secmodel_extensions.c revision 1.4 
1/* $NetBSD: secmodel_extensions.c,v 1.4 2013/01/28 00:51:29 jym Exp $ */
2/*-
3 * Copyright (c) 2011 Elad Efrat <elad@NetBSD.org>
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 * 3. The name of the author may not be used to endorse or promote products
15 *    derived from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30__KERNEL_RCSID(0, "$NetBSD: secmodel_extensions.c,v 1.4 2013/01/28 00:51:29 jym Exp $");
31
32#include <sys/types.h>
33#include <sys/param.h>
34#include <sys/kauth.h>
35
36#include <sys/mount.h>
37#include <sys/vnode.h>
38#include <sys/socketvar.h>
39#include <sys/sysctl.h>
40#include <sys/proc.h>
41#include <sys/module.h>
42
43#include <secmodel/secmodel.h>
44#include <secmodel/extensions/extensions.h>
45
46MODULE(MODULE_CLASS_SECMODEL, extensions, NULL);
47
48static int dovfsusermount;
49static int curtain;
50static int user_set_cpu_affinity;
51
52static kauth_listener_t l_system, l_process, l_network;
53
54static secmodel_t extensions_sm;
55static struct sysctllog *extensions_sysctl_log;
56
57static void secmodel_extensions_init(void);
58static void secmodel_extensions_start(void);
59static void secmodel_extensions_stop(void);
60
61static void sysctl_security_extensions_setup(struct sysctllog **);
62static int  sysctl_extensions_user_handler(SYSCTLFN_PROTO);
63static int  sysctl_extensions_curtain_handler(SYSCTLFN_PROTO);
64static bool is_securelevel_above(int);
65
66static int secmodel_extensions_system_cb(kauth_cred_t, kauth_action_t,
67    void *, void *, void *, void *, void *);
68static int secmodel_extensions_process_cb(kauth_cred_t, kauth_action_t,
69    void *, void *, void *, void *, void *);
70static int secmodel_extensions_network_cb(kauth_cred_t, kauth_action_t,
71    void *, void *, void *, void *, void *);
72
73static void
74sysctl_security_extensions_setup(struct sysctllog **clog)
75{
76	const struct sysctlnode *rnode, *rnode2;
77
78	sysctl_createv(clog, 0, NULL, &rnode,
79		       CTLFLAG_PERMANENT,
80		       CTLTYPE_NODE, "security", NULL,
81		       NULL, 0, NULL, 0,
82		       CTL_SECURITY, CTL_EOL);
83
84	sysctl_createv(clog, 0, &rnode, &rnode,
85		       CTLFLAG_PERMANENT,
86		       CTLTYPE_NODE, "models", NULL,
87		       NULL, 0, NULL, 0,
88		       CTL_CREATE, CTL_EOL);
89
90	/* Compatibility: security.models.bsd44 */
91	rnode2 = rnode;
92	sysctl_createv(clog, 0, &rnode2, &rnode2,
93		       CTLFLAG_PERMANENT,
94		       CTLTYPE_NODE, "bsd44", NULL,
95		       NULL, 0, NULL, 0,
96		       CTL_CREATE, CTL_EOL);
97
98        /* Compatibility: security.models.bsd44.curtain */
99	sysctl_createv(clog, 0, &rnode2, NULL,
100		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
101		       CTLTYPE_INT, "curtain",
102		       SYSCTL_DESCR("Curtain information about objects to "\
103		       		    "users not owning them."),
104		       sysctl_extensions_curtain_handler, 0, &curtain, 0,
105		       CTL_CREATE, CTL_EOL);
106
107	sysctl_createv(clog, 0, &rnode, &rnode,
108		       CTLFLAG_PERMANENT,
109		       CTLTYPE_NODE, "extensions", NULL,
110		       NULL, 0, NULL, 0,
111		       CTL_CREATE, CTL_EOL);
112
113	sysctl_createv(clog, 0, &rnode, NULL,
114		       CTLFLAG_PERMANENT,
115		       CTLTYPE_STRING, "name", NULL,
116		       NULL, 0, __UNCONST(SECMODEL_EXTENSIONS_NAME), 0,
117		       CTL_CREATE, CTL_EOL);
118
