Re: IE8 img tag HiJacking

[T Biehn <tbiehn () gmail com>]

It could be used as a technique for defeating the login images used as
"two-factor-authentication" by some online services.
The application of using filesize to fingerprint an image is somewhat novel.
This is a decidedly 'old' vector, though.

-Travis

2010/4/21 Владимир Воронцов <vladimir.vorontsov () onsec ru>

> Hello Full disclosure!
>
> Once again, unwinding theme HiJacking found a fun way to get the very
> least information about the target resource when the user is located at the
> attacker.
>
> Already crocked <img> tag opens new opportunities using the method
> fileSize, described here: http://msdn.microsoft.com/en-us/library/ms533752
> (v = VS.85). Aspx
>
> Consider a simple example - a Web application after authentication
> provides some sort of picture for the user, for example:
>
> http://example.com/getImage.php?image=myAvatar
>
> The attacker, knowing this can create a page to read:
>
> <img id="onsec" src="http://example.com/getImage.php?image=myAvatar";>
>
> <input type="button" onclick="if (onsec.fileSize> 0) (alert ('authorized
> on example.com') else (alert ('not authorized on example.com')}">
>
> Thus, the attacker learns the simplest case, whether the target user
> access to example.com.
>
> Continuing the theme, I want to note that in some cases, can obtain
> additional information from the very values of the size of the picture. It
> can be any logical information Web applications, say, the same script can
> show administrators a picture of the same size, and users - of another.
> Thus, we obtain the user rights. And so on.
>
> I'd like to return the size of the method is not only "valid" images, but
> also HTML pages, JSON, etc. But, unfortunately, does not work. Maybe, of
> course, there are exceptions, call to investigate the matter.
>
> I have some thoughts on the study of vector images in XML format, because
> HTML is often valid XML, and then ...
>
> Check for the test version IE9, but he did not support SVG inside tag
> <img>, but only as a separate tag.
>
> Works in IE8, in Opera 10.52 does not work on check writing, if not
> difficult.
>
> Original at russian language: http://oxod.ru/?p=113
>
> --
> Best regards,
> Vladimir Vorontsov
> ONsec security expert
>
> _______________________________________________
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