Re: [Captive-portals] Questions about PvD/API

[Martin Thomson <[e-mail]>]

Hi David,

Can you explain more about why you believe that a lower-layer protocol
needs to be used?

I remember a similar discussion about this about 10 years ago with
GEOPRIV.  Then it was asserted that DHCP was the only protocol that
could deliver location information to user equipment.  That discussion
took a long time, but ultimately ended with an HTTP-based protocol.  I
have no desire to repeat that experience.

It seems like this is - at least in part - based in how this might be
configured.  That is, you believe that a lower-layer protocol offers
no option for misconfiguration.  Is that correct?  Have I missed
something?


On 20 August 2017 at 00:12, David Bird <[e-mail]> wrote:
> HI Tommy,
>
> Agreed that RFC7710 is lacking notification of captive portal existence, it
> only provides configuration information. ICMP would provide the
> notification, as it does today for other forms of destination unreachable,
> port unreachable, etc. In your first reply, I thought you were suggesting
> that RFC7710 was at play along side PvD DHCP/RA (and I wasn't clear what you
> meant by DHCP/RA).
>
> I think we both also agree that taking about both a Capport API *and* PvD is
> adding to the confusion and we ultimately will not want two "APIs".
>
> ICMP today delivers more than hints... it provides signaling that can
> directly influence traffic. Yes, there are security concerns around ICMP,
> which is why it is common for it to be filtered out of networks (which is a
> good think for Capport ICMP, it is only for the edge network).
>
> Regarding ICMP and the "content details of the network" ... I think that
> statement conflates policy and enforcement. ICMP provides (as today)
> notification of enforcement, and RFC7710 provides where to find out about
> the policy (ToS, etc).
>
> The JSON API becomes a "web service" when it has a http(s):// in front of it
> :) .. but, indeed, my concern is in the transport protocol. It being a URL
> signals that this is meant to be deployed alongside the portal, or otherwise
> 'remotely'... Vendors will likely have a "PvD URL: " configuration dialog
> ... and there will be many hotspot services companies updating their "Howto"
> instructions with their PvD URL info... it is a web service.
>
> I welcome suggestions that put that JSON API into a lower layer network
> protocol. We could stuff JSON into ICMP :)
>
> Maybe there is a way to merge ICMP and PvD -- to where ICMP provides the
> notification (with tokens) and PvD provides the policy (based on these
> tokens) (?)
>
> With regard to vendor (NAS/UE) cooperation, perhaps PvD could be a new
> start, but thus far (as my quote of Cisco documentation suggests), it is
> more about what users/venues want. Cisco already today actively avoids iOS
> captive portal detection because the "pseudo-browser" (as they call it) does
> work with their portal. That is a problem that could be solve today by
> Apple/Cisco, couldn't it? Just by not using the pseudo browser...
> introducing PvD doesn't resolve the core problem there, but does make it
> easier to avoid that pseudo browser.
>
> You also said "We can still get to a captive portal once the user goes into
> the browser." ... However, this is increasingly untrue as the work moves to
> https... So, doing this avoidance of detection will still be a problem.
>
> Cheers,
> David
>
>
> On Fri, Aug 18, 2017 at 7:23 PM, Tommy Pauly <[e-mail]> wrote:
>>
>> Hi David,
>>
>> My thoughts with regards to RFC 7710 is that it is not deployed as far as
>> I know, and no client stack respects the value sent in 7710. Without some
>> API extensions, it isn't directly better than what we currently have.
>> Ideally, this would not be an API that would get deployed if we were also
>> using PvDs. My concern is that if PvDs are used for enterprise and private
>> networks, we'll have a very similar but less complete path based on RFC
>> 7710. We could end up deprecating or replacing that RFC, which was mentioned
>> in our last meeting. I don't think RFC 7710 can be used without a URL, which
>> is why I think we need a solution that does a better job of indicating the
>> lack of captive or other extended network info.
>>
>> I would hope that since both iOS and Android stack developers are working
>> on the UE side, we would actually see UE deployment of PvDs before any
>> captive vendors adopt PvDs, and we'd be standardizing around Cisco/etc
>> enterprise deployments. By the time there were NAS vendors deploying, they
>> would test with both iOS and Android devices to validate support.
>>
>> Basing our standards on the idea that devices (either networks or UE's)
>> may implement the RFCs incorrectly seems to be a difficult starting point.
>>
>> I like the point you bring up of splitting network notifications from web
>> APIs. There is a need to be judicious about what properties fall into each
>> category. I think you're saying that the fact that there is a captive
>> network can be signaled via ICMP, etc, as a network-level property. While
>> ICMP is a fine solution for giving the UE hints when something has expired,
>> I am concerned that (possibly unsolicited) network signaling is not the
>> correct mechanism for the content details of the network, whether that is
