On Wed, 15 Oct 2014 02:53:03 +0000 [email protected] 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? -- tor-talk mailing list - [email protected] To unsubscribe or change other settings go to https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk
