1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Integrity Measurement Architecture 4 * 5 * Copyright (C) 2005,2006,2007,2008 IBM Corporation 6 * 7 * Authors: 8 * Reiner Sailer <sailer@watson.ibm.com> 9 * Serge Hallyn <serue@us.ibm.com> 10 * Kylene Hall <kylene@us.ibm.com> 11 * Mimi Zohar <zohar@us.ibm.com> 12 * 13 * File: ima_main.c 14 * implements the IMA hooks: ima_bprm_check, ima_file_mmap, 15 * and ima_file_check. 16 */ 17 18 #include <linux/module.h> 19 #include <linux/file.h> 20 #include <linux/binfmts.h> 21 #include <linux/kernel_read_file.h> 22 #include <linux/mount.h> 23 #include <linux/mman.h> 24 #include <linux/slab.h> 25 #include <linux/xattr.h> 26 #include <linux/ima.h> 27 #include <linux/fs.h> 28 #include <linux/iversion.h> 29 #include <linux/evm.h> 30 #include <linux/crash_dump.h> 31 32 #include "ima.h" 33 34 #ifdef CONFIG_IMA_APPRAISE 35 int ima_appraise = IMA_APPRAISE_ENFORCE; 36 #else 37 int ima_appraise; 38 #endif 39 40 int __ro_after_init ima_hash_algo = HASH_ALGO_SHA1; 41 static int hash_setup_done; 42 static int ima_disabled __ro_after_init; 43 44 static struct notifier_block ima_lsm_policy_notifier = { 45 .notifier_call = ima_lsm_policy_change, 46 }; 47 48 static int __init ima_setup(char *str) 49 { 50 if (!is_kdump_kernel()) { 51 pr_info("Warning: ima setup option only permitted in kdump"); 52 return 1; 53 } 54 55 if (strncmp(str, "off", 3) == 0) 56 ima_disabled = 1; 57 else if (strncmp(str, "on", 2) == 0) 58 ima_disabled = 0; 59 else 60 pr_err("Invalid ima setup option: \"%s\" , please specify ima=on|off.", str); 61 62 return 1; 63 } 64 __setup("ima=", ima_setup); 65 66 static int __init hash_setup(char *str) 67 { 68 struct ima_template_desc *template_desc = ima_template_desc_current(); 69 int i; 70 71 if (hash_setup_done) 72 return 1; 73 74 if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) { 75 if (strncmp(str, "sha1", 4) == 0) { 76 ima_hash_algo = HASH_ALGO_SHA1; 77 } else if (strncmp(str, "md5", 3) == 0) { 78 ima_hash_algo = HASH_ALGO_MD5; 79 } else { 80 pr_err("invalid hash algorithm \"%s\" for template \"%s\"", 81 str, IMA_TEMPLATE_IMA_NAME); 82 return 1; 83 } 84 goto out; 85 } 86 87 i = match_string(hash_algo_name, HASH_ALGO__LAST, str); 88 if (i < 0) { 89 pr_err("invalid hash algorithm \"%s\"", str); 90 return 1; 91 } 92 93 ima_hash_algo = i; 94 out: 95 hash_setup_done = 1; 96 return 1; 97 } 98 __setup("ima_hash=", hash_setup); 99 100 enum hash_algo ima_get_current_hash_algo(void) 101 { 102 return ima_hash_algo; 103 } 104 105 /* Prevent mmap'ing a file execute that is already mmap'ed write */ 106 static int mmap_violation_check(enum ima_hooks func, struct file *file, 107 char **pathbuf, const char **pathname, 108 char *filename) 109 { 110 struct inode *inode; 111 int rc = 0; 112 113 if ((func == MMAP_CHECK || func == MMAP_CHECK_REQPROT) && 114 mapping_writably_mapped(file->f_mapping)) { 115 rc = -ETXTBSY; 116 inode = file_inode(file); 117 118 if (!*pathbuf) /* ima_rdwr_violation possibly pre-fetched */ 119 *pathname = ima_d_path(&file->f_path, pathbuf, 120 filename); 121 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, *pathname, 122 "mmap_file", "mmapped_writers", rc, 0); 123 } 124 return rc; 125 } 126 127 /* 128 * ima_rdwr_violation_check 129 * 130 * Only invalidate the PCR for measured files: 131 * - Opening a file for write when already open for read, 132 * results in a time of measure, time of use (ToMToU) error. 133 * - Opening a file for read when already open for write, 134 * could result in a file measurement error. 135 * 136 */ 137 static void ima_rdwr_violation_check(struct file *file, 138 struct ima_iint_cache *iint, 139 int must_measure, 140 char **pathbuf, 141 const char **pathname, 142 char *filename) 143 { 144 struct inode *inode = file_inode(file); 145 fmode_t mode = file->f_mode; 146 bool send_tomtou = false, send_writers = false; 147 148 if (mode & FMODE_WRITE) { 149 if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) { 150 if (!iint) 151 iint = ima_iint_find(inode); 152 153 /* IMA_MEASURE is set from reader side */ 154 if (iint && test_and_clear_bit(IMA_MAY_EMIT_TOMTOU, 155 &iint->atomic_flags)) 156 send_tomtou = true; 157 } 158 } else { 159 if (must_measure) 160 set_bit(IMA_MAY_EMIT_TOMTOU, &iint->atomic_flags); 161 162 /* Limit number of open_writers violations */ 163 if (inode_is_open_for_write(inode) && must_measure) { 164 if (!test_and_set_bit(IMA_EMITTED_OPENWRITERS, 165 &iint->atomic_flags)) 166 send_writers = true; 167 } 168 } 169 170 if (!send_tomtou && !send_writers) 171 return; 172 173 *pathname = ima_d_path(&file->f_path, pathbuf, filename); 174 175 if (send_tomtou) 176 ima_add_violation(file, *pathname, iint, 177 "invalid_pcr", "ToMToU"); 178 if (send_writers) 179 ima_add_violation(file, *pathname, iint, 180 "invalid_pcr", "open_writers"); 181 } 182 183 static void ima_check_last_writer(struct ima_iint_cache *iint, 184 struct inode *inode, struct file *file) 185 { 186 fmode_t mode = file->f_mode; 187 bool update; 188 189 if (!