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 };
  61
  62 /* Store an entry ref to speed AVC decisions.  */
  63 static struct avc_entry_ref aeref;
  64
  65 /* Thread to listen for SELinux status changes via netlink.  */
  66 static pthread_t avc_notify_thread;
  67
  68 /* Prototypes for AVC callback functions.  */
  69 static void *avc_create_thread (void (*run) (void));
  70 static void avc_stop_thread (void *thread);
  71 static void *avc_alloc_lock (void);
  72 static void avc_get_lock (void *lock);
  73 static void avc_release_lock (void *lock);
  74 static void avc_free_lock (void *lock);
  75
  76 /* AVC callback structures for use in avc_init.  */
  77 static const struct avc_log_callback log_cb =
  78 {
  79   .func_log = dbg_log,
  80   .func_audit = NULL
  81 };
  82 static const struct avc_thread_callback thread_cb =
  83 {
  84   .func_create_thread = avc_create_thread,
  85   .func_stop_thread = avc_stop_thread
  86 };
  87 static const struct avc_lock_callback lock_cb =
  88 {
  89   .func_alloc_lock = avc_alloc_lock,
  90   .func_get_lock = avc_get_lock,
  91   .func_release_lock = avc_release_lock,
  92   .func_free_lock = avc_free_lock
  93 };
  94
  95
  96 /* Determine if we are running on an SELinux kernel. Set selinux_enabled
  97    to the result.  */
  98 void
  99 nscd_selinux_enabled (int *selinux_enabled)
 100 {
 101   *selinux_enabled = is_selinux_enabled ();
 102   if (*selinux_enabled < 0)
 103     {
 104       dbg_log (_("Failed to determine if kernel supports SELinux"));
 105       exit (EXIT_FAILURE);
 106     }
 107 }
 108
 109
 110 /* Create thread for AVC netlink notification.  */
 111 static void *
 112 avc_create_thread (void (*run) (void))
 113 {
 114   int rc;
 115
 116   rc =
 117     pthread_create (&avc_notify_thread, NULL, (void *(*) (void *)) run, NULL);
 118   if (rc != 0)
 119     error (EXIT_FAILURE, rc, _("Failed to start AVC thread"));
 120
 121   return &avc_notify_thread;
 122 }
 123
 124
 125 /* Stop AVC netlink thread.  */
 126 static void
 127 avc_stop_thread (void *thread)
 128 {
 129   pthread_cancel (*(pthread_t *) thread);
 130 }
 131
 132
 133 /* Allocate a new AVC lock.  */
 134 static void *
 135 avc_alloc_lock (void)
 136 {
 137   pthread_mutex_t *avc_mutex;
 138
 139   avc_mutex = malloc (sizeof (pthread_mutex_t));
 140   if (avc_mutex == NULL)
 141     error (EXIT_FAILURE, errno, _("Failed to create AVC lock"));
 142   pthread_mutex_init (avc_mutex, NULL);
 143
 144   return avc_mutex;
 145 }
 146
 147
 148 /* Acquire an AVC lock.  */
 149 static void
 150 avc_get_lock (void *lock)
 151 {
 152   pthread_mutex_lock (lock);
 153 }
 154
 155
 156 /* Release an AVC lock.  */
 157 static void
 158 avc_release_lock (void *lock)
 159 {
 160   pthread_mutex_unlock (lock);
 161 }
 162
 163
 164 /* Free an AVC lock.  */
 165 static void
 166 avc_free_lock (void *lock)
 167 {
 168   pthread_mutex_destroy (lock);
 169   free (lock);
 170 }
 171
 172
 173 /* Initialize the user space access vector cache (AVC) for NSCD along with
 174    log/thread/lock callbacks.  */
 175 void
 176 nscd_avc_init (void)
 177 {
 178   avc_entry_ref_init (&aeref);
 179
 180   if (avc_init ("avc", NULL, &log_cb, &thread_cb, &lock_cb) < 0)
 181     error (EXIT_FAILURE, errno, _("Failed to start AVC"));
 182   else
 183     dbg_log (_("Access Vector Cache (AVC) started"));
 184 }
 185
 186
 187 /* Check the permission from the caller (via getpeercon) to nscd.
 188    Returns 0 if access is allowed, 1 if denied, and -1 on error.  */
 189 int
 190 nscd_request_avc_has_perm (int fd, request_type req)
 191 {
 192   /* Initialize to NULL so we know what to free in case of failure.  */
 193   security_context_t scon = NULL;
 194   security_context_t tcon = NULL;
 195   security_id_t ssid = NULL;
 196   security_id_t tsid = NULL;
 197   int rc = -1;
 198
 199   if (getpeercon (fd, &scon) < 0)
 200     {
 201       dbg_log (_("Error getting context of socket peer"));
 202       goto out;
 203     }
 204   if (getcon (&tcon) < 0)
 205     {
 206       dbg_log (_("Error getting context of nscd"));
 207       goto out;
 208     }
 209   if (avc_context_to_sid (scon, &ssid) < 0 ||
 210       avc_context_to_sid (tcon, &tsid) < 0)
 211     {
 212       dbg_log (_("Error getting sid from context"));
 213       goto out;
 214     }
 215
 216   rc = avc_has_perm (ssid, tsid, SECCLASS_NSCD, perms[req], &aeref, NULL) < 0;
 217
 218 out:
 219   if (scon)
 220     freecon (scon);
 221   if (tcon)
 222     freecon (tcon);
 223   if (ssid)
 224     sidput (ssid);
 225   if (tsid)
 226     sidput (tsid);
 227
 228   return rc;
 229 }
 230
 231
 232 /* Wrapper to get AVC statistics.  */
 233 void
 234 nscd_avc_cache_stats (struct avc_cache_stats *cstats)
 235 {
 236   avc_cache_stats (cstats);
 237 }
 238
 239
 240 /* Print the AVC statistics to stdout.  */
 241 void
 242 nscd_avc_print_stats (struct avc_cache_stats *cstats)
 243 {
 244   printf (_("\nSELinux AVC Statistics:\n\n"
 245             "%15u  entry lookups\n"
 246             "%15u  entry hits\n"
 247             "%15u  entry misses\n"
 248             "%15u  entry discards\n"
 249             "%15u  CAV lookups\n"
 250             "%15u  CAV hits\n"
 251             "%15u  CAV probes\n"
 252             "%15u  CAV misses\n"),
 253           cstats->entry_lookups, cstats->entry_hits, cstats->entry_misses,
 254           cstats->entry_discards, cstats->cav_lookups, cstats->cav_hits,
 255           cstats->cav_probes, cstats->cav_misses);
 256 }
 257
 258
 259 /* Clean up the AVC before exiting.  */
 260 void
 261 nscd_avc_destroy (void)
 262 {
 263   avc_destroy ();
 264 }
 265
 266 #endif /* HAVE_SELINUX */