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.
FreeS/WAN is a Linux implementation of the IPsec protocols, providing security services at the IP (Internet Protocol) level of the network.
For more detail, see our introduction document or the FreeS/WAN project web site.
To start setting it up, go to our quickstart guide.
Our web links document has information on IPsec for other systems.
It may guide you to a solution. If not, see its problem reporting section.
Basically, what it says is give us the output from ipsec barf from both gateways. Without full information, we cannot diagnose a problem. However, ipsec barf produces a lot of output. If at all possible, please make barfs accessible via the web or FTP rather than sending enormous mail messages.
FreeS/WAN developers, volunteers and users can often be found there. Be patient and be prepared to provide lots of information to support your question.
If your question was really interesting, and you found an answer, please share that with the class by posting to the users mailing list. That way others with the same problem can find your answer in the archives.
See the next several questions.
There are a number of Linux distributions or firewall products which include FreeS/WAN. See this list. Using one of these, chosen to match your requirements and budget, may save you considerable time and effort.
If you don't know your requirements, start by reading Schneier's Secrets and Lies. That gives the best overview of security issues I have seen. Then consider hiring a consultant (see next question) to help define your requirements.
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.
Many of the distributions or firewall products which include FreeS/WAN (see this list) come with commercial support or have it available as an option.
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.
The current release is the highest-numbered tarball on our distribution site. Almost always, any of the mirrors will have the same file, though perhaps not for a day or so after a release.
Unfortunately, the web site is not always updated as quickly as it should be.
We try to do a release approximately every six to eight weeks.
If pre-release tests fail and the fix appears complex, or more generally if the code does not appear stable when a release is scheduled, we will just skip that release.
For serious bugs, we may bring out an extra bug-fix release. These get numbers in the normal release series. For example, there was a bug found in FreeS/WAN 1.6, so we did another release less than two weeks later. The bug-fix release was called 1.7.
Any problems we are aware of at the time of a release are documented in the BUGS file for that release. You should also look at the CHANGES file.
Bugs discovered after a release are discussed on the mailing lists. The easiest way to check for any problems in the current code would be to peruse the List In Brief.
You are free to modify FreeS/WAN in any way. See the discussion of licensing in our introduction document.
Before investing much energy in any such project, we suggest that you
This may prevent duplicated effort, or lead to interesting collaborations.
Users have also contributed heavily to documentation, both by creating their own HowTos and by posting things on the mailing lists which I have quoted in these HTML docs.
There are, however, some caveats.
FreeS/WAN is being implemented in Canada, by Canadians, largely to ensure that is it is entirely free of export restrictions. See this discussion. We cannot accept code contributions from US residents or citizens, not even one-line bugs fixes. The reasons for this were recently discussed extensively on the mailing list, in a thread starting here.
Not all contributions are of interest to us. The project has a set of fairly ambitious and quite specific goals, described in our introduction. Contributions that lead toward these goals are likely to be welcomed enthusiastically. Other contributions may be seen as lower priority, or even as a distraction.
Discussion of possible contributions takes place on the design mailing list.
The only formal design documents are a few papers in the last category above. All the other categories, however, have things to say about design as well.
The IPsec protocols are designed to support interoperation. In theory, any two IPsec implementations should be able to talk to each other. In practice, it is considerably more complex. We have a whole interoperation document devoted to this problem.
An important part of that document is links to the many user-written HowTos on interoperation between FreeS/WAN and various other implementations. Often the users know more than the developers about these issues (and almost always more than me :-), so these documents may be your best resource.
Linux FreeS/WAN can interoperate with many IPsec implementations, including earlier versions of Linux FreeS/WAN itself.
In a few cases, there are some complications. See our interoperation document for details.
There is no hard limit, but see below.
There is no hard limit, but see next question.
A quick summary:
Beyond about 50 tunnels it needs careful management.
See our FreeS/WAN performance document for details.
We build and test on Redhat distributions, but FreeS/WAN runs just fine on several other distributions, sometimes with minor fiddles to adapt to the local environment. Details are in our compatibility document. Also, some distributions or products come with FreeS/WAN included.
FreeS/WAN is intended to run on all CPUs Linux supports . 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 is designed to work on any SMP architecture Linux supports, and has been tested successfully on at least dual processor Intel architecture machines. Details are in our compatibility document.
It might, but we strongly recommend using a recent 2.2 or 2.4 series kernel. Sometimes the newer versions include security fixes which can be quite important on a gateway.
Also, we use recent kernels for development and testing, so those are better tested and, if you do encounter a problem, more easily supported. If something breaks applying recent FreeS/WAN patches to an older kernel, then "update your kernel" is almost certain to be the first thing we suggest. It may be the only suggestion we have.
The precise kernel versions supported by a particular FreeS/WAN release are given in the README file of that release.
See the following question for more on kernels.
Sometimes yes, but quite often, no.
Kernel versions supported are given in the README file of each FreeS/WAN release. Typically, they are whatever production kernels were current at the time of our release (or shortly before; we might release for kernel n just as Linus releases n+1 ). Often FreeS/WAN will work on slightly later kernels as well, but of course this cannot be guaranteed.
For example, FreeS/WAN 1.91 was released for kernels 2.2.19 or 2.4.5, the current kernels at the time. It also worked on 2.4.6, 2.4.7 and 2.4.8, but 2.4.9 had changes that caused compilation errors if it was patched with FreeS/WAN 1.91.
