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