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, 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 unsigned int 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 unsigned int aa_str_perms(struct aa_policydb *file_rules, unsigned int start, 213 const char *name, struct path_cond *cond, 214 struct aa_perms *perms) 215 { 216 unsigned int 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 int e = 0; 228 229 if (profile_unconfined(profile)) 230 return 0; 231 aa_str_perms(&(profile->file), profile->file.start[AA_CLASS_FILE], 232 name, cond, perms); 233 if (request & ~perms->allow) 234 e = -EACCES; 235 return aa_audit_file(profile, perms, op, request, name, NULL, NULL, 236 cond->uid, NULL, e); 237 } 238 239 240 static int profile_path_perm(const char *op, struct aa_profile *profile, 241 const struct path *path, char *buffer, u32 request, 242 struct path_cond *cond, int flags, 243 struct aa_perms *perms) 244 { 245 const char *name; 246 int error; 247 248 if (profile_unconfined(profile)) 249 return 0; 250 251 error = path_name(op, &profile->label, path, 252 flags | profile->path_flags, buffer, &name, cond, 253 request); 254 if (error) 255 return error; 256 return __aa_path_perm(op, profile, name, request, cond, flags, 257 perms); 258 } 259 260 /** 261 * aa_path_perm - do permissions check & audit for @path 262 * @op: operation being checked 263 * @label: profile being enforced (NOT NULL) 264 * @path: path to check permissions of (NOT NULL) 265 * @flags: any additional path flags beyond what the profile specifies 266 * @request: requested permissions 267 * @cond: conditional info for this request (NOT NULL) 268 * 269 * Returns: %0 else error if access denied or other error 270 */ 271 int aa_path_perm(const char *op, struct aa_label *label, 272 const struct path *path, int flags, u32 request, 273 struct path_cond *cond) 274 { 275 struct aa_perms perms = {}; 276 struct aa_profile *profile; 277 char *buffer = NULL; 278 int error; 279 280 flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 281 0); 282 buffer = aa_get_buffer(false); 283 if (!buffer) 284 return -ENOMEM; 285 error = fn_for_each_confined(label, profile, 286 profile_path_perm(op, profile, path, buffer, request, 287 cond, flags, &perms)); 288 289 aa_put_buffer(buffer); 290 291 return error; 292 } 293 294 /** 295 * xindex_is_subset - helper for aa_path_link 296 * @link: link permission set 297 * @target: target permission set 298 * 299 * test target x permissions are equal OR a subset of link x permissions 300 * this is done as part of the subset test, where a hardlink must have 301 * a subset of permissions that the target has. 302 * 303 * Returns: true if subset else false 304 */ 305 static inline bool xindex_is_subset(u32 link, u32 target) 306 { 307 if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) || 308 ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE))) 309 return false; 310 311 return true; 312 } 313 314 static int profile_path_link(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 const char *lname, *tname = NULL; 320 struct aa_perms lperms = {}, perms; 321 const char *info = NULL; 322 u32 request = AA_MAY_LINK; 323 unsigned int state; 324 int error; 325 326 error = path_name(OP_LINK, &profile->label, link, profile->path_flags, 327 buffer, &lname, cond, AA_MAY_LINK); 328 if (error) 329 goto audit; 330 331 /* buffer2 freed below, tname is pointer in buffer2 */ 332 error = path_name(OP_LINK, &profile->label, target, profile->path_flags, 333 buffer2, &tname, cond, AA_MAY_LINK); 334 if (error) 335 goto audit; 336 337 error = -EACCES; 338 /* aa_str_perms - handles the case of the dfa being NULL */ 339 state = aa_str_perms(&(profile->file), 340 profile->file.start[AA_CLASS_FILE], lname, 341 cond, &lperms); 342 343 if (!(lperms.allow & AA_MAY_LINK)) 344 goto audit; 345 346 /* test to see if target can be paired with link */ 347 state = aa_dfa_null_transition(profile->file.dfa, state); 348 aa_str_perms(&(profile->file), state, tname, cond, &perms); 349 350 /* force audit/quiet masks for link are stored in the second entry 351 * in the link pair. 352 */ 353 lperms.audit = perms.audit; 354 lperms.quiet = perms.quiet; 355 lperms.kill = perms.kill; 356 357 if (!(perms.allow & AA_MAY_LINK)) { 358 info = "target restricted"; 359 lperms = perms; 360 goto audit; 361 } 362 363 /* done if link subset test is not required */ 364 if (!(perms.allow & AA_LINK_SUBSET)) 365 goto done_tests; 366 367 /* Do link perm subset test requiring allowed permission on link are 368 * a subset of the allowed permissions on target. 