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 __FBSDID("$FreeBSD: releng/8.3/sys/security/mac/mac_process.c 191731 2009-05-01 21:05:40Z rwatson $");
47
48 #include "opt_kdtrace.h"
49 #include "opt_mac.h"
50
51 #include <sys/param.h>
52 #include <sys/condvar.h>
53 #include <sys/imgact.h>
54 #include <sys/kernel.h>
55 #include <sys/lock.h>
56 #include <sys/malloc.h>
57 #include <sys/mutex.h>
58 #include <sys/mac.h>
59 #include <sys/proc.h>
60 #include <sys/sbuf.h>
61 #include <sys/sdt.h>
62 #include <sys/systm.h>
63 #include <sys/vnode.h>
64 #include <sys/mount.h>
65 #include <sys/file.h>
66 #include <sys/namei.h>
67 #include <sys/sysctl.h>
68
69 #include <vm/vm.h>
70 #include <vm/pmap.h>
71 #include <vm/vm_map.h>
72 #include <vm/vm_object.h>
73
74 #include <security/mac/mac_framework.h>
75 #include <security/mac/mac_internal.h>
76 #include <security/mac/mac_policy.h>
77
78 static int mac_mmap_revocation = 1;
79 SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation, CTLFLAG_RW,
80 &mac_mmap_revocation, 0, "Revoke mmap access to files on subject "
81 "relabel");
82
83 static int mac_mmap_revocation_via_cow = 0;
84 SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation_via_cow, CTLFLAG_RW,
85 &mac_mmap_revocation_via_cow, 0, "Revoke mmap access to files via "
86 "copy-on-write semantics, or by removing all write access");
87
88 static void mac_proc_vm_revoke_recurse(struct thread *td,
89 struct ucred *cred, struct vm_map *map);
90
91 static struct label *
92 mac_proc_label_alloc(void)
93 {
94 struct label *label;
95
96 label = mac_labelzone_alloc(M_WAITOK);
97 MAC_POLICY_PERFORM(proc_init_label, label);
98 return (label);
99 }
100
101 void
102 mac_proc_init(struct proc *p)
103 {
104
105 if (mac_labeled & MPC_OBJECT_PROC)
106 p->p_label = mac_proc_label_alloc();
107 else
108 p->p_label = NULL;
109 }
110
111 static void
112 mac_proc_label_free(struct label *label)
113 {
114
115 MAC_POLICY_PERFORM_NOSLEEP(proc_destroy_label, label);
116 mac_labelzone_free(label);
117 }
118
119 void
120 mac_proc_destroy(struct proc *p)
121 {
122
123 if (p->p_label != NULL) {
124 mac_proc_label_free(p->p_label);
125 p->p_label = NULL;
126 }
127 }
128
129 void
130 mac_thread_userret(struct thread *td)
131 {
132
133 MAC_POLICY_PERFORM(thread_userret, td);
134 }
135
136 int
137 mac_execve_enter(struct image_params *imgp, struct mac *mac_p)
138 {
139 struct label *label;
140 struct mac mac;
141 char *buffer;
142 int error;
143
144 if (mac_p == NULL)
145 return (0);
146
147 if (!(mac_labeled & MPC_OBJECT_CRED))
148 return (EINVAL);
149
150 error = copyin(mac_p, &mac, sizeof(mac));
151 if (error)
152 return (error);
153
154 error = mac_check_structmac_consistent(&mac);
155 if (error)
156 return (error);
157
158 buffer = malloc(mac.m_buflen, M_MACTEMP, M_WAITOK);
159 error = copyinstr(mac.m_string, buffer, mac.m_buflen, NULL);
160 if (error) {
161 free(buffer, M_MACTEMP);
162 return (error);
163 }
164
165 label = mac_cred_label_alloc();
166 error = mac_cred_internalize_label(label, buffer);
167 free(buffer, M_MACTEMP);
168 if (error) {
169 mac_cred_label_free(label);
170 return (error);
171 }
172 imgp->execlabel = label;
173 return (0);
174 }
175
176 void
177 mac_execve_exit(struct image_params *imgp)
178 {
179 if (imgp->execlabel != NULL) {
180 mac_cred_label_free(imgp->execlabel);
181 imgp->execlabel = NULL;
182 }
183 }
184
185 void
186 mac_execve_interpreter_enter(struct vnode *interpvp,
187 struct label **interpvplabel)
188 {
189
190 if (mac_labeled & MPC_OBJECT_VNODE) {
191 *interpvplabel = mac_vnode_label_alloc();
192 mac_vnode_copy_label(interpvp->v_label, *interpvplabel);
193 } else
194 *interpvplabel = NULL;
195 }
196
197 void
198 mac_execve_interpreter_exit(struct label *interpvplabel)
199 {
200
201 if (interpvplabel != NULL)
202 mac_vnode_label_free(interpvplabel);
203 }
204
205 /*
206 * When relabeling a process, call out to the policies for the maximum
207 * permission allowed for each object type we know about in its memory space,
208 * and revoke access (in the least surprising ways we know) when necessary.
