[K12OSN] Block internet access on thinclient side

[James P. Kinney III]

Ugh. Still blinked and missed the foobar.

iptables -A PREROUTING -t nat -s 127.0.0.1 -m tcp -p tcp --dport 80 -j
DNAT --to-destination 192.168.0.80:8080

The -I means to "insert" a rule and a required rule number must be next.
Without the rule number, nothing happens (as you have seen :-) -A means
to append to the list. I've spent the last several day doing inserts and
that is the current personal default :) sorry for the slip.

On Tue, 2008-04-01 at 14:12 +0100, Brian Chivers wrote:
> OK being really stupid today :-(
> 
> I've done
> 
> iptables -I PREROUTING -t nat -s 127.0.0.1 -m tcp -p tcp --dport 80 -j DNAT --to-destination 
> 192.168.0.80:8080
> 
> If I then do a
> 
> iptables --list
> 
> Nothing shows up, do I have to save it in some way ??
> 
> In /etc/sysconfig there is a file called iptables, can I just add it to that ??
> 
> Sorry I'm being really slow about this :-/
> 
> Brian
> 
> James P. Kinney III wrote:
> > Sorry. sleep deprivation. change REDIRECT to DNAT
> > 
> > For a full discussion of all the parts of iptables, man iptables tells
> > all. But it is quite overwhelming :)
> > 
> > For a great book on Linux Security, get Real World Linux Security by Bob
> > Toxen (I know him personally - he was one of the small team that ported
> > unix to the SGI MIPS platform back when dinosaurs...). 
> > On Tue, 2008-04-01 at 10:36 +0100, Brian Chivers wrote:
> >> Just tried this and got the error below
> >>
> >> iptables -I PREROUTING -t nat -s 127.0.0.1 -m tcp -p tcp --dport 80 -j REDIRECT --to-destination 
> >> 192.168.0.80:8080
> >>
> >> iptables v1.3.5: Unknown arg `--to-destination'
> >> Try `iptables -h' or 'iptables --help' for more information.
> >>
> >>
> >> Help :-)
> >> Brian
> >>
> >>
> >> James P. Kinney III wrote:
> >>> Hi Brian,
> >>>
> >>> It is quite easy to do what you need. The thin clients all run their web
> >>> browser on the server so only the thin client servers need to be
> >>> adjusted. iptables is the correct way to do it because proxy settings in
> >>> user configs can be changed.
> >>>
> >>> iptables -I PREROUTING -t nat -s 127.0.0.1 -m tcp -p tcp --dport 80 -j
> >>> REDIRECT --to-destination <ip of proxy>:<port of proxy>
> >>>
> >>> Repeat that for all other port traffic you need by just changing the 80.
> >>>
> >>> You can save the final configuration with iptables-save >
> >>> iptables-saved-file
> >>> and restore with iptables-restore iptables-saved-file
> >>> On Mon, 2008-03-31 at 12:09 +0100, Brian Chivers wrote:
> >>>> I'd like to block all access to the outside network / internet from our thinclients unless they go 
> >>>> via the our proxy server. I have installed a global extension for firefox that has setup it up how I 
> >>>> want with proxy's and bookmarks etc for all users but if you change the connection setting to 
> >>>> "direct" you go straight out bypassing everything.
> >>>>
> >>>> I could setup our main firewall to block the thinclient server completely but it is very useful to 
> >>>> have full connectivity on it for things like freenx and updates.
> >>>>
> >>>> Is it possible to setup the iptables on the k12ltsp box itself to drop or redirect all connects from 
> >>>> the thinclient side and only allow the important ones for things like the initial booting ?
> >>>>
> >>>> I've never played with iptables before any useful pointers would be gratefully received.
> >>>>
> >>>> Thanks
> >>>> Brian Chivers
> >>>> Portsmouth College
> >>>>
> >>>> ------------------------------------------------------------------------------------------------
> >>>>     The views expressed here are my own and not necessarily
> >>>>  
> >>>>                 the views of Portsmouth College    
> >>>>
> >>>> _______________________________________________
> >>>> K12OSN mailing list
> >>>> K12OSN at redhat.com
> >>>> https://www.redhat.com/mailman/listinfo/k12osn
> >>>> For more info see <http://www.k12os.org>
> >>>>
> >>
> >> ------------------------------------------------------------------------------------------------
> >>     The views expressed here are my own and not necessarily
> >>  
> >>                 the views of Portsmouth College    
> >>
> >> _______________________________________________
> >> K12OSN mailing list
> >> K12OSN at redhat.com
> >> https://www.redhat.com/mailman/listinfo/k12osn
> >> For more info see <http://www.k12os.org>
> >>
> 
> 
> ------------------------------------------------------------------------------------------------
>     The views expressed here are my own and not necessarily
>  
>                 the views of Portsmouth College    
> 
> _______________________________________________
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> K12OSN at redhat.com
> https://www.redhat.com/mailman/listinfo/k12osn
> For more info see <http://www.k12os.org>
> 
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-- 
James P. Kinney III          
CEO & Director of Engineering 
Local Net Solutions,LLC        
770-493-8244                    
http://www.localnetsolutions.com

GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
<jkinney at localnetsolutions.com>
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