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 27static 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 */ 44static 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 */ 94int 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/** 148 * is_deleted - test if a file has been completely unlinked 149 * @dentry: dentry of file to test for deletion (NOT NULL) 150 * 151 * Returns: true if deleted else false 152 */ 153static inline bool is_deleted(struct dentry *dentry) 154{ 155 if (d_unlinked(dentry) && d_backing_inode(dentry)->i_nlink == 0) 156 return true; 157 return false; 158} 159 160static int path_name(const char *op, const struct cred *subj_cred, 161 struct aa_label *label, 162 const struct path *path, int flags, char *buffer, 163 const char **name, struct path_cond *cond, u32 request) 164{ 165 struct aa_profile *profile; 166 const char *info = NULL; 167 int error; 168 169 error = aa_path_name(path, flags, buffer, name, &info, 170 labels_profile(label)->disconnected); 171 if (error) { 172 fn_for_each_confined(label, profile, 173 aa_audit_file(subj_cred, 174 profile, &nullperms, op, request, *name, 175 NULL, NULL, cond->uid, info, error)); 176 return error; 177 } 178 179 return 0; 180} 181 182struct aa_perms default_perms = {}; 183/** 184 * aa_lookup_fperms - convert dfa compressed perms to internal perms 185 * @file_rules: the aa_policydb to lookup perms for (NOT NULL) 186 * @state: state in dfa 187 * @cond: conditions to consider (NOT NULL) 188 * 189 * TODO: convert from dfa + state to permission entry 190 * 191 * Returns: a pointer to a file permission set 192 */ 193struct aa_perms *aa_lookup_fperms(struct aa_policydb *file_rules, 194 aa_state_t state, struct path_cond *cond) 195{ 196 unsigned int index = ACCEPT_TABLE(file_rules->dfa)[state]; 197 198 if (!(file_rules->perms)) 199 return &default_perms; 200 201 if (uid_eq(current_fsuid(), cond->uid)) 202 return &(file_rules->perms[index]); 203 204 return &(file_rules->perms[index + 1]); 205} 206 207/** 208 * aa_str_perms - find permission that match @name 209 * @file_rules: the aa_policydb to match against (NOT NULL) 210 * @start: state to start matching in 211 * @name: string to match against dfa (NOT NULL) 212 * @cond: conditions to consider for permission set computation (NOT NULL) 213 * @perms: Returns - the permissions found when matching @name 214 * 215 * Returns: the final state in @dfa when beginning @start and walking @name 216 */ 217aa_state_t aa_str_perms(struct aa_policydb *file_rules, aa_state_t start, 218 const char *name, struct path_cond *cond, 219 struct aa_perms *perms) 220{ 221 aa_state_t state; 222 state = aa_dfa_match(file_rules->dfa, start, name); 223 *perms = *(aa_lookup_fperms(file_rules, state, cond)); 224 225 return state; 226} 227 228static int __aa_path_perm(const char *op, const struct cred *subj_cred, 229 struct aa_profile *profile, const char *name, 230 u32 request, struct path_cond *cond, int flags, 231 struct aa_perms *perms) 232{ 233 struct aa_ruleset *rules = list_first_entry(&profile->rules, 234 typeof(*rules), list); 235 int e = 0; 236 237 if (profile_unconfined(profile)) 238 return 0; 239 aa_str_perms(rules->file, rules->file->start[AA_CLASS_FILE], 240 name, cond, perms); 241 if (request & ~perms->allow) 242 e = -EACCES; 243 return aa_audit_file(subj_cred, 244 profile, perms, op, request, name, NULL, NULL, 245 cond->uid, NULL, e); 246} 247 248 249static int profile_path_perm(const char *op, const struct cred *subj_cred, 250 struct aa_profile *profile, 251 const struct path *path, char *buffer, u32 request, 252 struct path_cond *cond, int flags, 253 struct aa_perms *perms) 254{ 255 const char *name; 256 int error; 257 258 if (profile_unconfined(profile)) 259 return 0; 260 261 error = path_name(op, subj_cred, &profile->label, path, 262 flags | profile->path_flags, buffer, &name, cond, 263 request); 264 if (error) 265 return error; 266 return __aa_path_perm(op, subj_cred, profile, name, request, cond, 267 flags, perms); 268} 269 270/** 271 * aa_path_perm - do permissions check & audit for @path 272 * @op: operation being checked 273 * @subj_cred: subject cred 274 * @label: profile being enforced (NOT NULL) 275 * @path: path to check permissions of (NOT NULL) 276 * @flags: any additional path flags beyond what