This is a collection of questions and answers, mostly taken from the FreeS/WAN mailing list. See the project web site for more information. All the FreeS/WAN documentation is online there.
Contributions to the FAQ are welcome. Please send them to the project mailing list.
For more detail, see our introduction document or the FreeS/WAN project web site.
Use the mailing list for problem reports, rather than mailing developers directly. This gives you access to more expertise, including users who may have encountered and solved the same problems. In particular, for problems involving interoperation with another IPSEC implementation, the users often know more than the developers.
Using the list may also be important in relation to various cryptography export laws. A US citizen who provides technical assistance to foreign cryptographic work might be charged under the arms export regulations. Such a charge would be easier to defend if the discussion took place on a public mailing list than if it were done in private mail.
If you want the help of a contractor, or to hire staff with FreeS/WAN expertise, you could:
For companies offerring support, see the next question.
Various companies specialize in commercial support of open source software. Our project leader was a founder of the first such company, Cygnus Support. It has since been bought by Redhat. Another such firm is Linuxcare.
In practice, it is considerably more complex. We have a whole interop document devoted to it.
In general, new versions will use existing configuration files, at least until the next major version number change. For example, 1.8 can use files created for 1.7, 1.6, even back to 1.0, but not from 0.92. This behaviour will continue until we release 2.0.
As of 1.8, however, conf file checking has become stricter, so that an error that may have slipped past the checks in an earlier version may be caught in a later one. From 1.8's doc/CHANGES:
The internal configuration-file reader is progressively getting fussier about what it will accept, which may cause problems for illegal ipsec.conf files whose sins previously passed unnoticed. IN PARTICULAR, the "auto" parameter's values are now checked for legality everywhere.
FreeS/WAN is intended to run on all CPUs Linux supports. As of June 2000, we know of it being used in production on x86, ARM, Alpha and MIPS. It has also had successful tests on PPC and SPARC, though we don't know of actual use there. Details are in our compatibility document.
FreeS/WAN has been tested on multiprocessor Intel Linux and worked there. Note, however, that we do not test this often and have never tested on multiprocessor machines of other architectures.
The GMP library is included in most Linux distributions. Typically, there are two RPMs, libgmp and libgmp-devel, You need to install both, either from your distribution CDs or from your vendor's web site.
On Debian, a mailing list message reports that the command to give is
For more information and the latest version, see the GMP home page.
Setup and configuration of FreeS/WAN are covered in other documentation sections:
However, we also list some of the commonest problems here.
The standard subnet-to-subnet tunnel protects traffic only between the subnets. To test it, you must use pings that go from one subnet to the other.
For example, suppose you have:
subnet a.b.c.0/24 | eth1 = a.b.c.1 gate1 eth0 = 1.2.3.4 | ~ internet ~ | eth0 = 4.3.2.1 gate2 eth1 = x.y.z.1 | subnet x.y.z.0/24and the connection description:
conn abc-xyz left=1.2.3.4 leftsubnet=a.b.c.0/24 right=4.3.2.1 rightsubnet=x.y.z.0/24You can test this connection description only by sending a ping that will actually go through the tunnel. Assuming you have machines at addresses a.b.c.2 and x.y.z.2, pings you might consider trying are:
Only the first of these is a useful test of this tunnel. The others do not use the tunnel. Depending on other details of your setup and routing, they:
If required, you can of course build additional tunnels so that all the machines involved can talk to all the others. See multiple tunnels in the configuration document for details.
Almost always, these turn out to involve failure of a DNS lookup. The timeouts waiting for DNS are typically set long so that you won't time out when a query involves multiple lookups or long paths. Genuine failures therefore produce long delays before they are detected.
A mailing list message from project technical lead Henry Spencer:
> ... when i run /etc/rc.d/init.d/ipsec start, i get: > ipsec_setup: Starting FreeS/WAN IPSEC 1.5... > and it just sits there, doesn't give back my bash prompt. Almost certainly, the problem is that you're using DNS names in your ipsec.conf, but DNS lookups are not working for some reason. You will get your prompt back... eventually. But the DNS timeouts are long. Doing something about this is on our list, but it is not easy.
In the meanwhile, we recommend that connection descriptions in ipsec.conf(5) use numeric IP addresses rather than names which will require a DNS lookup.
