1 /* $NetBSD: privs.c,v 1.3 2018/02/25 23:48:16 htodd Exp $ */
2
3 /*
4 * privs.c - privileged operations
5 * Copyright (C) 1993 Thomas Koenig
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. The name of the author(s) may not be used to endorse or promote
13 * products derived from this software without specific prior written
14 * permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
27 * From: OpenBSD: privs.h,v 1.4 1997/03/01 23:40:12 millert Exp
28 */
29
30 #include <unistd.h>
31
32 #include "privs.h"
33
34 /*
35 * Used by: usr.bin/at
36 * Used by: libexec/atrun
37 */
38
39 /*
40 * Relinquish privileges temporarily for a setuid or setgid program
41 * with the option of getting them back later. This is done by
42 * using POSIX saved user and groups ids. Call RELINQUISH_PRIVS once
43 * at the beginning of the main program. This will cause all operations
44 * to be executed with the real userid. When you need the privileges
45 * of the setuid/setgid invocation, call PRIV_START; when you no longer
46 * need it, call PRIV_END. Note that it is an error to call PRIV_START
47 * and not PRIV_END within the same function.
48 *
49 * Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running
50 * as root, and you want to drop back the effective userid to a
51 * and the effective group id to b, with the option to get them back
52 * later.
53 *
54 * Problems: Do not use return between PRIV_START and PRIV_END; this
55 * will cause the program to continue running in an unprivileged
56 * state.
57 *
58 * It is NOT safe to call exec(), system() or popen() with a user-
59 * supplied program (i.e. without carefully checking PATH and any
60 * library load paths) with relinquished privileges; the called program
61 * can acquire them just as easily. Set both effective and real userid
62 * to the real userid before calling any of them.
63 */
64
65 uid_t real_uid, effective_uid;
66 gid_t real_gid, effective_gid;
67
68 void
privs_enter(void)69 privs_enter(void)
70 {
71 if (seteuid(effective_uid) == -1)
72 privs_fail("Cannot get user privs");
73 if (setegid(effective_gid) == -1)
74 privs_fail("Cannot get group privs");
75 }
76
77 void
privs_exit(void)78 privs_exit(void)
79 {
80 if (setegid(real_gid) == -1)
81 privs_fail("Cannot relinquish group privs");
82 if (seteuid(real_uid) == -1)
83 privs_fail("Cannot relinquish user privs");
84 }
85
86 void
privs_relinquish(void)87 privs_relinquish(void)
88 {
89 real_uid = getuid();
90 effective_uid = geteuid();
91 real_gid = getgid();
92 effective_gid = getegid();
93 privs_exit();
94 }
95
96 void
privs_relinquish_root(uid_t ruid,gid_t rgid)97 privs_relinquish_root(uid_t ruid, gid_t rgid)
98 {
99 real_uid = ruid;
100 real_gid = rgid;
101 effective_uid = geteuid();
102 effective_gid = getegid();
103 privs_exit();
104 }
105