xref: /freebsd/sys/security/mac/mac_process.c (revision 91c878a6935c5c2e99866eb267e5bc3028bf6d2f)
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("$FreeBSD$");
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_framework.h>
68 #include <security/mac/mac_internal.h>
69 
70 int	mac_enforce_process = 1;
71 SYSCTL_INT(_security_mac, OID_AUTO, enforce_process, CTLFLAG_RW,
72     &mac_enforce_process, 0, "Enforce MAC policy on inter-process operations");
73 TUNABLE_INT("security.mac.enforce_process", &mac_enforce_process);
74 
75 int	mac_enforce_vm = 1;
76 SYSCTL_INT(_security_mac, OID_AUTO, enforce_vm, CTLFLAG_RW,
77     &mac_enforce_vm, 0, "Enforce MAC policy on vm operations");
78 TUNABLE_INT("security.mac.enforce_vm", &mac_enforce_vm);
79 
80 static int	mac_mmap_revocation = 1;
81 SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation, CTLFLAG_RW,
82     &mac_mmap_revocation, 0, "Revoke mmap access to files on subject "
83     "relabel");
84 
85 static int	mac_mmap_revocation_via_cow = 0;
86 SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation_via_cow, CTLFLAG_RW,
87     &mac_mmap_revocation_via_cow, 0, "Revoke mmap access to files via "
88     "copy-on-write semantics, or by removing all write access");
89 
90 static int	mac_enforce_suid = 1;
91 SYSCTL_INT(_security_mac, OID_AUTO, enforce_suid, CTLFLAG_RW,
92     &mac_enforce_suid, 0, "Enforce MAC policy on suid/sgid operations");
93 TUNABLE_INT("security.mac.enforce_suid", &mac_enforce_suid);
94 
95 static void	mac_cred_mmapped_drop_perms_recurse(struct thread *td,
96 		    struct ucred *cred, struct vm_map *map);
97 
98 struct label *
99 mac_cred_label_alloc(void)
100 {
101 	struct label *label;
102 
103 	label = mac_labelzone_alloc(M_WAITOK);
104 	MAC_PERFORM(init_cred_label, label);
105 	return (label);
106 }
107 
108 void
109 mac_init_cred(struct ucred *cred)
110 {
111 
112 	cred->cr_label = mac_cred_label_alloc();
113 }
114 
115 static struct label *
116 mac_proc_label_alloc(void)
117 {
118 	struct label *label;
119 
120 	label = mac_labelzone_alloc(M_WAITOK);
121 	MAC_PERFORM(init_proc_label, label);
122 	return (label);
123 }
124 
125 void
126 mac_init_proc(struct proc *p)
127 {
128 
129 	p->p_label = mac_proc_label_alloc();
130 }
131 
132 void
133 mac_cred_label_free(struct label *label)
134 {
135 
136 	MAC_PERFORM(destroy_cred_label, label);
137 	mac_labelzone_free(label);
138 }
139 
140 void
141 mac_destroy_cred(struct ucred *cred)
142 {
143 
144 	mac_cred_label_free(cred->cr_label);
145 	cred->cr_label = NULL;
146 }
147 
148 static void
149 mac_proc_label_free(struct label *label)
150 {
151 
152 	MAC_PERFORM(destroy_proc_label, label);
153 	mac_labelzone_free(label);
154 }
155 
156 void
157 mac_destroy_proc(struct proc *p)
158 {
159 
160 	mac_proc_label_free(p->p_label);
161 	p->p_label = NULL;
162 }
163 
164 int
165 mac_externalize_cred_label(struct label *label, char *elements,
166     char *outbuf, size_t outbuflen)
167 {
168 	int error;
169 
170 	MAC_EXTERNALIZE(cred, label, elements, outbuf, outbuflen);
171 
172 	return (error);
173 }
174 
175 int
176 mac_internalize_cred_label(struct label *label, char *string)
177 {
178 	int error;
179 
180 	MAC_INTERNALIZE(cred, label, string);
181 
182 	return (error);
183 }
184 
185 /*
186  * Initialize MAC label for the first kernel process, from which other
187  * kernel processes and threads are spawned.
