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