1 /*-
2 * Copyright (c) 1999-2002, 2006, 2009 Robert N. M. Watson
3 * Copyright (c) 2001 Ilmar S. Habibulin
4 * Copyright (c) 2001-2005 Networks Associates Technology, Inc.
5 * Copyright (c) 2005-2006 SPARTA, Inc.
6 * Copyright (c) 2008-2009 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 /*-
46 * Framework for extensible kernel access control. This file contains core
47 * kernel infrastructure for the TrustedBSD MAC Framework, including policy
48 * registration, versioning, locking, error composition operator, and system
49 * calls.
50 *
51 * The MAC Framework implements three programming interfaces:
52 *
53 * - The kernel MAC interface, defined in mac_framework.h, and invoked
54 * throughout the kernel to request security decisions, notify of security
55 * related events, etc.
56 *
57 * - The MAC policy module interface, defined in mac_policy.h, which is
58 * implemented by MAC policy modules and invoked by the MAC Framework to
59 * forward kernel security requests and notifications to policy modules.
60 *
61 * - The user MAC API, defined in mac.h, which allows user programs to query
62 * and set label state on objects.
63 *
64 * The majority of the MAC Framework implementation may be found in
65 * src/sys/security/mac. Sample policy modules may be found in
66 * src/sys/security/mac_*.
67 */
68
69 #include "opt_kdtrace.h"
70 #include "opt_mac.h"
71
72 #include <sys/cdefs.h>
73 __FBSDID("$FreeBSD$");
74
75 #include <sys/param.h>
76 #include <sys/systm.h>
77 #include <sys/condvar.h>
78 #include <sys/kernel.h>
79 #include <sys/lock.h>
80 #include <sys/mac.h>
81 #include <sys/module.h>
82 #include <sys/rmlock.h>
83 #include <sys/sdt.h>
84 #include <sys/sx.h>
85 #include <sys/sysctl.h>
86
87 #include <security/mac/mac_framework.h>
88 #include <security/mac/mac_internal.h>
89 #include <security/mac/mac_policy.h>
90
91 /*
92 * DTrace SDT providers for MAC.
93 */
94 SDT_PROVIDER_DEFINE(mac);
95 SDT_PROVIDER_DEFINE(mac_framework);
96
97 SDT_PROBE_DEFINE2(mac, , policy, modevent, "int",
98 "struct mac_policy_conf *");
99 SDT_PROBE_DEFINE1(mac, , policy, register,
100 "struct mac_policy_conf *");
101 SDT_PROBE_DEFINE1(mac, , policy, unregister,
102 "struct mac_policy_conf *");
103
104 /*
105 * Root sysctl node for all MAC and MAC policy controls.
106 */
107 SYSCTL_NODE(_security, OID_AUTO, mac, CTLFLAG_RW, 0,
108 "TrustedBSD MAC policy controls");
109
110 /*
111 * Declare that the kernel provides MAC support, version 3 (FreeBSD 7.x).
112 * This permits modules to refuse to be loaded if the necessary support isn't
113 * present, even if it's pre-boot.
114 */
115 MODULE_VERSION(kernel_mac_support, MAC_VERSION);
116
117 static unsigned int mac_version = MAC_VERSION;
118 SYSCTL_UINT(_security_mac, OID_AUTO, version, CTLFLAG_RD, &mac_version, 0,
119 "");
120
121 /*
122 * Labels consist of a indexed set of "slots", which are allocated policies
123 * as required. The MAC Framework maintains a bitmask of slots allocated so
124 * far to prevent reuse. Slots cannot be reused, as the MAC Framework
125 * guarantees that newly allocated slots in labels will be NULL unless
126 * otherwise initialized, and because we do not have a mechanism to garbage
127 * collect slots on policy unload. As labeled policies tend to be statically
128 * loaded during boot, and not frequently unloaded and reloaded, this is not
129 * generally an issue.
