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