(mode & FMODE_WRITE)) 190 return; 191 192 mutex_lock(&iint->mutex); 193 if (atomic_read(&inode->i_writecount) == 1) { 194 struct kstat stat; 195 196 clear_bit(IMA_EMITTED_OPENWRITERS, &iint->atomic_flags); 197 198 update = test_and_clear_bit(IMA_UPDATE_XATTR, 199 &iint->atomic_flags); 200 if ((iint->flags & IMA_NEW_FILE) || 201 vfs_getattr_nosec(&file->f_path, &stat, 202 STATX_CHANGE_COOKIE, 203 AT_STATX_SYNC_AS_STAT) || 204 !(stat.result_mask & STATX_CHANGE_COOKIE) || 205 stat.change_cookie != iint->real_inode.version) { 206 iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE); 207 iint->measured_pcrs = 0; 208 if (update) 209 ima_update_xattr(iint, file); 210 } 211 } 212 mutex_unlock(&iint->mutex); 213 } 214 215 /** 216 * ima_file_free - called on __fput() 217 * @file: pointer to file structure being freed 218 * 219 * Flag files that changed, based on i_version 220 */ 221 static void ima_file_free(struct file *file) 222 { 223 struct inode *inode = file_inode(file); 224 struct ima_iint_cache *iint; 225 226 if (!ima_policy_flag || !S_ISREG(inode->i_mode)) 227 return; 228 229 iint = ima_iint_find(inode); 230 if (!iint) 231 return; 232 233 ima_check_last_writer(iint, inode, file); 234 } 235 236 static int process_measurement(struct file *file, const struct cred *cred, 237 struct lsm_prop *prop, char *buf, loff_t size, 238 int mask, enum ima_hooks func) 239 { 240 struct inode *real_inode, *inode = file_inode(file); 241 struct ima_iint_cache *iint = NULL; 242 struct ima_template_desc *template_desc = NULL; 243 struct inode *metadata_inode; 244 char *pathbuf = NULL; 245 char filename[NAME_MAX]; 246 const char *pathname = NULL; 247 int rc = 0, action, must_appraise = 0; 248 int pcr = CONFIG_IMA_MEASURE_PCR_IDX; 249 struct evm_ima_xattr_data *xattr_value = NULL; 250 struct modsig *modsig = NULL; 251 int xattr_len = 0; 252 bool violation_check; 253 enum hash_algo hash_algo; 254 unsigned int allowed_algos = 0; 255 256 if (!ima_policy_flag || !S_ISREG(inode->i_mode)) 257 return 0; 258 259 /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action 260 * bitmask based on the appraise/audit/measurement policy. 261 * Included is the appraise submask. 262 */ 263 action = ima_get_action(file_mnt_idmap(file), inode, cred, prop, 264 mask, func, &pcr, &template_desc, NULL, 265 &allowed_algos); 266 violation_check = ((func == FILE_CHECK || func == MMAP_CHECK || 267 func == MMAP_CHECK_REQPROT) && 268 (ima_policy_flag & IMA_MEASURE) && 269 ((action & IMA_MEASURE) || 270 (file->f_mode & FMODE_WRITE))); 271 if (!action && !violation_check) 272 return 0; 273 274 must_appraise = action & IMA_APPRAISE; 275 276 /* Is the appraise rule hook specific? */ 277 if (action & IMA_FILE_APPRAISE) 278 func = FILE_CHECK; 279 280 inode_lock(inode); 281 282 if (action) { 283 iint = ima_inode_get(inode); 284 if (!iint) 285 rc = -ENOMEM; 286 } 287 288 if (!rc && violation_check) 289 ima_rdwr_violation_check(file, iint, action & IMA_MEASURE, 290 &pathbuf, &pathname, filename); 291 292 inode_unlock(inode); 293 294 if (rc) 295 goto out; 296 if (!action) 297 goto out; 298 299 mutex_lock(&iint->mutex); 300 301 if (test_and_clear_bit(IMA_CHANGE_ATTR, &iint->atomic_flags)) 302 /* 303 * Reset appraisal flags (action and non-action rule-specific) 304 * if ima_inode_post_setattr was called. 305 */ 306 iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED | 307 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK | 308 IMA_NONACTION_RULE_FLAGS); 309 310 /* 311 * Re-evaulate the file if either the xattr has changed or the 312 * kernel has no way of detecting file change on the filesystem. 313 * (Limited to privileged mounted filesystems.) 314 */ 315 if (test_and_clear_bit(IMA_CHANGE_XATTR, &iint->atomic_flags) || 316 ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) && 317 !(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) && 318 !(action & IMA_FAIL_UNVERIFIABLE_SIGS))) { 319 iint->flags &= ~IMA_DONE_MASK; 320 iint->measured_pcrs = 0; 321 } 322 323 /* 324 * On stacked filesystems, detect and re-evaluate file data and 325 * metadata changes. 326 */ 327 real_inode = d_real_inode(file_dentry(file)); 328 if (real_inode != inode && 329 (action & IMA_DO_MASK) && (iint->flags & IMA_DONE_MASK)) { 330 if (!IS_I_VERSION(real_inode) || 331 integrity_inode_attrs_changed(&iint->real_inode, 332 real_inode)) { 333 iint->flags &= ~IMA_DONE_MASK; 334 iint->measured_pcrs = 0; 335 } 336 337 /* 338 * Reset the EVM status when metadata changed. 339 */ 340 metadata_inode = d_inode(d_real(file_dentry(file), 341 D_REAL_METADATA)); 342 if (evm_metadata_changed(inode, metadata_inode)) 343 iint->flags &= ~(IMA_APPRAISED | 344 IMA_APPRAISED_SUBMASK); 345 } 346 347 /* Determine if already appraised/measured based on bitmask 348 * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED, 349 * IMA_AUDIT, IMA_AUDITED) 350 */ 351 iint->flags |= action; 352 action &= IMA_DO_MASK; 353 action &= ~((iint->flags & (IMA_DONE_MASK ^ IMA_MEASURED)) >> 1); 354 355 /* If target pcr is already measured, unset IMA_MEASURE action */ 356 if ((action & IMA_MEASURE) && (iint->measured_pcrs & (0x1 << pcr))) 357 action ^= IMA_MEASURE; 358 359 /* HASH sets the digital signature and update flags, nothing else */ 360 if ((action & IMA_HASH) && 361 !