130 */
131 #if MAC_MAX_SLOTS > 32
132 #error "MAC_MAX_SLOTS too large"
133 #endif
134
135 static unsigned int mac_max_slots = MAC_MAX_SLOTS;
136 static unsigned int mac_slot_offsets_free = (1 << MAC_MAX_SLOTS) - 1;
137 SYSCTL_UINT(_security_mac, OID_AUTO, max_slots, CTLFLAG_RD, &mac_max_slots,
138 0, "");
139
140 /*
141 * Has the kernel started generating labeled objects yet? All read/write
142 * access to this variable is serialized during the boot process. Following
143 * the end of serialization, we don't update this flag; no locking.
144 */
145 static int mac_late = 0;
146
147 /*
148 * Each policy declares a mask of object types requiring labels to be
149 * allocated for them. For convenience, we combine and cache the bitwise or
150 * of the per-policy object flags to track whether we will allocate a label
151 * for an object type at run-time.
152 */
153 uint64_t mac_labeled;
154 SYSCTL_UQUAD(_security_mac, OID_AUTO, labeled, CTLFLAG_RD, &mac_labeled, 0,
155 "Mask of object types being labeled");
156
157 MALLOC_DEFINE(M_MACTEMP, "mactemp", "MAC temporary label storage");
158
159 /*
160 * MAC policy modules are placed in one of two lists: mac_static_policy_list,
161 * for policies that are loaded early and cannot be unloaded, and
162 * mac_policy_list, which holds policies either loaded later in the boot
163 * cycle or that may be unloaded. The static policy list does not require
164 * locks to iterate over, but the dynamic list requires synchronization.
165 * Support for dynamic policy loading can be compiled out using the
166 * MAC_STATIC kernel option.
167 *
168 * The dynamic policy list is protected by two locks: modifying the list
169 * requires both locks to be held exclusively. One of the locks,
170 * mac_policy_rm, is acquired over policy entry points that will never sleep;
171 * the other, mac_policy_sx, is acquire over policy entry points that may
172 * sleep. The former category will be used when kernel locks may be held
173 * over calls to the MAC Framework, during network processing in ithreads,
174 * etc. The latter will tend to involve potentially blocking memory
175 * allocations, extended attribute I/O, etc.
176 */
177 #ifndef MAC_STATIC
178 static struct rmlock mac_policy_rm; /* Non-sleeping entry points. */
179 static struct sx mac_policy_sx; /* Sleeping entry points. */
180 #endif
181
182 struct mac_policy_list_head mac_policy_list;
183 struct mac_policy_list_head mac_static_policy_list;
184 u_int mac_policy_count; /* Registered policy count. */
185
186 static void mac_policy_xlock(void);
187 static void mac_policy_xlock_assert(void);
188 static void mac_policy_xunlock(void);
189
190 void
191 mac_policy_slock_nosleep(struct rm_priotracker *tracker)
192 {
193
194 #ifndef MAC_STATIC
195 if (!mac_late)
196 return;
197
198 rm_rlock(&mac_policy_rm, tracker);
199 #endif
200 }
201
202 void
203 mac_policy_slock_sleep(void)
204 {
205
206 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
207 "mac_policy_slock_sleep");
208
209 #ifndef MAC_STATIC
210 if (!mac_late)
211 return;
212
213 sx_slock(&mac_policy_sx);
214 #endif
215 }
216
217 void
218 mac_policy_sunlock_nosleep(struct rm_priotracker *tracker)
219 {
220
221 #ifndef MAC_STATIC
222 if (!mac_late)
223 return;
224
225 rm_runlock(&mac_policy_rm, tracker);
226 #endif
227 }
228
229 void
230 mac_policy_sunlock_sleep(void)
231 {
232
233 #ifndef MAC_STATIC
234 if (!mac_late)
235 return;
236
237 sx_sunlock(&mac_policy_sx);
238 #endif
239 }
240
241 static void
242 mac_policy_xlock(void)
243 {
244
245 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
246 "mac_policy_xlock()");
247
248 #ifndef MAC_STATIC
249 if (!mac_late)
250 return;
251
252 sx_xlock(&mac_policy_sx);
253 rm_wlock(&mac_policy_rm);
254 #endif
255 }
256
257 static void
258 mac_policy_xunlock(void)
259 {
260
261 #ifndef MAC_STATIC
262 if (!mac_late)
263 return;
264
265 rm_wunlock(&mac_policy_rm);
266 sx_xunlock(&mac_policy_sx);
267 #endif
268 }
269
270 static void
271 mac_policy_xlock_assert(void)
272 {
273
274 #ifndef MAC_STATIC
275 if (!mac_late)
276 return;
277
278 /* XXXRW: rm_assert(&mac_policy_rm, RA_WLOCKED); */
279 sx_assert(&mac_policy_sx, SA_XLOCKED);
280 #endif
281 }
282
283 /*
284 * Initialize the MAC subsystem, including appropriate SMP locks.