When such changes appear, we put a fix in the FreeS/WAN snapshots, and distribute it with our next release. However, this is not a high priority for us, and it may take anything from a few days to several weeks for such a problem to find its way to the top of our kernel programmer's To-Do list. In the meanwhile, you have two choices:
We don't even try to keep up with kernel changes outside the main 2.2 and 2.4 branches, such as the 2.4.x-ac patched versions from Alan Cox or the 2.5 series of development kernels. We'd rather work on developing the FreeS/WAN code than on chasing these moving targets. We are, however, happy to get patches for problems discovered there.
See also the Choosing a kernel section of our installation document.
IPsec is designed to work over any network that IP works over, and FreeS/WAN is intended to work over any network interface hardware that Linux supports.
If you have working IP on some unusual interface -- perhaps Arcnet, Token Ring, ATM or Gigabit Ethernet -- then IPsec should "just work".
That said, practice is sometimes less tractable than theory. Our testing is done almost entirely on:
If you have some other interface, especially an uncommon one, it is entirely possible you will get bitten either by a FreeS/WAN bug which our testing did not turn up, or by a bug in the driver that shows up only with our loads.
If IP works on your interface and FreeS/WAN doesn't, seek help on the mailing lists.
Another FAQ section describes MTU problems . These are a possibility for some interfaces.
Yes, FreeSwan works fine, though some network drivers have problems with jumbo sized ethernet frames. If you used interfaces=%defaultroute you do not need to change anything, but if you specified an interface (eg eth0) then remember you must change that to reflect the VLAN interface (eg eth0.2 for VLAN ID 2).
The "eepro100" module is known to be broken, use the e100 driver for those cards instead (included in 2.4 as 'alternative driver' for the Intel EtherExpressPro/100.
You do not need to change any MTU setting (those are workarounds that are only needed for buggy drivers)
This FAQ contributed by Paul Wouters.
For a discussion of which parts of the IPsec specifications FreeS/WAN does and does not implement, see our compatibility document.
For information on some often-requested features, see below.
Absolutely. See this FreeS/WAN-FreeS/WAN configuration example. If only one site is using FreeS/WAN, there may be a relevant HOWTO on our interop page.
Yes. We call the remote users "Road Warriors". Check out our FreeS/WAN-FreeS/WAN Road Warrior Configuration Example.
If your Road Warrior is a Windows or Mac PC, you may need to install an IPsec implementation on that machine. Our interop page lists many available brands, and features links to several HOWTOs.
Yes, but there are severe restrictions, so we strongly recommend using RSA keys for authentication instead.
See this FAQ question.
Yes, it is a common practice to use IPsec over wireless networks because their built-in encryption, WEP, is insecure.
There is some discussion in our advanced configuration document. See also the WaveSEC site.
Vanilla FreeS/WAN does not support X.509, but Andreas Steffen and others have provided a popular, well-supported X.509 patch.
Linux FreeS/WAN features Opportunistic Encryption, an alternative Public Key Infrastructure based on Secure DNS.
Andreas Steffen's X.509 patch (v. 1.42+) supports Smart Cards. The patch does not ship with vanilla FreeS/WAN, but will be incorporated into Openswan 2.01+. The patch implements the PCKS#15 Cryptographic Token Information Format Standard, using the OpenSC smartcard library functions.
Older news:
A user-supported patch to FreeS/WAN 1.3, for smart card style authentication, is available on Bastiaan's site. It supports skeyid and ibutton. This patch is not part of Openswan.
For a while progress on this front was impeded by a lack of standard. The IETF working group has now nearly completed its recommended solution to the problem; meanwhile several vendors have implemented various things.
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:
If either of those is trustworthy, it is not clear that you need user authentication in IPsec.
Vanilla FreeS/WAN does not, but thanks to Mathieu Lafon and Arkoon Network Security, there's a patch to support this.
The NAT traversal patch has some issues with PSKs, so you may wish to authenticate with RSA keys, or X.509 (requires a patch which is also included in Openswan). Doing the latter also has advantages when dealing with large numbers of clients who may be behind NAT; instead of having to make an individual Roadwarrior connection for each virtual IP, you can use the "rightsubnetwithin" parameter to specify a range. See these rightsubnetwithin instructions.
Some IPsec implementations allow you to make the source address on packets sent by a Road Warrior machine be something other than the address of its interface to the Internet. This is sometimes described as assigning a virtual identity to that machine.
FreeS/WAN does not directly support this, but it can be done. See this FAQ question.
No, single DES is not used either at the IKE level for negotiating connections or at the IPsec level for actually building them.
Single 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 .
If you want to interoperate with an IPsec implementation which offers only DES, see our interoperation document.
AES is a new US government block cipher standard to replace the obsolete DES.
At time of writing (March 2002), the FreeS/WAN distribution does not yet support AES but user-written patches are available to add it. Our kernel programmer is working on integrating those patches into the distribution, and there is active discussion of this on the design mailimg list.
Currently triple DES is the only cipher supported. AES will almost certainly be added (see previous question), and it is likely that in the process we will also add the other two AES finalists with open licensing, Twofish and Serpent.
We are extremely reluctant to add other ciphers. This would make both use and maintenance of FreeS/WAN more complex without providing any clear benefit. Complexity is emphatically not desirable in a security product.
Various users have written patches to add other ciphers. We provide links to these.
