privs.h revision 330449
1/*- 2 * privs.h - header for privileged operations 3 * 4 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 5 * 6 * Copyright (C) 1993 Thomas Koenig 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(S) 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 * $FreeBSD: stable/11/usr.bin/at/privs.h 330449 2018-03-05 07:26:05Z eadler $ 29 */ 30 31#ifndef _PRIVS_H 32#define _PRIVS_H 33 34#include <unistd.h> 35 36/* Relinquish privileges temporarily for a setuid or setgid program 37 * with the option of getting them back later. This is done by 38 * utilizing POSIX saved user and group IDs. Call RELINQUISH_PRIVS once 39 * at the beginning of the main program. This will cause all operations 40 * to be executed with the real userid. When you need the privileges 41 * of the setuid/setgid invocation, call PRIV_START; when you no longer 42 * need it, call PRIV_END. Note that it is an error to call PRIV_START 43 * and not PRIV_END within the same function. 44 * 45 * Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running 46 * as root, and you want to drop back the effective userid to a 47 * and the effective group id to b, with the option to get them back 48 * later. 49 * 50 * If you no longer need root privileges, but those of some other 51 * userid/groupid, you can call REDUCE_PRIV(a,b) when your effective 52 * is the user's. 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 65extern uid_t real_uid, effective_uid; 66extern gid_t real_gid, effective_gid; 67 68#ifdef MAIN 69uid_t real_uid, effective_uid; 70gid_t real_gid, effective_gid; 71#endif 72 73#define RELINQUISH_PRIVS { \ 74 real_uid = getuid(); \ 75 effective_uid = geteuid(); \ 76 real_gid = getgid(); \ 77 effective_gid = getegid(); \ 78 if (seteuid(real_uid) != 0) err(1, "seteuid failed"); \ 79 if (setegid(real_gid) != 0) err(1, "setegid failed"); \ 80} 81 82#define RELINQUISH_PRIVS_ROOT(a, b) { \ 83 real_uid = (a); \ 84 effective_uid = geteuid(); \ 85 real_gid = (b); \ 86 effective_gid = getegid(); \ 87 if (setegid(real_gid) != 0) err(1, "setegid failed"); \ 88 if (seteuid(real_uid) != 0) err(1, "seteuid failed"); \ 89} 90 91#define PRIV_START { \ 92 if (seteuid(effective_uid) != 0) err(1, "seteuid failed"); \ 93 if (setegid(effective_gid) != 0) err(1, "setegid failed"); \ 94} 95 96#define PRIV_END { \ 97 if (setegid(real_gid) != 0) err(1, "setegid failed"); \ 98 if (seteuid(real_uid) != 0) err(1, "seteuid failed"); \ 99} 100 101#define REDUCE_PRIV(a, b) { \ 102 PRIV_START \ 103 effective_uid = (a); \ 104 effective_gid = (b); \ 105 if (setregid((gid_t)-1, effective_gid) != 0) err(1, "setregid failed"); \ 106 if (setreuid((uid_t)-1, effective_uid) != 0) err(1, "setreuid failed"); \ 107 PRIV_END \ 108} 109#endif 110