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. */
64static dbus_bool_t selinux_enabled = FALSE;
65
66/* Store an avc_entry_ref to speed AVC decisions. */
67static struct avc_entry_ref aeref;
68
69/* Store the SID of the bus itself to use as the default. */
70static security_id_t bus_sid = SECSID_WILD;
71
72/* Thread to listen for SELinux status changes via netlink. */
73static pthread_t avc_notify_thread;
74
75/* Prototypes for AVC callback functions.  */
76static void log_callback (const char *fmt, ...);
77static void log_audit_callback (void *data, security_class_t class, char *buf, size_t bufleft);
78static void *avc_create_thread (void (*run) (void));
79static void avc_stop_thread (void *thread);
80static void *avc_alloc_lock (void);
81static void avc_get_lock (void *lock);
82static void avc_release_lock (void *lock);
83static void avc_free_lock (void *lock);
84
85/* AVC callback structures for use in avc_init.  */
86static const struct avc_memory_callback mem_cb =
87{
88  .func_malloc = dbus_malloc,
89  .func_free = dbus_free
90};
91static const struct avc_log_callback log_cb =
92{
93  .func_log = log_callback,
94  .func_audit = log_audit_callback
95};
96static const struct avc_thread_callback thread_cb =
97{
98  .func_create_thread = avc_create_thread,
99  .func_stop_thread = avc_stop_thread
100};
101static 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
121static int audit_fd = -1;
122#endif
123
124void
125bus_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
143static void
144log_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 */
175static int
176policy_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 */
189static void
190log_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 */
216static void *
217avc_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.  */
231static void
232avc_stop_thread (void *thread)
233{
234  pthread_cancel (*(pthread_t *) thread);
235}
236
237/* Allocate a new AVC lock.  */
238static void *
239avc_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.  */
255static void
256avc_get_lock (void *lock)
257{
258  pthread_mutex_lock (lock);
259}
260
261/* Release an AVC lock.  */
262static void
263avc_release_lock (void *lock)
264{
265  pthread_mutex_unlock (lock);
266}
267
268/* Free an AVC lock.  */
269static void
270avc_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 */
281dbus_bool_t
282bus_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 */
294dbus_bool_t
295bus_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 */
321dbus_bool_t
322bus_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 */
387void
388bus_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
400void
401bus_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
430static dbus_bool_t
431bus_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 */
473dbus_bool_t
474bus_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 */
539dbus_bool_t
540bus_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
654dbus_bool_t
655bus_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
698static dbus_bool_t
699bus_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 */
733BusSELinuxID*
734bus_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 */
782static void
783bus_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 */
799DBusHashTable*
800bus_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 */
816dbus_bool_t
817bus_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 */
890BusSELinuxID*
891bus_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 */
924const char *
925bus_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 */
937void
938bus_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 */
967static void
968bus_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 */
995void
996bus_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 */
1033dbus_bool_t
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