Yes, you can, so long as you pay attention to the selection rule, which can be summarized "the most specific connection wins". We describe the rule in our policy groups document, and provide a more technical explanation in man ipsec.conf.
A good guideline: If you have a regular connection defined in ipsec.conf, ensure that a subset of that connection is not listed in a less restrictive policy group. Otherwise, FreeS/WAN will use the subset, with its more specific source/destination pair.
Here's an example. Suppose you are the system administrator at 192.0.2.2. You have this connection in ipsec.conf: ipsec.conf :
conn net-to-net
left=192.0.2.2 # you are here
right=192.0.2.8
rightsubnet=192.0.2.96/27
....
If you then place a host or net within rightsubnet, (let's say 192.0.2.98) in private-or-clear, you may find that 192.0.2.2 at times communicates in the clear with 192.0.2.98. That's consistent with the rule, but may be contrary to your expectations.
On the other hand, it's safe to put a larger subnet in a less restrictive policy group file. If private-or-clear contains 192.0.2.0/24, then the more specific net-to-net connection is used for any communication to 192.0.2.96/27. The more general policy applies only to communication with hosts or subnets in 192.0.2.0/24 without a more specific policy or connection.
Yes. Use these instructions.
Yes, you can do this. Here are the details, in a mailing list message from Pluto programmer Hugh Redelmeier:
| 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.
Another useful command here is ipsec auto --replace <conn_name> which re-reads data for a named connection.
Yes. This is done all the time. See the discussion in our setup document. The only restriction is that the subnets on the two ends must not overlap. See the next question.
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 it 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
No. The notion that IP addresses are unique is one of the fundamental principles of the IP protocol. Messing with it is exceedingly perilous.
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 several solutions to this problem.
Usually, you re-number the subnets. Perhaps the Vancouver office becomes 192.168.101.0/24, Calgary 192.168.102.0/24 and so on. FreeS/WAN can happily handle this. With, for example leftsubnet=192.168.101.0/24 and rightsubnet=192.168.102.0/24 in a connection description, any machine in Calgary can talk to any machine in Vancouver. If you want to be more restrictive and use something like leftsubnet=192.168.101.128/25 and rightsubnet=192.168.102.240/28 so only certain machines on each end have access to the tunnel, that's fine too.
You could also split the subnet into smaller ones, for example using 192.168.1.0/25 in Vancouver and rightsubnet=192.168.0.128/25 in Calgary.
Alternately, you can just give up routing directly to machines on the subnets. Omit the leftsubnet and rightsubnet parameters from your connection descriptions. Your IPsec tunnels will then run between the public interfaces of the two firewalls. Packets will be masqueraded both before they are put into tunnels and after they emerge. Your Vancouver client machines will see only one Calgary machine, the firewall.
Often it would be convenient to be able to give a Road Warrior an IP address which appears to be on the local network. Some IPsec implementations have support for this, sometimes calling the feature "virtual identity".
Currently (Sept 2002) FreeS/WAN does not support this, and we have no definite plans to add it. The difficulty is that is not yet a standard mechanism for it. There is an Internet Draft for a method of doing it using DHCP which looks promising. FreeS/WAN may support that in a future release.
In the meanwhile, you can do it yourself using the Linux iproute2(8) facilities. Details are in this paper.
Another method has also been discussed on the mailing list.:
For example, you might have:
You then set up routing so that the office machines use the IPsec gateway as their route to a.b.c.128/25. The leftsubnet parameter tells the road warriors to use tunnels to reach a.b.c.0/25, so you should have two-way communication. Depending or your network and applications, there may be some additional work to do on DNS or Windows configuration
Yes. This is easily done, using
In either case, each Road Warrior must have a different key or certificate.
It is also possible using pre-shared key authentication, though we don't recommend this; see the next question for details.
If you expect to have more than a few dozen Road Warriors connecting simultaneously, you may need a fairly powerful gateway machine. See our document on FreeS/WAN performance.
Yes, but avoid it if possible.
You can have multiple Road Warriors using shared secret authentication only if they all use the same secret. You must also set:
uniqueids=no
in the connection definition.
Why it's less secure:
This is a designed-in limitation of the IKE key negotiation protocol, not a problem with our implementation.
We very strongly recommend that you avoid using shared secret authentication for multiple Road Warriors. Use RSA authentication instead.
The longer story: When using shared secrets, the protocol requires that the responding gateway be able to determine which secret to use at a time when all it knows about the initiator is an IP address. This works fine if you know the initiator's address in advance and can use it to look up the appropiriate secret. However, it fails for Road Warriors since the gateway cannot know their IP addresses in advance.
With RSA signatures (or certificates) the protocol is slightly different. The initiator provides an identifier early in the exchange and the responder can use that identifier to look up the correct key or certificate. See above.
From project technical lead Henry Spencer:
> 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.
Copying the TOS (type of service) information from the encapsulated packet to the outer header reveals the TOS information to an eavesdropper. This does not tell him much, but it might be of use in traffic analysis. Since we do not have to give it to him, our default is not to.
Even with the TOS hidden, you can still:
See ipsec.conf(5) for more on the hidetos= parameter.
There is no general mechanism to do this is in the IPsec protocols.
From time to time, there is discussion on the IETF Working Group mailing list of adding a "keep-alive" mechanism (which some say should be called "make-dead"), but it is a fairly complex problem and no consensus has been reached on whether or how it should be done.
