source/smbd/smbrun.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 1.9.
   4    external program running routine
   5    Copyright (C) Andrew Tridgell 1992-1997
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 */
  21
  22 #include "includes.h"
  23
  24
  25 /*******************************************************************
  26 close the low 3 fd's and open dev/null in their place
  27 ********************************************************************/
  28 static void close_fds(void)
  29 {
  30   int fd;
  31   int i;
  32   close(0); close(1); close(2);
  33   /* try and use up these file descriptors, so silly
  34      library routines writing to stdout etc won't cause havoc */
  35   for (i=0;i<3;i++) {
  36     fd = open("/dev/null",O_RDWR,0);
  37     if (fd < 0) fd = open("/dev/null",O_WRONLY,0);
  38     if (fd != i) return;
  39   }
  40 }
  41
  42
  43 /*
  44 This is a wrapper around the system() call to allow commands to run correctly
  45 as non root from a program which is switching between root and non-root
  46
  47 It takes 3 arguments as uid,gid,command and runs command after
  48 becoming a non-root user */
  49  int main(int argc,char *argv[])
  50 {
  51   int uid,gid;
  52
  53   close_fds();
  54
  55   if (argc != 4) exit(2);
  56
  57   uid = atoi(argv[1]);
  58   gid = atoi(argv[2]);
  59
  60   /* first become root - we may need to do this in order to lose
  61      our privilages! */
  62 #ifdef USE_SETRES
  63   setresgid(0,0,0);
  64   setresuid(0,0,0);
  65 #else
  66   setuid(0);
  67   seteuid(0);
  68 #endif
  69
  70 #ifdef USE_SETFS
  71   setfsuid(uid);
  72   setfsgid(gid);
  73 #endif
  74
  75 #ifdef USE_SETRES
  76   setresgid(gid,gid,gid);
  77   setresuid(uid,uid,uid);
  78 #else
  79   setgid(gid);
  80   setegid(gid);
  81   setuid(uid);
  82   seteuid(uid);
  83 #endif
  84
  85
  86   /* paranoia :-) */
  87   if (getuid() != uid)
  88     return(3);
  89
  90   if (geteuid() != getuid())
  91     return(4);
  92
  93   /* this is to make sure that the system() call doesn't run forever */
  94   alarm(30);
  95
  96   return(system(argv[3]));
  97 }