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 * Return whether or not SELinux is enabled; must be
195 * called after bus_selinux_init.
198 bus_selinux_enabled (void)
201 return selinux_enabled;
204 #endif /* HAVE_SELINUX */
208 * Initialize the user space access vector cache (AVC) for D-BUS and set up
212 bus_selinux_init (void)
218 _dbus_assert (bus_sid == SECSID_WILD);
220 /* Determine if we are running an SELinux kernel. */
221 r = is_selinux_enabled ();
224 _dbus_warn ("Could not tell if SELinux is enabled: %s\n",
225 _dbus_strerror (errno));
229 selinux_enabled = r != 0;
231 if (!selinux_enabled)
233 _dbus_verbose ("SELinux not enabled in this kernel.\n");
237 _dbus_verbose ("SELinux is enabled in this kernel.\n");
239 avc_entry_ref_init (&aeref);
240 if (avc_init ("avc", &mem_cb, &log_cb, &thread_cb, &lock_cb) < 0)
242 _dbus_warn ("Failed to start Access Vector Cache (AVC).\n");
247 openlog ("dbus", LOG_PERROR, LOG_USER);
248 _dbus_verbose ("Access Vector Cache (AVC) started.\n");
251 if (avc_add_callback (policy_reload_callback, AVC_CALLBACK_RESET,
252 NULL, NULL, 0, 0) < 0)
254 _dbus_warn ("Failed to add policy reload callback: %s\n",
255 _dbus_strerror (errno));
261 bus_sid = SECSID_WILD;
263 if (getcon (&bus_context) < 0)
265 _dbus_verbose ("Error getting context of bus: %s\n",
266 _dbus_strerror (errno));
270 if (avc_context_to_sid (bus_context, &bus_sid) < 0)
272 _dbus_verbose ("Error getting SID from bus context: %s\n",
273 _dbus_strerror (errno));
274 freecon (bus_context);
278 freecon (bus_context);
283 #endif /* HAVE_SELINUX */
287 * Decrement SID reference count.
289 * @param sid the SID to decrement
292 bus_selinux_id_unref (BusSELinuxID *sid)
295 if (!selinux_enabled)
298 _dbus_assert (sid != NULL);
300 sidput (SELINUX_SID_FROM_BUS (sid));
301 #endif /* HAVE_SELINUX */
305 bus_selinux_id_ref (BusSELinuxID *sid)
308 if (!selinux_enabled)
311 _dbus_assert (sid != NULL);
313 sidget (SELINUX_SID_FROM_BUS (sid));
314 #endif /* HAVE_SELINUX */
318 * Determine if the SELinux security policy allows the given sender
319 * security context to go to the given recipient security context.
320 * This function determines if the requested permissions are to be
321 * granted from the connection to the message bus or to another
322 * optionally supplied security identifier (e.g. for a service
323 * context). Currently these permissions are either send_msg or
324 * acquire_svc in the dbus class.
326 * @param sender_sid source security context
327 * @param override_sid is the target security context. If SECSID_WILD this will
328 * use the context of the bus itself (e.g. the default).
329 * @param target_class is the target security class.
330 * @param requested is the requested permissions.
331 * @returns #TRUE if security policy allows the send.
335 bus_selinux_check (BusSELinuxID *sender_sid,
336 BusSELinuxID *override_sid,
337 security_class_t target_class,
338 access_vector_t requested)
340 if (!selinux_enabled)
343 /* Make the security check. AVC checks enforcing mode here as well. */
344 if (avc_has_perm (SELINUX_SID_FROM_BUS (sender_sid),
346 SELINUX_SID_FROM_BUS (override_sid) :
347 SELINUX_SID_FROM_BUS (bus_sid),
348 target_class, requested, &aeref, NULL) < 0)
350 _dbus_verbose ("SELinux denying due to security policy.\n");
356 #endif /* HAVE_SELINUX */
359 * Returns true if the given connection can acquire a service,
360 * assuming the given security ID is needed for that service.
362 * @param connection connection that wants to own the service
363 * @param service_sid the SID of the service from the table
364 * @returns #TRUE if acquire is permitted.
367 bus_selinux_allows_acquire_service (DBusConnection *connection,
368 BusSELinuxID *service_sid)
371 BusSELinuxID *connection_sid;
373 if (!selinux_enabled)
376 connection_sid = bus_connection_get_selinux_id (connection);
378 return bus_selinux_check (connection_sid,
384 #endif /* HAVE_SELINUX */
388 * Check if SELinux security controls allow the message to be sent to a
389 * particular connection based on the security context of the sender and
390 * that of the receiver. The destination connection need not be the
391 * addressed recipient, it could be an "eavesdropper"
393 * @param sender the sender of the message.
394 * @param proposed_recipient the connection the message is to be sent to.
