1 /*-
2 * Copyright (c) 2003-2004 Networks Associates Technology, Inc.
3 * Copyright (c) 2006 SPARTA, Inc.
4 * All rights reserved.
5 *
6 * This software was developed for the FreeBSD Project by Network
7 * Associates Laboratories, the Security Research Division of Network
8 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
9 * as part of the DARPA CHATS research program.
10 *
11 * This software was enhanced by SPARTA ISSO under SPAWAR contract
12 * N66001-04-C-6019 ("SEFOS").
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
16 * are met:
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 * 2. Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in the
21 * documentation and/or other materials provided with the distribution.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 *
35 * $FreeBSD: releng/11.0/sys/security/mac_portacl/mac_portacl.c 267992 2014-06-28 03:56:17Z hselasky $
36 */
37
38 /*
39 * Developed by the TrustedBSD Project.
40 *
41 * Administratively limit access to local UDP/TCP ports for binding purposes.
42 * Intended to be combined with net.inet.ip.portrange.reservedhigh to allow
43 * specific uids and gids to bind specific ports for specific purposes,
44 * while not opening the door to any user replacing an "official" service
45 * while you're restarting it. This only affects ports explicitly bound by
46 * the user process (either for listen/outgoing socket for TCP, or send/
47 * receive for UDP). This module will not limit ports bound implicitly for
48 * out-going connections where the process hasn't explicitly selected a port:
49 * these are automatically selected by the IP stack.
50 *
51 * To use this module, security.mac.enforce_socket must be enabled, and you
52 * will probably want to twiddle the net.inet sysctl listed above. Then use
53 * sysctl(8) to modify the rules string:
54 *
55 * # sysctl security.mac.portacl.rules="uid:425:tcp:80,uid:425:tcp:79"
56 *
57 * This ruleset, for example, permits uid 425 to bind TCP ports 80 (http) and
58 * 79 (finger). User names and group names can't be used directly because
59 * the kernel only knows about uids and gids.
60 */
61
62 #include <sys/param.h>
63 #include <sys/domain.h>
64 #include <sys/kernel.h>
65 #include <sys/lock.h>
66 #include <sys/malloc.h>
67 #include <sys/module.h>
68 #include <sys/mutex.h>
69 #include <sys/priv.h>
70 #include <sys/proc.h>
71 #include <sys/protosw.h>
72 #include <sys/queue.h>
73 #include <sys/systm.h>
74 #include <sys/sbuf.h>
75 #include <sys/socket.h>
76 #include <sys/socketvar.h>
77 #include <sys/sysctl.h>
78
79 #include <netinet/in.h>
80 #include <netinet/in_pcb.h>
81
82 #include <security/mac/mac_policy.h>
83
84 SYSCTL_DECL(_security_mac);
85
86 static SYSCTL_NODE(_security_mac, OID_AUTO, portacl, CTLFLAG_RW, 0,
87 "TrustedBSD mac_portacl policy controls");
88
89 static int portacl_enabled = 1;
90 SYSCTL_INT(_security_mac_portacl, OID_AUTO, enabled, CTLFLAG_RWTUN,
91 &portacl_enabled, 0, "Enforce portacl policy");
92
93 static int portacl_suser_exempt = 1;
94 SYSCTL_INT(_security_mac_portacl, OID_AUTO, suser_exempt, CTLFLAG_RWTUN,
95 &portacl_suser_exempt, 0, "Privilege permits binding of any port");
96
97 static int portacl_autoport_exempt = 1;
98 SYSCTL_INT(_security_mac_portacl, OID_AUTO, autoport_exempt, CTLFLAG_RWTUN,
99 &portacl_autoport_exempt, 0, "Allow automatic allocation through "
100 "binding port 0 if not IP_PORTRANGELOW");
101
102 static int portacl_port_high = 1023;
103 SYSCTL_INT(_security_mac_portacl, OID_AUTO, port_high, CTLFLAG_RWTUN,
104 &portacl_port_high, 0, "Highest port to enforce for");
105
106 static MALLOC_DEFINE(M_PORTACL, "portacl_rule", "Rules for mac_portacl");
107
108 #define MAC_RULE_STRING_LEN 1024
109
110 #define RULE_GID 1
111 #define RULE_UID 2
112 #define RULE_PROTO_TCP 1
113 #define RULE_PROTO_UDP 2
114 struct rule {
115 id_t r_id;
116 int r_idtype;
117 u_int16_t r_port;
118 int r_protocol;
119
120 TAILQ_ENTRY(rule) r_entries;
121 };
122
123 #define GID_STRING "gid"
124 #define TCP_STRING "tcp"
125 #define UID_STRING "uid"
126 #define UDP_STRING "udp"
127
128 /*
129 * Text format for the rule string is that a rule consists of a
130 * comma-separated list of elements. Each element is in the form
131 * idtype:id:protocol:portnumber, and constitutes granting of permission
132 * for the specified binding.
