1 /*-
2 * Copyright (c) 1999-2002, 2008-2009 Robert N. M. Watson
3 * Copyright (c) 2001 Ilmar S. Habibulin
4 * Copyright (c) 2001-2003 Networks Associates Technology, Inc.
5 * Copyright (c) 2006 SPARTA, Inc.
6 * Copyright (c) 2008 Apple Inc.
7 * All rights reserved.
8 *
9 * This software was developed by Robert Watson and Ilmar Habibulin for the
10 * TrustedBSD Project.
11 *
12 * This software was developed for the FreeBSD Project in part by Network
13 * Associates Laboratories, the Security Research Division of Network
14 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
15 * as part of the DARPA CHATS research program.
16 *
17 * This software was enhanced by SPARTA ISSO under SPAWAR contract
18 * N66001-04-C-6019 ("SEFOS").
19 *
20 * This software was developed at the University of Cambridge Computer
21 * Laboratory with support from a grant from Google, Inc.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the above copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 *
32 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
33 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
34 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
35 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
36 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
37 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
38 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
39 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
40 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
41 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
42 * SUCH DAMAGE.
43 */
44
45 #include <sys/cdefs.h>
46 #include "opt_mac.h"
47
48 #include <sys/param.h>
49 #include <sys/condvar.h>
50 #include <sys/imgact.h>
51 #include <sys/kernel.h>
52 #include <sys/lock.h>
53 #include <sys/malloc.h>
54 #include <sys/mac.h>
55 #include <sys/proc.h>
56 #include <sys/rwlock.h>
57 #include <sys/sbuf.h>
58 #include <sys/sdt.h>
59 #include <sys/systm.h>
60 #include <sys/vnode.h>
61 #include <sys/mount.h>
62 #include <sys/file.h>
63 #include <sys/namei.h>
64 #include <sys/sysctl.h>
65
66 #include <vm/vm.h>
67 #include <vm/pmap.h>
68 #include <vm/vm_map.h>
69 #include <vm/vm_object.h>
70
71 #include <security/mac/mac_framework.h>
72 #include <security/mac/mac_internal.h>
73 #include <security/mac/mac_policy.h>
74
75 static int mac_mmap_revocation = 1;
76 SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation, CTLFLAG_RW,
77 &mac_mmap_revocation, 0, "Revoke mmap access to files on subject "
78 "relabel");
79
80 static int mac_mmap_revocation_via_cow = 0;
81 SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation_via_cow, CTLFLAG_RW,
82 &mac_mmap_revocation_via_cow, 0, "Revoke mmap access to files via "
83 "copy-on-write semantics, or by removing all write access");
84
85 static void mac_proc_vm_revoke_recurse(struct thread *td,
86 struct ucred *cred, struct vm_map *map);
87
88 static struct label *
mac_proc_label_alloc(void)89 mac_proc_label_alloc(void)
90 {
91 struct label *label;
92
93 label = mac_labelzone_alloc(M_WAITOK);
94 MAC_POLICY_PERFORM(proc_init_label, label);
95 return (label);
96 }
97
98 void
mac_proc_init(struct proc * p)99 mac_proc_init(struct proc *p)
100 {
101
102 if (mac_labeled & MPC_OBJECT_PROC)
103 p->p_label = mac_proc_label_alloc();
104 else
105 p->p_label = NULL;
106 }
107
108 static void
mac_proc_label_free(struct label * label)109 mac_proc_label_free(struct label *label)
110 {
111
112 MAC_POLICY_PERFORM_NOSLEEP(proc_destroy_label, label);
113 mac_labelzone_free(label);
114 }
115
116 void
mac_proc_destroy(struct proc * p)117 mac_proc_destroy(struct proc *p)
118 {
119
120 if (p->p_label != NULL) {
121 mac_proc_label_free(p->p_label);
122 p->p_label = NULL;
123 }
124 }
125
126 void
mac_thread_userret(struct thread * td)127 mac_thread_userret(struct thread *td)
128 {
129
130 MAC_POLICY_PERFORM(thread_userret, td);
131 }
132
133 int
mac_execve_enter(struct image_params * imgp,struct mac * mac_p)134 mac_execve_enter(struct image_params *imgp, struct mac *mac_p)
135 {
136 struct label *label;
137 struct mac mac;
138 char *buffer;
139 int error;
140
141 if (mac_p == NULL)
142 return (0);
143
144 if (!(mac_labeled & MPC_OBJECT_CRED))
145 return (EINVAL);
146
147 error = copyin(mac_p, &mac, sizeof(mac));
148 if (error)
149 return (error);
150
151 error = mac_check_structmac_consistent(&mac);
152 if (error)
153 return (error);
154
155 buffer = malloc(mac.m_buflen, M_MACTEMP, M_WAITOK);
156 error = copyinstr(mac.m_string, buffer, mac.m_buflen, NULL);
157 if (error) {
158 free(buffer, M_MACTEMP);
159 return (error);
160 }
161
162 label = mac_cred_label_alloc();
163 error = mac_cred_internalize_label(label, buffer);
164 free(buffer, M_MACTEMP);
165 if (error) {
166 mac_cred_label_free(label);
167 return (error);
168 }
169 imgp->execlabel = label;
170 return (0);
171 }
172
173 void
mac_execve_exit(struct image_params * imgp)174 mac_execve_exit(struct image_params *imgp)
175 {
176 if (imgp->execlabel != NULL) {
177 mac_cred_label_free(imgp->execlabel);
178 imgp->execlabel = NULL;
179 }
180 }
181
182 void
mac_execve_interpreter_enter(struct vnode * interpvp,struct label ** interpvplabel)183 mac_execve_interpreter_enter(struct vnode *interpvp,
184 struct label **interpvplabel)
185 {
186
187 if (mac_labeled & MPC_OBJECT_VNODE) {
188 *interpvplabel = mac_vnode_label_alloc();
189 mac_vnode_copy_label(interpvp->v_label, *interpvplabel);
190 } else
191 *interpvplabel = NULL;
192 }
193
194 void
mac_execve_interpreter_exit(struct label * interpvplabel)195 mac_execve_interpreter_exit(struct label *interpvplabel)
196 {
197
198 if (interpvplabel != NULL)
199 mac_vnode_label_free(interpvplabel);
200 }
201
202 /*
203 * When relabeling a process, call out to the policies for the maximum
204 * permission allowed for each object type we know about in its memory space,
205 * and revoke access (in the least surprising ways we know) when necessary.
