1 /* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
2 * selinux.c SELinux security checks for D-Bus
3 *
4 * Author: Matthew Rickard <mjricka@epoch.ncsc.mil>
5 *
6 * Licensed under the Academic Free License version 2.1
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 *
22 */
23
24 #include <config.h>
25 #include <dbus/dbus-internals.h>
26 #include <dbus/dbus-string.h>
27 #ifndef DBUS_WIN
28 #include <dbus/dbus-userdb.h>
29 #endif
30 #include "selinux.h"
31 #include "services.h"
32 #include "policy.h"
33 #include "utils.h"
34 #include "config-parser.h"
35
36 #ifdef HAVE_ERRNO_H
37 #include <errno.h>
38 #endif
39 #ifdef HAVE_SELINUX
40 #include <sys/types.h>
41 #include <unistd.h>
42 #include <limits.h>
43 #include <pthread.h>
44 #include <syslog.h>
45 #include <selinux/selinux.h>
46 #include <selinux/avc.h>
47 #include <selinux/av_permissions.h>
48 #include <selinux/flask.h>
49 #include <signal.h>
50 #include <stdarg.h>
51 #include <stdio.h>
52 #include <grp.h>
53 #endif /* HAVE_SELINUX */
54 #ifdef HAVE_LIBAUDIT
55 #include <cap-ng.h>
56 #include <libaudit.h>
57 #endif /* HAVE_LIBAUDIT */
58
59 #define BUS_SID_FROM_SELINUX(sid) ((BusSELinuxID*) (sid))
60 #define SELINUX_SID_FROM_BUS(sid) ((security_id_t) (sid))
61
62 #ifdef HAVE_SELINUX
63 /* Store the value telling us if SELinux is enabled in the kernel. */
64 static dbus_bool_t selinux_enabled = FALSE;
65
66 /* Store an avc_entry_ref to speed AVC decisions. */
67 static struct avc_entry_ref aeref;
68
69 /* Store the SID of the bus itself to use as the default. */
70 static security_id_t bus_sid = SECSID_WILD;
71
72 /* Thread to listen for SELinux status changes via netlink. */
73 static pthread_t avc_notify_thread;
74
75 /* Prototypes for AVC callback functions. */
76 static void log_callback (const char *fmt, ...);
77 static void log_audit_callback (void *data, security_class_t class, char *buf, size_t bufleft);
78 static void *avc_create_thread (void (*run) (void));
79 static void avc_stop_thread (void *thread);
80 static void *avc_alloc_lock (void);
81 static void avc_get_lock (void *lock);
82 static void avc_release_lock (void *lock);
83 static void avc_free_lock (void *lock);
84
85 /* AVC callback structures for use in avc_init. */
86 static const struct avc_memory_callback mem_cb =
87 {
88 .func_malloc = dbus_malloc,
89 .func_free = dbus_free
90 };
91 static const struct avc_log_callback log_cb =
92 {
93 .func_log = log_callback,
94 .func_audit = log_audit_callback
95 };
96 static const struct avc_thread_callback thread_cb =
97 {
98 .func_create_thread = avc_create_thread,
99 .func_stop_thread = avc_stop_thread
100 };
101 static const struct avc_lock_callback lock_cb =
102 {
103 .func_alloc_lock = avc_alloc_lock,
104 .func_get_lock = avc_get_lock,
105 .func_release_lock = avc_release_lock,
106 .func_free_lock = avc_free_lock
107 };
108 #endif /* HAVE_SELINUX */
109
110 /**
111 * Log callback to log denial messages from the AVC.
112 * This is used in avc_init. Logs to both standard
113 * error and syslogd.
114 *
115 * @param fmt the format string
116 * @param variable argument list
117 */
118 #ifdef HAVE_SELINUX
119
120 #ifdef HAVE_LIBAUDIT
121 static int audit_fd = -1;
122 #endif
123
124 void
bus_selinux_audit_init(void)125 bus_selinux_audit_init(void)
126 {
127 #ifdef HAVE_LIBAUDIT
128 audit_fd = audit_open ();
129
130 if (audit_fd < 0)
131 {
132 /* If kernel doesn't support audit, bail out */
133 if (errno == EINVAL || errno == EPROTONOSUPPORT || errno == EAFNOSUPPORT)
134 return;
135 /* If user bus, bail out */
136 if (errno == EPERM && getuid() != 0)
137 return;
138 _dbus_warn ("Failed opening connection to the audit subsystem");
139 }
140 #endif /* HAVE_LIBAUDIT */
141 }
142
143 static void
log_callback(const char * fmt,...)144 log_callback (const char *fmt, ...)
