/* 

   Unix SMB/CIFS implementation.

   gain/lose root privileges

   Copyright (C) Andrew Tridgell 2004

   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 3 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, see <http://www.gnu.org/licenses/>.

*/

#include "replace.h"

#include <talloc.h>

#include "lib/util/fault.h"

#include "system/passwd.h"

#ifdef HAVE_UNISTD_H

#include <unistd.h>

#endif

#include "../lib/util/unix_privs.h"

#include "../lib/util/setid.h"

/**

 * @file

 * @brief Gaining/losing root privileges

 */

/*

  there are times when smbd needs to temporarily gain root privileges

  to do some operation. To do this you call root_privileges(), which

  returns a talloc handle. To restore your previous privileges

  talloc_free() this pointer.

  Note that this call is considered successful even if it does not

  manage to gain root privileges, but it will call smb_abort() if it

  fails to restore the privileges afterwards. The logic is that

  failing to gain root access can be caught by whatever operation

  needs to be run as root failing, but failing to lose the root

  privileges is dangerous.

  This also means that this code is safe to be called from completely

  unprivileged processes.

*/

struct saved_state {

  uid_t uid;

};

static int privileges_destructor(struct saved_state *s)

{

  if (geteuid() != s->uid &&

      samba_seteuid(s->uid) != 0) {

    smb_panic("Failed to restore privileges");

  }

  return 0;

}

/**

 * Obtain root privileges for the current process.

 *

 * The privileges can be dropped by talloc_free()-ing the 

 * token returned by this function

 */

void *root_privileges(void)

{

  struct saved_state *s;

  s = talloc(NULL, struct saved_state);

  if (!s) return NULL;

  s->uid = geteuid();

  if (s->uid != 0) {

    samba_seteuid(0);

  }

  talloc_set_destructor(s, privileges_destructor);

  return s;

}

uid_t root_privileges_original_uid(void *s)

{

  struct saved_state *saved = talloc_get_type_abort(s, struct saved_state);

  return saved->uid;

}