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: src/usr.bin/at/privs.h,v 1.8 2001/09/04 16:15:51 ru Exp $ 26 * $DragonFly: src/usr.bin/at/privs.h,v 1.4 2007/08/26 16:12:27 pavalos Exp $ 27 */ 28 29 #ifndef _PRIVS_H 30 #define _PRIVS_H 31 32 #include <unistd.h> 33 34 /* Relinquish privileges temporarily for a setuid or setgid program 35 * with the option of getting them back later. This is done by 36 * utilizing POSIX saved user and group IDs. Call RELINQUISH_PRIVS once 37 * at the beginning of the main program. This will cause all operations 38 * to be executed with the real userid. When you need the privileges 39 * of the setuid/setgid 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,b) 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/groupid, you can call REDUCE_PRIV(a,b) 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 acquire them just as easily. Set both effective and real userid 60 * to the real userid before calling any of them. 61 */ 62 63 extern uid_t real_uid, effective_uid; 64 extern gid_t real_gid, effective_gid; 65 66 #define RELINQUISH_PRIVS { \ 67 real_uid = getuid(); \ 68 effective_uid = geteuid(); \ 69 real_gid = getgid(); \ 70 effective_gid = getegid(); \ 71 seteuid(real_uid); \ 72 setegid(real_gid); \ 73 } 74 75 #define RELINQUISH_PRIVS_ROOT(a, b) { \ 76 real_uid = (a); \ 77 effective_uid = geteuid(); \ 78 real_gid = (b); \ 79 effective_gid = getegid(); \ 80 setegid(real_gid); \ 81 seteuid(real_uid); \ 82 } 83 84 #define PRIV_START { \ 85 seteuid(effective_uid); \ 86 setegid(effective_gid); \ 87 } 88 89 #define PRIV_END { \ 90 setegid(real_gid); \ 91 seteuid(real_uid); \ 92 } 93 94 #define REDUCE_PRIV(a, b) { \ 95 PRIV_START \ 96 effective_uid = (a); \ 97 effective_gid = (b); \ 98 setreuid((uid_t)-1, effective_uid); \ 99 setregid((gid_t)-1, effective_gid); \ 100 PRIV_END \ 101 } 102 #endif 103