145 {
146 va_list ap;
147
148 va_start(ap, fmt);
149
150 #ifdef HAVE_LIBAUDIT
151 if (audit_fd >= 0)
152 {
153 capng_get_caps_process();
154 if (capng_have_capability(CAPNG_EFFECTIVE, CAP_AUDIT_WRITE))
155 {
156 char buf[PATH_MAX*2];
157
158 /* FIXME: need to change this to show real user */
159 vsnprintf(buf, sizeof(buf), fmt, ap);
160 audit_log_user_avc_message(audit_fd, AUDIT_USER_AVC, buf, NULL, NULL,
161 NULL, getuid());
162 return;
163 }
164 }
165 #endif /* HAVE_LIBAUDIT */
166
167 vsyslog (LOG_INFO, fmt, ap);
168 va_end(ap);
169 }
170
171 /**
172 * On a policy reload we need to reparse the SELinux configuration file, since
173 * this could have changed. Send a SIGHUP to reload all configs.
174 */
175 static int
policy_reload_callback(u_int32_t event,security_id_t ssid,security_id_t tsid,security_class_t tclass,access_vector_t perms,access_vector_t * out_retained)176 policy_reload_callback (u_int32_t event, security_id_t ssid,
177 security_id_t tsid, security_class_t tclass,
178 access_vector_t perms, access_vector_t *out_retained)
179 {
180 if (event == AVC_CALLBACK_RESET)
181 return raise (SIGHUP);
182
183 return 0;
184 }
185
186 /**
187 * Log any auxiliary data
188 */
189 static void
log_audit_callback(void * data,security_class_t class,char * buf,size_t bufleft)190 log_audit_callback (void *data, security_class_t class, char *buf, size_t bufleft)
191 {
192 DBusString *audmsg = data;
193
194 if (bufleft > (size_t) _dbus_string_get_length(audmsg))
195 {
196 _dbus_string_copy_to_buffer_with_nul (audmsg, buf, bufleft);
197 }
198 else
199 {
200 DBusString s;
201
202 _dbus_string_init_const(&s, "Buffer too small for audit message");
203
204 if (bufleft > (size_t) _dbus_string_get_length(&s))
205 _dbus_string_copy_to_buffer_with_nul (&s, buf, bufleft);
206 }
207 }
208
209 /**
210 * Create thread to notify the AVC of enforcing and policy reload
211 * changes via netlink.
212 *
213 * @param run the thread run function
214 * @return pointer to the thread
215 */
216 static void *
avc_create_thread(void (* run)(void))217 avc_create_thread (void (*run) (void))
218 {
219 int rc;
220
221 rc = pthread_create (&avc_notify_thread, NULL, (void *(*) (void *)) run, NULL);
222 if (rc != 0)
223 {
224 _dbus_warn ("Failed to start AVC thread: %s\n", _dbus_strerror (rc));
225 exit (1);
226 }
227 return &avc_notify_thread;
228 }
229
230 /* Stop AVC netlink thread. */
231 static void
avc_stop_thread(void * thread)232 avc_stop_thread (void *thread)
233 {
234 pthread_cancel (*(pthread_t *) thread);
235 }
236
237 /* Allocate a new AVC lock. */
238 static void *
avc_alloc_lock(void)239 avc_alloc_lock (void)
240 {
241 pthread_mutex_t *avc_mutex;
242
243 avc_mutex = dbus_new (pthread_mutex_t, 1);
244 if (avc_mutex == NULL)
245 {
246 _dbus_warn ("Could not create mutex: %s\n", _dbus_strerror (errno));
247 exit (1);
248 }
249 pthread_mutex_init (avc_mutex, NULL);
250
251 return avc_mutex;
252 }
253
254 /* Acquire an AVC lock. */
255 static void
avc_get_lock(void * lock)256 avc_get_lock (void *lock)
257 {
258 pthread_mutex_lock (lock);
259 }
260
261 /* Release an AVC lock. */
262 static void
avc_release_lock(void * lock)263 avc_release_lock (void *lock)
264 {
265 pthread_mutex_unlock (lock);
266 }
267
268 /* Free an AVC lock. */
269 static void
avc_free_lock(void * lock)270 avc_free_lock (void *lock)
271 {
272 pthread_mutex_destroy (lock);
273 dbus_free (lock);
274 }
275 #endif /* HAVE_SELINUX */
276
277 /**
278 * Return whether or not SELinux is enabled; must be
279 * called after bus_selinux_init.
