mac_cred.c revision 151115
1/*- 2 * Copyright (c) 1999-2002 Robert N. M. Watson 3 * Copyright (c) 2001 Ilmar S. Habibulin 4 * Copyright (c) 2001-2003 Networks Associates Technology, Inc. 5 * Copyright (c) 2005 Samy Al Bahra 6 * All rights reserved. 7 * 8 * This software was developed by Robert Watson and Ilmar Habibulin for the 9 * TrustedBSD Project. 10 * 11 * This software was developed for the FreeBSD Project in part by Network 12 * Associates Laboratories, the Security Research Division of Network 13 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), 14 * as part of the DARPA CHATS research program. 15 * 16 * Redistribution and use in source and binary forms, with or without 17 * modification, are permitted provided that the following conditions 18 * are met: 19 * 1. Redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer. 21 * 2. Redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35 * SUCH DAMAGE. 36 */ 37 38#include <sys/cdefs.h> 39__FBSDID("$FreeBSD: head/sys/security/mac/mac_process.c 151115 2005-10-09 02:37:27Z csjp $"); 40 41#include "opt_mac.h" 42 43#include <sys/param.h> 44#include <sys/condvar.h> 45#include <sys/imgact.h> 46#include <sys/kernel.h> 47#include <sys/lock.h> 48#include <sys/malloc.h> 49#include <sys/mutex.h> 50#include <sys/mac.h> 51#include <sys/proc.h> 52#include <sys/sbuf.h> 53#include <sys/systm.h> 54#include <sys/vnode.h> 55#include <sys/mount.h> 56#include <sys/file.h> 57#include <sys/namei.h> 58#include <sys/sysctl.h> 59 60#include <vm/vm.h> 61#include <vm/pmap.h> 62#include <vm/vm_map.h> 63#include <vm/vm_object.h> 64 65#include <sys/mac_policy.h> 66 67#include <security/mac/mac_internal.h> 68 69int mac_enforce_process = 1; 70SYSCTL_INT(_security_mac, OID_AUTO, enforce_process, CTLFLAG_RW, 71 &mac_enforce_process, 0, "Enforce MAC policy on inter-process operations"); 72TUNABLE_INT("security.mac.enforce_process", &mac_enforce_process); 73 74int mac_enforce_vm = 1; 75SYSCTL_INT(_security_mac, OID_AUTO, enforce_vm, CTLFLAG_RW, 76 &mac_enforce_vm, 0, "Enforce MAC policy on vm operations"); 77TUNABLE_INT("security.mac.enforce_vm", &mac_enforce_vm); 78 79static int mac_mmap_revocation = 1; 80SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation, CTLFLAG_RW, 81 &mac_mmap_revocation, 0, "Revoke mmap access to files on subject " 82 "relabel"); 83 84static int mac_mmap_revocation_via_cow = 0; 85SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation_via_cow, CTLFLAG_RW, 86 &mac_mmap_revocation_via_cow, 0, "Revoke mmap access to files via " 87 "copy-on-write semantics, or by removing all write access"); 88 89static int mac_enforce_suid = 1; 90SYSCTL_INT(_security_mac, OID_AUTO, enforce_suid, CTLFLAG_RW, 91 &mac_enforce_suid, 0, "Enforce MAC policy on suid/sgid operations"); 92TUNABLE_INT("security.mac.enforce_suid", &mac_enforce_suid); 93 94#ifdef MAC_DEBUG 95static unsigned int nmaccreds, nmacprocs; 96SYSCTL_UINT(_security_mac_debug_counters, OID_AUTO, creds, CTLFLAG_RD, 97 &nmaccreds, 0, "number of ucreds in use"); 98SYSCTL_UINT(_security_mac_debug_counters, OID_AUTO, procs, CTLFLAG_RD, 99 &nmacprocs, 0, "number of procs in use"); 100#endif 101 102static void mac_cred_mmapped_drop_perms_recurse(struct thread *td, 103 struct ucred *cred, struct vm_map *map); 104 105struct label * 