W3C home > Mailing lists > Public > public-web-security@w3.org > January 2011

Re: XSS mitigation in browsers

From: <sird@rckc.at>
Date: Wed, 19 Jan 2011 17:20:43 -0600
Message-ID: <AANLkTi=BvVJcWYzVTVkBTXXNO5wVEudgQfL0eNpQHcSQ@mail.gmail.com>
To: Adam Barth <w3c@adambarth.com>
Cc: public-web-security@w3.org, Sid Stamm <sid@mozilla.com>, Brandon Sterne <bsterne@mozilla.com>
Oh btw, the way it works is by parsing HTML by itself.

If the DOM provided this events, then that would avoid the requirement
of parsing the DOM :)

-- Eduardo

On Wed, Jan 19, 2011 at 5:19 PM, sird@rckc.at <sird@rckc.at> wrote:
> Hi Adam!
> I did a script that does this a few years ago:
> http://secinn.appspot.com/pstzine/read?issue=4&articleid=8
> Mod Security is using it now as a demo, and there are a few sessions
> about it in OWASP Summit in Portugal next month.
> Greetings!!
> -- Eduardo
> On Wed, Jan 19, 2011 at 5:17 PM, Adam Barth <w3c@adambarth.com> wrote:
>> On Wed, Jan 19, 2011 at 2:58 PM, sird@rckc.at <sird@rckc.at> wrote:
>>> Couldn't the same be done with simply a script element? No need for
>>> webkit (browser) support.
>> I believe you can block external script loads using the beforeload
>> event, but I don't know how you would be able to block inline scripts
>> or inline event handlers purely in script.  Another approach, of
>> course, is to add "before" events for these operations as well to
>> allow for programatic control.
>> Adam
>>> On Wed, Jan 19, 2011 at 4:42 PM, Adam Barth <w3c@adambarth.com> wrote:
>>>> Hi public-web-security,
>>>> I'm not sure if this the right forum for discussing new browser
>>>> features that help mitigate cross-site scripting.  If not, please feel
>>>> free to point me to a better forum.
>>>> As I'm sure many of you are aware, various folks from Mozilla have
>>>> proposed Content Security Policies
>>>> <https://wiki.mozilla.org/Security/CSP> as a way of improving the
>>>> security of web pages by including a security policy.  I'm interested
>>>> two aspects of CSP:
>>>> 1) Cross-site scripting mitigation
>>>> 2) Notification of policy violations
>>>> The simplest design I could think of that achieves those goals is
>>>> described on this wiki page:
>>>> https://trac.webkit.org/wiki/HTML%20Security%20Policy
>>>> The design is largely inspired by CSP, but different in a few ways:
>>>> 1) Instead of using HTTP headers, the policy is expressed in HTML.  Of
>>>> course, authors will want to place the policy as early as possible in
>>>> their document, so we're using a meta element, which can be placed in
>>>> the head of the document.
>>>> 2) Instead of exposing policy levers for every kind of resource load,
>>>> this proposal only lets the author control the source scripts.  This
>>>> focus on scripts is motivated by wanting to prevent the attacker from
>>>> injecting script into the page.
>>>> 3) Instead of reporting violations to the server via HTTP, this
>>>> proposal simply generates a DOM event in the document.  The author of
>>>> the page can listen for the event and wire it up to whatever analytics
>>>> the author uses for other kinds of events (e.g., mouse clicks).
>>>> Let me know if you have any feedback on this proposal.  In general,
>>>> I'm more interested in feedback that leads to simplification rather
>>>> than feedback that leads to more complexity.
>>>> Thanks!
>>>> Adam
Received on Wednesday, 19 January 2011 23:21:36 UTC

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