Prevent Certain LAN ips from accessing WAN when OpenVPN goes down

[phil.davis]

The advice from cmb should work - http://forum.pfsense.org/index.php/topic,58694.msg315225.html#msg315225
Post your "quick floating rule matching out on WAN" and we can try to sort out the detail of it.

[m3ki]

Hi Phil,

Thank you for your reply!
I am not at home at the moment.

But the rule I used was…
Anything on WAN interface, Direction OUT,coming from 192.168.1.5 - to Anywhere BLOCK <--- this didnt work.
I also tried same as above going to WAN Subnet. that didnt work either.

I tried packet capture and it seems that I only see my pings coming from 192.168.1.5 on LAN I am not sure if that helps.

Is there a documentation/diagram anywhere displaying how packets are traversed and in which order rules are applied?

Ig.

[GruensFroeschli]

Firewall rules are always applied to to down.
Firewall rules are always applied on the interface on which they come in (well, floating rules are an exception, but these are more complicated)
.
So to block traffic for your 192.168.1.5 on the LAN interface, you need to add the block rule on the LAN interface.

Now i'm not sure but i suspect that since your VPN interface is down, the rule which redirects traffic for your client doesn't apply anymore (don't take my word on this, i'm really not sure).

What i would do:

• Create an alias containing all your "is only allowed via VPN" clients. (Firewall–>Aliases). Lets call it VPN_USERS
• Change your redirect rule to: "source: VPN_USERS, gateway: VPN_gateway"
• Change the default allow all rule to: "source: NOT VPN_USERS"

In The end you would have 2 rules:
1: rule to allow VPN_USERS to the VPN, which forces traffic directly to the VPN gateway
2: rule to allow everyone except the VPN_USERS to wherever the routing table allows.

[m3ki]

Ahah ok that makes sense I guess it's possible I have to try that when I get home.

I tried this last night and it didnt work.
ALLOW source: 192.168.1.5, gateway: VPN_gateway <–- i assumed this would be skipped if vpn gateway is down.
BLOCK source: 192.168.1.5, anywhere < --- and this would be triggered
ALLOW source: lan, *

Is there a way to see which rules which packet hits?

[phil.davis]

On 2.1-RC1 the firewall log lets you display the rule number and description of the packets logged.
(I suspect that is new to 2.1, so won't be in 2.0.n - it is quickly getting to the point where 2.1 needs to get released and everyone upgrade, then we can all forget about what features might or might not be in 2.0.n)

[m3ki]

Is there a way to definitively know that a rule gets skipped if  VPN_gateway is down?

since this didnt work.
IN LAN TAB
ALLOW source: 192.168.1.5, gateway: VPN_gateway <–- i assumed this would be skipped if vpn gateway is down and would go to next rule.
BLOCK source: 192.168.1.5, anywhere < --- and this would be triggered
ALLOW source: lan, *

[m3ki]

Alright I tried rules below.
If 192.168.1.5 -> VPN is enabled and vpn gateway is down. Traffic from 192.168.1.5 still flows to ISP.
If the rule is disabled then 192.168.1.5 cannot ping anything.

So it seems that the moment the traffic is redirected to VPN gateway rest of the routing table is skipped.

Any ideas?


[kejianshi]

Well - What ports are needed for DNS, OpenVPN and little things like that?
You could close everything on LAN, and only allow from LAN subnet to pfsense LAN IP (lets call it 192.168.1.1 for simplicity)

That would kill all traffic to the NET.

Then you could allow only that 1 port that openvpn needs out from LAN 192.168.1.5 to *.

That should do it.  One would think.

(Is the vpn client on the computer 192.168.1.5, or is pfsense the client?)
This is easier to do if the computer in question is the client and not pfsense as client.

[m3ki]

That's the thing the moment traffic is redirected to VPN Gateway every other rule seems to be skipped.

I am trying to wrap my head around this:
Policy Route Negation
When a firewall rule directs traffic into the gateway, it bypasses the firewall's normal routing table. Policy route negation is just a rule that passes traffic to other local or VPN-connected networks that does not have a gateway set. By not setting a gateway on that rule it will bypass the gateway group and use the firewall's routing table. These rules should be at the top of the ruleset – or at least above any rules using gateways.

Am I supposed to create another rule somewhere ?

[kejianshi]

I'd just make the computer the client directly and that solves so many issues.
If its a windows machine or a MAC, this is really easy.  If its some server, maybe not as easy.

[m3ki]

Haha yeah… that would be simpler.

What I want is:

Have 3x machines -> ISP
TV -> flow to US VPN
NAS -> Some other VPN

If OpenVPN links go down BLOCK TV and NAS from accessing outside world.
I did this with DDWRT before but I have no idea how to do this with PFsense. I must be missing something simple.

[kejianshi]

OK - I want to be sure about this, so I'll list a list of conditions.  Tell me which are true or false for you.

Your distant VPN server uses a fixed IP?

If your VPN drops you want everything connected to pfsense to not be able to access internet?

[m3ki]

@kejianshi:

OK - I want to be sure about this, so I'll list a list of conditions.  Tell me which are true or false for you.

Your distant VPN server uses a fixed IP?
NO It's dynamic. Using OpenVPN Client in pfsense

If your VPN drops you want everything connected to pfsense to not be able to access internet?
No only machines forwarded to VPN Gateway

[kejianshi]

In that case, not sure…  I'll be reading along and thinking about it a while.

[kejianshi]

You posted a screen shot above.  I cant see the whole page.  Can you repost the screen shot to include the interface tabs etc?

[m3ki]

Here you go


[m3ki]

This can easily be done using iptables I just don't know how to do it here.

Idea is mark packets to go to either one routing table or another. then if packet still arrives to unwanted interface drop it. I have my iptables rules in earlier  posts.

[kejianshi]

The rules, as they are now, pass everything.  For sure.  First you pass 192.168.1.5, and then you pass everything that isn't 192.168.1.5.
So, that everything.

For the first one, shouldn’t you specify a destination gateway?

[m3ki]

Yeah sorry I was doing some other tests to see here are the rules as they are now. OpenVPN gateway is down and I can still ping outside from 192.168.1.5


[kejianshi]

So, if you put in a rule immediately after the pass 192.168.1.5 to olive rule and you made it a block 192.168.1.5 to anywhere rule, I wonder what that would do?

Second what is the subnet the VPN is using?  I have 1 last question after this…