nscd/selinux.c

   1 /* SELinux access controls for nscd.
   2    Copyright (C) 2004 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Matthew Rickard <mjricka@epoch.ncsc.mil>, 2004.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <error.h>
  22 #include <errno.h>
  23 #include <libintl.h>
  24 #include <pthread.h>
  25 #include <stdarg.h>
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <syslog.h>
  29 #include <selinux/av_permissions.h>
  30 #include <selinux/avc.h>
  31 #include <selinux/flask.h>
  32 #include <selinux/selinux.h>
  33
  34 #include "dbg_log.h"
  35 #include "selinux.h"
  36
  37
  38 #ifdef HAVE_SELINUX
  39 /* Global variable to tell if the kernel has SELinux support.  */
  40 int selinux_enabled;
  41
  42 /* Define mappings of access vector permissions to request types.  */
  43 static const int perms[LASTREQ] =
  44 {
  45   [GETPWBYNAME] = NSCD__GETPWD,
  46   [GETPWBYUID] = NSCD__GETPWD,
  47   [GETGRBYNAME] = NSCD__GETGRP,
  48   [GETGRBYGID] = NSCD__GETGRP,
  49   [GETHOSTBYNAME] = NSCD__GETHOST,
  50   [GETHOSTBYNAMEv6] = NSCD__GETHOST,
  51   [GETHOSTBYADDR] = NSCD__GETHOST,
  52   [GETHOSTBYADDRv6] = NSCD__GETHOST,
  53   [GETSTAT] = NSCD__GETSTAT,
  54   [SHUTDOWN] = NSCD__ADMIN,
  55   [INVALIDATE] = NSCD__ADMIN,
  56   [GETFDPW] = NSCD__SHMEMPWD,
  57   [GETFDGR] = NSCD__SHMEMGRP,
  58   [GETFDHST] = NSCD__SHMEMHOST,
  59   [GETAI] = NSCD__GETHOST,
  60   [INITGROUPS] = NSCD__GETGRP
  61 };
  62
  63 /* Store an entry ref to speed AVC decisions.  */
  64 static struct avc_entry_ref aeref;
  65
  66 /* Thread to listen for SELinux status changes via netlink.  */
  67 static pthread_t avc_notify_thread;
  68
  69 /* Prototypes for AVC callback functions.  */
  70 static void *avc_create_thread (void (*run) (void));
  71 static void avc_stop_thread (void *thread);
  72 static void *avc_alloc_lock (void);
  73 static void avc_get_lock (void *lock);
  74 static void avc_release_lock (void *lock);
  75 static void avc_free_lock (void *lock);
  76
  77 /* AVC callback structures for use in avc_init.  */
  78 static const struct avc_log_callback log_cb =
  79 {
  80   .func_log = dbg_log,
  81   .func_audit = NULL
  82 };
  83 static const struct avc_thread_callback thread_cb =
  84 {
  85   .func_create_thread = avc_create_thread,
  86   .func_stop_thread = avc_stop_thread
  87 };
  88 static const struct avc_lock_callback lock_cb =
  89 {
  90   .func_alloc_lock = avc_alloc_lock,
  91   .func_get_lock = avc_get_lock,
  92   .func_release_lock = avc_release_lock,
  93   .func_free_lock = avc_free_lock
  94 };
  95
  96
  97 /* Determine if we are running on an SELinux kernel. Set selinux_enabled
  98    to the result.  */
  99 void
 100 nscd_selinux_enabled (int *selinux_enabled)
 101 {
 102   *selinux_enabled = is_selinux_enabled ();
 103   if (*selinux_enabled < 0)
 104     {
 105       dbg_log (_("Failed to determine if kernel supports SELinux"));
 106       exit (EXIT_FAILURE);
 107     }
 108 }
 109
 110
 111 /* Create thread for AVC netlink notification.  */
 112 static void *
 113 avc_create_thread (void (*run) (void))
 114 {
 115   int rc;
 116
 117   rc =
 118     pthread_create (&avc_notify_thread, NULL, (void *(*) (void *)) run, NULL);
 119   if (rc != 0)
 120     error (EXIT_FAILURE, rc, _("Failed to start AVC thread"));
 121
 122   return &avc_notify_thread;
 123 }
 124
 125
 126 /* Stop AVC netlink thread.  */
 127 static void
 128 avc_stop_thread (void *thread)
 129 {
 130   pthread_cancel (*(pthread_t *) thread);
 131 }
 132
