Re: [perpass] SMTP and SRV records

Eliot Lear <lear@cisco.com> Wed, 25 November 2015 06:47 UTC

Return-Path: <lear@cisco.com>
X-Original-To: perpass@ietfa.amsl.com
Delivered-To: perpass@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id E043D1B2ABB for <perpass@ietfa.amsl.com>; Tue, 24 Nov 2015 22:47:35 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -15.085
X-Spam-Level:
X-Spam-Status: No, score=-15.085 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_HI=-5, RP_MATCHES_RCVD=-0.585, SPF_PASS=-0.001, USER_IN_DEF_DKIM_WL=-7.5] autolearn=ham
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id UH2ycHnvyIz5 for <perpass@ietfa.amsl.com>; Tue, 24 Nov 2015 22:47:34 -0800 (PST)
Received: from aer-iport-4.cisco.com (aer-iport-4.cisco.com [173.38.203.54]) (using TLSv1.2 with cipher DHE-RSA-SEED-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id A9BEE1B2ABA for <perpass@ietf.org>; Tue, 24 Nov 2015 22:47:33 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=8592; q=dns/txt; s=iport; t=1448434053; x=1449643653; h=subject:to:references:cc:from:message-id:date: mime-version:in-reply-to; bh=pS30r2UV00FYZ3FR9LdyUYSIeuV+W99NEeoFS/3oWLc=; b=YXrk7SivwuBfIcovD/Pqr6clom31uqAQ4P2lrr1RdiI3X83vvSJdJCWf OD7TjCjwnP8y2Di9auFU6DQkiH6AReAMDkdl4t+iztdaMjlYEH+oQdhTO aAPgSQJH+yu1yS5yPmBlveysMjPICMlgoirve85pX5q1GkHBMMMqBhmTn M=;
X-Files: signature.asc : 481
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: A0CtBABWWFVW/xbLJq1ehA5vwD8XAQmFJEoCghUBAQEBAQGBC4Q1AQEEAQEBIEsKARALGAkWCAMCAgkDAgECARUfEQYBDAYCAQGIKg2tKpAuAQEBAQEBAQEBAQEBAQEBAQEBAQEBDwUEi1KEOwEBgziBRAWWVYJagWFqiA2BW4dEj0eDcmOCER2BVz00AYNqgUEBAQE
X-IronPort-AV: E=Sophos;i="5.20,341,1444694400"; d="asc'?scan'208,217";a="608442242"
Received: from aer-iport-nat.cisco.com (HELO aer-core-4.cisco.com) ([173.38.203.22]) by aer-iport-4.cisco.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Nov 2015 06:47:31 +0000
Received: from [10.61.104.165] (dhcp-10-61-104-165.cisco.com [10.61.104.165]) by aer-core-4.cisco.com (8.14.5/8.14.5) with ESMTP id tAP6lVTO016200; Wed, 25 Nov 2015 06:47:31 GMT
To: Ted Hardie <ted.ietf@gmail.com>, Ted Lemon <mellon@fugue.com>
References: <20151124201103.GA9353@cowbell.employees.org> <5654D5AF.50700@cisco.com> <1448403824760-dbe4ee86-e05e8503-58e2c4c8@fugue.com> <CA+9kkMCxEpE99R7Sf9Wv=tx76JhXVgbxwya3kUN+H_5s6L7xFw@mail.gmail.com>
From: Eliot Lear <lear@cisco.com>
Message-ID: <56555980.4000804@cisco.com>
Date: Wed, 25 Nov 2015 07:47:28 +0100
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:38.0) Gecko/20100101 Thunderbird/38.3.0
MIME-Version: 1.0
In-Reply-To: <CA+9kkMCxEpE99R7Sf9Wv=tx76JhXVgbxwya3kUN+H_5s6L7xFw@mail.gmail.com>
Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="H5u37UN2FxHNpV9bWA2A7DWFx19JdAa46"
Archived-At: <http://mailarchive.ietf.org/arch/msg/perpass/9bpqwGnQo6-3RcwFlr0AB4pUOi4>
Cc: "<perpass@ietf.org>" <perpass@ietf.org>
Subject: Re: [perpass] SMTP and SRV records
X-BeenThere: perpass@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: "The perpass list is for IETF discussion of pervasive monitoring. " <perpass.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/perpass>, <mailto:perpass-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/perpass/>
List-Post: <mailto:perpass@ietf.org>
List-Help: <mailto:perpass-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/perpass>, <mailto:perpass-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 25 Nov 2015 06:47:36 -0000

Yeah, this is what I would suggest as well, especially for SMTP.  There
are a host of operational problems with attempting to vary the port.

Eliot


On 11/24/15 11:41 PM, Ted Hardie wrote:
> On Tue, Nov 24, 2015 at 2:23 PM, Ted Lemon <mellon@fugue.com
> <mailto:mellon@fugue.com>> wrote:
>
>     Tuesday, Nov 24, 2015 4:25 PM Eliot Lear wrote:
>     > What benefit would this add to the average user?
>
>     It's the germ of an interesting idea.   The theory would be that a
>     sniffer at the backbone would have to listen to all traffic, not
>     just traffic on port 25. 
>
>
> ​I don't think that's quite right.  A port-specific sniffer would have
> to know what SMTP port was correct for a specific domain.  Depending
> on the TTL of the record, that might turn into a table lookup for
> setting the sniffers rather than listening to all traffic.
>
> That said, I rather suspect that listening to all traffic is pretty
> much in the program of most signals intelligence agencies anyway,
> because the ephemeral ports can be be used by VoIP and other media
> traffic. DPI on that would tell you which ones were SMTP and which
> others pretty rapidly.
>
>      However, it's not as good as SMTP+TLS, and has the same adoption
>     problem, plus SMTP+TLS has a _big_ head start, so it's probably
>     better to concentrate our efforts on making that work even better.
>
>
> ​ Yes, focusing on getting encryption underneath it seems like a
> better use of energy; at most, port shifting is minor security through
> obscurity, and that doesn't tend to give you a lot of bang for your buck.
>
> Just my two cents,
>
> Ted ​
>
>  
>
>
>     --
>     Sent from Whiteout Mail - https://whiteout.io
>
>     My PGP key: https://keys.whiteout.io/mellon@fugue.com
>     _______________________________________________
>     perpass mailing list
>     perpass@ietf.org <mailto:perpass@ietf.org>
>     https://www.ietf.org/mailman/listinfo/perpass
>
>