Re: [secdir] Secdir review of draft-ietf-mpls-ldp-gtsm-07

Carlos Pignataro <cpignata@cisco.com> Sat, 02 June 2012 16:23 UTC

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From: Carlos Pignataro <cpignata@cisco.com>
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Date: Sat, 2 Jun 2012 12:23:37 -0400
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To: Brian Weis <bew@cisco.com>
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Cc: secdir@ietf.org, draft-ietf-mpls-ldp-gtsm.all@tools.ietf.org, The IESG <iesg@ietf.org>, "Rajiv Asati \(rajiva\)" <rajiva@cisco.com>
Subject: Re: [secdir] Secdir review of draft-ietf-mpls-ldp-gtsm-07
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Hi Brian,

Many thanks for your review.

The document already talks about these two cases, and also already discusses that multi-hop is out of scope; however I agree with you that highlighting this in the Security Considerations adds to completeness, and also like Rajiv's text.

I just posted a new rev that I believe addresses these (basically Rajiv's text modulo minor edits).

Thanks!

-- Carlos.

On Jun 1, 2012, at 5:11 PM, Brian Weis wrote:

> Hi Rajiv,
> 
> Your proposed text looks good to me. I think it's good to go with this added.
> 
> Thanks,
> Brian
> 
> 
> On Jun 1, 2012, at 1:37 PM, Rajiv Asati (rajiva) wrote:
> 
>> Hi Brian,
>> 
>> Really appreciate your critical review and suggestions. 
>> 
>> I agree to your both of your suggestions, and would propose the
>> following text for us to include in the next revision.
>> 
>> 
>> //
>> As discussed in section 3, it is possible that 
>> - GTSM for LDP may not always be enforced on a single-hop LDP peering
>> session and may still be susceptible to forged/spoofed protocol packets,
>> if the single-hop LDP peering session is set up using Extended
>> Discovery. 
>> - GTSM for LDP may cause LDP peering session to not get established (or
>> torn down), if IP routing ever declares that the directly connected peer
>> is more than one hop away.
>> Suffice to say, use of cryptographic integrity (e.g., RFC 5925) is
>> recommended as an alternate solution for detecting forged protocol
>> packets (especially for the multi-hop case).
>> //
>> 
>> Cheers,
>> Rajiv
>> 
>> 
>>> -----Original Message-----
>>> From: Brian Weis (bew)
>>> Sent: Friday, June 01, 2012 2:16 PM
>>> To: secdir@ietf.org; The IESG
>>> Cc: draft-ietf-mpls-ldp-gtsm.all@tools.ietf.org
>>> Subject: Secdir review of draft-ietf-mpls-ldp-gtsm-07
>>> 
>>> I have reviewed this document as part of the security directorate's
>> ongoing
>>> effort to review all IETF documents being processed by the IESG. These
>>> comments were written primarily for the benefit of the security area
>>> directors. Document editors and WG chairs should treat these comments
>>> just like any other last call comments.
>>> 
>>> This document applies the Generalized TTL Security Mechanism (GTSM)
>>> mechanism defined in RFC 5082. This mechanism is used by routing
>>> protocols as a low-cost non-cryptographic method intended to frustrate
>> off-
>>> path attackers.  It is applicable when the peer is known to be
>> connected by a
>>> single hop.
>>> 
>>> The security considerations of this draft mostly point to RFC 5082's
>>> extensive security considerations section, which is appropriate.
>> However
>>> because this I-D discusses multi-hop cases in greater detail it would
>> be
>>> appropriate for the security considerations section to also discuss
>> multi-hop
>>> a bit more. Here are some thoughts for that:
>>> 
>>> 1) Use of cryptographic integrity (e.g., RFC 5925) should be
>> recommended as
>>> an alternate solution for detecting forged protocol packets in the
>> multi-hop
>>> case.
>>> 
>>> 2) GTSM is expected to be enabled by default for Basic Discovery
>> because
>>> it's usually a single-hop, and disabled for Extended Discovery because
>> it's
>>> usually multi-hop. But then Section 3 mentions several exceptions,
>> which
>>> apparently need to be administratively configured away from the
>> defaults.
>>> Failing to do this when needed results in security risks in either
>> case: either
>>> GTSM isn't deployed when it should be and the router is inadvertently
>> open
>>> to spoofing, or GTSM is deployed when it shouldn't be and this results
>> in an
>>> availability issue because LDP packets will be dropped before reaching
>> the
>>> LDP peer. This should be stated in the Security Considerations.
>>> 
>>> Brian
>>> 
>>> 
>>> 
>>> 
>>> 
>> 
> 
> 
> -- 
> Brian Weis
> Security Standards and Technology, SRTG, Cisco Systems
> Telephone: +1 408 526 4796
> Email: bew@cisco.com
> 
> 
> 
> 
>