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/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
* audit.c - libaudit integration for SELinux and AppArmor
*
* Based on apparmor.c, selinux.c
*
* Copyright © 2014-2015 Canonical, Ltd.
* Copyright © 2015 Collabora Ltd.
*
* 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
*
*/
#include <config.h>
#include "audit.h"
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#ifdef HAVE_LIBAUDIT
#include <cap-ng.h>
#include <libaudit.h>
#endif
#include <dbus/dbus-internals.h>
#ifdef DBUS_UNIX
#include <dbus/dbus-userdb.h>
#endif
#ifdef HAVE_LIBAUDIT
static int audit_fd = -1;
#endif
/**
* Open the libaudit fd if appropriate.
*/
void
bus_audit_init (BusContext *context)
{
#ifdef HAVE_LIBAUDIT
int i;
capng_get_caps_process ();
/* Work around a bug in libcap-ng < 0.7.7: it leaks a fd, which isn't
* close-on-exec. Assume it will be one of the first few fds. */
for (i = 3; i < 42; i++)
_dbus_fd_set_close_on_exec (i);
if (!capng_have_capability (CAPNG_EFFECTIVE, CAP_AUDIT_WRITE))
return;
audit_fd = audit_open ();
if (audit_fd < 0)
{
int e = errno;
/* If kernel doesn't support audit, bail out */
if (e == EINVAL || e == EPROTONOSUPPORT || e == EAFNOSUPPORT)
return;
bus_context_log (context, DBUS_SYSTEM_LOG_WARNING,
"Failed to open connection to the audit subsystem: %s",
_dbus_strerror (e));
}
#endif /* HAVE_LIBAUDIT */
}
/**
* If libaudit is in use and it would be appropriate to write audit records,
* return the libaudit fd. Otherwise return -1.
*/
int
bus_audit_get_fd (void)
{
#ifdef HAVE_LIBAUDIT
if (audit_fd >= 0)
{
return audit_fd;
}
#endif
return -1;
}
/**
* Close the libaudit fd.
*/
void
bus_audit_shutdown (void)
{
#ifdef HAVE_LIBAUDIT
audit_close (audit_fd);
#endif /* HAVE_LIBAUDIT */
}
/* The !HAVE_LIBAUDIT case lives in dbus-sysdeps-util-unix.c */
#ifdef HAVE_LIBAUDIT
/**
* Changes the user and group the bus is running as.
*
* @param user the user to become
* @param error return location for errors
* @returns #FALSE on failure
*/
dbus_bool_t
_dbus_change_to_daemon_user (const char *user,
DBusError *error)
{
dbus_uid_t uid;
dbus_gid_t gid;
DBusString u;
_dbus_string_init_const (&u, user);
if (!_dbus_get_user_id_and_primary_group (&u, &uid, &gid))
{
dbus_set_error (error, DBUS_ERROR_FAILED,
"User '%s' does not appear to exist?",
user);
return FALSE;
}
/* If we were root */
if (_dbus_geteuid () == 0)
{
int rc;
int have_audit_write;
have_audit_write = capng_have_capability (CAPNG_PERMITTED, CAP_AUDIT_WRITE);
capng_clear (CAPNG_SELECT_BOTH);
/* Only attempt to retain CAP_AUDIT_WRITE if we had it when
* starting. See:
* https://bugs.freedesktop.org/show_bug.cgi?id=49062#c9
*/
if (have_audit_write)
capng_update (CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED,
CAP_AUDIT_WRITE);
rc = capng_change_id (uid, gid, CAPNG_DROP_SUPP_GRP);
if (rc)
{
switch (rc) {
default:
dbus_set_error (error, DBUS_ERROR_FAILED,
"Failed to drop capabilities: %s\n",
_dbus_strerror (errno));
break;
case -4:
dbus_set_error (error, _dbus_error_from_errno (errno),
"Failed to set GID to %lu: %s", gid,
_dbus_strerror (errno));
break;
case -5:
dbus_set_error (error, _dbus_error_from_errno (errno),
"Failed to drop supplementary groups: %s",
_dbus_strerror (errno));
break;
case -6:
dbus_set_error (error, _dbus_error_from_errno (errno),
"Failed to set UID to %lu: %s", uid,
_dbus_strerror (errno));
break;
case -7:
dbus_set_error (error, _dbus_error_from_errno (errno),
"Failed to unset keep-capabilities: %s\n",
_dbus_strerror (errno));
break;
}
return FALSE;
}
}
return TRUE;
}
#endif
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