1 /* selinux.c SELinux security checks for D-BUS
3 * Author: Matthew Rickard <mjricka@epoch.ncsc.mil>
5 * Licensed under the Academic Free License version 2.1
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 #include <dbus/dbus-internals.h>
23 #include <dbus/dbus-string.h>
28 #include "config-parser.h"
34 #include <selinux/selinux.h>
35 #include <selinux/avc.h>
36 #include <selinux/av_permissions.h>
37 #include <selinux/flask.h>
40 #endif /* HAVE_SELINUX */
42 #define BUS_SID_FROM_SELINUX(sid) ((BusSELinuxID*) (sid))
43 #define SELINUX_SID_FROM_BUS(sid) ((security_id_t) (sid))
46 /* Store the value telling us if SELinux is enabled in the kernel. */
47 static dbus_bool_t selinux_enabled = FALSE;
49 /* Store an avc_entry_ref to speed AVC decisions. */
50 static struct avc_entry_ref aeref;
52 /* Store the SID of the bus itself to use as the default. */
53 static security_id_t bus_sid = SECSID_WILD;
55 /* Thread to listen for SELinux status changes via netlink. */
56 static pthread_t avc_notify_thread;
58 /* Prototypes for AVC callback functions. */
59 static void log_callback (const char *fmt, ...);
60 static void *avc_create_thread (void (*run) (void));
61 static void avc_stop_thread (void *thread);
62 static void *avc_alloc_lock (void);
63 static void avc_get_lock (void *lock);
64 static void avc_release_lock (void *lock);
65 static void avc_free_lock (void *lock);
67 /* AVC callback structures for use in avc_init. */
68 static const struct avc_memory_callback mem_cb =
70 .func_malloc = dbus_malloc,
71 .func_free = dbus_free
73 static const struct avc_log_callback log_cb =
75 .func_log = log_callback,
78 static const struct avc_thread_callback thread_cb =
80 .func_create_thread = avc_create_thread,
81 .func_stop_thread = avc_stop_thread
83 static const struct avc_lock_callback lock_cb =
85 .func_alloc_lock = avc_alloc_lock,
86 .func_get_lock = avc_get_lock,
87 .func_release_lock = avc_release_lock,
88 .func_free_lock = avc_free_lock
90 #endif /* HAVE_SELINUX */
93 * Log callback to log denial messages from the AVC.
94 * This is used in avc_init. Logs to both standard
97 * @param fmt the format string
98 * @param variable argument list
102 log_callback (const char *fmt, ...)
106 vsyslog (LOG_INFO, fmt, ap);
111 * On a policy reload we need to reparse the SELinux configuration file, since
112 * this could have changed. Send a SIGHUP to reload all configs.
115 policy_reload_callback (u_int32_t event, security_id_t ssid,
116 security_id_t tsid, security_class_t tclass,
117 access_vector_t perms, access_vector_t *out_retained)
119 if (event == AVC_CALLBACK_RESET)
120 return raise (SIGHUP);
126 * Create thread to notify the AVC of enforcing and policy reload
127 * changes via netlink.
129 * @param run the thread run function
130 * @return pointer to the thread
133 avc_create_thread (void (*run) (void))
137 rc = pthread_create (&avc_notify_thread, NULL, (void *(*) (void *)) run, NULL);
140 _dbus_warn ("Failed to start AVC thread: %s\n", _dbus_strerror (rc));
143 return &avc_notify_thread;
146 /* Stop AVC netlink thread. */
148 avc_stop_thread (void *thread)
150 pthread_cancel (*(pthread_t *) thread);
153 /* Allocate a new AVC lock. */
155 avc_alloc_lock (void)
157 pthread_mutex_t *avc_mutex;
159 avc_mutex = dbus_new (pthread_mutex_t, 1);
160 if (avc_mutex == NULL)
162 _dbus_warn ("Could not create mutex: %s\n", _dbus_strerror (errno));
165 pthread_mutex_init (avc_mutex, NULL);
170 /* Acquire an AVC lock. */
172 avc_get_lock (void *lock)
174 pthread_mutex_lock (lock);
177 /* Release an AVC lock. */
179 avc_release_lock (void *lock)
181 pthread_mutex_unlock (lock);
184 /* Free an AVC lock. */
186 avc_free_lock (void *lock)
188 pthread_mutex_destroy (lock);
191 #endif /* HAVE_SELINUX */
194 * Initialize the user space access vector cache (AVC) for D-BUS and set up
198 bus_selinux_init (void)
204 _dbus_assert (bus_sid == SECSID_WILD);
206 /* Determine if we are running an SELinux kernel. */
207 r = is_selinux_enabled ();
210 _dbus_warn ("Could not tell if SELinux is enabled: %s\n",
211 _dbus_strerror (errno));
215 selinux_enabled = r != 0;
217 if (!selinux_enabled)
219 _dbus_verbose ("SELinux not enabled in this kernel.\n");
223 _dbus_verbose ("SELinux is enabled in this kernel.\n");
225 avc_entry_ref_init (&aeref);
