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 1.7 1999/12/05 19:57:14 charnier Exp $
  26  * $DragonFly: src/usr.bin/at/privs.h,v 1.3 2004/09/20 13:11:54 joerg Exp $
  27  */
  28
  29 #ifndef _PRIVS_H
  30 #define _PRIVS_H
  31
  32 #ifndef _USE_BSD
  33 #define _USE_BSD 1
  34 #include <unistd.h>
  35 #undef _USE_BSD
  36 #else
  37 #include <unistd.h>
  38 #endif
  39
  40 /* Relinquish privileges temporarily for a setuid or setgid program
  41  * with the option of getting them back later.  This is done by swapping
  42  * the real and effective userid BSD style.  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  * If you no longer need root privileges, but those of some other
  55  * userid/groupid, you can call REDUCE_PRIV(a,b) when your effective
  56  * is the user's.
  57  *
  58  * Problems: Do not use return between PRIV_START and PRIV_END; this
  59  * will cause the program to continue running in an unprivileged
  60  * state.
  61  *
  62  * It is NOT safe to call exec(), system() or popen() with a user-
  63  * supplied program (i.e. without carefully checking PATH and any
  64  * library load paths) with relinquished privileges; the called program
  65  * can acquire them just as easily.  Set both effective and real userid
  66  * to the real userid before calling any of them.
  67  */
  68
  69 extern uid_t real_uid, effective_uid;
  70 extern 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                               setreuid(effective_uid, real_uid); \
  78                               setregid(effective_gid, real_gid); \
  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                               setregid(effective_gid, real_gid); \
  87                               setreuid(effective_uid, real_uid); \
  88                           }
  89
  90 #define PRIV_START {\
  91                     setreuid(real_uid, effective_uid); \
  92                     setregid(real_gid, effective_gid);
  93
  94 #define PRIV_END \
  95                     setregid(effective_gid, real_gid); \
  96                     setreuid(effective_uid, real_uid); \
  97                     }
  98
  99 #define REDUCE_PRIV(a,b) {\
 100                         setreuid(real_uid, effective_uid); \
 101                         setregid(real_gid, effective_gid); \
 102                         effective_uid = (a); \
 103                         effective_gid = (b); \
 104                         setregid(effective_gid, real_gid); \
 105                         setreuid(effective_uid, real_uid); \
 106                     }
 107 #endif