1 /* SELinux access controls for nscd.
2 Copyright (C) 2004, 2005, 2006, 2007 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 int 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,
74 /* Store an entry ref to speed AVC decisions. */
75 static struct avc_entry_ref aeref;
77 /* Thread to listen for SELinux status changes via netlink. */
78 static pthread_t avc_notify_thread;
81 /* Prototype for supporting the audit daemon */
82 static void log_callback (const char *fmt, ...);
85 /* Prototypes for AVC callback functions. */
86 static void *avc_create_thread (void (*run) (void));
87 static void avc_stop_thread (void *thread);
88 static void *avc_alloc_lock (void);
89 static void avc_get_lock (void *lock);
90 static void avc_release_lock (void *lock);
91 static void avc_free_lock (void *lock);
93 /* AVC callback structures for use in avc_init. */
94 static const struct avc_log_callback log_cb =
97 .func_log = log_callback,
103 static const struct avc_thread_callback thread_cb =
105 .func_create_thread = avc_create_thread,
106 .func_stop_thread = avc_stop_thread
108 static const struct avc_lock_callback lock_cb =
110 .func_alloc_lock = avc_alloc_lock,
111 .func_get_lock = avc_get_lock,
112 .func_release_lock = avc_release_lock,
113 .func_free_lock = avc_free_lock
117 /* The audit system's netlink socket descriptor */
118 static int audit_fd = -1;
120 /* When an avc denial occurs, log it to audit system */
122 log_callback (const char *fmt, ...)
130 int e = vasprintf (&buf, fmt, ap);
133 buf = alloca (BUFSIZ);
134 vsnprintf (buf, BUFSIZ, fmt, ap);
137 /* FIXME: need to attribute this to real user, using getuid for now */
138 audit_log_user_avc_message (audit_fd, AUDIT_USER_AVC, buf, NULL, NULL,
148 /* Initialize the connection to the audit system */
152 audit_fd = audit_open ();
154 /* If kernel doesn't support audit, bail out */
155 && errno != EINVAL && errno != EPROTONOSUPPORT && errno != EAFNOSUPPORT)
156 dbg_log (_("Failed opening connection to the audit subsystem: %m"));
161 static const cap_value_t new_cap_list[] =
163 # define nnew_cap_list (sizeof (new_cap_list) / sizeof (new_cap_list[0]))
164 static const cap_value_t tmp_cap_list[] =
165 { CAP_AUDIT_WRITE, CAP_SETUID, CAP_SETGID };
166 # define ntmp_cap_list (sizeof (tmp_cap_list) / sizeof (tmp_cap_list[0]))
169 preserve_capabilities (void)
172 /* Not root, then we cannot preserve anything. */
175 if (prctl (PR_SET_KEEPCAPS, 1) == -1)
177 dbg_log (_("Failed to set keep-capabilities"));
178 error (EXIT_FAILURE, errno, _("prctl(KEEPCAPS) failed"));
182 cap_t tmp_caps = cap_init ();
184 if (tmp_caps != NULL)
185 new_caps = cap_init ();
187 if (tmp_caps == NULL || new_caps == NULL)
189 if (tmp_caps != NULL)
192 dbg_log (_("Failed to initialize drop of capabilities"));
193 error (EXIT_FAILURE, 0, _("cap_init failed"));
196 /* There is no reason why these should not work. */
197 cap_set_flag (new_caps, CAP_PERMITTED, nnew_cap_list,
198 (cap_value_t *) new_cap_list, CAP_SET);
199 cap_set_flag (new_caps, CAP_EFFECTIVE, nnew_cap_list,
200 (cap_value_t *) new_cap_list, CAP_SET);
202 cap_set_flag (tmp_caps, CAP_PERMITTED, ntmp_cap_list,
203 (cap_value_t *) tmp_cap_list, CAP_SET);
204 cap_set_flag (tmp_caps, CAP_EFFECTIVE, ntmp_cap_list,
205 (cap_value_t *) tmp_cap_list, CAP_SET);
207 int res = cap_set_proc (tmp_caps);
211 if (__builtin_expect (res != 0, 0))
214 dbg_log (_("Failed to drop capabilities"));
215 error (EXIT_FAILURE, 0, _("cap_set_proc failed"));
222 install_real_capabilities (cap_t new_caps)