188  */
189 void
190 mac_create_proc0(struct ucred *cred)
191 {
192 
193 	MAC_PERFORM(create_proc0, cred);
194 }
195 
196 /*
197  * Initialize MAC label for the first userland process, from which other
198  * userland processes and threads are spawned.
199  */
200 void
201 mac_create_proc1(struct ucred *cred)
202 {
203 
204 	MAC_PERFORM(create_proc1, cred);
205 }
206 
207 void
208 mac_thread_userret(struct thread *td)
209 {
210 
211 	MAC_PERFORM(thread_userret, td);
212 }
213 
214 /*
215  * When a new process is created, its label must be initialized.  Generally,
216  * this involves inheritence from the parent process, modulo possible
217  * deltas.  This function allows that processing to take place.
218  */
219 void
220 mac_copy_cred(struct ucred *src, struct ucred *dest)
221 {
222 
223 	MAC_PERFORM(copy_cred_label, src->cr_label, dest->cr_label);
224 }
225 
226 int
227 mac_execve_enter(struct image_params *imgp, struct mac *mac_p)
228 {
229 	struct label *label;
230 	struct mac mac;
231 	char *buffer;
232 	int error;
233 
234 	if (mac_p == NULL)
235 		return (0);
236 
237 	error = copyin(mac_p, &mac, sizeof(mac));
238 	if (error)
239 		return (error);
240 
241 	error = mac_check_structmac_consistent(&mac);
242 	if (error)
243 		return (error);
244 
245 	buffer = malloc(mac.m_buflen, M_MACTEMP, M_WAITOK);
246 	error = copyinstr(mac.m_string, buffer, mac.m_buflen, NULL);
247 	if (error) {
248 		free(buffer, M_MACTEMP);
249 		return (error);
250 	}
251 
252 	label = mac_cred_label_alloc();
253 	error = mac_internalize_cred_label(label, buffer);
254 	free(buffer, M_MACTEMP);
255 	if (error) {
256 		mac_cred_label_free(label);
257 		return (error);
258 	}
259 	imgp->execlabel = label;
260 	return (0);
261 }
262 
263 void
264 mac_execve_exit(struct image_params *imgp)
265 {
266 	if (imgp->execlabel != NULL) {
267 		mac_cred_label_free(imgp->execlabel);
268 		imgp->execlabel = NULL;
269 	}
270 }
271 
272 /*
273  * When relabeling a process, call out to the policies for the maximum
274  * permission allowed for each object type we know about in its
275  * memory space, and revoke access (in the least surprising ways we
276  * know) when necessary.  The process lock is not held here.
277  */
278 void
279 mac_cred_mmapped_drop_perms(struct thread *td, struct ucred *cred)
280 {
281 
282 	/* XXX freeze all other threads */
283 	mac_cred_mmapped_drop_perms_recurse(td, cred,
284 	    &td->td_proc->p_vmspace->vm_map);
285 	/* XXX allow other threads to continue */
286 }
287 
288 static __inline const char *
289 prot2str(vm_prot_t prot)
290 {
291 
292 	switch (prot & VM_PROT_ALL) {
293 	case VM_PROT_READ:
294 		return ("r--");
295 	case VM_PROT_READ | VM_PROT_WRITE:
296 		return ("rw-");
297 	case VM_PROT_READ | VM_PROT_EXECUTE:
298 		return ("r-x");
299 	case VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE:
300 		return ("rwx");
301 	case VM_PROT_WRITE:
302 		return ("-w-");
303 	case VM_PROT_EXECUTE:
304 		return ("--x");
305 	case VM_PROT_WRITE | VM_PROT_EXECUTE:
306 		return ("-wx");
307 	default:
308 		return ("---");
309 	}
310 }
311 
312 static void
313 mac_cred_mmapped_drop_perms_recurse(struct thread *td, struct ucred *cred,
314     struct vm_map *map)
315 {
316 	struct vm_map_entry *vme;
317 	int vfslocked, result;
318 	vm_prot_t revokeperms;
319 	vm_object_t backing_object, object;
320 	vm_ooffset_t offset;
321 	struct vnode *vp;
322 	struct mount *mp;
323 
324 	if (!mac_mmap_revocation)
325 		return;
326 
327 	vm_map_lock_read(map);
328 	for (vme = map->header.next; vme != &map->header; vme = vme->next) {
329 		if (vme->eflags & MAP_ENTRY_IS_SUB_MAP) {
330 			mac_cred_mmapped_drop_perms_recurse(td, cred,
331 			    vme->object.sub_map);
332 			continue;
333 		}
334 		/*
335 		 * Skip over entries that obviously are not shared.
