[Openswan Users] Firewall rules for openswan behind NAT

Wed Nov 20 22:05:41 UTC 2013

Yes, exactly that.  I am confused for the same reason.  It also applies to other traffic types i.e. smb, rdp, etc.  If I don’t permit it into openswan then it doesn’t work and that makes absolutely no sense to me.

From: Nick Howitt [mailto:n1ck.h0w1tt at gmail.com]
Sent: Wednesday, November 20, 2013 5:03 PM
To: Fred Weston; neal.p.murphy at alum.wpi.edu; users at openswan.org
Subject: Re: [Openswan Users] Firewall rules for openswan behind NAT

Both traceroutes are going through the tunnel (no WAN IP hops). I don't understand why blocking ICMP at the gateway blocks these. Totally confused. :-(       What about other traffic?
On 20/11/2013 21:49, Fred Weston wrote:
Sorry, I didn’t see your request for traceroutes.

Here are traceroutes from a host behind openswan in site 1 to a host behind openswan in site 2 and vice versa.  They look like I expect them to work, however they only work when I allow ICMP into openswan from the Internet.

Tracing route to aws-useast-sp1.lpgaoffice.local [10.0.0.146]
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  aws-uswest-nat.lpgaoffice.local [10.1.0.67]
  2    85 ms    84 ms    99 ms  aws-useast-nat.lpgaoffice.local [10.0.0.82]
  3    84 ms    84 ms    84 ms  AWS-USEAST-SP1 [10.0.0.146]

Trace complete.

Tracing route to aws-uswest-sp1.lpgaoffice.local [10.1.0.38]
over a maximum of 30 hops:

  1     1 ms    <1 ms    <1 ms  aws-useast-nat.lpgaoffice.local [10.0.0.82]
  2    84 ms    84 ms    84 ms  aws-uswest-nat.lpgaoffice.local [10.1.0.67]
  3    84 ms    84 ms    84 ms  sprestore.lpga.com [10.1.0.38]

Trace complete.

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
Sent: Wednesday, November 20, 2013 4:20 PM
To: neal.p.murphy at alum.wpi.edu<mailto:neal.p.murphy at alum.wpi.edu>; users at openswan.org<mailto:users at openswan.org>
Subject: Re: [Openswan Users] Firewall rules for openswan behind NAT

As I said before, tunnel status is almost impossible to obtain.

You can see the encryption being used in /var/log/secure. You are using AES128, modp2048 and SHA1 which is OK

Your conns look absolutely fine and your tunnel is up. You have not explicitly defined the encryption so it has chosen a reasonable one (similar in strength to 3des but uses 1/3 cpu cycles). You don't need virtual_private with your set up and you don't need protocols 50 and 51 through the firewall as ipsec with NAT-T is working.

Neal's summary was pretty much spot on.

Can you confirm you don't have a blank line after conn ...... and before type=tunnel in your conf files?

Can you do the traceroutes/tracerts I asked for?

Nick
On 20/11/2013 20:07, Neal Murphy wrote:

On Wednesday, November 20, 2013 02:48:11 PM Fred Weston wrote:

All of this makes sense to me and I believe I have crossed everything you

listed off my troubleshooting list.

Is there a way to see the status of the tunnel and what crypto is being

used to transmit packets between LANs?

If openswan is running on GNU/Linux and you are using KLIPS,

  cd /proc/net

  for i in ipsec_*; do

    echo $i

    sed -e 's/^/  /' $i

  done

And peruse /proc/net/ipsec/.

To obtain a deluge of info, '/usr/sbin/ipsec barf'.

-----Original Message-----

From: users-bounces at lists.openswan.org<mailto:users-bounces at lists.openswan.org>

[mailto:users-bounces at lists.openswan.org] On Behalf Of Neal Murphy Sent:

Wednesday, November 20, 2013 2:12 PM

To: users at openswan.org<mailto:users at openswan.org>

Subject: Re: [Openswan Users] Firewall rules for openswan behind NAT

You've addressed some or most of what's in the following bird's-eye view;

it shouldn't hurt to review in case you've overlooked something.

You need to forward UDP ports 500 and 4500 on each firewall to the local

openswan box (limit it to coming from the remote IP/openswan box for added

security), and allow UDP ports 500 and 4500 out from the local openswan

box (preferably limit it to going to the remote openswan box for added

security). This will allow either end to start the VPN. Each firewall

should drop packets destined for the remote LAN(s) since they don't know

how to reach them. Logging them with a specific prefix would make it easy

to discover malconfigured nodes.

I don't believe protocols 50 and 51 are used when NAT-T is used.

Each internal node must have an explicit route to the remote LAN via the

local openswan box's IP.

