1/*
2 *  privs.h - header for privileged operations
3 *  Copyright (C) 1993  Thomas Koenig
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. The name of the author(s) may not be used to endorse or promote
11 *    products derived from this software without specific prior written
12 *    permission.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 *
25 * $FreeBSD$
26 */
27
28#ifndef _PRIVS_H
29#define _PRIVS_H
30
31#include <unistd.h>
32
33/* Relinquish privileges temporarily for a setuid or setgid program
34 * with the option of getting them back later.  This is done by
35 * utilizing POSIX saved user and group IDs.  Call RELINQUISH_PRIVS once
36 * at the beginning of the main program.  This will cause all operations
37 * to be executed with the real userid.  When you need the privileges
38 * of the setuid/setgid invocation, call PRIV_START; when you no longer
39 * need it, call PRIV_END.  Note that it is an error to call PRIV_START
40 * and not PRIV_END within the same function.
41 *
42 * Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running
43 * as root, and you want to drop back the effective userid to a
44 * and the effective group id to b, with the option to get them back
45 * later.
46 *
47 * If you no longer need root privileges, but those of some other
48 * userid/groupid, you can call REDUCE_PRIV(a,b) when your effective
49 * is the user's.
50 *
51 * Problems: Do not use return between PRIV_START and PRIV_END; this
52 * will cause the program to continue running in an unprivileged
53 * state.
54 *
55 * It is NOT safe to call exec(), system() or popen() with a user-
56 * supplied program (i.e. without carefully checking PATH and any
57 * library load paths) with relinquished privileges; the called program
58 * can acquire them just as easily.  Set both effective and real userid
59 * to the real userid before calling any of them.
60 */
61
62#ifndef MAIN
63extern
64#endif
65uid_t real_uid, effective_uid;
66
67#ifndef MAIN
68extern
69#endif
70gid_t real_gid, effective_gid;
71
72#define RELINQUISH_PRIVS { \
73	real_uid = getuid(); \
74	effective_uid = geteuid(); \
75	real_gid = getgid(); \
76	effective_gid = getegid(); \
77	seteuid(real_uid); \
78	setegid(real_gid); \
79}
80
81#define RELINQUISH_PRIVS_ROOT(a, b) { \
82	real_uid = (a); \
83	effective_uid = geteuid(); \
84	real_gid = (b); \
85	effective_gid = getegid(); \
86	setegid(real_gid); \
87	seteuid(real_uid); \
88}
89
90#define PRIV_START { \
91	seteuid(effective_uid); \
92	setegid(effective_gid); \
93}
94
95#define PRIV_END { \
96	setegid(real_gid); \
97	seteuid(real_uid); \
98}
99
100#define REDUCE_PRIV(a, b) { \
101	PRIV_START \
102	effective_uid = (a); \
103	effective_gid = (b); \
104	setreuid((uid_t)-1, effective_uid); \
105	setregid((gid_t)-1, effective_gid); \
106	PRIV_END \
107}
108#endif
109