Subject: Re: [conex] Kathleen Moriarty's Discuss on draft-ietf-conex-destopt-09: (with DISCUSS and COMMENT)

From: Suresh Krishnan <[email-masked]>
Date: Thu, 1 Oct 2015 01:41:53 +0000

Hi Kathleen,
   Thanks a lot for your comments. Please find responses inline.

On 09/30/2015 03:22 PM, Kathleen Moriarty wrote:
> Kathleen Moriarty has entered the following ballot position for
> draft-ietf-conex-destopt-09: Discuss
>
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> Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html
> for more information about IESG DISCUSS and COMMENT positions.
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> The document, along with other ballot positions, can be found here:
> https://datatracker.ietf.org/doc/draft-ietf-conex-destopt/
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>
>
> ----------------------------------------------------------------------
> DISCUSS:
> ----------------------------------------------------------------------
>
> I think this should be easy to address, but wanted to discuss options for
> the text in section 7.  Since there is text that says IPsec
> Authentication should be used when integrity protection and the section
> goes on to also discuss encryption, shouldn't there be a similar
> statement that says IPsec encryption should be used when there is a need
> to protect confidentiality?

Yes. We were worried more about the authentication because tampering of 
the packet to scrub the markings would cause audit devices to penalize 
the connection. Encryption on the other hand would be counterproductive 
as the intermediate nodes would be unable to observe the markings.

>
> Also, in reading this, I think because of the selected wording, I was
> thinking that it wasn't clear enough on the need/recommendation for
> authentication or encryption with IPsec since there are options for both
> to be set to NULL/none.  You can have a NULL cipher-suite and you can
> also have authentication set to none to allow for opportunistic security
> negotiations (fairly new RFC for the latter).  There's no need to mention
> these options explicitly, but rather to make it clear that IPsec can be
> used to provide authentication and encryption.  So I think one additional
> sentence and some possible rewording in this section would be helpful.

I have added a new sentence about encryption and reworded some of the 
text to clarify. Does this text change work for you?

OLD:

If the transport network cannot be trusted, IPsec Authentication
should be used to ensure integrity of the ConEx information.  If an
attacker would be able to remove the ConEx marks, this could cause an
audit device to penalize the respective connection, while the sender
cannot easily detect that ConEx information is missing.

In IPv6 a Destination Option header can be placed in two possible
position in the order of possible headers, either before the Routing
header or after the Encapsulating Security Payload (ESP) header
[RFC2460].  As the CDO is placed in the destination option header
before the AH and/or ESP, it is not encrypted in transport mode
[RFC4301].  Otherwise, if the CDO were placed in the latter position
and an ESP header were used, the CDO would also be encrypted and
could not be interpreted by ConEx-aware devices.

NEW:

If the transport network cannot be trusted, the IPsec Authentication 
Header (AH) [RFC4302] should be used to ensure integrity of the ConEx 
information. If an attacker would be able to remove the ConEx marks, 
this could cause an audit device to penalize the respective connection, 
while the sender cannot easily detect that ConEx information is missing. 
Similarly, if confidentiality of the transmitted information is desired, 
the IPsec Encapsulating Security Payload (ESP) [RFC4303] should be used.

Inside an IPv6 packet, a Destination Option header can be placed in two 
possible positions, either before the Routing header or after the ESP/AH 
headers as described in Section 4.1 of [RFC2460].  When the CDO is 
placed in the destination option header before the AH and/or ESP, it is 
not encrypted in transport mode [RFC4301].  Otherwise, if the CDO were 
placed in the latter position and an ESP header was used with 
encryption, the CDO cannot be viewed and interpreted by ConEx-aware 
intermediate nodes effectively rendering it useless.

>
>
> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
>
> For the Security Considerations section, I'd just ask that you add in
> "IPsec" when AH and ESP are first mentioned so this is clear.

Does the above wording change work to resolve this as well?

Cheers
Suresh