Names that do not require a lookup are fine. For example:
These are fine. The @ sign prevents any DNS lookup. However, do not attempt to give the gateway address as left=camelot.example.org. That requires a lookup.
A post from one user after solving a problem with long delays:
Subject: Final Answer to Delay!!! Date: Mon, 19 Feb 2001 From: "Felippe Solutions" <felippe@solutionstecnologia.com.br> Sorry people, but seems like the Delay problem had nothing to do with freeswan. The problem was DNS as some people sad from the beginning, but not the way they thought it was happening. Samba, ssh, telnet and other apps try to reverse lookup addresses when you use IP numbers (Stupid that ahh). I could ping very fast because I always ping with "-n" option, but I don't know the option on the other apps to stop reverse addressing so I don't use it.This post is fairly typical. These problems are often tricky and frustrating to diagnose, and most turn out to be DNS-related.
One suggestion for diagnosis: test with both names and addresses if possible. For example, try all of:
If these behave differently, the problem must be DNS-related since the three commands do exactly the same thing except for DNS lookups.
IPsec tunnels are not just virtual wires; they are virtual wires with built-in access controls. Negotiation of an IPsec tunnel includes negotiation of access rights for it, which don't include packets to/from other IP addresses. (The protocols themselves are quite inflexible about this, so there are limits to what we can do about it.)For fairly obvious security reasons, and to comply with the IPSEC RFCs, KLIPS drops any packets it receives that are not allowed on the tunnels currently defined. So if you send it packets with route(8), and suitable tunnels are not defined, the packets vanish. Whether this is reported in the logs depends on the setting of klipsdebug in your ipsec.conf(5) file.
To rescue vanishing packets, you must ensure that suitable tunnels for them exist, by editing the connection descriptions in ipsec.conf(5). For example, supposing you have a simple setup:
leftsubnet -- leftgateway === internet === roadwarriorIf you want to give the roadwarrior access to some resource that is located behind the left gateway but is not in the currently defined left subnet, then the usual procedure is to define an additional tunnel for those packets by creating a new connection description.
In some cases, it may be easier to alter an existing connection description, enlarging the definition of leftsubnet. For example, instead of two connection descriptions with 192.168.8.0/24 and 192.168.9.0/24 as their leftsubnet parameters, you can use a single description with 192.168.8.0/23.
If you have multiple endpoints on each side, you need to ensure that there is a route for each pair of endpoints. See our configuration document for an example.
When a tunnel goes away, either because negotiations with the other
gateway failed or because you gave an
This is a documented design decision, not a bug. FreeS/WAN must not automatically adjust things to send packets via another route. The other route might be insecure.
Of course, re-routing may be necessary in many cases. In those cases,
you have to do it manually or via scripts. We provide the
From ipsec_auto(8):
Normally, pluto establishes a route to the destination specified for a connection as part of the --up operation. However, the route and only the route can be established with the --route operation. Until and unless an actual connection is established, this discards any packets sent there, which may be preferable to having them sent elsewhere based on a more general route (e.g., a default route).See also this mailing list message.Normally, pluto's route to a destination remains in place when a --down operation is used to take the connection down (or if connection setup, or later automatic rekeying, fails). This permits establishing a new connection (perhaps using a different specification; the route is altered as necessary) without having a ``window'' in which packets might go elsewhere based on a more general route. Such a route can be removed using the --unroute operation (and is implicitly removed by --delete).
then IPSEC cannot work. The first thing to check if packets seem to be vanishing is the firewall rules on the two gateway machines and any other machines along the path that you have access to.
For details, see our document on firewalls.
Networks being what they are, IPSEC connections can be broken for any number of reasons, ranging from hardware failures to various software problems such as the path MTU problems discussed elsewhere in the FAQ. Fortunately, various diagnostic tools exist that help you sort many of the possible problems.
There is one situation, however, where FreeS/WAN (using default settings) may destroy a connection for no readily apparent reason. This occurs when things are misconfigured so that two tunnels from the same gateway expect the same subnet on the far end.
In this situation, the first tunnel comes up fine and works until the second is established. At that point, because of the way we track connections internally, the first tunnel ceases to exist as far as this gateway is concerned. Of course the far end does not know that and a storm of error messages appears on both systems as it tries to use the tunnel.
