Re: [TLS] drop obsolete SSL 2 backwards compatibility from TLS 1.3 draft

[Florian Weimer <[e-mail]>]

On 12/24/2014 08:02 AM, Yuhong Bao wrote:
>>>
>>> There's no reason to maintain any backwards support here just for Internet
>>> Explorer 2.0 on Windows 3.1.
>>>
>>
>> I’m not objecting to the change, but I am objecting to the hyperbole. The issue is with Internet Explorer 6 on Windows XP, which still exists, but more importantly, a lot of web service clients running on top of Windows XP use the same SCHANNEL library as IE would use, so they issue a SSLv2 ClientHello. Despite Microsoft’s best efforts, there is still a substantial but diminishing install base of XP.
>>
>> It’s fine for us to break compatibility with these clients, but let’s not pretend it’s some ancient technology that doesn’t exist in the market anymore.
>>
> If needed, one suggestion would be to cap the old SSLv2 ClientHello to TLS 1.2.

At least make it TLS 1.1 instead.  With TLS 1.2, the SSLv2 ClientHello
cannot include the signature algorithms extension, so SHA-1 is used
instead of the concatenation of MD5 and SHA-1, and this usually not what
is wanted.

-- 
Florian Weimer / Red Hat Product Security