privs.h revision 10154 
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
26#ifndef _PRIVS_H
27#define _PRIVS_H
28
29#ifndef _USE_BSD
30#define _USE_BSD 1
31#include <unistd.h>
32#undef _USE_BSD
33#else
34#include <unistd.h>
35#endif
36
37/* Relinquish privileges temporarily for a setuid or setgid program
38 * with the option of getting them back later.  This is done by swapping
39 * the real and effective userid BSD style.  Call RELINQUISH_PRIVS once
40 * at the beginning of the main program.  This will cause all operatons
41 * to be executed with the real userid.  When you need the privileges
42 * of the setuid/setgid invocation, call PRIV_START; when you no longer
43 * need it, call PRIV_END.  Note that it is an error to call PRIV_START
44 * and not PRIV_END within the same function.
45 *
46 * Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running
47 * as root, and you want to drop back the effective userid to a
48 * and the effective group id to b, with the option to get them back
49 * later.
50 *
51 * If you no longer need root privileges, but those of some other
52 * userid/groupid, you can call REDUCE_PRIV(a,b) when your effective
53 * is the user's.
54 *
55 * Problems: Do not use return between PRIV_START and PRIV_END; this
56 * will cause the program to continue running in an unprivileged
57 * state.
58 *
59 * It is NOT safe to call exec(), system() or popen() with a user-
60 * supplied program (i.e. without carefully checking PATH and any
61 * library load paths) with relinquished privileges; the called program
62 * can aquire them just as easily.  Set both effective and real userid
63 * to the real userid before calling any of them.
64 */
65
66#ifndef MAIN
67extern
68#endif
69uid_t real_uid, effective_uid;
70
71#ifndef MAIN
72extern
73#endif
74gid_t real_gid, effective_gid;
75
76#define RELINQUISH_PRIVS { \
77			      real_uid = getuid(); \
78			      effective_uid = geteuid(); \
79			      real_gid = getgid(); \
80			      effective_gid = getegid(); \
81			      setreuid(effective_uid, real_uid); \
82			      setregid(effective_gid, real_gid); \
83		          }
84
85#define RELINQUISH_PRIVS_ROOT(a,b) { \
86			      real_uid = (a); \
87			      effective_uid = geteuid(); \
88			      real_gid = (b); \
89			      effective_gid = getegid(); \
90			      setregid(effective_gid, real_gid); \
91			      setreuid(effective_uid, real_uid); \
92		          }
93
94#define PRIV_START {\
95		    setreuid(real_uid, effective_uid); \
96		    setregid(real_gid, effective_gid);
97
98#define PRIV_END \
99		    setregid(effective_gid, real_gid); \
100		    setreuid(effective_uid, real_uid); \
101		    }
102
103#define REDUCE_PRIV(a,b) {\
104			setreuid(real_uid, effective_uid); \
105			setregid(real_gid, effective_gid); \
106			effective_uid = (a); \
107			effective_gid = (b); \
108			setregid(effective_gid, real_gid); \
109			setreuid(effective_uid, real_uid); \
110		    }
111#endif
112