Re: [TLS] access_administratively_disabled v2

Eric Rescorla <ekr@rtfm.com> Thu, 04 January 2018 15:59 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Thu, 4 Jan 2018 07:58:28 -0800
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To: =?UTF-8?Q?Mateusz_Jo=C5=84czyk?= <mat.jonczyk@o2.pl>
Cc: "Salz, Rich" <rsalz@akamai.com>, "Kaduk, Ben" <bkaduk@akamai.com>, "<tls@ietf.org>" <tls@ietf.org>
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Subject: Re: [TLS] access_administratively_disabled v2
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On Thu, Jan 4, 2018 at 7:22 AM, Mateusz Jończyk <mat.jonczyk@o2.pl> wrote:

> W dniu 04.01.2018 o 16:00, Salz, Rich pisze:
> >
> >>    Yes, at least in corporate environments, parental control solutions,
> etc.
> >     This will give a more understandable message to the user.
> >
> >
> > But as others have pointed out, the alert is not signed by the target
> origin.
> > So anyone along the path can inject this alert.
> Yup, just as anyone along the path can block the website.
> > So browsers cannot trust it,
> > and they certainly cannot display any possible text associated with it.
> In the version being discussed there is no associated text.
> >
> > How can you distinguish valid and proper use, from not valid and
> improper use
> > including DoS?
> Any intermediary (ISP, etc.) can block a website and this way cause a DoS.
> TLS
> changes nothing in this regard.
> This solution only makes it obvious that the DoS is introduced
> intentionally.
>
> > Without that algorithm specified, I doubt any browser
> > would implement this.  (And IMO I doubt they will do so anyway.)
> >
> In the version being discussed it is just another error value.
> I think browsers would implement it just like they will implement
> access_denied.
>

Well, support for access_denied is pretty minimal. I just tested in Chrome
and Firefox,
and they both generate pretty much generic error pages for both
access_denied
and some unknown alert number. Chrome provides a pretty opaque error code
(ERR_SSL_PROTOCOL_ERROR) and Firefox just provides a confusing error
about how it couldn't complete the connection.

-Ekr








> Greetings,
> Mateusz Jończyk
>
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