xattr_value->data[0]; 211 if (ret < HASH_ALGO__LAST) 212 return ret; 213 break; 214 case IMA_XATTR_DIGEST: 215 /* this is for backward compatibility */ 216 if (xattr_len == 21) { 217 unsigned int zero = 0; 218 if (!memcmp(&xattr_value->data[16], &zero, 4)) 219 return HASH_ALGO_MD5; 220 else 221 return HASH_ALGO_SHA1; 222 } else if (xattr_len == 17) 223 return HASH_ALGO_MD5; 224 break; 225 } 226 227 /* return default hash algo */ 228 return ima_hash_algo; 229 } 230 231 int ima_read_xattr(struct dentry *dentry, 232 struct evm_ima_xattr_data **xattr_value, int xattr_len) 233 { 234 int ret; 235 236 ret = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, XATTR_NAME_IMA, 237 (char **)xattr_value, xattr_len, GFP_NOFS); 238 if (ret == -EOPNOTSUPP) 239 ret = 0; 240 return ret; 241 } 242 243 /* 244 * xattr_verify - verify xattr digest or signature 245 * 246 * Verify whether the hash or signature matches the file contents. 247 * 248 * Return 0 on success, error code otherwise. 249 */ 250 static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint, 251 struct evm_ima_xattr_data *xattr_value, int xattr_len, 252 enum integrity_status *status, const char **cause) 253 { 254 struct signature_v2_hdr *sig; 255 int rc = -EINVAL, hash_start = 0; 256 int mask; 257 258 switch (xattr_value->type) { 259 case IMA_XATTR_DIGEST_NG: 260 /* first byte contains algorithm id */ 261 hash_start = 1; 262 fallthrough; 263 case IMA_XATTR_DIGEST: 264 if (*status != INTEGRITY_PASS_IMMUTABLE) { 265 if (iint->flags & IMA_DIGSIG_REQUIRED) { 266 if (iint->flags & IMA_VERITY_REQUIRED) 267 *cause = "verity-signature-required"; 268 else 269 *cause = "IMA-signature-required"; 270 *status = INTEGRITY_FAIL; 271 break; 272 } 273 clear_bit(IMA_DIGSIG, &iint->atomic_flags); 274 } else { 275 set_bit(IMA_DIGSIG, &iint->atomic_flags); 276 } 277 /* 278 * Use addition, not subtraction: sizeof() forces unsigned 279 * math and a short xattr_len would wrap around, bypassing 280 * this bounds check. 281 */ 282 if (xattr_len >= (int)sizeof(xattr_value->type) + hash_start + 283 (int)iint->ima_hash->length) 284 /* 285 * xattr length may be longer. md5 hash in previous 286 * version occupied 20 bytes in xattr, instead of 16 287 */ 288 rc = memcmp(&xattr_value->data[hash_start], 289 iint->ima_hash->digest, 290 iint->ima_hash->length); 291 else 292 rc = -EINVAL; 293 if (rc) { 294 *cause = "invalid-hash"; 295 *status = INTEGRITY_FAIL; 296 break; 297 } 298 *status = INTEGRITY_PASS; 299 break; 300 case EVM_IMA_XATTR_DIGSIG: 301 set_bit(IMA_DIGSIG, &iint->atomic_flags); 302 303 mask = IMA_DIGSIG_REQUIRED | IMA_VERITY_REQUIRED; 304 if ((iint->flags & mask) == mask) { 305 *cause = "verity-signature-required"; 306 *status = INTEGRITY_FAIL; 307 break; 308 } 309 310 sig = (typeof(sig))xattr_value; 311 if (sig->version > 3) { 312 *cause = "invalid-signature-version"; 313 *status = INTEGRITY_FAIL; 314 break; 315 } 316 317 if ((iint->flags & IMA_SIGV3_REQUIRED) && sig->version != 3) { 318 *cause = "IMA-sigv3-required"; 319 *status = INTEGRITY_FAIL; 320 break; 321 } 322 323 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA, 324 (const char *)xattr_value, 325 xattr_len, 326 iint->ima_hash->digest, 327 iint->ima_hash->length, 328 iint->ima_hash->algo); 329 if (rc == -EOPNOTSUPP) { 330 *status = INTEGRITY_UNKNOWN; 331 break; 332 } 333 if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc && 334 func == KEXEC_KERNEL_CHECK) 335 rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM, 336 (const char *)xattr_value, 337 xattr_len, 338 iint->ima_hash->digest, 339 iint->ima_hash->length, 340 iint->ima_hash->algo); 341 342 if (rc) { 343 *cause = "invalid-signature"; 344 *status = INTEGRITY_FAIL; 345 } else { 346 *status = INTEGRITY_PASS; 347 } 348 break; 349 case IMA_VERITY_DIGSIG: 350 set_bit(IMA_DIGSIG, &iint->atomic_flags); 351 352 if (iint->flags & IMA_DIGSIG_REQUIRED) { 353 if (!