On 20/10/2014 02:58, Sam Varshavchik wrote: > Ángel González writes: > >> Sam Varshavchik writes: >> > Jakob Bohm writes: >> > > For clients (see above), there are API (not just ABI) changes, >> > > requiring SSL/TLS client codes to pass extra options to get the >> > > TLS_FALLBACK_SCSV protection feature. At least that is how it was >> > > in the original patch posted to the openssl mailing lists. >> > >> > I do not see why an extra option is needed. It should be enabled by >> default, >> > and maybe have an extra option to turn it off. >> >> >> SSL/TLS has a protocol version negotiation. If the client wants to >> perform a version downgrade based on OOB data (such as a network error), >> then it's his duty to do tag downgrades as such. > > I thought about writing up a detailed explanation of why I think this > is wrong, but I caught myself – it would be a waste of time, and won't > accomplish anything useful. > > Let's just wait to see how GnuTLS handles this. As I said before, I > expect GnuTLS to have the TLS_FALLBACK_SCSV protection enabled in > their API by default, with the client applications having an > additional option to turn it off, so all existing GnuTLS applications > will get the benefit of TLS_FALLBACK_SCSV by default. > > Meanwhile, all OpenSSL clients will have to do a code change, in order > to enable it. > > Just like GnuTLS appears to have the elliptic curve ciphers enabled by > default, and OpenSSL requiring a silly option (actually, two > alternative silly versions, depending on the OpenSSL version) to > enable them. > Update: It appears that OpenSSL does not need a code change in most clients. Only clients that bypass the automatic version negotiation by manually making new connections with lower protocol versions need to make an an extra call to tell OpenSSL that "the maximum TLS version passed to OpenSSL in a call is not the true maximum, but a lower value because the client application believes that the server would fail with the higher value" (whew that was long).
Unfortunately, in the rush to get the fix out, they didn't write full documentation, causing lots of confusion, in fact I am not sure what is and isn't the rules. Enjoy Jakob -- Jakob Bohm, CIO, Partner, WiseMo A/S. http://www.wisemo.com Transformervej 29, 2860 Søborg, Denmark. Direct +45 31 13 16 10 This public discussion message is non-binding and may contain errors. WiseMo - Remote Service Management for PCs, Phones and Embedded ------------------------------------------------------------------------------ Comprehensive Server Monitoring with Site24x7. Monitor 10 servers for $9/Month. Get alerted through email, SMS, voice calls or mobile push notifications. Take corrective actions from your mobile device. http://p.sf.net/sfu/Zoho _______________________________________________ Courier-imap mailing list Courier-imap@lists.sourceforge.net Unsubscribe: https://lists.sourceforge.net/lists/listinfo/courier-imap
