Stephen Frost sfrost at snowman.net
Tue Jan 28 19:56:15 UTC 2014


* David Miller (dmiller at tiggee.com) wrote:
> > On Jan 28, 2014, at 1:50 PM, Valdis.Kletnieks at vt.edu wrote:
> >> Hang on Jared, I'm trying to wrap my head around this.  You're saying that
> >> AS7922 has over 50K IP addresses which, if you send a DNS query to that IP,
> >> you get an answer back from *an entirely different ASN*? How the heck does
> >> *that* happen?
> > 
> > Yup.
> What you detected is a misconfiguration of devices on those networks,
> but that misconfiguration (in and of itself) is not necessarily what is
> commonly referred to as "IP spoofing" in the context of BCP38.
> You have *not* "shown" that these ASNs "allow IP spoofing".  You have
> collected one data point that indicates the mere possibility that these
> ASNs allow IP spoofing.

Sounds like he's got about 50k such data points, in some cases.

> In the example that you provided, you sent a DNS query to a Pacenet
> (India) IP and received a response from a Vodafone (India) IP address.
> The IP from which you received the invalid response is an open resolver
> (bad thing).  It is completely plausible that whatever device is being
> queried has interfaces on both networks.

If it was only one (and for those ASNs where it *is* only one, or even a
few, IPs) then I'd tend to agree with you, however...

> To have "shown" that this ASN "allows IP spoofing" you must have
> demonstrated that this response packet, sourced from a Vodafone IP,
> entered the "Internet" from a Pacenet router interface.  Unless I am
> missing something here, you haven't come close to showing that.

We're talking about 50,000 distinct IPs which are doing this in some
cases.  It strikes me as at least pretty unlikely that all 50,000
devices (or 25,000 or 10,000 or what-have-you, if you want to consider
that some devices might have multiple IPs) out there have multiple
interfaces which cross ASN boundaries.  Sure sounds to me like
*someone* out there has some serious issues to deal with, and the rest
of us are paying the price of their inaction.


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