The protocol does have optional delete-SA messages which one side can send when it closes a connection in hopes this will cause the other side to do the same. FreeS/WAN does not currently support these. In any case, they would not solve the problem since:
However, connections do have limited lifetimes and you can control how many attempts your gateway makes to rekey before giving up. For example, you can set:
conn default
keyingtries=3
keylife=30m
With these settings old connections will be cleaned up. Within 30 minutes of the other end dying, rekeying will be attempted. If it succeeds, the new connection replaces the old one. If it fails, no new connection is created. Either way, the old connection is taken down when its lifetime expires.
Here is a mailing list message on the topic from FreeS/WAN tech support person Claudia Schmeing:
You ask how to determine whether a tunnel is redundant:
> Can anybody explain the best way to determine this. Esp when a RW has
> disconnected? I thought 'ipsec auto --status' might be one way.
If a tunnel goes down from one end, Linux FreeS/WAN on the
other end has no way of knowing this until it attempts to rekey.
Once it tries to rekey and fails, it will 'know' that the tunnel is
down.
Because it doesn't have a way of knowing the state until this point,
it will also not be able to tell you the state via ipsec auto --status.
> However, comparing output from a working tunnel with that of one that
> was closed
> did not show clearly show tunnel status.
If your tunnel is down but not 'unrouted' (see man ipsec_auto), you
should not be able to ping the opposite side of the tunnel. You can
use this as an indicator of tunnel status.
On a related note, you may be interested to know that as of 1.7,
redundant tunnels caused by RW disconnections are likely to be
less of a pain. From doc/CHANGES:
There is a new configuration parameter, uniqueids, to control a new Pluto
option: when a new connection is negotiated with the same ID as an old
one, the old one is deleted immediately. This should help eliminate
dangling Road Warrior connections when the same Road Warrior reconnects.
It thus requires that IDs not be shared by hosts (a previously legal but
probably useless capability). NOTE WELL: the sample ipsec.conf now has
uniqueids=yes in its config-setup section.
Cheers,
Claudia
This is possible, but not easy. FreeS/WAN technical lead Henry Spencer wrote:
> 5. If the ISDN link goes down in between and is reestablished, the SAs > are still up but the eroute are deleted and the IPsec interface shows > garbage (with ifconfig) > 6. Only restarting IPsec will bring the VPN back online. This one is awkward to solve. If the real interface that the IPsec interface is mounted on goes down, it takes most of the IPsec machinery down with it, and a restart is the only good way to recover. The only really clean fix, right now, is to split the machines in two: 1. A minimal machine serves as the network router, and only it is aware that the link goes up and down. 2. The IPsec is done on a separate gateway machine, which thinks it has a permanent network connection, via the router. This is clumsy but it does work. Trying to do both functions within a single machine is tricky. There is a software package (diald) which will give the illusion of a permanent connection for demand-dialed modem connections; I don't know whether it's usable for ISDN, or whether it can be made to cooperate properly with FreeS/WAN. Doing a restart each time the interface comes up *does* work, although it is a bit painful. I did that with PPP when I was running on a modem link; it wasn't hard to arrange the PPP scripts to bring IPsec up and down at the right times. (I'd meant to investigate diald but never found time.) In principle you don't need to do a complete restart on reconnect, but you do have to rebuild some things, and we have no nice clean way of doing only the necessary parts.
In the same thread, one user commented:
Subject: Re: linux-ipsec: IPsec and Dial Up Connections Date: Wed, 22 Nov 2000 From: Andy Bradford <andyb@calderasystems.com> On Wed, 22 Nov 2000 19:47:11 +0100, Philip Reetz wrote: > Are there any ideas what might be the cause of the problem and any way > to work around it. > Any help is highly appreciated. On my laptop, when using ppp there is a ip-up script in /etc/ppp that will be executed each time that the ppp interface is brought up. Likewise there is an ip-down script that is called when it is taken down. You might consider custimzing those to stop and start FreeS/WAN with each connection. I believe that ISDN uses the same files, though I could be wrong---there should be something similar though.
Yes. Normally this is not necessary, but it is useful in a few special cases. For example, if you must route non-IP packets such as IPX, you will need to use a tunneling protocol that can route these packets. IPsec can be layered around it for extra security. Another example: you can provide failover protection for high availability (HA) environments by combining IPsec with other tools. Ken Bantoft describes one such setup in Using FreeS/WAN with Linux-HA, GRE, OSPF and BGP for enterprise grade VPN solutions.
GRE over IPsec is covered as part of that document. Here are links to other GRE resources. Jacco de Leuw has created this page on L2TP over IPsec with instructions for FreeS/WAN and several other brands of IPsec software.
Please let us know of other useful links via the mailing lists.
Your local PC needs to know how to translate NetBIOS names to IP addresses. It may do this either via a local LMHOSTS file, or using a local or remote WINS server. The WINS server is preferable since it provides a centralized source of the information to the entire network. To use a WINS server over the VPN (or any IP-based network), you must enable "NetBIOS over TCP".
Samba can emulate a WINS server on Linux.
See also several discussions in our September 2002 Users archives
FreeS/WAN is a fairly complex product. (Neither the networks it runs on nor the protocols it uses are simple, so it could hardly be otherwise.) It therefore sometimes exhibits behaviour which can be somewhat confusing, or has problems which are not easy to diagnose. This section tries to explain those problems.
