[ILUG] PDF Creation

[Kenn Humborg]

On Sat, Apr 28, 2001 at 11:02:57AM +0100, Conor Daly wrote:
> If you want to use it in a pipe, you'll need to generate a tmp file from
> stdin and then ps2pdf the tmp file.
> 
> pipe or console?
> if [ -t 0 ]; then
>   # We're in a console here
>   ps2pdf $1
> else
>   # Here, we're in a pipe
>   # We need a temporary file here so something else can carry on
>   cat > /tmp/input-file$$.ps
>   ps2pdf /tmp/input-file$$.ps
>   mv /tmp/input-file$$.pdf suitable/location/and/filename.pdf
>   rm /tmp/input-file$$.ps
> fi

This is very insecure.  If this runs as root and J. Random Cracker
does 

   $ ln -s /etc/passwd /tmp/input-file2.ps 
   $ ln -s /etc/passwd /tmp/input-file3.ps 
   $ ...
   $ ln -s /etc/passwd /tmp/input-file32767.ps 

and then prints a new passwd file to this printer, then you're rooted.

To ensure that you get a private temp file that you _know_ didn't
exist beforehand, you should do:

   #!/bin/sh
   mkdir --mode=600 /tmp/mydir.$$$ || (
      echo dir already existed - aborting
      exit 1
   )

But, really, for stuff that runs under well-known UID, like print
spoolers, or cron jobs, you should create your own temporary 
directory under /var/spool or /var/local and do all your work
in there.

These days, the only reason a script should use /tmp or /var/tmp
is if you ABSOLUTELY NEED the temp files to be accessible to more
than one UID.  And even then you might be able to get away with 
creating a special group, putting these users in that group and
setting /var/local/mydir to be owned by that group.

Later,
Kenn