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 26 #ifndef _PRIVS_H 27 #define _PRIVS_H 28 29 #ifndef _USE_BSD 30 #define _USE_BSD 1 31 #include <unistd.h> 32 #undef _USE_BSD 33 #else 34 #include <unistd.h> 35 #endif 36 37 /* Relinquish privileges temporarily for a setuid or setgid program 38 * with the option of getting them back later. This is done by swapping 39 * the real and effective userid BSD style. Call RELINQUISH_PRIVS once 40 * at the beginning of the main program. This will cause all operatons 41 * to be executed with the real userid. When you need the privileges 42 * of the setuid/setgid invocation, call PRIV_START; when you no longer 43 * need it, call PRIV_END. Note that it is an error to call PRIV_START 44 * and not PRIV_END within the same function. 45 * 46 * Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running 47 * as root, and you want to drop back the effective userid to a 48 * and the effective group id to b, with the option to get them back 49 * later. 50 * 51 * If you no longer need root privileges, but those of some other 52 * userid/groupid, you can call REDUCE_PRIV(a,b) when your effective 53 * is the user's. 54 * 55 * Problems: Do not use return between PRIV_START and PRIV_END; this 56 * will cause the program to continue running in an unprivileged 57 * state. 58 * 59 * It is NOT safe to call exec(), system() or popen() with a user- 60 * supplied program (i.e. without carefully checking PATH and any 61 * library load paths) with relinquished privileges; the called program 62 * can aquire them just as easily. Set both effective and real userid 63 * to the real userid before calling any of them. 64 */ 65 66 #ifndef MAIN 67 extern 68 #endif 69 uid_t real_uid, effective_uid; 70 71 #ifndef MAIN 72 extern 73 #endif 74 gid_t real_gid, effective_gid; 75 76 #define RELINQUISH_PRIVS { \ 77 real_uid = getuid(); \ 78 effective_uid = geteuid(); \ 79 real_gid = getgid(); \ 80 effective_gid = getegid(); \ 81 setreuid(effective_uid, real_uid); \ 82 setregid(effective_gid, real_gid); \ 83 } 84 85 #define RELINQUISH_PRIVS_ROOT(a,b) { \ 86 real_uid = (a); \ 87 effective_uid = geteuid(); \ 88 real_gid = (b); \ 89 effective_gid = getegid(); \ 90 setregid(effective_gid, real_gid); \ 91 setreuid(effective_uid, real_uid); \ 92 } 93 94 #define PRIV_START {\ 95 setreuid(real_uid, effective_uid); \ 96 setregid(real_gid, effective_gid); 97 98 #define PRIV_END \ 99 setregid(effective_gid, real_gid); \ 100 setreuid(effective_uid, real_uid); \ 101 } 102 103 #define REDUCE_PRIV(a,b) {\ 104 setreuid(real_uid, effective_uid); \ 105 setregid(real_gid, effective_gid); \ 106 effective_uid = (a); \ 107 effective_gid = (b); \ 108 setregid(effective_gid, real_gid); \ 109 setreuid(effective_uid, real_uid); \ 110 } 111 #endif 112