1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
|
/*-
* Copyright (c) 1999-2002, 2006, 2009 Robert N. M. Watson
* Copyright (c) 2001 Ilmar S. Habibulin
* Copyright (c) 2001-2005 Networks Associates Technology, Inc.
* Copyright (c) 2005-2006 SPARTA, Inc.
* Copyright (c) 2008-2009 Apple Inc.
* All rights reserved.
*
* This software was developed by Robert Watson and Ilmar Habibulin for the
* TrustedBSD Project.
*
* This software was developed for the FreeBSD Project in part by Network
* Associates Laboratories, the Security Research Division of Network
* Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
* as part of the DARPA CHATS research program.
*
* This software was enhanced by SPARTA ISSO under SPAWAR contract
* N66001-04-C-6019 ("SEFOS").
*
* This software was developed at the University of Cambridge Computer
* Laboratory with support from a grant from Google, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*-
* Framework for extensible kernel access control. This file contains core
* kernel infrastructure for the TrustedBSD MAC Framework, including policy
* registration, versioning, locking, error composition operator, and system
* calls.
*
* The MAC Framework implements three programming interfaces:
*
* - The kernel MAC interface, defined in mac_framework.h, and invoked
* throughout the kernel to request security decisions, notify of security
* related events, etc.
*
* - The MAC policy module interface, defined in mac_policy.h, which is
* implemented by MAC policy modules and invoked by the MAC Framework to
* forward kernel security requests and notifications to policy modules.
*
* - The user MAC API, defined in mac.h, which allows user programs to query
* and set label state on objects.
*
* The majority of the MAC Framework implementation may be found in
* src/sys/security/mac. Sample policy modules may be found in
* src/sys/security/mac_*.
*/
#include "opt_kdtrace.h"
#include "opt_mac.h"
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/condvar.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mac.h>
#include <sys/module.h>
#include <sys/rwlock.h>
#include <sys/sdt.h>
#include <sys/sx.h>
#include <sys/systm.h>
#include <sys/sysctl.h>
#include <security/mac/mac_framework.h>
#include <security/mac/mac_internal.h>
#include <security/mac/mac_policy.h>
/*
* DTrace SDT providers for MAC.
*/
SDT_PROVIDER_DEFINE(mac);
SDT_PROVIDER_DEFINE(mac_framework);
SDT_PROBE_DEFINE2(mac, kernel, policy, modevent, "int",
"struct mac_policy_conf *mpc");
SDT_PROBE_DEFINE1(mac, kernel, policy, register, "struct mac_policy_conf *");
SDT_PROBE_DEFINE1(mac, kernel, policy, unregister, "struct mac_policy_conf *");
/*
* Root sysctl node for all MAC and MAC policy controls.
*/
SYSCTL_NODE(_security, OID_AUTO, mac, CTLFLAG_RW, 0,
"TrustedBSD MAC policy controls");
/*
* Declare that the kernel provides MAC support, version 3 (FreeBSD 7.x).
* This permits modules to refuse to be loaded if the necessary support isn't
* present, even if it's pre-boot.
*/
MODULE_VERSION(kernel_mac_support, MAC_VERSION);
static unsigned int mac_version = MAC_VERSION;
SYSCTL_UINT(_security_mac, OID_AUTO, version, CTLFLAG_RD, &mac_version, 0,
"");
/*
* Labels consist of a indexed set of "slots", which are allocated policies
* as required. The MAC Framework maintains a bitmask of slots allocated so
* far to prevent reuse. Slots cannot be reused, as the MAC Framework
* guarantees that newly allocated slots in labels will be NULL unless
* otherwise initialized, and because we do not have a mechanism to garbage
* collect slots on policy unload. As labeled policies tend to be statically
* loaded during boot, and not frequently unloaded and reloaded, this is not
* generally an issue.
*/
#if MAC_MAX_SLOTS > 32
#error "MAC_MAX_SLOTS too large"
#endif
static unsigned int mac_max_slots = MAC_MAX_SLOTS;
static unsigned int mac_slot_offsets_free = (1 << MAC_MAX_SLOTS) - 1;
SYSCTL_UINT(_security_mac, OID_AUTO, max_slots, CTLFLAG_RD, &mac_max_slots,
0, "");
/*
* Has the kernel started generating labeled objects yet? All read/write
* access to this variable is serialized during the boot process. Following
* the end of serialization, we don't update this flag; no locking.