206 * The process lock is not held here.
207 */
208 void
mac_proc_vm_revoke(struct thread * td)209 mac_proc_vm_revoke(struct thread *td)
210 {
211 struct ucred *cred;
212
213 PROC_LOCK(td->td_proc);
214 cred = crhold(td->td_proc->p_ucred);
215 PROC_UNLOCK(td->td_proc);
216
217 /* XXX freeze all other threads */
218 mac_proc_vm_revoke_recurse(td, cred,
219 &td->td_proc->p_vmspace->vm_map);
220 /* XXX allow other threads to continue */
221
222 crfree(cred);
223 }
224
225 static __inline const char *
prot2str(vm_prot_t prot)226 prot2str(vm_prot_t prot)
227 {
228
229 switch (prot & VM_PROT_ALL) {
230 case VM_PROT_READ:
231 return ("r--");
232 case VM_PROT_READ | VM_PROT_WRITE:
233 return ("rw-");
234 case VM_PROT_READ | VM_PROT_EXECUTE:
235 return ("r-x");
236 case VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE:
237 return ("rwx");
238 case VM_PROT_WRITE:
239 return ("-w-");
240 case VM_PROT_EXECUTE:
241 return ("--x");
242 case VM_PROT_WRITE | VM_PROT_EXECUTE:
243 return ("-wx");
244 default:
245 return ("---");
246 }
247 }
248
249 static void
mac_proc_vm_revoke_recurse(struct thread * td,struct ucred * cred,struct vm_map * map)250 mac_proc_vm_revoke_recurse(struct thread *td, struct ucred *cred,
251 struct vm_map *map)
252 {
253 vm_map_entry_t prev, vme;
254 int result;
255 vm_prot_t revokeperms;
256 vm_object_t backing_object, object;
257 vm_ooffset_t offset;
258 struct vnode *vp;
259 struct mount *mp;
260
261 if (!mac_mmap_revocation)
262 return;
263
264 prev = &map->header;
265 vm_map_lock(map);
266 for (vme = vm_map_entry_first(map); vme != &map->header;
267 prev = vme, vme = vm_map_entry_succ(prev)) {
268 if (vme->eflags & MAP_ENTRY_IS_SUB_MAP) {
269 mac_proc_vm_revoke_recurse(td, cred,
270 vme->object.sub_map);
271 continue;
272 }
273 /*
274 * Skip over entries that obviously are not shared.
275 */
276 if (vme->eflags & (MAP_ENTRY_COW | MAP_ENTRY_NOSYNC) ||
277 !vme->max_protection)
278 continue;
279 /*
280 * Drill down to the deepest backing object.
281 */
282 offset = vme->offset;
283 object = vme->object.vm_object;
284 if (object == NULL)
285 continue;
286 VM_OBJECT_RLOCK(object);
287 while ((backing_object = object->backing_object) != NULL) {
288 VM_OBJECT_RLOCK(backing_object);
289 offset += object->backing_object_offset;
290 VM_OBJECT_RUNLOCK(object);
291 object = backing_object;
292 }
293 VM_OBJECT_RUNLOCK(object);
294 /*
295 * At the moment, vm_maps and objects aren't considered by
296 * the MAC system, so only things with backing by a normal
297 * object (read: vnodes) are checked.
298 */
299 if (object->type != OBJT_VNODE)
300 continue;
301 vp = (struct vnode *)object->handle;
302 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
303 result = vme->max_protection;
304 mac_vnode_check_mmap_downgrade(cred, vp, &result);
305 VOP_UNLOCK(vp);
306 /*
307 * Find out what maximum protection we may be allowing now
308 * but a policy needs to get removed.
