1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * AppArmor security module 4 * 5 * This file contains AppArmor mediation of files 6 * 7 * Copyright (C) 1998-2008 Novell/SUSE 8 * Copyright 2009-2010 Canonical Ltd. 9 */ 10 11 #include <linux/tty.h> 12 #include <linux/fdtable.h> 13 #include <linux/file.h> 14 #include <linux/fs.h> 15 #include <linux/mount.h> 16 17 #include "include/apparmor.h" 18 #include "include/audit.h" 19 #include "include/cred.h" 20 #include "include/file.h" 21 #include "include/match.h" 22 #include "include/net.h" 23 #include "include/path.h" 24 #include "include/policy.h" 25 #include "include/label.h" 26 27 static u32 map_mask_to_chr_mask(u32 mask) 28 { 29 u32 m = mask & PERMS_CHRS_MASK; 30 31 if (mask & AA_MAY_GETATTR) 32 m |= MAY_READ; 33 if (mask & (AA_MAY_SETATTR | AA_MAY_CHMOD | AA_MAY_CHOWN)) 34 m |= MAY_WRITE; 35 36 return m; 37 } 38 39 /** 40 * file_audit_cb - call back for file specific audit fields 41 * @ab: audit_buffer (NOT NULL) 42 * @va: audit struct to audit values of (NOT NULL) 43 */ 44 static void file_audit_cb(struct audit_buffer *ab, void *va) 45 { 46 struct common_audit_data *sa = va; 47 struct apparmor_audit_data *ad = aad(sa); 48 kuid_t fsuid = ad->subj_cred ? ad->subj_cred->fsuid : current_fsuid(); 49 char str[10]; 50 51 if (ad->request & AA_AUDIT_FILE_MASK) { 52 aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs, 53 map_mask_to_chr_mask(ad->request)); 54 audit_log_format(ab, " requested_mask=\"%s\"", str); 55 } 56 if (ad->denied & AA_AUDIT_FILE_MASK) { 57 aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs, 58 map_mask_to_chr_mask(ad->denied)); 59 audit_log_format(ab, " denied_mask=\"%s\"", str); 60 } 61 if (ad->request & AA_AUDIT_FILE_MASK) { 62 audit_log_format(ab, " fsuid=%d", 63 from_kuid(&init_user_ns, fsuid)); 64 audit_log_format(ab, " ouid=%d", 65 from_kuid(&init_user_ns, ad->fs.ouid)); 66 } 67 68 if (ad->peer) { 69 audit_log_format(ab, " target="); 70 aa_label_xaudit(ab, labels_ns(ad->subj_label), ad->peer, 71 FLAG_VIEW_SUBNS, GFP_KERNEL); 72 } else if (ad->fs.target) { 73 audit_log_format(ab, " target="); 74 audit_log_untrustedstring(ab, ad->fs.target); 75 } 76 } 77 78 /** 79 * aa_audit_file - handle the auditing of file operations 80 * @subj_cred: cred of the subject 81 * @profile: the profile being enforced (NOT NULL) 82 * @perms: the permissions computed for the request (NOT NULL) 83 * @op: operation being mediated 84 * @request: permissions requested 85 * @name: name of object being mediated (MAYBE NULL) 86 * @target: name of target (MAYBE NULL) 87 * @tlabel: target label (MAY BE NULL) 88 * @ouid: object uid 89 * @info: extra information message (MAYBE NULL) 90 * @error: 0 if operation allowed else failure error code 91 * 92 * Returns: %0 or error on failure 93 */ 94 int aa_audit_file(const struct cred *subj_cred, 95 struct aa_profile *profile, struct aa_perms *perms, 96 const char *op, u32 request, const char *name, 97 const char *target, struct aa_label *tlabel, 98 kuid_t ouid, const char *info, int error) 99 { 100 int type = AUDIT_APPARMOR_AUTO; 101 DEFINE_AUDIT_DATA(ad, LSM_AUDIT_DATA_TASK, AA_CLASS_FILE, op); 102 103 ad.subj_cred = subj_cred; 104 ad.request = request; 105 ad.name = name; 106 ad.fs.target = target; 107 ad.peer = tlabel; 108 ad.fs.ouid = ouid; 109 ad.info = info; 110 ad.error = error; 111 ad.common.u.tsk = NULL; 112 113 if (likely(!ad.error)) { 114 u32 mask = perms->audit; 115 116 if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL)) 