>> the enterprise network properties, or the captive network Terms &
>> Conditions, tokens, expiration timers, and URLs for various kinds of user
>> interaction. An JSON API is one form of grabbing information—I don't think
>> we should necessarily interpret that as something that is a high-level Web
>> interaction. We could create some custom protocol over UDP like DNS records
>> to get the information (that would be a lot of new protocol work here that
>> people may not be willing to get into), but the key is that it needs to be
>> the choice of a UE device that understands how to request and parse content
>> that initiates a lookup, and can fetch information from the network
>> infrastructure.
>>
>> With regards to your assertion that we'll always revert to doing a probe,
>> I still would like to believe that if we have a network that advertises a
>> PvD with no extended information, or extended information that doesn't
>> include a captive portal, we can avoid the probe altogether. Will we still
>> have networks that redirect HTTP requests? Yes. But that's no different from
>> the scenario today in which a network whitelists our captive detection
>> probes. We can still get to a captive portal once the user goes into the
>> browser. We can stop doing probes whenever the RA on the network indicates
>> that it supports explicit signaling about network properties. If a network
>> operator wants to invoke the system-level captive interaction, then they
>> will follow the RFCs we come up in the CAPPORT group as long as UEs end up
>> deploying support first. If they want to avoid it, or they have a broken
>> network, things will be like networks that whitelist our probes today. Not
>> great, but still possible for the user to get through. My main goal in these
>> standards is to make it possible for a network to give the user a good
>> experience; not to make it impossible for the user to have a sub-par
>> experience (since I don't think that goal is achievable).
>>
>> Best,
>> Tommy
>>
>>
>> On Aug 18, 2017, at 5:52 PM, David Bird <[e-mail]> wrote:
>>
>> Thanks Tommy,
>>
>> I don't dispute that PvD provides an elegant set of solutions --
>> particularly in enterprise and other 'private' networks. I question,
>> however, the value in public(/guest) access -- where everyone wants you to
>> access their network over others, for 'retail analytic' or
>> branding/attribution(/exploit) purposes.
>>
>> Another way to see the PvD integration/deployment:
>>
>> 1. Today, we join a network, always do a probe, which redirects to captive
>> portal
>> 2. A PvD URL is provide, so a captive portal notification is generated to
>> the user (is that what 'we just make a connection directly' means?)
>> 3. We may have also gotten RFC7710 URL, there are potentially two APIs in
>> play at the same time, which is extra confusing (?)
>> 4. The first NAS vendor release products with support, venues deploy and
>> start 'fiddling' with the new feature and URL to PvD end-points
>> 5. The first UE vendor releases products with support, start using it at
>> said venues... complain to vendor about problems unique to this new device
>> 6. In some networks, users complain that *only* their new PvD device is
>> seeing a captive portal, while all their other devices do not. Staff at the
>> coffee shop don't believe me; all their devices work too.
>>
>> I think there are fundamental issues in splitting what should be 'network
>> notification' into web APIs....
>>
>> 1. Tomorrow, we join a network, always do a probe, which redirects to
>> captive portal
>>
>> It wasn't clear in your e-mail if RFC7710 can be used *without* providing
>> a URL, or is there a PvD specific DHCP option?
>>
>> Thanks,
>> David
>>
>>
>> On Wed, Aug 16, 2017 at 9:20 AM, Tommy Pauly <[e-mail]> wrote:
>>>
>>> Hi David,
>>>
>>> You mention in one of your emails that you'd expect there to be many
>>> "broken PvD" deployments, which would either necessitate ignoring PvD and
>>> using legacy mechanisms, or else having the user face a broken portal. My
>>> impression is that if client-side deployments fail closed—that is, if there
>>> is a PvD advertised, but it does not work well, then we treat the network as
>>> broken. If this client behavior is consistent from the start of deployment,
>>> then I would think that deployments would notice very quickly if they are
>>> broken. The fundamental part of the PvD being advertised is in the RAs—if
>>> our DHCP or RAs are broken on a network, we generally are going to be broken
>>> anyhow.
>>>
>>> As far as where the API resides, I appreciate your explanation of the
>>> various complexities. My initial take is this:
>>>
>>> - Where a PvD is being served is up to the deployment, and determined by
>>> the entity that is providing the RAs. To that end, the server that hosts the
>>> API for extended PvD information may be very different for
>>> enterprise/carrier scenarios than in captive portals for coffee shops.
>>> - For the initial take for Captive Portals, I would co-locate the "PvD
>>> API" server with the "Captive API" and "Captive Web Server". Presumably, the
>>> device that was previously doing the HTTP redirects would be able to do the
>>> similar coordination of making sure the PvD ID that is given out to clients
>>> matches the PvD API server (which is the same as the "Captive Web Server").