280 */
281 dbus_bool_t
bus_selinux_enabled(void)282 bus_selinux_enabled (void)
283 {
284 #ifdef HAVE_SELINUX
285 return selinux_enabled;
286 #else
287 return FALSE;
288 #endif /* HAVE_SELINUX */
289 }
290
291 /**
292 * Do early initialization; determine whether SELinux is enabled.
293 */
294 dbus_bool_t
bus_selinux_pre_init(void)295 bus_selinux_pre_init (void)
296 {
297 #ifdef HAVE_SELINUX
298 int r;
299 _dbus_assert (bus_sid == SECSID_WILD);
300
301 /* Determine if we are running an SELinux kernel. */
302 r = is_selinux_enabled ();
303 if (r < 0)
304 {
305 _dbus_warn ("Could not tell if SELinux is enabled: %s\n",
306 _dbus_strerror (errno));
307 return FALSE;
308 }
309
310 selinux_enabled = r != 0;
311 return TRUE;
312 #else
313 return TRUE;
314 #endif
315 }
316
317 /**
318 * Initialize the user space access vector cache (AVC) for D-Bus and set up
319 * logging callbacks.
320 */
321 dbus_bool_t
bus_selinux_full_init(void)322 bus_selinux_full_init (void)
323 {
324 #ifdef HAVE_SELINUX
325 char *bus_context;
326
327 _dbus_assert (bus_sid == SECSID_WILD);
328
329 if (!selinux_enabled)
330 {
331 _dbus_verbose ("SELinux not enabled in this kernel.\n");
332 return TRUE;
333 }
334
335 _dbus_verbose ("SELinux is enabled in this kernel.\n");
336
337 avc_entry_ref_init (&aeref);
338 if (avc_init ("avc", &mem_cb, &log_cb, &thread_cb, &lock_cb) < 0)
339 {
340 _dbus_warn ("Failed to start Access Vector Cache (AVC).\n");
341 return FALSE;
342 }
343 else
344 {
345 openlog ("dbus", LOG_PERROR, LOG_USER);
346 _dbus_verbose ("Access Vector Cache (AVC) started.\n");
347 }
348
349 if (avc_add_callback (policy_reload_callback, AVC_CALLBACK_RESET,
350 NULL, NULL, 0, 0) < 0)
351 {
352 _dbus_warn ("Failed to add policy reload callback: %s\n",
353 _dbus_strerror (errno));
354 avc_destroy ();
355 return FALSE;
356 }
357
358 bus_context = NULL;
359 bus_sid = SECSID_WILD;
360
361 if (getcon (&bus_context) < 0)
362 {
363 _dbus_verbose ("Error getting context of bus: %s\n",
364 _dbus_strerror (errno));
365 return FALSE;
366 }
367
368 if (avc_context_to_sid (bus_context, &bus_sid) < 0)
369 {
370 _dbus_verbose ("Error getting SID from bus context: %s\n",
371 _dbus_strerror (errno));
372 freecon (bus_context);
373 return FALSE;
374 }
375
376 freecon (bus_context);
377
378 #endif /* HAVE_SELINUX */
379 return TRUE;
380 }
381
382 /**
383 * Decrement SID reference count.
384 *
385 * @param sid the SID to decrement
386 */
387 void
bus_selinux_id_unref(BusSELinuxID * sid)388 bus_selinux_id_unref (BusSELinuxID *sid)
389 {
390 #ifdef HAVE_SELINUX
391 if (!selinux_enabled)
392 return;
393
394 _dbus_assert (sid != NULL);
395
396 sidput (SELINUX_SID_FROM_BUS (sid));
397 #endif /* HAVE_SELINUX */
398 }
399
400 void
bus_selinux_id_ref(BusSELinuxID * sid)401 bus_selinux_id_ref (BusSELinuxID *sid)
402 {
403 #ifdef HAVE_SELINUX
404 if (!selinux_enabled)
405 return;
406
407 _dbus_assert (sid != NULL);
408
409 sidget (SELINUX_SID_FROM_BUS (sid));
410 #endif /* HAVE_SELINUX */
411 }
412
413 /**
414 * Determine if the SELinux security policy allows the given sender
415 * security context to go to the given recipient security context.
416 * This function determines if the requested permissions are to be
417 * granted from the connection to the message bus or to another
418 * optionally supplied security identifier (e.g. for a service
419 * context). Currently these permissions are either send_msg or
420 * acquire_svc in the dbus class.
