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Re: TrustKeysFrom .. a host netgroup?


From: Mark . Burgess
Subject: Re: TrustKeysFrom .. a host netgroup?
Date: Sat, 11 Jan 2003 10:40:10 +0100 (MET)

Ok, I hear you. The main reason for using IP addresses is that
you normally want to trust a whole subnet at a time when setting
up the keys. After that you switch off trust and be done
with. I can add support for name lookup, but I have no use
for it myself.

I disagree with Luke -- I think DNS is much easier to spoof than IP
addresses.

M

On 10 Jan, Marion Hakanson wrote:
>> Why would you want to trust DNS ?
>> 
>> M
> 
> Mark,
> 
> Luke spoke (typed) my mind before I got a chance to.  I trust DNS here
> because it makes sense to do so.  There are certainly circumstances
> where it does _not_ make sense to trust DNS, but there are other things
> to weigh when making that decision, and having cfengine's author make
> the decision for me is suboptimal, in my opinion.
> 
> For us, it's convenient, it's one source of information, and the consequences
> of DNS being compromised are not so terrible when it comes to cfengine, as it
> is used here.  For example, we do not run cfengine continually, nor
> automatically.  We use it at OS install time, and manually when configuration
> changes are made.  Maybe someday we'll trust cfengine and our own cfengine
> programming enough that we'll turn it loose on its own, but not just yet.
> 
> What irks me is when I have to make my code more complex in order to avoid
> keeping the same piece of information in multiple places, a situation which
> experience has shown causes problems far more often than we've ever had DNS
> compromises to deal with.  And if I don't want to trust DNS, I can enter
> IP addresses everywhere that hostnames are accepted -- most network utilities
> work this way.
> 
> For those of you who want to use host names in this particular situation,
> here's what I've come up with.  Note that the ${policyhost} macro and the
> "policyhost" class get setup in a globally shared file that is imported
> right before this bit of code gets imported into cfservd.conf:
> 
> control:
> 
>   linux::
>     policyhostip = ( ExecResult(/bin/sh -c "host ${policyhost} | grep address 
> | 
> awk '{print $4}'") )
>   !linux::
>     policyhostip = ( ExecResult(/bin/ksh -c "nslookup ${policyhost} | egrep 
> '^Ad
> dress:' | tail -1 | awk '{print $2}'") )
> 
>   any::
>     TrustKeysFrom = ( "$(policyhostip)" )
>     AllowUsers = ( root )
>     cfrunCommand = ( "$(cf_workdir)/bin/cfagent" )
> 
>   policyhost::
>     AllowConnectionsFrom = ( 192.168.10-20.* )
> 
>   !policyhost::
>     AllowConnectionsFrom = ( "$(policyhostip)" )
> . . .
> 
> 
> Above, we are trusting a shell and three utilities along with DNS.
> I'll leave it to the reader to decide if that mess of code is more or
> less error-prone than it would be to simply trust DNS alone.
> 
> Why do I do this?  Because I use ${policyhost} (a _name_) in other
> clauses, e.g. in update.conf and all over cfagent.conf to tell the client
> where to find the latest config files.  Cfengine trusts DNS and accepts
> a hostname _there_ (in "server=$(policyhost)" options of "copy" clauses),
> why not in cfservd.conf?
> 
> Representing the same piece of information in two different locations,
> in two different ways, is just asking for trouble.  They _will_ get out
> of sync and lead to problems.  Way more often than DNS is compromised.
> Give me a simple and consistent user (programmer) interface any day.
> Please!
> 
> Thanks and regards,
> 



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Work: +47 22453272            Email:  address@hidden
Fax : +47 22453205            WWW  :  http://www.iu.hio.no/~mark
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