[Openswan Users] Firewall rules for openswan behind NAT

Fred Weston fred.weston at lpga.com
Tue Nov 19 14:03:54 UTC 2013 

This is what I see in the log; it looks like it’s encrypting traffic but that doesn’t seem to be the case based upon the behavior I’m seeing.  If it is encrypting then the firewall in front of openswan should have no effect on the traffic I can pass over the tunnel as long as the tunnel is up.

Nov 19 14:00:55 ip-10-0-0-82 pluto[12517]: "vpc1-to-vpc2" #1: NAT-Traversal: Result using RFC 3947 (NAT-Traversal): both are NATed
Nov 19 14:00:55 ip-10-0-0-82 pluto[12517]: "vpc1-to-vpc2" #1: transition from state STATE_MAIN_I2 to state STATE_MAIN_I3
Nov 19 14:00:55 ip-10-0-0-82 pluto[12517]: "vpc1-to-vpc2" #1: STATE_MAIN_I3: sent MI3, expecting MR3
Nov 19 14:00:55 ip-10-0-0-82 pluto[12517]: "vpc1-to-vpc2" #1: received Vendor ID payload [CAN-IKEv2]
Nov 19 14:00:55 ip-10-0-0-82 pluto[12517]: "vpc1-to-vpc2" #1: Main mode peer ID is ID_IPV4_ADDR: '50.18.211.121'
Nov 19 14:00:55 ip-10-0-0-82 pluto[12517]: "vpc1-to-vpc2" #1: transition from state STATE_MAIN_I3 to state STATE_MAIN_I4
Nov 19 14:00:55 ip-10-0-0-82 pluto[12517]: "vpc1-to-vpc2" #1: STATE_MAIN_I4: ISAKMP SA established {auth=OAKLEY_PRESHARED_KEY cipher=aes_128 prf=oakley_sha group=modp2048}
Nov 19 14:00:55 ip-10-0-0-82 pluto[12517]: "vpc1-to-vpc2" #2: initiating Quick Mode PSK+ENCRYPT+TUNNEL+PFS+UP+IKEv2ALLOW+SAREFTRACK {using isakmp#1 msgid:463435ec proposal=defaults pfsgroup=OAKLEY_GROUP_MODP2048}
Nov 19 14:00:56 ip-10-0-0-82 pluto[12517]: "vpc1-to-vpc2" #2: transition from state STATE_QUICK_I1 to state STATE_QUICK_I2
Nov 19 14:00:56 ip-10-0-0-82 pluto[12517]: "vpc1-to-vpc2" #2: STATE_QUICK_I2: sent QI2, IPsec SA established tunnel mode {ESP=>0x54dd12fe <0x2bb3e074 xfrm=AES_128-HMAC_SHA1 NATOA=none NATD=50.18.211.121:4500 DPD=none}

From: Nick Howitt [mailto:n1ck.h0w1tt at gmail.com]
Sent: Tuesday, November 19, 2013 8:21 AM
To: Fred Weston
Cc: users at lists.openswan.org
Subject: RE: [Openswan Users] Firewall rules for openswan behind NAT


What are you getting in /var/log/secure - just the bit where the tunnel is negotiating, not the bit where ipsec loads?

Also what do you have in the "config setup" sections of your conf files?

On 2013-11-19 13:14, Fred Weston wrote:
So here’s something interesting…this morning just for the heck of it, I added ICMP to the permit list and that immediately got ping working.

Since the tunnel shouldn’t require ICMP, that got me thinking that the traffic isn’t actually being encrypted.  I verified that by trying to remote desktop to a host on the far side of the tunnel.  It didn’t work when I have the firewall rules set to only allow the few ports/protocols the tunnel should need, but as soon as I changed the ruleset to permit all traffic RDP worked, so it seems the problem is actually that the tunnel isn’t encrypting the traffic.

I’m not quite sure why this is.

Here are the configs from each side, can someone comment as to what I need to add to get the traffic to be encrypted?

conn vpc1-to-vpc2
        type=tunnel
        authby=secret
        left=%defaultroute
        leftid=107.21.17.86
        leftnexthop=%defaultroute
        leftsubnet=10.0.0.0/16
        leftsourceip=10.0.0.82
        right=50.18.211.121
        rightsubnet=10.1.0.0/16
        pfs=yes
        auto=start
        phase2=esp

conn vpc2-to-vpc1
        type=tunnel
        authby=secret
        left=%defaultroute
        leftid=50.18.211.121
        leftnexthop=%defaultroute
        leftsubnet=10.1.0.0/16
        leftsourceip=10.1.0.67
        right=107.21.17.86
        rightsubnet=10.0.0.0/16
        pfs=yes
        auto=start
        phase2=esp



From: Nick Howitt [mailto:n1ck.h0w1tt at gmail.com]
Sent: Tuesday, November 19, 2013 5:19 AM
To: Fred Weston
Cc: users at lists.openswan.org<mailto:users at lists.openswan.org>
Subject: RE: [Openswan Users] Firewall rules for openswan behind NAT


Yes, I was picturing firewalling in the hosts.

