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privs.h revision 1.3 
      1 /*	$NetBSD: privs.h,v 1.3 1995/03/25 18:13:41 glass Exp $	*/
      2 
      3 /*
      4  * privs.h - header for privileged operations
      5  * Copyright (c) 1993 by Thomas Koenig
      6  * All rights reserved.
      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 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 
     30 #ifndef _PRIVS_H
     31 #define _PRIVS_H
     32 
     33 #include <unistd.h>
     34 
     35 /* Relinquish privileges temporarily for a setuid program
     36  * with the option of getting them back later.  This is done by swapping
     37  * the real and effective userid BSD style.  Call RELINQUISH_PRIVS once
     38  * at the beginning of the main program.  This will cause all operatons
     39  * to be executed with the real userid.  When you need the privileges
     40  * of the setuid invocation, call PRIV_START; when you no longer
     41  * need it, call PRIV_END.  Note that it is an error to call PRIV_START
     42  * and not PRIV_END within the same function.
     43  *
     44  * Use RELINQUISH_PRIVS_ROOT(a) if your program started out running
     45  * as root, and you want to drop back the effective userid to a
     46  * and the effective group id to b, with the option to get them back
     47  * later.
     48  *
     49  * If you no longer need root privileges, but those of some other
     50  * userid, you can call REDUCE_PRIV(a) when your effective
     51  * is the user's.
     52  *
     53  * Problems: Do not use return between PRIV_START and PRIV_END; this
     54  * will cause the program to continue running in an unprivileged
     55  * state.
     56  *
     57  * It is NOT safe to call exec(), system() or popen() with a user-
     58  * supplied program (i.e. without carefully checking PATH and any
     59  * library load paths) with relinquished privileges; the called program
     60  * can aquire them just as easily.  Set both effective and real userid
     61  * to the real userid before calling any of them.
     62  */
     63 
     64 #ifndef MAIN
     65 extern
     66 #endif
     67 uid_t real_uid, effective_uid;
     68 
     69 #define RELINQUISH_PRIVS { \
     70 	real_uid = getuid(); \
     71 	effective_uid = geteuid(); \
     72 	seteuid(real_uid); \
     73 }
     74 
     75 #define RELINQUISH_PRIVS_ROOT(a) { \
     76 	real_uid = (a); \
     77 	effective_uid = geteuid(); \
     78 	seteuid(real_uid); \
     79 }
     80 
     81 #define PRIV_START { \
     82 	seteuid(effective_uid);
     83 
     84 #define PRIV_END \
     85 	seteuid(real_uid); \
     86 }
     87 
     88 #define REDUCE_PRIV(a) { \
     89 	seteuid(effective_uid); \
     90 	real_uid = effective_uid = (a); \
     91 	setuid(real_uid); \
     92 }
     93 #endif
     94