Re: default LDM to CheckHostIP=no

On Fri, Apr 01, 2011 at 12:17:47PM -0700, Vagrant Cascadian wrote:
> i've thought for some time we should consider defaulting to
> ignore the host ip address, to reduce the need to run
> ltsp-update-sshkeys whenever the ip address changes.
> 
> security-wise, i'm not sure what we gain by erroring out
> whenever the ip address changes- as long as we're connecting to
> a known hostname and host key pair, the connection should be
> mighty secure.

Well, a successful attack might involve either taking over DNS
or (which might prove easier) pushing rogue DHCP server pointing
to rogue DNS server but otherwise replicating the proper one's
setup.  This dhcpd should be significantly faster (or employ one
more trick if it's not employed by proper one yet) to achieve the
result, and this rather requires either physical access to the
network or breaching at least one fast enough host/VM on it to
continue.  (BTW this could also be discovered via buggy PXE BIOS
like some e100 due to them ignoring next-server and trying to
TFTP into a DHCP server nevertheless, but then again it could
be covered up by replicating tftpd too)

I'd consider all of the above quite noticeable an effort just to
get a chance to get to user sessions and/or terminal server data;
that is, probably not an easiest attack vector at all.

If the system is being specifically hardened/locked down
then clearly mentioning the need to enable strict host check
in deployment docs would seem enough and adequate.

-- 
 ---- WBR, Michael Shigorin <mike-u2l5PoMzF/[email protected]>
  ------ Linux.Kiev http://www.linux.kiev.ua/

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