(test_bit(IMA_DIGSIG, &iint->atomic_flags))) { 362 xattr_len = ima_read_xattr(file_dentry(file), 363 &xattr_value, xattr_len); 364 if ((xattr_value && xattr_len > 2) && 365 (xattr_value->type == EVM_IMA_XATTR_DIGSIG)) 366 set_bit(IMA_DIGSIG, &iint->atomic_flags); 367 iint->flags |= IMA_HASHED; 368 action ^= IMA_HASH; 369 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); 370 } 371 372 /* Nothing to do, just return existing appraised status */ 373 if (!action) { 374 if (must_appraise) { 375 rc = mmap_violation_check(func, file, &pathbuf, 376 &pathname, filename); 377 if (!rc) 378 rc = ima_get_cache_status(iint, func); 379 } 380 goto out_locked; 381 } 382 383 if ((action & IMA_APPRAISE_SUBMASK) || 384 strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0) { 385 /* read 'security.ima' */ 386 xattr_len = ima_read_xattr(file_dentry(file), 387 &xattr_value, xattr_len); 388 389 /* 390 * Read the appended modsig if allowed by the policy, and allow 391 * an additional measurement list entry, if needed, based on the 392 * template format and whether the file was already measured. 393 */ 394 if (iint->flags & IMA_MODSIG_ALLOWED) { 395 rc = ima_read_modsig(func, buf, size, &modsig); 396 397 if (!rc && ima_template_has_modsig(template_desc) && 398 iint->flags & IMA_MEASURED) 399 action |= IMA_MEASURE; 400 } 401 } 402 403 hash_algo = ima_get_hash_algo(xattr_value, xattr_len); 404 405 rc = ima_collect_measurement(iint, file, buf, size, hash_algo, modsig); 406 if (rc != 0 && rc != -EBADF && rc != -EINVAL) 407 goto out_locked; 408 409 if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */ 410 pathname = ima_d_path(&file->f_path, &pathbuf, filename); 411 412 if (action & IMA_MEASURE) 413 ima_store_measurement(iint, file, pathname, 414 xattr_value, xattr_len, modsig, pcr, 415 template_desc); 416 if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) { 417 rc = ima_check_blacklist(iint, modsig, pcr); 418 if (rc != -EPERM) { 419 inode_lock(inode); 420 rc = ima_appraise_measurement(func, iint, file, 421 pathname, xattr_value, 422 xattr_len, modsig); 423 inode_unlock(inode); 424 } 425 if (!rc) 426 rc = mmap_violation_check(func, file, &pathbuf, 427 &pathname, filename); 428 } 429 if (action & IMA_AUDIT) 430 ima_audit_measurement(iint, pathname); 431 432 if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO)) 433 rc = 0; 434 435 /* Ensure the digest was generated using an allowed algorithm */ 436 if (rc == 0 && must_appraise && allowed_algos != 0 && 437 (allowed_algos & (1U << hash_algo)) == 0) { 438 rc = -EACCES; 439 440 integrity_audit_msg(AUDIT_INTEGRITY_DATA, file_inode(file), 441 pathname, "collect_data", 442 "denied-hash-algorithm", rc, 0); 443 } 444 out_locked: 445 if ((mask & MAY_WRITE) && test_bit(IMA_DIGSIG, &iint->atomic_flags) && 446 !(iint->flags & IMA_NEW_FILE)) 447 rc = -EACCES; 448 mutex_unlock(&iint->mutex); 449 kfree(xattr_value); 450 ima_free_modsig(modsig); 451 out: 452 if (pathbuf) 453 __putname(pathbuf); 454 if (must_appraise) { 455 if (rc && (ima_appraise & IMA_APPRAISE_ENFORCE)) 456 return -EACCES; 457 if (file->f_mode & FMODE_WRITE) 458 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); 459 } 460 return 0; 461 } 462 463 /** 464 * ima_file_mmap - based on policy, collect/store measurement. 465 * @file: pointer to the file to be measured (May be NULL) 466 * @reqprot: protection requested by the application 467 * @prot: protection that will be applied by the kernel 468 * @flags: operational flags 469 * 470 * Measure files being mmapped executable based on the ima_must_measure() 471 * policy decision. 472 * 473 * On success return 0. On integrity appraisal error, assuming the file 474 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 475 */ 476 static int ima_file_mmap(struct file *file, unsigned long reqprot, 477 unsigned long prot, unsigned long flags) 478 { 479 struct lsm_prop prop; 480 int ret; 481 482 if (!file) 483 return 0; 484 485 security_current_getlsmprop_subj(&prop); 486 487 if (reqprot & PROT_EXEC) { 488 ret = process_measurement(file, current_cred(), &prop, NULL, 489 0, MAY_EXEC, MMAP_CHECK_REQPROT); 490 if (ret) 491 return ret; 492 } 493 494 if (prot & PROT_EXEC) 495 return process_measurement(file, current_cred(), &prop, NULL, 496 0, MAY_EXEC, MMAP_CHECK); 497 498 return 0; 499 } 500 501 /** 502 * ima_file_mprotect - based on policy, limit mprotect change 503 * @vma: vm_area_struct protection is set to 504 * @reqprot: protection requested by the application 505 * @prot: protection that will be applied by the kernel 506 * 507 * Files can be mmap'ed read/write and later changed to execute to circumvent 508 * IMA's mmap appraisal policy rules. Due to locking issues (mmap semaphore 509 * would be taken before i_mutex), files can not be measured or appraised at 510 * this point. Eliminate this integrity gap by denying the mprotect 511 * PROT_EXECUTE change, if an mmap appraise policy rule exists. 512 * 513 * On mprotect change success, return 0. On failure, return -EACESS. 