about summary refs log tree commit diff
path: root/nscd/selinux.c
blob: 77651e05c3abceb1d6b451605a0d0b94382843ca (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
/* SELinux access controls for nscd.
   Copyright (C) 2004 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Matthew Rickard <mjricka@epoch.ncsc.mil>, 2004.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <error.h>
#include <errno.h>
#include <libintl.h>
#include <pthread.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <syslog.h>
#include <selinux/av_permissions.h>
#include <selinux/avc.h>
#include <selinux/flask.h>
#include <selinux/selinux.h>

#include "dbg_log.h"
#include "selinux.h"


#ifdef HAVE_SELINUX
/* Global variable to tell if the kernel has SELinux support.  */
int selinux_enabled;

/* Define mappings of access vector permissions to request types.  */
static const int perms[LASTREQ] =
{
  [GETPWBYNAME] = NSCD__GETPWD,
  [GETPWBYUID] = NSCD__GETPWD,
  [GETGRBYNAME] = NSCD__GETGRP,
  [GETGRBYGID] = NSCD__GETGRP,
  [GETHOSTBYNAME] = NSCD__GETHOST,
  [GETHOSTBYNAMEv6] = NSCD__GETHOST,
  [GETHOSTBYADDR] = NSCD__GETHOST,
  [GETHOSTBYADDRv6] = NSCD__GETHOST,
  [GETSTAT] = NSCD__GETSTAT,
  [SHUTDOWN] = NSCD__ADMIN,
  [INVALIDATE] = NSCD__ADMIN,
  [GETFDPW] = NSCD__SHMEMPWD,
  [GETFDGR] = NSCD__SHMEMGRP,
  [GETFDHST] = NSCD__SHMEMHOST,
  [GETAI] = NSCD__GETHOST,
  [INITGROUPS] = NSCD__GETGRP
};

/* Store an entry ref to speed AVC decisions.  */
static struct avc_entry_ref aeref;

/* Thread to listen for SELinux status changes via netlink.  */
static pthread_t avc_notify_thread;

/* Prototypes for AVC callback functions.  */
static void *avc_create_thread (void (*run) (void));
static void avc_stop_thread (void *thread);
static void *avc_alloc_lock (void);
static void avc_get_lock (void *lock);
static void avc_release_lock (void *lock);
static void avc_free_lock (void *lock);

/* AVC callback structures for use in avc_init.  */
static const struct avc_log_callback log_cb =
{
  .func_log = dbg_log,
  .func_audit = NULL
};
static const struct avc_thread_callback thread_cb =
{
  .func_create_thread = avc_create_thread,
  .func_stop_thread = avc_stop_thread
};
static const struct avc_lock_callback lock_cb =
{
  .func_alloc_lock = avc_alloc_lock,
  .func_get_lock = avc_get_lock,
  .func_release_lock = avc_release_lock,
  .func_free_lock = avc_free_lock
};


/* Determine if we are running on an SELinux kernel. Set selinux_enabled
   to the result.  */
void
nscd_selinux_enabled (int *selinux_enabled)
{
  *selinux_enabled = is_selinux_enabled ();
  if (*selinux_enabled < 0)
    {
      dbg_log (_("Failed to determine if kernel supports SELinux"));
      exit (EXIT_FAILURE);
    }
}


/* Create thread for AVC netlink notification.  */
static void *
avc_create_thread (void (*run) (void))
{
  int rc;

  rc =
    pthread_create (&avc_notify_thread, NULL, (void *(*) (void *)) run, NULL);
  if (rc != 0)
    error (EXIT_FAILURE, rc, _("Failed to start AVC thread"));

  return &avc_notify_thread;
}


/* Stop AVC netlink thread.  */
static void
avc_stop_thread (void *thread)
{
  pthread_cancel (*(pthread_t *) thread);
}


/* Allocate a new AVC lock.  */
static void *
avc_alloc_lock (void)
{
  pthread_mutex_t *avc_mutex;

  avc_mutex = malloc (sizeof (pthread_mutex_t));
  if (avc_mutex == NULL)
    error (EXIT_FAILURE, errno, _("Failed to create AVC lock"));
  pthread_mutex_init (avc_mutex, NULL);

  return avc_mutex;
}


/* Acquire an AVC lock.  */
static void
avc_get_lock (void *lock)
{
  pthread_mutex_lock (lock);
}


/* Release an AVC lock.  */
static void
avc_release_lock (void *lock)
{
  pthread_mutex_unlock (lock);
}


/* Free an AVC lock.  */
static void
avc_free_lock (void *lock)
{
  pthread_mutex_destroy (lock);
  free (lock);
}


/* Initialize the user space access vector cache (AVC) for NSCD along with
   log/thread/lock callbacks.  */
void
nscd_avc_init (void)
{
  avc_entry_ref_init (&aeref);

  if (avc_init ("avc", NULL, &log_cb, &thread_cb, &lock_cb) < 0)
    error (EXIT_FAILURE, errno, _("Failed to start AVC"));
  else
    dbg_log (_("Access Vector Cache (AVC) started"));
}


/* Check the permission from the caller (via getpeercon) to nscd.
   Returns 0 if access is allowed, 1 if denied, and -1 on error.  */
int
nscd_request_avc_has_perm (int fd, request_type req)
{
  /* Initialize to NULL so we know what to free in case of failure.  */
  security_context_t scon = NULL;
  security_context_t tcon = NULL;
  security_id_t ssid = NULL;
  security_id_t tsid = NULL;
  int rc = -1;

  if (getpeercon (fd, &scon) < 0)
    {
      dbg_log (_("Error getting context of socket peer"));
      goto out;
    }
  if (getcon (&tcon) < 0)
    {
      dbg_log (_("Error getting context of nscd"));
      goto out;
    }
  if (avc_context_to_sid (scon, &ssid) < 0 ||
      avc_context_to_sid (tcon, &tsid) < 0)
    {
      dbg_log (_("Error getting sid from context"));
      goto out;
    }

  rc = avc_has_perm (ssid, tsid, SECCLASS_NSCD, perms[req], &aeref, NULL) < 0;

out:
  if (scon)
    freecon (scon);
  if (tcon)
    freecon (tcon);
  if (ssid)
    sidput (ssid);
  if (tsid)
    sidput (tsid);

  return rc;
}


/* Wrapper to get AVC statistics.  */
void
nscd_avc_cache_stats (struct avc_cache_stats *cstats)
{
  avc_cache_stats (cstats);
}


/* Print the AVC statistics to stdout.  */
void
nscd_avc_print_stats (struct avc_cache_stats *cstats)
{
  printf (_("\nSELinux AVC Statistics:\n\n"
	    "%15u  entry lookups\n"
	    "%15u  entry hits\n"
	    "%15u  entry misses\n"
	    "%15u  entry discards\n"
	    "%15u  CAV lookups\n"
	    "%15u  CAV hits\n"
	    "%15u  CAV probes\n"
	    "%15u  CAV misses\n"),
	  cstats->entry_lookups, cstats->entry_hits, cstats->entry_misses,
	  cstats->entry_discards, cstats->cav_lookups, cstats->cav_hits,
	  cstats->cav_probes, cstats->cav_misses);
}


/* Clean up the AVC before exiting.  */
void
nscd_avc_destroy (void)
{
  avc_destroy ();
}

#endif /* HAVE_SELINUX */