421 *
422 * @param sender_sid source security context
423 * @param override_sid is the target security context. If SECSID_WILD this will
424 * use the context of the bus itself (e.g. the default).
425 * @param target_class is the target security class.
426 * @param requested is the requested permissions.
427 * @returns #TRUE if security policy allows the send.
428 */
429 #ifdef HAVE_SELINUX
430 static dbus_bool_t
bus_selinux_check(BusSELinuxID * sender_sid,BusSELinuxID * override_sid,security_class_t target_class,access_vector_t requested,DBusString * auxdata)431 bus_selinux_check (BusSELinuxID *sender_sid,
432 BusSELinuxID *override_sid,
433 security_class_t target_class,
434 access_vector_t requested,
435 DBusString *auxdata)
436 {
437 if (!selinux_enabled)
438 return TRUE;
439
440 /* Make the security check. AVC checks enforcing mode here as well. */
441 if (avc_has_perm (SELINUX_SID_FROM_BUS (sender_sid),
442 override_sid ?
443 SELINUX_SID_FROM_BUS (override_sid) :
444 SELINUX_SID_FROM_BUS (bus_sid),
445 target_class, requested, &aeref, auxdata) < 0)
446 {
447 switch (errno)
448 {
449 case EACCES:
450 _dbus_verbose ("SELinux denying due to security policy.\n");
451 return FALSE;
452 case EINVAL:
453 _dbus_verbose ("SELinux denying due to invalid security context.\n");
454 return FALSE;
455 default:
456 _dbus_verbose ("SELinux denying due to: %s\n", _dbus_strerror (errno));
457 return FALSE;
458 }
459 }
460 else
461 return TRUE;
462 }
463 #endif /* HAVE_SELINUX */
464
465 /**
466 * Returns true if the given connection can acquire a service,
467 * assuming the given security ID is needed for that service.
468 *
469 * @param connection connection that wants to own the service
470 * @param service_sid the SID of the service from the table
471 * @returns #TRUE if acquire is permitted.
472 */
473 dbus_bool_t
bus_selinux_allows_acquire_service(DBusConnection * connection,BusSELinuxID * service_sid,const char * service_name,DBusError * error)474 bus_selinux_allows_acquire_service (DBusConnection *connection,
475 BusSELinuxID *service_sid,
476 const char *service_name,
477 DBusError *error)
478 {
479 #ifdef HAVE_SELINUX
480 BusSELinuxID *connection_sid;
481 unsigned long spid;
482 DBusString auxdata;
483 dbus_bool_t ret;
484
485 if (!selinux_enabled)
486 return TRUE;
487
488 connection_sid = bus_connection_get_selinux_id (connection);
489 if (!dbus_connection_get_unix_process_id (connection, &spid))
490 spid = 0;
491
492 if (!_dbus_string_init (&auxdata))
493 goto oom;
494
495 if (!_dbus_string_append (&auxdata, "service="))
496 goto oom;
497
498 if (!_dbus_string_append (&auxdata, service_name))
499 goto oom;
500
501 if (spid)
502 {
503 if (!_dbus_string_append (&auxdata, " spid="))
504 goto oom;
505
506 if (!_dbus_string_append_uint (&auxdata, spid))
507 goto oom;
508 }
509
510 ret = bus_selinux_check (connection_sid,
511 service_sid,
512 SECCLASS_DBUS,
513 DBUS__ACQUIRE_SVC,
514 &auxdata);
515
516 _dbus_string_free (&auxdata);
517 return ret;
518
519 oom:
520 _dbus_string_free (&auxdata);
521 BUS_SET_OOM (error);
522 return FALSE;
523
524 #else
525 return TRUE;
526 #endif /* HAVE_SELINUX */
527 }
528
529 /**
530 * Check if SELinux security controls allow the message to be sent to a
531 * particular connection based on the security context of the sender and
532 * that of the receiver. The destination connection need not be the
533 * addressed recipient, it could be an "eavesdropper"
534 *
535 * @param sender the sender of the message.
536 * @param proposed_recipient the connection the message is to be sent to.
