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