336 		 */
337 		if (vme->eflags & (MAP_ENTRY_COW | MAP_ENTRY_NOSYNC) ||
338 		    !vme->max_protection)
339 			continue;
340 		/*
341 		 * Drill down to the deepest backing object.
342 		 */
343 		offset = vme->offset;
344 		object = vme->object.vm_object;
345 		if (object == NULL)
346 			continue;
347 		VM_OBJECT_LOCK(object);
348 		while ((backing_object = object->backing_object) != NULL) {
349 			VM_OBJECT_LOCK(backing_object);
350 			offset += object->backing_object_offset;
351 			VM_OBJECT_UNLOCK(object);
352 			object = backing_object;
353 		}
354 		VM_OBJECT_UNLOCK(object);
355 		/*
356 		 * At the moment, vm_maps and objects aren't considered
357 		 * by the MAC system, so only things with backing by a
358 		 * normal object (read: vnodes) are checked.
359 		 */
360 		if (object->type != OBJT_VNODE)
361 			continue;
362 		vp = (struct vnode *)object->handle;
363 		vfslocked = VFS_LOCK_GIANT(vp->v_mount);
364 		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
365 		result = vme->max_protection;
366 		mac_check_vnode_mmap_downgrade(cred, vp, &result);
367 		VOP_UNLOCK(vp, 0, td);
368 		/*
369 		 * Find out what maximum protection we may be allowing
370 		 * now but a policy needs to get removed.
371 		 */
372 		revokeperms = vme->max_protection & ~result;
373 		if (!revokeperms) {
374 			VFS_UNLOCK_GIANT(vfslocked);
375 			continue;
376 		}
377 		printf("pid %ld: revoking %s perms from %#lx:%ld "
378 		    "(max %s/cur %s)\n", (long)td->td_proc->p_pid,
379 		    prot2str(revokeperms), (u_long)vme->start,
380 		    (long)(vme->end - vme->start),
381 		    prot2str(vme->max_protection), prot2str(vme->protection));
382 		vm_map_lock_upgrade(map);
383 		/*
384 		 * This is the really simple case: if a map has more
385 		 * max_protection than is allowed, but it's not being
386 		 * actually used (that is, the current protection is
387 		 * still allowed), we can just wipe it out and do
388 		 * nothing more.
389 		 */
390 		if ((vme->protection & revokeperms) == 0) {
391 			vme->max_protection -= revokeperms;
392 		} else {
393 			if (revokeperms & VM_PROT_WRITE) {
394 				/*
395 				 * In the more complicated case, flush out all
396 				 * pending changes to the object then turn it
397 				 * copy-on-write.
398 				 */
399 				vm_object_reference(object);
400 				(void) vn_start_write(vp, &mp, V_WAIT);
401 				vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
402 				VM_OBJECT_LOCK(object);
403 				vm_object_page_clean(object,
404 				    OFF_TO_IDX(offset),
405 				    OFF_TO_IDX(offset + vme->end - vme->start +
406 					PAGE_MASK),
407 				    OBJPC_SYNC);
408 				VM_OBJECT_UNLOCK(object);
409 				VOP_UNLOCK(vp, 0, td);
410 				vn_finished_write(mp);
411 				vm_object_deallocate(object);
412 				/*
413 				 * Why bother if there's no read permissions
414 				 * anymore?  For the rest, we need to leave
415 				 * the write permissions on for COW, or
416 				 * remove them entirely if configured to.
