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 #ifndef _USE_BSD 32 #define _USE_BSD 1 33 #include <unistd.h> 34 #undef _USE_BSD 35 #else 36 #include <unistd.h> 37 #endif 38 39 /* Relinquish privileges temporarily for a setuid or setgid program 40 * with the option of getting them back later. This is done by swapping 41 * the real and effective userid BSD style. Call RELINQUISH_PRIVS once 42 * at the beginning of the main program. This will cause all operations 43 * to be executed with the real userid. When you need the privileges 44 * of the setuid/setgid invocation, call PRIV_START; when you no longer 45 * need it, call PRIV_END. Note that it is an error to call PRIV_START 46 * and not PRIV_END within the same function. 47 * 48 * Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running 49 * as root, and you want to drop back the effective userid to a 50 * and the effective group id to b, with the option to get them back 51 * later. 52 * 53 * If you no longer need root privileges, but those of some other 54 * userid/groupid, you can call REDUCE_PRIV(a,b) when your effective 55 * is the user's. 56 * 57 * Problems: Do not use return between PRIV_START and PRIV_END; this 58 * will cause the program to continue running in an unprivileged 59 * state. 60 * 61 * It is NOT safe to call exec(), system() or popen() with a user- 62 * supplied program (i.e. without carefully checking PATH and any 63 * library load paths) with relinquished privileges; the called program 64 * can acquire them just as easily. Set both effective and real userid 65 * to the real userid before calling any of them. 66 */ 67 68 #ifndef MAIN 69 extern 70 #endif 71 uid_t real_uid, effective_uid; 72 73 #ifndef MAIN 74 extern 75 #endif 76 gid_t real_gid, effective_gid; 77 78 #define RELINQUISH_PRIVS { \ 79 real_uid = getuid(); \ 80 effective_uid = geteuid(); \ 81 real_gid = getgid(); \ 82 effective_gid = getegid(); \ 83 setreuid(effective_uid, real_uid); \ 84 setregid(effective_gid, real_gid); \ 85 } 86 87 #define RELINQUISH_PRIVS_ROOT(a,b) { \ 88 real_uid = (a); \ 89 effective_uid = geteuid(); \ 90 real_gid = (b); \ 91 effective_gid = getegid(); \ 92 setregid(effective_gid, real_gid); \ 93 setreuid(effective_uid, real_uid); \ 94 } 95 96 #define PRIV_START {\ 97 setreuid(real_uid, effective_uid); \ 98 setregid(real_gid, effective_gid); 99 100 #define PRIV_END \ 101 setregid(effective_gid, real_gid); \ 102 setreuid(effective_uid, real_uid); \ 103 } 104 105 #define REDUCE_PRIV(a,b) {\ 106 setreuid(real_uid, effective_uid); \ 107 setregid(real_gid, effective_gid); \ 108 effective_uid = (a); \ 109 effective_gid = (b); \ 110 setregid(effective_gid, real_gid); \ 111 setreuid(effective_uid, real_uid); \ 112 } 113 #endif 114