1 /* $NetBSD: privs.h,v 1.3 1995/03/25 18:13:41 glass Exp $ */ 2 3 /* 4 * privs.h - header for privileged operations 5 * Copyright (c) 1993 by Thomas Koenig 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. The name of the author(s) may not be used to endorse or promote 14 * products derived from this software without specific prior written 15 * permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 * 28 */ 29 30 #ifndef _PRIVS_H 31 #define _PRIVS_H 32 33 #include <unistd.h> 34 35 /* Relinquish privileges temporarily for a setuid program 36 * with the option of getting them back later. This is done by swapping 37 * the real and effective userid BSD style. Call RELINQUISH_PRIVS once 38 * at the beginning of the main program. This will cause all operatons 39 * to be executed with the real userid. When you need the privileges 40 * of the setuid invocation, call PRIV_START; when you no longer 41 * need it, call PRIV_END. Note that it is an error to call PRIV_START 42 * and not PRIV_END within the same function. 43 * 44 * Use RELINQUISH_PRIVS_ROOT(a) if your program started out running 45 * as root, and you want to drop back the effective userid to a 46 * and the effective group id to b, with the option to get them back 47 * later. 48 * 49 * If you no longer need root privileges, but those of some other 50 * userid, you can call REDUCE_PRIV(a) when your effective 51 * is the user's. 52 * 53 * Problems: Do not use return between PRIV_START and PRIV_END; this 54 * will cause the program to continue running in an unprivileged 55 * state. 56 * 57 * It is NOT safe to call exec(), system() or popen() with a user- 58 * supplied program (i.e. without carefully checking PATH and any 59 * library load paths) with relinquished privileges; the called program 60 * can aquire them just as easily. Set both effective and real userid 61 * to the real userid before calling any of them. 62 */ 63 64 #ifndef MAIN 65 extern 66 #endif 67 uid_t real_uid, effective_uid; 68 69 #define RELINQUISH_PRIVS { \ 70 real_uid = getuid(); \ 71 effective_uid = geteuid(); \ 72 seteuid(real_uid); \ 73 } 74 75 #define RELINQUISH_PRIVS_ROOT(a) { \ 76 real_uid = (a); \ 77 effective_uid = geteuid(); \ 78 seteuid(real_uid); \ 79 } 80 81 #define PRIV_START { \ 82 seteuid(effective_uid); 83 84 #define PRIV_END \ 85 seteuid(real_uid); \ 86 } 87 88 #define REDUCE_PRIV(a) { \ 89 seteuid(effective_uid); \ 90 real_uid = effective_uid = (a); \ 91 setuid(real_uid); \ 92 } 93 #endif 94