/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-

 * Portion Copyright © 2008 Nokia Corporation and/or its subsidiary(-ies). All rights reserved.

 * selinux.c  SELinux security checks for D-Bus

 *

 * Author: Matthew Rickard <mjricka@epoch.ncsc.mil>

 *

 * Licensed under the Academic Free License version 2.1

 * 

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program 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 General Public License for more details.

 * 

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

 *

 */

#ifndef __SYMBIAN32__

#include <dbus/dbus-internals.h>

#include <dbus/dbus-string.h>

#else

#include "dbus-internals.h"

#include "dbus-string.h"

#endif //__SYMBIAN32__

#include "selinux.h"

#include "services.h"

#include "policy.h"

#include "utils.h"

#include "config-parser.h"

#ifdef HAVE_SELINUX

#include <errno.h>

#include <pthread.h>

#include <syslog.h>

#include <selinux/selinux.h>

#include <selinux/avc.h>

#include <selinux/av_permissions.h>

#include <selinux/flask.h>

#include <signal.h>

#include <stdarg.h>

#endif /* HAVE_SELINUX */

#define BUS_SID_FROM_SELINUX(sid)  ((BusSELinuxID*) (sid))

#define SELINUX_SID_FROM_BUS(sid)  ((security_id_t) (sid))

#ifdef HAVE_SELINUX

/* Store the value telling us if SELinux is enabled in the kernel. */

static dbus_bool_t selinux_enabled = FALSE;

/* Store an avc_entry_ref to speed AVC decisions. */

static struct avc_entry_ref aeref;

/* Store the SID of the bus itself to use as the default. */

static security_id_t bus_sid = SECSID_WILD;

/* Thread to listen for SELinux status changes via netlink. */

static pthread_t avc_notify_thread;

/* Prototypes for AVC callback functions.  */

static void log_callback (const char *fmt, ...);

static void log_audit_callback (void *data, security_class_t class, char *buf, size_t bufleft);

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_memory_callback mem_cb =

{

  .func_malloc = dbus_malloc,

  .func_free = dbus_free

};

static const struct avc_log_callback log_cb =

{

  .func_log = log_callback,

  .func_audit = log_audit_callback

};

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

};

#endif /* HAVE_SELINUX */

/**

 * Log callback to log denial messages from the AVC.

 * This is used in avc_init.  Logs to both standard

 * error and syslogd.

 *

 * @param fmt the format string

 * @param variable argument list

 */

#ifdef HAVE_SELINUX

static void 

log_callback (const char *fmt, ...) 

{

  va_list ap;

  va_start(ap, fmt);

  vsyslog (LOG_INFO, fmt, ap);

  va_end(ap);

}

/**

 * On a policy reload we need to reparse the SELinux configuration file, since

 * this could have changed.  Send a SIGHUP to reload all configs.

 */

static int

policy_reload_callback (u_int32_t event, security_id_t ssid, 

                        security_id_t tsid, security_class_t tclass, 

                        access_vector_t perms, access_vector_t *out_retained)

{

  if (event == AVC_CALLBACK_RESET)

    return raise (SIGHUP);

  return 0;

}

/**

 * Log any auxiliary data 

 */

static void

log_audit_callback (void *data, security_class_t class, char *buf, size_t bufleft)

{

  DBusString *audmsg = data;

  _dbus_string_copy_to_buffer (audmsg, buf, bufleft);

}

/**

 * Create thread to notify the AVC of enforcing and policy reload

 * changes via netlink.

 *

 * @param run the thread run function

 * @return pointer to the thread

 */

static void *

avc_create_thread (void (*run) (void))

{

  int rc;

  rc = pthread_create (&avc_notify_thread, NULL, (void *(*) (void *)) run, NULL);

  if (rc != 0)

    {

      _dbus_warn ("Failed to start AVC thread: %s\n", _dbus_strerror (rc));

      exit (1);

    }

  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 = dbus_new (pthread_mutex_t, 1);

  if (avc_mutex == NULL)

    {

      _dbus_warn ("Could not create mutex: %s\n", _dbus_strerror (errno));

      exit (1);

    }

  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);

  dbus_free (lock);

}

#endif /* HAVE_SELINUX */

/**

 * Return whether or not SELinux is enabled; must be

 * called after bus_selinux_init.

