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 "config.h"
  22 #include <error.h>
  23 #include <errno.h>
  24 #include <libintl.h>
  25 #include <pthread.h>
  26 #include <stdarg.h>
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <syslog.h>
  30 #include <selinux/av_permissions.h>
  31 #include <selinux/avc.h>
  32 #include <selinux/flask.h>
  33 #include <selinux/selinux.h>
  34 #ifdef HAVE_LIBAUDIT
  35 #include <libaudit.h>
  36 #endif
  37
  38 #include "dbg_log.h"
  39 #include "selinux.h"
  40
  41
  42 #ifdef HAVE_SELINUX
  43 /* Global variable to tell if the kernel has SELinux support.  */
  44 int selinux_enabled;
  45
  46 /* Define mappings of access vector permissions to request types.  */
  47 static const int perms[LASTREQ] =
  48 {
  49   [GETPWBYNAME] = NSCD__GETPWD,
  50   [GETPWBYUID] = NSCD__GETPWD,
  51   [GETGRBYNAME] = NSCD__GETGRP,
  52   [GETGRBYGID] = NSCD__GETGRP,
  53   [GETHOSTBYNAME] = NSCD__GETHOST,
  54   [GETHOSTBYNAMEv6] = NSCD__GETHOST,
  55   [GETHOSTBYADDR] = NSCD__GETHOST,
  56   [GETHOSTBYADDRv6] = NSCD__GETHOST,
  57   [GETSTAT] = NSCD__GETSTAT,
  58   [SHUTDOWN] = NSCD__ADMIN,
  59   [INVALIDATE] = NSCD__ADMIN,
  60   [GETFDPW] = NSCD__SHMEMPWD,
  61   [GETFDGR] = NSCD__SHMEMGRP,
  62   [GETFDHST] = NSCD__SHMEMHOST,
  63   [GETAI] = NSCD__GETHOST,
  64   [INITGROUPS] = NSCD__GETGRP
  65 };
  66
  67 /* Store an entry ref to speed AVC decisions.  */
  68 static struct avc_entry_ref aeref;
  69
  70 /* Thread to listen for SELinux status changes via netlink.  */
  71 static pthread_t avc_notify_thread;
  72
  73 #ifdef HAVE_LIBAUDIT
  74 /* Prototype for supporting the audit daemon */
  75 static void log_callback (const char *fmt, ...);
  76 #endif
  77
  78 /* Prototypes for AVC callback functions.  */
  79 static void *avc_create_thread (void (*run) (void));
  80 static void avc_stop_thread (void *thread);
  81 static void *avc_alloc_lock (void);
  82 static void avc_get_lock (void *lock);
  83 static void avc_release_lock (void *lock);
  84 static void avc_free_lock (void *lock);
  85
  86 /* AVC callback structures for use in avc_init.  */
  87 static const struct avc_log_callback log_cb =
  88 {
  89 #ifdef HAVE_LIBAUDIT
  90   .func_log = log_callback,
  91 #else
  92   .func_log = dbg_log,
  93 #endif
  94   .func_audit = NULL
  95 };
  96 static const struct avc_thread_callback thread_cb =
  97 {
  98   .func_create_thread = avc_create_thread,
  99   .func_stop_thread = avc_stop_thread
 100 };
 101 static 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
 109 #ifdef HAVE_LIBAUDIT
 110 /* The audit system's netlink socket descriptor */
 111 static int audit_fd = -1;
 112
 113 /* When an avc denial occurs, log it to audit system */
 114 static void
 115 log_callback (const char *fmt, ...)
