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Flash Vulnerability Found, Adobe Says No Fix Forthcoming
An anonymous reader writes "Security researchers at Foreground Security have found an issue with Adobe Flash. Any site that allows files to be uploaded could be vulnerable to this issue (whether they serve Flash or not!). Adobe has said that no easy fix exists and no patch is forthcoming. Adobe puts the responsibility on the website administrators themselves to fix this problem, but they themselves seem to be vulnerable to these problems. Every user with Flash installed is vulnerable to this new type of attack and — until IT administrators fix their sites — will continue to be."
Adobe's answer is just the greatest kind of cop out. "Websites just need to make sure to check all uploaded material". But that's obviously never going to happen -- fuck they can't even do that themselves! End users can't rely on every single website out there to be vigilant at all times and never accept an upload of a flash file.
If this is really unfixable in the flash plugin, then maybe it's because your security model is fucking broken and it's time to throw this piece of shit away?
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Entranced by anime since late summer 2001 and loving it ^_^
This is ridiculous. If a web site lets you upload a JavaScript file and then serves it back to you as part of a request, it would be crazy. All that has happened here is that people have worked out that doing the same thing with a Flash file is equally bad.
Of course there's no easy fix apart from web sites being sensible in what they upload -- just like anyone with a clue doesn't let users submit comments with tags in them.
The vulnerability is not new at all. It's been known for probably coupe of years now. If a site accepts file uploads, in some cases even if simply displays user submitted data like *comments*, a malicious user may upload content that contains a policy XML snippet (the resulting file doesn't have to start with the snippet as well due to some specific of how the content is parsed). Flash can be pointed to that snippet and it will blindly accept it as the security policy for that domain/folder.
The security implications are that even if the site doesn't use Flash itself, a user opening a third party site with Flash could read from the site with the faulty policy.
Say Facebook is vulnerable to this problem (likely it is), and you're logged in. Opening another site will allow Flash on that third party site to read your Facebook details, as it has access to anything you do.
This problem was introduced sometimes Flash 7-8 (I forget) when an ability was added for Flash to read policy files from a custom URL. Prios to that, the only valid location was www.example.com/crossdomain.xml, which is, of course far simpler to lock down and secure. The bottom line is, they can fix this in a number of ways, but not in a backwards compatible manner. For the moment they simply seems to have their bets that people don't care enough about this problem to warrant the effort.
It doesn't matter, and unsigned, obviously.
Comment removed based on user account deletion
I'm glad that 64-bit Firefox doesn't have a flash plugin.
Science : Proprietary , Knowledge : Open Source
Instead, Arkin added, Adobe has tried to get the word out to Web application designers and site administrators about the danger of allowing users to upload content. "Sites should not allow user uploads to a trusted domain," Arkin argued. "The real issue here is that developers should be cautious about using techniques that can be misused maliciously. In general, this is a general challenge in managing active content."
Arkin is from Adobe. And he's seriously saying that in order to "fix" this, web site owners must simply disallow users from uploading files. Period. (Not through Flash, but all file uploading .) That's a spectacular answer.
On the other hand... I kind of understand where he's comign from. If you let your users upload content unchecked, and serve that content up, you are potentially giving some level of access to client machines. In this case, it seems somewhat minimal? I'm not familiar with actionscript, but you don't get free reign to the user's machien do you? Only content specifically store under the domain of the owning server, in the context of Flash?
I have just read the article. The problem seems to be with sites who allow flash object to be uploaded, then served to other people using the site. Of course, this is just stupid anyway. If I allow you to upload a flash object to my site, I should sanitise it before I allow my server to give it to anyone. The example they give is an animated avatar, but that is poor example as they should be restricted to animated gifs anyway.
This is just more FUD. ActionScript is a very powerful language, and so server admins should only allow flash files they trust to be served up form websites they maintain. To my mind that is just common sense. The only alternative would be for Adobe to cripple Flash beyond belief so it was only useful for a small percentage of what it is currently used for.