514 */ 515 static int ima_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot, 516 unsigned long prot) 517 { 518 struct ima_template_desc *template = NULL; 519 struct file *file; 520 char filename[NAME_MAX]; 521 char *pathbuf = NULL; 522 const char *pathname = NULL; 523 struct inode *inode; 524 struct lsm_prop prop; 525 int result = 0; 526 int action; 527 int pcr; 528 529 /* Is mprotect making an mmap'ed file executable? */ 530 if (!(ima_policy_flag & IMA_APPRAISE) || !vma->vm_file || 531 !(prot & PROT_EXEC) || (vma->vm_flags & VM_EXEC)) 532 return 0; 533 534 security_current_getlsmprop_subj(&prop); 535 inode = file_inode(vma->vm_file); 536 action = ima_get_action(file_mnt_idmap(vma->vm_file), inode, 537 current_cred(), &prop, MAY_EXEC, MMAP_CHECK, 538 &pcr, &template, NULL, NULL); 539 action |= ima_get_action(file_mnt_idmap(vma->vm_file), inode, 540 current_cred(), &prop, MAY_EXEC, 541 MMAP_CHECK_REQPROT, &pcr, &template, NULL, 542 NULL); 543 544 /* Is the mmap'ed file in policy? */ 545 if (!(action & (IMA_MEASURE | IMA_APPRAISE_SUBMASK))) 546 return 0; 547 548 if (action & IMA_APPRAISE_SUBMASK) 549 result = -EPERM; 550 551 file = vma->vm_file; 552 pathname = ima_d_path(&file->f_path, &pathbuf, filename); 553 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, pathname, 554 "collect_data", "failed-mprotect", result, 0); 555 if (pathbuf) 556 __putname(pathbuf); 557 558 return result; 559 } 560 561 /** 562 * ima_bprm_check - based on policy, collect/store measurement. 563 * @bprm: contains the linux_binprm structure 564 * 565 * The OS protects against an executable file, already open for write, 566 * from being executed in deny_write_access() and an executable file, 567 * already open for execute, from being modified in get_write_access(). 568 * So we can be certain that what we verify and measure here is actually 569 * what is being executed. 570 * 571 * On success return 0. On integrity appraisal error, assuming the file 572 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 573 */ 574 static int ima_bprm_check(struct linux_binprm *bprm) 575 { 576 int ret; 577 struct lsm_prop prop; 578 579 security_current_getlsmprop_subj(&prop); 580 ret = process_measurement(bprm->file, current_cred(), 581 &prop, NULL, 0, MAY_EXEC, BPRM_CHECK); 582 if (ret) 583 return ret; 584 585 security_cred_getlsmprop(bprm->cred, &prop); 586 return process_measurement(bprm->file, bprm->cred, &prop, NULL, 0, 587 MAY_EXEC, CREDS_CHECK); 588 } 589 590 /** 591 * ima_bprm_creds_for_exec - collect/store/appraise measurement. 592 * @bprm: contains the linux_binprm structure 593 * 594 * Based on the IMA policy and the execveat(2) AT_EXECVE_CHECK flag, measure 595 * and appraise the integrity of a file to be executed by script interpreters. 596 * Unlike any of the other LSM hooks where the kernel enforces file integrity, 597 * enforcing file integrity is left up to the discretion of the script 598 * interpreter (userspace). 599 * 600 * On success return 0. On integrity appraisal error, assuming the file 601 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 602 */ 603 static int ima_bprm_creds_for_exec(struct linux_binprm *bprm) 604 { 605 /* 606 * As security_bprm_check() is called multiple times, both 607 * the script and the shebang interpreter are measured, appraised, 608 * and audited. Limit usage of this LSM hook to just measuring, 609 * appraising, and auditing the indirect script execution 610 * (e.g. ./sh example.sh). 611 */ 612 if (!bprm->is_check) 613 return 0; 614 615 return ima_bprm_check(bprm); 616 } 617 618 /** 619 * ima_file_check - based on policy, collect/store measurement. 620 * @file: pointer to the file to be measured 621 * @mask: contains MAY_READ, MAY_WRITE, MAY_EXEC or MAY_APPEND 622 * 623 * Measure files based on the ima_must_measure() policy decision. 624 * 625 * On success return 0. On integrity appraisal error, assuming the file 626 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 627 */ 628 static int ima_file_check(struct file *file, int mask) 629 { 630 struct lsm_prop prop; 631 632 security_current_getlsmprop_subj(&prop); 633 return process_measurement(file, current_cred(), &prop, NULL, 0, 634 mask & (MAY_READ | MAY_WRITE | MAY_EXEC | 635 MAY_APPEND), FILE_CHECK); 636 } 637 638 static int __ima_inode_hash(struct inode *inode, struct file *file, char *buf, 639 size_t buf_size) 640 { 641 struct ima_iint_cache *iint = NULL, tmp_iint; 642 int rc, hash_algo; 643 644 if (ima_policy_flag) { 645 iint = ima_iint_find(inode); 646 if (iint) 647 mutex_lock(&iint->mutex); 648 } 649 650 if ((!iint || !(iint->flags & IMA_COLLECTED)) && file) { 651 if (iint) 652 mutex_unlock(&iint->mutex); 653 654 memset(&tmp_iint, 0, sizeof(tmp_iint)); 655 mutex_init(&tmp_iint.mutex); 656 657 rc = ima_collect_measurement(&tmp_iint, file, NULL, 0, 658 ima_hash_algo, NULL); 659 if (rc < 0) { 660 /* ima_hash could be allocated in case of failure. */ 661 if (rc != -ENOMEM) 662 kfree(tmp_iint.ima_hash); 663 664 return -EOPNOTSUPP; 665 } 666 667 iint = &tmp_iint; 668 mutex_lock(&iint->mutex); 669 } 670 671 if (!iint) 672 return -EOPNOTSUPP; 673 674 /* 675 * ima_file_hash can be called when ima_collect_measurement has still 676 * not been called, we might not always have a hash. 677 */ 678 if (!iint->ima_hash || !