>>>
>>> For the captive use-case, I see the integration of PvDs as an incremental
>>> step:
>>>
>>> 1. Today, we join a network, always do a probe, which may get redirected
>>> to a captive web server
>>> 2. With RFC 7710, we would join a network and do the same as (1), unless
>>> the captive URL is given in the DHCP/RA and we just make a connection
>>> directly.
>>> 3. With the Captive API draft, we can interact with the portal other than
>>> just showing a webpage; but this may still be bootstrapped by 7710 if not
>>> using another mechanism
>>> 4. With PvDs, the mechanism in 7710 is generalized to support APIs other
>>> than just captive, and can indicate that no captive portal or other extended
>>> info is present; and the PvD API in this form is just a more generic version
>>> of the captive API that allows us to use the same mechanism for other
>>> network properties that aren't specifically captive (like enterprise network
>>> extended info, or walled gardens)
>>>
>>> Getting into the arms race of people avoiding the captive probes: if
>>> someone doesn't want to interact with the client OS's captive portal system,
>>> they can and likely will not change anything and just keep redirecting
>>> pages. Hopefully if a better solution becomes prevalent enough in the
>>> future, client OS's will be able to just ignore and reject any network that
>>> redirects traffic, and the only supported captive portals would be ones that
>>> interact in specified ways and advertise themselves as captive networks. In
>>> order to get to this point, there certainly needs to be a carrot to
>>> incentivize adoption. My goal with the more flexible interaction supported
>>> by PvD is that we will allow the networks to provide a better user
>>> experience to people joining their networks, and integrate with client OS's
>>> to streamline the joining process (notification of the network being
>>> available, who owns it, how to accept and how to pay), the maintenance
>>> process (being able to integrate time left or bytes left on the network into
>>> the system UI), and what is allowed or not on the network.
>>>
>>> Thanks,
>>> Tommy
>>>
>>>
>>> On Aug 16, 2017, at 6:51 AM, David Bird <[e-mail]> wrote:
>>>
>>> My question about where the PvD API resides was somewhat rhetorical. In
>>> reality, I'm sure you will find all of the above - In the NAS (e.g. Cisco),
>>> at the hotspot services provider, and something hosted next to the venues
>>> website. It depends mostly on how this URL is configured, and by whom. (One
>>> could imagine people doing all sorts of things).
>>>
>>> My question more specifically for the authors is, how would Cisco
>>> implement PvD for Guest/Public access and would it actively stop avoiding
>>> Apple captive portal detection? Or, would turning on PvD just make that
>>> 'feature' easier to implement?
>>>
>>> On Tue, Aug 15, 2017 at 5:19 PM, Erik Kline <[e-mail]> wrote:
>>>>
>>>> Randomly selecting Tommy and Eric so this bubbles up in their inbox.
>>>>
>>>> On 2 August 2017 at 10:36, David Bird <[e-mail]> wrote:
>>>> > Could an author of PvD help me understand the following questions for
>>>> > each
>>>> > of the diagrams below I found on the Internet -- which represent some
>>>> > typical hotspot configurations out there...
>>>> >
>>>> > - Where would the API reside?
>>>> >
>>>> > - Who 'owns' the API?
>>>> >
>>>> > - How does the API keep in-sync with the NAS? Who's responsible for
>>>> > that
>>>> > (possibly multi-vendor, multi-AAA) integration?
>>>> >
>>>> > 1) Typical Hotspot service company outsourcing:
>>>> >
>>>> > http://cloudessa.com/wp-content/uploads/2013/08/shema-CaptivePortalSolution_beta2b.png
>>>> >
>>>> > 2) Same as above, except venue owns portal:
>>>> >
>>>> > http://cloudessa.com/wp-content/uploads/2013/07/solutions_hotspots-co-working-cloudessa_2p1.png
>>>> >
>>>> > 3) Now consider the above, but the venue has more roaming partners and
>>>> > multi-realm RADIUS setup in their Cisco NAS:
>>>> >
>>>> > http://www.cisco.com/c/en/us/td/docs/wireless/controller/8-3/config-guide/b_cg83/b_cg83_chapter_0100111.html
>>>> > describes many options -- including separate MAC authentication
>>>> > sources,
>>>> > optional portals for 802.1x (RADIUS) authenticated users, and so much
>>>> > more...
>>>> >
>>>> > "Cisco ISE supports internal and external identity sources. Both
>>>> > sources can
>>>> > be used as an authentication source for sponsor-user and guest-user
>>>> > authentication."
>>>> >
>>>> > Also note this interesting article:  the section Information About
>>>> > Captive
>>>> > Bypassing and how it describes how to avoid Apple captive portal
>>>> > detection!!! "If no response is received, then the Internet access is
>>>> > assumed to be blocked by the captive portal and Apple’s Captive
>>>> > Network
>>>> > Assistant (CNA) auto-launches the pseudo-browser to request portal
>>>> > login in
>>>> > a controlled window. The CNA may break when redirecting to an ISE
>>>> > captive
>>>> > portal. The controller prevents this pseudo-browser from popping up."
>>>> >
>>>> >
>>>> >
>>>> > _______________________________________________
>>>> > Captive-portals mailing list
>>>> > [e-mail]
>>>> > https://www.ietf.org/mailman/listinfo/captive-portals
>>>> >
>>>
>>>
>>>
>>
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