537 * @returns whether to allow the send
538 */
539 dbus_bool_t
bus_selinux_allows_send(DBusConnection * sender,DBusConnection * proposed_recipient,const char * msgtype,const char * interface,const char * member,const char * error_name,const char * destination,DBusError * error)540 bus_selinux_allows_send (DBusConnection *sender,
541 DBusConnection *proposed_recipient,
542 const char *msgtype,
543 const char *interface,
544 const char *member,
545 const char *error_name,
546 const char *destination,
547 DBusError *error)
548 {
549 #ifdef HAVE_SELINUX
550 BusSELinuxID *recipient_sid;
551 BusSELinuxID *sender_sid;
552 unsigned long spid, tpid;
553 DBusString auxdata;
554 dbus_bool_t ret;
555 dbus_bool_t string_alloced;
556
557 if (!selinux_enabled)
558 return TRUE;
559
560 if (!sender || !dbus_connection_get_unix_process_id (sender, &spid))
561 spid = 0;
562 if (!proposed_recipient || !dbus_connection_get_unix_process_id (proposed_recipient, &tpid))
563 tpid = 0;
564
565 string_alloced = FALSE;
566 if (!_dbus_string_init (&auxdata))
567 goto oom;
568 string_alloced = TRUE;
569
570 if (!_dbus_string_append (&auxdata, "msgtype="))
571 goto oom;
572
573 if (!_dbus_string_append (&auxdata, msgtype))
574 goto oom;
575
576 if (interface)
577 {
578 if (!_dbus_string_append (&auxdata, " interface="))
579 goto oom;
580 if (!_dbus_string_append (&auxdata, interface))
581 goto oom;
582 }
583
584 if (member)
585 {
586 if (!_dbus_string_append (&auxdata, " member="))
587 goto oom;
588 if (!_dbus_string_append (&auxdata, member))
589 goto oom;
590 }
591
592 if (error_name)
593 {
594 if (!_dbus_string_append (&auxdata, " error_name="))
595 goto oom;
596 if (!_dbus_string_append (&auxdata, error_name))
597 goto oom;
598 }
599
600 if (destination)
601 {
602 if (!_dbus_string_append (&auxdata, " dest="))
603 goto oom;
604 if (!_dbus_string_append (&auxdata, destination))
605 goto oom;
606 }
607
608 if (spid)
609 {
610 if (!_dbus_string_append (&auxdata, " spid="))
611 goto oom;
612
613 if (!_dbus_string_append_uint (&auxdata, spid))
614 goto oom;
615 }
616
617 if (tpid)
618 {
619 if (!_dbus_string_append (&auxdata, " tpid="))
620 goto oom;
621
622 if (!_dbus_string_append_uint (&auxdata, tpid))
623 goto oom;
624 }
625
626 sender_sid = bus_connection_get_selinux_id (sender);
627 /* A NULL proposed_recipient means the bus itself. */
628 if (proposed_recipient)
629 recipient_sid = bus_connection_get_selinux_id (proposed_recipient);
630 else
631 recipient_sid = BUS_SID_FROM_SELINUX (bus_sid);
632
633 ret = bus_selinux_check (sender_sid,
634 recipient_sid,
635 SECCLASS_DBUS,
636 DBUS__SEND_MSG,
637 &auxdata);
638
639 _dbus_string_free (&auxdata);
640
641 return ret;
642
643 oom:
644 if (string_alloced)
645 _dbus_string_free (&auxdata);
646 BUS_SET_OOM (error);
647 return FALSE;
648
649 #else
650 return TRUE;
651 #endif /* HAVE_SELINUX */
652 }
653
654 dbus_bool_t
bus_selinux_append_context(DBusMessage * message,BusSELinuxID * sid,DBusError * error)655 bus_selinux_append_context (DBusMessage *message,
656 BusSELinuxID *sid,
657 DBusError *error)
658 {
659 #ifdef HAVE_SELINUX
660 char *context;
661
662 if (avc_sid_to_context (SELINUX_SID_FROM_BUS (sid), &context) < 0)
663 {
664 if (errno == ENOMEM)
665 BUS_SET_OOM (error);
666 else
667 dbus_set_error (error, DBUS_ERROR_FAILED,
668 "Error getting context from SID: %s\n",
669 _dbus_strerror (errno));
670 return FALSE;
671 }
672 if (!dbus_message_append_args (message,
673 DBUS_TYPE_ARRAY,
674 DBUS_TYPE_BYTE,
675 &context,
676 strlen (context),
677 DBUS_TYPE_INVALID))
678 {
679 _DBUS_SET_OOM (error);
680 return FALSE;
681 }
682 freecon (context);
683 return TRUE;
684 #else
685 return TRUE;
686 #endif
687 }
688
689 /**
690 * Gets the security context of a connection to the bus. It is up to
691 * the caller to freecon() when they are done.
692 *
693 * @param connection the connection to get the context of.
694 * @param con the location to store the security context.
695 * @returns #TRUE if context is successfully obtained.
