privs.h revision 54158 
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: head/usr.bin/at/privs.h 54158 1999-12-05 19:57:14Z charnier $
26 */
27
28#ifndef _PRIVS_H
29#define _PRIVS_H
30
31#ifndef _USE_BSD
32#define _USE_BSD 1
33#include <unistd.h>
34#undef _USE_BSD
35#else
36#include <unistd.h>
37#endif
38
39/* Relinquish privileges temporarily for a setuid or setgid program
40 * with the option of getting them back later.  This is done by swapping
41 * the real and effective userid BSD style.  Call RELINQUISH_PRIVS once
42 * at the beginning of the main program.  This will cause all operations
43 * to be executed with the real userid.  When you need the privileges
44 * of the setuid/setgid invocation, call PRIV_START; when you no longer
45 * need it, call PRIV_END.  Note that it is an error to call PRIV_START
46 * and not PRIV_END within the same function.
47 *
48 * Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running
49 * as root, and you want to drop back the effective userid to a
50 * and the effective group id to b, with the option to get them back
51 * later.
52 *
53 * If you no longer need root privileges, but those of some other
54 * userid/groupid, you can call REDUCE_PRIV(a,b) when your effective
55 * is the user's.
56 *
57 * Problems: Do not use return between PRIV_START and PRIV_END; this
58 * will cause the program to continue running in an unprivileged
59 * state.
60 *
61 * It is NOT safe to call exec(), system() or popen() with a user-
62 * supplied program (i.e. without carefully checking PATH and any
63 * library load paths) with relinquished privileges; the called program
64 * can acquire them just as easily.  Set both effective and real userid
65 * to the real userid before calling any of them.
66 */
67
68#ifndef MAIN
69extern
70#endif
71uid_t real_uid, effective_uid;
72
73#ifndef MAIN
74extern
75#endif
76gid_t real_gid, effective_gid;
77
78#define RELINQUISH_PRIVS { \
79			      real_uid = getuid(); \
80			      effective_uid = geteuid(); \
81			      real_gid = getgid(); \
82			      effective_gid = getegid(); \
83			      setreuid(effective_uid, real_uid); \
84			      setregid(effective_gid, real_gid); \
85		          }
86
87#define RELINQUISH_PRIVS_ROOT(a,b) { \
88			      real_uid = (a); \
89			      effective_uid = geteuid(); \
90			      real_gid = (b); \
91			      effective_gid = getegid(); \
92			      setregid(effective_gid, real_gid); \
93			      setreuid(effective_uid, real_uid); \
94		          }
95
96#define PRIV_START {\
97		    setreuid(real_uid, effective_uid); \
98		    setregid(real_gid, effective_gid);
99
100#define PRIV_END \
101		    setregid(effective_gid, real_gid); \
102		    setreuid(effective_uid, real_uid); \
103		    }
104
105#define REDUCE_PRIV(a,b) {\
106			setreuid(real_uid, effective_uid); \
107			setregid(real_gid, effective_gid); \
108			effective_uid = (a); \
109			effective_gid = (b); \
110			setregid(effective_gid, real_gid); \
111			setreuid(effective_uid, real_uid); \
112		    }
113#endif
114