Tuesday, October 14, 2014

Poodles are fine dogs. SSLv3 is not a fine protocol.

For the hat trick, the security researchers who brought you BEAST and CRIME now introduce POODLE, the "Padding Oracle On Downgraded Legacy Encryption" attack. The attack allows an SSLv3 connection to be gradually broken down using a dramatically faster method that coughs up a byte of the session cookie on average one out of 256 tries. Ironically, because the demonstrated attack vector is JavaScript, our JIT makes us more vulnerable to this because we run JavaScript faster.

There is no fixing SSLv3 against this -- it's a fundamental flaw in the protocol that can't be worked around, and while previous weaknesses were mitigated somewhat with cipher changes there's no easy way out this time. Most browser vendors, including Mozilla, are taking this as the last straw and ending support for SSLv3, especially since TLS v1 and its successors have been around so long. Even Classilla supports TLS v1.

What will happen is that starting in Firefox 34, all connections must use TLS v1 or higher, giving servers a six-week cycle to do any necessary upgrades. We will follow suit: if Mozilla does not do this first, we will also set TenFourFox on the corresponding ESR release (31.3) to do the same. If you want to do this early, go into about:config and set security.tls.version.min to 1; if this causes problems with HTTPS sites you visit, switch back and tell them to get with it. Classilla users are advised to disable SSLv2 and SSLv3 in the Preferences window, under Security (leave TLS checked). The next version of Classilla, if and when I get those SSL changes done, will have them defaulted off as well.

34 is about 80% done (slogging through JavaScript), and the MP3-enhanced 31 is now playing substantially more audio files without problems. There is still a critical issue with parsing MP3 metadata and it's still quite crashy, but it's developing pleasingly quickly.

4 comments:

  1. Thanks, changed security, and on a few HTTPS sites I tried so far there's been no problem.

    ReplyDelete
  2. Found a problem on my county library website, connection reset.

    ReplyDelete
  3. This makes it easier to switch when you have to.

    https://addons.mozilla.org/en-US/firefox/addon/ssl-version-control/

    ReplyDelete
  4. On Classilla and POODLE, you should backport this if you hasn't already:
    https://bugzilla.mozilla.org/show_bug.cgi?id=571796

    ReplyDelete

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