417 				 */
418 				if (!mac_mmap_revocation_via_cow) {
419 					vme->max_protection &= ~VM_PROT_WRITE;
420 					vme->protection &= ~VM_PROT_WRITE;
421 				} if ((revokeperms & VM_PROT_READ) == 0)
422 					vme->eflags |= MAP_ENTRY_COW |
423 					    MAP_ENTRY_NEEDS_COPY;
424 			}
425 			if (revokeperms & VM_PROT_EXECUTE) {
426 				vme->max_protection &= ~VM_PROT_EXECUTE;
427 				vme->protection &= ~VM_PROT_EXECUTE;
428 			}
429 			if (revokeperms & VM_PROT_READ) {
430 				vme->max_protection = 0;
431 				vme->protection = 0;
432 			}
433 			pmap_protect(map->pmap, vme->start, vme->end,
434 			    vme->protection & ~revokeperms);
435 			vm_map_simplify_entry(map, vme);
436 		}
437 		vm_map_lock_downgrade(map);
438 		VFS_UNLOCK_GIANT(vfslocked);
439 	}
440 	vm_map_unlock_read(map);
441 }
442 
443 /*
444  * When the subject's label changes, it may require revocation of privilege
445  * to mapped objects.  This can't be done on-the-fly later with a unified
446  * buffer cache.
447  */
448 void
449 mac_relabel_cred(struct ucred *cred, struct label *newlabel)
450 {
451 
452 	MAC_PERFORM(relabel_cred, cred, newlabel);
453 }
454 
455 int
456 mac_check_cred_relabel(struct ucred *cred, struct label *newlabel)
457 {
458 	int error;
459 
460 	MAC_CHECK(check_cred_relabel, cred, newlabel);
461 
462 	return (error);
463 }
464 
465 int
466 mac_check_cred_visible(struct ucred *u1, struct ucred *u2)
467 {
468 	int error;
469 
470 	if (!mac_enforce_process)
471 		return (0);
472 
473 	MAC_CHECK(check_cred_visible, u1, u2);
474 
475 	return (error);
476 }
477 
478 int
479 mac_check_proc_debug(struct ucred *cred, struct proc *proc)
480 {
481 	int error;
482 
483 	PROC_LOCK_ASSERT(proc, MA_OWNED);
484 
485 	if (!mac_enforce_process)
486 		return (0);
487 
488 	MAC_CHECK(check_proc_debug, cred, proc);
489 
490 	return (error);
491 }
492 
493 int
494 mac_check_proc_sched(struct ucred *cred, struct proc *proc)
495 {
496 	int error;
497 
498 	PROC_LOCK_ASSERT(proc, MA_OWNED);
499 
500 	if (!mac_enforce_process)
501 		return (0);
502 
503 	MAC_CHECK(check_proc_sched, cred, proc);
504 
505 	return (error);
506 }
507 
508 int
509 mac_check_proc_signal(struct ucred *cred, struct proc *proc, int signum)
510 {
511 	int error;
512 
513 	PROC_LOCK_ASSERT(proc, MA_OWNED);
514 
515 	if (!mac_enforce_process)
516 		return (0);
517 
518 	MAC_CHECK(check_proc_signal, cred, proc, signum);
519 
520 	return (error);
521 }
522 
523 int
524 mac_check_proc_setuid(struct proc *proc, struct ucred *cred, uid_t uid)
525 {
526 	int error;
527 
528 	PROC_LOCK_ASSERT(proc, MA_OWNED);
529 
530 	if (!mac_enforce_suid)
531 		return (0);
532 
533 	MAC_CHECK(check_proc_setuid, cred, uid);
534 	return (error);
535 }
536 
537 int
