W3C home > Mailing lists > Public > public-webappsec@w3.org > February 2015

Entry Point Regulation vs Simpler Solutions (was Re: WebAppSec re-charter status)

From: Brian Smith <brian@briansmith.org>
Date: Thu, 12 Feb 2015 12:53:03 -0800
Message-ID: <CAFewVt4xTZT8jM8AGXcnyFRov4c9g6=hr-bFhDmEy8DUojLffw@mail.gmail.com>
To: David Ross <drx@google.com>
Cc: Devdatta Akhawe <dev.akhawe@gmail.com>, Deian Stefan <deian@cs.stanford.edu>, Martin Thomson <martin.thomson@gmail.com>, Brad Hill <hillbrad@gmail.com>, Jeffrey Yasskin <jyasskin@google.com>, Mike West <mkwst@google.com>, Wendy Seltzer <wseltzer@w3.org>, Dan Veditz <dveditz@mozilla.com>, Mounir Lamouri <mlamouri@google.com>, David Baron <dbaron@dbaron.org>, Anne van Kesteren <annevk@annevk.nl>, "public-webappsec@w3.org" <public-webappsec@w3.org>
David Ross <drx@google.com> wrote:
> That being said, I think the criticism is a bit unfair.  EPR is an opt-in
> feature with an intended audience largely separate from those who might wish
> to prevent deep linking on their web sites.

As Anne noted, the concerns about the *unintended* abuse of EPR, not
the use by the intended audience.

> EPR helps enable the web platform to support scenarios with very stringent
> security requirements.  For example, XSS or XSRF is an unacceptable failure
> mode for sensitive applications.

To what extent is CSP not solving the defense-in-depth issue
sufficiently for XSS? It seems to me that with or without EPR, if
there are serious deficiencies in CSP, we need to improve it.

Similarly, it looks like the idea of improved origin restrictions
cookies as defense-in-depth for CSRF has a lot of support from Google
[1][2] and Mozilla [3]. Again, it seems with or without EPR, we need
such independent improvements to CSRF protection. What limitations are
there to those proposals that would make them insufficient
defense-in-depth for CSRF compared to EPR?

It seems like the existing/simpler mechanisms I cited are less open to
abuse that would reduce browser users' agency, and so they seem
preferable to me, if they offer the same level of benefit as EPR,
unless there are other significant benefits to EPR that I'm


[1] https://mikewest.github.io/internetdrafts/first-party-cookies/draft-west-first-party-cookies-00.html
[2] https://mikewest.github.io/internetdrafts/origin-cookies/draft-west-origin-cookies-00.html
[3] https://github.com/mozmark/SameDomain-cookies/blob/master/samedomain.txt

>  (Eg: Administrative consoles)  Authors of
> these sensitive applications sometimes favor implementation as a legacy
> platform app, a mobile app, or even a command line app over the web app
> platform simply because of this security consideration.  I believe it's
> important to provide the _option_ for developers to implement EPR to better
> meet their security requirements.
> Dave
> On Mon, Feb 9, 2015 at 8:48 AM, Devdatta Akhawe <dev.akhawe@gmail.com>
> wrote:
>> > If I am not mistaken what you are proposing here is your work on DCS
>> > [2]. I like DCS, but this is a different system.  I think that web apps
>> > implementing the enforcement logic, while useful for more complex
>> > policies, is more difficult than associating a label with postMessages
>> Forgive me if I gave that impression. That was not my intention. I
>> actually think the ideas proposed in COWL are definitely what we want:
>> confinement for things like ads, third-party widgets without the heavy
>> cost of doing isolation via iframes. I think that was the general
>> motivation discussed at TPAC too, although maybe I am forgetting
>> something. So, for example, I am definitely in favor of something like
>> the workers in the proposal.
>> My only concern is whether or not we want to make "specify and
>> implement DC labels on the web patform" a part of the deliverable. It
>> seems you definitely want it to be part of the deliverable---but in
>> that case , I think the text should say this explicitly. I definitely
>> did not get that when I first read the text and we would have saved a
>> lot of email :)
>> cheers
>> Dev
>> > as a way of expressing security concern.  (Because of labels, the COWL
>> > confinement enforcement mechanism also piggy-backs on CSP.) But, more
>> > importantly, DCS cannot safely allow for a number of use cases that COWL
>> > does. For example, we would not be able to build mashups wherein the
>> > parties are mutually distrusting. This is because an iframe (or worker)
>> > cannot impose any restrictions on its parent and there is no way to
>> > impose confinement restrictions on cross-origin contexts.
>> >
>> > DCS and COWL have some similarities, but also have different goals, so
>> > it is natural that the approaches differ and excell at different things.
>> > I think they may even be complimentary.  But, if it's okay with you,
>> > Dev, I propose discussing DCS separately to avoid confusion.
>> >
>> > Thanks,
>> > Deian
>> >
>> > [1] http://www.scs.stanford.edu/~deian/pubs/stefan:2011:dclabels.pdf
>> > [2] http://devd.me/papers/dcs-esorics.pdf
Received on Thursday, 12 February 2015 20:53:31 UTC

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