[Patch]: Fixing the PROCESS_DUP_HANDLE security hole (part 1).

[Christopher Faylor]

On Mon, Sep 29, 2003 at 09:55:25PM -0400, Pierre A. Humblet wrote:
>Here is a patch that allows to open master ttys without giving
>full access to the process, at least for access to the ctty. 
>
>It works by snooping the ctty pipe handles and duplicating them
>on the cygheap, for use by future opens in descendant processes.
>
>It passes all the tests I tried, but considering my lack of knowledge
>about ttys, everything is possible.

I checked in a variation of this patch.  It restructures the way
controlling tty is handled, making it a little easier to deal with
/dev/tty at the fhandler level.  I suspect that eventually there will
be a fhandler_ctty class but, for now, this seems to work.

I'm not 100% certain that I got the close-on-exec stuff right but, fwiw,
it seems to work with the combination of ssh/zsh which is usually a
pretty tough test for this kind of thing.  I did check to make sure that
access to a tty is now not allowed from a non-privileged account thanks
to the tty.cc change below.

Thanks for the patch and sorry for the delay.

cgf