(iint->flags & IMA_VERITY_REQUIRED)) { 354 *cause = "IMA-signature-required"; 355 *status = INTEGRITY_FAIL; 356 break; 357 } 358 } 359 360 sig = (typeof(sig))xattr_value; 361 if (sig->version != 3) { 362 *cause = "invalid-signature-version"; 363 *status = INTEGRITY_FAIL; 364 break; 365 } 366 367 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA, 368 (const char *)xattr_value, 369 xattr_len, 370 iint->ima_hash->digest, 371 iint->ima_hash->length, 372 iint->ima_hash->algo); 373 if (rc == -EOPNOTSUPP) { 374 *status = INTEGRITY_UNKNOWN; 375 break; 376 } else if (rc) { 377 *cause = "invalid-verity-signature"; 378 *status = INTEGRITY_FAIL; 379 } else { 380 *status = INTEGRITY_PASS; 381 } 382 383 break; 384 default: 385 *status = INTEGRITY_UNKNOWN; 386 *cause = "unknown-ima-data"; 387 break; 388 } 389 390 return rc; 391 } 392 393 /* 394 * modsig_verify - verify modsig signature 395 * 396 * Verify whether the signature matches the file contents. 397 * 398 * Return 0 on success, error code otherwise. 399 */ 400 static int modsig_verify(enum ima_hooks func, const struct modsig *modsig, 401 enum integrity_status *status, const char **cause) 402 { 403 int rc; 404 405 rc = integrity_modsig_verify(INTEGRITY_KEYRING_IMA, modsig); 406 if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc && 407 func == KEXEC_KERNEL_CHECK) 408 rc = integrity_modsig_verify(INTEGRITY_KEYRING_PLATFORM, 409 modsig); 410 if (rc) { 411 *cause = "invalid-signature"; 412 *status = INTEGRITY_FAIL; 413 } else { 414 *status = INTEGRITY_PASS; 415 } 416 417 return rc; 418 } 419 420 /* 421 * ima_check_blacklist - determine if the binary is blacklisted. 422 * 423 * Add the hash of the blacklisted binary to the measurement list, based 424 * on policy. 425 * 426 * Returns -EPERM if the hash is blacklisted. 427 */ 428 int ima_check_blacklist(struct ima_iint_cache *iint, 429 const struct modsig *modsig, int pcr) 430 { 431 enum hash_algo hash_algo; 432 const u8 *digest = NULL; 433 u32 digestsize = 0; 434 int rc = 0; 435 436 if (!(iint->flags & IMA_CHECK_BLACKLIST)) 437 return 0; 438 439 if (iint->flags & IMA_MODSIG_ALLOWED && modsig) { 440 ima_get_modsig_digest(modsig, &hash_algo, &digest, &digestsize); 441 442 rc = is_binary_blacklisted(digest, digestsize); 443 } else if (iint->flags & IMA_DIGSIG_REQUIRED && iint->ima_hash) 444 rc = is_binary_blacklisted(iint->ima_hash->digest, iint->ima_hash->length); 445 446 if ((rc == -EPERM) && (iint->flags & IMA_MEASURE)) 447 process_buffer_measurement(&nop_mnt_idmap, NULL, digest, digestsize, 448 "blacklisted-hash", NONE, 449 pcr, NULL, false, NULL, 0); 450 451 return rc; 452 } 453 454 /* 455 * ima_appraise_measurement - appraise file measurement 456 * 457 * Call evm_verifyxattr() to verify the integrity of 'security.ima'. 458 * Assuming success, compare the xattr hash with the collected measurement. 