*/
static int mac_late = 0;
/*
* Each policy declares a mask of object types requiring labels to be
* allocated for them. For convenience, we combine and cache the bitwise or
* of the per-policy object flags to track whether we will allocate a label
* for an object type at run-time.
*/
uint64_t mac_labeled;
SYSCTL_QUAD(_security_mac, OID_AUTO, labeled, CTLFLAG_RD, &mac_labeled, 0,
"Mask of object types being labeled");
MALLOC_DEFINE(M_MACTEMP, "mactemp", "MAC temporary label storage");
/*
* MAC policy modules are placed in one of two lists: mac_static_policy_list,
* for policies that are loaded early and cannot be unloaded, and
* mac_policy_list, which holds policies either loaded later in the boot
* cycle or that may be unloaded. The static policy list does not require
* locks to iterate over, but the dynamic list requires synchronization.
* Support for dynamic policy loading can be compiled out using the
* MAC_STATIC kernel option.
*
* The dynamic policy list is protected by two locks: modifying the list
* requires both locks to be held exclusively. One of the locks,
* mac_policy_rw, is acquired over policy entry points that will never sleep;
* the other, mac_policy_sx, is acquire over policy entry points that may
* sleep. The former category will be used when kernel locks may be held
* over calls to the MAC Framework, during network processing in ithreads,
* etc. The latter will tend to involve potentially blocking memory
* allocations, extended attribute I/O, etc.
*/
#ifndef MAC_STATIC
static struct rwlock mac_policy_rw; /* Non-sleeping entry points. */
static struct sx mac_policy_sx; /* Sleeping entry points. */
#endif
struct mac_policy_list_head mac_policy_list;
struct mac_policy_list_head mac_static_policy_list;
static void mac_policy_xlock(void);
static void mac_policy_xlock_assert(void);
static void mac_policy_xunlock(void);
void
mac_policy_slock_nosleep(void)
{
#ifndef MAC_STATIC
if (!mac_late)
return;
rw_rlock(&mac_policy_rw);
#endif
}
void
mac_policy_slock_sleep(void)
{
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
"mac_policy_slock_sleep");
#ifndef MAC_STATIC
if (!mac_late)
return;
sx_slock(&mac_policy_sx);
#endif
}
void
mac_policy_sunlock_nosleep(void)
{
#ifndef MAC_STATIC
if (!mac_late)
return;
rw_runlock(&mac_policy_rw);
#endif
}
void
mac_policy_sunlock_sleep(void)
{
#ifndef MAC_STATIC
if (!mac_late)
return;
sx_sunlock(&mac_policy_sx);
#endif
}
static void
mac_policy_xlock(void)
{
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
"mac_policy_xlock()");
#ifndef MAC_STATIC
if (!mac_late)
return;
sx_xlock(&mac_policy_sx);
rw_wlock(&mac_policy_rw);
#endif
}
static void
mac_policy_xunlock(void)
{
#ifndef MAC_STATIC
if (!mac_late)
return;
rw_wunlock(&mac_policy_rw);
sx_xunlock(&mac_policy_sx);
#endif
}
static void
mac_policy_xlock_assert(void)
{
#ifndef MAC_STATIC
if (!mac_late)
return;
rw_assert(&mac_policy_rw, RA_WLOCKED);
sx_assert(&mac_policy_sx, SA_XLOCKED);
#endif
}
/*
* Initialize the MAC subsystem, including appropriate SMP locks.
*/
static void
mac_init(void)
{
LIST_INIT(&mac_static_policy_list);
LIST_INIT(&mac_policy_list);
mac_labelzone_init();
#ifndef MAC_STATIC
rw_init(&mac_policy_rw, "mac_policy_rw");
sx_init(&mac_policy_sx, "mac_policy_sx");
#endif
}
/*
* For the purposes of modules that want to know if they were loaded "early",
* set the mac_late flag once we've processed modules either linked into the
* kernel, or loaded before the kernel startup.
*/
static void
mac_late_init(void)
{
mac_late = 1;
}
/*
* Given a policy, derive from its set of non-NULL label init methods what
* object types the policy is interested in.