117 mask = 0xffff; 118 119 /* mask off perms that are not being force audited */ 120 ad.request &= mask; 121 122 if (likely(!ad.request)) 123 return 0; 124 type = AUDIT_APPARMOR_AUDIT; 125 } else { 126 /* only report permissions that were denied */ 127 ad.request = ad.request & ~perms->allow; 128 AA_BUG(!ad.request); 129 130 if (ad.request & perms->kill) 131 type = AUDIT_APPARMOR_KILL; 132 133 /* quiet known rejects, assumes quiet and kill do not overlap */ 134 if ((ad.request & perms->quiet) && 135 AUDIT_MODE(profile) != AUDIT_NOQUIET && 136 AUDIT_MODE(profile) != AUDIT_ALL) 137 ad.request &= ~perms->quiet; 138 139 if (!ad.request) 140 return ad.error; 141 } 142 143 ad.denied = ad.request & ~perms->allow; 144 return aa_audit(type, profile, &ad, file_audit_cb); 145 } 146 147 static int path_name(const char *op, const struct cred *subj_cred, 148 struct aa_label *label, 149 const struct path *path, int flags, char *buffer, 150 const char **name, struct path_cond *cond, u32 request) 151 { 152 struct aa_profile *profile; 153 const char *info = NULL; 154 int error; 155 156 error = aa_path_name(path, flags, buffer, name, &info, 157 labels_profile(label)->disconnected); 158 if (error) { 159 fn_for_each_confined(label, profile, 160 aa_audit_file(subj_cred, 161 profile, &nullperms, op, request, *name, 162 NULL, NULL, cond->uid, info, error)); 163 return error; 164 } 165 166 return 0; 167 } 168 169 struct aa_perms default_perms = {}; 170 /** 171 * aa_lookup_fperms - convert dfa compressed perms to internal perms 172 * @file_rules: the aa_policydb to lookup perms for (NOT NULL) 173 * @state: state in dfa 174 * @cond: conditions to consider (NOT NULL) 175 * 176 * TODO: convert from dfa + state to permission entry 177 * 178 * Returns: a pointer to a file permission set 179 */ 180 struct aa_perms *aa_lookup_fperms(struct aa_policydb *file_rules, 181 aa_state_t state, struct path_cond *cond) 182 { 183 unsigned int index = ACCEPT_TABLE(file_rules->dfa)[state]; 184 185 if (!(file_rules->perms)) 186 return &default_perms; 187 188 if (uid_eq(current_fsuid(), cond->uid)) 189 return &(file_rules->perms[index]); 190 191 return &(file_rules->perms[index + 1]); 192 } 193 194 /** 195 * aa_str_perms - find permission that match @name 196 * @file_rules: the aa_policydb to match against (NOT NULL) 197 * @start: state to start matching in 198 * @name: string to match against dfa (NOT NULL) 199 * @cond: conditions to consider for permission set computation (NOT NULL) 200 * @perms: Returns - the permissions found when matching @name 201 * 202 * Returns: the final state in @dfa when beginning @start and walking @name 203 */ 204 aa_state_t aa_str_perms(struct aa_policydb *file_rules, aa_state_t start, 205 const char *name, struct path_cond *cond, 206 struct aa_perms *perms) 207 { 208 aa_state_t state; 209 state = aa_dfa_match(file_rules->dfa, start, name); 210 *perms = *(aa_lookup_fperms(file_rules, state, cond)); 211 212 return state; 213 } 214 215 static int __aa_path_perm(const char *op, const struct cred *subj_cred, 216 struct aa_profile *profile, const char *name, 217 u32 request, struct path_cond *cond, int flags, 218 struct aa_perms *perms) 219 { 220 struct aa_ruleset *rules = list_first_entry(&profile->rules, 221 typeof(*rules), list); 222 int e = 0; 223 224 if (profile_unconfined(profile)) 225 return 0; 226 aa_str_perms(rules->file, rules->file->start[AA_CLASS_FILE], 227 name, cond, perms); 228 if (request & ~perms->allow) 229 e = -EACCES; 230 return aa_audit_file(subj_cred, 231 profile, perms, op, request, name, NULL, NULL, 232 cond->uid, NULL, e); 233 } 234 235 236 static int profile_path_perm(const char *op, const struct cred *subj_cred, 237 struct aa_profile *profile, 238 const struct path *path, char *buffer, u32 request, 239 struct path_cond *cond, int flags, 240 struct aa_perms *perms) 241 { 242 const char *name; 243 int error; 244 245 if (profile_unconfined(profile)) 246 return 0; 247 248 error = path_name(op, subj_cred, &profile->label, path, 249 flags | profile->path_flags, buffer, &name, cond, 250 request); 251 if (error) 252 return error; 253 return __aa_path_perm(op, subj_cred, profile, name, request, cond, 254 flags, perms); 255 } 256 257 /** 258 * aa_path_perm - do permissions check & audit for @path 259 * @op: operation being checked 260 * @subj_cred: subject cred 261 * @label: profile being enforced (NOT NULL) 262 * @path: path to check permissions of (NOT NULL) 263 * @flags: any additional path flags beyond what the profile specifies 264 * @request: requested permissions 265 * @cond: conditional info for this request (NOT NULL) 266 * 267 * Returns: %0 else error if access denied or other error 268 */ 269 int aa_path_perm(const char *op, const struct cred *subj_cred, 270 struct aa_label *label, 271 const struct path *path, int flags, u32 request, 272 struct path_cond *cond) 273 { 274 struct aa_perms perms = {}; 275 struct aa_profile *profile; 276 char *buffer = NULL; 277 int error; 278 279 flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 280 0); 281 buffer = aa_get_buffer(false); 282 if (!buffer) 283 return -ENOMEM; 284 error = fn_for_each_confined(label, profile, 285 profile_path_perm(op, subj_cred, profile, path, buffer, 286 request, cond, flags, &perms)); 287 288 aa_put_buffer(buffer); 289 290 return error; 291 } 292 293 /** 294 * xindex_is_subset - helper for aa_path_link 295 * @link: link permission set 296 * @target: target permission set 297 * 298 * test target x permissions are equal OR a subset of link x permissions 299 * this is done as part of the subset test, where a hardlink must have 300 * a subset of permissions that the target has. 301 * 302 * Returns: true if subset else false 303 */ 304 static inline bool xindex_is_subset(u32 link, u32 target) 305 { 306 if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) || 307 ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE))) 308 return false; 309 310 return true; 311 } 312 313 static int profile_path_link(const struct cred *subj_cred, 314 struct aa_profile *profile, 315 const struct path *link, char *buffer, 316 const struct path *target, char *buffer2, 317 struct path_cond *cond) 318 { 319 struct aa_ruleset *rules = list_first_entry(&profile->rules, 320 typeof(*rules), list); 321 const char *lname, *tname = NULL; 322 struct aa_perms lperms = {}, perms; 323 const char *info = NULL; 324 u32 request = AA_MAY_LINK; 325 aa_state_t state; 326 int error; 327 328 error = path_name(OP_LINK, subj_cred, &profile->label, link, 329 profile->path_flags, 330 buffer, &lname, cond, AA_MAY_LINK); 331 if (error) 332 goto audit; 333 334 /* buffer2 freed below, tname is pointer in buffer2 */ 335 error = path_name(OP_LINK, subj_cred, &profile->label, target, 336 profile->path_flags, 337 buffer2, &tname, cond, AA_MAY_LINK); 338 if (error) 339 goto audit; 340 341 error = -EACCES; 342 /* aa_str_perms - handles the case of the dfa being NULL */ 343 state = aa_str_perms(rules->file, 344 rules->file->start[AA_CLASS_FILE], lname, 345 cond, &lperms); 346 347 if (!