459 * 460 * Return 0 on success, error code otherwise 461 */ 462 int ima_appraise_measurement(enum ima_hooks func, struct ima_iint_cache *iint, 463 struct file *file, const unsigned char *filename, 464 struct evm_ima_xattr_data *xattr_value, 465 int xattr_len, const struct modsig *modsig, 466 bool bprm_is_check) 467 { 468 static const char op[] = "appraise_data"; 469 int audit_msgno = AUDIT_INTEGRITY_DATA; 470 const char *cause = "unknown"; 471 struct dentry *dentry = file_dentry(file); 472 struct inode *inode = d_backing_inode(dentry); 473 enum integrity_status status = INTEGRITY_UNKNOWN; 474 int rc = xattr_len; 475 bool try_modsig = iint->flags & IMA_MODSIG_ALLOWED && modsig; 476 477 /* If not appraising a modsig, we need an xattr. */ 478 if (!(inode->i_opflags & IOP_XATTR) && !try_modsig) 479 return INTEGRITY_UNKNOWN; 480 481 /* 482 * Unlike any of the other LSM hooks where the kernel enforces file 483 * integrity, enforcing file integrity for the bprm_creds_for_exec() 484 * LSM hook with the AT_EXECVE_CHECK flag is left up to the discretion 485 * of the script interpreter(userspace). Differentiate kernel and 486 * userspace enforced integrity audit messages. 487 */ 488 if (bprm_is_check) 489 audit_msgno = AUDIT_INTEGRITY_USERSPACE; 490 491 /* If reading the xattr failed and there's no modsig, error out. */ 492 if (rc <= 0 && !try_modsig) { 493 if (rc && rc != -ENODATA) 494 goto out; 495 496 if (iint->flags & IMA_DIGSIG_REQUIRED) { 497 if (iint->flags & IMA_VERITY_REQUIRED) 498 cause = "verity-signature-required"; 499 else 500 cause = "IMA-signature-required"; 501 } else { 502 cause = "missing-hash"; 503 } 504 505 status = INTEGRITY_NOLABEL; 506 if (file->f_mode & FMODE_CREATED) 507 iint->flags |= IMA_NEW_FILE; 508 if ((iint->flags & IMA_NEW_FILE) && 509 (!(iint->flags & IMA_DIGSIG_REQUIRED) || 510 (inode->i_size == 0))) 511 status = INTEGRITY_PASS; 512 goto out; 513 } 514 515 status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, 516 rc < 0 ? 0 : rc); 517 switch (status) { 518 case INTEGRITY_PASS: 519 case INTEGRITY_PASS_IMMUTABLE: 520 case INTEGRITY_UNKNOWN: 521 break; 522 case INTEGRITY_NOXATTRS: /* No EVM protected xattrs. */ 523 /* It's fine not to have xattrs when using a modsig. */ 524 if (try_modsig) 525 break; 526 fallthrough; 527 case INTEGRITY_NOLABEL: /* No security.evm xattr. */ 528 cause = "missing-HMAC"; 529 goto out; 530 case INTEGRITY_FAIL_IMMUTABLE: 531 set_bit(IMA_DIGSIG, &iint->atomic_flags); 532 cause = "invalid-fail-immutable"; 533 goto out; 534 case INTEGRITY_FAIL: /* Invalid HMAC/signature. */ 535 cause = "invalid-HMAC"; 536 goto out; 537 default: 538 WARN_ONCE(true, "Unexpected integrity status %d\n", status); 539 } 540 541 if (xattr_value) 542 rc = xattr_verify(func, iint, xattr_value, xattr_len, &status, 543 &cause); 544 545 /* 546 * If we have a modsig and either no imasig or the imasig's key isn't 547 * known, then try verifying the modsig. 548 */ 549 if (try_modsig && 550 (!xattr_value || xattr_value->type == IMA_XATTR_DIGEST_NG || 551 rc == -ENOKEY)) 552 rc = modsig_verify(func, modsig, &status, &cause); 553 554 out: 555 /* 556 * File signatures on some filesystems can not be properly verified. 557 * When such filesystems are mounted by an untrusted mounter or on a 558 * system not willing to accept such a risk, fail the file signature 559 * verification. 