209 * The process lock is not held here.
210 */
211 void
212 mac_proc_vm_revoke(struct thread *td)
213 {
214 struct ucred *cred;
215
216 PROC_LOCK(td->td_proc);
217 cred = crhold(td->td_proc->p_ucred);
218 PROC_UNLOCK(td->td_proc);
219
220 /* XXX freeze all other threads */
221 mac_proc_vm_revoke_recurse(td, cred,
222 &td->td_proc->p_vmspace->vm_map);
223 /* XXX allow other threads to continue */
224
225 crfree(cred);
226 }
227
228 static __inline const char *
229 prot2str(vm_prot_t prot)
230 {
231
232 switch (prot & VM_PROT_ALL) {
233 case VM_PROT_READ:
234 return ("r--");
235 case VM_PROT_READ | VM_PROT_WRITE:
236 return ("rw-");
237 case VM_PROT_READ | VM_PROT_EXECUTE:
238 return ("r-x");
239 case VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE:
240 return ("rwx");
241 case VM_PROT_WRITE:
242 return ("-w-");
243 case VM_PROT_EXECUTE:
244 return ("--x");
245 case VM_PROT_WRITE | VM_PROT_EXECUTE:
246 return ("-wx");
247 default:
248 return ("---");
249 }
250 }
251
252 static void
253 mac_proc_vm_revoke_recurse(struct thread *td, struct ucred *cred,
254 struct vm_map *map)
255 {
256 vm_map_entry_t vme;
257 int vfslocked, result;
258 vm_prot_t revokeperms;
259 vm_object_t backing_object, object;
260 vm_ooffset_t offset;
261 struct vnode *vp;
262 struct mount *mp;
263
264 if (!mac_mmap_revocation)
265 return;
266
267 vm_map_lock(map);
268 for (vme = map->header.next; vme != &map->header; vme = vme->next) {
269 if (vme->eflags & MAP_ENTRY_IS_SUB_MAP) {
270 mac_proc_vm_revoke_recurse(td, cred,
271 vme->object.sub_map);
272 continue;
273 }
274 /*
275 * Skip over entries that obviously are not shared.
276 */
277 if (vme->eflags & (MAP_ENTRY_COW | MAP_ENTRY_NOSYNC) ||
278 !vme->max_protection)
279 continue;
280 /*
281 * Drill down to the deepest backing object.
282 */
283 offset = vme->offset;
284 object = vme->object.vm_object;
285 if (object == NULL)
286 continue;
287 VM_OBJECT_LOCK(object);
288 while ((backing_object = object->backing_object) != NULL) {
289 VM_OBJECT_LOCK(backing_object);
290 offset += object->backing_object_offset;
291 VM_OBJECT_UNLOCK(object);
292 object = backing_object;
293 }
294 VM_OBJECT_UNLOCK(object);
295 /*
296 * At the moment, vm_maps and objects aren't considered by
297 * the MAC system, so only things with backing by a normal
298 * object (read: vnodes) are checked.
299 */
300 if (object->type != OBJT_VNODE)
301 continue;
302 vp = (struct vnode *)object->handle;
303 vfslocked = VFS_LOCK_GIANT(vp->v_mount);
304 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
305 result = vme->max_protection;
306 mac_vnode_check_mmap_downgrade(cred, vp, &result);
307 VOP_UNLOCK(vp, 0);
308 /*
309 * Find out what maximum protection we may be allowing now
310 * but a policy needs to get removed.
311 */
312 revokeperms = vme->max_protection & ~result;
313 if (!revokeperms) {
314 VFS_UNLOCK_GIANT(vfslocked);
315 continue;
316 }
317 printf("pid %ld: revoking %s perms from %#lx:%ld "
318 "(max %s/cur %s)\n", (long)td->td_proc->p_pid,
319 prot2str(revokeperms), (u_long)vme->start,
320 (long)(vme->end - vme->start),
321 prot2str(vme->max_protection), prot2str(vme->protection));
322 /*
323 * This is the really simple case: if a map has more
324 * max_protection than is allowed, but it's not being
325 * actually used (that is, the current protection is still
326 * allowed), we can just wipe it out and do nothing more.