119	sysctl_createv(clog, 0, &rnode, NULL,
120		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
121		       CTLTYPE_INT, "usermount",
122		       SYSCTL_DESCR("Whether unprivileged users may mount "
123				    "filesystems"),
124		       sysctl_extensions_user_handler, 0, &dovfsusermount, 0,
125		       CTL_CREATE, CTL_EOL);
126
127	sysctl_createv(clog, 0, &rnode, NULL,
128		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
129		       CTLTYPE_INT, "curtain",
130		       SYSCTL_DESCR("Curtain information about objects to "\
131		       		    "users not owning them."),
132		       sysctl_extensions_curtain_handler, 0, &curtain, 0,
133		       CTL_CREATE, CTL_EOL);
134
135	sysctl_createv(clog, 0, &rnode, NULL,
136		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
137		       CTLTYPE_INT, "user_set_cpu_affinity",
138		       SYSCTL_DESCR("Whether unprivileged users may control "\
139		       		    "CPU affinity."),
140		       sysctl_extensions_user_handler, 0,
141		       &user_set_cpu_affinity, 0,
142		       CTL_CREATE, CTL_EOL);
143
144	/* Compatibility: vfs.generic.usermount */
145	sysctl_createv(clog, 0, NULL, NULL,
146		       CTLFLAG_PERMANENT,
147		       CTLTYPE_NODE, "vfs", NULL,
148		       NULL, 0, NULL, 0,
149		       CTL_VFS, CTL_EOL);
150
151	sysctl_createv(clog, 0, NULL, NULL,
152		       CTLFLAG_PERMANENT,
153		       CTLTYPE_NODE, "generic",
154		       SYSCTL_DESCR("Non-specific vfs related information"),
155		       NULL, 0, NULL, 0,
156		       CTL_VFS, VFS_GENERIC, CTL_EOL);
157
158	sysctl_createv(clog, 0, NULL, NULL,
159		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
160		       CTLTYPE_INT, "usermount",
161		       SYSCTL_DESCR("Whether unprivileged users may mount "
162				    "filesystems"),
163		       sysctl_extensions_user_handler, 0, &dovfsusermount, 0,
164		       CTL_VFS, VFS_GENERIC, VFS_USERMOUNT, CTL_EOL);
165
166	/* Compatibility: security.curtain */
167	sysctl_createv(clog, 0, NULL, &rnode,
168		       CTLFLAG_PERMANENT,
169		       CTLTYPE_NODE, "security", NULL,
170		       NULL, 0, NULL, 0,
171		       CTL_SECURITY, CTL_EOL);
172
173	sysctl_createv(clog, 0, &rnode, NULL,
174		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
175		       CTLTYPE_INT, "curtain",
176		       SYSCTL_DESCR("Curtain information about objects to "\
177		       		    "users not owning them."),
178		       sysctl_extensions_curtain_handler, 0, &curtain, 0,
179		       CTL_CREATE, CTL_EOL);
180}
181
182static int
183sysctl_extensions_curtain_handler(SYSCTLFN_ARGS)
184{
185	struct sysctlnode node;
186	int val, error;
187
188	val = *(int *)rnode->sysctl_data;
189
190	node = *rnode;
191	node.sysctl_data = &val;
192
193	error = sysctl_lookup(SYSCTLFN_CALL(&node));
194	if (error || newp == NULL)
195		return error;
196
197	/* shortcut */
198	if (val == *(int *)rnode->sysctl_data)
199		return 0;
200
201	/* curtain cannot be disabled when securelevel is above 0 */
202	if (val == 0 && is_securelevel_above(0)) {
203		return EPERM;
204	}
205
206	*(int *)rnode->sysctl_data = val;
207	return 0;
208}
209
210/*
211 * Generic sysctl extensions handler for user mount and set CPU affinity
212 * rights. Checks the following conditions:
213 * - setting value to 0 is always permitted (decrease user rights)
214 * - setting value != 0 is not permitted when securelevel is above 0 (increase
215 *   user rights).
