Use reserved port only when required for NIS look-ups

[Jeff Law]

On 08/12/2012 03:16 AM, Kalle Olavi Niemitalo wrote:
>
> That risk does not apply, because the proposed change does not
> affect the _destination_ port of the requests sent by the client.
> It makes the client send the requests from unprivileged _source_
> ports unless the server is expected to restrict access by port.
I think that's a key point to remember.  The unprivileged port is the 
client side source port.  So from a security standpoint we're really 
just worried about information leakage.  Spoofing and the like isn't an 
issue.

> Perhaps an existing configuration file could be used.
> In the client machines, there may already be an yp.conf file,
> used by the ypbind daemon, which tells other client processes how
> to contact the NIS server.  Perhaps the list of secured maps could
> be added to yp.conf and then passed to the client processes via
> RPC, like the NIS server address.
Given that the secured maps are a function of the server, it makes sense 
to provide both the server name and list of secured maps in the same 
configuration file.

I think some sensible defaults would be good

Jeff