Setup and configuration of FreeS/WAN are covered in other documentation sections:
However, we also list some of the commonest problems here.
This question is dealt with in the advanced configuration section under the heading multiple tunnels.
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 = 192.0.2.8
|
~ internet ~
|
eth0 = 192.0.2.11
gate2
eth1 = x.y.z.1
|
subnet x.y.z.0/24
and the connection description:
conn abc-xyz
left=192.0.2.8
leftsubnet=a.b.c.0/24
right=192.0.2.11
rightsubnet=x.y.z.0/24
You 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:
In some cases, you may be able to get around this. For the example network above, you could use:
ping -I a.b.c.1 x.y.z.1
Both the adresses given are within protected subnets, so this should go through the tunnel.
If required, you can build additional tunnels so that all the machines involved can talk to all the others. See multiple tunnels in the advanced configuration document for details.
Users fairly often report various problems involving long delays, sometimes on tunnel setup and sometimes on operations done through the tunnel, occasionally on simple things like ping or more often on more complex operations like doing NFS or Samba through the tunnel.
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 connections are designed to carry only packets travelling between pre-defined connection endpoints. As project technical lead Henry Spencer put it:
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 === roadwarrior
If 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 this example.
This is a special case of the vanishing packet problem described in the previous question. Whenever KLIPS sees packets for which it does not have a tunnel, it drops them.
When a tunnel goes away, either because negotiations with the other gateway failed or because you gave an ipsec auto --down command, the route to its other end is left pointing into KLIPS, and KLIPS will drop packets it has no tunnel for.
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 ipsec auto --unroute command for these cases.
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).
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).
See also this mailing list message.
If firewalls filter out:
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 .
Some advice from technical lead Henry Spencer on diagnosing such problems:
> > Packets vanishing between the hardware interface and the ipsecN interface > > is usually the result of firewalls not being configured to let them in... > > Thanks for the suggestion. If only it were that simple! My ipchains startup > script does take care of that, but just in case I manually inserted rules > accepting everything from london on dublin. No difference. The other thing to check is whether the "RX packets dropped" count on the ipsecN interface (run "ifconfig ipsecN", for N=1 or whatever, to see the counts) is rising. If so, then there's some sort of configuration mismatch between the two ends, and IPsec itself is rejecting them. If none of the ipsecN counts is rising, then the packets are never reaching the IPsec machinery, and the problem is almost certainly in firewalls etc.
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 out 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).
When an underlying connection (eg. ppp) goes down, FreeS/WAN will not recover properly without a little help. Here are the symptoms that FreeS/WAN user Michael Carmody noticed:
> After about 24 hours the freeswan connection takes over the default route. > > i.e instead of deafult gateway pointing to the router via eth0, it becomes a > pointer to the router via ipsec0. > All internet access is then lost as all replies (and not just the link I > wanted) are routed out ipsec0 and the router doesn't respond to the ipsec > traffic.
If you're using a FreeS/WAN 2.x/KLIPS system, simply re-attach the IPsec virtual interface with ipsec tnconfig command such as:
ipsec tnconfig --attach --virtual ipsec0 --physical ppp0
In your command, name the physical and virtual interfaces as they appear paired on your system during regular uptime. For a system with several physical/virtual interface pairs on flaky links, you'll need more than one such command. If you're using FreeS/WAN 1.x, you must restart FreeS/WAN, which is more time consuming.
Here is a script which can help to automate the process of FreeS/WAN restart at need. It could easily be adapted to use tnconfig instead.
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.
See our testing document for more detail.
As far as traceroute can see, the two gateways are one hop apart; the data packet goes directly from one to the other through the tunnel. Of course the outer packets that implement the tunnel pass through whatever lies between the gateways, but those packets are built and dismantled by the gateways. Traceroute does not see them and cannot report anything about their path.
Here is a mailing list message with more detail.
Date: Mon, 14 May 2001 To: linux-ipsec@freeswan.org From: "John S. Denker" <jsd@research.att.com< Subject: Re: traceroute: one virtual hop At 02:20 PM 5/14/01 -0400, Claudia Schmeing wrote: > >> > A bonus question: traceroute in subnet to subnet enviroment looks like: >> > >> > traceroute to andris.dmz (172.20.24.10), 30 hops max, 38 byte packets >> > 1 drama (172.20.1.1) 0.716 ms 0.942 ms 0.434 ms >> > 2 * * * >> > 3 andris.dmz (172.20.24.10) 73.576 ms 78.858 ms 79.434 ms >> > >> > Why aren't there the other hosts which take part in the delivery during > * * * ? > >If there is an ipsec tunnel between GateA and Gate B, this tunnel forms a >'virtual wire'. When it is tunneled, the original packet becomes an inner >packet, and new ... headers are added to create an outer packet >around it... > >Think about the packet's path from the inner packet's perspective. >It leaves the subnet, goes into the tunnel, and re-emerges in the second >subnet. This perspective is also the only one available to the >'traceroute' command when the IPSec tunnel is up. Claudia got this exactly right. Let me just expand on a couple of points: *) GateB is exactly one (virtual) hop away from GateA. This is how it would be if there were a physically private wire from A to B. The virtually private connection should work the same, and it does. *) While the information is in transit from GateA to GateB, the hop count of the outer header (the "envelope") is being decremented. The hop count of the inner header (the "contents" of the envelope) is not decremented and should not be decremented. The hop count of the outer header is not derived from and should not be derived from the hop count of the inner header. Indeed, even if the packets did time out in transit along the tunnel, there would be no way for traceroute to find out what happened. Just as information cannot leak _out_ of the tunnel to the outside, information cannot leak _into_ the tunnel from outside, and this includes ICMP messages from routers along the path. There are some cases where one might wish for information about what is happening at the IP layer (below the tunnel layer) -- but the protocol makes no provision for this. This raises all sorts of conceptual issues. AFAIK nobody has ever cared enough to really figure out what _should_ happen, let alone implement it and standardize it. *) I consider the "* * *" to be a slight bug. One might wish for it to be replaced by "GateB GateB GateB". It has to do with treating host-to-subnet traffic different from subnet-to-subnet traffic (and other gory details). I fervently hope KLIPS2 will make this problem go away. *) If you want to ask questions about the link from GateA to GateB at the IP level (below the tunnel level), you have to ssh to GateA and launch a traceroute from there.
