W3C home > Mailing lists > Public > semantic-web@w3.org > August 2014

Re: The ability to automatically upgrade a reference to HTTPS from HTTP

From: Reto Gmür <reto@gmuer.ch>
Date: Mon, 25 Aug 2014 16:00:49 +0200
Message-ID: <CALvhUEVKxToVprjA94-dLb-s49dA-bpDH=EpiDW6JHzxoq1jSA@mail.gmail.com>
To: Hugh Glaser <hugh@glasers.org>
Cc: Tim Berners-Lee <timbl@w3.org>, SW-forum Web <semantic-web@w3.org>, Public TAG List <www-tag@w3.org>
On Sat, Aug 23, 2014 at 10:13 PM, Hugh Glaser <hugh@glasers.org> wrote:

> Hi,
> Of course I can’t comment on TAG issues, but you did cc this to SemWeb, so
> I maybe I dare to comment.
> (Although I have always found indicating the security in the URI rather a
> strange thing, but I am sure there were/are good reasons for it.)
> There seems to be some confusion here between the URI and what it serves,
> something well know to SemWeb people :-)
> Or at least some stuff that might usefully be picked apart.
> And I think I detect it in your initial email.
> On 22 Aug 2014, at 18:00, Tim Berners-Lee <timbl@w3.org> wrote:
> >
> > There is a massive and reasonable push to get everything from HTTP space
> into HTTPS.
> > While this is laudable, the effect on the web as a hypertext system
> could be
> > very severe, in that links into http: space will basically break all
> over the place.
> > Basically every link in the HTTP web we are used to breaks.
> >
> > Here is a proposal, that we need this convention:
> >
> >        If two URIs differ only in the 's' of 'https:', then they may
> never be used for different things.
> This, to me, implies the URIs identify the same “thing” (NIR?).
> So
> <http://foo.bar/baz> owl:sameAs <https://foo.bar/baz>
> for all foo, bar and baz…
> That sounds like a pretty sound suggestion to me.
> Especially in the SemWeb/Linked Data world.
> Then you go on to talk about GET and the documents that come back in a
> similar vein.
> When we consider what gets served from a GET (or whatever we do), the
> owl:sameAs doesn’t mean that the documents served have the same content.
> As you say, for html, there might be a message saying to use the  other
> one - and of course that might actually be true of the RDF.
> I am well used to getting different information about NIRs from a variety
> of resources - after all, no-one enforces that the ttl, n3 and rdf
> documents have exactly the same stuff in them, and sometimes they don’t.
> And if html is also served, it certainly is very different from the RDF.
> As you say later, switching from one to the other should not give
> misleading information.
> Simply by considering the two URIs owl:sameAs, that should essentially
> make that happen, even if the server chooses to provide different RDF on
> the two URIs.
> They are just two (possibly) different documents about the same NIR.
> If we allow the sameAs meaning, then we can go on to discuss whether the
> documents actually can be assumed to be the same...

If the resource A and B are owl:sameAs we can conclude that if X is an
appropriate representation of A it is also an appropriate representation of
B. So while A and B might happen to dereference to different
representations each of there representation is a representation of the
single resource identified by both A and B.

You can also see the problem when you try to express your redirect message
in RDF. You cannot just send back the triple

<http://foo.bar/baz> <eg:redirectsTo> <https://foo.bar/baz> .

As if <http://foo.bar/baz> <owl:sameAs> <https://foo.bar/baz>,

the following triple can infered: <https://foo.bar/baz> <eg:redirectsTo> <
http://foo.bar/baz> - the opposite of what was intended.

If you wanted to reference to a specific resource name in RDF you would
have to use literals, but this would make things significantly more
complex. Think of an HTML redirect page with RDFa, the value of the href
attribute is considered to name a resource by IRI, so by owl-inference it
would be exchangeable with the other one.

So I think the original owl:sameAs suggestion ("If two URIs differ only in
the 's' of 'https:', then they may never be used for different things")
should be relaxed to allow to describe a distinction between the two such
as needed to express a redirect.


> Hope that helps a bit :-)
> Hugh
> PS
> I might fix sameAs.org to automatically give the other URI for any
> requests - would that be a good idea?
> Anyway want to tell me it would help them?
> >
> > That's sounds like a double negative way of putting it, but avoids
> saying things we don't want to mean.
> > I don't mean you must always serve up https or always serve up http.
> > Basically we are saying the 's' isn't a part of the identity of the
> resource, it is just a tip.
> >
> > So if I have successfully retrieved https:x  (for some value of x) and I
> have a link to http:x then I can satisfy following the link, by presenting
> what I got from https:x.
> > I know that whatever I get if I do do the GET on the http:x, it can't be
> different from what I have.
> >
> > The opposite however is NOT true, as a page which links to https:x
> requires the transaction to be made securely.  Even if I have already
> looked up http:x < i can't assume that I can use it for htts:x.  But for
> reasons of security alone -- it would still be against the principle if the
> server did deliberately serve something different.
> >
> > This means that if you have built two completely separate web sites in
> HTTPS and HTTP space, and you may have used the same path (module the 's')
> for different things, then you are in trouble. But who would do that?   I
> assume the large search engines know who.
> >
> > I suppose an exception for human readable pages may be that the http:
> version has a warning on it that the user should accessing the https: one.
> >
> > With linked data pages, where a huge amount of the Linked Open Data
> cloud is in http: space last time I looked, systems using URIs for
> identifiers need to be able to canonicalize them so tht anything said about
> http:x applies equally to https:x.
> >
> > What this means is that a client given an http:  URL in a reference is
> always free to try out the HTTPS, just adding an S, and use result if the
>  is successful.
> > Sometimes, if bowser security prevents a https-origin web page from
> loading any http resources as Firefox proudly does, [1], is you are writing
> a general purpose web app which has to read arbitrary web resources with
> XHR, ironically, you have to serve it over HTTP!     In the mean time, many
> client libraries will I assume need to just try HTTPS as that is all they
> are allowed.
> >
> > Or do we have to only build serious internet applications as browser
> extensions or native apps?
> >
> > For this any many related reasons, we need to first get a very high
> level principle that if a client switches from http to http of its own
> accord, then it can't be given misleading data as a result.
> >
> > I suspect has been discussed in many fora -- apologies if the issue is
> already noted and resolved, and do point to where it has
> >
> > TimBL
> >
> > [1]
> https://blog.mozilla.org/tanvi/2013/04/10/mixed-content-blocking-enabled-in-firefox-23/
> >
> >
> >
> >
> >
> >
> > In order for this switch to be made, transitions
> >
> --
> Hugh Glaser
>    20 Portchester Rise
>    Eastleigh
>    SO50 4QS
> Mobile: +44 75 9533 4155, Home: +44 23 8061 5652
Received on Monday, 25 August 2014 14:01:21 UTC

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