Re: [http-state] Ticket 6: host-only cookies

Adam Barth <ietf@adambarth.com> Tue, 02 February 2010 06:59 UTC

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From: Adam Barth <ietf@adambarth.com>
Date: Mon, 1 Feb 2010 23:00:07 -0800
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To: Blake Frantz <bfrantz@cisecurity.org>
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Subject: Re: [http-state] Ticket 6: host-only cookies
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I've added the following text to the server section, as recommend by
Dan Winship:

              <t>WARNING: Some legacy user agents treat an absent Domain
              attribute as if the Domain attribute were present and contained
              the current host name. For example, if example.com returns a
              Set-Cookie header without a Domain attribute, these user agents
              will send the cookie to www.example.com.</t>

Adam


On Mon, Feb 1, 2010 at 8:32 AM, Blake Frantz <bfrantz@cisecurity.org> wrote:
> I support Dan's approach.
>
> B
> -----Original Message-----
> From: http-state-bounces@ietf.org [mailto:http-state-bounces@ietf.org] On Behalf Of Dan Winship
> Sent: Friday, January 22, 2010 6:38 AM
> To: Adam Barth
> Cc: http-state
> Subject: Re: [http-state] Ticket 6: host-only cookies
>
> On 01/22/2010 03:50 AM, Adam Barth wrote:
>> 1) Specify host-only cookies to match Firefox, Chrome, Safari, and
>> Opera.  This is best for security, and I think there's a good chance
>> that IE will adopt host-only cookies in future, but I don't have any
>> citable evidence for this belief.  (The draft currently matches this
>> proposal.)
>
> The other argument in favor of this is that the host-only cookie rule
> was part of the original Netscape spec, so this isn't just a case of
> unspecified behavior where some browsers do one thing and others do
> another, or of clients being-liberal-in-what-they-accept to work around
> server problems. IE is just doing it wrong.
>
>> 3) Allow both behaviors.  This alternative is the worst for security
>> because it makes the cookie protocol less predictable.  When all the
>> other browsers agree on a behavior that's better than the IE behavior,
>> I think we can require the non-IE behavior.
>
> Well... allowing both behaviors doesn't *make* the protocol less
> predictable, because the protocol already *is* less predictable, and
> will continue to be for several years at least, regardless of what we
> say. So we should document the unpredictability, so that server authors
> will know that they have to take steps to protect themselves against
> unintended cookie leakage in some cases.
>
> So my vote is, require clients to implement host-only cookies (as the
> Netscape spec did), but note in the corresponding server-side section
> that some clients don't do this, with some discussion of the security
> issues.
>
> -- Dan
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