Re: IPv6 and IPSec

["Paul D. Robertson" <paul () compuwar net>]

On Sun, 29 Aug 2004, Michael H. Warfield wrote:

> Hey all,

Hi Mike, that's for such a comprehensive reply!

> > > Hi,
> > >    IPSec based security is MUST for IPv6. Due to this, I would
> > >    assume that end systems would use IPSec to secure the traffic
> > >    going out.
>
> > Why?  It's not a must for IPv4, why would adding address space suddenly
> > require IPSec?  Heck, the cascading headers for V6 offer the chance for
> > pseudo-out-of-band control and encapsulation, why again would you use
> > IPSec?
>
>       It's a missinterpretation of the specs and the requirements.

Ah- that makes sense-

[snip]

>       IPv6 is VASTLY more interesting that this...  There are lots
> of things that are interesting (both in the good sense and the bad
> sense) about IPv6 and security.  Consider "privacy enhanced addresses".
> Now, as a system administrator, how are you going to track down a virus
> infected system that changes it's address every half hour with no audit
> trail?

This is something I need to read up on, I don't recall it being around
when I last looked, but perhaps I simply overlooked it...  I was more
interested in using the encapsulating headers to rope off control and
provide transit a layer or two deep and add some separation for different
populations - all problems I no longer have directly.

>       I restrict ssh to IPv6 only (hell, it's virtually unscannable and
> has no broadcast address and is reachable from anywhere I am on IPv4, why
> not...).  Some of my external servers, the ssh listens only on certain
> IPv6 addresses.  And those addresses change every 15 minutes.  A new address
> is added every 15 minutes and the dns is updated (w/ TSIG).  Each address
> is valid for 2 hours (to allow for DNS TTL).  After that time, it's
> deprecated.  When a deprecated address no longer has a resource (socket)
> attached to it, it ceases to exist on the machine.  Every IPv4 address
> has an entire IPv6 NETWORK (65,536 subnets each containing 16 billion
> billion host addresses).  I have yet to find anywhere on the entire
> internet where IPv6 does not work (private address space or global address
> space), and it works well.  I can reach all my IPv6 stuff from anywhere
> on IPv4.  Why leave it expose and vulnerable (to scanning and probes) on
> IPv4?  Even my virtual web server farm has web services on IPv4 but all
> the security stuff is tightly marshalled over IPv6.

Won't the 4<->6 gateway be vulnerable anyway?  In a mixed environment, it
seems that you'd be stuck with the v4 problems until the environment isn't
so mixed anymore.

>       How do you scan for backdoors, when the intruder adds his own
> unique address (hell, you can add IPv6 to XP without even rebooting the
> damn thing and you have to reboot Linux to disable it) amongst
> 16 billion-billion possible addresses on that wire?  How do you deal
> with bot-nets, were every bot is given a unique contact addresses and
> the server has has thousands of addresses added without having to ask
> anyone?

Have you seen any botnets using v6 in the wild?  I assume that you still
need some sort of v4<->v6 gateway for most leaf nodes these days, so the
traffic will still come down to a v4 address until everyone routes v6
directly.

> >    Want to check out something really NASTY, check out Teredo.
> That's IPv6 over UDP.  A buddy at MS refers to this as the "Evil
> Firewall Destroying Deamon from Hell".  Do you worry about UDP traffic
> over port 3544?  Should you be?  Some people have already found out,
> to their regret, that they should be.

Tunnels have always been an issue for protected networks.  It's one of the
reasons that I wouldn't allow anything that wasn't proxied when I was
running operational user networks.  From there, you normally just need to
do utilization reporting to detect whole-network tunnels, though traffic
inspection at some point becomes necessary once the tunnel thresholds go
under normal usage.

>       IPv6 has LOTS of security implications.  They're just not obvious.
> And a lot of people (particulary in North America) have their heads in the
> sands vis-a-vis IPv6.  At many of my talks, I've had people walk up to
> me later and tell me that they've been seeing this strange traffic on
> their network for ages, they just didn't know what it was.  And now they
> know, and now they need to figure all this out...  IPv6 arrived several
> years ago and anyone who thinks they don't have IPv6 just doesn't know
> that they have it already, and that they don't control it, and that it's
> uniformly routable, and that it's globally addressible (whether their IPv4
> addresses are globally addressible or not).

Hmmm, but won't the default deny access lists on my border stop it unless
I specifically allow IPv6 in?  It seems to me that if I'm doing all the
right things[1], my exposure should be tunnels and mistakes.  Tunnels are
an issue with IPv6 as well, though blocking v6 DNS does seem like a
reasonable bit of defense in depth if I'm not quite ready to deal with the
other issues.

>       But...  Back on the original topic...  IPSec is not required
> to use IPv6.  It's only required by implimentations to be supported in
> order to be "IPv6 compliant".  Use it if you wish, or don't use it if
> you wish.  You don't have to support IPSec to be IPv4 compliant, but you
> do have to support it for IPv6.  Outside of just supporting it, it's
> the same as it ever was.
>
>       OTOH...  IPSec CAN be REALLY usefull in supporting IPv6!  My
> laptop has over a dozen different ways of connecting to IPv6 no matter
> where I am in the world.  If I can pull a native prefix, great.  If not,
> I can go 6to4 or 6over4, no problem.  If that doesn't work, my next fall
> back is IPSec on IPv4 (to tunnel my IPv6 stuff over a VPN) and IPSec NAT-T
> (IPSec over UDP port 4500) next.  If those fail, then I start resorting
> to things like PPP over stunnel or PPP over ssh (both of which have been
> tested).  Beyond that, there are even more access methods that I've never
> tested because I've never run into a circumstance where none of the above
> didn't work.  In most corporate environment with really strict rules,
> IPSec NAT-T (forcing NAT-T even when not cross a NAT) works like a champ.
> Have never been force to resort to things like CCTT, even though they
> are there and ready if I ever find anything that gets in the way of what
> I normally use.  IPSec (particulary NAT-T) is a great firewall bypass tool.
> Ya don't need to run IPSec on IPv6 when you are already tunnelling IPv6
> over IPSec.  :-)

Dammit, I don't have _time_ to play... But now you're gonna make me...

Paul
-----------------------------------------------------------------------------
Paul D. Robertson      "My statements in this message are personal opinions
paul () compuwar net       which may have no basis whatsoever in fact."
probertson () trusecure com Director of Risk Assessment TruSecure Corporation
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