133 */
134
135 static struct mtx rule_mtx;
136 static TAILQ_HEAD(rulehead, rule) rule_head;
137 static char rule_string[MAC_RULE_STRING_LEN];
138
139 static void
140 toast_rules(struct rulehead *head)
141 {
142 struct rule *rule;
143
144 while ((rule = TAILQ_FIRST(head)) != NULL) {
145 TAILQ_REMOVE(head, rule, r_entries);
146 free(rule, M_PORTACL);
147 }
148 }
149
150 /*
151 * Note that there is an inherent race condition in the unload of modules
152 * and access via sysctl.
153 */
154 static void
155 destroy(struct mac_policy_conf *mpc)
156 {
157
158 mtx_destroy(&rule_mtx);
159 toast_rules(&rule_head);
160 }
161
162 static void
163 init(struct mac_policy_conf *mpc)
164 {
165
166 mtx_init(&rule_mtx, "rule_mtx", NULL, MTX_DEF);
167 TAILQ_INIT(&rule_head);
168 }
169
170 /*
171 * Note: parsing routines are destructive on the passed string.
172 */
173 static int
174 parse_rule_element(char *element, struct rule **rule)
175 {
176 char *idtype, *id, *protocol, *portnumber, *p;
177 struct rule *new;
178 int error;
179
180 error = 0;
181 new = malloc(sizeof(*new), M_PORTACL, M_ZERO | M_WAITOK);
182
183 idtype = strsep(&element, ":");
184 if (idtype == NULL) {
185 error = EINVAL;
186 goto out;
187 }
188 id = strsep(&element, ":");
189 if (id == NULL) {
190 error = EINVAL;
191 goto out;
192 }
193 new->r_id = strtol(id, &p, 10);
194 if (*p != '\0') {
195 error = EINVAL;
196 goto out;
197 }
198 if (strcmp(idtype, UID_STRING) == 0)
199 new->r_idtype = RULE_UID;
200 else if (strcmp(idtype, GID_STRING) == 0)
201 new->r_idtype = RULE_GID;
202 else {
203 error = EINVAL;
204 goto out;
205 }
206 protocol = strsep(&element, ":");
207 if (protocol == NULL) {
208 error = EINVAL;
209 goto out;
210 }
211 if (strcmp(protocol, TCP_STRING) == 0)
212 new->r_protocol = RULE_PROTO_TCP;
213 else if (strcmp(protocol, UDP_STRING) == 0)
214 new->r_protocol = RULE_PROTO_UDP;
215 else {
216 error = EINVAL;
217 goto out;
218 }
219 portnumber = element;
220 if (portnumber == NULL) {
221 error = EINVAL;
222 goto out;
223 }
224 new->r_port = strtol(portnumber, &p, 10);
225 if (*p != '\0') {
226 error = EINVAL;
227 goto out;
228 }
229
230 out:
231 if (error != 0) {
232 free(new, M_PORTACL);
233 *rule = NULL;
234 } else
235 *rule = new;
236 return (error);
237 }
238
239 static int
240 parse_rules(char *string, struct rulehead *head)
241 {
242 struct rule *new;
243 char *element;
244 int error;
245
246 error = 0;
247 while ((element = strsep(&string, ",")) != NULL) {
248 if (strlen(element) == 0)
249 continue;
250 error = parse_rule_element(element, &new);
251 if (error)
252 goto out;
253 TAILQ_INSERT_TAIL(head, new, r_entries);
254 }
255 out:
256 if (error != 0)
257 toast_rules(head);
258 return (error);
259 }
260
261 /*
262 * rule_printf() and rules_to_string() are unused currently because they rely
263 * on sbufs with auto-extension, which may sleep while holding a mutex.
