glibc/nscd/selinux.c

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/* 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 "config.h"
#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>
#ifdef HAVE_LIBAUDIT
#include <libaudit.h>
#endif
#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;
#ifdef HAVE_LIBAUDIT
/* Prototype for supporting the audit daemon */
static void log_callback (const char *fmt, ...);
#endif
/* 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 =
{
#ifdef HAVE_LIBAUDIT
.func_log = log_callback,
#else
.func_log = dbg_log,
#endif
.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
};
#ifdef HAVE_LIBAUDIT
/* The audit system's netlink socket descriptor */
static int audit_fd = -1;
/* When an avc denial occurs, log it to audit system */
static void
log_callback (const char *fmt, ...)
{
va_list ap;
va_start (ap, fmt);
audit_log_avc (audit_fd, AUDIT_USER_AVC, fmt, ap);
va_end (ap);
}
/* Initialize the connection to the audit system */
static void
audit_init (void)
{
audit_fd = audit_open ();
if (audit_fd < 0)
dbg_log (_("Failed opening connection to the audit subsystem"));
}
#endif /* HAVE_LIBAUDIT */
/* 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"));
#ifdef HAVE_LIBAUDIT
audit_init ();
#endif
}
/* 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 ();
#ifdef HAVE_LIBAUDIT
audit_close (audit_fd);
#endif
}
#endif /* HAVE_SELINUX */