369 */ 370 aa_str_perms(&(profile->file), profile->file.start[AA_CLASS_FILE], 371 tname, cond, &perms); 372 373 /* AA_MAY_LINK is not considered in the subset test */ 374 request = lperms.allow & ~AA_MAY_LINK; 375 lperms.allow &= perms.allow | AA_MAY_LINK; 376 377 request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow); 378 if (request & ~lperms.allow) { 379 goto audit; 380 } else if ((lperms.allow & MAY_EXEC) && 381 !xindex_is_subset(lperms.xindex, perms.xindex)) { 382 lperms.allow &= ~MAY_EXEC; 383 request |= MAY_EXEC; 384 info = "link not subset of target"; 385 goto audit; 386 } 387 388 done_tests: 389 error = 0; 390 391 audit: 392 return aa_audit_file(profile, &lperms, OP_LINK, request, lname, tname, 393 NULL, cond->uid, info, error); 394 } 395 396 /** 397 * aa_path_link - Handle hard link permission check 398 * @label: the label being enforced (NOT NULL) 399 * @old_dentry: the target dentry (NOT NULL) 400 * @new_dir: directory the new link will be created in (NOT NULL) 401 * @new_dentry: the link being created (NOT NULL) 402 * 403 * Handle the permission test for a link & target pair. Permission 404 * is encoded as a pair where the link permission is determined 405 * first, and if allowed, the target is tested. The target test 406 * is done from the point of the link match (not start of DFA) 407 * making the target permission dependent on the link permission match. 408 * 409 * The subset test if required forces that permissions granted 410 * on link are a subset of the permission granted to target. 411 * 412 * Returns: %0 if allowed else error 413 */ 414 int aa_path_link(struct aa_label *label, struct dentry *old_dentry, 415 const struct path *new_dir, struct dentry *new_dentry) 416 { 417 struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry }; 418 struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry }; 419 struct path_cond cond = { 420 d_backing_inode(old_dentry)->i_uid, 421 d_backing_inode(old_dentry)->i_mode 422 }; 423 char *buffer = NULL, *buffer2 = NULL; 424 struct aa_profile *profile; 425 int error; 426 427 /* buffer freed below, lname is pointer in buffer */ 428 buffer = aa_get_buffer(false); 429 buffer2 = aa_get_buffer(false); 430 error = -ENOMEM; 431 if (!buffer || !buffer2) 432 goto out; 433 434 error = fn_for_each_confined(label, profile, 435 profile_path_link(profile, &link, buffer, &target, 436 buffer2, &cond)); 437 out: 438 aa_put_buffer(buffer); 439 aa_put_buffer(buffer2); 440 return error; 441 } 442 443 static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label, 444 u32 request) 445 { 446 struct aa_label *l, *old; 447 448 /* update caching of label on file_ctx */ 449 spin_lock(&fctx->lock); 450 old = rcu_dereference_protected(fctx->label, 451 lockdep_is_held(&fctx->lock)); 452 l = aa_label_merge(old, label, GFP_ATOMIC); 453 if (l) { 454 if (l != old) { 455 rcu_assign_pointer(fctx->label, l); 456 aa_put_label(old); 457 } else 458 aa_put_label(l); 459 fctx->allow |= request; 460 } 461 spin_unlock(&fctx->lock); 462 } 463 464 static int __file_path_perm(const char *op, struct aa_label *label, 465 struct aa_label *flabel, struct file *file, 466 u32 request, u32 denied, bool in_atomic) 467 { 468 struct aa_profile *profile; 469 struct aa_perms perms = {}; 470 struct path_cond cond = { 471 .uid = i_uid_into_mnt(file_mnt_user_ns(file), file_inode(file)), 472 .mode = file_inode(file)->i_mode 473 }; 474 char *buffer; 475 int flags, error; 476 477 /* revalidation due to label out of date. No revocation at this time */ 478 if (!denied && aa_label_is_subset(flabel, label)) 479 /* TODO: check for revocation on stale profiles */ 480 return 0; 481 482 flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0); 483 buffer = aa_get_buffer(in_atomic); 484 if (!buffer) 485 return -ENOMEM; 486 487 /* check every profile in task label not in current cache */ 488 error = fn_for_each_not_in_set(flabel, label, profile, 489 profile_path_perm(op, profile, &file->f_path, buffer, 490 request, &cond, flags, &perms)); 491 if (denied && !error) { 492 /* 493 * check every profile in file label that was not tested 494 * in the initial check above. 