285 */
286 static void
287 mac_init(void)
288 {
289
290 LIST_INIT(&mac_static_policy_list);
291 LIST_INIT(&mac_policy_list);
292 mac_labelzone_init();
293
294 #ifndef MAC_STATIC
295 rm_init_flags(&mac_policy_rm, "mac_policy_rm", RM_NOWITNESS |
296 RM_RECURSE);
297 sx_init_flags(&mac_policy_sx, "mac_policy_sx", SX_NOWITNESS);
298 #endif
299 }
300
301 /*
302 * For the purposes of modules that want to know if they were loaded "early",
303 * set the mac_late flag once we've processed modules either linked into the
304 * kernel, or loaded before the kernel startup.
305 */
306 static void
307 mac_late_init(void)
308 {
309
310 mac_late = 1;
311 }
312
313 /*
314 * Given a policy, derive from its set of non-NULL label init methods what
315 * object types the policy is interested in.
316 */
317 static uint64_t
318 mac_policy_getlabeled(struct mac_policy_conf *mpc)
319 {
320 uint64_t labeled;
321
322 #define MPC_FLAG(method, flag) \
323 if (mpc->mpc_ops->mpo_ ## method != NULL) \
324 labeled |= (flag); \
325
326 labeled = 0;
327 MPC_FLAG(cred_init_label, MPC_OBJECT_CRED);
328 MPC_FLAG(proc_init_label, MPC_OBJECT_PROC);
329 MPC_FLAG(vnode_init_label, MPC_OBJECT_VNODE);
330 MPC_FLAG(inpcb_init_label, MPC_OBJECT_INPCB);
331 MPC_FLAG(socket_init_label, MPC_OBJECT_SOCKET);
332 MPC_FLAG(devfs_init_label, MPC_OBJECT_DEVFS);
333 MPC_FLAG(mbuf_init_label, MPC_OBJECT_MBUF);
334 MPC_FLAG(ipq_init_label, MPC_OBJECT_IPQ);
335 MPC_FLAG(ifnet_init_label, MPC_OBJECT_IFNET);
336 MPC_FLAG(bpfdesc_init_label, MPC_OBJECT_BPFDESC);
337 MPC_FLAG(pipe_init_label, MPC_OBJECT_PIPE);
338 MPC_FLAG(mount_init_label, MPC_OBJECT_MOUNT);
339 MPC_FLAG(posixsem_init_label, MPC_OBJECT_POSIXSEM);
340 MPC_FLAG(posixshm_init_label, MPC_OBJECT_POSIXSHM);
341 MPC_FLAG(sysvmsg_init_label, MPC_OBJECT_SYSVMSG);
342 MPC_FLAG(sysvmsq_init_label, MPC_OBJECT_SYSVMSQ);
343 MPC_FLAG(sysvsem_init_label, MPC_OBJECT_SYSVSEM);
344 MPC_FLAG(sysvshm_init_label, MPC_OBJECT_SYSVSHM);
345 MPC_FLAG(syncache_init_label, MPC_OBJECT_SYNCACHE);
346 MPC_FLAG(ip6q_init_label, MPC_OBJECT_IP6Q);
347
348 #undef MPC_FLAG
349 return (labeled);
350 }
351
352 /*
353 * When policies are loaded or unloaded, walk the list of registered policies
354 * and built mac_labeled, a bitmask representing the union of all objects
355 * requiring labels across all policies.
