at.tproj/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: /usr/local/www/cvsroot/FreeBSD/src/usr.bin/at/privs.h,v 1.10 2011/11/06 20:30:21 ed Exp $
  26  */
  27
  28 #ifndef _PRIVS_H
  29 #define _PRIVS_H
  30
  31 #include <unistd.h>
  32
  33 /* Relinquish privileges temporarily for a setuid or setgid program
  34  * with the option of getting them back later.  This is done by
  35  * utilizing POSIX saved user and group IDs.  Call RELINQUISH_PRIVS once
  36  * at the beginning of the main program.  This will cause all operations
  37  * to be executed with the real userid.  When you need the privileges
  38  * of the setuid/setgid invocation, call PRIV_START; when you no longer
  39  * need it, call PRIV_END.  Note that it is an error to call PRIV_START
  40  * and not PRIV_END within the same function.
  41  *
  42  * Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running
  43  * as root, and you want to drop back the effective userid to a
  44  * and the effective group id to b, with the option to get them back
  45  * later.
  46  *
  47  * If you no longer need root privileges, but those of some other
  48  * userid/groupid, you can call REDUCE_PRIV(a,b) when your effective
  49  * is the user's.
  50  *
  51  * Problems: Do not use return between PRIV_START and PRIV_END; this
  52  * will cause the program to continue running in an unprivileged
  53  * state.
  54  *
  55  * It is NOT safe to call exec(), system() or popen() with a user-
  56  * supplied program (i.e. without carefully checking PATH and any
  57  * library load paths) with relinquished privileges; the called program
  58  * can acquire them just as easily.  Set both effective and real userid
  59  * to the real userid before calling any of them.
  60  */
  61
  62 #ifndef MAIN
  63 extern
  64 #endif
  65 uid_t real_uid, effective_uid;
  66
  67 #ifndef MAIN
  68 extern
  69 #endif
  70 gid_t real_gid, effective_gid;
  71
  72 #define RELINQUISH_PRIVS { \
  73         real_uid = getuid(); \
  74         effective_uid = geteuid(); \
  75         real_gid = getgid(); \
  76         effective_gid = getegid(); \
  77         setegid(real_gid); \
  78         seteuid(real_uid); \
  79 }
  80
  81 #define RELINQUISH_PRIVS_ROOT(a, b) { \
  82         real_uid = (a); \
  83         effective_uid = geteuid(); \
  84         real_gid = (b); \
  85         effective_gid = getegid(); \
  86         setegid(real_gid); \
  87         seteuid(real_uid); \
  88 }
  89
  90 #define PRIV_START { \
  91         if (seteuid(0)<0) perr("cannot regain privs"); \
  92         if (setegid(effective_gid)<0) perr("cannot reset gid"); \
  93         if (seteuid(effective_uid)<0) perr("cannot reset uid"); \
  94 }
  95
  96 #define PRIV_END { \
  97         if (seteuid(0)<0) perr("cannot regain privs"); \
  98         if (setegid(real_gid)<0) perr("cannot reset gid"); \
  99         if (seteuid(real_uid)<0) perr("cannot reset uid"); \
 100 }
 101
 102 #define REDUCE_PRIV(a, b) { \
 103         PRIV_START \
 104         effective_uid = (a); \
 105         effective_gid = (b); \
 106         setregid((gid_t)-1, effective_gid); \
 107         setreuid((uid_t)-1, effective_uid); \
 108         PRIV_END \
 109 }
 110 #endif