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_mac.h"
70
71 #include <sys/cdefs.h>
72 __FBSDID("$FreeBSD: releng/11.0/sys/security/mac/mac_framework.c 299187 2016-05-06 16:59:04Z pfg $");
73
74 #include <sys/param.h>
75 #include <sys/systm.h>
76 #include <sys/condvar.h>
77 #include <sys/kernel.h>
78 #include <sys/lock.h>
79 #include <sys/mac.h>
80 #include <sys/module.h>
81 #include <sys/rmlock.h>
82 #include <sys/sdt.h>
83 #include <sys/sx.h>
84 #include <sys/sysctl.h>
85
86 #include <security/mac/mac_framework.h>
87 #include <security/mac/mac_internal.h>
88 #include <security/mac/mac_policy.h>
89
90 /*
91 * DTrace SDT providers for MAC.
92 */
93 SDT_PROVIDER_DEFINE(mac);
94 SDT_PROVIDER_DEFINE(mac_framework);
95
96 SDT_PROBE_DEFINE2(mac, , policy, modevent, "int",
97 "struct mac_policy_conf *");
98 SDT_PROBE_DEFINE1(mac, , policy, register,
99 "struct mac_policy_conf *");
100 SDT_PROBE_DEFINE1(mac, , policy, unregister,
101 "struct mac_policy_conf *");
102
103 /*
104 * Root sysctl node for all MAC and MAC policy controls.
105 */
106 SYSCTL_NODE(_security, OID_AUTO, mac, CTLFLAG_RW, 0,
107 "TrustedBSD MAC policy controls");
108
109 /*
110 * Declare that the kernel provides MAC support, version 3 (FreeBSD 7.x).
111 * This permits modules to refuse to be loaded if the necessary support isn't
112 * present, even if it's pre-boot.
113 */
114 MODULE_VERSION(kernel_mac_support, MAC_VERSION);
115
116 static unsigned int mac_version = MAC_VERSION;
117 SYSCTL_UINT(_security_mac, OID_AUTO, version, CTLFLAG_RD, &mac_version, 0,
118 "");
119
120 /*
121 * Labels consist of a indexed set of "slots", which are allocated policies
122 * as required. The MAC Framework maintains a bitmask of slots allocated so
123 * far to prevent reuse. Slots cannot be reused, as the MAC Framework
124 * guarantees that newly allocated slots in labels will be NULL unless
125 * otherwise initialized, and because we do not have a mechanism to garbage
126 * collect slots on policy unload. As labeled policies tend to be statically
127 * loaded during boot, and not frequently unloaded and reloaded, this is not
128 * generally an issue.
129 */
130 #if MAC_MAX_SLOTS > 32
131 #error "MAC_MAX_SLOTS too large"
132 #endif
133
134 static unsigned int mac_max_slots = MAC_MAX_SLOTS;
135 static unsigned int mac_slot_offsets_free = (1 << MAC_MAX_SLOTS) - 1;
136 SYSCTL_UINT(_security_mac, OID_AUTO, max_slots, CTLFLAG_RD, &mac_max_slots,
137 0, "");
138
139 /*
140 * Has the kernel started generating labeled objects yet? All read/write
141 * access to this variable is serialized during the boot process. Following
142 * the end of serialization, we don't update this flag; no locking.
143 */
144 static int mac_late = 0;
145
146 /*
147 * Each policy declares a mask of object types requiring labels to be
148 * allocated for them. For convenience, we combine and cache the bitwise or
149 * of the per-policy object flags to track whether we will allocate a label
150 * for an object type at run-time.
151 */
152 uint64_t mac_labeled;
153 SYSCTL_UQUAD(_security_mac, OID_AUTO, labeled, CTLFLAG_RD, &mac_labeled, 0,
154 "Mask of object types being labeled");
155
156 MALLOC_DEFINE(M_MACTEMP, "mactemp", "MAC temporary label storage");
157
158 /*
159 * MAC policy modules are placed in one of two lists: mac_static_policy_list,
160 * for policies that are loaded early and cannot be unloaded, and
161 * mac_policy_list, which holds policies either loaded later in the boot
162 * cycle or that may be unloaded. The static policy list does not require
163 * locks to iterate over, but the dynamic list requires synchronization.
164 * Support for dynamic policy loading can be compiled out using the
165 * MAC_STATIC kernel option.
166 *
167 * The dynamic policy list is protected by two locks: modifying the list
168 * requires both locks to be held exclusively. One of the locks,
169 * mac_policy_rm, is acquired over policy entry points that will never sleep;
170 * the other, mac_policy_sx, is acquire over policy entry points that may
171 * sleep. The former category will be used when kernel locks may be held
172 * over calls to the MAC Framework, during network processing in ithreads,
173 * etc. The latter will tend to involve potentially blocking memory
174 * allocations, extended attribute I/O, etc.
