1 /* 2 * privs.h - header for privileged operations 3 * Copyright (c) 1993 by Thomas Koenig 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. The name of the author(s) may not be used to endorse or promote 12 * products derived from this software without specific prior written 13 * permission. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 * 26 * $Id: privs.h,v 1.1 94/07/29 19:58:09 root Exp $ 27 */ 28 29 #ifndef _PRIVS_H 30 #define _PRIVS_H 31 32 #include <unistd.h> 33 34 /* Relinquish privileges temporarily for a setuid program 35 * with the option of getting them back later. This is done by swapping 36 * the real and effective userid BSD style. Call RELINQUISH_PRIVS once 37 * at the beginning of the main program. This will cause all operatons 38 * to be executed with the real userid. When you need the privileges 39 * of the setuid invocation, call PRIV_START; when you no longer 40 * need it, call PRIV_END. Note that it is an error to call PRIV_START 41 * and not PRIV_END within the same function. 42 * 43 * Use RELINQUISH_PRIVS_ROOT(a) if your program started out running 44 * as root, and you want to drop back the effective userid to a 45 * and the effective group id to b, with the option to get them back 46 * later. 47 * 48 * If you no longer need root privileges, but those of some other 49 * userid, you can call REDUCE_PRIV(a) when your effective 50 * is the user's. 51 * 52 * Problems: Do not use return between PRIV_START and PRIV_END; this 53 * will cause the program to continue running in an unprivileged 54 * state. 55 * 56 * It is NOT safe to call exec(), system() or popen() with a user- 57 * supplied program (i.e. without carefully checking PATH and any 58 * library load paths) with relinquished privileges; the called program 59 * can aquire them just as easily. Set both effective and real userid 60 * to the real userid before calling any of them. 61 */ 62 63 #ifndef MAIN 64 extern 65 #endif 66 uid_t real_uid, effective_uid; 67 68 #define RELINQUISH_PRIVS { \ 69 real_uid = getuid(); \ 70 effective_uid = geteuid(); \ 71 seteuid(real_uid); \ 72 } 73 74 #define RELINQUISH_PRIVS_ROOT(a) { \ 75 real_uid = (a); \ 76 effective_uid = geteuid(); \ 77 seteuid(real_uid); \ 78 } 79 80 #define PRIV_START { \ 81 seteuid(effective_uid); 82 83 #define PRIV_END \ 84 seteuid(real_uid); \ 85 } 86 87 #define REDUCE_PRIV(a) { \ 88 seteuid(effective_uid); \ 89 real_uid = effective_uid = (a); \ 90 setuid(real_uid); \ 91 } 92 #endif 93