[tor-talk] howsmyssl

[<BM-2cTjsegDfZQNGQWUQjSwro6jrWLC9B3MN3@xxxxxxxxxxxxx>]

On Wed, 15 Oct 2014 02:53:03 +0000
tor-talk-request@xxxxxxxxxxxxxxxxxxxx wrote:

> Hi!  It's a new month, so that means there's a new attack on TLS.
> 
> This time, the attack is that many clients, when they find a server
> that doesn't support TLS, will downgrade to the ancient SSLv3.  And
> SSLv3 is subject to a new padding oracle attack.
> 
> There is a readable summary of the issue at
> https://www.imperialviolet.org/2014/10/14/poodle.html .
> 
> Tor itself is not affected: all released versions for a long time have
> shipped with TLSv1 enabled, and we have never had a fallback mechanism
> to SSLv3. Furthermore, Tor does not send the same secret encrypted in
> the same way in multiple connection attempts, so even if you could
> make Tor fall back to SSLv3, a padding oracle attack probably wouldn't
> help very much.
> 
> TorBrowser, on the other hand, does have the same default fallback
> mechanisms as Firefox.  I expect and hope the TorBrowser team will be
> releasing a new version soon with SSLv3 enabled.  But in the meantime,
> I think you can disable SSLv3 yourself by changing the value of the
> "security.tls.version.min" preference to 1.
> 
> To do that:
> 
> 1.  enter "about:config" in the URL bar.
> 
> 2. Then you click "I'll be careful, I promise".
> 
> 3. Then enter "security.tls.version.min" in the preference "search"
> field underneath the URL bar.  (Not the search box next to the URL
> bar.)
> 
> 4. You should see an entry that says "security.tls.version.min" under
> "Preference Name".  Double-click on it, then enter the value "1" and
> click okay.
> 
> You should now see that the value of "security.tls.version.min" is
> set to one.
> 
> 
> (Note that I am not a Firefox developer or a TorBrowser developer: if
> you're cautious, you might want to wait until one of them says
> something here before you try this workaround.)
> 
> 
> Obviously, this isn't a convenient way to do this; if you are
> uncertain of your ability to do so, waiting for an upgrade might be a
> good move.  In the meantime, if you have serious security requirements
> and you cannot disable SSLv3, it might be a good idea to avoid using
> the Internet for a week or two while this all shakes out.
> 
> best wishes to other residents of interesting times,
> -- 
> Nick


While on the topic, these links discuss this issue and provide a test
for the TLS suite:
https://blog.dbrgn.ch/2014/1/8/improving_firefox_ssl_tls_security/
https://www.howsmyssl.com/

The link states that: Another issue is the support for the
SSL_RSA_FIPS_WITH_3DES_EDE_CBC_SHA cipher, which may or may not be a
good idea to use: https://github.com/jmhodges/howsmyssl/pull/17.
Firefox 26 supports cipher suites that are known to be insecure.

This setting can also be disabled in the Firefox configuration. In the
about:config screen, search for security.ssl3.rsa_fips_des_ede3_sha and
disable it.

Should this also occur in TBB?

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