395 * @returns whether to allow the send
398 bus_selinux_allows_send (DBusConnection *sender,
399 DBusConnection *proposed_recipient)
402 BusSELinuxID *recipient_sid;
403 BusSELinuxID *sender_sid;
405 if (!selinux_enabled)
408 sender_sid = bus_connection_get_selinux_id (sender);
409 /* A NULL proposed_recipient means the bus itself. */
410 if (proposed_recipient)
411 recipient_sid = bus_connection_get_selinux_id (proposed_recipient);
413 recipient_sid = BUS_SID_FROM_SELINUX (bus_sid);
415 return bus_selinux_check (sender_sid, recipient_sid,
416 SECCLASS_DBUS, DBUS__SEND_MSG);
419 #endif /* HAVE_SELINUX */
423 * Gets the security context of a connection to the bus. It is up to
424 * the caller to freecon() when they are done.
426 * @param connection the connection to get the context of.
427 * @param con the location to store the security context.
428 * @returns #TRUE if context is successfully obtained.
432 bus_connection_read_selinux_context (DBusConnection *connection,
437 if (!selinux_enabled)
440 _dbus_assert (connection != NULL);
442 if (!dbus_connection_get_unix_fd (connection, &fd))
444 _dbus_verbose ("Failed to get file descriptor of socket.\n");
448 if (getpeercon (fd, con) < 0)
450 _dbus_verbose ("Error getting context of socket peer: %s\n",
451 _dbus_strerror (errno));
455 _dbus_verbose ("Successfully read connection context.\n");
458 #endif /* HAVE_SELINUX */
461 * Read the SELinux ID from the connection.
463 * @param connection the connection to read from
464 * @returns the SID if successfully determined, #NULL otherwise.
467 bus_selinux_init_connection_id (DBusConnection *connection,
474 if (!selinux_enabled)
477 if (!bus_connection_read_selinux_context (connection, &con))
479 dbus_set_error (error, DBUS_ERROR_FAILED,
480 "Failed to read an SELinux context from connection");
481 _dbus_verbose ("Error getting peer context.\n");
485 _dbus_verbose ("Converting context to SID to store on connection\n");
487 if (avc_context_to_sid (con, &sid) < 0)
492 dbus_set_error (error, DBUS_ERROR_FAILED,
493 "Error getting SID from context: %s\n",
494 _dbus_strerror (errno));
496 _dbus_warn ("Error getting SID from context: %s\n",
497 _dbus_strerror (errno));
504 return BUS_SID_FROM_SELINUX (sid);
507 #endif /* HAVE_SELINUX */
512 * Function for freeing hash table data. These SIDs
513 * should no longer be referenced.
516 bus_selinux_id_table_free_value (BusSELinuxID *sid)
519 /* NULL sometimes due to how DBusHashTable works */
521 bus_selinux_id_unref (sid);
522 #endif /* HAVE_SELINUX */
526 * Creates a new table mapping service names to security ID.
527 * A security ID is a "compiled" security context, a security
528 * context is just a string.
530 * @returns the new table or #NULL if no memory
533 bus_selinux_id_table_new (void)
535 return _dbus_hash_table_new (DBUS_HASH_STRING,
536 (DBusFreeFunction) dbus_free,
537 (DBusFreeFunction) bus_selinux_id_table_free_value);
541 * Hashes a service name and service context into the service SID
542 * table as a string and a SID.
544 * @param service_name is the name of the service.
545 * @param service_context is the context of the service.
546 * @param service_table is the table to hash them into.
547 * @return #FALSE if not enough memory
550 bus_selinux_id_table_insert (DBusHashTable *service_table,
551 const char *service_name,
552 const char *service_context)
559 if (!selinux_enabled)
565 key = _dbus_strdup (service_name);
569 if (avc_context_to_sid ((char *) service_context, &sid) < 0)
571 _dbus_assert (errno == ENOMEM);
575 if (!_dbus_hash_table_insert_string (service_table,
577 BUS_SID_FROM_SELINUX (sid)))
580 _dbus_verbose ("Parsed \tservice: %s \n\t\tcontext: %s\n",
584 /* These are owned by the hash, so clear them to avoid unref */
591 if (sid != SECSID_WILD)
600 #endif /* HAVE_SELINUX */
605 * Find the security identifier associated with a particular service
606 * name. Return a pointer to this SID, or #NULL/SECSID_WILD if the
607 * service is not found in the hash table. This should be nearly a
608 * constant time operation. If SELinux support is not available,
609 * always return NULL.
611 * @param service_table the hash table to check for service name.
612 * @param service_name the name of the service to look for.