(iint->flags & IMA_COLLECTED)) { 679 mutex_unlock(&iint->mutex); 680 return -EOPNOTSUPP; 681 } 682 683 if (buf) { 684 size_t copied_size; 685 686 copied_size = min_t(size_t, iint->ima_hash->length, buf_size); 687 memcpy(buf, iint->ima_hash->digest, copied_size); 688 } 689 hash_algo = iint->ima_hash->algo; 690 mutex_unlock(&iint->mutex); 691 692 if (iint == &tmp_iint) 693 kfree(iint->ima_hash); 694 695 return hash_algo; 696 } 697 698 /** 699 * ima_file_hash - return a measurement of the file 700 * @file: pointer to the file 701 * @buf: buffer in which to store the hash 702 * @buf_size: length of the buffer 703 * 704 * On success, return the hash algorithm (as defined in the enum hash_algo). 705 * If buf is not NULL, this function also outputs the hash into buf. 706 * If the hash is larger than buf_size, then only buf_size bytes will be copied. 707 * It generally just makes sense to pass a buffer capable of holding the largest 708 * possible hash: IMA_MAX_DIGEST_SIZE. 709 * The file hash returned is based on the entire file, including the appended 710 * signature. 711 * 712 * If the measurement cannot be performed, return -EOPNOTSUPP. 713 * If the parameters are incorrect, return -EINVAL. 714 */ 715 int ima_file_hash(struct file *file, char *buf, size_t buf_size) 716 { 717 if (!file) 718 return -EINVAL; 719 720 return __ima_inode_hash(file_inode(file), file, buf, buf_size); 721 } 722 EXPORT_SYMBOL_GPL(ima_file_hash); 723 724 /** 725 * ima_inode_hash - return the stored measurement if the inode has been hashed 726 * and is in the iint cache. 727 * @inode: pointer to the inode 728 * @buf: buffer in which to store the hash 729 * @buf_size: length of the buffer 730 * 731 * On success, return the hash algorithm (as defined in the enum hash_algo). 732 * If buf is not NULL, this function also outputs the hash into buf. 733 * If the hash is larger than buf_size, then only buf_size bytes will be copied. 734 * It generally just makes sense to pass a buffer capable of holding the largest 735 * possible hash: IMA_MAX_DIGEST_SIZE. 736 * The hash returned is based on the entire contents, including the appended 737 * signature. 738 * 739 * If IMA is disabled or if no measurement is available, return -EOPNOTSUPP. 740 * If the parameters are incorrect, return -EINVAL. 741 */ 742 int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size) 743 { 744 if (!inode) 745 return -EINVAL; 746 747 return __ima_inode_hash(inode, NULL, buf, buf_size); 748 } 749 EXPORT_SYMBOL_GPL(ima_inode_hash); 750 751 /** 752 * ima_post_create_tmpfile - mark newly created tmpfile as new 753 * @idmap: idmap of the mount the inode was found from 754 * @inode: inode of the newly created tmpfile 755 * 756 * No measuring, appraising or auditing of newly created tmpfiles is needed. 757 * Skip calling process_measurement(), but indicate which newly, created 758 * tmpfiles are in policy. 759 */ 760 static void ima_post_create_tmpfile(struct mnt_idmap *idmap, 761 struct inode *inode) 762 763 { 764 struct ima_iint_cache *iint; 765 int must_appraise; 766 767 if (!ima_policy_flag || !S_ISREG(inode->i_mode)) 768 return; 769 770 must_appraise = ima_must_appraise(idmap, inode, MAY_ACCESS, 771 FILE_CHECK); 772 if (!must_appraise) 773 return; 774 775 /* Nothing to do if we can't allocate memory */ 776 iint = ima_inode_get(inode); 777 if (!iint) 778 return; 779 780 /* needed for writing the security xattrs */ 781 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); 782 iint->ima_file_status = INTEGRITY_PASS; 783 } 784 785 /** 786 * ima_post_path_mknod - mark as a new inode 787 * @idmap: idmap of the mount the inode was found from 788 * @dentry: newly created dentry 789 * 790 * Mark files created via the mknodat syscall as new, so that the 791 * file data can be written later. 792 */ 793 static void ima_post_path_mknod(struct mnt_idmap *idmap, struct dentry *dentry) 794 { 795 struct ima_iint_cache *iint; 796 struct inode *inode = dentry->d_inode; 797 int must_appraise; 798 799 if (!ima_policy_flag || !S_ISREG(inode->i_mode)) 800 return; 801 802 must_appraise = ima_must_appraise(idmap, inode, MAY_ACCESS, 803 FILE_CHECK); 804 if (!must_appraise) 805 return; 806 807 /* Nothing to do if we can't allocate memory */ 808 iint = ima_inode_get(inode); 809 if (!iint) 810 return; 811 812 /* needed for re-opening empty files */ 813 iint->flags |= IMA_NEW_FILE; 814 } 815 816 /** 817 * ima_read_file - pre-measure/appraise hook decision based on policy 818 * @file: pointer to the file to be measured/appraised/audit 819 * @read_id: caller identifier 820 * @contents: whether a subsequent call will be made to ima_post_read_file() 821 * 822 * Permit reading a file based on policy. The policy rules are written 823 * in terms of the policy identifier. Appraising the integrity of 824 * a file requires a file descriptor. 825 * 826 * For permission return 0, otherwise return -EACCES. 