Re: [http-state] Browser Behaviors on Cookie Domain and Public Suffix

Zhong Yu <zhong.j.yu@gmail.com> Mon, 25 May 2015 02:01 UTC

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Date: Sun, 24 May 2015 21:01:37 -0500
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From: Zhong Yu <zhong.j.yu@gmail.com>
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Subject: Re: [http-state] Browser Behaviors on Cookie Domain and Public Suffix
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Based on the previous observations and reasonings, I'm going to propose an
Errata for rfc6265. Since the subject is messy and controversial, I'll wait
for some time though. If nobody objects, I'll submit the Errata on Thursday.

I think an errata is needed here because an implementer reading the RFC and
publicsuffix.org may have missed the nuances, and accidentally allowed
super cookies.

Proposed Errata: (technical)

Section 5.3 says:

   If the user agent is configured to reject "public suffixes" and the
domain-attribute is a public suffix:

           If the domain-attribute is identical to the canonicalized
request-host:

              Let the domain-attribute be the empty string.

           Otherwise:

              Ignore the cookie entirely and abort these steps.


It should say:

   If the user agent is configured to reject "public suffixes" and the
domain-attribute is a TLD, or a public suffix, or any parent domain of a
public suffix:

              Ignore the cookie entirely and abort these steps.


Notes:

1. "TLD" is explicitly mentioned, because a TLD may not be a public suffix.

2. "parent of public suffix" is explicitly mentioned, because it may not be
a public suffix.

3. The clause to set domain-attribute="" is removed for simplicity and
interoperability; only Firefox implements it; and it doesn't seem very
useful.

--

Zhong Yu
bayou.io