(lperms.allow & AA_MAY_LINK)) 348 goto audit; 349 350 /* test to see if target can be paired with link */ 351 state = aa_dfa_null_transition(rules->file->dfa, state); 352 aa_str_perms(rules->file, state, tname, cond, &perms); 353 354 /* force audit/quiet masks for link are stored in the second entry 355 * in the link pair. 356 */ 357 lperms.audit = perms.audit; 358 lperms.quiet = perms.quiet; 359 lperms.kill = perms.kill; 360 361 if (!(perms.allow & AA_MAY_LINK)) { 362 info = "target restricted"; 363 lperms = perms; 364 goto audit; 365 } 366 367 /* done if link subset test is not required */ 368 if (!(perms.allow & AA_LINK_SUBSET)) 369 goto done_tests; 370 371 /* Do link perm subset test requiring allowed permission on link are 372 * a subset of the allowed permissions on target. 373 */ 374 aa_str_perms(rules->file, rules->file->start[AA_CLASS_FILE], 375 tname, cond, &perms); 376 377 /* AA_MAY_LINK is not considered in the subset test */ 378 request = lperms.allow & ~AA_MAY_LINK; 379 lperms.allow &= perms.allow | AA_MAY_LINK; 380 381 request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow); 382 if (request & ~lperms.allow) { 383 goto audit; 384 } else if ((lperms.allow & MAY_EXEC) && 385 !xindex_is_subset(lperms.xindex, perms.xindex)) { 386 lperms.allow &= ~MAY_EXEC; 387 request |= MAY_EXEC; 388 info = "link not subset of target"; 389 goto audit; 390 } 391 392 done_tests: 393 error = 0; 394 395 audit: 396 return aa_audit_file(subj_cred, 397 profile, &lperms, OP_LINK, request, lname, tname, 398 NULL, cond->uid, info, error); 399 } 400 401 /** 402 * aa_path_link - Handle hard link permission check 403 * @subj_cred: subject cred 404 * @label: the label being enforced (NOT NULL) 405 * @old_dentry: the target dentry (NOT NULL) 406 * @new_dir: directory the new link will be created in (NOT NULL) 407 * @new_dentry: the link being created (NOT NULL) 408 * 409 * Handle the permission test for a link & target pair. Permission 410 * is encoded as a pair where the link permission is determined 411 * first, and if allowed, the target is tested. The target test 412 * is done from the point of the link match (not start of DFA) 413 * making the target permission dependent on the link permission match. 414 * 415 * The subset test if required forces that permissions granted 416 * on link are a subset of the permission granted to target. 417 * 418 * Returns: %0 if allowed else error 419 */ 420 int aa_path_link(const struct cred *subj_cred, 421 struct aa_label *label, struct dentry *old_dentry, 422 const struct path *new_dir, struct dentry *new_dentry) 423 { 424 struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry }; 425 struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry }; 426 struct path_cond cond = { 427 d_backing_inode(old_dentry)->i_uid, 428 d_backing_inode(old_dentry)->i_mode 429 }; 430 char *buffer = NULL, *buffer2 = NULL; 431 struct aa_profile *profile; 432 int error; 433 434 /* buffer freed below, lname is pointer in buffer */ 435 buffer = aa_get_buffer(false); 436 buffer2 = aa_get_buffer(false); 437 error = -ENOMEM; 438 if (!buffer || !buffer2) 439 goto out; 440 441 error = fn_for_each_confined(label, profile, 442 profile_path_link(subj_cred, profile, &link, buffer, 443 &target, buffer2, &cond)); 444 out: 445 aa_put_buffer(buffer); 446 aa_put_buffer(buffer2); 447 return error; 448 } 449 450 static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label, 