If the far end gives up, goes back to square one and negotiates a new tunnel, then that wipes out the second tunnel and ...
The solution is simple. Do not build multiple conn descriptions with the same remote subnet.
This is actually intended to be a feature, rather than a bug. Consider the situation where a single remote system goes down, then comes back up and reconnects to the gateway. It is useful to have the gateway tear down the old tunnel and recover resources when the reconnection is made. It recognises that situation by checking the remote subnet for each tunnel it builds and discarding duplicates. This works fine as long as you don't configure multiple tunnels with the same remote subnet.
If this behaviour is inconvenient for you, you can disable it by setting
uniqueids=no in ipsec.conf(5).
At one point, this problem was quite severe. On more recent systems,
the problem has been solved. The version of tcpdump
shipped with Redhat 6.2, for example, understands IPSEC well enough
to be usable on a gateway. If in doubt about your version of tcpdump,
you can get the latest version from tcpdump.org.
Even if you have a version of tcpdump that works on gateways however, the most
certain way to examine IPSEC packets is to look at them on the wire. For security,
you need to be certain, so we recommend doing that. To do so, you need a
separate sniffer machine located between the two gateways.
This machine can be routing IPSEC packets, but it must not be an IPSEC gateway.
A common test setup is to put a machine with dual Ethernet cards in
between two gateways under test. The central machine both routes
packets and provides a place to safely run tcpdump or other sniffing
tools. What you end up with looks like:
With p and q any convenient values that do not interfere with other
routes you may have. The ipsec.conf(5) file then has, among other things:
Note that nothing on either subnet needs to change. This lets you
test most of your IPSEC setup before connecting to the insecure
Internet.
It is often useful in debugging to test things one at a time:
FreeS/WAN releases are tested for all of these, so you can be reasonably
certain they can do them all. Of course, that does not mean they
will on the first try, especially if you have some unusual configuration.
The rest of this section gives information on diagnosing the problem
when each of the above steps fails.
Suspect one of:
Each connection must be identified by a unique SPI value.
For automatic connections, these values are assigned automatically. For manual
connections, you must set them with spi= statements in
ipsec.conf(5).
Each manual connection must have a unique SPI value in the range 0x100 to 0x999.
Two or more with the same value will fail. For details, see our HTML doc section
Using manual keying in production and the
man page ipsec.conf(5).
Other possibilities:
If tests with ping(1) and a small packet size succeed, but tests or
transfers with larger packet sizes fail, suspect problems with
path MTU discovery.
IPSEC makes packets larger by adding an ESP or AH header. This can tickle
assorted bugs in path MTU discovery mechanisms and cause a variety of
annoying symptoms. Here is one example of a discussion of this problem off
the mailing list:TCPdump on the gateway shows strange things
Attempting to look at IPSEC packets by running monitoring tools on the IPSEC
gateway machine can produce silly results. That machine is mangling the packets
for IPSEC, and possibly for firewall or NAT purposes as well. If the internals
of the machine's IP stack are not what the monitoring tool expects, then the
tool can misinterpret them and produce nonsense output.
Testing network
subnet a.b.c.0/24
|
eth1 = a.b.c.1
gate1
eth0 = 192.168.p.1
|
|
eth0 = 192.168.p.2
route/monitor box
eth1 = 192.168.q.2
|
|
eth0 = 192.168.q.1
gate2
eth1 = x.y.z.1
|
subnet x.y.z.0/24
conn abc=xyz
left=192.168.p.1
leftnexthop=192.168.p.2
right=192.168.q.1
rightnexthop=192.168.q.2
Once that works, you can remove the "route/monitor box", and connect
the two gateways to the Internet. The only parameters in ipsec.conf(5)
that need to change are the four shown above. You replace them with
values appropriate for your Internet connection, and change the eth0
IP addresses and the default routes on both gateways.
Testing in stages
Manually keyed connections don't work
e.g. incorrect interface or next hop informationOne manual connection works, but second one fails
This is fairly common problem when attempting to configure multiple manually keyed
connections from a single gateway.
