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Re: Bug#519339: ITP: tmux -- an alternative to screen, licensed under 3-BSD

On Sat, 14 Mar 2009, Mike Hommey <mh@glandium.org> wrote:
> > [Mike Hommey]
> >
> > > Screen does that too, so that would hardly be less secure than screen.
> >
> > Well, if by "in /tmp" you mean "in /var/run/screen".
> Well, that's a Debian thing. Upstream default is /tmp/screens, and last
> time I checked on RH, it was there too.

RHEL 5.2 has /var/run/screen.  Debian/Lenny and RHEL 5.2 work in a similar 
way, you have a setgid screen program and the /var/run/screen directory is 
writable by the group.  In Debian there is an init.d script to create that 
directory (presumably to support tmpfs /var/run) while in RHEL it is 
installed as part of the package.

RHEL 4.7 has the directory /tmp/screens for root and /tmp/uscreens for user 
sessions.  /tmp/uscreens is owned by the first non-root user who ran screen 
and group writable.  If that user is hostile (or even clueless) then "chmod 
700 /tmp/uscreens" will make it unusable for others.  I don't know whether 
they can do anything really bad, screen appears to check the ownership of the 
socket so it should be OK apart from DOS attacks.

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