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:
This is a fairly common problem when attempting to configure multiple manually keyed connections from a single gateway.
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 doc section Using manual keying in production and the man page ipsec.conf(5).
The most common reason for this behaviour is a firewall dropping the UDP port 500 packets used in key negotiation.
Other possibilities:
One common configuration error is forgetting that you need auto=add to load the connection description on the receiving end so it recognises the connection when the other end asks for it.
Some possibile problems are discussed in out interoperation document.
When we first added compression, we saw some problems:
We have not seen either problem in some time (at least six months as I write in March 2002), but if you have some unusual configuration then you may see them.
If tests with ping(1) and a small packet size succeed, but tests or transfers with larger packet sizes fail, suspect problems with packet fragmentation and perhaps path MTU discovery.
Our troubleshooting document covers these problems. Information on the underlying mechanism is in our background document.
This is described under I cannot ping... above.
Pluto needs the GMP (GNU
Multi-Precision) library for the large integer calculations it uses in public key cryptography. This error message indicates a failure to find the library. You must install it before Pluto will compile.
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 apt-get install gmp2.
For more information and the latest version, see the GMP home page.
We have had several reports of this message appearing, all on SPARC Linux. Here is a mailing message on a solution:
> ipsec_sha1.c: In function `SHA1Transform': > ipsec_sha1.c:95: virtual memory exhausted I'm seeing exactly the same problem on an Ultra with 256MB ram and 500 MB swap. Except I am compiling version 1.5 and its Red Hat 6.2. I can get around this by using -O instead of -O2 for the optimization level. So it is probably a bug in the optimizer on the sparc complier. I'll try and chase this down on the sparc lists.
Here is a discussion of this error from FreeS/WAN "listress" (mailing list tech support person) Claudia Schmeing. The "FAQ on the network unreachable error" which she refers to is the next question below.
> I reached the point where the two boxes (both on dial-up connections, but > treated as static IPs by getting the IP and editing ipsec.conf after the > connection is established) to the point where they exchange some info, but I > get an error like "route-client command exited with status 7 \n internal > error". > Where can I find a description of this error? In general, if the FAQ doesn't cover it, you can search the mailing list archives - I like to use http://www.sandelman.ottawa.on.ca/linux-ipsec/ but you can see doc/mail.html for different archive formats. Your error comes from the _updown script, which performs some routing and firewall functions to help Linux FreeS/WAN. More info is available at doc/firewall.html and man ipsec.conf. Its routing is integral to the health of Linux FreeS/WAN; it also provides facility to insert custom firewall rules to be executed when you create or destroy a connection. Yours is, of course, a routing error. You can be fairly sure the routing machinery is saying "network is unreachable". There's a FAQ on the "network is unreachable" error, but more information is available now; read on. If your _updown script is recent (for example if it shipped with Linux FreeS/WAN 1.91), you will see another debugging line in your logs that looks something like this: > output: /usr/local/lib/ipsec/_updown: `route add -net 128.174.253.83 > netmask 255.255.255.255 dev ipsec0 gw 66.92.93.161' failed This is, of course, the system route command that exited with status 7, (ie. failed). Man route for details. Seeing the command typed out yields more information. If your _updown script is older, you may wish to update it to show the command explicitly. Three parameters fed to the route command: net, netmask and gw [gateway] are derived from things you've put in ipsec.conf. Net and netmask are derived from the peer's IP and mask. In more detail: You may see a routing error when routing to a client (ie. subnet), or to a host (IPSec gateway or freestanding host; a box that does IPSec for itself). In _updown, the "route-client" section is responsible to set up the route for IPSec'd (usually, read 'tunneled') packets headed to a peer subnet. Similarly, route-host routes IPSec'd packets to a peer host or IPSec gateway. When routing to a 'client', net and netmask are ipsec.conf's left- or rightsubnet (whichever is not local). Similarly, when routing to a 'host' the net is left or right. Host netmask is always /32, indicating a single machine. Gw is nexthop's value. Again, the value in question is left- or rightnexthop, whichever is local. Where left/right or left-/rightnexthop has the special value %defaultroute (described in man ipsec.conf), gw will automagically get the value of the next hop on the default route. Q: "What's a nexthop and why do I need one?" A: 'nexthop' is a routing kluge; its value is the next hop away from the machine that's doing IPSec, and toward your IPSec peer. You need it to get the processed packets out of the local system and onto the wire. While we often route other packets through the machine that's now doing IPSec, and are done with it, this does not suffice here. After packets are processed with IPSec, this machine needs to know where they go next. Of course using the 'IPSec gateway' as their routing gateway would cause an infinite loop! [To visualize this, see the packet flow diagram at doc/firewall.html.] To avoid this, we route packets through the next hop down their projected path. Now that you know the background, consider: 1. Did you test routing between the gateways in the absence of Linux FreeS/WAN, as recommended? You need to ensure the two machines that will be running Linux FreeS/WAN can route to one another before trying to make a secure connection. 2. Is there anything obviously wrong with the sense of your route command? Normally, this problem is caused by an incorrect local nexthop parameter. Check out the use of %defaultroute, described in man ipsec.conf. This is a simple way to set nexthop for most people. To figure nexthop out by hand, traceroute in-the-clear to your IPSec peer. Nexthop is the traceroute's first hop after your IPSec gateway.