495 * 496 * TODO: cache full perms so this only happens because of 497 * conditionals 498 * TODO: don't audit here 499 */ 500 if (label == flabel) 501 error = fn_for_each(label, profile, 502 profile_path_perm(op, profile, &file->f_path, 503 buffer, request, &cond, flags, 504 &perms)); 505 else 506 error = fn_for_each_not_in_set(label, flabel, profile, 507 profile_path_perm(op, profile, &file->f_path, 508 buffer, request, &cond, flags, 509 &perms)); 510 } 511 if (!error) 512 update_file_ctx(file_ctx(file), label, request); 513 514 aa_put_buffer(buffer); 515 516 return error; 517 } 518 519 static int __file_sock_perm(const char *op, struct aa_label *label, 520 struct aa_label *flabel, struct file *file, 521 u32 request, u32 denied) 522 { 523 struct socket *sock = (struct socket *) file->private_data; 524 int error; 525 526 AA_BUG(!sock); 527 528 /* revalidation due to label out of date. No revocation at this time */ 529 if (!denied && aa_label_is_subset(flabel, label)) 530 return 0; 531 532 /* TODO: improve to skip profiles cached in flabel */ 533 error = aa_sock_file_perm(label, op, request, sock); 534 if (denied) { 535 /* TODO: improve to skip profiles checked above */ 536 /* check every profile in file label to is cached */ 537 last_error(error, aa_sock_file_perm(flabel, op, request, sock)); 538 } 539 if (!error) 540 update_file_ctx(file_ctx(file), label, request); 541 542 return error; 543 } 544 545 /** 546 * aa_file_perm - do permission revalidation check & audit for @file 547 * @op: operation being checked 548 * @label: label being enforced (NOT NULL) 549 * @file: file to revalidate access permissions on (NOT NULL) 550 * @request: requested permissions 551 * @in_atomic: whether allocations need to be done in atomic context 552 * 553 * Returns: %0 if access allowed else error 554 */ 555 int aa_file_perm(const char *op, struct aa_label *label, struct file *file, 556 u32 request, bool in_atomic) 557 { 558 struct aa_file_ctx *fctx; 559 struct aa_label *flabel; 560 u32 denied; 561 int error = 0; 562 563 AA_BUG(!label); 564 AA_BUG(!file); 565 566 fctx = file_ctx(file); 567 568 rcu_read_lock(); 569 flabel = rcu_dereference(fctx->label); 570 AA_BUG(!flabel); 571 572 /* revalidate access, if task is unconfined, or the cached cred 573 * doesn't match or if the request is for more permissions than 574 * was granted. 575 * 576 * Note: the test for !unconfined(flabel) is to handle file 577 * delegation from unconfined tasks 578 */ 579 denied = request & ~fctx->allow; 580 if (unconfined(label) || unconfined(flabel) || 581 (!denied && aa_label_is_subset(flabel, label))) { 582 rcu_read_unlock(); 583 goto done; 584 } 585 586 flabel = aa_get_newest_label(flabel); 587 rcu_read_unlock(); 588 /* TODO: label cross check */ 589 590 if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry)) 591 error = __file_path_perm(op, label, flabel, file, request, 592 denied, in_atomic); 593 594 else if (S_ISSOCK(file_inode(file)->i_mode)) 595 error = __file_sock_perm(op, label, flabel, file, request, 596 denied); 597 aa_put_label(flabel); 598 599 done: 600 return error; 601 } 602 603 static void revalidate_tty(struct aa_label *label) 604 { 605 struct tty_struct *tty; 606 int drop_tty = 0; 607 608 tty = get_current_tty(); 609 if (!tty) 610 return; 611 612 spin_lock(&tty->files_lock); 613 if (!list_empty(&tty->tty_files)) { 614 struct tty_file_private *file_priv; 615 struct file *file; 616 /* TODO: Revalidate access to controlling tty. */ 617 file_priv = list_first_entry(&tty->tty_files, 618 struct tty_file_private, list); 619 file = file_priv->file; 620 621 if (aa_file_perm(OP_INHERIT, label, file, MAY_READ | MAY_WRITE, 622 IN_ATOMIC)) 623 drop_tty = 1; 624 } 625 spin_unlock(&tty->files_lock); 626 tty_kref_put(tty); 627 628 if (drop_tty) 629 no_tty(); 630 } 631 632 static int match_file(const void *p, struct file *file, unsigned int fd) 633 { 634 struct aa_label *label = (struct aa_label *)p; 635 636 if (aa_file_perm(OP_INHERIT, label, file, aa_map_file_to_perms(file), 637 IN_ATOMIC)) 638 return fd + 1; 639 return 0; 640 } 641 642 643 /* based on selinux's flush_unauthorized_files */ 644 void aa_inherit_files(const struct cred *cred, struct files_struct *files) 645 { 646 struct aa_label *label = aa_get_newest_cred_label(cred); 647 struct file *devnull = NULL; 648 unsigned int n; 649 650 revalidate_tty(label); 651 652 /* Revalidate access to inherited open files. */ 653 n = iterate_fd(files, 0, match_file, label); 654 if (!n) /* none found? */ 655 goto out; 656 657 devnull = dentry_open(&aa_null, O_RDWR, cred); 658 if (IS_ERR(devnull)) 659 devnull = NULL; 660 /* replace all the matching ones with this */ 661 do { 662 replace_fd(n - 1, devnull, 0); 663 } while ((n = iterate_fd(files, n, match_file, label)) != 0); 664 if (devnull) 665 fput(devnull); 666 out: 667 aa_put_label(label); 668 } 669