106mac_cred_label_alloc(void) 107{ 108 struct label *label; 109 110 label = mac_labelzone_alloc(M_WAITOK); 111 MAC_PERFORM(init_cred_label, label); 112 MAC_DEBUG_COUNTER_INC(&nmaccreds); 113 return (label); 114} 115 116void 117mac_init_cred(struct ucred *cred) 118{ 119 120 cred->cr_label = mac_cred_label_alloc(); 121} 122 123static struct label * 124mac_proc_label_alloc(void) 125{ 126 struct label *label; 127 128 label = mac_labelzone_alloc(M_WAITOK); 129 MAC_PERFORM(init_proc_label, label); 130 MAC_DEBUG_COUNTER_INC(&nmacprocs); 131 return (label); 132} 133 134void 135mac_init_proc(struct proc *p) 136{ 137 138 p->p_label = mac_proc_label_alloc(); 139} 140 141void 142mac_cred_label_free(struct label *label) 143{ 144 145 MAC_PERFORM(destroy_cred_label, label); 146 mac_labelzone_free(label); 147 MAC_DEBUG_COUNTER_DEC(&nmaccreds); 148} 149 150void 151mac_destroy_cred(struct ucred *cred) 152{ 153 154 mac_cred_label_free(cred->cr_label); 155 cred->cr_label = NULL; 156} 157 158static void 159mac_proc_label_free(struct label *label) 160{ 161 162 MAC_PERFORM(destroy_proc_label, label); 163 mac_labelzone_free(label); 164 MAC_DEBUG_COUNTER_DEC(&nmacprocs); 165} 166 167void 168mac_destroy_proc(struct proc *p) 169{ 170 171 mac_proc_label_free(p->p_label); 172 p->p_label = NULL; 173} 174 175int 176mac_externalize_cred_label(struct label *label, char *elements, 177 char *outbuf, size_t outbuflen) 178{ 179 int error; 180 181 MAC_EXTERNALIZE(cred, label, elements, outbuf, outbuflen); 182 183 return (error); 184} 185 186int 187mac_internalize_cred_label(struct label *label, char *string) 188{ 189 int error; 190 191 MAC_INTERNALIZE(cred, label, string); 192 193 return (error); 194} 195 196/* 197 * Initialize MAC label for the first kernel process, from which other 198 * kernel processes and threads are spawned. 199 */ 200void 201mac_create_proc0(struct ucred *cred) 202{ 203 204 MAC_PERFORM(create_proc0, cred); 205} 206 207/* 208 * Initialize MAC label for the first userland process, from which other 209 * userland processes and threads are spawned. 210 */ 211void 212mac_create_proc1(struct ucred *cred) 213{ 214 215 MAC_PERFORM(create_proc1, cred); 216} 217 218void 219mac_thread_userret(struct thread *td) 220{ 221 222 MAC_PERFORM(thread_userret, td); 223} 224 225/* 226 * When a new process is created, its label must be initialized. Generally, 227 * this involves inheritence from the parent process, modulo possible 228 * deltas. This function allows that processing to take place. 229 */ 230void 231mac_copy_cred(struct ucred *src, struct ucred *dest) 232{ 233 234 MAC_PERFORM(copy_cred_label, src->cr_label, dest->cr_label); 235} 236 237int 238mac_execve_enter(struct image_params *imgp, struct mac *mac_p) 239{ 240 struct label *label; 241 struct mac mac; 242 char *buffer; 243 int error; 244 245 if (mac_p == NULL) 246 return (0); 247 248 error = copyin(mac_p, &mac, sizeof(mac)); 249 if (error) 250 return (error); 251 252 error = mac_check_structmac_consistent(&mac); 253 if (error) 254 return (error); 255 256 buffer = malloc(mac.m_buflen, M_MACTEMP, M_WAITOK); 257 error = copyinstr(mac.m_string, buffer, mac.m_buflen, NULL); 258 if (error) { 259 free(buffer, M_MACTEMP); 260 return (error); 261 } 262 263 label = mac_cred_label_alloc(); 264 error = mac_internalize_cred_label(label, buffer); 265 free(buffer, M_MACTEMP); 266 if (error) { 267 mac_cred_label_free(label); 268 return (error); 269 } 270 imgp->execlabel = label; 271 return (0); 272} 273 274void 275mac_execve_exit(struct image_params *imgp) 276{ 277 if (imgp->execlabel != NULL) { 278 mac_cred_label_free(imgp->execlabel); 279 imgp->execlabel = NULL; 280 } 281} 282 283/* 284 * When relabeling a process, call out to the policies for the maximum 285 * permission allowed for each object type we know about in its 286 * memory space, and revoke access (in the least surprising ways we 287 * know) when necessary. The process lock is not held here. 288 */ 289void 290mac_cred_mmapped_drop_perms(struct thread *td, struct ucred *cred) 291{ 292 293 /* XXX freeze all other threads */ 294 mac_cred_mmapped_drop_perms_recurse(td, cred, 295 &td->td_proc->p_vmspace->vm_map); 296 /* XXX allow other threads to continue */ 297} 298 299static __inline const char * 300prot2str(vm_prot_t prot) 301{ 302 303 switch (prot & VM_PROT_ALL) { 304 case VM_PROT_READ: 305 return ("r--"); 306 case VM_PROT_READ | VM_PROT_WRITE: 307 return ("rw-"); 308 case VM_PROT_READ | VM_PROT_EXECUTE: 309 return ("r-x"); 310 case VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE: 311 return ("rwx"); 312 case VM_PROT_WRITE: 313 return ("-w-"); 314 case VM_PROT_EXECUTE: 315 return ("--x"); 316 case VM_PROT_WRITE | VM_PROT_EXECUTE: 317 return ("-wx"); 318 default: 319 return ("---"); 320 } 321} 322 323static void 324mac_cred_mmapped_drop_perms_recurse(struct thread *td, struct ucred *cred, 325 struct vm_map *map) 326{ 327 struct vm_map_entry *vme; 328 int vfslocked, result; 329 vm_prot_t revokeperms; 330 vm_object_t backing_object, object; 331 vm_ooffset_t offset; 332 struct vnode *vp; 333 334 if (!mac_mmap_revocation) 335 return; 336 337 vm_map_lock_read(map); 338 for (vme = map->header.next; vme != &map->header; vme = vme->next) { 339 if (vme->eflags & MAP_ENTRY_IS_SUB_MAP) { 340 mac_cred_mmapped_drop_perms_recurse(td, cred, 341 vme->object.sub_map); 342 continue; 343 } 344 /* 345 * Skip over entries that obviously are not shared. 346 */ 347 if (vme->eflags & (MAP_ENTRY_COW | MAP_ENTRY_NOSYNC) || 348 !vme->max_protection) 349 continue; 350 /* 351 * Drill down to the deepest backing object. 352 */ 353 offset = vme->offset; 354 object = vme->object.vm_object; 355 if (object == NULL) 356 continue; 357 VM_OBJECT_LOCK(object); 358 while ((backing_object = object->backing_object) != NULL) { 359 VM_OBJECT_LOCK(backing_object); 360 offset += object->backing_object_offset; 361 VM_OBJECT_UNLOCK(object); 362 object = backing_object; 363 } 364 VM_OBJECT_UNLOCK(object); 365 /* 366 * At the moment, vm_maps and objects aren't considered 367 * by the MAC system, so only things with backing by a 368 * normal object (read: vnodes) are checked. 369 */ 370 if (object->type != OBJT_VNODE) 371 continue; 372 vp = (struct vnode *)object->handle; 373 vfslocked = VFS_LOCK_GIANT(vp->v_mount); 374 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td); 375 result = vme->max_protection; 376 mac_check_vnode_mmap_downgrade(cred, vp, &result); 377 VOP_UNLOCK(vp, 0, td); 378 /* 379 * Find out what maximum protection we may be allowing 380 * now but a policy needs to get removed. 