356 */
357 static void
358 mac_policy_update(void)
359 {
360 struct mac_policy_conf *mpc;
361
362 mac_policy_xlock_assert();
363
364 mac_labeled = 0;
365 mac_policy_count = 0;
366 LIST_FOREACH(mpc, &mac_static_policy_list, mpc_list) {
367 mac_labeled |= mac_policy_getlabeled(mpc);
368 mac_policy_count++;
369 }
370 LIST_FOREACH(mpc, &mac_policy_list, mpc_list) {
371 mac_labeled |= mac_policy_getlabeled(mpc);
372 mac_policy_count++;
373 }
374 }
375
376 static int
377 mac_policy_register(struct mac_policy_conf *mpc)
378 {
379 struct mac_policy_conf *tmpc;
380 int error, slot, static_entry;
381
382 error = 0;
383
384 /*
385 * We don't technically need exclusive access while !mac_late, but
386 * hold it for assertion consistency.
387 */
388 mac_policy_xlock();
389
390 /*
391 * If the module can potentially be unloaded, or we're loading late,
392 * we have to stick it in the non-static list and pay an extra
393 * performance overhead. Otherwise, we can pay a light locking cost
394 * and stick it in the static list.
395 */
396 static_entry = (!mac_late &&
397 !(mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK));
398
399 if (static_entry) {
400 LIST_FOREACH(tmpc, &mac_static_policy_list, mpc_list) {
401 if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) {
402 error = EEXIST;
403 goto out;
404 }
405 }
406 } else {
407 LIST_FOREACH(tmpc, &mac_policy_list, mpc_list) {
408 if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) {
409 error = EEXIST;
410 goto out;
411 }
412 }
413 }
414 if (mpc->mpc_field_off != NULL) {
415 slot = ffs(mac_slot_offsets_free);
416 if (slot == 0) {
417 error = ENOMEM;
418 goto out;
419 }
420 slot--;
421 mac_slot_offsets_free &= ~(1 << slot);
422 *mpc->mpc_field_off = slot;
423 }
424 mpc->mpc_runtime_flags |= MPC_RUNTIME_FLAG_REGISTERED;
425
426 /*
427 * If we're loading a MAC module after the framework has initialized,
428 * it has to go into the dynamic list. If we're loading it before
429 * we've finished initializing, it can go into the static list with
430 * weaker locker requirements.
431 */
432 if (static_entry)
433 LIST_INSERT_HEAD(&mac_static_policy_list, mpc, mpc_list);
434 else
435 LIST_INSERT_HEAD(&mac_policy_list, mpc, mpc_list);
436
437 /*
438 * Per-policy initialization. Currently, this takes place under the
439 * exclusive lock, so policies must not sleep in their init method.
440 * In the future, we may want to separate "init" from "start", with
441 * "init" occuring without the lock held. Likewise, on tear-down,
442 * breaking out "stop" from "destroy".
443 */
444 if (mpc->mpc_ops->mpo_init != NULL)
445 (*(mpc->mpc_ops->mpo_init))(mpc);
446 mac_policy_update();
447
448 SDT_PROBE1(mac, , policy, register, mpc);
449 printf("Security policy loaded: %s (%s)\n", mpc->mpc_fullname,
450 mpc->mpc_name);
451
452 out:
453 mac_policy_xunlock();
454 return (error);
455 }
456
457 static int
458 mac_policy_unregister(struct mac_policy_conf *mpc)
459 {
460
461 /*
462 * If we fail the load, we may get a request to unload. Check to see
463 * if we did the run-time registration, and if not, silently succeed.
464 */
465 mac_policy_xlock();
466 if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) == 0) {
467 mac_policy_xunlock();
468 return (0);
469 }
470 #if 0
471 /*
472 * Don't allow unloading modules with private data.