 */

dbus_bool_t

bus_selinux_enabled (void)

{

#ifdef HAVE_SELINUX

  return selinux_enabled;

#else

  return FALSE;

#endif /* HAVE_SELINUX */

}

/**

 * Do early initialization; determine whether SELinux is enabled.

 */

dbus_bool_t

bus_selinux_pre_init (void)

{

#ifdef HAVE_SELINUX

  int r;

  _dbus_assert (bus_sid == SECSID_WILD);

  /* Determine if we are running an SELinux kernel. */

  r = is_selinux_enabled ();

  if (r < 0)

    {

      _dbus_warn ("Could not tell if SELinux is enabled: %s\n",

                  _dbus_strerror (errno));

      return FALSE;

    }

  selinux_enabled = r != 0;

  return TRUE;

#else

  return TRUE;

#endif

}

/**

 * Initialize the user space access vector cache (AVC) for D-Bus and set up

 * logging callbacks.

 */

dbus_bool_t

bus_selinux_full_init (void)

{

#ifdef HAVE_SELINUX

  char *bus_context;

  _dbus_assert (bus_sid == SECSID_WILD);

  if (!selinux_enabled)

    {

      _dbus_verbose ("SELinux not enabled in this kernel.\n");

      return TRUE;

    }

  _dbus_verbose ("SELinux is enabled in this kernel.\n");

  avc_entry_ref_init (&aeref);

  if (avc_init ("avc", &mem_cb, &log_cb, &thread_cb, &lock_cb) < 0)

    {

      _dbus_warn ("Failed to start Access Vector Cache (AVC).\n");

      return FALSE;

    }

  else

    {

      openlog ("dbus", LOG_PERROR, LOG_USER);

      _dbus_verbose ("Access Vector Cache (AVC) started.\n");

    }

  if (avc_add_callback (policy_reload_callback, AVC_CALLBACK_RESET,

                       NULL, NULL, 0, 0) < 0)

    {

      _dbus_warn ("Failed to add policy reload callback: %s\n",

                  _dbus_strerror (errno));

      avc_destroy ();

      return FALSE;

    }

  bus_context = NULL;

  bus_sid = SECSID_WILD;

  if (getcon (&bus_context) < 0)

    {

      _dbus_verbose ("Error getting context of bus: %s\n",

                     _dbus_strerror (errno));

      return FALSE;

    }

  if (avc_context_to_sid (bus_context, &bus_sid) < 0)

    {

      _dbus_verbose ("Error getting SID from bus context: %s\n",

                     _dbus_strerror (errno));

      freecon (bus_context);

      return FALSE;

    }

  freecon (bus_context);

  return TRUE;

#else

  return TRUE;

#endif /* HAVE_SELINUX */

}

/**

 * Decrement SID reference count.

 * 

 * @param sid the SID to decrement

 */

void

bus_selinux_id_unref (BusSELinuxID *sid)

{

#ifdef HAVE_SELINUX

  if (!selinux_enabled)

    return;

  _dbus_assert (sid != NULL);

  sidput (SELINUX_SID_FROM_BUS (sid));

#endif /* HAVE_SELINUX */

}

void

bus_selinux_id_ref (BusSELinuxID *sid)

{

#ifdef HAVE_SELINUX

  if (!selinux_enabled)

    return;

  _dbus_assert (sid != NULL);

  sidget (SELINUX_SID_FROM_BUS (sid));

#endif /* HAVE_SELINUX */

}

/**

 * Determine if the SELinux security policy allows the given sender

 * security context to go to the given recipient security context.

 * This function determines if the requested permissions are to be

 * granted from the connection to the message bus or to another

 * optionally supplied security identifier (e.g. for a service

 * context).  Currently these permissions are either send_msg or

 * acquire_svc in the dbus class.

 *

 * @param sender_sid source security context

 * @param override_sid is the target security context.  If SECSID_WILD this will

 *        use the context of the bus itself (e.g. the default).

 * @param target_class is the target security class.

 * @param requested is the requested permissions.

 * @returns #TRUE if security policy allows the send.

 */

#ifdef HAVE_SELINUX

static dbus_bool_t

bus_selinux_check (BusSELinuxID        *sender_sid,

                   BusSELinuxID        *override_sid,

                   security_class_t     target_class,

                   access_vector_t      requested,

		   DBusString          *auxdata)

{

  if (!selinux_enabled)

    return TRUE;

  /* Make the security check.  AVC checks enforcing mode here as well. */

  if (avc_has_perm (SELINUX_SID_FROM_BUS (sender_sid),

                    override_sid ?