226 if (avc_init ("avc", &mem_cb, &log_cb, &thread_cb, &lock_cb) < 0)
228 _dbus_warn ("Failed to start Access Vector Cache (AVC).\n");
233 openlog ("dbus", LOG_PERROR, LOG_USER);
234 _dbus_verbose ("Access Vector Cache (AVC) started.\n");
237 if (avc_add_callback (policy_reload_callback, AVC_CALLBACK_RESET,
238 NULL, NULL, 0, 0) < 0)
240 _dbus_warn ("Failed to add policy reload callback: %s\n",
241 _dbus_strerror (errno));
247 bus_sid = SECSID_WILD;
249 if (getcon (&bus_context) < 0)
251 _dbus_verbose ("Error getting context of bus: %s\n",
252 _dbus_strerror (errno));
256 if (avc_context_to_sid (bus_context, &bus_sid) < 0)
258 _dbus_verbose ("Error getting SID from bus context: %s\n",
259 _dbus_strerror (errno));
260 freecon (bus_context);
264 freecon (bus_context);
269 #endif /* HAVE_SELINUX */
273 * Decrement SID reference count.
275 * @param sid the SID to decrement
278 bus_selinux_id_unref (BusSELinuxID *sid)
281 if (!selinux_enabled)
284 _dbus_assert (sid != NULL);
286 sidput (SELINUX_SID_FROM_BUS (sid));
287 #endif /* HAVE_SELINUX */
291 bus_selinux_id_ref (BusSELinuxID *sid)
294 if (!selinux_enabled)
297 _dbus_assert (sid != NULL);
299 sidget (SELINUX_SID_FROM_BUS (sid));
300 #endif /* HAVE_SELINUX */
304 * Determine if the SELinux security policy allows the given sender
305 * security context to go to the given recipient security context.
306 * This function determines if the requested permissions are to be
307 * granted from the connection to the message bus or to another
308 * optionally supplied security identifier (e.g. for a service
309 * context). Currently these permissions are either send_msg or
310 * acquire_svc in the dbus class.
312 * @param sender_sid source security context
313 * @param override_sid is the target security context. If SECSID_WILD this will
314 * use the context of the bus itself (e.g. the default).
315 * @param target_class is the target security class.
316 * @param requested is the requested permissions.
317 * @returns #TRUE if security policy allows the send.
321 bus_selinux_check (BusSELinuxID *sender_sid,
322 BusSELinuxID *override_sid,
323 security_class_t target_class,
324 access_vector_t requested)
326 if (!selinux_enabled)
329 /* Make the security check. AVC checks enforcing mode here as well. */
330 if (avc_has_perm (SELINUX_SID_FROM_BUS (sender_sid),
332 SELINUX_SID_FROM_BUS (override_sid) :
333 SELINUX_SID_FROM_BUS (bus_sid),
334 target_class, requested, &aeref, NULL) < 0)
336 _dbus_verbose ("SELinux denying due to security policy.\n");
342 #endif /* HAVE_SELINUX */
345 * Returns true if the given connection can acquire a service,
346 * assuming the given security ID is needed for that service.
348 * @param connection connection that wants to own the service
349 * @param service_sid the SID of the service from the table
350 * @returns #TRUE if acquire is permitted.
353 bus_selinux_allows_acquire_service (DBusConnection *connection,
354 BusSELinuxID *service_sid)
357 BusSELinuxID *connection_sid;
359 if (!selinux_enabled)
362 connection_sid = bus_connection_get_selinux_id (connection);
364 return bus_selinux_check (connection_sid,
370 #endif /* HAVE_SELINUX */
374 * Check if SELinux security controls allow the message to be sent to a
375 * particular connection based on the security context of the sender and
376 * that of the receiver. The destination connection need not be the
377 * addressed recipient, it could be an "eavesdropper"
379 * @param sender the sender of the message.
380 * @param proposed_recipient the connection the message is to be sent to.
381 * @returns whether to allow the send
384 bus_selinux_allows_send (DBusConnection *sender,
385 DBusConnection *proposed_recipient)
388 BusSELinuxID *recipient_sid;
389 BusSELinuxID *sender_sid;
391 if (!selinux_enabled)
394 sender_sid = bus_connection_get_selinux_id (sender);
395 /* A NULL proposed_recipient means the bus itself. */
396 if (proposed_recipient)
397 recipient_sid = bus_connection_get_selinux_id (proposed_recipient);
399 recipient_sid = BUS_SID_FROM_SELINUX (bus_sid);
401 return bus_selinux_check (sender_sid, recipient_sid,
402 SECCLASS_DBUS, DBUS__SEND_MSG);
405 #endif /* HAVE_SELINUX */
409 * Gets the security context of a connection to the bus. It is up to
410 * the caller to freecon() when they are done.