the profile specifies 277 * @request: requested permissions 278 * @cond: conditional info for this request (NOT NULL) 279 * 280 * Returns: %0 else error if access denied or other error 281 */ 282int aa_path_perm(const char *op, const struct cred *subj_cred, 283 struct aa_label *label, 284 const struct path *path, int flags, u32 request, 285 struct path_cond *cond) 286{ 287 struct aa_perms perms = {}; 288 struct aa_profile *profile; 289 char *buffer = NULL; 290 int error; 291 292 flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR : 293 0); 294 buffer = aa_get_buffer(false); 295 if (!buffer) 296 return -ENOMEM; 297 error = fn_for_each_confined(label, profile, 298 profile_path_perm(op, subj_cred, profile, path, buffer, 299 request, cond, flags, &perms)); 300 301 aa_put_buffer(buffer); 302 303 return error; 304} 305 306/** 307 * xindex_is_subset - helper for aa_path_link 308 * @link: link permission set 309 * @target: target permission set 310 * 311 * test target x permissions are equal OR a subset of link x permissions 312 * this is done as part of the subset test, where a hardlink must have 313 * a subset of permissions that the target has. 314 * 315 * Returns: true if subset else false 316 */ 317static inline bool xindex_is_subset(u32 link, u32 target) 318{ 319 if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) || 320 ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE))) 321 return false; 322 323 return true; 324} 325 326static int profile_path_link(const struct cred *subj_cred, 327 struct aa_profile *profile, 328 const struct path *link, char *buffer, 329 const struct path *target, char *buffer2, 330 struct path_cond *cond) 331{ 332 struct aa_ruleset *rules = list_first_entry(&profile->rules, 333 typeof(*rules), list); 334 const char *lname, *tname = NULL; 335 struct aa_perms lperms = {}, perms; 336 const char *info = NULL; 337 u32 request = AA_MAY_LINK; 338 aa_state_t state; 339 int error; 340 341 error = path_name(OP_LINK, subj_cred, &profile->label, link, 342 profile->path_flags, 343 buffer, &lname, cond, AA_MAY_LINK); 344 if (error) 345 goto audit; 346 347 /* buffer2 freed below, tname is pointer in buffer2 */ 348 error = path_name(OP_LINK, subj_cred, &profile->label, target, 349 profile->path_flags, 350 buffer2, &tname, cond, AA_MAY_LINK); 351 if (error) 352 goto audit; 353 354 error = -EACCES; 355 /* aa_str_perms - handles the case of the dfa being NULL */ 356 state = aa_str_perms(rules->file, 357 rules->file->start[AA_CLASS_FILE], lname, 358 cond, &lperms); 359 360 if (!(lperms.allow & AA_MAY_LINK)) 361 goto audit; 362 363 /* test to see if target can be paired with link */ 364 state = aa_dfa_null_transition(rules->file->dfa, state); 365 aa_str_perms(rules->file, state, tname, cond, &perms); 366 367 /* force audit/quiet masks for link are stored in the second entry 368 * in the link pair. 369 */ 370 lperms.audit = perms.audit; 371 lperms.quiet = perms.quiet; 372 lperms.kill = perms.kill; 373 374 if (!(perms.allow & AA_MAY_LINK)) { 375 info = "target restricted"; 376 lperms = perms; 377 goto audit; 378 } 379 380 /* done if link subset test is not required */ 381 if (!(perms.allow & AA_LINK_SUBSET)) 382 goto done_tests; 383 384 /* Do link perm subset test requiring allowed permission on link are 385 * a subset of the allowed permissions on target. 386 */ 387 aa_str_perms(rules->file, rules->file->start[AA_CLASS_FILE], 388 tname, cond, &perms); 389 390 /* AA_MAY_LINK is not considered in the subset test */ 391 request = lperms.allow & ~AA_MAY_LINK; 392 lperms.allow &= perms.allow | AA_MAY_LINK; 393 394 request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow); 395 if (request & ~lperms.allow) { 396 goto audit; 397 } else if ((lperms.allow & MAY_EXEC) && 398 !xindex_is_subset(lperms.xindex, perms.xindex)) { 399 lperms.allow &= ~MAY_EXEC; 400 request |= MAY_EXEC; 401 info = "link not subset of target"; 402 goto audit; 403 } 404 405done_tests: 406 error = 0; 407 408audit: 409 return aa_audit_file(subj_cred, 410 profile, &lperms, OP_LINK, request, lname, tname, 411 NULL, cond->uid, info, error); 412} 413 414/** 415 * aa_path_link - Handle hard link permission check 416 * @subj_cred: subject cred 417 * @label: the label being enforced (NOT NULL) 418 * @old_dentry: the target dentry (NOT NULL) 419 * @new_dir: directory the new link will be created in (NOT NULL) 420 * @new_dentry: the link being created (NOT NULL) 421 * 422 * Handle the permission test for a link & target pair. Permission 423 * is encoded as a pair where the link permission is determined 424 * first, and if allowed, the target is tested. The target test 425 * is done from the point of the link match (not start of DFA) 426 * making the target permission dependent on the link permission match. 