175 */
176 #ifndef MAC_STATIC
177 static struct rmlock mac_policy_rm; /* Non-sleeping entry points. */
178 static struct sx mac_policy_sx; /* Sleeping entry points. */
179 #endif
180
181 struct mac_policy_list_head mac_policy_list;
182 struct mac_policy_list_head mac_static_policy_list;
183 u_int mac_policy_count; /* Registered policy count. */
184
185 static void mac_policy_xlock(void);
186 static void mac_policy_xlock_assert(void);
187 static void mac_policy_xunlock(void);
188
189 void
190 mac_policy_slock_nosleep(struct rm_priotracker *tracker)
191 {
192
193 #ifndef MAC_STATIC
194 if (!mac_late)
195 return;
196
197 rm_rlock(&mac_policy_rm, tracker);
198 #endif
199 }
200
201 void
202 mac_policy_slock_sleep(void)
203 {
204
205 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
206 "mac_policy_slock_sleep");
207
208 #ifndef MAC_STATIC
209 if (!mac_late)
210 return;
211
212 sx_slock(&mac_policy_sx);
213 #endif
214 }
215
216 void
217 mac_policy_sunlock_nosleep(struct rm_priotracker *tracker)
218 {
219
220 #ifndef MAC_STATIC
221 if (!mac_late)
222 return;
223
224 rm_runlock(&mac_policy_rm, tracker);
225 #endif
226 }
227
228 void
229 mac_policy_sunlock_sleep(void)
230 {
231
232 #ifndef MAC_STATIC
233 if (!mac_late)
234 return;
235
236 sx_sunlock(&mac_policy_sx);
237 #endif
238 }
239
240 static void
241 mac_policy_xlock(void)
242 {
243
244 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
245 "mac_policy_xlock()");
246
247 #ifndef MAC_STATIC
248 if (!mac_late)
249 return;
250
251 sx_xlock(&mac_policy_sx);
252 rm_wlock(&mac_policy_rm);
253 #endif
254 }
255
256 static void
257 mac_policy_xunlock(void)
258 {
259
260 #ifndef MAC_STATIC
261 if (!mac_late)
262 return;
263
264 rm_wunlock(&mac_policy_rm);
265 sx_xunlock(&mac_policy_sx);
266 #endif
267 }
268
269 static void
270 mac_policy_xlock_assert(void)
271 {
272
273 #ifndef MAC_STATIC
274 if (!mac_late)
275 return;
276
277 /* XXXRW: rm_assert(&mac_policy_rm, RA_WLOCKED); */
278 sx_assert(&mac_policy_sx, SA_XLOCKED);
279 #endif
280 }
281
282 /*
283 * Initialize the MAC subsystem, including appropriate SMP locks.
284 */
285 static void
286 mac_init(void)
287 {
288
289 LIST_INIT(&mac_static_policy_list);
290 LIST_INIT(&mac_policy_list);
291 mac_labelzone_init();
292
293 #ifndef MAC_STATIC
294 rm_init_flags(&mac_policy_rm, "mac_policy_rm", RM_NOWITNESS |
295 RM_RECURSE);
296 sx_init_flags(&mac_policy_sx, "mac_policy_sx", SX_NOWITNESS);
297 #endif
298 }
299
300 /*
301 * For the purposes of modules that want to know if they were loaded "early",
302 * set the mac_late flag once we've processed modules either linked into the
303 * kernel, or loaded before the kernel startup.
304 */
305 static void
306 mac_late_init(void)
307 {
308
309 mac_late = 1;
310 }
311
312 /*
313 * Given a policy, derive from its set of non-NULL label init methods what
314 * object types the policy is interested in.