Manual connections work, but automatic keying doesn't
The most common reason for this behaviour is a firewall dropping the UDP port 500
packets used in key negotiation.
IPSEC works, but connections using compression fail
Suspect one of:
Small packets work, but large transfers fail
Date: Mon, 3 Apr 2000
From: "Michael H. Warfield" <mhw@wittsend.com>
Paul Koning wrote:
> Chris> It appears that the Osicom router discards IP
> Chris> fragments...
> Amazing. A device that discards fragments isn't a router, it's at
> best a boat anchor.
It may not be exactly what it appears. I ran into a similar problem
with an ISDN link a while ago giving similar symptoms. Turned out that
the device was negotiating an MTU that it really couldn't handle and the
device in front of it (a Linux box with always defragment enabled) was
defragmenting the huge IPSec datagrams and then refragmenting them into
hunks that the ISDN PPP thought it could handle but couldn't. Problem was
solved by manually capping the MTU on the ISDN link to a smaller value.
I gave the FreeSwan guys a hard time until tracking it down since
FreeSwan was the only thing that appeared to be able to tickle the bug.
Nothing else seemed to be broken. What it really was that MTU discovery
was avoiding the problem on normal links and it was only the IPSEC tunnels
that were creating huge datagrams that went through the defragment/refragment
process.
Point here is that it "appeared" as though the ISDN link was
failing to handle fragments when it was really a configuration error and
a software bug resulting in a bad MTU that was really the culprit. So
it may not be that the router is not handling fragments. It may be that
it's missconfigured or has some other bug that only FreeSwan is tripping
over.
Subnet-to-subnet works, but tests from the gateways don't
This is described under I cannot ping... above.
Here is a message from FreeS/WAN "listress" (mailing list tech support person) Claudia Schmeing suggesting ways to diagnose and fix such problems:
You write, > I have correctly installed freeswan-1.8 on RH7.0 kernel 2.2.17, but when > I setup a VPN connection with the other machine(RH5.2 Kernel 2.0.36 > freeswan-1.0, it works well.) it told me that > "SIOCADDRT:Network is unreachable"! But the network connection is no > problem. Often this error is the result of a misconfiguration. Be sure that you can route successfully in the absence of Linux FreeS/WAN. (You say this is no problem, so proceed to the next step.) Use a custom copy of the default updownscript. Do not change the route commands, but add a diagnostic message revealing the exact text of the route command. Is there a problem with the sense of the route command that you can see? If so, then re-examine those ipsec.conf settings that are being sent to the route command. You may wish to use the ipsec auto --route and --unroute commands to troubleshoot the problem. See man ipsec_auto for details.Since the above message was written, we have modified the updown script to provide a better diagnostic for this problem. Check /var/log/messages.
From Pluto programmer Hugh Redelmeier:
| Jan 17 16:21:10 remus Pluto[13631]: "jumble" #1: responding to Main Mode from Road Warrior 130.205.82.46 | Jan 17 16:21:11 remus Pluto[13631]: "jumble" #1: no suitable connection for peer @banshee.wittsend.com | | The connection "jumble" has nothing to do with the incoming | connection requests, which were meant for the connection "banshee". You are right. The message tells you which Connection Pluto is currently using, which need not be the right one. It need not be the right one now for the negotiation to eventually succeed! This is described in ipsec_pluto(8) in the section "Road Warrior Support". There are two times when Pluto will consider switching Connections for a state object. Both are in response to receiving ID payloads (one in Phase 1 / Main Mode and one in Phase 2 / Quick Mode). The second is not unique to Road Warriors. In fact, neither is the first any more (two connections for the same pair of hosts could differ in Phase 1 ID payload; probably nobody else has tried this).
Normally a match is found. Then Pluto knows where it is and can set up other things (for example, if it is left) using parameters such as leftsubnet and leftnexthop, and sending its outgoing packets to right.
If no match is found, it emits the above error message.
The match involves the left, right, leftsubnet and rightsubnet parameters and must be exact. For example, if your left subnet is a.b.c.0/24 then neither a single machine in that net nor a smaller subnet such as a.b.c.64/26 will be considered a match.
The message can also occur when an appropriate description exists but Pluto has not loaded it. Use an auto=add statement in the connection description, or an ipsec auto --add <conn_name> command, to correct this.