696 */
697 #ifdef HAVE_SELINUX
698 static dbus_bool_t
bus_connection_read_selinux_context(DBusConnection * connection,char ** con)699 bus_connection_read_selinux_context (DBusConnection *connection,
700 char **con)
701 {
702 int fd;
703
704 if (!selinux_enabled)
705 return FALSE;
706
707 _dbus_assert (connection != NULL);
708
709 if (!dbus_connection_get_unix_fd (connection, &fd))
710 {
711 _dbus_verbose ("Failed to get file descriptor of socket.\n");
712 return FALSE;
713 }
714
715 if (getpeercon (fd, con) < 0)
716 {
717 _dbus_verbose ("Error getting context of socket peer: %s\n",
718 _dbus_strerror (errno));
719 return FALSE;
720 }
721
722 _dbus_verbose ("Successfully read connection context.\n");
723 return TRUE;
724 }
725 #endif /* HAVE_SELINUX */
726
727 /**
728 * Read the SELinux ID from the connection.
729 *
730 * @param connection the connection to read from
731 * @returns the SID if successfully determined, #NULL otherwise.
732 */
733 BusSELinuxID*
bus_selinux_init_connection_id(DBusConnection * connection,DBusError * error)734 bus_selinux_init_connection_id (DBusConnection *connection,
735 DBusError *error)
736 {
737 #ifdef HAVE_SELINUX
738 char *con;
739 security_id_t sid;
740
741 if (!selinux_enabled)
742 return NULL;
743
744 if (!bus_connection_read_selinux_context (connection, &con))
745 {
746 dbus_set_error (error, DBUS_ERROR_FAILED,
747 "Failed to read an SELinux context from connection");
748 _dbus_verbose ("Error getting peer context.\n");
749 return NULL;
750 }
751
752 _dbus_verbose ("Converting context to SID to store on connection\n");
753
754 if (avc_context_to_sid (con, &sid) < 0)
755 {
756 if (errno == ENOMEM)
757 BUS_SET_OOM (error);
758 else
759 dbus_set_error (error, DBUS_ERROR_FAILED,
760 "Error getting SID from context \"%s\": %s\n",
761 con, _dbus_strerror (errno));
762
763 _dbus_warn ("Error getting SID from context \"%s\": %s\n",
764 con, _dbus_strerror (errno));
765
766 freecon (con);
767 return NULL;
768 }
769
770 freecon (con);
771 return BUS_SID_FROM_SELINUX (sid);
772 #else
773 return NULL;
774 #endif /* HAVE_SELINUX */
775 }
776
777
778 /**
779 * Function for freeing hash table data. These SIDs
780 * should no longer be referenced.
781 */
782 static void
bus_selinux_id_table_free_value(BusSELinuxID * sid)783 bus_selinux_id_table_free_value (BusSELinuxID *sid)
784 {
785 #ifdef HAVE_SELINUX
786 /* NULL sometimes due to how DBusHashTable works */
787 if (sid)
788 bus_selinux_id_unref (sid);
789 #endif /* HAVE_SELINUX */
790 }
791
792 /**
793 * Creates a new table mapping service names to security ID.
794 * A security ID is a "compiled" security context, a security
795 * context is just a string.
796 *
797 * @returns the new table or #NULL if no memory
798 */
799 DBusHashTable*
bus_selinux_id_table_new(void)800 bus_selinux_id_table_new (void)
801 {
802 return _dbus_hash_table_new (DBUS_HASH_STRING,
803 (DBusFreeFunction) dbus_free,
804 (DBusFreeFunction) bus_selinux_id_table_free_value);
805 }
806
807 /**
808 * Hashes a service name and service context into the service SID
809 * table as a string and a SID.
810 *
811 * @param service_name is the name of the service.
812 * @param service_context is the context of the service.
813 * @param service_table is the table to hash them into.