315 */
316 static uint64_t
317 mac_policy_getlabeled(struct mac_policy_conf *mpc)
318 {
319 uint64_t labeled;
320
321 #define MPC_FLAG(method, flag) \
322 if (mpc->mpc_ops->mpo_ ## method != NULL) \
323 labeled |= (flag); \
324
325 labeled = 0;
326 MPC_FLAG(cred_init_label, MPC_OBJECT_CRED);
327 MPC_FLAG(proc_init_label, MPC_OBJECT_PROC);
328 MPC_FLAG(vnode_init_label, MPC_OBJECT_VNODE);
329 MPC_FLAG(inpcb_init_label, MPC_OBJECT_INPCB);
330 MPC_FLAG(socket_init_label, MPC_OBJECT_SOCKET);
331 MPC_FLAG(devfs_init_label, MPC_OBJECT_DEVFS);
332 MPC_FLAG(mbuf_init_label, MPC_OBJECT_MBUF);
333 MPC_FLAG(ipq_init_label, MPC_OBJECT_IPQ);
334 MPC_FLAG(ifnet_init_label, MPC_OBJECT_IFNET);
335 MPC_FLAG(bpfdesc_init_label, MPC_OBJECT_BPFDESC);
336 MPC_FLAG(pipe_init_label, MPC_OBJECT_PIPE);
337 MPC_FLAG(mount_init_label, MPC_OBJECT_MOUNT);
338 MPC_FLAG(posixsem_init_label, MPC_OBJECT_POSIXSEM);
339 MPC_FLAG(posixshm_init_label, MPC_OBJECT_POSIXSHM);
340 MPC_FLAG(sysvmsg_init_label, MPC_OBJECT_SYSVMSG);
341 MPC_FLAG(sysvmsq_init_label, MPC_OBJECT_SYSVMSQ);
342 MPC_FLAG(sysvsem_init_label, MPC_OBJECT_SYSVSEM);
343 MPC_FLAG(sysvshm_init_label, MPC_OBJECT_SYSVSHM);
344 MPC_FLAG(syncache_init_label, MPC_OBJECT_SYNCACHE);
345 MPC_FLAG(ip6q_init_label, MPC_OBJECT_IP6Q);
346
347 #undef MPC_FLAG
348 return (labeled);
349 }
350
351 /*
352 * When policies are loaded or unloaded, walk the list of registered policies
353 * and built mac_labeled, a bitmask representing the union of all objects
354 * requiring labels across all policies.
355 */
356 static void
357 mac_policy_update(void)
358 {
359 struct mac_policy_conf *mpc;
360
361 mac_policy_xlock_assert();
362
363 mac_labeled = 0;
364 mac_policy_count = 0;
365 LIST_FOREACH(mpc, &mac_static_policy_list, mpc_list) {
366 mac_labeled |= mac_policy_getlabeled(mpc);
367 mac_policy_count++;
368 }
369 LIST_FOREACH(mpc, &mac_policy_list, mpc_list) {
370 mac_labeled |= mac_policy_getlabeled(mpc);
371 mac_policy_count++;
372 }
373 }
374
375 static int
376 mac_policy_register(struct mac_policy_conf *mpc)
377 {
378 struct mac_policy_conf *tmpc;
379 int error, slot, static_entry;
380
381 error = 0;
382
383 /*
384 * We don't technically need exclusive access while !mac_late, but
385 * hold it for assertion consistency.
386 */
387 mac_policy_xlock();
388
389 /*
390 * If the module can potentially be unloaded, or we're loading late,
391 * we have to stick it in the non-static list and pay an extra
392 * performance overhead. Otherwise, we can pay a light locking cost
393 * and stick it in the static list.
394 */
395 static_entry = (!mac_late &&
396 !(mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK));
397
398 if (static_entry) {
399 LIST_FOREACH(tmpc, &mac_static_policy_list, mpc_list) {
400 if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) {
401 error = EEXIST;
402 goto out;
403 }
404 }
405 } else {
406 LIST_FOREACH(tmpc, &mac_policy_list, mpc_list) {
407 if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) {
408 error = EEXIST;
409 goto out;
410 }
411 }
412 }
413 if (mpc->mpc_field_off != NULL) {
414 slot = ffs(mac_slot_offsets_free);
415 if (slot == 0) {
416 error = ENOMEM;
417 goto out;
418 }
419 slot--;
420 mac_slot_offsets_free &= ~(1 << slot);
421 *mpc->mpc_field_off = slot;
422 }
423 mpc->mpc_runtime_flags |= MPC_RUNTIME_FLAG_REGISTERED;
424
425 /*
426 * If we're loading a MAC module after the framework has initialized,
427 * it has to go into the dynamic list. If we're loading it before
428 * we've finished initializing, it can go into the static list with
429 * weaker locker requirements.
430 */
431 if (static_entry)
432 LIST_INSERT_HEAD(&mac_static_policy_list, mpc, mpc_list);
433 else
434 LIST_INSERT_HEAD(&mac_policy_list, mpc, mpc_list);
435
436 /*
437 * Per-policy initialization. Currently, this takes place under the
438 * exclusive lock, so policies must not sleep in their init method.
439 * In the future, we may want to separate "init" from "start", with
440 * "init" occurring without the lock held. Likewise, on tear-down,
441 * breaking out "stop" from "destroy".
