Re: [TLS] Prohibiting SSL 3.0

[Yoav Nir <[e-mail]>]

> On Oct 29, 2014, at 5:33 PM, Hubert Kario <[e-mail]> wrote:
> 
> On Wednesday 29 October 2014 17:06:51 Yoav Nir wrote:
>>> On Oct 29, 2014, at 3:25 PM, Hubert Kario <[e-mail]> wrote:
>>> 
>>> On Wednesday 29 October 2014 13:18:59 Ilari Liusvaara wrote:
>>>> On Wed, Oct 29, 2014 at 10:51:39AM +0000, Peter Gutmann wrote:
>>>>> Hubert Kario <[e-mail]> writes:
>>>>>> Even the TLS 1.3 draft says that a client SHOULD NOT send a SSLv2
>>>>>> compatible client hello with server support being stated as MAY.
>>>>> 
>>>>> Good grief, it's still allowing SSLv2 after nearly *twenty years*?  This
>>>>> should have been MUST NOT for both client and server years ago, and at
>>>>> an
>>>>> absolute minimum SHOULD NOT SSLv3 as well.
>>>> 
>>>> Also, one can't even use SSLv2 compatible ClientHello for TLS v1.3
>>>> because
>>>> TLS v1.3 backward compatiblity mode requires extensions, and SSLv2 can't
>>>> pass those.
>>>> 
>>>> Checking SSL pulse (which I think scans global Internet, not all kinds of
>>>> odd internal sites nobody cares about) gives ~19% for SSLv2 (this isn't
>>>> the compatiblity hello, this the whole protocol!), which is scary.
>>> 
>>> In my scans (a bit bigger set than SSL Pulse), I see over 1% of servers
>>> that don't support anything but SSLv2!
>> 
>> I think that shows that there is an issue with the scan. A server that
>> offers only SSLv2 is not on the web. No modern browser can connect to it.
>> Are your scans going by the most popular HTTP sites that also answer on
>> port 443?  Or are these really HTTPS sites that are accessed as such?
> 
> they are very much on the web for IE 6 users

Right. So it’s not like they expect everyone to visit their site. They’re either responding to programmatic clients or they have their small group of users who keep using IE6 on XP especially for accessing those sites.

> I'm using Alexa top 1 million sites
> 
> but I'm not checking if the sites use redirect to https (as the redirect may 
> be just for login page, only for admins, etc.) so it may not be actually 
> visible for regular visitors
> 
> I also don't check for CN mismatch (as some clients don't check CNs too…)

Are you validating certificates?  Could some of these sites be showing the Apache default page with a self-signed certificate?

> That being said, I didn't verify how reliable are the scan results for SSL2 
> Only sites, so yes, it may be even less than 1%.
> 
> -- 
> Regards,
> Hubert Kario