Have a look in the logs and see if Openswan is connecting with or without NAT-T when your firewall is not up. Then, with your firewalling, try forceencaps=yes in the conn and nat_traversal=yes in config setup.

For minor tunnel info I use "service ipsec status", but it depends on your distro and the information is almost useless. You can also have a look at "ip xfrm" and "ip route".

Nick

On 2013-11-19 10:03, Fred Weston wrote:
I think you’re picturing the firewalling taking place on the openswan hosts, which isn’t the case.  There isn’t a firewall on either openswan box (other than any standard firewall that may be enabled by default).  The firewall rules I am manipulating are in the network / NAT device in front of openswan.  Since the tunnel works when I permit all traffic to openswan, that would seem to discount the possibility of any firewall issues on the hosts themselves.

I’ll take a look at the logs to see if they show anything interesting.  Is there a utility that will show tunnel status?

From: Nick Howitt [mailto:n1ck.h0w1tt at gmail.com]
Sent: Tuesday, November 19, 2013 3:44 AM
To: Fred Weston
Cc: users at lists.openswan.org<mailto:users at lists.openswan.org>
Subject: RE: [Openswan Users] Firewall rules for openswan behind NAT


For your rules, I was hoping for something like the output to "iptables -L -n -v" and "iptables -t nat -L -n -v" rather than a description of the rules.

Forceencaps is unlikely but can be useful

Openswan/ipsec logs are typically found in /var/log/secure depending on your system. If you have dpd enabled you should see constant tunnel renegotiation if the tunnel has gone down. You'll see nothing odd if the tunnel is up but no traffic is passing. When the tunnel is up you should see in the logs something like "IPSec SA Established". Available status information is not particulrly helpful.

Can you also try adding a firewall rule something like:

iptables -t nat -I POSTROUTING -m policy --dir out --pol ipsec -j ACCEPT

Either that or somthing in the post routing chain which allows traffic between the local and remote subnets, but this rule is more flexible as you don't need to specify the subnets.

Nick

On 2013-11-18 23:28, Fred Weston wrote:

From: users-bounces at lists.openswan.org<mailto:users-bounces at lists.openswan.org> [mailto:users-bounces at lists.openswan.org] On Behalf Of Nick Howitt

Can you post the exact rules you are using?

I included those in my original message.
*:* > UDP 500
*:* > UDP 4500
* > IP Protocol 50
* > IP Protocol 51

Also have you tried forcing encapsulation with forceencaps=yes in your conns?

No, I haven’t tried that.

When you say "things stop working" does the tunnel come down, or does traffic just fail to pass?

I’m not sure how to tell the difference, my test methodology was to ping a host on the far side of the tunnel and when I change the firewall rules from wide open to those above the ping starts timing out.  How can I tell what state the tunnel is in?

Regards,

Nick

On 2013-11-17 17:13, Fred Weston wrote:
Does anyone else have any suggestions?  I would like to implement this in production but I am hesitant to do so when the only way I can get it to work is permit all traffic from the Internet into the openswan boxes.

From: users-bounces at lists.openswan.org<mailto:users-bounces at lists.openswan.org> [mailto:users-bounces at lists.openswan.org] On Behalf Of Fred Weston
Sent: Wednesday, November 13, 2013 11:49 AM
To: Leto
Cc: users at lists.openswan.org<mailto:users at lists.openswan.org>
Subject: Re: [Openswan Users] Firewall rules for openswan behind NAT

Let me clarify – when I reference ports/protocols that I’m allowing inbound, I’m allowing it from the opposite host and not specifying a source port.

Thanks,
FW





From: Leto [mailto:letoams at gmail.com]
Sent: Wednesday, November 13, 2013 11:27 AM
To: Fred Weston
Cc: users at lists.openswan.org<mailto:users at lists.openswan.org>
Subject: Re: [Openswan Users] Firewall rules for openswan behind NAT



sent from a tiny device

On 2013-11-13, at 10:44, Fred Weston <fred.weston at lpga.com<mailto:fred.weston at lpga.com>> wrote:
Hello All,

I’m using OpenSwan with AWS to link two private VPC networks in different regions.

I’m having trouble getting my firewall ACLs right.  Everything works if I permit all traffic to the OpenSwan boxes, however when I try to get more restrictive and permit only the necessary ports things stop working.

One side has all traffic permitted inbound for the time being and I’m making ACL changes trying to restrict traffic to certain ports/protocols on the other side.

Both endpoints are behind 1:1 NAT.  Everything is permitted outbound on both sides.

From reading online, I understand that the following ports and protocols should be all I need:

UDP 500
UDP 4500
IP Protocol 50
IP Protocol 51

I tried the above and had no luck.  As soon as I change from permitting all inbound to permitting only the above list the tunnel comes down.

You should really allow icmp.

Note that you need to accept from a random high port to dest udp 4500, not just 4500 <-> 4500. Same for 500




I also tried permitting tcp/1721 and tcp/1723 and IP Protocol 47.

I am using AWS ‘security groups’ to control filtering and according to the docs (and my observations) security groups are stateful, so I am not sure why this isn’t working.

Can anyone offer any suggestions?


Thanks,

Fred Weston





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