216 */
217static int
218sysctl_extensions_user_handler(SYSCTLFN_ARGS)
219{
220	struct sysctlnode node;
221	int val, error;
222
223	val = *(int *)rnode->sysctl_data;
224
225	node = *rnode;
226	node.sysctl_data = &val;
227
228	error = sysctl_lookup(SYSCTLFN_CALL(&node));
229	if (error || newp == NULL)
230		return error;
231
232	/* shortcut */
233	if (val == *(int *)rnode->sysctl_data)
234		return 0;
235
236	/* we cannot grant more rights to users when securelevel is above 0 */
237	if (val != 0 && is_securelevel_above(0)) {
238		return EPERM;
239	}
240
241	*(int *)rnode->sysctl_data = val;
242	return 0;
243}
244
245/*
246 * Query secmodel_securelevel(9) to know whether securelevel is strictly
247 * above 'level' or not.
248 * Returns true if it is, false otherwise (when securelevel is absent or
249 * securelevel is at or below 'level').
250 */
251static bool
252is_securelevel_above(int level)
253{
254	bool above;
255	int error;
256
257	error = secmodel_eval("org.netbsd.secmodel.securelevel",
258	    "is-securelevel-above", KAUTH_ARG(level), &above);
259	if (error == 0 && above)
260		return true;
261	else
262		return false;
263}
264
265static void
266secmodel_extensions_init(void)
267{
268
269	curtain = 0;
270	user_set_cpu_affinity = 0;
271}
272
273static void
274secmodel_extensions_start(void)
275{
276
277	l_system = kauth_listen_scope(KAUTH_SCOPE_SYSTEM,
278	    secmodel_extensions_system_cb, NULL);
279	l_process = kauth_listen_scope(KAUTH_SCOPE_PROCESS,
280	    secmodel_extensions_process_cb, NULL);
281	l_network = kauth_listen_scope(KAUTH_SCOPE_NETWORK,
282	    secmodel_extensions_network_cb, NULL);
283}
284
285static void
286secmodel_extensions_stop(void)
287{
288
289	kauth_unlisten_scope(l_system);
290	kauth_unlisten_scope(l_process);
291	kauth_unlisten_scope(l_network);
292}
293
294static int
295extensions_modcmd(modcmd_t cmd, void *arg)
296{
297	int error = 0;
298
299	switch (cmd) {
300	case MODULE_CMD_INIT:
301		error = secmodel_register(&extensions_sm,
302		    SECMODEL_EXTENSIONS_ID, SECMODEL_EXTENSIONS_NAME,
303		    NULL, NULL, NULL);
304		if (error != 0)
305			printf("extensions_modcmd::init: secmodel_register "
306			    "returned %d\n", error);
307
308		secmodel_extensions_init();
309		secmodel_extensions_start();
310		sysctl_security_extensions_setup(&extensions_sysctl_log);
311		break;
312
313	case MODULE_CMD_FINI:
314		sysctl_teardown(&extensions_sysctl_log);
315		secmodel_extensions_stop();
316
317		error = secmodel_deregister(extensions_sm);
318		if (error != 0)
319			printf("extensions_modcmd::fini: secmodel_deregister "
320			    "returned %d\n", error);
321
322		break;
323
324	case MODULE_CMD_AUTOUNLOAD:
325		error = EPERM;
326		break;
327
328	default:
329		error = ENOTTY;
330		break;
331	}
332
333	return (error);
334}
335
336static int
337secmodel_extensions_system_cb(kauth_cred_t cred, kauth_action_t action,
338    void *cookie, void *arg0, void *arg1, void *arg2, void *arg3)
339{
340	vnode_t *vp;
341	struct vattr va;
342	struct mount *mp;
343	u_long flags;
344	int result;
345	enum kauth_system_req req;
346	int error;
347
348	req = (enum kauth_system_req)arg0;
349	result = KAUTH_RESULT_DEFER;
350
351	if (action != KAUTH_SYSTEM_MOUNT || dovfsusermount == 0)
352		return result;
353
354	switch (req) {
355	case KAUTH_REQ_SYSTEM_MOUNT_NEW:
356		vp = (vnode_t *)arg1;
357		mp = vp->v_mount;
358		flags = (u_long)arg2;
359
360		/*
361		 * Ensure that the user owns the directory onto which the
362		 * mount is attempted.
