Re: [Chicken-users] OpenSSL egg option defaults poll

[Thomas Chust]

On Thu, 16 Oct 2014, Andy Bennett wrote:

> [...]
> Having said that, I'm not sure which clients on which operating systems
> are SSL 3.0 only.
> [...]

Hello Andy,

if I understand the situation correctly, almost nobody uses SSLv3 since it 
was quickly superseded by the newer TLS variants. But the initial 
connection setup is similar between SSLv2 and SSLv3, while for TLS it is 
entirely different and usually one uses the SSLv2 variant with additional 
information that TLS is supported, if the other endpoint also supports 
TLS, the protocol will then be upgraded. You can tell OpenSSL to support 
only SSLv2, only SSLv3, only TLS or all three variants together. But you 
cannot specifically exclude SSLv3 and still allow SSLv2 and TLS.

> [...]
> Have you seen this article by Google about TLS_FALLBACK_SCSV?
> [...]

Yes. Whether that security measure is supported depends on the version of 
the underlying SSL library, I think it is incorporated in OpenSSL 1.0.1j. 
I'm unsure whether anything special needs to be done to activate the 
feature.

Personally, I think the big mess of SSL/TLS protocol versions, extension 
features and cipher suites is so hideously complex by now that there will 
always be some more hidden vulnerabilities %-] For anything truly security 
critical I would try to use an alternative protocol with a less convoluted 
design and with stronger default crypto algorithms.

Ciao,
Thomas


--
When C++ is your hammer, every problem looks like your thumb.