This message is not from FreeS/WAN, but from the Linux IP stack itself. That stack is seeing packets it has no route for, either because your routing was broken before FreeS/WAN started or because FreeS/WAN's changes broke it.
Here is a message from Claudia 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.
See also the FAQ question route-client (or host) exited with status 7.
These messages indicate an installation failure. The kernel you are running does not contain the KLIPS (kernel IPsec) code.
Note that the "modprobe: Can't locate module ipsec" message appears even if you are not using modules. If there is no KLIPS in your kernel, FreeS/WAN tries to load it as a module. If that fails, you get this message.
Commands you can quickly try are:
If those don't find the problem, you have to go back and check through the install procedure to see what was missed.
Here is one of Claudia's messages on the topic:
> I tried to install freeswan 1.8 on my mandrake 7.2 test box. ... > It does show version and some output for whack. Yes, because the Pluto (daemon) part of ipsec is installed correctly, but as we see below the kernel portion is not. > However, I get the following from /var/log/messages: > > Mar 11 22:11:55 pavillion ipsec_setup: Starting FreeS/WAN IPsec 1.8... > Mar 11 22:12:02 pavillion ipsec_setup: modprobe: Can't locate module ipsec > Mar 11 22:12:02 pavillion ipsec_setup: Fatal error, kernel appears to lack > KLIPS. This is your problem. You have not successfully installed a kernel with IPSec machinery in it. Did you build Linux FreeS/WAN as a module? If so, you need to ensure that your new module has been installed in the directory where your kernel loader normally finds your modules. If not, you need to ensure that the new IPSec-enabled kernel is being loaded correctly. See also doc/install.html, and INSTALL in the distro.
Quoting Henry:
Note that by default, FreeS/WAN is now set up to
(a) authenticate with RSA keys, and
(b) fetch the public key of the far end from DNS.
Explicit attention to ipsec.conf will be needed if you want
to do something different.
and Claudia, responding to the same user:
You write, > My current setup in ipsec.conf is leftrsasigkey=%dns I have > commented this and authby=rsasig out. I am able to get ipsec running, > but what I find is that the documentation only specifies for %dns are > there any other values that can be placed in this variable other than > %dns and the key? I am also assuming that this is where I would place > my public key for the left and right side as well is this correct? Valid values for authby= are rsasig and secret, which entail authentication by RSA signature or by shared secret, respectively. Because you have commented authby=rsasig out, you are using the default value of authby=secret. When using RSA signatures, there are two ways to get the public key for the IPSec peer: either copy it directly into *rsasigkey= in ipsec.conf, or fetch it from dns. The magic value %dns for *rsasigkey parameters says to try to fetch the peer's key from dns. For any parameters, you may find their significance and special values in man ipsec.conf. If you are setting up keys or secrets, be sure also to reference man ipsec.secrets.
This is a fatal error. FreeS/WAN cannot cope with two or more interfaces using the same IP address. You must re-configure to avoid this.
A mailing list message on the topic from Pluto developer Hugh Redelmeier:
| I'm trying to get freeswan working between two machine where one has a ppp | interface. | I've already suceeded with two machines with ethernet ports but the ppp | interface is causing me problems. | basically when I run ipsec start i get | ipsec_setup: Starting FreeS/WAN IPsec 1.7... | ipsec_setup: 003 IP interfaces ppp1 and ppp0 share address 192.168.0.10! | ipsec_setup: 003 IP interfaces ppp1 and ppp2 share address 192.168.0.10! | ipsec_setup: 003 IP interfaces ppp0 and ppp2 share address 192.168.0.10! | ipsec_setup: 003 no public interfaces found | | followed by lots of cannot work out interface for connection messages | | now I can specify the interface in ipsec.conf to be ppp0 , but this does | not affect the above behaviour. A quick look in server.c indicates that the | interfaces value is not used but some sort of raw detect happens. | | I guess I could prevent the formation of the extra ppp interfaces or | allocate them different ip but I'd rather not. if at all possible. Any | suggestions please. Pluto won't touch an interface that shares an IP address with another. This will eventually change, but it probably won't happen soon. For now, you will have to give the ppp1 and ppp2 different addresses.
A mailing list message form technical lead Henry Spencer:
> 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.
Pluto messages often indicate where Pluto is in the IKE protocols. The letters indicate Main mode or Q uick mode and Initiator or Responder. The numerals are message sequence numbers. For more detail, see our IPsec section.
