Hi Vladimir,
Thanks for your views.
I was carried away because the author used scripts (in a global script tag)
in the PoC of the issue in question which made unconditional recursion
possible.
Without scripts enabled, if iframe's src property is set to itself(?), it is
parsed upto 1 level (i.e. not recursed). Hence it doesn't affect or DoS the
latest browsers (the best I can say...).
A few other points:
1. if a links/ads or any other content-syndication provider allow unverified
javascript to be served, DoS would be the least of the concern (read: it’s
the breeding ground of XSS exploits)
2. I more than agree that an issue to be classified as a security
vulnerability if a combination of tags/properties/scripts causes or is
capable of causing malice in any form while conforming to the standards
(which isn't the case here).
3. Just to reiterate my earlier post, DoS is more of an annoyance than
malice. If the issue noted in this context DoS by a form of unconditional
recursion (or infinite loop) to create 'out of memory' or stack overflow
sortof situation (though modern uri handlers handle it gracefully) but
requires a task kill operation on the script engine's host (the browser in
this context).
Sadly, there're too many known unknowns to the #2 above which involves the
support of non-standard techniques like Anti-Phishing Working
Group/SmartScreen filter etc which doesn't attempt to or can be absolutely
100% fool-proof...
Best Regards,
w
PS: Lets put IE6 out of context, I'm not sure why it is still brought up or
why it's still used, because it’s a browser from the times when the first
ancestor of Firefox (Phoenix) didn't exist. Yes, its that ancient! :)
--------------------------------------------------
From: "Vladimir '3APA3A' Dubrovin" <3APA3A@xxxxxxxxxxxxxxxx>
Sent: Saturday, May 29, 2010 2:05 AM
To: "John Smith" <at-x@xxxxxxxx>
Cc: "MustLive" <mustlive@xxxxxxxxxxxxxxxxxx>; "Susan Bradley"
<sbradcpa@xxxxxxxxxxx>; <bugtraq@xxxxxxxxxxxxxxxxx>
Subject: Re[4]: DoS vulnerabilities in Firefox, Internet Explorer, Chrome,
Opera and other browsers
Dear John Smith,
In general case we are discussing, DoS may be caused by e.g. some
combination of allowed tags/properties or by malformed image.
As it was pointed by author, this attack may be performed with
scripting disabled (with [iframe src=]). That's why e-mail vector may
be significant.
--Friday, May 28, 2010, 11:55:28 PM, you wrote to 3APA3A@xxxxxxxxxxxxxxxx:
JS> Point taken. But that'd be a non-issue on the browser's end as much as
JS> site's that is allowing the rogue scripts (or malformed ads, as per
your
JS> example).
JS> The fork of this mail thread clearly explains what I'm talking about.
The
JS> issue noted there is a simple DoS attack which every programming
language
JS> and platform is vulnerable too. Its called the "infinite loop". It is
not a
JS> 'security vulnerability' by itself and is completely agnostic of the
uri
JS> handler (try http or anything instead of nntp).
JS> Here's the simplified JS version of it (lets call it the Universal
DoS --
JS> yes, it'd work for every browser on the planet that can execute JS) -
JS> <script>
JS> while(1)alert('hello world');
JS> </script>
JS> Done!
JS> Workaround:
JS> None very intuitive. Maybe allow the user to terminate the script at
every
JS> iteration? specific time period? etc...
JS> --------------------------------------------------
JS> From: "Vladimir '3APA3A' Dubrovin" <3APA3A@xxxxxxxxxxxxxxxx>
JS> Sent: Friday, May 28, 2010 11:47 PM
JS> To: "John Smith" <at-x@xxxxxxxx>
JS> Cc: "MustLive" <mustlive@xxxxxxxxxxxxxxxxxx>; "Susan Bradley"
JS> <sbradcpa@xxxxxxxxxxx>; <bugtraq@xxxxxxxxxxxxxxxxx>
JS> Subject: Re[2]: DoS vulnerabilities in Firefox, Internet Explorer,
Chrome,
JS> Opera and other browsers
Dear John Smith,
Actually, browser DoS may be quite serious vulnerability, depending on
nature of DoS. Think about e.g. banner or content exchange network,
social networks, web boards, etc where browser vulnerability may be
used against site or page because it will harm any visitors of this
site or page.
In case of this very vulnerability, most serious impact may be from
e-mail vector.
--Friday, May 28, 2010, 7:07:50 PM, you wrote to
mustlive@xxxxxxxxxxxxxxxxxx:
JS> Just a few cents - DoS in webbrowsers doesn't fall under the
category
of
JS> "vulnerabilities" rather more of "annoyances". Although I don't deny
the
JS> fact that certain DoS attacks *may lead* or *may serve as hints* to
other
JS> more serious exploits, but that's a different topic and with ASLR in
the
JS> scene, a very grey area of discussion.
--
Skype: Vladimir.Dubrovin
~/ZARAZA http://securityvulns.com/
Стреляя во второй раз, он искалечил постороннего. Посторонним был я.
(Твен)
--
Skype: Vladimir.Dubrovin
~/ZARAZA http://securityvulns.com/
Машина оказалась способной к единственному действию,
а именно умножению 2x2, да и то при этом ошибаясь. (Лем)
