source3/lib/smbrun.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    run a command as a specified user
   4    Copyright (C) Andrew Tridgell 1992-1998
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19 */
  20
  21 #include "includes.h"
  22
  23 /* need to move this from here!! need some sleep ... */
  24 struct current_user current_user;
  25
  26 /****************************************************************************
  27 This is a utility function of smbrun().
  28 ****************************************************************************/
  29
  30 static int setup_out_fd(void)
  31 {
  32         int fd;
  33         pstring path;
  34
  35         slprintf(path, sizeof(path)-1, "%s/smb.XXXXXX", tmpdir());
  36
  37         /* now create the file */
  38         fd = smb_mkstemp(path);
  39
  40         if (fd == -1) {
  41                 DEBUG(0,("setup_out_fd: Failed to create file %s. (%s)\n",
  42                         path, strerror(errno) ));
  43                 return -1;
  44         }
  45
  46         DEBUG(10,("setup_out_fd: Created tmp file %s\n", path ));
  47
  48         /* Ensure file only kept around by open fd. */
  49         unlink(path);
  50         return fd;
  51 }
  52
  53 /****************************************************************************
  54 run a command being careful about uid/gid handling and putting the output in
  55 outfd (or discard it if outfd is NULL).
  56 ****************************************************************************/
  57
  58 int smbrun(char *cmd, int *outfd)
  59 {
  60         pid_t pid;
  61         uid_t uid = current_user.uid;
  62         gid_t gid = current_user.gid;
  63
  64         /*
  65          * Lose any kernel oplock capabilities we may have.
  66          */
  67         oplock_set_capability(False, False);
  68
  69         /* point our stdout at the file we want output to go into */
  70
  71         if (outfd && ((*outfd = setup_out_fd()) == -1)) {
  72                 return -1;
  73         }
  74
  75         /* in this method we will exec /bin/sh with the correct
  76            arguments, after first setting stdout to point at the file */
  77
  78         /*
  79          * We need to temporarily stop CatchChild from eating
  80          * SIGCLD signals as it also eats the exit status code. JRA.
  81          */
  82
  83         CatchChildLeaveStatus();
  84
  85         if ((pid=sys_fork()) < 0) {
  86                 DEBUG(0,("smbrun: fork failed with error %s\n", strerror(errno) ));
  87                 CatchChild();
  88                 if (outfd) {
  89                         close(*outfd);
  90                         *outfd = -1;
  91                 }
  92                 return errno;
  93     }
  94
  95         if (pid) {
  96                 /*
  97                  * Parent.
  98                  */
  99                 int status=0;
 100                 pid_t wpid;
 101
 102
 103                 /* the parent just waits for the child to exit */
 104                 while((wpid = sys_waitpid(pid,&status,0)) < 0) {
 105                         if(errno == EINTR) {
 106                                 errno = 0;
 107                                 continue;
 108                         }
 109                         break;
 110                 }
 111
 112                 CatchChild();
 113
 114                 if (wpid != pid) {
 115                         DEBUG(2,("waitpid(%d) : %s\n",(int)pid,strerror(errno)));
 116                         if (outfd) {
 117                                 close(*outfd);
 118                                 *outfd = -1;
 119                         }
 120                         return -1;
 121                 }
 122
 123                 /* Reset the seek pointer. */
 124                 if (outfd) {
 125                         sys_lseek(*outfd, 0, SEEK_SET);
 126                 }
 127
 128 #if defined(WIFEXITED) && defined(WEXITSTATUS)
 129                 if (WIFEXITED(status)) {
 130                         return WEXITSTATUS(status);
 131                 }
 132 #endif
 133
 134                 return status;
 135         }
 136
 137         CatchChild();
 138
 139         /* we are in the child. we exec /bin/sh to do the work for us. we
 140            don't directly exec the command we want because it may be a
 141            pipeline or anything else the config file specifies */
 142
 143         /* point our stdout at the file we want output to go into */
 144         if (outfd) {
 145                 close(1);
 146                 if (sys_dup2(*outfd,1) != 1) {
 147                         DEBUG(2,("Failed to create stdout file descriptor\n"));
 148                         close(*outfd);
 149                         exit(80);
 150                 }
 151         }
 152
 153         /* now completely lose our privileges. This is a fairly paranoid
 154            way of doing it, but it does work on all systems that I know of */
 155
 156         become_user_permanently(uid, gid);
 157
 158         if (getuid() != uid || geteuid() != uid ||
 159             getgid() != gid || getegid() != gid) {
 160                 /* we failed to lose our privileges - do not execute
 161                    the command */
 162                 exit(81); /* we can't print stuff at this stage,
 163                              instead use exit codes for debugging */
 164         }
 165
 166 #ifndef __INSURE__
 167         /* close all other file descriptors, leaving only 0, 1 and 2. 0 and
 168            2 point to /dev/null from the startup code */
 169         {
 170         int fd;
 171         for (fd=3;fd<256;fd++) close(fd);
 172         }
 173 #endif
 174
 175         execl("/bin/sh","sh","-c",cmd,NULL);
 176
 177         /* not reached */
 178         exit(82);
 179         return 1;
 180 }