usr.bin/at/privs.h

   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: src/usr.bin/at/privs.h,v 1.8 2001/09/04 16:15:51 ru Exp $
  26  * $DragonFly: src/usr.bin/at/privs.h,v 1.4 2007/08/26 16:12:27 pavalos Exp $
  27  */
  28
  29 #ifndef _PRIVS_H
  30 #define _PRIVS_H
  31
  32 #include <unistd.h>
  33
  34 /* Relinquish privileges temporarily for a setuid or setgid program
  35  * with the option of getting them back later.  This is done by
  36  * utilizing POSIX saved user and group IDs.  Call RELINQUISH_PRIVS once
  37  * at the beginning of the main program.  This will cause all operations
  38  * to be executed with the real userid.  When you need the privileges
  39  * of the setuid/setgid invocation, call PRIV_START; when you no longer
  40  * need it, call PRIV_END.  Note that it is an error to call PRIV_START
  41  * and not PRIV_END within the same function.
  42  *
  43  * Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running
  44  * as root, and you want to drop back the effective userid to a
  45  * and the effective group id to b, with the option to get them back
  46  * later.
  47  *
  48  * If you no longer need root privileges, but those of some other
  49  * userid/groupid, you can call REDUCE_PRIV(a,b) when your effective
  50  * is the user's.
  51  *
  52  * Problems: Do not use return between PRIV_START and PRIV_END; this
  53  * will cause the program to continue running in an unprivileged
  54  * state.
  55  *
  56  * It is NOT safe to call exec(), system() or popen() with a user-
  57  * supplied program (i.e. without carefully checking PATH and any
  58  * library load paths) with relinquished privileges; the called program
  59  * can acquire them just as easily.  Set both effective and real userid
  60  * to the real userid before calling any of them.
  61  */
  62
  63 extern uid_t real_uid, effective_uid;
  64 extern gid_t real_gid, effective_gid;
  65
  66 #define RELINQUISH_PRIVS { \
  67         real_uid = getuid(); \
  68         effective_uid = geteuid(); \
  69         real_gid = getgid(); \
  70         effective_gid = getegid(); \
  71         seteuid(real_uid); \
  72         setegid(real_gid); \
  73 }
  74
  75 #define RELINQUISH_PRIVS_ROOT(a, b) { \
  76         real_uid = (a); \
  77         effective_uid = geteuid(); \
  78         real_gid = (b); \
  79         effective_gid = getegid(); \
  80         setegid(real_gid); \
  81         seteuid(real_uid); \
  82 }
  83
  84 #define PRIV_START { \
  85         seteuid(effective_uid); \
  86         setegid(effective_gid); \
  87 }
  88
  89 #define PRIV_END { \
  90         setegid(real_gid); \
  91         seteuid(real_uid); \
  92 }
  93
  94 #define REDUCE_PRIV(a, b) { \
  95         PRIV_START \
  96         effective_uid = (a); \
  97         effective_gid = (b); \
  98         setreuid((uid_t)-1, effective_uid); \
  99         setregid((gid_t)-1, effective_gid); \
 100         PRIV_END \
 101 }
 102 #endif