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Re: [Captive-portals] A new draft / idea - draft-wkumari-capport-icmp-unreach

Any middlebox between user and server can block traffic and redirect http.
An IETF protocol should not mix layering or be limited to specific access technology.

IPv6 has ‎autoconfiguration for obtaining IP addresses.

3GPP has specific GTP-based mechanisms for obtaining IP addresses.

So DHCP isn't even always used to access the internet.

David Dolson
Senior Software Architect, Sandvine Inc.
  Original Message
From: Yaron Sheffer
Sent: Friday, May 1, 2015 7:43 AM
To: Dave Dolson; Warren Kumari
Cc: [email protected]
Subject: Re: [Captive-portals] A new draft / idea - draft-wkumari-capport-icmp-unreach

As a user, I have never seen a case where the captive portal is not on
the same link as the client device, and never seen a case where an IP is
obtained using a non-DHCP mechanism when in a CP setting. Can you give
some concrete examples?


On 05/01/2015 05:49 AM, Dave Dolson wrote:
> I think it would be desirable to keep the captive portal mechanism independent of DHCP. The captive portal enforcement need not be on the same link as the user device. Furthermore, DHCP is not the only way to obtain an IP address.
> David Dolson
> Senior Software Architect, Sandvine Inc.
>    Original Message
> From: Warren Kumari
> Sent: Thursday, April 30, 2015 8:02 PM
> To: Yaron Sheffer
> Cc: [email protected]
> Subject: Re: [Captive-portals] A new draft / idea - draft-wkumari-capport-icmp-unreach
> On Thu, Apr 30, 2015 at 10:52 AM, Yaron Sheffer <[email protected]> wrote:
>> Hi Warren.
>> The security consideration (an attacker can send any arbitrary URL, and will
>> redirect you at will) seems like a showstopper to me.
> Yeah, we were a bit freaked about that too :-)
> I have removed the URL / URI stuff - now this is simply annotates
> Destination Unreachable to explain that the reason for the Dest
> Unreachable is because of a captive portal.
>> Also, once you have the DHCP mechanism, you can have client-initiated
>> communication to a well-defined interface, and you don't need to deal with
>> arbitrary connections being rejected. After all, the client needs to get an
>> IP address from DHCP before it can initiate any such connection.
> One reason that this is still useful is that eventually your captive
> portal connection will expire and the CP will close. If you have
> gotten CP information from DHCP, and then start getting these
> Destination Unreachables you will know to connect to the captive
> portal URL and pay again....
> So, basically, get CP information from DHCP and use it. After 4hours
> (or whatever), you start getting these new unrechables and know to
> connect and pay again...
> I think that the security implications are now the same as for
> "regular" (extended) Destination Unreachable.
> Thoughts?
> Thank you very much for your feedback,
> W
>> Thanks,
>>          Yaron
>> On 04/29/2015 11:32 PM, Warren Kumari wrote:
>>> Hi y'all.
>>> So, this short document discusses another way for Captive Portals to
>>> inform users that they are behind a CP. Basically, it uses an extended
>>> ICMP Destination Unreachable message to let the host know that the
>>> reason it cannot reach a destination is because it is behind a CP and
>>> also includes a URL to reach the CP.
>>> This idea is mainly David's, I'm largely the editor. We'd really like
>>> some feedback on this idea and the implementation we've written up.
>>> Obviously the document would need a bunch more work, but we'd like to
>>> get some idea if folk think this is worth pursuing.
>>> URL:
>>> https://www.ietf.org/internet-drafts/draft-wkumari-capport-icmp-unreach-00.txt
>>> Status:
>>> https://datatracker.ietf.org/doc/draft-wkumari-capport-icmp-unreach/
>>> Htmlized:
>>> https://tools.ietf.org/html/draft-wkumari-capport-icmp-unreach-00
>>> It is somewhat similar to the wkumari-dhc-capport document, but solves
>>> a different issue, in a different way - I think that they are
>>> complementary documents.
>>> Any feedback gratefully accepted.
>>> W
> --
> I don't think the execution is relevant when it was obviously a bad
> idea in the first place.
> This is like putting rabid weasels in your pants, and later expressing
> regret at having chosen those particular rabid weasels and that pair
> of pants.
>     ---maf
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