451 u32 request) 452 { 453 struct aa_label *l, *old; 454 455 /* update caching of label on file_ctx */ 456 spin_lock(&fctx->lock); 457 old = rcu_dereference_protected(fctx->label, 458 lockdep_is_held(&fctx->lock)); 459 l = aa_label_merge(old, label, GFP_ATOMIC); 460 if (l) { 461 if (l != old) { 462 rcu_assign_pointer(fctx->label, l); 463 aa_put_label(old); 464 } else 465 aa_put_label(l); 466 fctx->allow |= request; 467 } 468 spin_unlock(&fctx->lock); 469 } 470 471 static int __file_path_perm(const char *op, const struct cred *subj_cred, 472 struct aa_label *label, 473 struct aa_label *flabel, struct file *file, 474 u32 request, u32 denied, bool in_atomic) 475 { 476 struct aa_profile *profile; 477 struct aa_perms perms = {}; 478 vfsuid_t vfsuid = i_uid_into_vfsuid(file_mnt_idmap(file), 479 file_inode(file)); 480 struct path_cond cond = { 481 .uid = vfsuid_into_kuid(vfsuid), 482 .mode = file_inode(file)->i_mode 483 }; 484 char *buffer; 485 int flags, error; 486 487 /* revalidation due to label out of date. No revocation at this time */ 488 if (!denied && aa_label_is_subset(flabel, label)) 489 /* TODO: check for revocation on stale profiles */ 490 return 0; 491 492 flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0); 493 buffer = aa_get_buffer(in_atomic); 494 if (!buffer) 495 return -ENOMEM; 496 497 /* check every profile in task label not in current cache */ 498 error = fn_for_each_not_in_set(flabel, label, profile, 499 profile_path_perm(op, subj_cred, profile, 500 &file->f_path, buffer, 501 request, &cond, flags, &perms)); 502 if (denied && !error) { 503 /* 504 * check every profile in file label that was not tested 505 * in the initial check above. 506 * 507 * TODO: cache full perms so this only happens because of 508 * conditionals 509 * TODO: don't audit here 510 */ 511 if (label == flabel) 512 error = fn_for_each(label, profile, 513 profile_path_perm(op, subj_cred, 514 profile, &file->f_path, 515 buffer, request, &cond, flags, 516 &perms)); 517 else 518 error = fn_for_each_not_in_set(label, flabel, profile, 519 profile_path_perm(op, subj_cred, 520 profile, &file->f_path, 521 buffer, request, &cond, flags, 522 &perms)); 523 } 524 if (!error) 525 update_file_ctx(file_ctx(file), label, request); 526 527 aa_put_buffer(buffer); 528 529 return error; 530 } 531 532 static int __file_sock_perm(const char *op, const struct cred *subj_cred, 533 struct aa_label *label, 534 struct aa_label *flabel, struct file *file, 535 u32 request, u32 denied) 536 { 537 struct socket *sock = (struct socket *) file->private_data; 538 int error; 539 540 AA_BUG(!sock); 541 542 /* revalidation due to label out of date. No revocation at this time */ 543 if (!denied && aa_label_is_subset(flabel, label)) 544 return 0; 545 546 /* TODO: improve to skip profiles cached in flabel */ 547 error = aa_sock_file_perm(subj_cred, label, op, request, sock); 548 if (denied) { 549 /* TODO: improve to skip profiles checked above */ 550 /* check every profile in file label to is cached */ 551 last_error(error, aa_sock_file_perm(subj_cred, flabel, op, 552 request, sock)); 553 } 554 if (!error) 555 update_file_ctx(file_ctx(file), label, request); 556 557 return error; 558 } 559 560 /** 561 * aa_file_perm - do permission revalidation check & audit for @file 562 * @op: operation being checked 563 * @subj_cred: subject cred 564 * @label: label being enforced (NOT NULL) 565 * @file: file to revalidate access permissions on (NOT NULL) 