309 */
310 revokeperms = vme->max_protection & ~result;
311 if (!revokeperms)
312 continue;
313 printf("pid %ld: revoking %s perms from %#lx:%ld "
314 "(max %s/cur %s)\n", (long)td->td_proc->p_pid,
315 prot2str(revokeperms), (u_long)vme->start,
316 (long)(vme->end - vme->start),
317 prot2str(vme->max_protection), prot2str(vme->protection));
318 /*
319 * This is the really simple case: if a map has more
320 * max_protection than is allowed, but it's not being
321 * actually used (that is, the current protection is still
322 * allowed), we can just wipe it out and do nothing more.
323 */
324 if ((vme->protection & revokeperms) == 0) {
325 vme->max_protection -= revokeperms;
326 } else {
327 if (revokeperms & VM_PROT_WRITE) {
328 /*
329 * In the more complicated case, flush out all
330 * pending changes to the object then turn it
331 * copy-on-write.
332 */
333 vm_object_reference(object);
334 (void) vn_start_write(vp, &mp, V_WAIT);
335 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
336 VM_OBJECT_WLOCK(object);
337 vm_object_page_clean(object, offset, offset +
338 vme->end - vme->start, OBJPC_SYNC);
339 VM_OBJECT_WUNLOCK(object);
340 VOP_UNLOCK(vp);
341 vn_finished_write(mp);
342 vm_object_deallocate(object);
343 /*
344 * Why bother if there's no read permissions
345 * anymore? For the rest, we need to leave
346 * the write permissions on for COW, or
347 * remove them entirely if configured to.
348 */
349 if (!mac_mmap_revocation_via_cow) {
350 vme->max_protection &= ~VM_PROT_WRITE;
351 vme->protection &= ~VM_PROT_WRITE;
352 } if ((revokeperms & VM_PROT_READ) == 0)
353 vme->eflags |= MAP_ENTRY_COW |
354 MAP_ENTRY_NEEDS_COPY;
355 }
356 if (revokeperms & VM_PROT_EXECUTE) {
357 vme->max_protection &= ~VM_PROT_EXECUTE;
358 vme->protection &= ~VM_PROT_EXECUTE;
359 }
360 if (revokeperms & VM_PROT_READ) {
361 vme->max_protection = 0;
362 vme->protection = 0;
363 }
364 pmap_protect(map->pmap, vme->start, vme->end,
365 vme->protection & ~revokeperms);
366 vm_map_try_merge_entries(map, prev, vme);
367 }
368 }
369 vm_map_unlock(map);
370 }
371
372 MAC_CHECK_PROBE_DEFINE2(proc_check_debug, "struct ucred *", "struct proc *");
373
374 int
mac_proc_check_debug(struct ucred * cred,struct proc * p)375 mac_proc_check_debug(struct ucred *cred, struct proc *p)
376 {
377 int error;
378
379 PROC_LOCK_ASSERT(p, MA_OWNED);
380
381 MAC_POLICY_CHECK_NOSLEEP(proc_check_debug, cred, p);
382 MAC_CHECK_PROBE2(proc_check_debug, error, cred, p);
383
384 return (error);
385 }
386
387 MAC_CHECK_PROBE_DEFINE2(proc_check_sched, "struct ucred *", "struct proc *");
388
389 int
mac_proc_check_sched(struct ucred * cred,struct proc * p)390 mac_proc_check_sched(struct ucred *cred, struct proc *p)
391 {
392 int error;
393
394 PROC_LOCK_ASSERT(p, MA_OWNED);
395
396 MAC_POLICY_CHECK_NOSLEEP(proc_check_sched, cred, p);
397 MAC_CHECK_PROBE2(proc_check_sched, error, cred, p);
398
399 return (error);
400 }
401
402 MAC_CHECK_PROBE_DEFINE3(proc_check_signal, "struct ucred *", "struct proc *",
403 "int");
404
405 int
mac_proc_check_signal(struct ucred * cred,struct proc * p,int signum)406 mac_proc_check_signal(struct ucred *cred, struct proc *p, int signum)
407 {
408 int error;
409
410 PROC_LOCK_ASSERT(p, MA_OWNED);
411
412 MAC_POLICY_CHECK_NOSLEEP(proc_check_signal, cred, p, signum);
413 MAC_CHECK_PROBE3(proc_check_signal, error, cred, p, signum);
414
415 return (error);
416 }
417
418 MAC_CHECK_PROBE_DEFINE2(proc_check_wait, "struct ucred *", "struct proc *");
419
420 int
mac_proc_check_wait(struct ucred * cred,struct proc * p)421 mac_proc_check_wait(struct ucred *cred, struct proc *p)
422 {
423 int error;
424
425 PROC_LOCK_ASSERT(p, MA_OWNED);
426
427 MAC_POLICY_CHECK_NOSLEEP(proc_check_wait, cred, p);
428 MAC_CHECK_PROBE2(proc_check_wait, error, cred, p);
429
430 return (error);
431 }
432