[squid-dev] cope with OPENSSL_NO_SSL3 builds of (libre|open)ssl

[Tsantilas Christos]

On 09/10/2015 11:09 PM, Amos Jeffries wrote:
> On 11/09/2015 4:50 a.m., Tsantilas Christos wrote:
>> On 09/10/2015 04:07 PM, Stuart Henderson wrote:
>>> LibreSSL has removed SSLv3, and it can be disabled optionally in OpenSSL
>>> by building with no_ssl3. The patch below allows building against such a
>>
>> I suppose that LibreSSL wants to forces as to use the TLS isntead of
>> sslv3, so maybe it is better to try use the TLS_method() instead of
>> SSLv23_method.
>>
>> Also, with a very quick view looks that the  libreSSL TLS_method() is
>> equivalent to openSSL TLSv1_2_method() method...
>
> Yes, maybe and no :
>
>
> Yes - LibreSSL is following the SSLv2/SSLv3 deprecation RFCs very
> closely. Upcoming OpenSSL versions will be too, eventually. So those
> using the very latest libraries get the very latest up-to-date
> specification requirements applied.
>

The SSLv2 removed from OpenSSL git repository too...

>
>
> Maybe - If I'm reading the OpenSSL docs right the SSLv3_method was
> producing a fixed specific method to negotiate SSLv3-only protocol. The
> TLS_method is negotiating any TLS version. I think use of SSLv3_method
> was a bug to begin with and TLS_method()/SSLv23_method() would be
> correct now.

The SSLv23_method, if the SSLv2 is disabled from options, will sent a 
full SSLv3/TLS message without SSLv2 backward compatibility.

Looks that using the TLS_method/SSLv23_method is the correct.

>
> [ IMO we should rename parseV23Hello to parseV2Hello to clarify that it
> parses a v2 syntax hello. Avoid confusing with SSL*_method() vs
> TLS_method() relevance. ]

This is not exactly correct.
The parseV23Hello actually parses an SSLv3 Hello message which is 
encapsulated to an SSLv2 compatible header.
Unfortunately there are clients which still using it.

>
>
>
> No - TLS_method() is *not* equivalent to TLSv1_2_method(). It is
> equivalent to SSLv23_method() / SSLv23_server_method(). All of those may
> or may not produce TLSv1_2_method() as their output depending on the
> config settings.

This is true. TLS_method is something like "support up to TLSv1.2".

>
> Assuming the patch is correct in swapping SSLv23_method(). Then it
> should actually be swapping to TLS_method() with back-compat #if
> wrappers using SSLv23_method(). As seen with uses of the
> SSLv23_*_method() functions.

Yes.

>
> [ I see the parseV23Hello() is using SSLv23_method() bare. That is a bug
> waiting to happen when OpenSSL v1.2-1.3 hits us. Which should also be
> fixed in this patch scope. ]

True.
The SSLv23_method() is used to parse an SSLv3/TLS hello message, which 
is encapsulated in an SSLv2 compatible SSL header.
We need to replace this method.
With a very quick view the only use of this method is to get the size of 
each cipher in HELLO message. I suppose  it can be hardcoded.
I hope we have some time before the SSLv23_method full removed from 
openSSL and forked libraries.



>
> Amos
>
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