An explanation from the Pluto developer:
| Jul 12 15:00:22 sohar58 Pluto[574]: "corp_road" #2: cannot respond to IPsec | SA request because no connection is known for | 216.112.83.112/32===216.112.83.112...216.67.25.118 This is the first message from the Pluto log showing a problem. It means that PGPnet is trying to negotiate a set of SAs with this topology: 216.112.83.112/32===216.112.83.112...216.67.25.118 ^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^ client on our side our host PGPnet host, no client None of the conns you showed look like this. Use ipsec auto --status to see a snapshot of what connections are in pluto, what negotiations are going on, and what SAs are established. The leftsubnet= (client) in your conn is 216.112.83.64/26. It must exactly match what pluto is looking for, and it does not.
Another FAQ section describes how to deal with systems that attempt to use single DES.
Background: When one IKE system (for example, Pluto) is negotiating with another to create an SA, the Initiator proposes a bunch of choices and the Responder replies with one that it has selected. The structure of the choices is fairly complicated. An SA payload contains a list of lists of "Proposals". The outer list is a set of choices: the selection must be from one element of this list. Each of these elements is a list of Proposals. A selection must be made from each of the elements of the inner list. In other words, *all* of them apply (that is how, for example, both AH and ESP can apply at once). Within each of these Proposals is a list of Transforms. For each Proposal selected, one Transform must be selected (in other words, each Proposal provides a choice of Transforms). Each Transform is made up of a list of Attributes describing, well, attributes. Such as lifetime of the SA. Such as algorithm to be used. All the Attributes apply to a Transform. You will have noticed a pattern here: layers alternate between being disjunctions ("or") and conjunctions ("and"). For Phase 1 / Main Mode (negotiating an ISAKMP SA), this structure is cut back. There must be exactly one Proposal. So this degenerates to a list of Transforms, one of which must be chosen. In your case, no proposal was considered acceptable to Pluto (the Responder). So negotiation ceased. Pluto logs the reason it rejects each Transform. So look back in the log to see what is going wrong.
From John Denker, on the mailing list:
1) The log message some IKE message we sent has been rejected with ECONNREFUSED (kernel supplied no details) is much more suitable than the previous version. Thanks. 2) Minor suggestion for further improvement: it might be worth mentioning that the command tcpdump -i eth1 icmp[0] != 8 and icmp[0] != 0 is useful for tracking down the details in question. We shouldn't expect all IPsec users to figure that out on their own. The log message might even provide a hint as to where to look in the docs.
Reply From Pluto developer Hugh Redelmeier
Good idea. I've added a bit pluto(8)'s BUGS section along these lines. I didn't have the heart to lengthen this message.
Here is a more detailed duscussion from the team's tech support person Claudia Schmeing, responding to a query on the mailing list:
> Why ipsec reports no eroute! ???? IP Masq... is disabled. In general, more information is required so that people on the list may give you informed input. See doc/prob.report. However, I can make some general comments on this type of error. This error usually looks something like this (clipped from an archived message): > ttl:64 proto:1 chk:45459 saddr:192.168.1.2 daddr:192.168.100.1 > ... klips_debug:ipsec_findroute: 192.168.1.2->192.168.100.1 > ... klips_debug:rj_match: * See if we match exactly as a host destination > ... klips_debug:rj_match: ** try to match a leaf, t=0xc1a260b0 > ... klips_debug:rj_match: *** start searching up the tree, t=0xc1a260b0 > ... klips_debug:rj_match: **** t=0xc1a260c8 > ... klips_debug:rj_match: **** t=0xc1fe5960 > ... klips_debug:rj_match: ***** not found. > ... klips_debug:ipsec_tunnel_start_xmit: Original head/tailroom: 2, 28 > ... klips_debug:ipsec_tunnel_start_xmit: no eroute!: ts=47.3030, dropping. What does this mean? - -------------------- "eroute" stands for "extended route", and is a special type of route internal to Linux FreeS/WAN. For more information about this type of route, see the section of