264 * Instead, the non-canonical user-generated rule string is returned to the
265 * user when the rules are queried, which is faster anyway.
266 */
267 #if 0
268 static void
269 rule_printf(struct sbuf *sb, struct rule *rule)
270 {
271 const char *idtype, *protocol;
272
273 switch(rule->r_idtype) {
274 case RULE_GID:
275 idtype = GID_STRING;
276 break;
277 case RULE_UID:
278 idtype = UID_STRING;
279 break;
280 default:
281 panic("rule_printf: unknown idtype (%d)\n", rule->r_idtype);
282 }
283
284 switch (rule->r_protocol) {
285 case RULE_PROTO_TCP:
286 protocol = TCP_STRING;
287 break;
288 case RULE_PROTO_UDP:
289 protocol = UDP_STRING;
290 break;
291 default:
292 panic("rule_printf: unknown protocol (%d)\n",
293 rule->r_protocol);
294 }
295 sbuf_printf(sb, "%s:%jd:%s:%d", idtype, (intmax_t)rule->r_id,
296 protocol, rule->r_port);
297 }
298
299 static char *
300 rules_to_string(void)
301 {
302 struct rule *rule;
303 struct sbuf *sb;
304 int needcomma;
305 char *temp;
306
307 sb = sbuf_new_auto();
308 needcomma = 0;
309 mtx_lock(&rule_mtx);
310 for (rule = TAILQ_FIRST(&rule_head); rule != NULL;
311 rule = TAILQ_NEXT(rule, r_entries)) {
312 if (!needcomma)
313 needcomma = 1;
314 else
315 sbuf_printf(sb, ",");
316 rule_printf(sb, rule);
317 }
318 mtx_unlock(&rule_mtx);
319 sbuf_finish(sb);
320 temp = strdup(sbuf_data(sb), M_PORTACL);
321 sbuf_delete(sb);
322 return (temp);
323 }
324 #endif
325
326 /*
327 * Note: due to races, there is not a single serializable order
328 * between parallel calls to the sysctl.
329 */
330 static int
331 sysctl_rules(SYSCTL_HANDLER_ARGS)
332 {
333 char *string, *copy_string, *new_string;
334 struct rulehead head, save_head;
335 int error;
336
337 new_string = NULL;
338 if (req->newptr != NULL) {
339 new_string = malloc(MAC_RULE_STRING_LEN, M_PORTACL,
340 M_WAITOK | M_ZERO);
341 mtx_lock(&rule_mtx);
342 strcpy(new_string, rule_string);
343 mtx_unlock(&rule_mtx);
344 string = new_string;
345 } else
346 string = rule_string;
347
348 error = sysctl_handle_string(oidp, string, MAC_RULE_STRING_LEN, req);
349 if (error)
350 goto out;
351
352 if (req->newptr != NULL) {
353 copy_string = strdup(string, M_PORTACL);
354 TAILQ_INIT(&head);
355 error = parse_rules(copy_string, &head);
356 free(copy_string, M_PORTACL);
357 if (error)
358 goto out;
359
360 TAILQ_INIT(&save_head);
361 mtx_lock(&rule_mtx);
362 TAILQ_CONCAT(&save_head, &rule_head, r_entries);
363 TAILQ_CONCAT(&rule_head, &head, r_entries);
364 strcpy(rule_string, string);
365 mtx_unlock(&rule_mtx);
366 toast_rules(&save_head);
367 }
368 out:
369 if (new_string != NULL)
370 free(new_string, M_PORTACL);
371 return (error);
372 }
373
374 SYSCTL_PROC(_security_mac_portacl, OID_AUTO, rules,
375 CTLTYPE_STRING|CTLFLAG_RW, 0, 0, sysctl_rules, "A", "Rules");
376
377 static int
378 rules_check(struct ucred *cred, int family, int type, u_int16_t port)
379 {
380 struct rule *rule;
381 int error;
382
383 #if 0
384 printf("Check requested for euid %d, family %d, type %d, port %d\n",
385 cred->cr_uid, family, type, port);
386 #endif
387
