[Cerowrt-devel] improving security: xinetd

David Lang david at lang.hm
Fri Jan 17 18:24:02 EST 2014

On Thu, 16 Jan 2014, Dave Taht wrote:

> in terms of a stable release, improving security some more has been
> weighing on my mind.
> One of the things cero does differently than openwrt
> is that it uses the xinetd daemon. It rather than having things like dropbear
> or rsync listening directly on ports, and specifically only allows access
> to certain services (like ssh) from certain ip addresses.
> There are also sensors for connection attempts via ftp or telnet that
> disable all services when someone accesses them, for 120 minutes by
> default.

this seems like something that's unreasonable to do on something exposed to the 
Internet. There's a very real probability that this will result in you being 
unable to access your router because it's always in this 'lockdown' mode. I 
don't object to the capability being there, but I do object to it being on by 
default, especially for such a long lockout period.

If you make the lockout per-IP then it may be reasonable, but this could result 
in a lot of IPs in your block list.

David Lang

> See the /etc/xinetd.conf and /etc/xinetd.d dir for details
> However this layer of defense is incomplete as several processes, notably the
> configuration gui, upnp, and so on are separate daemons with their own
> access controls.  Worse, many attacks nowadays come from the inside,
> and should be dealt with...
> Since we've been fiddling with ipsets on the bcp38 front it would be
> rather easy to hook up xinetd's mechanism with that to do the same
> blocking for *all* services from that specific IP. All it needs is a
> fork and exec in the sensor to run a script like this:
> #!/bin/sh
> # $1 = addr type (ipv4 or ipv6)
> # $2 = addr
> # $3 = timeout in seconds
> ipset add badboys-$1 $1 timeout $3
> ...
> and use the firewall rules to check that ipset for badboy IPs.
> the xinetd.org site is dead seemingly, but copies of the last release
> are widely available. Would probably be a very small patch if someone
> wants to
> take it on...
> is there anything else out there as tight and secure as xinetd for
> spawning network services or doing intrusion monitoring?

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