We don't want to use Microsoft's,
whatever we do, because it promotes their
own borked browser IE9.
On Fri, Jun 3, 2011 at 11:30 AM, Mark Dilley <markwdilley(a)gmail.com> wrote:
<aside from main conversation>
Would it be a good community gesture to join Microsoft in trying to
eradicate IE6?
http://TheIE6Countdown.com
or to not join them and put up a more general banner
http://IE6NoMore.com
and move on?
</aside from main conversation>
On 03Jun2011, at 10:53 AM, Brion Vibber wrote:
On Thu, Jun 2, 2011 at 5:21 PM, Tim Starling
<tstarling(a)wikimedia.org
wrote:
> On 03/06/11 06:56, Brion Vibber wrote:
>> For 1) I'm honestly a bit willing to sacrifice a few IE 6 users at
>> this
>> point; the vendor's dropped support, shipped three major versions, and
is
>> actively campaigning to get the remaining
users to upgrade. :) But I
get
>> protecting, so if we can find a
workaround that's ok.
>
> We can't really do this without sending "Vary: User-Agent", which
> would completely destroy our cache hit ratio. For people who use Squid
> with our X-Vary-Options patch, it would be possible to use a very long
> X-Vary-Options header to single out IE 6 requests, but not everyone
> has that patch.
>
I'm really thinking more along the lines of: if someone's an IE
6-or-below
user they have hundreds of other exploit vectors
staring them in the
face
too, and we can't protect them against many of them -- or ANY of them if
they're visiting other sites than just an up-to-date MediaWiki.
The cost of this fix has been immense; several versions of the fix with
varying levels of disruption on production sites, both for IE 6 users
and
non-IE 6 users, and several weeks of delay on the 1.17.0 release.
I'd be willing to accept a few drive-by downloads for IE 6 users; it's
not
ideal but it's something that their antivirus
tools etc will already be
watching out for, that end-users already get trained to beware of, and
that
will probably *still* be exploitable on other web
sites that they visit
anyway.
The main issue here is that we don't a wide variety of web servers set
> up for testing. We know that Apache lets you detect %2E versus dot via
> $_SERVER['REQUEST_URI'], but we don't know if any other web servers do
> that.
>
> Note that checking for %2E alone is not sufficient, a lot of
> installations (including Wikimedia) have an alias /wiki ->
> /w/index.php which can be used to exploit action=raw.
>
Well that should be fine; as long as we can see the "/wiki?/foo.bat"
then
we
can identify that it doesn't contain an
unencoded dot in the path.
It sounds like simply checking REQUEST_URI when available would
eliminate
a
huge portion of our false positives that affect
real-world situations.
Apache is still the default web server in most situations for most
folks,
and of course runs our own production servers.
>
>> Are there any additional exploit vectors for API output other than
>> HTML
> tags
>> mixed unescaped into JSON?
>
> Yes, all other content types, as I said above.
>
Only as drive-by downloads, or as things that execute without
interaction?
> I think the current solution in trunk, plus the redirect idea that
> I've been discussing with Roan, is our best bet for now, unless
> someone wants to investigate $_SERVER['REQUEST_URI'].
>
*nod* Checking REQUEST_URI is probably the first thing we should do when
it's available.
> If there is an actual problem with ForeignAPIRepo then we can look at
> server-side special cases for it. But r89248 should allow all API
> requests that have a dotless value in their last GET parameter, and a
> quick review of ForeignAPIRepo in 1.16 and trunk indicates that it
> always sends such requests.
>
Yay! That's one less thing to worry about. :D
> Since we're talking about discarded solutions for this, maybe it's
> worth noting that I also investigated using a Content-Disposition
> header. The vulnerability involves an incorrect cache filename, and
> it's possible to override the cache filename using a
> Content-Disposition "filename" parameter. The reason I gave up on it
> is because we already use Content-Disposition for wfStreamFile():
>
> header( "Content-Disposition:
> inline;filename*=utf-8'$wgLanguageCode'" . urlencode( basename( $fname
> ) ) );
>
> IE 6 doesn't understand the charset specification, so it ignores the
> header and goes back to detecting the extension.
>
Good to know.
-- brion
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