560 */ 561 if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) && 562 ((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) || 563 (iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) { 564 status = INTEGRITY_FAIL; 565 cause = "unverifiable-signature"; 566 integrity_audit_msg(audit_msgno, inode, filename, 567 op, cause, rc, 0); 568 } else if (status != INTEGRITY_PASS) { 569 /* Fix mode, but don't replace file signatures. */ 570 if ((ima_appraise & IMA_APPRAISE_FIX) && !try_modsig && 571 (!xattr_value || 572 xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { 573 if (!ima_fix_xattr(dentry, iint)) 574 status = INTEGRITY_PASS; 575 } else if (status == INTEGRITY_NOLABEL) { 576 if (!evm_fix_hmac(dentry, XATTR_NAME_IMA, 577 (const char *)xattr_value, 578 xattr_len)) 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_msgno, 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 ima_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 * @ia_valid: for the UID and GID status 631 * 632 * Changes to a dentry's metadata might result in needing to appraise. 633 * 634 * This function is called from notify_change(), which expects the caller 635 * to lock the inode's i_mutex. 636 */ 637 static void ima_inode_post_setattr(struct mnt_idmap *idmap, 638 struct dentry *dentry, int ia_valid) 639 { 640 struct inode *inode = d_backing_inode(dentry); 641 struct ima_iint_cache *iint; 642 int action; 643 644 if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode) 645 || !(inode->i_opflags & IOP_XATTR)) 646 return; 647 648 action = ima_must_appraise(idmap, inode, MAY_ACCESS, POST_SETATTR); 649 iint = ima_iint_find(inode); 650 if (iint) { 651 set_bit(IMA_CHANGE_ATTR, &iint->atomic_flags); 652 if (!action) 653 clear_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); 654 } 655 } 656 657 /* 658 * ima_protect_xattr - protect 'security.ima' 659 * 660 * Ensure that not just anyone can modify or remove 'security.ima'. 661 */ 662 static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name, 663 const void *xattr_value, size_t xattr_value_len) 664 { 665 if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) { 666 if (!capable(CAP_SYS_ADMIN)) 667 return -EPERM; 668 return 1; 669 } 670 return 0; 671 } 672 673 /* 674 * ima_reset_appraise_flags - reset ima_iint_cache flags 675 * 676 * @digsig: whether to clear/set IMA_DIGSIG flag, tristate values 677 * 0: clear IMA_DIGSIG 678 * 1: set IMA_DIGSIG 679 * -1: don't change IMA_DIGSIG 680 * 681 */ 682 static void ima_reset_appraise_flags(struct inode *inode, int digsig) 683 { 684 struct ima_iint_cache *iint; 685 686 if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)) 687 return; 688 689 iint = ima_iint_find(inode); 690 if (!iint) 691 return; 692 iint->measured_pcrs = 0; 693 set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags); 694 if (digsig == 1) 695 set_bit(IMA_DIGSIG, &iint->atomic_flags); 696 else if (digsig == 0) 697 clear_bit(IMA_DIGSIG, &iint->atomic_flags); 698 } 699 700 /** 701 * validate_hash_algo() - Block setxattr with unsupported hash algorithms 702 * @dentry: object of the setxattr() 703 * @xattr_value: userland supplied xattr value 704 * @xattr_value_len: length of xattr_value 705 * 706 * The xattr value is mapped to its hash algorithm, and this algorithm 707 * must be built in the kernel for the setxattr to be allowed. 708 * 709 * Emit an audit message when the algorithm is invalid. 710 * 711 * Return: 0 on success, else an error. 