381 */ 382 revokeperms = vme->max_protection & ~result; 383 if (!revokeperms) { 384 VFS_UNLOCK_GIANT(vfslocked); 385 continue; 386 } 387 printf("pid %ld: revoking %s perms from %#lx:%ld " 388 "(max %s/cur %s)\n", (long)td->td_proc->p_pid, 389 prot2str(revokeperms), (u_long)vme->start, 390 (long)(vme->end - vme->start), 391 prot2str(vme->max_protection), prot2str(vme->protection)); 392 vm_map_lock_upgrade(map); 393 /* 394 * This is the really simple case: if a map has more 395 * max_protection than is allowed, but it's not being 396 * actually used (that is, the current protection is 397 * still allowed), we can just wipe it out and do 398 * nothing more. 399 */ 400 if ((vme->protection & revokeperms) == 0) { 401 vme->max_protection -= revokeperms; 402 } else { 403 if (revokeperms & VM_PROT_WRITE) { 404 /* 405 * In the more complicated case, flush out all 406 * pending changes to the object then turn it 407 * copy-on-write. 408 */ 409 vm_object_reference(object); 410 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td); 411 VM_OBJECT_LOCK(object); 412 vm_object_page_clean(object, 413 OFF_TO_IDX(offset), 414 OFF_TO_IDX(offset + vme->end - vme->start + 415 PAGE_MASK), 416 OBJPC_SYNC); 417 VM_OBJECT_UNLOCK(object); 418 VOP_UNLOCK(vp, 0, td); 419 vm_object_deallocate(object); 420 /* 421 * Why bother if there's no read permissions 422 * anymore? For the rest, we need to leave 423 * the write permissions on for COW, or 424 * remove them entirely if configured to. 425 */ 426 if (!mac_mmap_revocation_via_cow) { 427 vme->max_protection &= ~VM_PROT_WRITE; 428 vme->protection &= ~VM_PROT_WRITE; 429 } if ((revokeperms & VM_PROT_READ) == 0) 430 vme->eflags |= MAP_ENTRY_COW | 431 MAP_ENTRY_NEEDS_COPY; 432 } 433 if (revokeperms & VM_PROT_EXECUTE) { 434 vme->max_protection &= ~VM_PROT_EXECUTE; 435 vme->protection &= ~VM_PROT_EXECUTE; 436 } 437 if (revokeperms & VM_PROT_READ) { 438 vme->max_protection = 0; 439 vme->protection = 0; 440 } 441 pmap_protect(map->pmap, vme->start, vme->end, 442 vme->protection & ~revokeperms); 443 vm_map_simplify_entry(map, vme); 444 } 445 vm_map_lock_downgrade(map); 446 VFS_UNLOCK_GIANT(vfslocked); 447 } 448 vm_map_unlock_read(map); 449} 450 451/* 452 * When the subject's label changes, it may require revocation of privilege 453 * to mapped objects. This can't be done on-the-fly later with a unified 454 * buffer cache. 455 */ 456void 457mac_relabel_cred(struct ucred *cred, struct label *newlabel) 458{ 459 460 MAC_PERFORM(relabel_cred, cred, newlabel); 461} 462 463int 464mac_check_cred_relabel(struct ucred *cred, struct label *newlabel) 465{ 466 int error; 467 468 MAC_CHECK(check_cred_relabel, cred, newlabel); 469 470 return (error); 471} 472 473int 474mac_check_cred_visible(struct ucred *u1, struct ucred *u2) 475{ 476 int error; 477 478 if (!mac_enforce_process) 479 return (0); 480 481 MAC_CHECK(check_cred_visible, u1, u2); 482 483 return (error); 484} 485 486int 487mac_check_proc_debug(struct ucred *cred, struct proc *proc) 488{ 489 int error; 490 491 PROC_LOCK_ASSERT(proc, MA_OWNED); 492 493 if (!mac_enforce_process) 494 return (0); 495 496 MAC_CHECK(check_proc_debug, cred, proc); 497 498 return (error); 499} 500 501int 502mac_check_proc_sched(struct ucred *cred, struct proc *proc) 503{ 504 int error; 505 506 PROC_LOCK_ASSERT(proc, MA_OWNED); 507 508 