man ipsec_auto on ipsec auto --route. "no eroute!" here means, roughly, that Linux FreeS/WAN cannot find an appropriate tunnel that should have delivered this packet. Linux FreeS/WAN therefore drops the packet, with the message "no eroute! ... dropping", on the assumption that this packet is not a legitimate transmission through a properly constructed tunnel. How does this situation come about? - ----------------------------------- Linux FreeS/WAN has a number of connection descriptions defined in ipsec.conf. These must be successfully brought "up" to form actual tunnels. (see doc/setup.html's step 15, man ipsec.conf and man ipsec_auto for details). Such connections are often specific to the endpoints' IPs. However, in some cases they may be more general, for example in the case of Road Warriors where left or right is the special value %any. When Linux FreeS/WAN receives a packet, it verifies that the packet has come through a legitimate channel, by checking that there is an appropriate tunnel through which this packet might legitimately have arrived. This is the process we see above. First, it checks for an eroute that exactly matches the packet. In the example above, we see it checking for a route that begins at 192.168.1.2 and ends at 192.168.100.1. This search favours the most specific match that would apply to the route between these IPs. So, if there is a connection description exactly matching these IPs, the search will end there. If not, the code will search for a more general description matching the IPs. If there is no match, either specific or general, the packet will be dropped, as we see, above. Unless you are working with Road Warriors, only the first, specific part of the matching process is likely to be relevant to you. "But I defined the tunnel, and it came up, why do I have this error?" - --------------------------------------------------------------------- One of the most common causes of this error is failure to specify enough connection descriptions to cover all needed tunnels between any two gateways and their respective subnets. As you have noticed, troubleshooting this error may be complicated by the use of IP Masq. However, this error is not limited to cases where IP Masq is used. See doc/configuration.html#multitunnel for a detailed example of the solution to this type of problem.
> When FreeS/WAN IPSEC 1.7 is starting on my 2.0.38 Linux kernel the following > error message is generated: > ipsec_setup: Cannot adjust kernel flags, no /proc/sys/net/ipsec directory! > What is supposed to create this directory and how can I fix this problem? I think that directory is a 2.2ism, although I'm not certain (I don't have a 2.0.xx system handy any more for testing). Without it, some of the ipsec.conf config-setup flags won't work, but otherwise things should function.You also need to enable the /proc filesystem in your kernel configuration for these operations to work.
> When I activate one manual tunnels it works, but when I try to activate > another tunnel, it gives an error message... > tunnel_2: Had trouble writing to /dev/ipsec SA:tun0x200@202.103.5.63 -- > SA already in use. Delete old one first. Please read the Using manual keying in production discussion in config.html, specifically the part about needing a different spi (or spibase) setting for each connection.This problem is also discussed in this FAQ under the heading One manual connection works, but second one fails.
| How can I reload config's without restarting all of pluto and klips? I am using | FreeSWAN -> PGPNet in a medium sized production environment, and would like to be | able to add new connections ( i am using include config/* ) without dropping current | SA's. | | Can this be done? | | If not, are there plans to add this kind of feature? ipsec auto --add whatever This will look in the usual place (/etc/ipsec.conf) for a conn named whatever and add it. If you added new secrets, you need to do ipsec auto --rereadsecrets before Pluto needs to know those secrets. | I have looked (perhaps not thoroughly enough tho) to see how to do this: There may be more bits to look for, depending on what you are trying to do.
Here is a mailing list message on the topic. The user incorrectly thinks you need a 2.4 kernel for this -- actually various people have been doing on 2.0 and 2.2 for quite some time -- but he has it right for 2.4.
