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Date: Tue, 10 Feb 2015 18:14:12 -0500
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From: Erik Nygren <erik@nygren.org>
To: Patrick McManus <pmcmanus@mozilla.com>
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Subject: Re: http2 opportunistic security negotiation
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The two motivations for OE are to 1) help HTTP/2 deployment for HTTP-scheme
sites by getting around meddlesome middle-boxes, while 2) also providing a
tiny bit of protection against pervasive monitoring.  In both cases, the
closer the traffic is to HTTPS traffic (port 443) the more likely it is to
make it through and work without interference.  Both argue for using port
443 with a handshake where at least the ClientHello is indistinguishable
between a true HTTPS request and an OE HTTP request.

The "cleanest" solution would just be to give OE for HTTP/2 its own ALPN
token such that it is explicitly negotiated where you only send that token
in your ClientHello.  This would help for #1 but is not ideal for #2.  On
the other hand, there are some many attack vectors for #2 that it seems
more worthwhile to make sure #1 works well while raising the bar a little
for #2 where possible.

       Erik


On Tue, Feb 10, 2015 at 5:47 PM, Patrick McManus <pmcmanus@mozilla.com>
wrote:

> I might be under-thinking this one.... but it occurs to me its possible to
> not put the tls version of the site on 443 if there is no https://
> version of the site.. oe doesn't require a particular port number and 443
> seems like the wrong choice if https:// isn't available. too simplistic?
>
> On Thu, Feb 5, 2015 at 10:08 AM, Erik Nygren <erik@nygren.org> wrote:
>
>> While digging further into server-side implementation details of the
>> current opportunistic security draft, we identified a user experience
>> problem.  In particular, for a site that has Virtual Hosts which are
>> HTTP-only (ie, there is no valid certificate for them), there is no way in
>> the current proposal to both support Opportunistic Security  (negotiate h2
>> for http scheme over TLS without a necessarily valid certificate) without
>> also giving users accidentally typing in https URIs a certificate mismatch
>> interstitial they'd be prompted to click through.
>>
>
>
>

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<div dir=3D"ltr"><div>The two motivations for OE are to 1) help HTTP/2 depl=
oyment for HTTP-scheme sites by getting around meddlesome middle-boxes, whi=
le 2) also providing a tiny bit of protection against pervasive monitoring.=
=C2=A0 In both cases, the closer the traffic is to HTTPS traffic (port 443)=
 the more likely it is to make it through and work without interference.=C2=
=A0 Both argue for using port 443 with a handshake where at least the Clien=
tHello is indistinguishable between a true HTTPS request and an OE HTTP req=
uest.<br><br></div><div>The &quot;cleanest&quot; solution would just be to =
give OE for HTTP/2 its own ALPN token such that it is explicitly negotiated=
 where you only send that token in your ClientHello.=C2=A0 This would help =
for #1 but is not ideal for #2.=C2=A0 On the other hand, there are some man=
y attack vectors for #2 that it seems more worthwhile to make sure #1 works=
 well while raising the bar a little for #2 where possible.<br></div><div><=
br></div>=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Erik<br><br></div><div class=
=3D"gmail_extra"><br><div class=3D"gmail_quote">On Tue, Feb 10, 2015 at 5:4=
7 PM, Patrick McManus <span dir=3D"ltr">&lt;<a href=3D"mailto:pmcmanus@mozi=
lla.com" target=3D"_blank">pmcmanus@mozilla.com</a>&gt;</span> wrote:<br><b=
lockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px =
#ccc solid;padding-left:1ex"><div dir=3D"ltr">I might be under-thinking thi=
s one.... but it occurs to me its possible to not put the tls version of th=
e site on 443 if there is no https:// version of the site.. oe doesn&#39;t =
require a particular port number and 443 seems like the wrong choice if htt=
ps:// isn&#39;t available. too simplistic?<span class=3D""><br><div><div cl=
ass=3D"gmail_extra"><br><div class=3D"gmail_quote">On Thu, Feb 5, 2015 at 1=
0:08 AM, Erik Nygren <span dir=3D"ltr">&lt;<a href=3D"mailto:erik@nygren.or=
g" target=3D"_blank">erik@nygren.org</a>&gt;</span> wrote:<br><blockquote c=
lass=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px soli=
d rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr"><div><div><div><div><=
div><div><div><div>While digging further into server-side implementation de=
tails of the current opportunistic security draft, we identified a user exp=
erience problem.=C2=A0 In particular, for a site that has Virtual Hosts whi=
ch are HTTP-only (ie, there is no valid certificate for them), there is no =
way in the current proposal to both support Opportunistic Security=C2=A0 (n=
egotiate h2 for http scheme over TLS without a necessarily valid certificat=
e) without also giving users accidentally typing in https URIs a certificat=
e mismatch interstitial they&#39;d be prompted to click through.<br></div><=
/div></div></div></div></div></div></div></div></blockquote><div><br>=C2=A0=
</div></div></div></div></span></div>
</blockquote></div><br></div>

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