Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1YTYbf-0003Hr-OL for pgsql-hackers@arkaria.postgresql.org; Thu, 05 Mar 2015 16:26:39 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.80) (envelope-from ) id 1YTYbf-0001Av-79 for pgsql-hackers@arkaria.postgresql.org; Thu, 05 Mar 2015 16:26:39 +0000 Received: from makus.postgresql.org ([2001:4800:1501:1::229]) by malur.postgresql.org with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1YTYbd-00017f-FS for pgsql-hackers@postgresql.org; Thu, 05 Mar 2015 16:26:37 +0000 Received: from tamriel.snowman.net ([2001:4830:167b::11]) by makus.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1YTYba-0000RG-7r for pgsql-hackers@postgresql.org; Thu, 05 Mar 2015 16:26:35 +0000 Received: by tamriel.snowman.net (Postfix, from userid 1000) id 79CCC5F7AB; Thu, 5 Mar 2015 11:26:33 -0500 (EST) Date: Thu, 5 Mar 2015 11:26:33 -0500 From: Stephen Frost To: Bruce Momjian Cc: Tom Lane , PostgreSQL-development Subject: Re: MD5 authentication needs help Message-ID: <20150305162633.GX29780@tamriel.snowman.net> References: <20150304174354.GC29780@tamriel.snowman.net> <20150304175857.GA31979@momjian.us> <20150304182731.GG29780@tamriel.snowman.net> <20150304191625.GB31979@momjian.us> <20150304192151.GJ29780@tamriel.snowman.net> <20150304193715.GC31979@momjian.us> <20150304194654.GL29780@tamriel.snowman.net> <20150304204327.GD31979@momjian.us> <24254.1425502449@sss.pgh.pa.us> <20150304235555.GA24491@momjian.us> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="UBlFrcG9zwrDu6zE" Content-Disposition: inline In-Reply-To: <20150304235555.GA24491@momjian.us> X-Editor: Vim http://www.vim.org/ X-Info: http://www.snowman.net X-Operating-System: Linux/3.13.0-45-generic (x86_64) X-Uptime: 11:23:30 up 42 days, 16:12, 6 users, load average: 0.03, 0.10, 0.13 User-Agent: Mutt/1.5.21 (2010-09-15) X-Pg-Spam-Score: -1.9 (-) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-hackers Precedence: bulk Sender: pgsql-hackers-owner@postgresql.org --UBlFrcG9zwrDu6zE Content-Type: text/plain; charset=us-ascii Content-Disposition: inline * Bruce Momjian (bruce@momjian.us) wrote: > One way to fix #2 would be to use a per-user or per-cluster counter for > the session salt, rather than a random number --- that would change > replays from ~16k to 4 billion, with no wire protocol change needed. I'm not against doing that if we decide to ignore the pg_authid-based vector (which we could certainly do), but given the relatively poor hashing algorithm we use and the small salt, along with the commonly used practice of using TLS to address network-based attacks, I'm not sure it's really worth it. Note that changing the algorithm or the salt would require a wireline protocol change and therefore isn't interesting to consider as, if we're going to do that, we should be moving to a vetted solution instead. Thanks! Stephen --UBlFrcG9zwrDu6zE Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBCgAGBQJU+IO5AAoJEO1sijiDR2RV3LAP/iP+GkwDK/IIu36FBFKxiZme NezWfHNc8vkH1e3KUioeCWjUc6RWkLGdR3qi6TQfM9ChUx69AVslb7B7cdfeaEgH m3TIGUMKeC5rJd7BQDD7JkH6OERSVi30AmOs39v1K3Ai1ePTwNS+UPw+3g37oZb9 a2ijcoW3QQa9B0x/oZKYshVe2M6n8yNZd9jDfBRGLgxEF+96CT/bvzYQJl8XCtVJ lbR22Qu6pSkBe8Pzcz9pxVVGX0m9W3aoHNgN7PoVGkgk8sdkwCMruYoAzJUvPIOL lhPm0IOpV1eG+Gl9iNe1eY6cprcWDW089qN84PO2g3lYbszgd6isS2munA2X/Z/U /+dNXDpnJ4griTcA3sUjtgQtrFuirrT2kMESdJZHr+9MPFx2jMJzw42GJiqK+JA0 4KDuY8poid9WXkeCKEoCcA2UG3CPY36Wc6MEPVg8uVmvGO8y9Ic4TSPuHgHjRzqP IKYBfPuPtGVDZ3xanYdyn+ucWEdrz8Qt0OMa/oq9pp1TONwpXNwfo4ZEkDjLrJ8e +1Eq1+AkLUAgINTEBHqDPE3tH7o171mswAj4HknTAgzyRzjJeYiquKcynL8UrXMQ xfhuCVl2yUO3qJ05+OxWDVmLlsDy71+cy6y4pg81+z05NMPx1PpvJ5JYZR0cARgS uA2I48dSWcLyIZPpXNOu =2RG/ -----END PGP SIGNATURE----- --UBlFrcG9zwrDu6zE--