Re: Xwindows security?

[J.S.Peatfield () amtp cam ac uk (Jon Peatfield)]

(2nd attempt, 1st one had finger trouble.)

>   Jon> One trick you can do with this is to get the X server to run
>   Jon> through all current windows and perform the check again on
>   Jon> their existing connection based on the current rules.  A server
>
> This is a decent idea, though you'd have to keep state about the user
> associated with the display connection in the server. If you're going
> to be keeping this kind of information in the server on a
> per-connection basis, you may as well keep some sort of token or
> cookie 

You have a choice here.  Either cache the information on a per connection 
basis or rescan all connections.  (For each connection you know which host it 
is to (stored in the TCP layer) and you can just do the Pident lookup again.)  
Personally I'd prefer to cache the values, memory is cheaper than network 
bandwidth:-)

Yes you could keep a (cookie,host) pair per connection instead but then you 
still have to distribute them to each host.  Cookies work well with NFS shared 
home directories in small clusters of trusted machines and other cases where 
you don't have to shunt them over the network.  Using Pident saves the cookie 
pushing and provides most of the features of (cookie,host) pairs.

Yes it doesn't work in all cases.  E.g. X over DecNet, but I'm sure people can 
invent tricks to do similar lookups.  (Unix-Domain-Sockets can be done for 
example by a daemon which looks to see who has the other end open.)

  -- Jon