1 /*- 2 * privs.h - header for privileged operations 3 * 4 * SPDX-License-Identifier: BSD-2-Clause 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 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 #ifdef MAIN 67 uid_t real_uid, effective_uid; 68 gid_t real_gid, effective_gid; 69 #endif 70 71 #define RELINQUISH_PRIVS { \ 72 real_uid = getuid(); \ 73 effective_uid = geteuid(); \ 74 real_gid = getgid(); \ 75 effective_gid = getegid(); \ 76 if (seteuid(real_uid) != 0) err(1, "seteuid failed"); \ 77 if (setegid(real_gid) != 0) err(1, "setegid failed"); \ 78 } 79 80 #define RELINQUISH_PRIVS_ROOT(a, b) { \ 81 real_uid = (a); \ 82 effective_uid = geteuid(); \ 83 real_gid = (b); \ 84 effective_gid = getegid(); \ 85 if (setegid(real_gid) != 0) err(1, "setegid failed"); \ 86 if (seteuid(real_uid) != 0) err(1, "seteuid failed"); \ 87 } 88 89 #define PRIV_START { \ 90 if (seteuid(effective_uid) != 0) err(1, "seteuid failed"); \ 91 if (setegid(effective_gid) != 0) err(1, "setegid failed"); \ 92 } 93 94 #define PRIV_END { \ 95 if (setegid(real_gid) != 0) err(1, "setegid failed"); \ 96 if (seteuid(real_uid) != 0) err(1, "seteuid failed"); \ 97 } 98 99 #define REDUCE_PRIV(a, b) { \ 100 PRIV_START \ 101 effective_uid = (a); \ 102 effective_gid = (b); \ 103 if (setregid((gid_t)-1, effective_gid) != 0) err(1, "setregid failed"); \ 104 if (setreuid((uid_t)-1, effective_uid) != 0) err(1, "setreuid failed"); \ 105 PRIV_END \ 106 } 107 #endif 108