827 */ 828 static int ima_read_file(struct file *file, enum kernel_read_file_id read_id, 829 bool contents) 830 { 831 enum ima_hooks func; 832 struct lsm_prop prop; 833 834 /* 835 * Do devices using pre-allocated memory run the risk of the 836 * firmware being accessible to the device prior to the completion 837 * of IMA's signature verification any more than when using two 838 * buffers? It may be desirable to include the buffer address 839 * in this API and walk all the dma_map_single() mappings to check. 840 */ 841 842 /* 843 * There will be a call made to ima_post_read_file() with 844 * a filled buffer, so we don't need to perform an extra 845 * read early here. 846 */ 847 if (contents) 848 return 0; 849 850 /* Read entire file for all partial reads. */ 851 func = read_idmap[read_id] ?: FILE_CHECK; 852 security_current_getlsmprop_subj(&prop); 853 return process_measurement(file, current_cred(), &prop, NULL, 0, 854 MAY_READ, func); 855 } 856 857 const int read_idmap[READING_MAX_ID] = { 858 [READING_FIRMWARE] = FIRMWARE_CHECK, 859 [READING_MODULE] = MODULE_CHECK, 860 [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK, 861 [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK, 862 [READING_POLICY] = POLICY_CHECK 863 }; 864 865 /** 866 * ima_post_read_file - in memory collect/appraise/audit measurement 867 * @file: pointer to the file to be measured/appraised/audit 868 * @buf: pointer to in memory file contents 869 * @size: size of in memory file contents 870 * @read_id: caller identifier 871 * 872 * Measure/appraise/audit in memory file based on policy. Policy rules 873 * are written in terms of a policy identifier. 874 * 875 * On success return 0. On integrity appraisal error, assuming the file 876 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 877 */ 878 static int ima_post_read_file(struct file *file, char *buf, loff_t size, 879 enum kernel_read_file_id read_id) 880 { 881 enum ima_hooks func; 882 struct lsm_prop prop; 883 884 /* permit signed certs */ 885 if (!file && read_id == READING_X509_CERTIFICATE) 886 return 0; 887 888 if (!file || !buf || size == 0) { /* should never happen */ 889 if (ima_appraise & IMA_APPRAISE_ENFORCE) 890 return -EACCES; 891 return 0; 892 } 893 894 func = read_idmap[read_id] ?: FILE_CHECK; 895 security_current_getlsmprop_subj(&prop); 896 return process_measurement(file, current_cred(), &prop, buf, size, 897 MAY_READ, func); 898 } 899 900 /** 901 * ima_load_data - appraise decision based on policy 902 * @id: kernel load data caller identifier 903 * @contents: whether the full contents will be available in a later 904 * call to ima_post_load_data(). 905 * 906 * Callers of this LSM hook can not measure, appraise, or audit the 907 * data provided by userspace. Enforce policy rules requiring a file 908 * signature (eg. kexec'ed kernel image). 909 * 910 * For permission return 0, otherwise return -EACCES. 911 */ 912 static int ima_load_data(enum kernel_load_data_id id, bool contents) 913 { 914 bool ima_enforce, sig_enforce; 915 916 ima_enforce = 917 (ima_appraise & IMA_APPRAISE_ENFORCE) == IMA_APPRAISE_ENFORCE; 918 919 switch (id) { 920 case LOADING_KEXEC_IMAGE: 921 if (IS_ENABLED(CONFIG_KEXEC_SIG) 922 && arch_ima_get_secureboot()) { 923 pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n"); 924 return -EACCES; 925 } 926 927 if (ima_enforce && (ima_appraise & IMA_APPRAISE_KEXEC)) { 928 pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n"); 929 return -EACCES; /* INTEGRITY_UNKNOWN */ 930 } 931 break; 932 case LOADING_FIRMWARE: 933 if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE) && !contents) { 934 pr_err("Prevent firmware sysfs fallback loading.\n"); 935 return -EACCES; /* INTEGRITY_UNKNOWN */ 936 } 937 break; 938 case LOADING_MODULE: 939 sig_enforce = is_module_sig_enforced(); 940 941 if (ima_enforce && (!sig_enforce 942 && (ima_appraise & IMA_APPRAISE_MODULES))) { 943 pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n"); 944 return -EACCES; /* INTEGRITY_UNKNOWN */ 945 } 946 break; 947 default: 948 break; 949 } 950 return 0; 951 } 952 953 /** 954 * ima_post_load_data - appraise decision based on policy 955 * @buf: pointer to in memory file contents 956 * @size: size of in memory file contents 957 * @load_id: kernel load data caller identifier 958 * @description: @load_id-specific description of contents 959 * 960 * Measure/appraise/audit in memory buffer based on policy. Policy rules 961 * are written in terms of a policy identifier. 962 * 963 * On success return 0. On integrity appraisal error, assuming the file 964 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 965 */ 966 static int ima_post_load_data(char *buf, loff_t size, 967 enum kernel_load_data_id load_id, 968 char *description) 969 { 970 if (load_id == LOADING_FIRMWARE) { 971 if ((ima_appraise & IMA_APPRAISE_FIRMWARE) && 972 (ima_appraise & IMA_APPRAISE_ENFORCE)) { 973 pr_err("Prevent firmware loading_store.\n"); 974 return -EACCES; /* INTEGRITY_UNKNOWN */ 975 } 976 return 0; 977 } 978 979 /* 980 * Measure the init_module syscall buffer containing the ELF image. 