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 int __aa_path_perm(const char *op, struct aa_profile *profile, const char *name, 224 u32 request, struct path_cond *cond, int flags, 225 struct aa_perms *perms) 226 { 227 struct aa_ruleset *rules = &profile->rules; 228 int e = 0; 229 230 if (profile_unconfined(profile)) 231 return 0; 232 aa_str_perms(&(rules->file), rules->file.start[AA_CLASS_FILE], 233 name, cond, perms); 234 if (request & ~perms->allow) 235 e = -EACCES; 236 return aa_audit_file(profile, perms, op, request, name, NULL, NULL, 237 cond->uid, NULL, e); 238 } 239 240 241 static int profile_path_perm(const char *op, struct aa_profile *profile, 242 const struct path *path, char *buffer, u32 request, 243 struct path_cond *cond, int flags, 244 struct aa_perms *perms) 245 { 246 const char *name; 247 int error; 248 249 if (profile_unconfined(profile)) 250 return 0; 251 252 error = path_name(op, &profile->label, path, 253 flags | profile->path_flags, buffer, &name, cond, 254 request); 255 if (error) 256 return error; 257 return __aa_path_perm(op, profile, name, request, cond, flags, 258 perms); 259 } 260 261 /** 262 * aa_path_perm - do permissions check & audit for @path 263 * @op: operation being checked 264 * @label: profile being enforced (NOT NULL) 265 * @path: path to check permissions of (NOT NULL) 266 * @flags: any additional path flags beyond what the profile specifies 267 * @request: requested permissions 268 * @cond: conditional info for this request (NOT NULL) 269 * 270 * Returns: %0 else error if access denied or other error 271 */ 272 int aa_path_perm(const char *op, struct aa_label *label, 273 const struct path *path, int flags, u32 request, 274 struct path_cond *cond) 275 { 276 struct aa_perms perms = {}; 277 struct aa_profile *profile; 278 char *buffer = NULL; 279 int error; 280 281 flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 282 0); 283 buffer = aa_get_buffer(false); 284 if (!buffer) 285 return -ENOMEM; 286 error = fn_for_each_confined(label, profile, 287 profile_path_perm(op, profile, path, buffer, request, 288 cond, flags, &perms)); 289 290 aa_put_buffer(buffer); 291 292 return error; 293 } 294 295 /** 296 * xindex_is_subset - helper for aa_path_link 297 * @link: link permission set 298 * @target: target permission set 299 * 300 * test target x permissions are equal OR a subset of link x permissions 301 * this is done as part of the subset test, where a hardlink must have 302 * a subset of permissions that the target has. 303 * 304 * Returns: true if subset else false 305 */ 306 static inline bool xindex_is_subset(u32 link, u32 target) 307 { 308 if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) || 309 ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE))) 310 return false; 311 312 return true; 313 } 314 315 static int profile_path_link(struct aa_profile *profile, 316 const struct path *link, char *buffer, 317 const struct path *target, char *buffer2, 318 struct path_cond *cond) 319 { 320 struct aa_ruleset *rules = &profile->rules; 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, &profile->label, link, profile->path_flags, 329 buffer, &lname, cond, AA_MAY_LINK); 330 if (error) 331 goto audit; 332 333 /* buffer2 freed below, tname is pointer in buffer2 */ 334 error = path_name(OP_LINK, &profile->label, target, profile->path_flags, 335 buffer2, &tname, cond, AA_MAY_LINK); 336 if (error) 337 goto audit; 338 339 error = -EACCES; 340 /* aa_str_perms - handles the case of the dfa being NULL */ 341 state = aa_str_perms(&(rules->file), 342 rules->file.start[AA_CLASS_FILE], lname, 343 cond, &lperms); 344 345 if (!(lperms.allow & AA_MAY_LINK)) 346 goto audit; 347 348 /* test to see if target can be paired with link */ 349 state = aa_dfa_null_transition(rules->file.dfa, state); 350 aa_str_perms(&(rules->file), state, tname, cond, &perms); 351 352 /* force audit/quiet masks for link are stored in the second entry 353 * in the link pair. 354 */ 355 lperms.audit = perms.audit; 356 lperms.quiet = perms.quiet; 357 lperms.kill = perms.kill; 358 359 if (!(perms.allow & AA_MAY_LINK)) { 360 info = "target restricted"; 361 lperms = perms; 362 goto audit; 363 } 364 365 /* done if link subset test is not required */ 366 if (!(perms.allow & AA_LINK_SUBSET)) 367 goto done_tests; 368 369 /* Do link perm subset test requiring allowed permission on link are 370 * a subset of the allowed permissions on target. 