442 */
443 if (mpc->mpc_ops->mpo_init != NULL)
444 (*(mpc->mpc_ops->mpo_init))(mpc);
445 mac_policy_update();
446
447 SDT_PROBE1(mac, , policy, register, mpc);
448 printf("Security policy loaded: %s (%s)\n", mpc->mpc_fullname,
449 mpc->mpc_name);
450
451 out:
452 mac_policy_xunlock();
453 return (error);
454 }
455
456 static int
457 mac_policy_unregister(struct mac_policy_conf *mpc)
458 {
459
460 /*
461 * If we fail the load, we may get a request to unload. Check to see
462 * if we did the run-time registration, and if not, silently succeed.
463 */
464 mac_policy_xlock();
465 if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) == 0) {
466 mac_policy_xunlock();
467 return (0);
468 }
469 #if 0
470 /*
471 * Don't allow unloading modules with private data.
472 */
473 if (mpc->mpc_field_off != NULL) {
474 mac_policy_xunlock();
475 return (EBUSY);
476 }
477 #endif
478 /*
479 * Only allow the unload to proceed if the module is unloadable by
480 * its own definition.
481 */
482 if ((mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK) == 0) {
483 mac_policy_xunlock();
484 return (EBUSY);
485 }
486 if (mpc->mpc_ops->mpo_destroy != NULL)
487 (*(mpc->mpc_ops->mpo_destroy))(mpc);
488
489 LIST_REMOVE(mpc, mpc_list);
490 mpc->mpc_runtime_flags &= ~MPC_RUNTIME_FLAG_REGISTERED;
491 mac_policy_update();
492 mac_policy_xunlock();
493
494 SDT_PROBE1(mac, , policy, unregister, mpc);
495 printf("Security policy unload: %s (%s)\n", mpc->mpc_fullname,
496 mpc->mpc_name);
497
498 return (0);
499 }
500
501 /*
502 * Allow MAC policy modules to register during boot, etc.
503 */
504 int
505 mac_policy_modevent(module_t mod, int type, void *data)
506 {
507 struct mac_policy_conf *mpc;
508 int error;
509
510 error = 0;
511 mpc = (struct mac_policy_conf *) data;
512
513 #ifdef MAC_STATIC
514 if (mac_late) {
515 printf("mac_policy_modevent: MAC_STATIC and late\n");
516 return (EBUSY);
517 }
518 #endif
519
520 SDT_PROBE2(mac, , policy, modevent, type, mpc);
521 switch (type) {
522 case MOD_LOAD:
523 if (mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_NOTLATE &&
524 mac_late) {
525 printf("mac_policy_modevent: can't load %s policy "
526 "after booting\n", mpc->mpc_name);
527 error = EBUSY;
528 break;
529 }
530 error = mac_policy_register(mpc);
531 break;
532 case MOD_UNLOAD:
533 /* Don't unregister the module if it was never registered. */
534 if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED)
535 != 0)
536 error = mac_policy_unregister(mpc);
537 else
538 error = 0;
539 break;
540 default:
541 error = EOPNOTSUPP;
542 break;
543 }
544
545 return (error);
546 }
547
548 /*
549 * Define an error value precedence, and given two arguments, selects the
550 * value with the higher precedence.
551 */
552 int
553 mac_error_select(int error1, int error2)
554 {
555
556 /* Certain decision-making errors take top priority. */
557 if (error1 == EDEADLK || error2 == EDEADLK)
558 return (EDEADLK);
559
560 /* Invalid arguments should be reported where possible. */
561 if (error1 == EINVAL || error2 == EINVAL)
562 return (EINVAL);
563
564 /* Precedence goes to "visibility", with both process and file. */
565 if (error1 == ESRCH || error2 == ESRCH)
566 return (ESRCH);
567
568 if (error1 == ENOENT || error2 == ENOENT)
569 return (ENOENT);
570
571 /* Precedence goes to DAC/MAC protections. */
572 if (error1 == EACCES || error2 == EACCES)
573 return (EACCES);
574
575 /* Precedence goes to privilege. */
576 if (error1 == EPERM || error2 == EPERM)
577 return (EPERM);
578
579 /* Precedence goes to error over success; otherwise, arbitrary. */
580 if (error1 != 0)
581 return (error1);
582 return (error2);
583 }
584
585 int
586 mac_check_structmac_consistent(struct mac *mac)
587 {
588
589 if (mac->m_buflen > MAC_MAX_LABEL_BUF_LEN)
590 return (EINVAL);
591
592 return (0);
593 }
594
595 SYSINIT(mac, SI_SUB_MAC, SI_ORDER_FIRST, mac_init, NULL);
596 SYSINIT(mac_late, SI_SUB_MAC_LATE, SI_ORDER_FIRST, mac_late_init, NULL);
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