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Re: [blink-dev] Re: Proposal: Marking HTTP As Non-Secure

From: Austin William Wright <aaa@bzfx.net>
Date: Fri, 26 Dec 2014 23:01:54 -0700
Message-ID: <CANkuk-V7cnV3T+Ldsg8YsM5QUbM4=816PJ+crNiFy50s0KZv+Q@mail.gmail.com>
To: noloader@gmail.com
Cc: "dev-security@lists.mozilla.org" <dev-security@lists.mozilla.org>, security-dev <security-dev@chromium.org>, "public-webappsec@w3.org" <public-webappsec@w3.org>, blink-dev <blink-dev@chromium.org>
On Fri, Dec 26, 2014 at 7:43 PM, Jeffrey Walton <noloader@gmail.com> wrote:

> > If we want to talk about the perspective of servers, the server has
> options
> > to demand a secure connection too; it simply has to deny plaintext
> requests
> > ...
>
> Actually, no. Middleware boxes and a class of active attackers can do
> whatever they want.
>

Ah yes, I wasn't even considering the class of active attacks, where *any*
attempt to go over cleartext would be vulnerable. Thanks for pointing this
out!

(I was careful to specify that accepting the TCP connection, for the
purposes of redirecting, could leak information to eavesdroppers.)


>
> The control to stop most of the intercept related attacks - public key
> pinning - was watered down by the committee members to the point that
> the attacker effectively controls the pinset. (Here, I'm making no
> differentiation between the "good" bad guys and the "bad" bad guys
> because its nearly impossible to differentiate between them).
>
> That is, the standard could have provided policy and the site could
> have sent a policy that governed the pinset. The site could have
> allowed an override or denied an override. But it was decided all
> users must be subjected to the interception, so the policy elements
> were not provided.
>
> So how's that for strategy: the user does not get a choice in their
> secure connection and the site does not get a choice in its secure
> connection. Rather, some unrelated externality makes the choice.
>

I share your concerns, and more: Public Key Pinning (and Strict Transport
Security, for that matter) is awfully specific to HTTP, even though it has
nothing to do with HTTP at all. The proper place to put this information is
in DNS records. This has worked reasonably well for Email; or at least I
don't see anyone proposing we query SMTP servers for relevant security
metadata. So why do this for HTTP? (If one wants to answer that properly
stopping forged headers is less important than stopping plaintext cat
pictures, color me surprised; if it's because it's a better alternative
than unencrypted DNS records for those lacking DNSSEC, that's a better
answer, but it's still relegates HPKP and HSTS to the realm of "stopgap
measure".)

Austin.


>
> Jeff
>
> On Fri, Dec 26, 2014 at 8:33 PM, Austin William Wright <aaa@bzfx.net>
> wrote:
> >
> > On Wed, Dec 24, 2014 at 3:43 PM, Alex Russell <slightlyoff@google.com>
> > wrote:
> >> ...
> >>
> >> No, the request for a resource means something. Security is about the
> >> quality of service in delivering said thing.
> >
> > Specifically, I refer to privacy and authentication (which seems to be
> what
> > "security" means here). There's many components to security, and they're
> not
> > all going to be desired at the same level for every request, sometimes
> even
> > at odds with each other. Deniability is a particularly expensive one to
> > implement, often at significant monetary and performance cost to the
> user.
> > Deniability is simply not implemented by any website (or more accurately,
> > any authority) indexed by the major search engines.
> >
> > It's difficult to claim that deniability, though, is about "quality of
> > service", but it is nonetheless considered something _very_ important by
> > Tor, and by users of it.
> >
> >>
> >> > HTTP could mean, simply, "I don't care about security".
> >>
> >> Then user agents should be free to act on behalf of users to write off
> >> correspondents who do not value the user enough to protect the message
> in
> >> transit.
> >>
> >> You're making claims about what UA's must do from the perspective of
> >> servers; this is a clear agency problem misunderstanding.
> >>
> >> We're the user's agent, not the publisher's.
> >
> > When a user navigates to an https:// resource, or hits the checkbox for
> > STARTTLS, or selects "Require encryption" from a drop-down, they, the
> user,
> > are *demanding* a secure connection (for someone's definition of secure;
> > traditionally this means privacy and authentication but need not include
> > deniability).
> >
> > If we want to talk about the perspective of servers, the server has
> options
> > to demand a secure connection too; it simply has to deny plaintext
> requests
> > (it could redirect, but this risks the user-agent sending sensitive
> > information including request-uri that'll just be ignored), and TLS can
> > specifically ask for or require a client TLS certificate for
> authentication.
> >
> > The user-agent works for the user, not the other way around. Letting a
> > user-agent intervene in the case of a plaintext request is imposing a
> value
> > on the user: It prioritizes privacy over "DO NOT BREAK USERSPACE!" which
> is
> > not *necessarily* true.
> >
> > If TLS were free or very cheap to implement, however, this would be a
> > non-issue. Hence my treatment of ways to do this.
> >
> > Even if the http-as-non-secure proposal fully worked; it still increases
> the
> > cost of publishing content and barriers to entry. I recall Tim
> Berners-Lee
> > recollecting that requiring users mint a long-lived URI was concerning
> cost;
> > but there was no other way to design a decentralized Web. (In the end,
> the
> > biggest barrier to entry has been acquisition of a domain name and
> hosting.)
> >
> > Of course, if efficiency and security are at odds, then we prefer
> security.
> > However, I see making TLS implementation cheaper as a viable alternative
> to
> > this proposal, and so is far more appealing.
> >>
> >> > A TLS failure means "Security is _required_ by the other party, but
> >> > couldn't be set up and verified. Abort! Abort!"
> >> >
> >> > Purporting that plaintext and HTTPS failure is the same would be
> >> > conditioning users to be less worried about HTTPS failures, where
> there's a
> >> > known _requirement_ for confidentiality.
> >>
> >> The UA could develop different (but also scary) UI for these conditions.
> >
> > I am specifically referring to the part of the proposal that, in the long
> > term, specifies no UI difference between plaintext and failed-TLS.
> >
> > Would you care to make an alternate proposal with this change?
> >>
> >> Regardless, we have done a poor job communicating the effective system
> >> model (that content is not tamper-evidentwhen served over HTTP). Steps
> to
> >> make this clearer aren't the same thing as throwing all distinction
> >> overboard.
> >>
> >> > There may be some value in saying "as with many network requests,
> >> > request/submission is being sent in the clear. Anyone on your network
> will
> >> > be able to read this!". But big scary warnings are most certainly
> bad. No
> >> > matter what, before I claim anything for sure, I would like to see a
> >> > double-blind study, and not change for the sake of change.
> >>
> >> This sort of argument might have worked in '12. Apologies, but you're
> >> dreadfully late.
> >
> > I'm afraid snark wasn't my first language, so you'll have to refresh my
> > memory: what are you referring to?
> >
> > Earlier in my message, I touched on the danger of users dismissing
> warnings
> > for their e.g. bank, because users become dismissive of "insecure
> > connection" warnings found elsewhere.
> >
> > Now, we might have HSTS (for my bank example), but at that point we're no
> > longer talking about two tiers of security, but three
> (insecure-bypassable,
> > insecure-nonbypassable, secure), which is precisely what the proposal is
> > advocating moving _away_ from (or, the proposal is not very clear on this
> > point, and a clarification in its text would be necessary).
> >> ...
>
Received on Saturday, 27 December 2014 06:02:23 UTC

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