427 * 428 * The subset test if required forces that permissions granted 429 * on link are a subset of the permission granted to target. 430 * 431 * Returns: %0 if allowed else error 432 */ 433int aa_path_link(const struct cred *subj_cred, 434 struct aa_label *label, struct dentry *old_dentry, 435 const struct path *new_dir, struct dentry *new_dentry) 436{ 437 struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry }; 438 struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry }; 439 struct path_cond cond = { 440 d_backing_inode(old_dentry)->i_uid, 441 d_backing_inode(old_dentry)->i_mode 442 }; 443 char *buffer = NULL, *buffer2 = NULL; 444 struct aa_profile *profile; 445 int error; 446 447 /* buffer freed below, lname is pointer in buffer */ 448 buffer = aa_get_buffer(false); 449 buffer2 = aa_get_buffer(false); 450 error = -ENOMEM; 451 if (!buffer || !buffer2) 452 goto out; 453 454 error = fn_for_each_confined(label, profile, 455 profile_path_link(subj_cred, profile, &link, buffer, 456 &target, buffer2, &cond)); 457out: 458 aa_put_buffer(buffer); 459 aa_put_buffer(buffer2); 460 return error; 461} 462 463static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label, 464 u32 request) 465{ 466 struct aa_label *l, *old; 467 468 /* update caching of label on file_ctx */ 469 spin_lock(&fctx->lock); 470 old = rcu_dereference_protected(fctx->label, 471 lockdep_is_held(&fctx->lock)); 472 l = aa_label_merge(old, label, GFP_ATOMIC); 473 if (l) { 474 if (l != old) { 475 rcu_assign_pointer(fctx->label, l); 476 aa_put_label(old); 477 } else 478 aa_put_label(l); 479 fctx->allow |= request; 480 } 481 spin_unlock(&fctx->lock); 482} 483 484static int __file_path_perm(const char *op, const struct cred *subj_cred, 485 struct aa_label *label, 486 struct aa_label *flabel, struct file *file, 487 u32 request, u32 denied, bool in_atomic) 488{ 489 struct aa_profile *profile; 490 struct aa_perms perms = {}; 491 vfsuid_t vfsuid = i_uid_into_vfsuid(file_mnt_idmap(file), 492 file_inode(file)); 493 struct path_cond cond = { 494 .uid = vfsuid_into_kuid(vfsuid), 495 .mode = file_inode(file)->i_mode 496 }; 497 char *buffer; 498 int flags, error; 499 500 /* revalidation due to label out of date. No revocation at this time */ 501 if (!denied && aa_label_is_subset(flabel, label)) 502 /* TODO: check for revocation on stale profiles */ 503 return 0; 504 505 flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0); 506 buffer = aa_get_buffer(in_atomic); 507 if (!buffer) 508 return -ENOMEM; 509 510 /* check every profile in task label not in current cache */ 511 error = fn_for_each_not_in_set(flabel, label, profile, 512 profile_path_perm(op, subj_cred, profile, 513 &file->f_path, buffer, 514 request, &cond, flags, &perms)); 515 if (denied && !error) { 516 /* 517 * check every profile in file label that was not tested 518 * in the initial check above. 519 * 520 * TODO: cache full perms so this only happens because of 521 * conditionals 522 * TODO: don't audit here 523 */ 524 if (label == flabel) 525 error = fn_for_each(label, profile, 526 profile_path_perm(op, subj_cred, 527 profile, &file->f_path, 528 buffer, request, &cond, flags, 529 &perms)); 530 else 531 error = fn_for_each_not_in_set(label, flabel, profile, 532 profile_path_perm(op, subj_cred, 533 profile, &file->f_path, 534 buffer, request, &cond, flags, 535 &perms)); 536 } 537 if (!error) 538 update_file_ctx(file_ctx(file), label, request); 539 540 aa_put_buffer(buffer); 541 542 return error; 543} 544 545static int __file_sock_perm(const char *op, const struct cred *subj_cred, 546 struct aa_label *label, 547 struct aa_label *flabel, struct file *file, 548 u32 request, u32 denied) 549{ 550 struct socket *sock = (struct socket *) file->private_data; 551 int error; 552 553 AA_BUG(!sock); 554 555 /* revalidation due