981 */ 982 if (load_id == LOADING_MODULE) 983 ima_measure_critical_data("modules", "init_module", 984 buf, size, true, NULL, 0); 985 986 return 0; 987 } 988 989 /** 990 * process_buffer_measurement - Measure the buffer or the buffer data hash 991 * @idmap: idmap of the mount the inode was found from 992 * @inode: inode associated with the object being measured (NULL for KEY_CHECK) 993 * @buf: pointer to the buffer that needs to be added to the log. 994 * @size: size of buffer(in bytes). 995 * @eventname: event name to be used for the buffer entry. 996 * @func: IMA hook 997 * @pcr: pcr to extend the measurement 998 * @func_data: func specific data, may be NULL 999 * @buf_hash: measure buffer data hash 1000 * @digest: buffer digest will be written to 1001 * @digest_len: buffer length 1002 * 1003 * Based on policy, either the buffer data or buffer data hash is measured 1004 * 1005 * Return: 0 if the buffer has been successfully measured, 1 if the digest 1006 * has been written to the passed location but not added to a measurement entry, 1007 * a negative value otherwise. 1008 */ 1009 int process_buffer_measurement(struct mnt_idmap *idmap, 1010 struct inode *inode, const void *buf, int size, 1011 const char *eventname, enum ima_hooks func, 1012 int pcr, const char *func_data, 1013 bool buf_hash, u8 *digest, size_t digest_len) 1014 { 1015 int ret = 0; 1016 const char *audit_cause = "ENOMEM"; 1017 struct ima_template_entry *entry = NULL; 1018 struct ima_iint_cache iint = {}; 1019 struct ima_event_data event_data = {.iint = &iint, 1020 .filename = eventname, 1021 .buf = buf, 1022 .buf_len = size}; 1023 struct ima_template_desc *template; 1024 struct ima_max_digest_data hash; 1025 struct ima_digest_data *hash_hdr = container_of(&hash.hdr, 1026 struct ima_digest_data, hdr); 1027 char digest_hash[IMA_MAX_DIGEST_SIZE]; 1028 int digest_hash_len = hash_digest_size[ima_hash_algo]; 1029 int violation = 0; 1030 int action = 0; 1031 struct lsm_prop prop; 1032 1033 if (digest && digest_len < digest_hash_len) 1034 return -EINVAL; 1035 1036 if (!ima_policy_flag && !digest) 1037 return -ENOENT; 1038 1039 template = ima_template_desc_buf(); 1040 if (!template) { 1041 ret = -EINVAL; 1042 audit_cause = "ima_template_desc_buf"; 1043 goto out; 1044 } 1045 1046 /* 1047 * Both LSM hooks and auxiliary based buffer measurements are 1048 * based on policy. To avoid code duplication, differentiate 1049 * between the LSM hooks and auxiliary buffer measurements, 1050 * retrieving the policy rule information only for the LSM hook 1051 * buffer measurements. 1052 */ 1053 if (func) { 1054 security_current_getlsmprop_subj(&prop); 1055 action = ima_get_action(idmap, inode, current_cred(), 1056 &prop, 0, func, &pcr, &template, 1057 func_data, NULL); 1058 if (!(action & IMA_MEASURE) && !digest) 1059 return -ENOENT; 1060 } 1061 1062 if (!pcr) 1063 pcr = CONFIG_IMA_MEASURE_PCR_IDX; 1064 1065 iint.ima_hash = hash_hdr; 1066 iint.ima_hash->algo = ima_hash_algo; 1067 iint.ima_hash->length = hash_digest_size[ima_hash_algo]; 1068 1069 ret = ima_calc_buffer_hash(buf, size, iint.ima_hash); 1070 if (ret < 0) { 1071 audit_cause = "hashing_error"; 1072 goto out; 1073 } 1074 1075 if (buf_hash) { 1076 memcpy(digest_hash, hash_hdr->digest, digest_hash_len); 1077 1078 ret = ima_calc_buffer_hash(digest_hash, digest_hash_len, 1079 iint.ima_hash); 1080 if (ret < 0) { 1081 audit_cause = "hashing_error"; 1082 goto out; 1083 } 1084 1085 event_data.buf = digest_hash; 1086 event_data.buf_len = digest_hash_len; 1087 } 1088 1089 if (digest) 1090 memcpy(digest, iint.ima_hash->digest, digest_hash_len); 1091 1092 if (!ima_policy_flag || (func && !(action & IMA_MEASURE))) 1093 return 1; 1094 1095 ret = ima_alloc_init_template(&event_data, &entry, template); 1096 if (ret < 0) { 1097 audit_cause = "alloc_entry"; 1098 goto out; 1099 } 1100 1101 ret = ima_store_template(entry, violation, NULL, event_data.buf, pcr); 1102 if (ret < 0) { 1103 audit_cause = "store_entry"; 1104 ima_free_template_entry(entry); 1105 } 1106 1107 out: 1108 if (ret < 0) 1109 integrity_audit_message(AUDIT_INTEGRITY_PCR, NULL, eventname, 1110 func_measure_str(func), 1111 audit_cause, ret, 0, ret); 1112 1113 return ret; 1114 } 1115 1116 /** 1117 * ima_kexec_cmdline - measure kexec cmdline boot args 1118 * @kernel_fd: file descriptor of the kexec kernel being loaded 1119 * @buf: pointer to buffer 1120 * @size: size of buffer 1121 * 1122 * Buffers can only be measured, not appraised. 1123 */ 1124 void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) 1125 { 1126 if (!buf || !size) 1127 return; 1128 1129 CLASS(fd, f)(kernel_fd); 1130 if (fd_empty(f)) 1131 return; 1132 1133 process_buffer_measurement(file_mnt_idmap(fd_file(f)), file_inode(fd_file(f)), 1134 buf, size, "kexec-cmdline", KEXEC_CMDLINE, 0, 1135 NULL, false, NULL, 0); 1136 } 1137 1138 /** 1139 * ima_measure_critical_data - measure kernel integrity critical data 1140 * @event_label: unique event label for grouping and limiting critical data 1141 * @event_name: event name for the record in the IMA measurement list 1142 * @buf: pointer to buffer data 1143 * @buf_len: length of buffer data (in bytes) 1144 * @hash: measure buffer data hash 1145 * @digest: buffer digest will be written to 1146 * @digest_len: buffer length 1147 * 1148 * Measure data critical to the integrity of the kernel into the IMA log 1149 * and extend the pcr. Examples of critical data could be various data 1150 * structures, policies, and states stored in kernel memory that can 1151 * impact the integrity of the system. 