 133
 134 /* Allocate a new AVC lock.  */
 135 static void *
 136 avc_alloc_lock (void)
 137 {
 138   pthread_mutex_t *avc_mutex;
 139
 140   avc_mutex = malloc (sizeof (pthread_mutex_t));
 141   if (avc_mutex == NULL)
 142     error (EXIT_FAILURE, errno, _("Failed to create AVC lock"));
 143   pthread_mutex_init (avc_mutex, NULL);
 144
 145   return avc_mutex;
 146 }
 147
 148
 149 /* Acquire an AVC lock.  */
 150 static void
 151 avc_get_lock (void *lock)
 152 {
 153   pthread_mutex_lock (lock);
 154 }
 155
 156
 157 /* Release an AVC lock.  */
 158 static void
 159 avc_release_lock (void *lock)
 160 {
 161   pthread_mutex_unlock (lock);
 162 }
 163
 164
 165 /* Free an AVC lock.  */
 166 static void
 167 avc_free_lock (void *lock)
 168 {
 169   pthread_mutex_destroy (lock);
 170   free (lock);
 171 }
 172
 173
 174 /* Initialize the user space access vector cache (AVC) for NSCD along with
 175    log/thread/lock callbacks.  */
 176 void
 177 nscd_avc_init (void)
 178 {
 179   avc_entry_ref_init (&aeref);
 180
 181   if (avc_init ("avc", NULL, &log_cb, &thread_cb, &lock_cb) < 0)
 182     error (EXIT_FAILURE, errno, _("Failed to start AVC"));
 183   else
 184     dbg_log (_("Access Vector Cache (AVC) started"));
 185 }
 186
 187
 188 /* Check the permission from the caller (via getpeercon) to nscd.
 189    Returns 0 if access is allowed, 1 if denied, and -1 on error.  */
 190 int
 191 nscd_request_avc_has_perm (int fd, request_type req)
 192 {
 193   /* Initialize to NULL so we know what to free in case of failure.  */
 194   security_context_t scon = NULL;
 195   security_context_t tcon = NULL;
 196   security_id_t ssid = NULL;
 197   security_id_t tsid = NULL;
 198   int rc = -1;
 199
 200   if (getpeercon (fd, &scon) < 0)
 201     {
 202       dbg_log (_("Error getting context of socket peer"));
 203       goto out;
 204     }
 205   if (getcon (&tcon) < 0)
 206     {
 207       dbg_log (_("Error getting context of nscd"));
 208       goto out;
 209     }
 210   if (avc_context_to_sid (scon, &ssid) < 0
 211       || avc_context_to_sid (tcon, &tsid) < 0)
 212     {
 213       dbg_log (_("Error getting sid from context"));
 214       goto out;
 215     }
 216
 217   rc = avc_has_perm (ssid, tsid, SECCLASS_NSCD, perms[req], &aeref, NULL) < 0;
 218
 219 out:
 220   if (scon)
 221     freecon (scon);
 222   if (tcon)
 223     freecon (tcon);
 224   if (ssid)
 225     sidput (ssid);
 226   if (tsid)
 227     sidput (tsid);
 228
 229   return rc;
 230 }
 231
 232
 233 /* Wrapper to get AVC statistics.  */
 234 void
 235 nscd_avc_cache_stats (struct avc_cache_stats *cstats)
 236 {
 237   avc_cache_stats (cstats);
 238 }
 239
 240
 241 /* Print the AVC statistics to stdout.  */
 242 void
 243 nscd_avc_print_stats (struct avc_cache_stats *cstats)
 244 {
 245   printf (_("\nSELinux AVC Statistics:\n\n"
 246             "%15u  entry lookups\n"
 247             "%15u  entry hits\n"
 248             "%15u  entry misses\n"
 249             "%15u  entry discards\n"
 250             "%15u  CAV lookups\n"
 251             "%15u  CAV hits\n"
 252             "%15u  CAV probes\n"
 253             "%15u  CAV misses\n"),
 254           cstats->entry_lookups, cstats->entry_hits, cstats->entry_misses,
 255           cstats->entry_discards, cstats->cav_lookups, cstats->cav_hits,
 256           cstats->cav_probes, cstats->cav_misses);
 257 }
 258
 259
 260 /* Clean up the AVC before exiting.  */
 261 void
 262 nscd_avc_destroy (void)
 263 {
 264   avc_destroy ();
 265 }
 266
 267 #endif /* HAVE_SELINUX */