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 "includes.h"
23#include "system/filesys.h"
24#include "../lib/util/unix_privs.h"
25
26/**
27 * @file
28 * @brief Gaining/losing root privileges
29 */
30
31/*
32  there are times when smbd needs to temporarily gain root privileges
33  to do some operation. To do this you call root_privileges(), which
34  returns a talloc handle. To restore your previous privileges
35  talloc_free() this pointer.
36
37  Note that this call is considered successful even if it does not
38  manage to gain root privileges, but it will call smb_abort() if it
39  fails to restore the privileges afterwards. The logic is that
40  failing to gain root access can be caught by whatever operation
41  needs to be run as root failing, but failing to lose the root
42  privileges is dangerous.
43
44  This also means that this code is safe to be called from completely
45  unprivileged processes.
46*/
47
48struct saved_state {
49	uid_t uid;
50};
51
52static int privileges_destructor(struct saved_state *s)
53{
54	if (geteuid() != s->uid &&
55	    seteuid(s->uid) != 0) {
56		smb_panic("Failed to restore privileges");
57	}
58	return 0;
59}
60
61/**
62 * Obtain root privileges for the current process.
63 *
64 * The privileges can be dropped by talloc_free()-ing the
65 * token returned by this function
66 */
67void *root_privileges(void)
68{
69	struct saved_state *s;
70	s = talloc(NULL, struct saved_state);
71	if (!s) return NULL;
72	s->uid = geteuid();
73	if (s->uid != 0) {
74		seteuid(0);
75	}
76	talloc_set_destructor(s, privileges_destructor);
77	return s;
78}
79