Each openswan box needs route(s) to the local internal LAN(s) and a default

route via the local firewall's internal IP address. Openswan takes care of

adding/removing routes to remote LANs when it brings VPNs up and down.

Do you have a 'config setup' in each ipsec.conf, possibly similar to:

        protostack=klips     # or netkey or mast

        interfaces=%defaultroute

        klipsdebug=none

        plutodebug=none

        plutowait=no

        uniqueids=yes

        nat_traversal=yes

You might need a virtual_private declaration describing your internal LANs,

but probably not, since you aren't using a road warrior setup.

In each conn spec, you may need to specify ike= and esp=; that is, tell

openswan which encrytpion to use. I don't know what happens if you don't

specify any encryption methods. (Does openswan then transmit in the

clear?)

I haven't played with NAT Traversal lately; I forget how to configure a

conn to make NAT-T work.

N

On Wednesday, November 20, 2013 12:28:35 PM Fred Weston wrote:

I cannot ping LAN-LAN without the tunnel.

In site A I have 10.0.0.0/16 and in site B I have 10.1.0.0/16.  In

each site the routing table has an entry for the opposite site’s IP

space which is pointed at the local openswan box.

I think we are confusing firewall and tunnel terminology.  The

firewall I am speaking of is builtin to AWS and controls ingress and

egress traffic from the openswan boxes.  It is something that is part

of the AWS network stack and the only thing I can do to it is change its

ruleset.

The traffic between sites is traversing the openswan tunnel, however

when it’s doing so it isn’t being encrypted, so for instance when I

send RDP traffic across the tunnel, the AWS firewall sees RDP traffic

and doesn’t let it through.  If the tunnel were encrypting traffic,

all the AWS firewall should see is UDP traffic coming into port 500

and it should have no idea what that traffic is, but it’ll allow it

because I’ve told it to permit udp/500 inbound.

In the diagram below I’ve notated where the AWS firewall at each site

is inspecting traffic.  The issue is that the traffic coming across

the tunnel is in the clear.

[cid:image002.jpg at 01CEE5EC.06F0A5C0]

From: Nick Howitt [mailto:n1ck.h0w1tt at gmail.com]

Sent: Wednesday, November 20, 2013 3:36 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

I am curious that your are even pinging LAN-LAN outside the tunnel.

You have private subnets and the internet would not know where to find

a 10.x.y.z address. Can you do a tracert/traceroute end to end with

and without the firewall?

On your gateways to you have routes set up to your far LAN's via your

Openswan devices?

Can you ping from 10.0.0.82 to 10.1.0.67 or vice-versa with the

firewall up and down?

On 2013-11-19 17:14, Fred Weston wrote:

The tunnel comes up either way but I can't ping unless I permit icmp

from the Internet into openswan.  I'm pinging from another device

behind openswan.

Thanks ,

FW

On Nov 19, 2013, at 11:40 AM, "Nick Howitt"

<n1ck.h0w1tt at gmail.com<mailto:n1ck.h0w1tt at gmail.com><mailto:n1ck.h0w1tt at gmail.com><mailto:n1ck.h0w1tt at gmail.com>> wrote:

OK that shows the tunnel is up. Is that with or without the firewall

(and btw it is using NAT-T so you should not need protocols 50 and 51

through your firewall).

When you are pinging end to end, is that from the openswan device or

from another LAN device?

On 2013-11-19 14:03, Fred Weston wrote:

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<mailto:users at lists.openswan.org><mailto:users at lists.openswan.org><mailto: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><mailto: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><mailto: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.o<mailto:users-bounces at lists.openswan.org>

rg><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.o<mailto:users-bounces at lists.openswan.org>

rg><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><mailto: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><mailto: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><mailto: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?

_______________________________________________

Users at lists.openswan.org<mailto:Users at lists.openswan.org>

https://lists.openswan.org/mailman/listinfo/users

Micropayments: https://flattr.com/thing/38387/IPsec-for-Linux-made-easy

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The information transmitted in this message (including any attachments) is intended only for the use of the individual(s) and/or entity(ies) to which it is addressed and may contain confidential business information which should not be disclosed. If you are not the intended recipient, you are not authorized to read, print, retain, copy or disseminate this message or any part of it. If you have received this email in error, please notify the sender and immediately destroy and delete this email from your system without disseminating it. E-mail transmission cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses. The sender therefore does not accept liability for any errors or omissions in the contents of this message. Any views or opinions presented in this e-mail are solely those of the author and do not necessarily represent those of the LPGA and/or its affiliates. No employee is authorized to conclude any binding agreement on behalf of LPGA and/or its affiliates with another party by e-mail. All agreements shall be contained in a separate writing executed by an authorized LPGA signatory. Thank You.
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