Subject: Double NAT and freeswan working :) Date: Sun, 11 Mar 2001 From: Paul Wouters <paul@xtdnet.nl> Just to share my pleasure, and make an entry for people who are searching the net on how to do this. Here's the very simple solution to have a double NAT'ed network working with freeswan. (Not sure if this is old news, but I'm not on the list (too much spam) and I didn't read this in any HOWTO/FAQ/doc on the freeswan site yet (Sandy, put it in! :) 10.0.0.0/24 --- 10.0.0.1 a.b.c.d ---- a.b.c.e {internet} ----+ | 10.0.1.0/24 --- 10.0.1.1 f.g.h.i ---- f.g.h.j {internet} ----+ the goal is to have the first network do a VPN to the second one, yet also have NAT in place for connections not destinated for the other side of the NAT. Here the two Linux security gateways have one real IP number (cable modem, dialup, whatever. The problem with NAT is you don't want packets from 10.*.*.* to 10.*.*.* to be NAT'ed. While with Linux 2.2, you can't, with Linux 2.4 you can. (This has been tested and works for 2.4.2 with Freeswan snapshot2001mar8b) relevant parts of /etc/ipsec.conf: left=f.g.h.i leftsubnet=10.0.1.0/24 leftnexthop=f.g.h.j leftfirewall=yes leftid=@firewall.netone.nl leftrsasigkey=0x0........ right=a.b.c.d rightsubnet=10.0.0.0/24 rightnexthop=a.b.c.e rightfirewall=yes rightid=@firewall.nettwo.nl rightrsasigkey=0x0...... # To authorize this connection, but not actually start it, at startup, # uncomment this. auto=add and now the real trick. Setup the NAT correctly on both sites: iptables -t nat -F iptables -t nat -A POSTROUTING -o eth0 -d \! 10.0.0.0/8 -j MASQUERADE This tells the NAT code to only do NAT for packets with destination other then 10.* networks. note the backslash to mask the exclamation mark to protect it against the shell. Happy painting :) Paul
Fairly often a situation comes up where a company has several branches, all using the same non-routable addresses, perhaps 192.168.0.0/24. This works fine as long as those nets are kept distinct. The IP masquerading on their firewalls ensures that packets reaching the Internet carry the firewall address, not the private address.
This can break down when IPSEC enters the picture. FreeS/WAN builds a tunnel that pokes through both masquerades and delivers packets from leftsubnet to rightsubnet and vice versa. For this to work, the two subnets must be distinct.
There are only two solutions to this problem.
For example, you might have:
> Do QoS add to FreeS/WAN? > For example integrating DiffServ and FreeS/WAN? With a current version of FreeS/WAN, you will have to add hidetos=no to the config-setup section of your configuration file. By default, the TOS field of tunnel packets is zeroed; with hidetos=no, it is copied from the packet inside. (This is a modest security hole, which is why it is no longer the default.) DiffServ does not interact well with tunneling in general. Ways of improving this are being studied.See ipsec.conf(5) for more on the hidetos= parameter.
On the other hand, it is a priority for some users and user-contributed
patches are available to add X.509 certificate support to FreeS/WAN now.
See the patches section of our web references
document for details.
Does FreeS/WAN support Radius or other user authentication?
Not yet. So far, there is no standard way to authenticate users for IPSEC,
though there is a very active IETF
working group
looking at the problem, and several vendors have implemented various things
already.
In the absence of a standard, user authentication has not been a priority for the FreeS/WAN team, and is unlikely to become one. This would be a good project for a volunteer, perhaps a staff member or contractor at some company that needs the feature. Certainly our team would co-operate with such an effort; we just don't have time to do it.
Of course, there are various ways to avoid any requirement for user authentication in IPSEC. Consider the situation where road warriors build IPSEC tunnels to your office net and you are considering requiring user authentication during tunnel negotiation. Alternatives include:
Single DES is insecure.
But isn't DES support part of the IPSEC standard?
Yes, but DES is insecure. As we see it, it is more
important to deliver real security than to comply with a standard which
has been subverted into allowing use of inadequate methods. See this
discussion.
I have to talk to .... which offers only DES. How do I do this?
Ask the device vendor for the triple DES upgrade.
These exist for many IPSEC devices. If no cipher stronger than DES is available,
we recommend you not use that IPSEC implementation.
If a 3DES implementation exists but your vendor cannot sell it to you because of export laws, consider complaining to one or more of:
Consider using FreeS/WAN instead. PCs are cheap and we deliver 3DES now.
As a matter of project policy, we will not help anyone subvert FreeS/WAN to provide insecure DES encryption.
As a matter of policy, the list needs to be open to non-subscribers. Project management feel strongly that maintaining this openness is more important than blocking spam.
This has been discussed several times at some length on the list. See the list archives. Bringing the topic up again is unlikely to be useful. Please don't. Or at the very least, please don't without reading the archives and being certain that whatever you are about to suggest has not yet been discussed.