371 */ 372 aa_str_perms(&(rules->file), rules->file.start[AA_CLASS_FILE], 373 tname, cond, &perms); 374 375 /* AA_MAY_LINK is not considered in the subset test */ 376 request = lperms.allow & ~AA_MAY_LINK; 377 lperms.allow &= perms.allow | AA_MAY_LINK; 378 379 request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow); 380 if (request & ~lperms.allow) { 381 goto audit; 382 } else if ((lperms.allow & MAY_EXEC) && 383 !xindex_is_subset(lperms.xindex, perms.xindex)) { 384 lperms.allow &= ~MAY_EXEC; 385 request |= MAY_EXEC; 386 info = "link not subset of target"; 387 goto audit; 388 } 389 390 done_tests: 391 error = 0; 392 393 audit: 394 return aa_audit_file(profile, &lperms, OP_LINK, request, lname, tname, 395 NULL, cond->uid, info, error); 396 } 397 398 /** 399 * aa_path_link - Handle hard link permission check 400 * @label: the label being enforced (NOT NULL) 401 * @old_dentry: the target dentry (NOT NULL) 402 * @new_dir: directory the new link will be created in (NOT NULL) 403 * @new_dentry: the link being created (NOT NULL) 404 * 405 * Handle the permission test for a link & target pair. Permission 406 * is encoded as a pair where the link permission is determined 407 * first, and if allowed, the target is tested. The target test 408 * is done from the point of the link match (not start of DFA) 409 * making the target permission dependent on the link permission match. 410 * 411 * The subset test if required forces that permissions granted 412 * on link are a subset of the permission granted to target. 413 * 414 * Returns: %0 if allowed else error 415 */ 416 int aa_path_link(struct aa_label *label, struct dentry *old_dentry, 417 const struct path *new_dir, struct dentry *new_dentry) 418 { 419 struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry }; 420 struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry }; 421 struct path_cond cond = { 422 d_backing_inode(old_dentry)->i_uid, 423 d_backing_inode(old_dentry)->i_mode 424 }; 425 char *buffer = NULL, *buffer2 = NULL; 426 struct aa_profile *profile; 427 int error; 428 429 /* buffer freed below, lname is pointer in buffer */ 430 buffer = aa_get_buffer(false); 431 buffer2 = aa_get_buffer(false); 432 error = -ENOMEM; 433 if (!buffer || !buffer2) 434 goto out; 435 436 error = fn_for_each_confined(label, profile, 437 profile_path_link(profile, &link, buffer, &target, 438 buffer2, &cond)); 439 out: 440 aa_put_buffer(buffer); 441 aa_put_buffer(buffer2); 442 return error; 443 } 444 445 static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label, 446 u32 request) 447 { 448 struct aa_label *l, *old; 449 450 /* update caching of label on file_ctx */ 451 spin_lock(&fctx->lock); 452 old = rcu_dereference_protected(fctx->label, 453 lockdep_is_held(&fctx->lock)); 454 l = aa_label_merge(old, label, GFP_ATOMIC); 455 if (l) { 456 if (l != old) { 457 rcu_assign_pointer(fctx->label, l); 458 aa_put_label(old); 459 } else 460 aa_put_label(l); 461 fctx->allow |= request; 462 } 463 spin_unlock(&fctx->lock); 464 } 465 466 static int __file_path_perm(const char *op, struct aa_label *label, 467 struct aa_label *flabel, struct file *file, 468 u32 request, u32 denied, bool in_atomic) 469 { 470 struct aa_profile *profile; 471 struct aa_perms perms = {}; 472 struct path_cond cond = { 473 .uid = i_uid_into_mnt(file_mnt_user_ns(file), file_inode(file)), 474 .mode = file_inode(file)->i_mode 475 }; 476 char *buffer; 477 int flags, error; 478 479 /* revalidation due to label out of date. No revocation at this time */ 480 if (!denied && aa_label_is_subset(flabel, label)) 481 /* TODO: check for revocation on stale profiles */ 482 return 0; 483 484 flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0); 485 buffer = aa_get_buffer(in_atomic); 486 if (!buffer) 487 return -ENOMEM; 488 489 /* check every profile in task label not in current cache */ 490 error = fn_for_each_not_in_set(flabel, label, profile, 491 profile_path_perm(op, profile, &file->f_path, buffer, 492 request, &cond, flags, &perms)); 493 if (denied && !error) { 494 /* 495 * check every profile in file label that was not tested 496 * in the initial check above. 