Should host/domain names travel over the internet with a trailing dot?

Mon Feb 25 15:56:49 UTC 2013

On Mon, Feb 25, 2013 at 09:49:19AM -0500, Jay Ashworth wrote:
> ----- Original Message -----
> > From: "Brian Reichert" <reichert at numachi.com>
> 
> > On Sun, Feb 24, 2013 at 12:10:20AM +1100, Mark Andrews wrote:
> [I believe this is Brian, then Mark: ]
> > > > When I did my initial development with OpenSSL, I observed:
> > > >
> > > > - If I did not have the rooted domain name in the SAN, then any SSL
> > > >   client stack would fail the verification if a rooted domain name
> > > >   was used to connect to the SSL server.
> > >
> > > Well you have a broken SSL client app. If it is accepting non legal
> > > hostnames it should be normalising them before passing them to the
> > > ssl layer.
> > 
> > From what little research I've done (only OpenSSL), the SSL client
> > is relying on getaddrinfo(3) to do name resolution. In turn, I
> > haven't found an implementation of getaddrinfo(3) that rejects
> > rooted domain names as non-legal.
> 
> Yes, but that's not the question, Brian, assuming I understand the problem
> as well as I think I do.  The question is not how the client does the
> name resolution on the client machine -- it's what it does with the domain
> name it's looking up before doing the SSL interaction with the server side,
> a process with which I'm not familiar enough to know if the client actually
> send the host/domain name to the server end.  Assuming it does -- and I
> am -- the question is: should it take the dot off.

My understanding is this:

Unless you're doing client certificate verification (wherein the
server is making decisions about which clients attempting a
connection), all validation/verification is done by the client.

The SSL client retrieves the server's certificate, and the set of
values in the Subject and the Subject Alternative Name is compared
against the hostname/IP address used to initiate the process.  This
comparison is (to my understanding) straight-forward (modulo UTF8
encodings, etc.).

The upshot (assuming I'm not totally off base here), is that other
than getaddrinfo(), nothing is acting on the semantics of the
supplied hostname (or IP address).  They are 'just strings', and
are (essentially) compared as such.

> Cheers,
> -- jr 'yeah, I know, it's Monday' a
> -- 
> Jay R. Ashworth                  Baylink                       jra at baylink.com
> Designer                     The Things I Think                       RFC 2100
> Ashworth & Associates     http://baylink.pitas.com         2000 Land Rover DII
> St Petersburg FL USA               #natog                      +1 727 647 1274

-- 
Brian Reichert				<reichert at numachi.com>
BSD admin/developer at large	