Project technical lead Henry Spencer summarised one discussion:
For the third and last time: this list *will* *not* do address-based filtering. This is a policy decision, not an implementation problem. The decision is final, and is not open to discussion. This needs to be communicated better to people, and steps are being taken to do that.Adding this FAQ section is one of the steps he refers to.
You have various options other than just putting up with the spam or unsubscribing:
A number of tools are available to filter mail.
If you use your ISP's mail server rather than running your own, consider suggesting to the ISP that they tag suspected spam as this ISP does. They could just refuse mail from dubious sources, but that is tricky and runs some risk of losing valuable mail or senselessly annoying senders and their admins. However, they can safely tag and deliver dubious mail. The tags can greatly assist your filtering.
For information on tracking down spammers, see these HowTos, or the Sputum site.
Here is a more detailed message from Henry:
On Mon, 15 Jan 2001, Jay Vaughan wrote: > I know I'm flogging a dead horse here, but I'm curious as to the reasons for > an aversion for a subscriber-only mailing list? Once again: for legal reasons, it is important that discussions of these things be held in a public place -- the list -- and we do not want to force people to subscribe to the list just to ask one question, because that may be more than merely inconvenient for them. There are also real difficulties with people who are temporarily forced to use alternate addresses; that is precisely the time when they may be most in need of help, yet a subscribers-only policy shuts them out. These issues do not apply to most mailing lists, but for a list that is (necessarily) the primary user support route for a crypto package, they are very important. This is *not* an ordinary mailing list; it has to function under awkward constraints that make various simplistic solutions inapplicable or undesirable. > We're *ALL* sick of hearing about list management problems, not just you > old-timers, so why don't you DO SOMETHING EFFECTIVE ABOUT IT... Because it's a lot harder than it looks, and many existing "solutions" have problems when examined closely. > A suggestion for you, based on 10 years of experience with management of my > own mailing lists would be to use mailman, which includes pretty much every > feature under the sun that you guys need and want, plus some. The URL for > mailman... I assure you, we're aware of mailman. Along with a whole bunch of others, including some you almost certainly have never heard of (I hadn't!). > As for the argument that the list shouldn't be configured to enforce > subscription - I contend that it *SHOULD* AT LEAST require manual address > verification in order for posts to be redirected. You do realize, I hope, that interposing such a manual step might cause your government to decide that this is not truly a public forum, and thus you could go to jail if you don't get approval from them before mailing to it? If you think this sounds irrational, your government is noted for making irrational decisions in this area; we can't assume that they will suddenly start being sensible. See above about awkward constraints. You may be willing to take the risk, but we can't, in good conscience, insist that all users with problems do so. Henry Spencer henry@spsystems.netand a message on the topic from project leader John Gilmore:
Subject: Re: The linux-ipsec list's topic Date: Sat, 30 Dec 2000 From: John Gilmore <gnu@toad.com> I'll post this single message, once only, in this discussion, and then not burden the list with any further off-topic messages. I encourage everyone on the list to restrain themself from posting ANY off-topic messages to the linux-ipsec list. The topic of the linux-ipsec mailing list is the FreeS/WAN software. I frequently see "discussions about spam on a list" overwhelm the volume of "actual spam" on a list. BOTH kinds of messages are off-topic messages. Twenty anti-spam messages take just as long to detect and discard as twenty spam messages. The Linux-ipsec list encourages on-topic messages from people who have not joined the list itself. We will not censor messages to the list based on where they originate, or what return address they contain. In other words, non-subscribers ARE allowed to post, and this will not change. My own valid contributions have been rejected out-of-hand by too many other mailing lists for me to want to impose that censorship on anybody else's contributions. And every day I see the damage that anti-spam zeal is causing in many other ways; that zeal is far more damaging to the culture of the Internet than the nuisance of spam. In general, it is the responsibility of recipients to filter, prioritize, or otherwise manage the handling of email that comes to them. It is not the responsibility of the rest of the Internet community to refrain from sending messages to recipients that they might not want to see. If your software infrastructure for managing your incoming email is insufficient, then improve it. If you think the signal-to-noise ratio on linux-ipsec is too poor, then please unsubscribe. But don't further increase the noise by posting to the linux-ipsec list about those topics. John Gilmore founder & sponsor, FreeS/WAN project