dynamic IPSEC

Christian Kratzer ck at cksoft.de
Mon Aug 11 05:23:39 PDT 2003


On Mon, 11 Aug 2003, Kent Hauser wrote:

> Hi Mike,
> Had any progress? I've also by stymied for a clean solution. Previously, I
> used a simple SED script from executed from "/etc/ppp/ppp.linkup" to edit a
> "setkeys" script which then negotiated with the office ascend router/gw & all
> was VPN heaven. However, I now need to negotiate mobile(FreeBSD) to
> static(FreeBSD) & that is proving problematic. Executing a SED script after
> DHCP of mobile is easy, but it seems I also need to SED the static host's SPD
> -- ie no wildcards allowed as in the ascend router situtation. Needless to
> say, allowing "unauthenticated" hosts (read anyone) to modify the SPD on a
> machine so that it can be authenticated strikes me as putting the cart before
> the horse.
> When I install a "wildcard" host ( on the static side, racoon only
> negotiates the mobile->static SAD...which is useless & expires. Seems to me
> that racoon needs to update kernel SPDs with wildcards to support mobile
> VPNs. At least that's all I've been able to come up with.
> Have you found a silver bullet?

Solution 1:

the silver bullet to allow roaming clients with dynamic address to connect to
your racoon is to have no policy at all defined for them and use an anonymous
section your racoon.conf with

	generate_policy on;

This way your clients connect and racoon sets up any policy they request.

This is a bit ugly as you have to trust them not to screw up your policy but
seems to be the only solution currently availale with racoon.

You will also want to use certificates instead of preshared keys for
authentication unless you are comfortable with having a single preshared key
for all your roaming users.

Solution 2:

We have a setup where we have 3 offices each with dynamic ip's and freebsd
boxes as their gateways.  The boxes all run scripts to register their dynamic
ip address at a colocated box with a static ip.  The boxes also resolve each
others ip addresses every 5 minutes and generate a new ipsec.conf and install
it if it differs from the previous one.  The system is now very stable and
we have ispec tunnels between all 3 offices.

If something changes they rewire themselves on the fly.


CK Software GmbH
Christian Kratzer,         Schwarzwaldstr. 31, 71131 Jettingen
Email: ck at cksoft.de
Phone: +49 7452 889-135    Open Software Solutions, Network Security
Fax:   +49 7452 889-136    FreeBSD spoken here!

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