Line data    Source code

       1             : /* 
       2             :    Unix SMB/CIFS implementation.
       3             : 
       4             :    gain/lose root privileges
       5             : 
       6             :    Copyright (C) Andrew Tridgell 2004
       7             :    
       8             :    This program is free software; you can redistribute it and/or modify
       9             :    it under the terms of the GNU General Public License as published by
      10             :    the Free Software Foundation; either version 3 of the License, or
      11             :    (at your option) any later version.
      12             :    
      13             :    This program is distributed in the hope that it will be useful,
      14             :    but WITHOUT ANY WARRANTY; without even the implied warranty of
      15             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      16             :    GNU General Public License for more details.
      17             :    
      18             :    You should have received a copy of the GNU General Public License
      19             :    along with this program.  If not, see <http://www.gnu.org/licenses/>.
      20             : */
      21             : 
      22             : #include "replace.h"
      23             : #include <talloc.h>
      24             : #include "lib/util/fault.h"
      25             : #include "system/passwd.h"
      26             : 
      27             : #ifdef HAVE_UNISTD_H
      28             : #include <unistd.h>
      29             : #endif
      30             : 
      31             : #include "../lib/util/unix_privs.h"
      32             : #include "../lib/util/setid.h"
      33             : 
      34             : /**
      35             :  * @file
      36             :  * @brief Gaining/losing root privileges
      37             :  */
      38             : 
      39             : /*
      40             :   there are times when smbd needs to temporarily gain root privileges
      41             :   to do some operation. To do this you call root_privileges(), which
      42             :   returns a talloc handle. To restore your previous privileges
      43             :   talloc_free() this pointer.
      44             : 
      45             :   Note that this call is considered successful even if it does not
      46             :   manage to gain root privileges, but it will call smb_abort() if it
      47             :   fails to restore the privileges afterwards. The logic is that
      48             :   failing to gain root access can be caught by whatever operation
      49             :   needs to be run as root failing, but failing to lose the root
      50             :   privileges is dangerous.
      51             : 
      52             :   This also means that this code is safe to be called from completely
      53             :   unprivileged processes.
      54             : */
      55             : 
      56             : struct saved_state {
      57             :         uid_t uid;
      58             : };
      59             : 
      60         585 : static int privileges_destructor(struct saved_state *s)
      61             : {
      62        1170 :         if (geteuid() != s->uid &&
      63         585 :             samba_seteuid(s->uid) != 0) {
      64           0 :                 smb_panic("Failed to restore privileges");
      65             :         }
      66         585 :         return 0;
      67             : }
      68             : 
      69             : /**
      70             :  * Obtain root privileges for the current process.
      71             :  *
      72             :  * The privileges can be dropped by talloc_free()-ing the 
      73             :  * token returned by this function
      74             :  */
      75         585 : void *root_privileges(void)
      76             : {
      77             :         struct saved_state *s;
      78         585 :         s = talloc(NULL, struct saved_state);
      79         585 :         if (!s) return NULL;
      80         585 :         s->uid = geteuid();
      81         585 :         if (s->uid != 0) {
      82         585 :                 samba_seteuid(0);
      83             :         }
      84         585 :         talloc_set_destructor(s, privileges_destructor);
      85         585 :         return s;
      86             : }
      87             : 
      88           0 : uid_t root_privileges_original_uid(void *s)
      89             : {
      90           0 :         struct saved_state *saved = talloc_get_type_abort(s, struct saved_state);
      91           0 :         return saved->uid;
      92             : }