363		 */
364		vn_lock(vp, LK_SHARED | LK_RETRY);
365		error = VOP_GETATTR(vp, &va, cred);
366		VOP_UNLOCK(vp);
367		if (error)
368			break;
369
370		if (va.va_uid != kauth_cred_geteuid(cred))
371			break;
372
373		error = usermount_common_policy(mp, flags);
374		if (error)
375			break;
376
377		result = KAUTH_RESULT_ALLOW;
378
379		break;
380
381	case KAUTH_REQ_SYSTEM_MOUNT_UNMOUNT:
382		mp = arg1;
383
384		/* Must own the mount. */
385		if (mp->mnt_stat.f_owner == kauth_cred_geteuid(cred))
386			result = KAUTH_RESULT_ALLOW;
387
388		break;
389
390	case KAUTH_REQ_SYSTEM_MOUNT_UPDATE:
391		mp = arg1;
392		flags = (u_long)arg2;
393
394		/* Must own the mount. */
395		if (mp->mnt_stat.f_owner == kauth_cred_geteuid(cred) &&
396		    usermount_common_policy(mp, flags) == 0)
397			result = KAUTH_RESULT_ALLOW;
398
399		break;
400
401	default:
402		break;
403	}
404
405	return (result);
406}
407
408static int
409secmodel_extensions_process_cb(kauth_cred_t cred, kauth_action_t action,
410    void *cookie, void *arg0, void *arg1, void *arg2, void *arg3)
411{
412	int result;
413	enum kauth_process_req req;
414
415	result = KAUTH_RESULT_DEFER;
416	req = (enum kauth_process_req)arg1;
417
418	switch (action) {
419	case KAUTH_PROCESS_CANSEE:
420		switch (req) {
421		case KAUTH_REQ_PROCESS_CANSEE_ARGS:
422		case KAUTH_REQ_PROCESS_CANSEE_ENTRY:
423		case KAUTH_REQ_PROCESS_CANSEE_OPENFILES:
424			if (curtain != 0) {
425				struct proc *p = arg0;
426
427				/*
428				 * Only process' owner and root can see
429				 * through curtain
430				 */
431				if (!kauth_cred_uidmatch(cred, p->p_cred)) {
432					int error;
433					bool isroot = false;
434
435					error = secmodel_eval(
436					    "org.netbsd.secmodel.suser",
437					    "is-root", cred, &isroot);
438					if (error == 0 && !isroot)
439						result = KAUTH_RESULT_DENY;
440				}
441			}
442
443			break;
444
445		default:
446			break;
447		}
448
449		break;
450
451	case KAUTH_PROCESS_SCHEDULER_SETAFFINITY:
452		if (user_set_cpu_affinity != 0) {
453			struct proc *p = arg0;
454
455			if (kauth_cred_uidmatch(cred, p->p_cred))
456				result = KAUTH_RESULT_ALLOW;
457		}
458		break;
459
460	default:
461		break;
462	}
463
464	return (result);
465}
466
467static int
468secmodel_extensions_network_cb(kauth_cred_t cred, kauth_action_t action,
469    void *cookie, void *arg0, void *arg1, void *arg2, void *arg3)
470{
471	int result;
472	enum kauth_network_req req;
473
474	result = KAUTH_RESULT_DEFER;
475	req = (enum kauth_network_req)arg0;
476
477	if (action != KAUTH_NETWORK_SOCKET ||
478	    req != KAUTH_REQ_NETWORK_SOCKET_CANSEE)
479		return result;
480
481	if (curtain != 0) {
482		struct socket *so = (struct socket *)arg1;
483
484		if (!kauth_cred_uidmatch(cred, so->so_cred)) {
485			int error;
486			bool isroot = false;
487
488			error = secmodel_eval("org.netbsd.secmodel.suser",
489			    "is-root", cred, &isroot);
490			if (error == 0 && !isroot)
491				result = KAUTH_RESULT_DENY;
492		}
493	}
494
495	return (result);
496}
497