712 */ 713 static int validate_hash_algo(struct dentry *dentry, 714 const struct evm_ima_xattr_data *xattr_value, 715 size_t xattr_value_len) 716 { 717 char *path = NULL, *pathbuf = NULL; 718 enum hash_algo xattr_hash_algo; 719 const char *errmsg = "unavailable-hash-algorithm"; 720 unsigned int allowed_hashes; 721 722 xattr_hash_algo = ima_get_hash_algo(xattr_value, xattr_value_len); 723 724 allowed_hashes = atomic_read(&ima_setxattr_allowed_hash_algorithms); 725 726 if (allowed_hashes) { 727 /* success if the algorithm is allowed in the ima policy */ 728 if (allowed_hashes & (1U << xattr_hash_algo)) 729 return 0; 730 731 /* 732 * We use a different audit message when the hash algorithm 733 * is denied by a policy rule, instead of not being built 734 * in the kernel image 735 */ 736 errmsg = "denied-hash-algorithm"; 737 } else { 738 if (likely(xattr_hash_algo == ima_hash_algo)) 739 return 0; 740 741 /* allow any xattr using an algorithm built in the kernel */ 742 if (crypto_has_alg(hash_algo_name[xattr_hash_algo], 0, 0)) 743 return 0; 744 } 745 746 pathbuf = kmalloc(PATH_MAX, GFP_KERNEL); 747 if (!pathbuf) 748 return -EACCES; 749 750 path = dentry_path(dentry, pathbuf, PATH_MAX); 751 752 integrity_audit_msg(AUDIT_INTEGRITY_DATA, d_inode(dentry), path, 753 "set_data", errmsg, -EACCES, 0); 754 755 kfree(pathbuf); 756 757 return -EACCES; 758 } 759 760 static int ima_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry, 761 const char *xattr_name, const void *xattr_value, 762 size_t xattr_value_len, int flags) 763 { 764 const struct evm_ima_xattr_data *xvalue = xattr_value; 765 int digsig = 0; 766 int result; 767 int err; 768 769 result = ima_protect_xattr(dentry, xattr_name, xattr_value, 770 xattr_value_len); 771 if (result == 1) { 772 if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) 773 return -EINVAL; 774 775 err = validate_hash_algo(dentry, xvalue, xattr_value_len); 776 if (err) 777 return err; 778 779 digsig = (xvalue->type == EVM_IMA_XATTR_DIGSIG); 780 } else if (!strcmp(xattr_name, XATTR_NAME_EVM) && xattr_value_len > 0) { 781 digsig = (xvalue->type == EVM_XATTR_PORTABLE_DIGSIG); 782 } else { 783 digsig = -1; 784 } 785 if (result == 1 || evm_revalidate_status(xattr_name)) { 786 ima_reset_appraise_flags(d_backing_inode(dentry), digsig); 787 if (result == 1) 788 result = 0; 789 } 790 return result; 791 } 792 793 static int ima_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, 794 const char *acl_name, struct posix_acl *kacl) 795 { 796 if (evm_revalidate_status(acl_name)) 797 ima_reset_appraise_flags(d_backing_inode(dentry), -1); 798 799 return 0; 800 } 801 802 static int ima_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry, 803 const char *xattr_name) 804 { 805 int result, digsig = -1; 806 807 result = ima_protect_xattr(dentry, xattr_name, NULL, 0); 808 if (result == 1 || evm_revalidate_status(xattr_name)) { 809 if (!strcmp(xattr_name, XATTR_NAME_IMA)) 810 digsig = 0; 811 ima_reset_appraise_flags(d_backing_inode(dentry), digsig); 812 if (result == 1) 813 result = 0; 814 } 815 return result; 816 } 817 818 static int ima_inode_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry, 819 const char *acl_name) 820 { 821 return ima_inode_set_acl(idmap, dentry, acl_name, NULL); 822 } 823 824 static struct security_hook_list ima_appraise_hooks[] __ro_after_init = { 825 LSM_HOOK_INIT(inode_post_setattr, ima_inode_post_setattr), 826 LSM_HOOK_INIT(inode_setxattr, ima_inode_setxattr), 827 LSM_HOOK_INIT(inode_set_acl, ima_inode_set_acl), 828 LSM_HOOK_INIT(inode_removexattr, ima_inode_removexattr), 829 LSM_HOOK_INIT(inode_remove_acl, ima_inode_remove_acl), 830 }; 831 832 void __init init_ima_appraise_lsm(const struct lsm_id *lsmid) 833 { 834 security_add_hooks(ima_appraise_hooks, ARRAY_SIZE(ima_appraise_hooks), 835 lsmid); 836 } 837