497 * 498 * TODO: cache full perms so this only happens because of 499 * conditionals 500 * TODO: don't audit here 501 */ 502 if (label == flabel) 503 error = fn_for_each(label, profile, 504 profile_path_perm(op, profile, &file->f_path, 505 buffer, request, &cond, flags, 506 &perms)); 507 else 508 error = fn_for_each_not_in_set(label, flabel, profile, 509 profile_path_perm(op, profile, &file->f_path, 510 buffer, request, &cond, flags, 511 &perms)); 512 } 513 if (!error) 514 update_file_ctx(file_ctx(file), label, request); 515 516 aa_put_buffer(buffer); 517 518 return error; 519 } 520 521 static int __file_sock_perm(const char *op, struct aa_label *label, 522 struct aa_label *flabel, struct file *file, 523 u32 request, u32 denied) 524 { 525 struct socket *sock = (struct socket *) file->private_data; 526 int error; 527 528 AA_BUG(!sock); 529 530 /* revalidation due to label out of date. No revocation at this time */ 531 if (!denied && aa_label_is_subset(flabel, label)) 532 return 0; 533 534 /* TODO: improve to skip profiles cached in flabel */ 535 error = aa_sock_file_perm(label, op, request, sock); 536 if (denied) { 537 /* TODO: improve to skip profiles checked above */ 538 /* check every profile in file label to is cached */ 539 last_error(error, aa_sock_file_perm(flabel, op, request, sock)); 540 } 541 if (!error) 542 update_file_ctx(file_ctx(file), label, request); 543 544 return error; 545 } 546 547 /** 548 * aa_file_perm - do permission revalidation check & audit for @file 549 * @op: operation being checked 550 * @label: label being enforced (NOT NULL) 551 * @file: file to revalidate access permissions on (NOT NULL) 552 * @request: requested permissions 553 * @in_atomic: whether allocations need to be done in atomic context 554 * 555 * Returns: %0 if access allowed else error 556 */ 557 int aa_file_perm(const char *op, struct aa_label *label, struct file *file, 558 u32 request, bool in_atomic) 559 { 560 struct aa_file_ctx *fctx; 561 struct aa_label *flabel; 562 u32 denied; 563 int error = 0; 564 565 AA_BUG(!label); 566 AA_BUG(!file); 567 568 fctx = file_ctx(file); 569 570 rcu_read_lock(); 571 flabel = rcu_dereference(fctx->label); 572 AA_BUG(!flabel); 573 574 /* revalidate access, if task is unconfined, or the cached cred 575 * doesn't match or if the request is for more permissions than 576 * was granted. 577 * 578 * Note: the test for !unconfined(flabel) is to handle file 579 * delegation from unconfined tasks 580 */ 581 denied = request & ~fctx->allow; 582 if (unconfined(label) || unconfined(flabel) || 583 (!denied && aa_label_is_subset(flabel, label))) { 584 rcu_read_unlock(); 585 goto done; 586 } 587 588 flabel = aa_get_newest_label(flabel); 589 rcu_read_unlock(); 590 /* TODO: label cross check */ 591 592 if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry)) 593 error = __file_path_perm(op, label, flabel, file, request, 594 denied, in_atomic); 595 596 else if (S_ISSOCK(file_inode(file)->i_mode)) 597 error = __file_sock_perm(op, label, flabel, file, request, 598 denied); 599 aa_put_label(flabel); 600 601 done: 602 return error; 603 } 604 605 static void revalidate_tty(struct aa_label *label) 606 { 607 struct tty_struct *tty; 608 int drop_tty = 0; 609 610 tty = get_current_tty(); 611 if (!tty) 612 return; 613 614 spin_lock(&tty->files_lock); 615 if (!list_empty(&tty->tty_files)) { 616 struct tty_file_private *file_priv; 617 struct file *file; 618 /* TODO: Revalidate access to controlling tty. */ 619 file_priv = list_first_entry(&tty->tty_files, 620 struct tty_file_private, list); 621 file = file_priv->file; 622 623 if (aa_file_perm(OP_INHERIT, label, file, MAY_READ | MAY_WRITE, 624 IN_ATOMIC)) 625 drop_tty = 1; 626 } 627 spin_unlock(&tty->files_lock); 628 tty_kref_put(tty); 629 630 if (drop_tty) 631 no_tty(); 632 } 633 634 static int match_file(const void *p, struct file *file, unsigned int fd) 635 { 636 struct aa_label *label = (struct aa_label *)p; 637 638 if (aa_file_perm(OP_INHERIT, label, file, aa_map_file_to_perms(file), 639 IN_ATOMIC)) 640 return fd + 1; 641 return 0; 642 } 643 644 645 /* based on selinux's flush_unauthorized_files */ 646 void aa_inherit_files(const struct cred *cred, struct files_struct *files) 647 { 648 struct aa_label *label = aa_get_newest_cred_label(cred); 649 struct file *devnull = NULL; 650 unsigned int n; 651 652 revalidate_tty(label); 653 654 /* Revalidate access to inherited open files. */ 655 n = iterate_fd(files, 0, match_file, label); 656 if (!n) /* none found? */ 657 goto out; 658 659 devnull = dentry_open(&aa_null, O_RDWR, cred); 660 if (IS_ERR(devnull)) 661 devnull = NULL; 662 /* replace all the matching ones with this */ 663 do { 664 replace_fd(n - 1, devnull, 0); 665 } while ((n = iterate_fd(files, n, match_file, label)) != 0); 666 if (devnull) 667 fput(devnull); 668 out: 669 aa_put_label(label); 670 } 671