I dont read
This is the same kind of logic Microsoft used with security in the 9.x kernel. Putting the impetus on third parties to behave and not take advantage of this is nuts! Are they not the least bit familiar with malware or anything else of the like? Bad Adobe, bad!
In this case, it was used to log the user into the attacker's account, which contained the malicious SWF uploaded as an attachment. If the user then logged into gmail (the video uses a registration email to prompt the user to do so), his account would be compromised.
In Gmail's case, there are other privacy consequences to the login CSRF. For example, if the user is logged into an account that I have access to, I can actually view his google search history.
"The cup is in turn designed for holding hot or cold liquids, and has an open rim and closed base." --US Patent #5425497
I've been worried about Flash security for a long time now. I'd like to point out three features of Flash that bother me.
First, Flash allows a web application to paste data to the clipboard even if the browser itself forbids this. Of the major browsers, only IE allows applications to directly set the clipboard content.
Second, Flash has an XMLHttpRequest equivalent with a lax security policy. Cross-domain retrieval is controlled by an XML control file listing permissible origins.
Finally, Flash has its own cookie system. These Flash cookies are hidden from the user, and require special tools to remove.
These features are secure in themselves, but are enablers: they give attackers the means to exploit other vulnerabilities.
Unfortunately, this cavalier attitude fits Adobe's business model. Lax security is as much a feature of Flash as its vector graphics. Flash allows web developers "get shit done" with no regard for the security of the web ecosystem as a whole. Web developers then come to rely on Flash, which increases the adoption of Flash Player among users, which in turn increases the value of Adobe's authoring tools. Being insecure is lucrative, up to the point that the vulnerabilities become so egregious that users disable Flash.
On the other hand, browser vendors seem to take a mostly-conservative approach to security (don't laugh yet): consider XMLHttpRequest: sure, its same-origin restriction on the target URL is inconvenient, and the restriction might have been loosened while remaining secure. But this same prudent restriction has also prevented many attacks. Browser vendors have the right incentives because users have a realistic choice of browsers. Flash is an all-or-nothing affair.
I wish I had an answer. Hopefully, HTML 5 will become widely supported enough that websites won't feel compelled to use Flash for graphics and storage, and eventually Flash's market penetration will sink below the point that web developers can consider it a viable way to circumvent browser security.
To disable Flash and Shockwave in my main browser.
It's remarkable how nice it is to surf the modern web without them ... ads (that I don't already block) have small fonts and easy-to-ignore plain text, I can listen to music and surf, and not have some crappy video start playing in a background window ... I'm loving it.
If I need Flash, I'll just surf with one of the alternate browsers for a page or three. The rest of the time ... bliss. Sheer bliss ...
On the other hand, the more arcane the attack, the less likely it is to get fixed, and so the more websites remain vulnerable. The end result is that an attacker well-versed in a variety of obscure attacks can find a way into just about everything.
This one, though, does affect an awful lot of sites- it's rare to find a site that doesn't allow users to upload some kind of file. The impression I get is that image uploads may be more or less simple to validate, but most other filetypes aren't.
"The cup is in turn designed for holding hot or cold liquids, and has an open rim and closed base." --US Patent #5425497
Slashdot really needs an appallingly ignorant mod. Or maybe just an RTFA.
I get the gist of the article - user flash content shouldn't be served from the same domain as your app.
But here's the thing - I know many, many people who run webservers just for the hell of it, and give free accounts to friends and such (the ubiquitous public_html subdirectory for a user, aka ~ ). So let's say the webserver at example.com has something like a secure login for webmail access or other stuff on there as well. It's not terribly vital, but it's still in place. One of the users maliciously uploads one of these flash files, has another person run it, and then that person logs in to another section of example.com - can the attacker then grab that data? It seems to be the case.
So what the hell are people in this situation supposed to do? Is the only solution to move all that user content to a subdomain as well? Seriously? At least javascript is confined mostly to a single PAGE - please tell me I'm reading this incorrectly.
good thing firefox will automatically block this plug in for me, to keep me safe. that's what they do right?
If the malicious content is served by the site, then even using a whitelist ala Flashblock won't work, will it? That's pretty scary.