Source address not NATed during OpenVPN startup?

bPsdTZpW

Another clue: if I change the NAT rule from LAN to WAN_IGB0 to use the WAN's IP address directly (e.g. w.x.y.z) instead of "interface address", the behavior is the same. This seems to indicate that the NAT rules aren't being used when the bad packets are passed.

stephenw10

Mmm, if if was NATing to the LAN IP or using the OBN rules at all you would see it in the created states.

Since it's being passed by a state opened on LAN you could try adding a block rule on LAN to prevent it as a workaround.

Steve

bPsdTZpW

@stephenw10 said in Source address not NATed during OpenVPN startup?:

Mmm, if if was NATing to the LAN IP or using the OBN rules at all you would see it in the created states.

Since it's being passed by a state opened on LAN you could try adding a block rule on LAN to prevent it as a workaround.

Steve

What block rule could I use? From the point of view of the LAN interface, the packets are perfectly OK (src:LAN device, dest:internet).

stephenw10

It's source: LANaddress destination: Internet though and it's outbound which should never happen.

You want to make it as specific as possible so I'd use a floating, quick, outbound rule, source: LANaddress destination: some-test-address. Make sure that does something useful and does block expected traffic before changing the destination to some thing wider.

Steve

bPsdTZpW

@stephenw10 said in Source address not NATed during OpenVPN startup?:

It's source: LANaddress destination: Internet though and it's outbound which should never happen.

You want to make it as specific as possible so I'd use a floating, quick, outbound rule, source: LANaddress destination: some-test-address. Make sure that does something useful and does block expected traffic before changing the destination to some thing wider.

Steve

I think I see. I already have a rule like this, and it doesn't work. From the original post:

I have put various "reject" floating rules on outbound WAN [by which I meant floating, WAN, outbound] to prevent these packets from exiting [1]...[1] e.g. action:block, quick, interface:WAN_IGB0, direction:out, family:IPV4+IPV6, protocol:any, source:RFC1918, destination:any, extra options:log, no advanced options.

I also tried putting such a rule on the LAN interface (out, reject, quick, src RFC1918, dest <test IP>) and, as expected, it did nothing.

stephenw10

Hmm, check the actual state as it appears in the state table. Try using pfctl -vvss

If it creates a state it should be possible to add a rule that prevents it.

Steve

bPsdTZpW

@stephenw10 said in Source address not NATed during OpenVPN startup?:

Hmm, check the actual state as it appears in the state table. Try using pfctl -vvss

If it creates a state it should be possible to add a rule that prevents it.

Steve

So after the bad packets have passed, pfctl -vvss gives many states of this form:

all tcp <website IP>:443 <- <LAN IP>:64970       CLOSED:SYN_SENT
   [0 + 16777216]  [1164774331 + 33554432]
   age 00:01:20, expires in 00:00:40, 1:1 pkts, 52:80 bytes, rule 122
   id: 4c80166200000000 creatorid: c79f1419 gateway: 0.0.0.0
   origif: igb1

which presumably correspond to some of the bad packets.

However, there are also a few state pairs that appear to correspond to working, NATed packets. The first state of the pair is very similar to the bad state, above, so I don't see how I could filter on it:

all tcp <website IP>:443 <- <LAN IP>:64972       TIME_WAIT:TIME_WAIT
   [4088558557 + 132096] wscale 7  [1887699560 + 1282998272] wscale 8
   age 00:01:20, expires in 00:01:13, 268:128 pkts, 27167:143271 bytes, rule 122
   id: 4d80166200000000 creatorid: c79f1419 gateway: 0.0.0.0
   origif: igb1

all tcp <WAN IP>:32245 (<LAN IP>:64972) -> <website IP>:443       ESTABLISHED:ESTABLISHED
   [3162374760 + 8323072] wscale 8  [4088558557 + 132096] wscale 7
   age 00:01:20, expires in 23:59:24, 268:128 pkts, 27167:143271 bytes, rule 74
   id: 4e80166200000000 creatorid: c79f1419 gateway: <WAN gateway>
   origif: igb0

This really seems like a bug.

stephenw10

It does. The only way I could possibly see anything sourced from the LAN IP itself would be some sort of proxy running. So Squid, HAProxy or NAT reflection in NAT+Proxy mode.

What is rule 122 in your ruleset?

Steve

bPsdTZpW

@stephenw10 said in Source address not NATed during OpenVPN startup?:

It does.

The only way I could possibly see anything sourced from the LAN IP itself would be some sort of proxy running. So Squid, HAProxy or NAT reflection in NAT+Proxy mode.

Nope, nope, and nope. The setup is quite vanilla. I have one package: service_watchdog.

What is rule 122 in your ruleset?

The only rule having any such number in the output of pfctl -vvsa is

@122(0) block drop in log quick on igb0 inet6 proto udp from any to any port = nameserver label "USER_RULE: Ports to monitor" ridentifier 1628204890
  [ Evaluations: 0         Packets: 0         Bytes: 0           States: 0     ]
  [ Inserted: pid 61558 State Creations: 0     ]

which makes not the least bit of sense. This is an inbound WAN block/log rule I use to see how many attempts at common ports the bad guys are making. Am I reading the numbers wrong?

stephenw10

Mmm, indeed. Can you see what rule 122 is or was when the OpenVPN is up?

This starts to look like a stale state somehow.

bPsdTZpW

@stephenw10 said in Source address not NATed during OpenVPN startup?:

Mmm, indeed. Can you see what rule 122 is or was when the OpenVPN is up?

That rule is from after OpenVPN came up. I don't know what the numbering was before it came up; it would be tricky to get; I'd probably need to write a script.

This starts to look like a stale state somehow.

Well, I did find that setting Reset All States in System/Advanced/Networking reduces (but does not zero) the number of bad packets.