1 /* $NetBSD: privs.c,v 1.3 2018/02/25 23:48:16 htodd Exp $ */ 2 3 /* 4 * privs.c - privileged operations 5 * Copyright (C) 1993 Thomas Koenig 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. The name of the author(s) may not be used to endorse or promote 13 * products derived from this software without specific prior written 14 * permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23 * THEORY OF LIABILITY, WETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 * 27 * From: OpenBSD: privs.h,v 1.4 1997/03/01 23:40:12 millert Exp 28 */ 29 30 #include <unistd.h> 31 32 #include "privs.h" 33 34 /* 35 * Used by: usr.bin/at 36 * Used by: libexec/atrun 37 */ 38 39 /* 40 * Relinquish privileges temporarily for a setuid or setgid program 41 * with the option of getting them back later. This is done by 42 * using POSIX saved user and groups ids. Call RELINQUISH_PRIVS once 43 * at the beginning of the main program. This will cause all operations 44 * to be executed with the real userid. When you need the privileges 45 * of the setuid/setgid invocation, call PRIV_START; when you no longer 46 * need it, call PRIV_END. Note that it is an error to call PRIV_START 47 * and not PRIV_END within the same function. 48 * 49 * Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running 50 * as root, and you want to drop back the effective userid to a 51 * and the effective group id to b, with the option to get them back 52 * later. 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 65 uid_t real_uid, effective_uid; 66 gid_t real_gid, effective_gid; 67 68 void 69 privs_enter(void) 70 { 71 if (seteuid(effective_uid) == -1) 72 privs_fail("Cannot get user privs"); 73 if (setegid(effective_gid) == -1) 74 privs_fail("Cannot get group privs"); 75 } 76 77 void 78 privs_exit(void) 79 { 80 if (setegid(real_gid) == -1) 81 privs_fail("Cannot relinquish group privs"); 82 if (seteuid(real_uid) == -1) 83 privs_fail("Cannot relinquish user privs"); 84 } 85 86 void 87 privs_relinquish(void) 88 { 89 real_uid = getuid(); 90 effective_uid = geteuid(); 91 real_gid = getgid(); 92 effective_gid = getegid(); 93 privs_exit(); 94 } 95 96 void 97 privs_relinquish_root(uid_t ruid, gid_t rgid) 98 { 99 real_uid = ruid; 100 real_gid = rgid; 101 effective_uid = geteuid(); 102 effective_gid = getegid(); 103 privs_exit(); 104 } 105