bsterne wrote:
> I think that CSP should be considered part of the browser security
> model.  Mike and others have made the excellent point that there are
> significant costs to bear for a website that wants to start using this
> model: policy development as well as migrating inline scripts to
> external script files.  Websites will not be willing to pay this cost
> if user agents are not strongly committed to enforcing the policies.
> We won't be able to make security guarantees like "XSS will never
> happen on your site", but we can provide smaller guarantees like
> "inline script will not execute in this page if the CSP header is
> sent".

I completely agree that we should make these guarantees, in the sense
that if that doesn't work, it's a bug :-) That's not the sort of
guarantee I'm objecting to. The sort I'm objecting to is "you don't have
to validate and escape user input properly because even if you let a
<script> tag through accidentally, CSP will catch it and save you".

Some understandings of "CSP being strongly part of the browser security
model" would have us making such guarantees. And I think they would be a
mistake. If "CSP being strongly part of the browser security model" just
means "we guarantee that it does what it says on the tin" then I have no
problem with it :-) My reduced commitment to guarantees was not designed
as an ass-covering measure for shoddy coding ;-)

Gerv
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