814 * @return #FALSE if not enough memory
815 */
816 dbus_bool_t
bus_selinux_id_table_insert(DBusHashTable * service_table,const char * service_name,const char * service_context)817 bus_selinux_id_table_insert (DBusHashTable *service_table,
818 const char *service_name,
819 const char *service_context)
820 {
821 #ifdef HAVE_SELINUX
822 dbus_bool_t retval;
823 security_id_t sid;
824 char *key;
825
826 if (!selinux_enabled)
827 return TRUE;
828
829 sid = SECSID_WILD;
830 retval = FALSE;
831
832 key = _dbus_strdup (service_name);
833 if (key == NULL)
834 return retval;
835
836 if (avc_context_to_sid ((char *) service_context, &sid) < 0)
837 {
838 if (errno == ENOMEM)
839 {
840 dbus_free (key);
841 return FALSE;
842 }
843
844 _dbus_warn ("Error getting SID from context \"%s\": %s\n",
845 (char *) service_context,
846 _dbus_strerror (errno));
847 goto out;
848 }
849
850 if (!_dbus_hash_table_insert_string (service_table,
851 key,
852 BUS_SID_FROM_SELINUX (sid)))
853 goto out;
854
855 _dbus_verbose ("Parsed \tservice: %s \n\t\tcontext: %s\n",
856 key,
857 sid->ctx);
858
859 /* These are owned by the hash, so clear them to avoid unref */
860 key = NULL;
861 sid = SECSID_WILD;
862
863 retval = TRUE;
864
865 out:
866 if (sid != SECSID_WILD)
867 sidput (sid);
868
869 if (key)
870 dbus_free (key);
871
872 return retval;
873 #else
874 return TRUE;
875 #endif /* HAVE_SELINUX */
876 }
877
878
879 /**
880 * Find the security identifier associated with a particular service
881 * name. Return a pointer to this SID, or #NULL/SECSID_WILD if the
882 * service is not found in the hash table. This should be nearly a
883 * constant time operation. If SELinux support is not available,
884 * always return NULL.
885 *
886 * @param service_table the hash table to check for service name.
887 * @param service_name the name of the service to look for.
888 * @returns the SELinux ID associated with the service
889 */
890 BusSELinuxID*
bus_selinux_id_table_lookup(DBusHashTable * service_table,const DBusString * service_name)891 bus_selinux_id_table_lookup (DBusHashTable *service_table,
892 const DBusString *service_name)
893 {
894 #ifdef HAVE_SELINUX
895 security_id_t sid;
896
897 sid = SECSID_WILD; /* default context */
898
899 if (!selinux_enabled)
900 return NULL;
901
902 _dbus_verbose ("Looking up service SID for %s\n",
903 _dbus_string_get_const_data (service_name));
904
905 sid = _dbus_hash_table_lookup_string (service_table,
906 _dbus_string_get_const_data (service_name));
907
908 if (sid == SECSID_WILD)
909 _dbus_verbose ("Service %s not found\n",
910 _dbus_string_get_const_data (service_name));
911 else
912 _dbus_verbose ("Service %s found\n",
913 _dbus_string_get_const_data (service_name));
914
915 return BUS_SID_FROM_SELINUX (sid);
916 #endif /* HAVE_SELINUX */
917 return NULL;
918 }
919
920 /**
921 * Get the SELinux policy root. This is used to find the D-Bus
922 * specific config file within the policy.
923 */
924 const char *
bus_selinux_get_policy_root(void)925 bus_selinux_get_policy_root (void)
926 {
927 #ifdef HAVE_SELINUX
928 return selinux_policy_root ();
929 #else
930 return NULL;
931 #endif /* HAVE_SELINUX */
932 }
933
934 /**
935 * For debugging: Print out the current hash table of service SIDs.
936 */
937 void
bus_selinux_id_table_print(DBusHashTable * service_table)938 bus_selinux_id_table_print (DBusHashTable *service_table)
939 {
940 #ifdef DBUS_ENABLE_VERBOSE_MODE
941 #ifdef HAVE_SELINUX
942 DBusHashIter iter;
943
944 if (!selinux_enabled)
945 return;
946
947 _dbus_verbose ("Service SID Table:\n");
948 _dbus_hash_iter_init (service_table, &iter);
949 while (_dbus_hash_iter_next (&iter))
950 {
951 const char *key = _dbus_hash_iter_get_string_key (&iter);
952 security_id_t sid = _dbus_hash_iter_get_value (&iter);
953 _dbus_verbose ("The key is %s\n", key);
954 _dbus_verbose ("The context is %s\n", sid->ctx);
955 _dbus_verbose ("The refcount is %d\n", sid->refcnt);
956 }
957 #endif /* HAVE_SELINUX */
958 #endif /* DBUS_ENABLE_VERBOSE_MODE */
959 }
960
961
962 #ifdef DBUS_ENABLE_VERBOSE_MODE
963 #ifdef HAVE_SELINUX
964 /**
965 * Print out some AVC statistics.