566 * @request: requested permissions 567 * @in_atomic: whether allocations need to be done in atomic context 568 * 569 * Returns: %0 if access allowed else error 570 */ 571 int aa_file_perm(const char *op, const struct cred *subj_cred, 572 struct aa_label *label, struct file *file, 573 u32 request, bool in_atomic) 574 { 575 struct aa_file_ctx *fctx; 576 struct aa_label *flabel; 577 u32 denied; 578 int error = 0; 579 580 AA_BUG(!label); 581 AA_BUG(!file); 582 583 fctx = file_ctx(file); 584 585 rcu_read_lock(); 586 flabel = rcu_dereference(fctx->label); 587 AA_BUG(!flabel); 588 589 /* revalidate access, if task is unconfined, or the cached cred 590 * doesn't match or if the request is for more permissions than 591 * was granted. 592 * 593 * Note: the test for !unconfined(flabel) is to handle file 594 * delegation from unconfined tasks 595 */ 596 denied = request & ~fctx->allow; 597 if (unconfined(label) || unconfined(flabel) || 598 (!denied && aa_label_is_subset(flabel, label))) { 599 rcu_read_unlock(); 600 goto done; 601 } 602 603 flabel = aa_get_newest_label(flabel); 604 rcu_read_unlock(); 605 /* TODO: label cross check */ 606 607 if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry)) 608 error = __file_path_perm(op, subj_cred, label, flabel, file, 609 request, denied, in_atomic); 610 611 else if (S_ISSOCK(file_inode(file)->i_mode)) 612 error = __file_sock_perm(op, subj_cred, label, flabel, file, 613 request, denied); 614 aa_put_label(flabel); 615 616 done: 617 return error; 618 } 619 620 static void revalidate_tty(const struct cred *subj_cred, struct aa_label *label) 621 { 622 struct tty_struct *tty; 623 int drop_tty = 0; 624 625 tty = get_current_tty(); 626 if (!tty) 627 return; 628 629 spin_lock(&tty->files_lock); 630 if (!list_empty(&tty->tty_files)) { 631 struct tty_file_private *file_priv; 632 struct file *file; 633 /* TODO: Revalidate access to controlling tty. */ 634 file_priv = list_first_entry(&tty->tty_files, 635 struct tty_file_private, list); 636 file = file_priv->file; 637 638 if (aa_file_perm(OP_INHERIT, subj_cred, label, file, 639 MAY_READ | MAY_WRITE, IN_ATOMIC)) 640 drop_tty = 1; 641 } 642 spin_unlock(&tty->files_lock); 643 tty_kref_put(tty); 644 645 if (drop_tty) 646 no_tty(); 647 } 648 649 struct cred_label { 650 const struct cred *cred; 651 struct aa_label *label; 652 }; 653 654 static int match_file(const void *p, struct file *file, unsigned int fd) 655 { 656 struct cred_label *cl = (struct cred_label *)p; 657 658 if (aa_file_perm(OP_INHERIT, cl->cred, cl->label, file, 659 aa_map_file_to_perms(file), IN_ATOMIC)) 660 return fd + 1; 661 return 0; 662 } 663 664 665 /* based on selinux's flush_unauthorized_files */ 666 void aa_inherit_files(const struct cred *cred, struct files_struct *files) 667 { 668 struct aa_label *label = aa_get_newest_cred_label(cred); 669 struct cred_label cl = { 670 .cred = cred, 671 .label = label, 672 }; 673 struct file *devnull = NULL; 674 unsigned int n; 675 676 revalidate_tty(cred, label); 677 678 /* Revalidate access to inherited open files. */ 679 n = iterate_fd(files, 0, match_file, &cl); 680 if (!n) /* none found? */ 681 goto out; 682 683 devnull = dentry_open(&aa_null, O_RDWR, cred); 684 if (IS_ERR(devnull)) 685 devnull = NULL; 686 /* replace all the matching ones with this */ 687 do { 688 replace_fd(n - 1, devnull, 0); 689 } while ((n = iterate_fd(files, n, match_file, &cl)) != 0); 690 if (devnull) 691 fput(devnull); 692 out: 693 aa_put_label(label); 694 } 695