412 * @param connection the connection to get the context of.
413 * @param con the location to store the security context.
414 * @returns #TRUE if context is successfully obtained.
418 bus_connection_read_selinux_context (DBusConnection *connection,
423 if (!selinux_enabled)
426 _dbus_assert (connection != NULL);
428 if (!dbus_connection_get_unix_fd (connection, &fd))
430 _dbus_verbose ("Failed to get file descriptor of socket.\n");
434 if (getpeercon (fd, con) < 0)
436 _dbus_verbose ("Error getting context of socket peer: %s\n",
437 _dbus_strerror (errno));
441 _dbus_verbose ("Successfully read connection context.\n");
444 #endif /* HAVE_SELINUX */
447 * Read the SELinux ID from the connection.
449 * @param connection the connection to read from
450 * @returns the SID if successfully determined, #NULL otherwise.
453 bus_selinux_init_connection_id (DBusConnection *connection,
460 if (!selinux_enabled)
463 if (!bus_connection_read_selinux_context (connection, &con))
465 dbus_set_error (error, DBUS_ERROR_FAILED,
466 "Failed to read an SELinux context from connection");
467 _dbus_verbose ("Error getting peer context.\n");
471 _dbus_verbose ("Converting context to SID to store on connection\n");
473 if (avc_context_to_sid (con, &sid) < 0)
478 dbus_set_error (error, DBUS_ERROR_FAILED,
479 "Error getting SID from context: %s\n",
480 _dbus_strerror (errno));
482 _dbus_warn ("Error getting SID from context: %s\n",
483 _dbus_strerror (errno));
490 return BUS_SID_FROM_SELINUX (sid);
493 #endif /* HAVE_SELINUX */
498 * Function for freeing hash table data. These SIDs
499 * should no longer be referenced.
502 bus_selinux_id_table_free_value (BusSELinuxID *sid)
505 /* NULL sometimes due to how DBusHashTable works */
507 bus_selinux_id_unref (sid);
508 #endif /* HAVE_SELINUX */
512 * Creates a new table mapping service names to security ID.
513 * A security ID is a "compiled" security context, a security
514 * context is just a string.
516 * @returns the new table or #NULL if no memory
519 bus_selinux_id_table_new (void)
521 return _dbus_hash_table_new (DBUS_HASH_STRING,
522 (DBusFreeFunction) dbus_free,
523 (DBusFreeFunction) bus_selinux_id_table_free_value);
527 * Hashes a service name and service context into the service SID
528 * table as a string and a SID.
530 * @param service_name is the name of the service.
531 * @param service_context is the context of the service.
532 * @param service_table is the table to hash them into.
533 * @return #FALSE if not enough memory
536 bus_selinux_id_table_insert (DBusHashTable *service_table,
537 const char *service_name,
538 const char *service_context)
545 if (!selinux_enabled)
551 key = _dbus_strdup (service_name);
555 if (avc_context_to_sid ((char *) service_context, &sid) < 0)
557 _dbus_assert (errno == ENOMEM);
561 if (!_dbus_hash_table_insert_string (service_table,
563 BUS_SID_FROM_SELINUX (sid)))
566 _dbus_verbose ("Parsed \tservice: %s \n\t\tcontext: %s\n",
570 /* These are owned by the hash, so clear them to avoid unref */
577 if (sid != SECSID_WILD)
586 #endif /* HAVE_SELINUX */
591 * Find the security identifier associated with a particular service
592 * name. Return a pointer to this SID, or #NULL/SECSID_WILD if the
593 * service is not found in the hash table. This should be nearly a
594 * constant time operation. If SELinux support is not available,
595 * always return NULL.
597 * @param service_table the hash table to check for service name.
598 * @param service_name the name of the service to look for.
599 * @returns the SELinux ID associated with the service
602 bus_selinux_id_table_lookup (DBusHashTable *service_table,
603 const DBusString *service_name)
608 sid = SECSID_WILD; /* default context */
610 if (!selinux_enabled)
613 _dbus_verbose ("Looking up service SID for %s\n",
614 _dbus_string_get_const_data (service_name));
616 sid = _dbus_hash_table_lookup_string (service_table,
617 _dbus_string_get_const_data (service_name));
619 if (sid == SECSID_WILD)
620 _dbus_verbose ("Service %s not found\n",
621 _dbus_string_get_const_data (service_name));
623 _dbus_verbose ("Service %s found\n",
624 _dbus_string_get_const_data (service_name));
626 return BUS_SID_FROM_SELINUX (sid);
627 #endif /* HAVE_SELINUX */
632 * Copy security ID table mapping from one table into another.