473 */
474 if (mpc->mpc_field_off != NULL) {
475 mac_policy_xunlock();
476 return (EBUSY);
477 }
478 #endif
479 /*
480 * Only allow the unload to proceed if the module is unloadable by
481 * its own definition.
482 */
483 if ((mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK) == 0) {
484 mac_policy_xunlock();
485 return (EBUSY);
486 }
487 if (mpc->mpc_ops->mpo_destroy != NULL)
488 (*(mpc->mpc_ops->mpo_destroy))(mpc);
489
490 LIST_REMOVE(mpc, mpc_list);
491 mpc->mpc_runtime_flags &= ~MPC_RUNTIME_FLAG_REGISTERED;
492 mac_policy_update();
493 mac_policy_xunlock();
494
495 SDT_PROBE1(mac, , policy, unregister, mpc);
496 printf("Security policy unload: %s (%s)\n", mpc->mpc_fullname,
497 mpc->mpc_name);
498
499 return (0);
500 }
501
502 /*
503 * Allow MAC policy modules to register during boot, etc.
504 */
505 int
506 mac_policy_modevent(module_t mod, int type, void *data)
507 {
508 struct mac_policy_conf *mpc;
509 int error;
510
511 error = 0;
512 mpc = (struct mac_policy_conf *) data;
513
514 #ifdef MAC_STATIC
515 if (mac_late) {
516 printf("mac_policy_modevent: MAC_STATIC and late\n");
517 return (EBUSY);
518 }
519 #endif
520
521 SDT_PROBE2(mac, , policy, modevent, type, mpc);
522 switch (type) {
523 case MOD_LOAD:
524 if (mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_NOTLATE &&
525 mac_late) {
526 printf("mac_policy_modevent: can't load %s policy "
527 "after booting\n", mpc->mpc_name);
528 error = EBUSY;
529 break;
530 }
531 error = mac_policy_register(mpc);
532 break;
533 case MOD_UNLOAD:
534 /* Don't unregister the module if it was never registered. */
535 if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED)
536 != 0)
537 error = mac_policy_unregister(mpc);
538 else
539 error = 0;
540 break;
541 default:
542 error = EOPNOTSUPP;
543 break;
544 }
545
546 return (error);
547 }
548
549 /*
550 * Define an error value precedence, and given two arguments, selects the
551 * value with the higher precedence.
552 */
553 int
554 mac_error_select(int error1, int error2)
555 {
556
557 /* Certain decision-making errors take top priority. */
558 if (error1 == EDEADLK || error2 == EDEADLK)
559 return (EDEADLK);
560
561 /* Invalid arguments should be reported where possible. */
562 if (error1 == EINVAL || error2 == EINVAL)
563 return (EINVAL);
564
565 /* Precedence goes to "visibility", with both process and file. */
566 if (error1 == ESRCH || error2 == ESRCH)
567 return (ESRCH);
568
569 if (error1 == ENOENT || error2 == ENOENT)
570 return (ENOENT);
571
572 /* Precedence goes to DAC/MAC protections. */
573 if (error1 == EACCES || error2 == EACCES)
574 return (EACCES);
575
576 /* Precedence goes to privilege. */
577 if (error1 == EPERM || error2 == EPERM)
578 return (EPERM);
579
580 /* Precedence goes to error over success; otherwise, arbitrary. */
581 if (error1 != 0)
582 return (error1);
583 return (error2);
584 }
585
586 int
587 mac_check_structmac_consistent(struct mac *mac)
588 {
589
590 if (mac->m_buflen > MAC_MAX_LABEL_BUF_LEN)
591 return (EINVAL);
592
593 return (0);
594 }
595
596 SYSINIT(mac, SI_SUB_MAC, SI_ORDER_FIRST, mac_init, NULL);
597 SYSINIT(mac_late, SI_SUB_MAC_LATE, SI_ORDER_FIRST, mac_late_init, NULL);
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