Re: [secdir] secdir review of draft-ietf-mpls-residence-time-12
Greg Mirsky <gregimirsky@gmail.com> Wed, 25 January 2017 19:34 UTC
Return-Path: <gregimirsky@gmail.com>
X-Original-To: secdir@ietfa.amsl.com
Delivered-To: secdir@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 73E6B129B3F; Wed, 25 Jan 2017 11:34:11 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.999
X-Spam-Level:
X-Spam-Status: No, score=-1.999 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_FROM=0.001, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=gmail.com
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 JaHEFlIUaj-y; Wed, 25 Jan 2017 11:34:08 -0800 (PST)
Received: from mail-ot0-x231.google.com (mail-ot0-x231.google.com [IPv6:2607:f8b0:4003:c0f::231]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 2378A129B4B; Wed, 25 Jan 2017 11:34:08 -0800 (PST)
Received: by mail-ot0-x231.google.com with SMTP id f9so159638369otd.1; Wed, 25 Jan 2017 11:34:08 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=FD5tHuh5iOVhqNzvf5B3mg8XqYopK82RKDUowgMNsDI=; b=UY/qsNwVem8sZRr9AkGAPvsUkx51PabTbJNJy15n3kn+lvBmuboEaRe2B6a+brfmgq tmiB1/Pfy7y07j15GTwagzzVT9+lYzHuAiFl6hqDg3NupRwrH38w+1AywRtd23lDNCMk N0y3GbOGJSiueFZ7XV7jr++owN5mpSDRTE07Yasr7skHIhxgx8LwgZDHLnfEevxrv4wW Ik/goL8IQbzT7s7yGmNrDdKYpp0xJL0Y4yIVbPNN74CX0TRKQ9+ayBCDzOnGBoMWpjMY +YpSbouAe0lO6GJwmNSaVUJhltICsrp3eX8TE9J4pxnfYHeQfLFCRCNsLNYbJkIh0P1f Fj+w==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=FD5tHuh5iOVhqNzvf5B3mg8XqYopK82RKDUowgMNsDI=; b=ZqhCIXsPOh2buEYqgGqyw9jKD3Ut4PYUmQPEjOUrBO32srHyWnj8c+BuDj7ii+Sdb3 Yba/c0TGd7XDrEieEsOCHEMKHfnL1gaKfHmNQe3Oc+JpitMGY73NIo1SQNXqdRfCI3s9 9AsXuPVJ6MOu7Y1l++Nuua5z/l7p4OIyD8IPgaIA4xNuSZa5dclsHxg4gHQhyi1DzjyG 8uDJXjGPlfJ4S/311EmgDsnqTwNy8TqKb+fDsd+cirNMDDlvAArHYAzJtsZjIqt8J4GV txYqybHBSDwrRMBRkYchNTMXTzW0lZ2CjgHlDpd952D02sJmNoltXEqiACxsrB5+n04Y hr+Q==
X-Gm-Message-State: AIkVDXI4Gc4wkH7+PSH7wGZylLWUZbK5mIhRJIJ3frtO+jebm0RbZH1l//4l+QLlu+W9lThVEjunjIISnpA8rw==
X-Received: by 10.157.32.135 with SMTP id x7mr18793858ota.35.1485372847481; Wed, 25 Jan 2017 11:34:07 -0800 (PST)
MIME-Version: 1.0
Received: by 10.157.1.103 with HTTP; Wed, 25 Jan 2017 11:34:06 -0800 (PST)
In-Reply-To: <20170125055730.GK8460@kduck.kaduk.org>
References: <20170118060025.GN8460@kduck.kaduk.org> <CA+RyBmVfOCJQ2eA49mi6Ye4AfSCRS5gcio+aO3AgbO_nGDuyiQ@mail.gmail.com> <20170125055730.GK8460@kduck.kaduk.org>
From: Greg Mirsky <gregimirsky@gmail.com>
Date: Wed, 25 Jan 2017 11:34:06 -0800
Message-ID: <CA+RyBmWFmH-a-aSEVH5juVU8EVVL7x-xf8A4i9GB_U5jLf3AyQ@mail.gmail.com>
To: Benjamin Kaduk <kaduk@mit.edu>
Content-Type: multipart/alternative; boundary="94eb2c033074eee9b40546f050ab"
Archived-At: <https://mailarchive.ietf.org/arch/msg/secdir/NjxEWXEGPoCARhMl-KaWcjRTzuM>
Cc: Loa Andersson <loa@pi.nu>, draft-ietf-mpls-residence-time.all@ietf.org, "iesg@ietf.org" <iesg@ietf.org>, "BRUNGARD, DEBORAH A (ATTLABS)" <db3546@att.com>, secdir@ietf.org
Subject: Re: [secdir] secdir review of draft-ietf-mpls-residence-time-12
X-BeenThere: secdir@ietf.org
X-Mailman-Version: 2.1.17
Precedence: list
List-Id: Security Area Directorate <secdir.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/secdir>, <mailto:secdir-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/secdir/>
List-Post: <mailto:secdir@ietf.org>
List-Help: <mailto:secdir-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/secdir>, <mailto:secdir-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 25 Jan 2017 19:34:11 -0000
Hi Ben, many thanks for taking time to review the proposed updates and share your comments, much obliged. My next steps: - Will use your text in the Security Considerations section, thank you. - Will place cases A and B as sub-sections, per your suggestion. - Will share the update by end of the week. Kind regards, Greg On Tue, Jan 24, 2017 at 9:57 PM, Benjamin Kaduk <kaduk@mit.edu> wrote: > On Fri, Jan 20, 2017 at 05:47:00PM -0800, Greg Mirsky wrote: > > Hi Ben, > > thank you for the careful review and the most helpful comments and > > suggestions. We're working on the new version to address GEN-ART, OPS and > > Security comments. I've attached the diff and current working version of > > the draft. Please find my responses to your comments in-lined and tagged > > GIM>>. > > Thanks! > Most of the changes are helpful; the only thing I would note about the > new text is in the security considerations, where the discussion of > "complex crypto schemes" seems like it should come after the mention > of "for further study", not before. > > I as a new reader to the field would still benefit from some discussion > and/or examples of how the new data structures interact with each other > and the parent containers, but I should defer to the experts as to what > is actually needed. > > I will trim the parts of the message that I sound good and I have no > further comment on. > > > > > On Tue, Jan 17, 2017 at 10:00 PM, Benjamin Kaduk <kaduk@mit.edu> wrote: > > > > > This document also mentions RFC 7384, whose entirety is security > > > requirements > > > of time procotols, which probably contains more detail than this > document > > > would > > > need if discussion was inline. However, the security considerations of > > > draft-ietf-mpls-residence-time-12 also contains discussion about how > > > PTP-aware nodes on the path are required to modify the messages, and > the > > > needed trust model involves these nodes being trusted to perform those > > > modifications. > > > That seems true and is probably fine for a protocol that is running on > > > "trusted infrastructure", but the claim is also made that the messages > > > modified > > > by intermediate nodes "cannot be authenticated". This is only somewhat > > > true, as one can create complex crypto schemes that involve giving key > > > material to intermediate nodes that can let them make authenticated > > > (but detectable) modifications. Such schemes seem far too complex for > the > > > topic at hand, though, as they are likely to increase the processing > delay > > > for the time packets, and it seems fine to defer investigating them in > the > > > same way that it is fine to defer investigating > authenticating/encrypting > > > the RTM data that does not need to be modified by intermediate nodes, > which > > > is explicitly noted in the security considerations. > > > > > GIM>> I agree with your suggestion. Would the following change address > your > > comment: > > > > --- > > > > OLD TEXT: > > > > As a result, the content of the PTP-related data in RTM messages that > > > > will be modified by intermediate nodes cannot be authenticated, and > > > > the additional information that must be accessible for proper > > > > operation of PTP 1-step and 2-step modes MUST be accessible to > > > > intermediate nodes (i.e. - MUST NOT be encrypted in a manner that > > > > makes this data inaccessible). > > > > ... > > > > The ability for potentially authenticating and/or encrypting RTM and > > > > PTP data that is not needed by intermediate RTM/PTP-capable nodes is > > > > for further study. > > > > NEW TEXT: > > > > That likely to require some complex crypto schemes that involve giving > key > > > > material to intermediate RTM/PTP-capable nodes that can let them make > > > > authenticated (but detectable) modifications to the additional > > > > information in RTM messages. > > > > The ability for potentially authenticating and/or encrypting RTM and > > > > PTP data for scenarios both with and without participation of > > > > intermediate RTM/PTP-capable nodes is for further study. > > I think this should be reordered to be more useful, something like > (with a few more tweaks): > > In addition - particularly as applied to use related to PTP - there > is a presumed trust model that depends on the existence of a trusted > relationship of at least all PTP-aware nodes on the path traversed by > PTP messages. This is necessary as these nodes are expected to > correctly modify specific content of the data in PTP messages and > proper operation of the protocol depends on this ability. In practice, > this means that those portions of the messages cannot be covered by > either confidentiality or integrity protection. Though there are > methods that make it possible in theory to provide either or both such > protections and still allow for intermediate nodes to make > detectable but authenticated modifications, such methods do not seem > practical at present, particularly for timing protocols that are > sensitive to latency. > > The ability for potentially authenticating and/or encrypting RTM and > PTP data for scenarios both with and without participation of > intermediate RTM/PTP-capable nodes is left for further study. > > > > ------- > > > > > > > > I do think there are some relevant security considerations that are not > > > mentioned, though -- for the two-step flow, an RTM-capable node is > > > required to wait for the follow-up RTM message and make the > corresponding > > > residence time update. This requirement is unbounded and could lead to > > > a resource leak if that follow-up packet fails to arrive, for an > > > implementation > > > that blindly follows the spec without resorting to practical > engineering > > > knowledge. I do not expect there to be any such implementations, but > this > > > document should probably indicate that timing out is okay within > > > "reasonable" bounds, or whatever similar workaround is best practice in > > > this > > > domain. > > > > > GIM>> Indeed, we've implicitly relied on good engineering practice and > left > > out discussion of the timer associated with two-step RTM. > > > > I agree with your observation and propose the following update to text > > > > in section One-step Clock and two-step Clock Modes (added sentence > > underlined): > > > > If the S bit is already set, then the RTM capable node MUST wait for the > > RTM message with the PTP type of follow-up and matching > > > > originator and sequence number to make the corresponding residence time > > update to the Scratch Pad field. > > > > *The wait period MUST be reasonably bound.* > > > Sounds good. > > > > > > > > > > On page 12, last paragraph, we have some text "If no RTM_SET TLV has > been > > > found, then the LSP setup MUST fail [...]". Is this only in the case > > > when the RTM_SET flag is set? If so, that should probably be made more > > > clear in the text, as on my first reading I was surprised, since > > > the RTM_SET generally goes in the LSP_ATTRIBUTES and not the > > > LSP_REQUIRED_ATTRIBUTES, and as such would not be globally mandatory. > > > > > GIM>> Earlier, in the same paragraph, we've said > > > > "If the RTM_SET flag set, the node MUST inspect the LSP_ATTRIBUTES object > > for presence of RTM_SET TLV." ("Node" is used in place of "RTM-capable > > node") > > Thus nodes that are not RTM-capable would not act on RTM_SET Attribure > > Flag, would not be chacking for presence of RTM_SET TLV. > > > Okay. > > > > > I'm also left puzzled by the last paragraph of section 7; it seems to > say > > > that the *last* RTM(-capable) node of the LSP will generate the > follow-up > > > message, but I thought it was generally an earlier node that would be > > > setting the S bit and generating the follow-up message. > > > > > GIM>> Updated text as the following: > > > > The egress RTM-capable node of the LSP will be removing RTM > > encapsulation and, in case of two-step clock mode being indicated, > > will generate PTP messages as appropriate (according to the > > [IEEE.1588.2008]). In this case, the common header of the PTP packet > > carrying the synchronization message would have to be modified in the > > twoStepFlag field indicating that there is now a follow up message > > associated to that. > > Ah, maybe I have un-confused myself. This about the case where the > underlying PTP is a one-step clock, but the RTM path includes two-step > nodes, so the node that removes the RTM wrapper has to synthesize a > follow-up PTP message to contain the correction? > > Making (A) and (B) fully fledged subsections would let them have > indicative tiles, like "Two-step RTM with two-step upstream" and > "Two-step RTM with one-step upstream". > > In any case, I would suggest being more explicit than "the associated RTM > packet must be created" means, explicitly describing what type of RTM > packet > is being created (i.e., the follow-up one?). > > > > > There are also a lot of grammar nits (including very many missing > > > instances of the definite article), but it does not seem worth > enumerating > > > them here. I will try to send a diff to the authors later this week, > > > but time is a bit short at the moment. > > > > > GIM>> Many thanks and greatly appreciate your kind help. > > I guess it is lucky that I did not have time last week, since there is > an updated version that I could be basing changes onto. (Things are still > busy for me, so no guarantees of anything.) > > -Ben >
- [secdir] secdir review of draft-ietf-mpls-residen… Benjamin Kaduk
- Re: [secdir] secdir review of draft-ietf-mpls-res… Greg Mirsky
- Re: [secdir] secdir review of draft-ietf-mpls-res… Benjamin Kaduk
- Re: [secdir] secdir review of draft-ietf-mpls-res… Greg Mirsky