Re: libpq compression

On Sat, Jun 16, 2012 at 11:15 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Magnus Hagander <magnus@hagander.net> writes:
>> On Sat, Jun 16, 2012 at 12:55 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> It's not obvious to me that we actually *need* anything except the
>>> ability to recognize that a null-encrypted SSL connection probably
>>> shouldn't be treated as matching a hostssl line; which is not something
>>> that requires any fundamental rearrangements, since it only requires an
>>> after-the-fact check of what was selected.
>
>> Maybe I spelled it out wrong. It does require it insofar that if we
>> want to use this for compression, we must *always* enable openssl on
>> the connection. So the "with these encryption method" boils down to
>> "NULL encryption only" or "whatever other standards I have for
>> encryption". We don't need the ability to change the "whatever other
>> standards" per subnet, but we need to control the
>> accept-NULL-encryption on a per subnet basis.
>
> After sleeping on it, I wonder if we couldn't redefine the existing
> "list of acceptable ciphers" option as the "list of ciphers that are
> considered to provide encrypted transport".  So you'd be allowed to
> connect with SSL using any unapproved cipher (including NULL), the
> backend just considers it as equivalent to a non-SSL connection for
> pg_hba purposes.  Then no change is needed in any configuration stuff.

That seems reasonable. In looking at our current defaults, two things hit me:

Is there a reason why we don't have a parameter on the client
mirroring ssl_ciphers?

and

Shouldn't our default SSL methods include !aNULL, meaning by default
we exclude all ciphers that don't provide authentication (which means
they can be man-in-the-middle'd). AFACIT, eNULL/NULL is disabled by
default unless explicitly enabled, but aNULL isn't..

I don't think it matters from a pure security perspective since we
look inside the actual cert anyway (which shouldn't work with these
methods, I think), but it seems like a wrong default.

That, or just have DEFAULT as being the default (which in current
openssl means ALL:!aNULL:!eNULL.

--
 Magnus Hagander
 Me: http://www.hagander.net/
 Work: http://www.redpill-linpro.com/