Tuesday, September 27, 2011

BEAST smothered by security blanket

7.0 was converted to final this morning and I'm pulling down 8 beta 1 for initial conversion as we speak. This will require more work than 7 because Mozilla committed a number of 10.5/10.6-specific widget changes which will need to be rewritten for 10.4, but I'm pretty confident this is possible. You'll be the first to know.

A number of people have privately asked me whether TenFourFox is susceptible to the BEAST SSL attack revealed over the weekend. This rather startling hack was able to decrypt a Paypal cookie sent over SSL, allowing the attacker to assume the identity of the logged-in user. It should come as no surprise that 1) the Mozilla security team has been discussing this (along with representatives from Google, which uses the Netscape-originated Network Security Services library also) for several months, and 2) as shipped, TenFourFox is not vulnerable. Notice that I said "as shipped." The exploit demonstrated by Rizzo and Duong used a Java applet to do the server thrashing needed to get the key out, and TenFourFox disables all plugins including the Java Embedding Plugin, so the applet cannot run. It may be possible to do something similar in Flash (though such code has not yet? surfaced), but obviously this doesn't ship enabled in TenFourFox either, and the version of WebSockets in Firefox 7 and TenFourFox 7 cannot be used to trigger this exploit.

Even with plugins, Java and/or other suitable footholds available, the SSL flaw in question is not trivial to exploit: not impossibly hard nor prohibitively expensive, but neither is it simple, quick or easy. An attacker must have control of the network the victim is using (such as a compromised or open wireless link), and must be fast enough to spy on the connection and manipulate the victim's browser to try combinations on the server the victim is accessing before the session terminates. Under the optimal conditions of the demonstration the "victim" was pwned in about two minutes; real world assaults will undoubtedly require significantly more time. It is also possible for servers to immunize themselves against the attack by negotiating ciphers that are not vulnerable to the flaw Rizzo and Duong are taking advantage of; RC4/ARC4 is one such cipher and Google is using it already on its services.

The best solution is to leave TLS 1.0 behind, but for a variety of reasons this has yet to happen, and perhaps this will be the impetus to change to a safer, later TLS version. Once a final fix is decided upon for NSS, there may or may not be a 7 chemspill; we'll follow Mozilla's lead here. A similar fix will be included in Classilla, which is technically vulnerable but hard to exploit because OS 9's MRJ is mercifully too old and Flash 7 does not support sockets of the type required.


  1. When I want to promote TFF 7 and link http://www.floodgap.com/software/tenfourfox/ in Facebook, it still says

    "TenFourFox: A fork of Mozilla Firefox 4 and 5 for the Power Macintosh and Mac OS X Tiger PowerPC".

  2. It seemed to pull ok for me on http://jnorthr.wordpress.com/2011/09/27/firefox-7-0-tenfourfox-for-apple-mac-os-g3g4-and-g5s/ as Firefox 7.0
    perhaps the facebook link is stale

  3. Pour l'avoir en fran├žais :

  4. I am not sure if this is the right place to ask this question (also put this question in the Release Notes comments) but here goes. I am not updating TFF after version 5.0 because (I am not of the computer generation, not much of a techie), I rely on my plugins to play online media of all types. If I want to experiment with TFF 7, is there anyway I can safely (always want version 5 available!!) run the 2 versions separately, put 2 icons on my desktop, just choose the version I want to use for particular situations. Thanks, Ken.

  5. Just got the answer myself. After unpacking TFF 7, I changed the name of the icon to TenFourFox7450 to TenFourFox7450(7). Now both versions 5 + 7 are in my Applications folder. I put aliases of both on my desktop, works like a charm. Ken.

  6. That's pretty much what I do for testing, yes.

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