538 mac_check_proc_seteuid(struct proc *proc, struct ucred *cred, uid_t euid)
539 {
540 	int error;
541 
542 	PROC_LOCK_ASSERT(proc, MA_OWNED);
543 
544 	if (!mac_enforce_suid)
545 		return (0);
546 
547 	MAC_CHECK(check_proc_seteuid, cred, euid);
548 	return (error);
549 }
550 
551 int
552 mac_check_proc_setgid(struct proc *proc, struct ucred *cred, gid_t gid)
553 {
554 	int error;
555 
556 	PROC_LOCK_ASSERT(proc, MA_OWNED);
557 
558 	if (!mac_enforce_suid)
559 		return (0);
560 
561 	MAC_CHECK(check_proc_setgid, cred, gid);
562 	return (error);
563 }
564 
565 int
566 mac_check_proc_setegid(struct proc *proc, struct ucred *cred, gid_t egid)
567 {
568 	int error;
569 
570 	PROC_LOCK_ASSERT(proc, MA_OWNED);
571 
572 	if (!mac_enforce_suid)
573 		return (0);
574 
575 	MAC_CHECK(check_proc_setegid, cred, egid);
576 	return (error);
577 }
578 
579 int
580 mac_check_proc_setgroups(struct proc *proc, struct ucred *cred,
581 	int ngroups, gid_t *gidset)
582 {
583 	int error;
584 
585 	PROC_LOCK_ASSERT(proc, MA_OWNED);
586 
587 	if (!mac_enforce_suid)
588 		return (0);
589 
590 	MAC_CHECK(check_proc_setgroups, cred, ngroups, gidset);
591 	return (error);
592 }
593 
594 int
595 mac_check_proc_setreuid(struct proc *proc, struct ucred *cred, uid_t ruid,
596 	uid_t euid)
597 {
598 	int error;
599 
600 	PROC_LOCK_ASSERT(proc, MA_OWNED);
601 
602 	if (!mac_enforce_suid)
603 		return (0);
604 
605 	MAC_CHECK(check_proc_setreuid, cred, ruid, euid);
606 	return (error);
607 }
608 
609 int
610 mac_check_proc_setregid(struct proc *proc, struct ucred *cred, gid_t rgid,
611 	gid_t egid)
612 {
613 	int error;
614 
615 	PROC_LOCK_ASSERT(proc, MA_OWNED);
616 
617 	if (!mac_enforce_suid)
618 		return (0);
619 
620 	MAC_CHECK(check_proc_setregid, cred, rgid, egid);
621 	return (error);
622 }
623 
624 int
625 mac_check_proc_setresuid(struct proc *proc, struct ucred *cred, uid_t ruid,
626 	uid_t euid, uid_t suid)
627 {
628 	int error;
629 
630 	PROC_LOCK_ASSERT(proc, MA_OWNED);
631 
632 	if (!mac_enforce_suid)
633 		return (0);
634 
635 	MAC_CHECK(check_proc_setresuid, cred, ruid, euid, suid);
636 	return (error);
637 }
638 
639 int
640 mac_check_proc_setresgid(struct proc *proc, struct ucred *cred, gid_t rgid,
641 	gid_t egid, gid_t sgid)
642 {
643 	int error;
644 
645 	PROC_LOCK_ASSERT(proc, MA_OWNED);
646 
647 	if (!mac_enforce_suid)
648 		return (0);
649 
650 	MAC_CHECK(check_proc_setresgid, cred, rgid, egid, sgid);
651 	return (error);
652 }
653 
654 int
655 mac_check_proc_wait(struct ucred *cred, struct proc *proc)
656 {
657 	int error;
658 
659 	PROC_LOCK_ASSERT(proc, MA_OWNED);
660 
661 	if (!mac_enforce_process)
662 		return (0);
663 
664 	MAC_CHECK(check_proc_wait, cred, proc);
665 
666 	return (error);
667 }
668