Re: Do you permit X11 via proxy firewall?

[dlang () diginsite com]

On Fri, 7 Sep 2007, ArkanoiD wrote:

> On Wed, Sep 05, 2007 at 04:48:46PM -0700, dlang () diginsite com wrote:
> > On Thu, 6 Sep 2007, ArkanoiD wrote:
> >
> > > That's most practical, almost everyone is doing that.
> > > So we can declare x11 gateways officially dead, i guess.
> > >
> > > On Wed, Sep 05, 2007 at 05:02:50PM -0400, Paul Melson wrote:
> > > > > And, if yes, how do you implement it?
> > > >
> > > > No, that's what 'ssh -X' is for.
> >
> > why is tunneling X through firewalls noticably safer then just doing packet
> > filtering to allow it through?
>
> Because it ensures proper endpoint authentication, encryption and ensures
> (well, to some extent) that no malicious connections will be made through
> the tunnel. At least does it better as packet filtering rules are static.
>
> The same rationale applies for x11 gateways: most of them present a kind
> of confirmation dialog for every new client connection.

I agree with the value of the authorization/authentication. encryption can be 
valuble in some environments, in others it just eats up CPU cycles.

> > if the only answer is becouse it prevents someone from intercepting and
> > tinkering with the TCP datastream then it's only relavent in some situations 
> > and
> > you are saying that in others it's perfectly safe to just do packet 
> > filtering.
> >
> > remember, just becouse everyone is doing it, it may not be safe.
>
> It is not, as nothing is safe, but sometimes it is acceptable risk ;-)

I agree, however I see a mindset creeping in that if you just encrypt it then 
it must be safe, and so I question statements like 'X is unsafe, but if you 
tunnel it through SSH then it's safe'

by the way, for those who are new to X, it allows programs to communicate with 
each other, even from different machines if they share a display. for a trivial 
example of this take two linux boxes, configure them to both use the same 
display (through whatever mechanism, including through SSH). then try to 
startup firefox on both machines (ideally, pass it a URL to start with)

what you will find is that when you try to start it up on the second machine it 
detects that you already have it running on the first machine and instruct that 
copy of firefox to open a window to the URL you told the second machine to 
display.

David Lang

> > remember almost everyone thinks that firewalls are just packet filters and 
> > have
> > no business actually looking at the packets that they let through.
>
> Not us ;-)
>
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