613 * @returns the SELinux ID associated with the service
616 bus_selinux_id_table_lookup (DBusHashTable *service_table,
617 const DBusString *service_name)
622 sid = SECSID_WILD; /* default context */
624 if (!selinux_enabled)
627 _dbus_verbose ("Looking up service SID for %s\n",
628 _dbus_string_get_const_data (service_name));
630 sid = _dbus_hash_table_lookup_string (service_table,
631 _dbus_string_get_const_data (service_name));
633 if (sid == SECSID_WILD)
634 _dbus_verbose ("Service %s not found\n",
635 _dbus_string_get_const_data (service_name));
637 _dbus_verbose ("Service %s found\n",
638 _dbus_string_get_const_data (service_name));
640 return BUS_SID_FROM_SELINUX (sid);
641 #endif /* HAVE_SELINUX */
646 * Copy security ID table mapping from one table into another.
648 * @param dest the table to copy into
649 * @param override the table to copy from
650 * @returns #FALSE if out of memory
654 bus_selinux_id_table_copy_over (DBusHashTable *dest,
655 DBusHashTable *override)
662 _dbus_hash_iter_init (override, &iter);
663 while (_dbus_hash_iter_next (&iter))
665 key = _dbus_hash_iter_get_string_key (&iter);
666 sid = _dbus_hash_iter_get_value (&iter);
668 key_copy = _dbus_strdup (key);
669 if (key_copy == NULL)
672 if (!_dbus_hash_table_insert_string (dest,
676 dbus_free (key_copy);
680 bus_selinux_id_ref (sid);
685 #endif /* HAVE_SELINUX */
688 * Creates the union of the two tables (each table maps a service
689 * name to a security ID). In case of the same service name in
690 * both tables, the security ID from "override" will be used.
692 * @param base the base table
693 * @param override the table that takes precedence in the merge
694 * @returns the new table, or #NULL if out of memory
697 bus_selinux_id_table_union (DBusHashTable *base,
698 DBusHashTable *override)
700 DBusHashTable *combined_table;
702 combined_table = bus_selinux_id_table_new ();
704 if (combined_table == NULL)
708 if (!selinux_enabled)
709 return combined_table;
711 if (!bus_selinux_id_table_copy_over (combined_table, base))
713 _dbus_hash_table_unref (combined_table);
717 if (!bus_selinux_id_table_copy_over (combined_table, override))
719 _dbus_hash_table_unref (combined_table);
722 #endif /* HAVE_SELINUX */
724 return combined_table;
728 * Get the SELinux policy root. This is used to find the D-BUS
729 * specific config file within the policy.
732 bus_selinux_get_policy_root (void)
735 return selinux_policy_root ();
738 #endif /* HAVE_SELINUX */
742 * For debugging: Print out the current hash table of service SIDs.
745 bus_selinux_id_table_print (DBusHashTable *service_table)
747 #ifdef DBUS_ENABLE_VERBOSE_MODE
751 if (!selinux_enabled)
754 _dbus_verbose ("Service SID Table:\n");
755 _dbus_hash_iter_init (service_table, &iter);
756 while (_dbus_hash_iter_next (&iter))
758 const char *key = _dbus_hash_iter_get_string_key (&iter);
759 security_id_t sid = _dbus_hash_iter_get_value (&iter);
760 _dbus_verbose ("The key is %s\n", key);
761 _dbus_verbose ("The context is %s\n", sid->ctx);
762 _dbus_verbose ("The refcount is %d\n", sid->refcnt);
764 #endif /* HAVE_SELINUX */
765 #endif /* DBUS_ENABLE_VERBOSE_MODE */
769 #ifdef DBUS_ENABLE_VERBOSE_MODE
772 * Print out some AVC statistics.
775 bus_avc_print_stats (void)
777 struct avc_cache_stats cstats;
779 if (!selinux_enabled)
782 _dbus_verbose ("AVC Statistics:\n");
783 avc_cache_stats (&cstats);
785 _dbus_verbose ("AVC Cache Statistics:\n");
786 _dbus_verbose ("Entry lookups: %d\n", cstats.entry_lookups);
787 _dbus_verbose ("Entry hits: %d\n", cstats.entry_hits);
788 _dbus_verbose ("Entry misses %d\n", cstats.entry_misses);
789 _dbus_verbose ("Entry discards: %d\n", cstats.entry_discards);
790 _dbus_verbose ("CAV lookups: %d\n", cstats.cav_lookups);
791 _dbus_verbose ("CAV hits: %d\n", cstats.cav_hits);
792 _dbus_verbose ("CAV probes: %d\n", cstats.cav_probes);
793 _dbus_verbose ("CAV misses: %d\n", cstats.cav_misses);
795 #endif /* HAVE_SELINUX */
796 #endif /* DBUS_ENABLE_VERBOSE_MODE */
800 * Destroy the AVC before we terminate.
803 bus_selinux_shutdown (void)
806 if (!selinux_enabled)
810 bus_sid = SECSID_WILD;
812 #ifdef DBUS_ENABLE_VERBOSE_MODE
813 bus_avc_print_stats ();
814 #endif /* DBUS_ENABLE_VERBOSE_MODE */
817 #endif /* HAVE_SELINUX */