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).
Older versions of FreeS/WAN used this message. The same error now gives the "we have no ipsecN ..." error described just below.
Your tunnel has no IP address which matches the IP address of any of the available IPsec interfaces. Either you've misconfigured the connection, or you need to define an appropriate IPsec interface connection. interfaces=%defaultroute works in many cases.
A longer story: Pluto needs to know whether it is running on the machine which the connection description calls left or on right. It figures that out by:
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.
This error message occurs when a remote system attempts to negotiate a connection and Pluto does not have a connection description that matches what the remote system has requested. The most common cause is a configuration error on one end or the other.
Parameters involved in this match are left, right , leftsubnet and rightsubnet.
The match 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.
This is similar to the no connection known error, but occurs at a different point in Pluto processing.
Here is one of Claudia's messages explaining the problem:
You write, > What could be the reason of the following error? > "no suitable connection for peer '@xforce'" When a connection is initiated by the peer, Pluto must choose which entry in the conf file best matches the incoming connection. A preliminary choice is made on the basis of source and destination IPs, since that information is available at that time. A payload containing an ID arrives later in the negotiation. Based on this id and the *id= parameters, Pluto refines its conn selection. ... The message "no suitable connection" indicates that in this refining step, Pluto does not find a connection that matches that ID. Please see "Selecting a connection when responding" in man ipsec_pluto for more details.
See also Connection names in Pluto error messages.
Here is one of Claudia's messages discussing this problem:
You write,
> May 22 10:46:31 debian Pluto[25834]: packet from x.y.z.p:10014:
> initial Main Mode message from x.y.z.p:10014
but no connection has been authorized
This error occurs early in the connection negotiation process,
at the first step of IKE negotiation (Main Mode), which is itself the
first of two negotiation phases involved in creating an IPSec connection.
Here, Linux FreeS/WAN receives a packet from a potential peer, which
requests that they begin discussing a connection.
The "no connection has been authorized" means that there is no connection
description in Linux FreeS/WAN's internal database that can be used to
link your ipsec interface with that peer.
"But of course I configured that connection!"
It may be that the appropriate connection description exists in ipsec.conf
but has not been added to the database with ipsec auto --add myconn or the
auto=add method. Or, the connection description may be misconfigured.
The only parameters that are relevant in this decision are left= and right= .
Local and remote ports are also taken into account -- we see that the port
is printed in the message above -- but there is no way to control these
in ipsec.conf.
Failure at "no connection has been authorized" is similar to the
"no connection is known for..." error in the FAQ, and the "no suitable
connection" error described in the snapshot's FAQ. In all three cases,
Linux FreeS/WAN is trying to match parameters received in the
negotiation with the connection description in the local config file.
As it receives more information, its matches take more parameters into
account, and become more precise: first the pair of potential peers,
then the peer IDs, then the endpoints (including any subnets).
The "no suitable connection for peer *" occurs toward the end of IKE
(Main Mode) negotiation, when the IDs are matched.
"no connection is known for a/b===c...d" is seen at the beginning of IPSec
(Quick Mode, phase 2) negotiation, when the connections are matched using
left, right, and any information about the subnets.
This message occurs when the other system attempts to negotiate a connection using single DES, which we do not support because it is insecure.
Our interoperation document has suggestions for how to deal with systems that attempt to use single DES.
This message means that the other gateway has made a proposal for connection parameters, but nothing they proposed is acceptable to Pluto. Possible causes include:
A more detailed explanation, from Pluto programmer Hugh Redelmeier:
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.
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.
On Fri, 29 Jun 2001, Rodrigo Gruppelli wrote: > ...Well, it seem that there's > another problem with it. When I try to generate a pair of RSA keys, > rsasigkey cores dump... *That* is a neon sign flashing "GMP LIBRARY IS BROKEN". Rsasigkey calls GMP a lot, and our own library a little bit, and that's very nearly all it does. Barring bugs in its code or our library -- which have happened, but not very often -- a problem in rsasigkey is a problem in GMP.
See the next question for how to deal with GMP errors.
Pluto has died. Signal 4 is SIGILL, illegal instruction.
The most likely cause is that your GMP (GNU multi-precision) library is compiled for a different processor than what you are running on. Pluto uses that library for its public key calculations.
Try getting the GMP sources and recompile for your processor type. Most Linux distributions will include this source, or you can download it from the GMP home page.
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.
This message means KLIPS has received a packet for which no IPsec tunnel has been defined.
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.
The document she refers to has since been replaced by a section of the troubleshooting document.
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.
The documentation section she refers to is now here.
This error message occurs when two manual connections are set up with the same SPI value.
See the FAQ for One manual connection works, but second one fails.
This message is harmless. The IKE protocol provides for a number of optional messages types:
An implementation is never required to send these, but they are allowed to. The receiver is not required to do anything with them. FreeS/WAN ignores them, but notifies you via the logs.
For the "ignoring delete SA Payload" message, see also our discussion of cleaning up dead tunnels.
This message can appear when you've upgraded an X.509-enabled Linux FreeS/WAN with a vanilla Linux FreeS/WAN. To use your X.509 configs you will need to overwrite the new install with Openswan, or add the X.509 patch by hand.
As a matter of policy, some of our mailing lists need 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, filtering it yourself, 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. Sputum have a Linux anti-spam screensaver available for download.
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.net
and 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