*/
static uint64_t
mac_policy_getlabeled(struct mac_policy_conf *mpc)
{
uint64_t labeled;
#define MPC_FLAG(method, flag) \
if (mpc->mpc_ops->mpo_ ## method != NULL) \
labeled |= (flag); \
labeled = 0;
MPC_FLAG(cred_init_label, MPC_OBJECT_CRED);
MPC_FLAG(proc_init_label, MPC_OBJECT_PROC);
MPC_FLAG(vnode_init_label, MPC_OBJECT_VNODE);
MPC_FLAG(inpcb_init_label, MPC_OBJECT_INPCB);
MPC_FLAG(socket_init_label, MPC_OBJECT_SOCKET);
MPC_FLAG(devfs_init_label, MPC_OBJECT_DEVFS);
MPC_FLAG(mbuf_init_label, MPC_OBJECT_MBUF);
MPC_FLAG(ipq_init_label, MPC_OBJECT_IPQ);
MPC_FLAG(ifnet_init_label, MPC_OBJECT_IFNET);
MPC_FLAG(bpfdesc_init_label, MPC_OBJECT_BPFDESC);
MPC_FLAG(pipe_init_label, MPC_OBJECT_PIPE);
MPC_FLAG(mount_init_label, MPC_OBJECT_MOUNT);
MPC_FLAG(posixsem_init_label, MPC_OBJECT_POSIXSEM);
MPC_FLAG(posixshm_init_label, MPC_OBJECT_POSIXSHM);
MPC_FLAG(sysvmsg_init_label, MPC_OBJECT_SYSVMSG);
MPC_FLAG(sysvmsq_init_label, MPC_OBJECT_SYSVMSQ);
MPC_FLAG(sysvsem_init_label, MPC_OBJECT_SYSVSEM);
MPC_FLAG(sysvshm_init_label, MPC_OBJECT_SYSVSHM);
MPC_FLAG(syncache_init_label, MPC_OBJECT_SYNCACHE);
MPC_FLAG(ip6q_init_label, MPC_OBJECT_IP6Q);
#undef MPC_FLAG
return (labeled);
}
/*
* When policies are loaded or unloaded, walk the list of registered policies
* and built mac_labeled, a bitmask representing the union of all objects
* requiring labels across all policies.
*/
static void
mac_policy_updateflags(void)
{
struct mac_policy_conf *mpc;
mac_policy_xlock_assert();
mac_labeled = 0;
LIST_FOREACH(mpc, &mac_static_policy_list, mpc_list)
mac_labeled |= mac_policy_getlabeled(mpc);
LIST_FOREACH(mpc, &mac_policy_list, mpc_list)
mac_labeled |= mac_policy_getlabeled(mpc);
}
static int
mac_policy_register(struct mac_policy_conf *mpc)
{
struct mac_policy_conf *tmpc;
int error, slot, static_entry;
error = 0;
/*
* We don't technically need exclusive access while !mac_late, but
* hold it for assertion consistency.
*/
mac_policy_xlock();
/*
* If the module can potentially be unloaded, or we're loading late,
* we have to stick it in the non-static list and pay an extra
* performance overhead. Otherwise, we can pay a light locking cost
* and stick it in the static list.
*/
static_entry = (!mac_late &&
!(mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK));
if (static_entry) {
LIST_FOREACH(tmpc, &mac_static_policy_list, mpc_list) {
if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) {
error = EEXIST;
goto out;
}
}
} else {
LIST_FOREACH(tmpc, &mac_policy_list, mpc_list) {
if (strcmp(tmpc->mpc_name, mpc->mpc_name) == 0) {
error = EEXIST;
goto out;
}
}
}
if (mpc->mpc_field_off != NULL) {
slot = ffs(mac_slot_offsets_free);
if (slot == 0) {
error = ENOMEM;
goto out;
}
slot--;
mac_slot_offsets_free &= ~(1 << slot);
*mpc->mpc_field_off = slot;
}
mpc->mpc_runtime_flags |= MPC_RUNTIME_FLAG_REGISTERED;
/*
* If we're loading a MAC module after the framework has initialized,
* it has to go into the dynamic list. If we're loading it before
* we've finished initializing, it can go into the static list with
* weaker locker requirements.
*/
if (static_entry)
LIST_INSERT_HEAD(&mac_static_policy_list, mpc, mpc_list);
else
LIST_INSERT_HEAD(&mac_policy_list, mpc, mpc_list);
/*
* Per-policy initialization. Currently, this takes place under the
* exclusive lock, so policies must not sleep in their init method.
* In the future, we may want to separate "init" from "start", with
* "init" occuring without the lock held. Likewise, on tear-down,
* breaking out "stop" from "destroy".