                    SELINUX_SID_FROM_BUS (override_sid) :

                    SELINUX_SID_FROM_BUS (bus_sid), 

                    target_class, requested, &aeref, auxdata) < 0)

    {

      _dbus_verbose ("SELinux denying due to security policy.\n");

      return FALSE;

    }

  else

    return TRUE;

}

#endif /* HAVE_SELINUX */

/**

 * Returns true if the given connection can acquire a service,

 * assuming the given security ID is needed for that service.

 *

 * @param connection connection that wants to own the service

 * @param service_sid the SID of the service from the table

 * @returns #TRUE if acquire is permitted.

 */

dbus_bool_t

bus_selinux_allows_acquire_service (DBusConnection     *connection,

                                    BusSELinuxID       *service_sid,

				    const char         *service_name,

				    DBusError          *error)

{

#ifdef HAVE_SELINUX

  BusSELinuxID *connection_sid;

  unsigned long spid;

  DBusString auxdata;

  dbus_bool_t ret;

  if (!selinux_enabled)

    return TRUE;

  connection_sid = bus_connection_get_selinux_id (connection);

  if (!dbus_connection_get_unix_process_id (connection, &spid))

    spid = 0;

  if (!_dbus_string_init (&auxdata))

    goto oom;

  if (!_dbus_string_append (&auxdata, "service="))

    goto oom;

  if (!_dbus_string_append (&auxdata, service_name))

    goto oom;

  if (spid)

    {

      if (!_dbus_string_append (&auxdata, " spid="))

	goto oom;

      if (!_dbus_string_append_uint (&auxdata, spid))

	goto oom;

    }

  ret = bus_selinux_check (connection_sid,

			   service_sid,

			   SECCLASS_DBUS,

			   DBUS__ACQUIRE_SVC,

			   &auxdata);

  _dbus_string_free (&auxdata);

  return ret;

 oom:

  _dbus_string_free (&auxdata);

  BUS_SET_OOM (error);

  return FALSE;

#else

  return TRUE;

#endif /* HAVE_SELINUX */

}

/**

 * Check if SELinux security controls allow the message to be sent to a

 * particular connection based on the security context of the sender and

 * that of the receiver. The destination connection need not be the

 * addressed recipient, it could be an "eavesdropper"

 *

 * @param sender the sender of the message.

 * @param proposed_recipient the connection the message is to be sent to.

 * @returns whether to allow the send

 */

dbus_bool_t

bus_selinux_allows_send (DBusConnection     *sender,

                         DBusConnection     *proposed_recipient,

			 const char         *msgtype,

			 const char         *interface,

			 const char         *member,

			 const char         *error_name,

			 const char         *destination,

			 DBusError          *error)

{

#ifdef HAVE_SELINUX

  BusSELinuxID *recipient_sid;

  BusSELinuxID *sender_sid;

  unsigned long spid, tpid;

  DBusString auxdata;

  dbus_bool_t ret;

  dbus_bool_t string_alloced;

  if (!selinux_enabled)

    return TRUE;

  if (!sender || !dbus_connection_get_unix_process_id (sender, &spid))

    spid = 0;

  if (!proposed_recipient || !dbus_connection_get_unix_process_id (proposed_recipient, &tpid))

    tpid = 0;

  string_alloced = FALSE;

  if (!_dbus_string_init (&auxdata))

    goto oom;

  string_alloced = TRUE;

  if (!_dbus_string_append (&auxdata, "msgtype="))

    goto oom;

  if (!_dbus_string_append (&auxdata, msgtype))

    goto oom;

  if (interface)

    {

      if (!_dbus_string_append (&auxdata, " interface="))

	goto oom;

      if (!_dbus_string_append (&auxdata, interface))

	goto oom;

    }

  if (member)

    {

      if (!_dbus_string_append (&auxdata, " member="))

	goto oom;

      if (!_dbus_string_append (&auxdata, member))

	goto oom;

    }

  if (error_name)

    {

      if (!_dbus_string_append (&auxdata, " error_name="))

	goto oom;

      if (!_dbus_string_append (&auxdata, error_name))

	goto oom;

    }

  if (destination)

    {