1 /* SELinux access controls for nscd.
2 Copyright (C) 2004,2005,2006,2007,2009,2011 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Matthew Rickard <mjricka@epoch.ncsc.mil>, 2004.
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.
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.
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
31 #include <sys/prctl.h>
32 #include <selinux/av_permissions.h>
33 #include <selinux/avc.h>
34 #include <selinux/flask.h>
35 #include <selinux/selinux.h>
37 # include <libaudit.h>
45 /* Global variable to tell if the kernel has SELinux support. */
48 /* Define mappings of access vector permissions to request types. */
49 static const access_vector_t perms[LASTREQ] =
51 [GETPWBYNAME] = NSCD__GETPWD,
52 [GETPWBYUID] = NSCD__GETPWD,
53 [GETGRBYNAME] = NSCD__GETGRP,
54 [GETGRBYGID] = NSCD__GETGRP,
55 [GETHOSTBYNAME] = NSCD__GETHOST,
56 [GETHOSTBYNAMEv6] = NSCD__GETHOST,
57 [GETHOSTBYADDR] = NSCD__GETHOST,
58 [GETHOSTBYADDRv6] = NSCD__GETHOST,
59 [GETSTAT] = NSCD__GETSTAT,
60 [SHUTDOWN] = NSCD__ADMIN,
61 [INVALIDATE] = NSCD__ADMIN,
62 [GETFDPW] = NSCD__SHMEMPWD,
63 [GETFDGR] = NSCD__SHMEMGRP,
64 [GETFDHST] = NSCD__SHMEMHOST,
65 [GETAI] = NSCD__GETHOST,
66 [INITGROUPS] = NSCD__GETGRP,
68 [GETSERVBYNAME] = NSCD__GETSERV,
69 [GETSERVBYPORT] = NSCD__GETSERV,
70 [GETFDSERV] = NSCD__SHMEMSERV,
72 #ifdef NSCD__GETNETGRP
73 [GETNETGRENT] = NSCD__GETNETGRP,
74 [INNETGR] = NSCD__GETNETGRP,
75 [GETFDNETGR] = NSCD__SHMEMNETGRP,
79 /* Store an entry ref to speed AVC decisions. */
80 static struct avc_entry_ref aeref;
82 /* Thread to listen for SELinux status changes via netlink. */
83 static pthread_t avc_notify_thread;
86 /* Prototype for supporting the audit daemon */
87 static void log_callback (const char *fmt, ...);
90 /* Prototypes for AVC callback functions. */
91 static void *avc_create_thread (void (*run) (void));
92 static void avc_stop_thread (void *thread);
93 static void *avc_alloc_lock (void);
94 static void avc_get_lock (void *lock);
95 static void avc_release_lock (void *lock);
96 static void avc_free_lock (void *lock);
98 /* AVC callback structures for use in avc_init. */
99 static const struct avc_log_callback log_cb =
102 .func_log = log_callback,
108 static const struct avc_thread_callback thread_cb =
110 .func_create_thread = avc_create_thread,
111 .func_stop_thread = avc_stop_thread
113 static const struct avc_lock_callback lock_cb =
115 .func_alloc_lock = avc_alloc_lock,
116 .func_get_lock = avc_get_lock,
117 .func_release_lock = avc_release_lock,
118 .func_free_lock = avc_free_lock
122 /* The audit system's netlink socket descriptor */
123 static int audit_fd = -1;
125 /* When an avc denial occurs, log it to audit system */
127 log_callback (const char *fmt, ...)
135 int e = vasprintf (&buf, fmt, ap);
138 buf = alloca (BUFSIZ);
139 vsnprintf (buf, BUFSIZ, fmt, ap);
142 /* FIXME: need to attribute this to real user, using getuid for now */
143 audit_log_user_avc_message (audit_fd, AUDIT_USER_AVC, buf, NULL, NULL,
153 /* Initialize the connection to the audit system */
157 audit_fd = audit_open ();
159 /* If kernel doesn't support audit, bail out */
160 && errno != EINVAL && errno != EPROTONOSUPPORT && errno != EAFNOSUPPORT)
161 dbg_log (_("Failed opening connection to the audit subsystem: %m"));
166 static const cap_value_t new_cap_list[] =
168 # define nnew_cap_list (sizeof (new_cap_list) / sizeof (new_cap_list[0]))
169 static const cap_value_t tmp_cap_list[] =
170 { CAP_AUDIT_WRITE, CAP_SETUID, CAP_SETGID };
171 # define ntmp_cap_list (sizeof (tmp_cap_list) / sizeof (tmp_cap_list[0]))
174 preserve_capabilities (void)
177 /* Not root, then we cannot preserve anything. */
180 if (prctl (PR_SET_KEEPCAPS, 1) == -1)
182 dbg_log (_("Failed to set keep-capabilities"));
183 error (EXIT_FAILURE, errno, _("prctl(KEEPCAPS) failed"));
187 cap_t tmp_caps = cap_init ();
188 cap_t new_caps = NULL;
189 if (tmp_caps != NULL)
190 new_caps = cap_init ();
192 if (tmp_caps == NULL || new_caps == NULL)
194 if (tmp_caps != NULL)
197 dbg_log (_("Failed to initialize drop of capabilities"));
198 error (EXIT_FAILURE, 0, _("cap_init failed"));