224 /* If we have no capabilities there is nothing to do here. */
225 if (new_caps == NULL)
228 if (cap_set_proc (new_caps))
231 dbg_log (_("Failed to drop capabilities"));
232 error (EXIT_FAILURE, 0, _("cap_set_proc failed"));
238 if (prctl (PR_SET_KEEPCAPS, 0) == -1)
240 dbg_log (_("Failed to unset keep-capabilities"));
241 error (EXIT_FAILURE, errno, _("prctl(KEEPCAPS) failed"));
245 # endif /* HAVE_LIBCAP */
246 #endif /* HAVE_LIBAUDIT */
248 /* Determine if we are running on an SELinux kernel. Set selinux_enabled
251 nscd_selinux_enabled (int *selinux_enabled)
253 *selinux_enabled = is_selinux_enabled ();
254 if (*selinux_enabled < 0)
256 dbg_log (_("Failed to determine if kernel supports SELinux"));
262 /* Create thread for AVC netlink notification. */
264 avc_create_thread (void (*run) (void))
269 pthread_create (&avc_notify_thread, NULL, (void *(*) (void *)) run, NULL);
271 error (EXIT_FAILURE, rc, _("Failed to start AVC thread"));
273 return &avc_notify_thread;
277 /* Stop AVC netlink thread. */
279 avc_stop_thread (void *thread)
281 pthread_cancel (*(pthread_t *) thread);
285 /* Allocate a new AVC lock. */
287 avc_alloc_lock (void)
289 pthread_mutex_t *avc_mutex;
291 avc_mutex = malloc (sizeof (pthread_mutex_t));
292 if (avc_mutex == NULL)
293 error (EXIT_FAILURE, errno, _("Failed to create AVC lock"));
294 pthread_mutex_init (avc_mutex, NULL);
300 /* Acquire an AVC lock. */
302 avc_get_lock (void *lock)
304 pthread_mutex_lock (lock);
308 /* Release an AVC lock. */
310 avc_release_lock (void *lock)
312 pthread_mutex_unlock (lock);
316 /* Free an AVC lock. */
318 avc_free_lock (void *lock)
320 pthread_mutex_destroy (lock);
325 /* Initialize the user space access vector cache (AVC) for NSCD along with
326 log/thread/lock callbacks. */
330 avc_entry_ref_init (&aeref);
332 if (avc_init ("avc", NULL, &log_cb, &thread_cb, &lock_cb) < 0)
333 error (EXIT_FAILURE, errno, _("Failed to start AVC"));
335 dbg_log (_("Access Vector Cache (AVC) started"));
342 /* Check the permission from the caller (via getpeercon) to nscd.
343 Returns 0 if access is allowed, 1 if denied, and -1 on error. */
345 nscd_request_avc_has_perm (int fd, request_type req)
347 /* Initialize to NULL so we know what to free in case of failure. */
348 security_context_t scon = NULL;
349 security_context_t tcon = NULL;
350 security_id_t ssid = NULL;
351 security_id_t tsid = NULL;
354 if (getpeercon (fd, &scon) < 0)
356 dbg_log (_("Error getting context of socket peer"));
359 if (getcon (&tcon) < 0)
361 dbg_log (_("Error getting context of nscd"));
364 if (avc_context_to_sid (scon, &ssid) < 0
365 || avc_context_to_sid (tcon, &tsid) < 0)
367 dbg_log (_("Error getting sid from context"));
371 rc = avc_has_perm (ssid, tsid, SECCLASS_NSCD, perms[req], &aeref, NULL) < 0;
387 /* Wrapper to get AVC statistics. */
389 nscd_avc_cache_stats (struct avc_cache_stats *cstats)
391 avc_cache_stats (cstats);
395 /* Print the AVC statistics to stdout. */
397 nscd_avc_print_stats (struct avc_cache_stats *cstats)
399 printf (_("\nSELinux AVC Statistics:\n\n"
400 "%15u entry lookups\n"
402 "%15u entry misses\n"
403 "%15u entry discards\n"
407 "%15u CAV misses\n"),
408 cstats->entry_lookups, cstats->entry_hits, cstats->entry_misses,
409 cstats->entry_discards, cstats->cav_lookups, cstats->cav_hits,
410 cstats->cav_probes, cstats->cav_misses);
414 /* Clean up the AVC before exiting. */
416 nscd_avc_destroy (void)
420 audit_close (audit_fd);
424 #endif /* HAVE_SELINUX */