[LAC-TF] Fwd: Re: Predictable IP protocol values

Fernando Gont fgont at si6networks.com
Sat Apr 28 17:55:27 BRT 2012


El I-D y propuesta al que se hace referencia es el mismo que discutimos
con Ivan Arce en estas listas, para mejorarlo.

En fin... :-)


-------- Original Message --------
Subject: Re: Predictable IP protocol values
Date: Sat, 28 Apr 2012 16:28:31 -0400
From: Joel M. Halpern <jmh at joelhalpern.com>
To: Ole Trøan <otroan at employees.org>
CC: ipv6 at ietf.org Mailing List <ipv6 at ietf.org>,  Fernando Gont
<fgont at si6networks.com>, Bob Hinden <bob.hinden at gmail.com>

It seems to me that the proposed document is a partial fix to a marginal
Yes, I take it as given that if I followed the references I wind find
descriptions of the attacks.  I do see how one could force fragmented
packets if one knew that A was talking to B at the current moment.

However, it seems to me that in the vast majority of cases, if the
attacker knows that A is talking to B, he can probably observe the
packets between A and B (and it must be a conversation of many round
trips to allow for observation, triggered behavior, and useful attack.)
 As such, none of the specified solutions would seem to help much.

Hence, I am left concluding that the right answer is not to publish any
recommendations in this space.


On 4/27/2012 4:21 AM, Ole Trøan wrote:
> working group,
> [changed subject]
> in the context of http://tools.ietf.org/html/draft-gont-6man-predictable-fragment-id-02
> any opinion on how to proceed?
> - document covering predictable values in IETF protocols in general
> - document predictable IP ID fields in both IPv4 and IPv6
> - fix the predictable fragment ID problem in IPv6
> - do nothing?
> cheers,
> Ole
> On Apr 26, 2012, at 22:53 , Fernando Gont wrote:
>> Hi, Ole,
>> On 04/26/2012 08:50 AM, Ole Trøan wrote:
>>>> I think that draft-gont-6man-predictable-fragment-id is also ready
>>>> for wg call for adoption as wg document -- I've rev'ed the
>>>> document since IETF 83 in response to the feedback received during
>>>> my presentation (i.e., just require the Frag ID to be
>>>> unpredictable, without mandating any particular algorithm).
>>> the chairs have an action item on taking this to the mailing list.
>>> there was an issue that I believe Bob raised, if we were going to
>>> have publish RFCs on every field in TCP/IP protocols that should
>>> have unpredictable values, or if we should have a generic
>>> recommendation applying to protocol design in general.
>> I believe that a generic document about protocol design that discusses
>> this issue would be valuable, such that *new* protocols and protocol
>> implementations do not incur into this problem. However, in this
>> particular case (Fragment ID), the IPv6 standard itself is suggesting
>> to use a counter, and hence the spec should be fixed.
>> That aside, different fields have different requirements. For example,
>> the constraints for randomizing the transport protocol ports are
>> different from those of producing unpredictable IDs, and different from
>> those of say, randomizing the TCP sequence numbers, or randomizing the
>> IPv6 Flow Label. The consequences of the particular approach that you
>> follow vary quite a bit in each case.
>> Thanks,
>> --
>> Fernando Gont
>> SI6 Networks
>> e-mail: fgont at si6networks.com
>> PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492
> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> ipv6 at ietf.org
> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> --------------------------------------------------------------------

More information about the LACTF mailing list