Hi, My colleagues and I are currently pursuing a TLS extension to address a very similar scenario. It is good to see we are not alone in this pursuit. We are still working out details at a somewhat high level but expect to have a draft out shortly. Please feel free to contact me if you would like to be included in our discussions.
Thanks,John Woodworth -------- Original message --------From: Eric Rescorla <e...@rtfm.com> Date: 1/2/18 2:37 PM (GMT-05:00) To: Mateusz Jończyk <mat.jonc...@o2.pl> Cc: tls@ietf.org Subject: Re: [TLS] Captive portals, "access administratively disabled" and alert messages A similar idea was proposed a while back, albeit with simpler semantics: https://tools.ietf.org/html/draft-lemon-tls-blocking-alert-00 Discussion here: https://www.ietf.org/mail-archive/web/tls/current/msg20264.html I'm not really enthusiastic about any of these ideas for any of the administratively prohibiteduse cases because the information being provided to the user is unverifiable. I.e., thisjust tells you that someone on the network didn't like it, but the message itself is justan assertion (this is different from 451 in that that's provided inside the TLS channelif TLS is used). It's not like, for instance, the browser should display the string to theuser as if it were true. The captive portal case seems a bit more plausible, in that it can be machine processedby the client to do some sort of captive portal detection thingy (e.g., connect toa site over HTTP). However, the right place to bring this kind of proposal would probably beCAPPORT (https://tools.ietf.org/wg/capport/). However, I see that they are pursuinga different direction based on HTTP. -Ekr On Tue, Jan 2, 2018 at 11:15 AM, Mateusz Jończyk <mat.jonc...@o2.pl> wrote: Hello, OpenDNS by default blocks websites that are used for phishing and optionally other sites as configured by the deployer. It does this by DNS poisoning: it responds with a forged A or AAAA response that redirects to their server. An example website blocked by OpenDNS in this manner is https://internetbadguys.com/. When OpenDNS blocks a website that is served by HTTPS, the user is presented with a "Certificate Error" message. To see what happened, she then has to accept the incorrect certificate or visit the plain HTTP version of the webpage. This creates some problems: aside from a bad user experience, it makes users accustomed to ignoring certificate errors. Another problem is created by captive portals: networks that use "a web page which is displayed to newly connected users before they are granted broader access to network resources." (Wikipedia). This could be solved by specifying two new values of AlertDescription: access_administratively_disabled and captive_portal as well as a new field to struct Alert: alert_message. Let alert_message be a fixed-length UTF-8-encoded string. It would be only valid for (description == access_administratively_disabled || description == captive_portal) and otherwise a client would HAVE TO ignore it. It would be plain-text for simplicity, shortness and security. It would be null-terminated and then randomly padded to a size of perhaps 100 bytes. A TLS client would HAVE TO filter the message for any odd characters, invalid UTF-8 sequences, etc. as will be specified in the standard. Greetings, Mateusz Jończyk _______________________________________________ TLS mailing list TLS@ietf.org https://www.ietf.org/mailman/listinfo/tls
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