327 */
328 if ((vme->protection & revokeperms) == 0) {
329 vme->max_protection -= revokeperms;
330 } else {
331 if (revokeperms & VM_PROT_WRITE) {
332 /*
333 * In the more complicated case, flush out all
334 * pending changes to the object then turn it
335 * copy-on-write.
336 */
337 vm_object_reference(object);
338 (void) vn_start_write(vp, &mp, V_WAIT);
339 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
340 VM_OBJECT_LOCK(object);
341 vm_object_page_clean(object,
342 OFF_TO_IDX(offset),
343 OFF_TO_IDX(offset + vme->end - vme->start +
344 PAGE_MASK),
345 OBJPC_SYNC);
346 VM_OBJECT_UNLOCK(object);
347 VOP_UNLOCK(vp, 0);
348 vn_finished_write(mp);
349 vm_object_deallocate(object);
350 /*
351 * Why bother if there's no read permissions
352 * anymore? For the rest, we need to leave
353 * the write permissions on for COW, or
354 * remove them entirely if configured to.
355 */
356 if (!mac_mmap_revocation_via_cow) {
357 vme->max_protection &= ~VM_PROT_WRITE;
358 vme->protection &= ~VM_PROT_WRITE;
359 } if ((revokeperms & VM_PROT_READ) == 0)
360 vme->eflags |= MAP_ENTRY_COW |
361 MAP_ENTRY_NEEDS_COPY;
362 }
363 if (revokeperms & VM_PROT_EXECUTE) {
364 vme->max_protection &= ~VM_PROT_EXECUTE;
365 vme->protection &= ~VM_PROT_EXECUTE;
366 }
367 if (revokeperms & VM_PROT_READ) {
368 vme->max_protection = 0;
369 vme->protection = 0;
370 }
371 pmap_protect(map->pmap, vme->start, vme->end,
372 vme->protection & ~revokeperms);
373 vm_map_simplify_entry(map, vme);
374 }
375 VFS_UNLOCK_GIANT(vfslocked);
376 }
377 vm_map_unlock(map);
378 }
379
380 MAC_CHECK_PROBE_DEFINE2(proc_check_debug, "struct ucred *", "struct proc *");
381
382 int
383 mac_proc_check_debug(struct ucred *cred, struct proc *p)
384 {
385 int error;
386
387 PROC_LOCK_ASSERT(p, MA_OWNED);
388
389 MAC_POLICY_CHECK_NOSLEEP(proc_check_debug, cred, p);
390 MAC_CHECK_PROBE2(proc_check_debug, error, cred, p);
391
392 return (error);
393 }
394
395 MAC_CHECK_PROBE_DEFINE2(proc_check_sched, "struct ucred *", "struct proc *");
396
397 int
398 mac_proc_check_sched(struct ucred *cred, struct proc *p)
399 {
400 int error;
401
402 PROC_LOCK_ASSERT(p, MA_OWNED);
403
404 MAC_POLICY_CHECK_NOSLEEP(proc_check_sched, cred, p);
405 MAC_CHECK_PROBE2(proc_check_sched, error, cred, p);
406
407 return (error);
408 }
409
410 MAC_CHECK_PROBE_DEFINE3(proc_check_signal, "struct ucred *", "struct proc *",
411 "int");
412
413 int
414 mac_proc_check_signal(struct ucred *cred, struct proc *p, int signum)
415 {
416 int error;
417
418 PROC_LOCK_ASSERT(p, MA_OWNED);
419
420 MAC_POLICY_CHECK_NOSLEEP(proc_check_signal, cred, p, signum);
421 MAC_CHECK_PROBE3(proc_check_signal, error, cred, p, signum);
422
423 return (error);
424 }
425
426 MAC_CHECK_PROBE_DEFINE2(proc_check_wait, "struct ucred *", "struct proc *");
427
428 int
429 mac_proc_check_wait(struct ucred *cred, struct proc *p)
430 {
431 int error;
432
433 PROC_LOCK_ASSERT(p, MA_OWNED);
434
435 MAC_POLICY_CHECK_NOSLEEP(proc_check_wait, cred, p);
436 MAC_CHECK_PROBE2(proc_check_wait, error, cred, p);
437
438 return (error);
439 }
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