966 */
967 static void
bus_avc_print_stats(void)968 bus_avc_print_stats (void)
969 {
970 struct avc_cache_stats cstats;
971
972 if (!selinux_enabled)
973 return;
974
975 _dbus_verbose ("AVC Statistics:\n");
976 avc_cache_stats (&cstats);
977 avc_av_stats ();
978 _dbus_verbose ("AVC Cache Statistics:\n");
979 _dbus_verbose ("Entry lookups: %d\n", cstats.entry_lookups);
980 _dbus_verbose ("Entry hits: %d\n", cstats.entry_hits);
981 _dbus_verbose ("Entry misses %d\n", cstats.entry_misses);
982 _dbus_verbose ("Entry discards: %d\n", cstats.entry_discards);
983 _dbus_verbose ("CAV lookups: %d\n", cstats.cav_lookups);
984 _dbus_verbose ("CAV hits: %d\n", cstats.cav_hits);
985 _dbus_verbose ("CAV probes: %d\n", cstats.cav_probes);
986 _dbus_verbose ("CAV misses: %d\n", cstats.cav_misses);
987 }
988 #endif /* HAVE_SELINUX */
989 #endif /* DBUS_ENABLE_VERBOSE_MODE */
990
991
992 /**
993 * Destroy the AVC before we terminate.
994 */
995 void
bus_selinux_shutdown(void)996 bus_selinux_shutdown (void)
997 {
998 #ifdef HAVE_SELINUX
999 if (!selinux_enabled)
1000 return;
1001
1002 _dbus_verbose ("AVC shutdown\n");
1003
1004 if (bus_sid != SECSID_WILD)
1005 {
1006 sidput (bus_sid);
1007 bus_sid = SECSID_WILD;
1008
1009 #ifdef DBUS_ENABLE_VERBOSE_MODE
1010
1011 if (_dbus_is_verbose())
1012 bus_avc_print_stats ();
1013
1014 #endif /* DBUS_ENABLE_VERBOSE_MODE */
1015
1016 avc_destroy ();
1017 #ifdef HAVE_LIBAUDIT
1018 audit_close (audit_fd);
1019 #endif /* HAVE_LIBAUDIT */
1020 }
1021 #endif /* HAVE_SELINUX */
1022 }
1023
1024 /* The !HAVE_LIBAUDIT case lives in dbus-sysdeps-util-unix.c */
1025 #ifdef HAVE_LIBAUDIT
1026 /**
1027 * Changes the user and group the bus is running as.
1028 *
1029 * @param user the user to become
1030 * @param error return location for errors
1031 * @returns #FALSE on failure
1032 */
1033 dbus_bool_t
_dbus_change_to_daemon_user(const char * user,DBusError * error)1034 _dbus_change_to_daemon_user (const char *user,
1035 DBusError *error)
1036 {
1037 dbus_uid_t uid;
1038 dbus_gid_t gid;
1039 DBusString u;
1040
1041 _dbus_string_init_const (&u, user);
1042
1043 if (!_dbus_get_user_id_and_primary_group (&u, &uid, &gid))
1044 {
1045 dbus_set_error (error, DBUS_ERROR_FAILED,
1046 "User '%s' does not appear to exist?",
1047 user);
1048 return FALSE;
1049 }
1050
1051 /* If we were root */
1052 if (_dbus_geteuid () == 0)
1053 {
1054 int rc;
1055
1056 capng_clear (CAPNG_SELECT_BOTH);
1057 capng_update (CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED,
1058 CAP_AUDIT_WRITE);
1059 rc = capng_change_id (uid, gid, 0);
1060 if (rc)
1061 {
1062 switch (rc) {
1063 default:
1064 dbus_set_error (error, DBUS_ERROR_FAILED,
1065 "Failed to drop capabilities: %s\n",
1066 _dbus_strerror (errno));
1067 break;
1068 case -4:
1069 dbus_set_error (error, _dbus_error_from_errno (errno),
1070 "Failed to set GID to %lu: %s", gid,
1071 _dbus_strerror (errno));
1072 break;
1073 case -5:
1074 _dbus_warn ("Failed to drop supplementary groups: %s\n",
1075 _dbus_strerror (errno));
1076 break;
1077 case -6:
1078 dbus_set_error (error, _dbus_error_from_errno (errno),
1079 "Failed to set UID to %lu: %s", uid,
1080 _dbus_strerror (errno));
1081 break;
1082 case -7:
1083 dbus_set_error (error, _dbus_error_from_errno (errno),
1084 "Failed to unset keep-capabilities: %s\n",
1085 _dbus_strerror (errno));
1086 break;
1087 }
1088 return FALSE;
1089 }
1090 }
1091
1092 return TRUE;
1093 }
1094 #endif
1095