if (!mac_enforce_process) 509 return (0); 510 511 MAC_CHECK(check_proc_sched, cred, proc); 512 513 return (error); 514} 515 516int 517mac_check_proc_signal(struct ucred *cred, struct proc *proc, int signum) 518{ 519 int error; 520 521 PROC_LOCK_ASSERT(proc, MA_OWNED); 522 523 if (!mac_enforce_process) 524 return (0); 525 526 MAC_CHECK(check_proc_signal, cred, proc, signum); 527 528 return (error); 529} 530 531int 532mac_check_proc_setuid(struct proc *proc, struct ucred *cred, uid_t uid) 533{ 534 int error; 535 536 PROC_LOCK_ASSERT(proc, MA_OWNED); 537 538 if (!mac_enforce_suid) 539 return (0); 540 541 MAC_CHECK(check_proc_setuid, cred, uid); 542 return (error); 543} 544 545int 546mac_check_proc_seteuid(struct proc *proc, struct ucred *cred, uid_t euid) 547{ 548 int error; 549 550 PROC_LOCK_ASSERT(proc, MA_OWNED); 551 552 if (!mac_enforce_suid) 553 return (0); 554 555 MAC_CHECK(check_proc_seteuid, cred, euid); 556 return (error); 557} 558 559int 560mac_check_proc_setgid(struct proc *proc, struct ucred *cred, gid_t gid) 561{ 562 int error; 563 564 PROC_LOCK_ASSERT(proc, MA_OWNED); 565 566 if (!mac_enforce_suid) 567 return (0); 568 569 MAC_CHECK(check_proc_setgid, cred, gid); 570 return (error); 571} 572 573int 574mac_check_proc_setegid(struct proc *proc, struct ucred *cred, gid_t egid) 575{ 576 int error; 577 578 PROC_LOCK_ASSERT(proc, MA_OWNED); 579 580 if (!mac_enforce_suid) 581 return (0); 582 583 MAC_CHECK(check_proc_setegid, cred, egid); 584 return (error); 585} 586 587int 588mac_check_proc_setgroups(struct proc *proc, struct ucred *cred, 589 int ngroups, gid_t *gidset) 590{ 591 int error; 592 593 PROC_LOCK_ASSERT(proc, MA_OWNED); 594 595 if (!mac_enforce_suid) 596 return (0); 597 598 MAC_CHECK(check_proc_setgroups, cred, ngroups, gidset); 599 return (error); 600} 601 602int 603mac_check_proc_setreuid(struct proc *proc, struct ucred *cred, uid_t ruid, 604 uid_t euid) 605{ 606 int error; 607 608 PROC_LOCK_ASSERT(proc, MA_OWNED); 609 610 if (!mac_enforce_suid) 611 return (0); 612 613 MAC_CHECK(check_proc_setreuid, cred, ruid, euid); 614 return (error); 615} 616 617int 618mac_check_proc_setregid(struct proc *proc, struct ucred *cred, gid_t rgid, 619 gid_t egid) 620{ 621 int error; 622 623 PROC_LOCK_ASSERT(proc, MA_OWNED); 624 625 if (!mac_enforce_suid) 626 return (0); 627 628 MAC_CHECK(check_proc_setregid, cred, rgid, egid); 629 return (error); 630} 631 632int 633mac_check_proc_setresuid(struct proc *proc, struct ucred *cred, uid_t ruid, 634 uid_t euid, uid_t suid) 635{ 636 int error; 637 638 PROC_LOCK_ASSERT(proc, MA_OWNED); 639 640 if (!mac_enforce_suid) 641 return (0); 642 643 MAC_CHECK(check_proc_setresuid, cred, ruid, euid, suid); 644 return (error); 645} 646 647int 648mac_check_proc_setresgid(struct proc *proc, struct ucred *cred, gid_t rgid, 649 gid_t egid, gid_t sgid) 650{ 651 int error; 652 653 PROC_LOCK_ASSERT(proc, MA_OWNED); 654 655 if (!mac_enforce_suid) 656 return (0); 657 658 MAC_CHECK(check_proc_setresgid, cred, rgid, egid, sgid); 659 return (error); 660} 661 662int 663mac_check_proc_wait(struct ucred *cred, struct proc *proc) 664{ 665 int error; 666 667 PROC_LOCK_ASSERT(proc, MA_OWNED); 668 669 if (!mac_enforce_process) 670 return (0); 671 672 MAC_CHECK(check_proc_wait, cred, proc); 673 674 return (error); 675} 676