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
62extern uid_t real_uid, effective_uid;
63extern gid_t real_gid, effective_gid;
64
65#ifdef MAIN
66uid_t real_uid, effective_uid;
67gid_t real_gid, effective_gid;
68#endif
69
70#define RELINQUISH_PRIVS { \
71	real_uid = getuid(); \
72	effective_uid = geteuid(); \
73	real_gid = getgid(); \
74	effective_gid = getegid(); \
75	if (seteuid(real_uid) != 0) err(1, "seteuid failed"); \
76	if (setegid(real_gid) != 0) err(1, "setegid failed"); \
77}
78
79#define RELINQUISH_PRIVS_ROOT(a, b) { \
80	real_uid = (a); \
81	effective_uid = geteuid(); \
82	real_gid = (b); \
83	effective_gid = getegid(); \
84	if (setegid(real_gid) != 0) err(1, "setegid failed"); \
85	if (seteuid(real_uid) != 0) err(1, "seteuid failed"); \
86}
87
88#define PRIV_START { \
89	if (seteuid(effective_uid) != 0) err(1, "seteuid failed"); \
90	if (setegid(effective_gid) != 0) err(1, "setegid failed"); \
91}
92
93#define PRIV_END { \
94	if (setegid(real_gid) != 0) err(1, "setegid failed"); \
95	if (seteuid(real_uid) != 0) err(1, "seteuid failed"); \
96}
97
98#define REDUCE_PRIV(a, b) { \
99	PRIV_START \
100	effective_uid = (a); \
101	effective_gid = (b); \
102	if (setregid((gid_t)-1, effective_gid) != 0) err(1, "setregid failed"); \
103	if (setreuid((uid_t)-1, effective_uid) != 0) err(1, "setreuid failed"); \
104	PRIV_END \
105}
106#endif
107