 116 {
 117   va_list ap;
 118
 119   va_start (ap, fmt);
 120   audit_log_avc (audit_fd, AUDIT_USER_AVC, fmt, ap);
 121   va_end (ap);
 122 }
 123
 124 /* Initialize the connection to the audit system */
 125 static void
 126 audit_init (void)
 127 {
 128   audit_fd = audit_open ();
 129   if (audit_fd < 0)
 130      dbg_log (_("Failed opening connection to the audit subsystem"));
 131 }
 132 #endif /* HAVE_LIBAUDIT */
 133
 134 /* Determine if we are running on an SELinux kernel. Set selinux_enabled
 135    to the result.  */
 136 void
 137 nscd_selinux_enabled (int *selinux_enabled)
 138 {
 139   *selinux_enabled = is_selinux_enabled ();
 140   if (*selinux_enabled < 0)
 141     {
 142       dbg_log (_("Failed to determine if kernel supports SELinux"));
 143       exit (EXIT_FAILURE);
 144     }
 145 }
 146
 147
 148 /* Create thread for AVC netlink notification.  */
 149 static void *
 150 avc_create_thread (void (*run) (void))
 151 {
 152   int rc;
 153
 154   rc =
 155     pthread_create (&avc_notify_thread, NULL, (void *(*) (void *)) run, NULL);
 156   if (rc != 0)
 157     error (EXIT_FAILURE, rc, _("Failed to start AVC thread"));
 158
 159   return &avc_notify_thread;
 160 }
 161
 162
 163 /* Stop AVC netlink thread.  */
 164 static void
 165 avc_stop_thread (void *thread)
 166 {
 167   pthread_cancel (*(pthread_t *) thread);
 168 }
 169
 170
 171 /* Allocate a new AVC lock.  */
 172 static void *
 173 avc_alloc_lock (void)
 174 {
 175   pthread_mutex_t *avc_mutex;
 176
 177   avc_mutex = malloc (sizeof (pthread_mutex_t));
 178   if (avc_mutex == NULL)
 179     error (EXIT_FAILURE, errno, _("Failed to create AVC lock"));
 180   pthread_mutex_init (avc_mutex, NULL);
 181
 182   return avc_mutex;
 183 }
 184
 185
 186 /* Acquire an AVC lock.  */
 187 static void
 188 avc_get_lock (void *lock)
 189 {
 190   pthread_mutex_lock (lock);
 191 }
 192
 193
 194 /* Release an AVC lock.  */
 195 static void
 196 avc_release_lock (void *lock)
 197 {
 198   pthread_mutex_unlock (lock);
 199 }
 200
 201
 202 /* Free an AVC lock.  */
 203 static void
 204 avc_free_lock (void *lock)
 205 {
 206   pthread_mutex_destroy (lock);
 207   free (lock);
 208 }
 209
 210
 211 /* Initialize the user space access vector cache (AVC) for NSCD along with
 212    log/thread/lock callbacks.  */
 213 void
 214 nscd_avc_init (void)
 215 {
 216   avc_entry_ref_init (&aeref);
 217
 218   if (avc_init ("avc", NULL, &log_cb, &thread_cb, &lock_cb) < 0)
 219     error (EXIT_FAILURE, errno, _("Failed to start AVC"));
 220   else
 221     dbg_log (_("Access Vector Cache (AVC) started"));
 222 #ifdef HAVE_LIBAUDIT
 223   audit_init ();
 224 #endif
 225 }
 226
 227
 228 /* Check the permission from the caller (via getpeercon) to nscd.
 229    Returns 0 if access is allowed, 1 if denied, and -1 on error.  */
 230 int
 231 nscd_request_avc_has_perm (int fd, request_type req)
 232 {
 233   /* Initialize to NULL so we know what to free in case of failure.  */
 234   security_context_t scon = NULL;
 235   security_context_t tcon = NULL;
 236   security_id_t ssid = NULL;
 237   security_id_t tsid = NULL;
 238   int rc = -1;
 239
 240   if (getpeercon (fd, &scon) < 0)
 241     {
 242       dbg_log (_("Error getting context of socket peer"));
 243       goto out;
 244     }
 245   if (getcon (&tcon) < 0)
 246     {
 247       dbg_log (_("Error getting context of nscd"));
 248       goto out;
 249     }
 250   if (avc_context_to_sid (scon, &ssid) < 0
 251       || avc_context_to_sid (tcon, &tsid) < 0)
 252     {
 253       dbg_log (_("Error getting sid from context"));
 254       goto out;
 255     }
 256
 257   rc = avc_has_perm (ssid, tsid, SECCLASS_NSCD, perms[req], &aeref, NULL) < 0;
 258
 259 out:
 260   if (scon)
 261     freecon (scon);
 262   if (tcon)
 263     freecon (tcon);
 264   if (ssid)
 265     sidput (ssid);
 266   if (tsid)
 267     sidput (tsid);
 268
 269   return rc;
 270 }
 271
 272
 273 /* Wrapper to get AVC statistics.  */
 274 void
 275 nscd_avc_cache_stats (struct avc_cache_stats *cstats)
 276 {
 277   avc_cache_stats (cstats);
 278 }
 279
 280
 281 /* Print the AVC statistics to stdout.  */
 282 void
 283 nscd_avc_print_stats (struct avc_cache_stats *cstats)
 284 {
 285   printf (_("\nSELinux AVC Statistics:\n\n"
 286             "%15u  entry lookups\n"
 287             "%15u  entry hits\n"
 288             "%15u  entry misses\n"
 289             "%15u  entry discards\n"
 290             "%15u  CAV lookups\n"
 291             "%15u  CAV hits\n"
 292             "%15u  CAV probes\n"
 293             "%15u  CAV misses\n"),
 294           cstats->entry_lookups, cstats->entry_hits, cstats->entry_misses,
 295           cstats->entry_discards, cstats->cav_lookups, cstats->cav_hits,
 296           cstats->cav_probes, cstats->cav_misses);
 297 }
 298
 299
 300 /* Clean up the AVC before exiting.  */
 301 void
 302 nscd_avc_destroy (void)
 303 {
 304   avc_destroy ();
 305 #ifdef HAVE_LIBAUDIT
 306   audit_close (audit_fd);
 307 #endif
 308 }
 309
 310 #endif /* HAVE_SELINUX */