*/
if (mpc->mpc_ops->mpo_init != NULL)
(*(mpc->mpc_ops->mpo_init))(mpc);
mac_policy_updateflags();
SDT_PROBE(mac, kernel, policy, register, mpc, 0, 0, 0, 0);
printf("Security policy loaded: %s (%s)\n", mpc->mpc_fullname,
mpc->mpc_name);
out:
mac_policy_xunlock();
return (error);
}
static int
mac_policy_unregister(struct mac_policy_conf *mpc)
{
/*
* If we fail the load, we may get a request to unload. Check to see
* if we did the run-time registration, and if not, silently succeed.
*/
mac_policy_xlock();
if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED) == 0) {
mac_policy_xunlock();
return (0);
}
#if 0
/*
* Don't allow unloading modules with private data.
*/
if (mpc->mpc_field_off != NULL) {
mac_policy_xunlock();
return (EBUSY);
}
#endif
/*
* Only allow the unload to proceed if the module is unloadable by
* its own definition.
*/
if ((mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_UNLOADOK) == 0) {
mac_policy_xunlock();
return (EBUSY);
}
if (mpc->mpc_ops->mpo_destroy != NULL)
(*(mpc->mpc_ops->mpo_destroy))(mpc);
LIST_REMOVE(mpc, mpc_list);
mpc->mpc_runtime_flags &= ~MPC_RUNTIME_FLAG_REGISTERED;
mac_policy_updateflags();
mac_policy_xunlock();
SDT_PROBE(mac, kernel, policy, unregister, mpc, 0, 0, 0, 0);
printf("Security policy unload: %s (%s)\n", mpc->mpc_fullname,
mpc->mpc_name);
return (0);
}
/*
* Allow MAC policy modules to register during boot, etc.
*/
int
mac_policy_modevent(module_t mod, int type, void *data)
{
struct mac_policy_conf *mpc;
int error;
error = 0;
mpc = (struct mac_policy_conf *) data;
#ifdef MAC_STATIC
if (mac_late) {
printf("mac_policy_modevent: MAC_STATIC and late\n");
return (EBUSY);
}
#endif
SDT_PROBE(mac, kernel, policy, modevent, type, mpc, 0, 0, 0);
switch (type) {
case MOD_LOAD:
if (mpc->mpc_loadtime_flags & MPC_LOADTIME_FLAG_NOTLATE &&
mac_late) {
printf("mac_policy_modevent: can't load %s policy "
"after booting\n", mpc->mpc_name);
error = EBUSY;
break;
}
error = mac_policy_register(mpc);
break;
case MOD_UNLOAD:
/* Don't unregister the module if it was never registered. */
if ((mpc->mpc_runtime_flags & MPC_RUNTIME_FLAG_REGISTERED)
!= 0)
error = mac_policy_unregister(mpc);
else
error = 0;
break;
default:
error = EOPNOTSUPP;
break;
}
return (error);
}
/*
* Define an error value precedence, and given two arguments, selects the
* value with the higher precedence.
*/
int
mac_error_select(int error1, int error2)
{
/* Certain decision-making errors take top priority. */
if (error1 == EDEADLK || error2 == EDEADLK)
return (EDEADLK);
/* Invalid arguments should be reported where possible. */
if (error1 == EINVAL || error2 == EINVAL)
return (EINVAL);
/* Precedence goes to "visibility", with both process and file. */
if (error1 == ESRCH || error2 == ESRCH)
return (ESRCH);
if (error1 == ENOENT || error2 == ENOENT)
return (ENOENT);
/* Precedence goes to DAC/MAC protections. */
if (error1 == EACCES || error2 == EACCES)
return (EACCES);
/* Precedence goes to privilege. */
if (error1 == EPERM || error2 == EPERM)
return (EPERM);
/* Precedence goes to error over success; otherwise, arbitrary. */
if (error1 != 0)
return (error1);
return (error2);
}
int
mac_check_structmac_consistent(struct mac *mac)
{
if (mac->m_buflen < 0 ||
mac->m_buflen > MAC_MAX_LABEL_BUF_LEN)
return (EINVAL);
return (0);
}
SYSINIT(mac, SI_SUB_MAC, SI_ORDER_FIRST, mac_init, NULL);
SYSINIT(mac_late, SI_SUB_MAC_LATE, SI_ORDER_FIRST, mac_late_init, NULL);
|