201 /* There is no reason why these should not work. */
202 cap_set_flag (new_caps, CAP_PERMITTED, nnew_cap_list,
203 (cap_value_t *) new_cap_list, CAP_SET);
204 cap_set_flag (new_caps, CAP_EFFECTIVE, nnew_cap_list,
205 (cap_value_t *) new_cap_list, CAP_SET);
207 cap_set_flag (tmp_caps, CAP_PERMITTED, ntmp_cap_list,
208 (cap_value_t *) tmp_cap_list, CAP_SET);
209 cap_set_flag (tmp_caps, CAP_EFFECTIVE, ntmp_cap_list,
210 (cap_value_t *) tmp_cap_list, CAP_SET);
212 int res = cap_set_proc (tmp_caps);
216 if (__builtin_expect (res != 0, 0))
219 dbg_log (_("Failed to drop capabilities"));
220 error (EXIT_FAILURE, 0, _("cap_set_proc failed"));
227 install_real_capabilities (cap_t new_caps)
229 /* If we have no capabilities there is nothing to do here. */
230 if (new_caps == NULL)
233 if (cap_set_proc (new_caps))
236 dbg_log (_("Failed to drop capabilities"));
237 error (EXIT_FAILURE, 0, _("cap_set_proc failed"));
243 if (prctl (PR_SET_KEEPCAPS, 0) == -1)
245 dbg_log (_("Failed to unset keep-capabilities"));
246 error (EXIT_FAILURE, errno, _("prctl(KEEPCAPS) failed"));
250 # endif /* HAVE_LIBCAP */
251 #endif /* HAVE_LIBAUDIT */
253 /* Determine if we are running on an SELinux kernel. Set selinux_enabled
256 nscd_selinux_enabled (int *selinux_enabled)
258 *selinux_enabled = is_selinux_enabled ();
259 if (*selinux_enabled < 0)
261 dbg_log (_("Failed to determine if kernel supports SELinux"));
267 /* Create thread for AVC netlink notification. */
269 avc_create_thread (void (*run) (void))
274 pthread_create (&avc_notify_thread, NULL, (void *(*) (void *)) run, NULL);
276 error (EXIT_FAILURE, rc, _("Failed to start AVC thread"));
278 return &avc_notify_thread;
282 /* Stop AVC netlink thread. */
284 avc_stop_thread (void *thread)
286 pthread_cancel (*(pthread_t *) thread);
290 /* Allocate a new AVC lock. */
292 avc_alloc_lock (void)
294 pthread_mutex_t *avc_mutex;
296 avc_mutex = malloc (sizeof (pthread_mutex_t));
297 if (avc_mutex == NULL)
298 error (EXIT_FAILURE, errno, _("Failed to create AVC lock"));
299 pthread_mutex_init (avc_mutex, NULL);
305 /* Acquire an AVC lock. */
307 avc_get_lock (void *lock)
309 pthread_mutex_lock (lock);
313 /* Release an AVC lock. */
315 avc_release_lock (void *lock)
317 pthread_mutex_unlock (lock);
321 /* Free an AVC lock. */
323 avc_free_lock (void *lock)
325 pthread_mutex_destroy (lock);
330 /* Initialize the user space access vector cache (AVC) for NSCD along with
331 log/thread/lock callbacks. */
335 avc_entry_ref_init (&aeref);
337 if (avc_init ("avc", NULL, &log_cb, &thread_cb, &lock_cb) < 0)
338 error (EXIT_FAILURE, errno, _("Failed to start AVC"));
340 dbg_log (_("Access Vector Cache (AVC) started"));
347 /* Check the permission from the caller (via getpeercon) to nscd.
348 Returns 0 if access is allowed, 1 if denied, and -1 on error. */
350 nscd_request_avc_has_perm (int fd, request_type req)
352 /* Initialize to NULL so we know what to free in case of failure. */
353 security_context_t scon = NULL;
354 security_context_t tcon = NULL;
355 security_id_t ssid = NULL;
356 security_id_t tsid = NULL;
359 if (getpeercon (fd, &scon) < 0)
361 dbg_log (_("Error getting context of socket peer"));
364 if (getcon (&tcon) < 0)
366 dbg_log (_("Error getting context of nscd"));
369 if (avc_context_to_sid (scon, &ssid) < 0
370 || avc_context_to_sid (tcon, &tsid) < 0)
372 dbg_log (_("Error getting sid from context"));
376 #ifndef NSCD__GETSERV
379 dbg_log (_("compile-time support for database policy missing"));
384 rc = avc_has_perm (ssid, tsid, SECCLASS_NSCD, perms[req], &aeref, NULL) < 0;
400 /* Wrapper to get AVC statistics. */
402 nscd_avc_cache_stats (struct avc_cache_stats *cstats)
404 avc_cache_stats (cstats);
408 /* Print the AVC statistics to stdout. */
410 nscd_avc_print_stats (struct avc_cache_stats *cstats)
412 printf (_("\nSELinux AVC Statistics:\n\n"
413 "%15u entry lookups\n"
415 "%15u entry misses\n"
416 "%15u entry discards\n"
420 "%15u CAV misses\n"),
421 cstats->entry_lookups, cstats->entry_hits, cstats->entry_misses,
422 cstats->entry_discards, cstats->cav_lookups, cstats->cav_hits,
423 cstats->cav_probes, cstats->cav_misses);
426 #endif /* HAVE_SELINUX */