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Re: Cfengine and multiple firewalls/security realms

From: Tim Nelson
Subject: Re: Cfengine and multiple firewalls/security realms
Date: Wed, 23 Jun 2004 09:26:16 +1000 (EST)

On Tue, 22 Jun 2004, Scott Omar Burch wrote:

> 1) Authentication with keys appears to be tied to the primary network
> interface of each server. Systems which sit behind firewalls in our
> environment have multiple network interfaces. The primary network
> interface is always considered the production interface. We always have
> a secondary interface which is used for management operations (backups,
> monitoring, etc.). If I have a host called snoopy then qfe0 would be
> snoopy and qfe1 would be snoopy-mgmt. For this example snoopy sits
> behind a firewall and the Cfengine policy server is on the other side of
> the policy server. When we execute cfrun on the policy server we found
> that no matter what we did we could not get authentication to work along
> the management interface...we needed to open 5308 on the production
> interface...Cfengine appears to always use the interface named snoopy.
> (This problem is really a minor issue, but we would prefer to do all
> Cfengine operations on the management interface..we did try binding the
> agent/cfservd to managment..but that did not work because the keys
> appear to only try to finalize the authentication along the production
> interface)

        Interesting.  Others have answered your question, so I'll comment
on my approach just for you to compare.  I run each service on a separate
interface, so that if people want to break in, and find complimentary
holes in service1 and service2, if they're on different interfaces,
hopefully the cracker won't realise that they're on the same machine, and
will give up.

> 2) Our bigger issue is how to have a policy server when there are
> multiple security realms. We have multiple layers of firewalls. For
> instance there are firewalls between application servers, web servers,
> database servers, and authentication servers, as well as our internal
> networks. (The servers in application/database/web/authentication layers
>   are on external networks). The Cfengine policy server sits in a
> special managment network that is on our internal network. Our general
> policy is not to allow external machines to tunnel through our
> firewalls. Source NAT and Destination NAT is in heavy use here, so
> sometimes we have used NAT names for internal machines to allow access
> to them from outside..also sometimes host routes along the management
> interfaces solve some issues. How are others working around this type of
> issue. We don't really want to have multiple policy servers..I
> especially don't want multiple servers that require the use of external
> tools to keep in sync (I have seen the discussions of having a policy
> server inside/outside, etc...obviously this will not work here as we
> have mutiple firewalls to contend with..we would need far more than 2
> policy servers. It would be really nice if Cfengine had the option to
> push rather than pull, that would allow it to function nicely in our
> environment without opening holes through our firewalls. I am aware that
> it is unlikely that Cfengine could be used to exploit the policy server,
> but buffer overflows have and can be introduced in the code...and we are
> not generally willing to take those risks (also having a general policy
> to open ports into our internal network is not a good practice). We care
> as much about the security of the servers that are clients as we do
> about the policy server. What are your suggestions..and are there any
> plans to implement the option of a Cfengine push/rather than pull.

        Well, cfengine can already be set to do push, but instead of
telling you about that, I'll instead tell you my solution, which has the
advantages of both.

        In my situation, I have two networks, an internal and an external.
My Gold Server is on the internal network, which is the master for all
clients on the internal network.  I have a "Gold Mirror" on the external
network, which is master for all the machines there.
        I have my cfengine configuration set up so that I edit a
file.  When I run a perl template converter on the .pt file, it generates
two .cf files in two different directories, one for my internal network,
and one for my external network.  Then it does an automatic scp to copy
the files in the external directory to the "Gold Mirror" machine.  As long
as the "Gold Mirror" machine doesn't fail, standard cfengine pull works
just fine.  If the Gold Mirror fails, I just do a recursive scp afterwards
to sync it with the autoritative files on the Gold Server.

        Does that sort of situation cover your problem?


Tim Nelson
Systems Administrator
Sunet Internet
Tel: +61 3 5241 1155
Fax: +61 3 5241 6187
Email: address@hidden

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