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 * $FreeBSD$ 26 */ 27 28 #ifndef _PRIVS_H 29 #define _PRIVS_H 30 31 #include <unistd.h> 32 33 /* Relinquish privileges temporarily for a setuid or setgid program 34 * with the option of getting them back later. This is done by 35 * utilizing POSIX saved user and group IDs. Call RELINQUISH_PRIVS once 36 * at the beginning of the main program. This will cause all operations 37 * to be executed with the real userid. When you need the privileges 38 * of the setuid/setgid invocation, call PRIV_START; when you no longer 39 * need it, call PRIV_END. Note that it is an error to call PRIV_START 40 * and not PRIV_END within the same function. 41 * 42 * Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running 43 * as root, and you want to drop back the effective userid to a 44 * and the effective group id to b, with the option to get them back 45 * later. 46 * 47 * If you no longer need root privileges, but those of some other 48 * userid/groupid, you can call REDUCE_PRIV(a,b) when your effective 49 * is the user's. 50 * 51 * Problems: Do not use return between PRIV_START and PRIV_END; this 52 * will cause the program to continue running in an unprivileged 53 * state. 54 * 55 * It is NOT safe to call exec(), system() or popen() with a user- 56 * supplied program (i.e. without carefully checking PATH and any 57 * library load paths) with relinquished privileges; the called program 58 * can acquire them just as easily. Set both effective and real userid 59 * to the real userid before calling any of them. 60 */ 61 62 extern uid_t real_uid, effective_uid; 63 extern gid_t real_gid, effective_gid; 64 65 #define RELINQUISH_PRIVS { \ 66 real_uid = getuid(); \ 67 effective_uid = geteuid(); \ 68 real_gid = getgid(); \ 69 effective_gid = getegid(); \ 70 seteuid(real_uid); \ 71 setegid(real_gid); \ 72 } 73 74 #define RELINQUISH_PRIVS_ROOT(a, b) { \ 75 real_uid = (a); \ 76 effective_uid = geteuid(); \ 77 real_gid = (b); \ 78 effective_gid = getegid(); \ 79 setegid(real_gid); \ 80 seteuid(real_uid); \ 81 } 82 83 #define PRIV_START { \ 84 seteuid(effective_uid); \ 85 setegid(effective_gid); \ 86 } 87 88 #define PRIV_END { \ 89 setegid(real_gid); \ 90 seteuid(real_uid); \ 91 } 92 93 #define REDUCE_PRIV(a, b) { \ 94 PRIV_START \ 95 effective_uid = (a); \ 96 effective_gid = (b); \ 97 setreuid((uid_t)-1, effective_uid); \ 98 setregid((gid_t)-1, effective_gid); \ 99 PRIV_END \ 100 } 101 #endif 102