to label out of date. No revocation at this time */ 556 if (!denied && aa_label_is_subset(flabel, label)) 557 return 0; 558 559 /* TODO: improve to skip profiles cached in flabel */ 560 error = aa_sock_file_perm(subj_cred, label, op, request, sock); 561 if (denied) { 562 /* TODO: improve to skip profiles checked above */ 563 /* check every profile in file label to is cached */ 564 last_error(error, aa_sock_file_perm(subj_cred, flabel, op, 565 request, sock)); 566 } 567 if (!error) 568 update_file_ctx(file_ctx(file), label, request); 569 570 return error; 571} 572 573/** 574 * aa_file_perm - do permission revalidation check & audit for @file 575 * @op: operation being checked 576 * @subj_cred: subject cred 577 * @label: label being enforced (NOT NULL) 578 * @file: file to revalidate access permissions on (NOT NULL) 579 * @request: requested permissions 580 * @in_atomic: whether allocations need to be done in atomic context 581 * 582 * Returns: %0 if access allowed else error 583 */ 584int aa_file_perm(const char *op, const struct cred *subj_cred, 585 struct aa_label *label, struct file *file, 586 u32 request, bool in_atomic) 587{ 588 struct aa_file_ctx *fctx; 589 struct aa_label *flabel; 590 u32 denied; 591 int error = 0; 592 593 AA_BUG(!label); 594 AA_BUG(!file); 595 596 fctx = file_ctx(file); 597 598 rcu_read_lock(); 599 flabel = rcu_dereference(fctx->label); 600 AA_BUG(!flabel); 601 602 /* revalidate access, if task is unconfined, or the cached cred 603 * doesn't match or if the request is for more permissions than 604 * was granted. 605 * 606 * Note: the test for !unconfined(flabel) is to handle file 607 * delegation from unconfined tasks 608 */ 609 denied = request & ~fctx->allow; 610 if (unconfined(label) || unconfined(flabel) || 611 (!denied && aa_label_is_subset(flabel, label))) { 612 rcu_read_unlock(); 613 goto done; 614 } 615 616 flabel = aa_get_newest_label(flabel); 617 rcu_read_unlock(); 618 /* TODO: label cross check */ 619 620 if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry)) 621 error = __file_path_perm(op, subj_cred, label, flabel, file, 622 request, denied, in_atomic); 623 624 else if (S_ISSOCK(file_inode(file)->i_mode)) 625 error = __file_sock_perm(op, subj_cred, label, flabel, file, 626 request, denied); 627 aa_put_label(flabel); 628 629done: 630 return error; 631} 632 633static void revalidate_tty(const struct cred *subj_cred, struct aa_label *label) 634{ 635 struct tty_struct *tty; 636 int drop_tty = 0; 637 638 tty = get_current_tty(); 639 if (!tty) 640 return; 641 642 spin_lock(&tty->files_lock); 643 if (!list_empty(&tty->tty_files)) { 644 struct tty_file_private *file_priv; 645 struct file *file; 646 /* TODO: Revalidate access to controlling tty. */ 647 file_priv = list_first_entry(&tty->tty_files, 648 struct tty_file_private, list); 649 file = file_priv->file; 650 651 if (aa_file_perm(OP_INHERIT, subj_cred, label, file, 652 MAY_READ | MAY_WRITE, IN_ATOMIC)) 653 drop_tty = 1; 654 } 655 spin_unlock(&tty->files_lock); 656 tty_kref_put(tty); 657 658 if (drop_tty) 659 no_tty(); 660} 661 662struct cred_label { 663 const struct cred *cred; 664 struct aa_label *label; 665}; 666 667static int match_file(const void *p, struct file *file, unsigned int fd) 668{ 669 struct cred_label *cl = (struct cred_label *)p; 670 671 if (aa_file_perm(OP_INHERIT, cl->cred, cl->label, file, 672 aa_map_file_to_perms(file), IN_ATOMIC)) 673 return fd + 1; 674 return 0; 675} 676 677 678/* based on selinux's flush_unauthorized_files */ 679void aa_inherit_files(const struct cred *cred, struct files_struct *files) 680{ 681 struct aa_label *label = aa_get_newest_cred_label(cred); 682 struct cred_label cl = { 683 .cred = cred, 684 .label = label, 685 }; 686 struct file *devnull = NULL; 687 unsigned int n; 688 689 revalidate_tty(cred, label); 690 691 /* Revalidate access to inherited open files. */ 692 n = iterate_fd(files, 0, match_file, &cl); 693 if (!n) /* none found? */ 694 goto out; 695 696 devnull = dentry_open(&aa_null, O_RDWR, cred); 697 if (IS_ERR(devnull)) 698 devnull = NULL; 699 /* replace all the matching ones with this */ 700 do { 701 replace_fd(n - 1, devnull, 0); 702 } while ((n = iterate_fd(files, n, match_file, &cl)) != 0); 703 if (devnull) 704 fput(devnull); 705out: 706 aa_put_label(label); 707} 708