source/lib/smbrun.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 1.9.
   4    run a command as a specified user
   5    Copyright (C) Andrew Tridgell 1992-1998
   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 /* need to move this from here!! need some sleep ... */
  25 struct current_user current_user;
  26
  27 extern int DEBUGLEVEL;
  28
  29 /****************************************************************************
  30 This is a utility function of smbrun().
  31 ****************************************************************************/
  32
  33 static int setup_out_fd(void)
  34 {
  35         int fd;
  36         pstring path;
  37
  38         slprintf(path, sizeof(path)-1, "%s/smb.XXXXXX", tmpdir());
  39
  40         /* now create the file */
  41         fd = smb_mkstemp(path);
  42
  43         if (fd == -1) {
  44                 DEBUG(0,("setup_out_fd: Failed to create file %s. (%s)\n",
  45                         path, strerror(errno) ));
  46                 return -1;
  47         }
  48
  49         DEBUG(10,("setup_out_fd: Created tmp file %s\n", path ));
  50
  51         /* Ensure file only kept around by open fd. */
  52         unlink(path);
  53         return fd;
  54 }
  55
  56 /****************************************************************************
  57 run a command being careful about uid/gid handling and putting the output in
  58 outfd (or discard it if outfd is NULL).
  59 ****************************************************************************/
  60
  61 int smbrun(char *cmd, int *outfd)
  62 {
  63         pid_t pid;
  64         uid_t uid = current_user.uid;
  65         gid_t gid = current_user.gid;
  66
  67         /*
  68          * Lose any kernel oplock capabilities we may have.
  69          */
  70         oplock_set_capability(False, False);
  71
  72         /* point our stdout at the file we want output to go into */
  73
  74         if (outfd && ((*outfd = setup_out_fd()) == -1)) {
  75                 return -1;
  76         }
  77
  78         /* in this method we will exec /bin/sh with the correct
  79            arguments, after first setting stdout to point at the file */
  80
  81         /*
  82          * We need to temporarily stop CatchChild from eating
  83          * SIGCLD signals as it also eats the exit status code. JRA.
  84          */
  85
  86         CatchChildLeaveStatus();
  87
  88         if ((pid=sys_fork()) < 0) {
  89                 DEBUG(0,("smbrun: fork failed with error %s\n", strerror(errno) ));
  90                 CatchChild();
  91                 if (outfd) {
  92                         close(*outfd);
  93                         *outfd = -1;
  94                 }
  95                 return errno;
  96     }
  97
  98         if (pid) {
  99                 /*
 100                  * Parent.
 101                  */
 102                 int status=0;
 103                 pid_t wpid;
 104
 105
 106                 /* the parent just waits for the child to exit */
 107                 while((wpid = sys_waitpid(pid,&status,0)) < 0) {
 108                         if(errno == EINTR) {
 109                                 errno = 0;
 110                                 continue;
 111                         }
 112                         break;
 113                 }
 114
 115                 CatchChild();
 116
 117                 if (wpid != pid) {
 118                         DEBUG(2,("waitpid(%d) : %s\n",(int)pid,strerror(errno)));
 119                         if (outfd) {
 120                                 close(*outfd);
 121                                 *outfd = -1;
 122                         }
 123                         return -1;
 124                 }
 125
 126                 /* Reset the seek pointer. */
 127                 if (outfd) {
 128                         sys_lseek(*outfd, 0, SEEK_SET);
 129                 }
 130
 131 #if defined(WIFEXITED) && defined(WEXITSTATUS)
 132                 if (WIFEXITED(status)) {
 133                         return WEXITSTATUS(status);
 134                 }
 135 #endif
 136
 137                 return status;
 138         }
 139
 140         CatchChild();
 141
 142         /* we are in the child. we exec /bin/sh to do the work for us. we
 143            don't directly exec the command we want because it may be a
 144            pipeline or anything else the config file specifies */
 145
 146         /* point our stdout at the file we want output to go into */
 147         if (outfd) {
 148                 close(1);
 149                 if (dup2(*outfd,1) != 1) {
 150                         DEBUG(2,("Failed to create stdout file descriptor\n"));
 151                         close(*outfd);
 152                         exit(80);
 153                 }
 154         }
 155
 156         /* now completely lose our privileges. This is a fairly paranoid
 157            way of doing it, but it does work on all systems that I know of */
 158
 159         become_user_permanently(uid, gid);
 160
 161         if (getuid() != uid || geteuid() != uid ||
 162             getgid() != gid || getegid() != gid) {
 163                 /* we failed to lose our privileges - do not execute
 164                    the command */
 165                 exit(81); /* we can't print stuff at this stage,
 166                              instead use exit codes for debugging */
 167         }
 168
 169 #ifndef __INSURE__
 170         /* close all other file descriptors, leaving only 0, 1 and 2. 0 and
 171            2 point to /dev/null from the startup code */
 172         {
 173         int fd;
 174         for (fd=3;fd<256;fd++) close(fd);
 175         }
 176 #endif
 177
 178         execl("/bin/sh","sh","-c",cmd,NULL);
 179
 180         /* not reached */
 181         exit(82);
 182         return 1;
 183 }