634 * @param dest the table to copy into
635 * @param override the table to copy from
636 * @returns #FALSE if out of memory
640 bus_selinux_id_table_copy_over (DBusHashTable *dest,
641 DBusHashTable *override)
648 _dbus_hash_iter_init (override, &iter);
649 while (_dbus_hash_iter_next (&iter))
651 key = _dbus_hash_iter_get_string_key (&iter);
652 sid = _dbus_hash_iter_get_value (&iter);
654 key_copy = _dbus_strdup (key);
655 if (key_copy == NULL)
658 if (!_dbus_hash_table_insert_string (dest,
662 dbus_free (key_copy);
666 bus_selinux_id_ref (sid);
671 #endif /* HAVE_SELINUX */
674 * Creates the union of the two tables (each table maps a service
675 * name to a security ID). In case of the same service name in
676 * both tables, the security ID from "override" will be used.
678 * @param base the base table
679 * @param override the table that takes precedence in the merge
680 * @returns the new table, or #NULL if out of memory
683 bus_selinux_id_table_union (DBusHashTable *base,
684 DBusHashTable *override)
686 DBusHashTable *combined_table;
688 combined_table = bus_selinux_id_table_new ();
690 if (combined_table == NULL)
694 if (!selinux_enabled)
695 return combined_table;
697 if (!bus_selinux_id_table_copy_over (combined_table, base))
699 _dbus_hash_table_unref (combined_table);
703 if (!bus_selinux_id_table_copy_over (combined_table, override))
705 _dbus_hash_table_unref (combined_table);
708 #endif /* HAVE_SELINUX */
710 return combined_table;
714 * Get the SELinux policy root. This is used to find the D-BUS
715 * specific config file within the policy.
718 bus_selinux_get_policy_root (void)
721 return selinux_policy_root ();
724 #endif /* HAVE_SELINUX */
728 * For debugging: Print out the current hash table of service SIDs.
731 bus_selinux_id_table_print (DBusHashTable *service_table)
733 #ifdef DBUS_ENABLE_VERBOSE_MODE
737 if (!selinux_enabled)
740 _dbus_verbose ("Service SID Table:\n");
741 _dbus_hash_iter_init (service_table, &iter);
742 while (_dbus_hash_iter_next (&iter))
744 const char *key = _dbus_hash_iter_get_string_key (&iter);
745 security_id_t sid = _dbus_hash_iter_get_value (&iter);
746 _dbus_verbose ("The key is %s\n", key);
747 _dbus_verbose ("The context is %s\n", sid->ctx);
748 _dbus_verbose ("The refcount is %d\n", sid->refcnt);
750 #endif /* HAVE_SELINUX */
751 #endif /* DBUS_ENABLE_VERBOSE_MODE */
755 #ifdef DBUS_ENABLE_VERBOSE_MODE
758 * Print out some AVC statistics.
761 bus_avc_print_stats (void)
763 struct avc_cache_stats cstats;
765 if (!selinux_enabled)
768 _dbus_verbose ("AVC Statistics:\n");
769 avc_cache_stats (&cstats);
771 _dbus_verbose ("AVC Cache Statistics:\n");
772 _dbus_verbose ("Entry lookups: %d\n", cstats.entry_lookups);
773 _dbus_verbose ("Entry hits: %d\n", cstats.entry_hits);
774 _dbus_verbose ("Entry misses %d\n", cstats.entry_misses);
775 _dbus_verbose ("Entry discards: %d\n", cstats.entry_discards);
776 _dbus_verbose ("CAV lookups: %d\n", cstats.cav_lookups);
777 _dbus_verbose ("CAV hits: %d\n", cstats.cav_hits);
778 _dbus_verbose ("CAV probes: %d\n", cstats.cav_probes);
779 _dbus_verbose ("CAV misses: %d\n", cstats.cav_misses);
781 #endif /* HAVE_SELINUX */
782 #endif /* DBUS_ENABLE_VERBOSE_MODE */
786 * Destroy the AVC before we terminate.
789 bus_selinux_shutdown (void)
792 if (!selinux_enabled)
796 bus_sid = SECSID_WILD;
798 #ifdef DBUS_ENABLE_VERBOSE_MODE
799 bus_avc_print_stats ();
800 #endif /* DBUS_ENABLE_VERBOSE_MODE */
803 #endif /* HAVE_SELINUX */