388 if (port > portacl_port_high)
389 return (0);
390
391 error = EPERM;
392 mtx_lock(&rule_mtx);
393 for (rule = TAILQ_FIRST(&rule_head);
394 rule != NULL;
395 rule = TAILQ_NEXT(rule, r_entries)) {
396 if (type == SOCK_DGRAM && rule->r_protocol != RULE_PROTO_UDP)
397 continue;
398 if (type == SOCK_STREAM && rule->r_protocol != RULE_PROTO_TCP)
399 continue;
400 if (port != rule->r_port)
401 continue;
402 if (rule->r_idtype == RULE_UID) {
403 if (cred->cr_uid == rule->r_id) {
404 error = 0;
405 break;
406 }
407 } else if (rule->r_idtype == RULE_GID) {
408 if (cred->cr_gid == rule->r_id) {
409 error = 0;
410 break;
411 } else if (groupmember(rule->r_id, cred)) {
412 error = 0;
413 break;
414 }
415 } else
416 panic("rules_check: unknown rule type %d",
417 rule->r_idtype);
418 }
419 mtx_unlock(&rule_mtx);
420
421 if (error != 0 && portacl_suser_exempt != 0)
422 error = priv_check_cred(cred, PRIV_NETINET_RESERVEDPORT, 0);
423
424 return (error);
425 }
426
427 /*
428 * Note, this only limits the ability to explicitly bind a port, it
429 * doesn't limit implicitly bound ports for outgoing connections where
430 * the source port is left up to the IP stack to determine automatically.
431 */
432 static int
433 socket_check_bind(struct ucred *cred, struct socket *so,
434 struct label *solabel, struct sockaddr *sa)
435 {
436 struct sockaddr_in *sin;
437 struct inpcb *inp;
438 int family, type;
439 u_int16_t port;
440
441 /* Only run if we are enabled. */
442 if (portacl_enabled == 0)
443 return (0);
444
445 /* Only interested in IPv4 and IPv6 sockets. */
446 if (so->so_proto->pr_domain->dom_family != PF_INET &&
447 so->so_proto->pr_domain->dom_family != PF_INET6)
448 return (0);
449
450 /* Currently, we don't attempt to deal with SOCK_RAW, etc. */
451 if (so->so_type != SOCK_DGRAM &&
452 so->so_type != SOCK_STREAM)
453 return (0);
454
455 /* Reject addresses we don't understand; fail closed. */
456 if (sa->sa_family != AF_INET && sa->sa_family != AF_INET6)
457 return (EINVAL);
458
459 family = so->so_proto->pr_domain->dom_family;
460 type = so->so_type;
461 sin = (struct sockaddr_in *) sa;
462 port = ntohs(sin->sin_port);
463
464 /*
465 * Sockets are frequently bound with a specific IP address but a port
466 * number of '' to request automatic port allocation. This is often
467 * desirable as long as IP_PORTRANGELOW isn't set, which might permit
468 * automatic allocation of a "privileged" port. The autoport exempt
469 * flag exempts port 0 allocation from rule checking as long as a low
470 * port isn't required.
471 */
472 if (portacl_autoport_exempt && port == 0) {
473 inp = sotoinpcb(so);
474 if ((inp->inp_flags & INP_LOWPORT) == 0)
475 return (0);
476 }
477
478 return (rules_check(cred, family, type, port));
479 }
480
481 static struct mac_policy_ops portacl_ops =
482 {
483 .mpo_destroy = destroy,
484 .mpo_init = init,
485 .mpo_socket_check_bind = socket_check_bind,
486 };
487
488 MAC_POLICY_SET(&portacl_ops, mac_portacl, "TrustedBSD MAC/portacl",
489 MPC_LOADTIME_FLAG_UNLOADOK, NULL);
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