clipboard integration -- possible security implications

William Hubbs w.d.hubbs at
Thu Oct 22 11:38:10 EDT 2009

Hi again Tony,

as far as I know, speakup can't write environment variables.  Even if it
did, they would not be accessible to you in your login session since the
environment is different for every session.

How do you define the current user?  It can't be the one who is
logged in since multiple users can be logged in even on a machine that
doesn't have network access (you can log into one vt as root and another
as yourself for example).

That puts us back in a situation where the files you are talking about
have to be only accessible to root and you would have to find another
way to create the random file name you are talking about.

What do you think?


On Thu, Oct 22, 2009 at 12:57:43AM -0700, Tony Baechler wrote:
> Hi,
> Ah, of course. OK, we need something like mktemp. Can Speakup set 
> environment variables? What about restricting it so that it can only 
> write the clipboard under /tmp? What I'm thinking is that somehow a 
> random filename needs to be generated and somehow the name has to be 
> communicated to the user. By writing under /tmp, it avoids the 
> /boot/vmlinuz problem that you outline but people could still create 
> symlinks, so make it a random file that changes based on the ID of the 
> logged in user. Put the name of that file in 
> /sys/accessibility/speakup/clip. That creates an extra step for the user 
> because they would have to open two files, first to find what the random 
> file is and second to open the actual clipboard text, but that should be 
> very secure. Obviously, the owner of both files would have to be the 
> current user.
> If you can write to the environment, you could set a variable with the 
> random filename which could be read by any shell script, again such as 
> speakupconf or just "set" by itself. It could also be used in a script 
> if someone wanted to copy it to a predictable name, in which case 
> security would be their problem.
> On 10/21/2009 9:02 AM, William Hubbs wrote:
> > If another user logs in, they would need to have permission to access
> >> files under /home/tony to do any good.  If they wanted to copy text to
> >> the clipboard, I would have to login as root and change the above
> >> location or they could use something like speakupconf.  That way, no
> >> actual text would be stored under /sys at all from the clipboard.
> >>      
> >
> >   This idea leads to another issue.  If your system is compromised, it
> >   would be possible for someone to put something in the sys file like:
> >
> >   /boot/vmlinuz
> >
> >   and take your system down since the kernel could be directed to
> >   overwrite any file in the filesystem.
> >    
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