1152 * 1153 * Return: 0 if the buffer has been successfully measured, 1 if the digest 1154 * has been written to the passed location but not added to a measurement entry, 1155 * a negative value otherwise. 1156 */ 1157 int ima_measure_critical_data(const char *event_label, 1158 const char *event_name, 1159 const void *buf, size_t buf_len, 1160 bool hash, u8 *digest, size_t digest_len) 1161 { 1162 if (!event_name || !event_label || !buf || !buf_len) 1163 return -ENOPARAM; 1164 1165 return process_buffer_measurement(&nop_mnt_idmap, NULL, buf, buf_len, 1166 event_name, CRITICAL_DATA, 0, 1167 event_label, hash, digest, 1168 digest_len); 1169 } 1170 EXPORT_SYMBOL_GPL(ima_measure_critical_data); 1171 1172 #ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS 1173 1174 /** 1175 * ima_kernel_module_request - Prevent crypto-pkcs1(rsa,*) requests 1176 * @kmod_name: kernel module name 1177 * 1178 * Avoid a verification loop where verifying the signature of the modprobe 1179 * binary requires executing modprobe itself. Since the modprobe iint->mutex 1180 * is already held when the signature verification is performed, a deadlock 1181 * occurs as soon as modprobe is executed within the critical region, since 1182 * the same lock cannot be taken again. 1183 * 1184 * This happens when public_key_verify_signature(), in case of RSA algorithm, 1185 * use alg_name to store internal information in order to construct an 1186 * algorithm on the fly, but crypto_larval_lookup() will try to use alg_name 1187 * in order to load a kernel module with same name. 1188 * 1189 * Since we don't have any real "crypto-pkcs1(rsa,*)" kernel modules, 1190 * we are safe to fail such module request from crypto_larval_lookup(), and 1191 * avoid the verification loop. 1192 * 1193 * Return: Zero if it is safe to load the kernel module, -EINVAL otherwise. 1194 */ 1195 static int ima_kernel_module_request(char *kmod_name) 1196 { 1197 if (strncmp(kmod_name, "crypto-pkcs1(rsa,", 17) == 0) 1198 return -EINVAL; 1199 1200 return 0; 1201 } 1202 1203 #endif /* CONFIG_INTEGRITY_ASYMMETRIC_KEYS */ 1204 1205 static int __init init_ima(void) 1206 { 1207 int error; 1208 1209 /*Note that turning IMA off is intentionally limited to kdump kernel.*/ 1210 if (ima_disabled && is_kdump_kernel()) { 1211 pr_info("IMA functionality is disabled"); 1212 return 0; 1213 } 1214 1215 ima_appraise_parse_cmdline(); 1216 ima_init_template_list(); 1217 hash_setup(CONFIG_IMA_DEFAULT_HASH); 1218 error = ima_init(); 1219 1220 if (error && strcmp(hash_algo_name[ima_hash_algo], 1221 CONFIG_IMA_DEFAULT_HASH) != 0) { 1222 pr_info("Allocating %s failed, going to use default hash algorithm %s\n", 1223 hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH); 1224 hash_setup_done = 0; 1225 hash_setup(CONFIG_IMA_DEFAULT_HASH); 1226 error = ima_init(); 1227 } 1228 1229 if (error) 1230 return error; 1231 1232 error = register_blocking_lsm_notifier(&ima_lsm_policy_notifier); 1233 if (error) 1234 pr_warn("Couldn't register LSM notifier, error %d\n", error); 1235 1236 if (!error) 1237 ima_update_policy_flags(); 1238 1239 return error; 1240 } 1241 1242 static struct security_hook_list ima_hooks[] __ro_after_init = { 1243 LSM_HOOK_INIT(bprm_check_security, ima_bprm_check), 1244 LSM_HOOK_INIT(bprm_creds_for_exec, ima_bprm_creds_for_exec), 1245 LSM_HOOK_INIT(file_post_open, ima_file_check), 1246 LSM_HOOK_INIT(inode_post_create_tmpfile, ima_post_create_tmpfile), 1247 LSM_HOOK_INIT(file_release, ima_file_free), 1248 LSM_HOOK_INIT(mmap_file, ima_file_mmap), 1249 LSM_HOOK_INIT(file_mprotect, ima_file_mprotect), 1250 LSM_HOOK_INIT(kernel_load_data, ima_load_data), 1251 LSM_HOOK_INIT(kernel_post_load_data, ima_post_load_data), 1252 LSM_HOOK_INIT(kernel_read_file, ima_read_file), 1253 LSM_HOOK_INIT(kernel_post_read_file, ima_post_read_file), 1254 LSM_HOOK_INIT(path_post_mknod, ima_post_path_mknod), 1255 #ifdef CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS 1256 LSM_HOOK_INIT(key_post_create_or_update, ima_post_key_create_or_update), 1257 #endif 1258 #ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS 1259 LSM_HOOK_INIT(kernel_module_request, ima_kernel_module_request), 1260 #endif 1261 LSM_HOOK_INIT(inode_free_security_rcu, ima_inode_free_rcu), 1262 }; 1263 1264 static const struct lsm_id ima_lsmid = { 1265 .name = "ima", 1266 .id = LSM_ID_IMA, 1267 }; 1268 1269 static int __init init_ima_lsm(void) 1270 { 1271 ima_iintcache_init(); 1272 security_add_hooks(ima_hooks, ARRAY_SIZE(ima_hooks), &ima_lsmid); 1273 init_ima_appraise_lsm(&ima_lsmid); 1274 return 0; 1275 } 1276 1277 struct lsm_blob_sizes ima_blob_sizes __ro_after_init = { 1278 .lbs_inode = sizeof(struct ima_iint_cache *), 1279 }; 1280 1281 DEFINE_LSM(ima) = { 1282 .name = "ima", 1283 .init = init_ima_lsm, 1284 .order = LSM_ORDER_LAST, 1285 .blobs = &ima_blob_sizes, 1286 }; 1287 1288 late_initcall(init_ima); /* Start IMA after the TPM is available */ 1289