Date: Fri, 22 Nov 2002 11:49:17 -0500 From: Lars Eggert <larse@ISI.EDU> To: Helge Oldach <freebsd-stable-21nov02@oldach.net> Cc: Cambria Mike <mcambria@avaya.com>, archie@dellroad.org, guido@gvr.org, dkelly@hiwaay.net, hausen@punkt.de, sullrich@CRE8.COM, greg.panula@dolaninformation.com, FreeBSD-stable@FreeBSD.ORG Subject: Re: IPsec/gif VPN tunnel packets on wrong NIC in ipfw? SOLUTION A ND QUESTIONS Message-ID: <3DDE600D.1080509@isi.edu> In-Reply-To: <200211221611.gAMGBO9j093412@sep.oldach.net> References: <200211221611.gAMGBO9j093412@sep.oldach.net>
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This is a cryptographically signed message in MIME format. --------------ms050303050109080107010608 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Helge Oldach wrote: > OK, I should have been more precise in stating the assumption of an IKE > framework (racoon). IKE should be taught that gif+transport == tunnel. :-) > That's where it breaks. It will however work fine with static keys. The KAME implementation notes have some info on draft-touch in section 4.8, specifically IKE: http://orange.kame.net/dev/cvsweb.cgi/kame/IMPLEMENTATION?rev=1.320 Using IKE over the tunnel works fine, if both ends implement draft-touch. If one doesn't, there is an issue though. And actually, IPIP+transport isn't exactly equivalent to tunnel mode in most current implementations. With tunnel mode, your SAs match on the inner header (inner IP plus you have access to the transport header) on both inbound and outbound. With IPIP+transport, your SAs match on the outer IP header, and can't currently match on transport headers. RFC2401 is currently under revision, and the details of this are enthusiastically discussed (strong opinions on both sides.) > Most examples on the net for setting up IPSec using racoon or isakmpd > do it like this, for both tunnel and transport mode. Looking at the > details in the tunnel mode case one can see that the gif holds more like > a "routing placeholder" to get the routing table for the encapsulated > network correct. That's the only purpose I can see. A loopback interface > could do the same (doesn't work on FreeBSD for some reason), as could > static ARP entries using the MAC address of the encapsulating network's > default gateway. Exactly, these tutorials are broken. They create an IPIP virtual topology using IPIP for routing, and a second parallel topology using IPsec tunnel mode for encryption. Things appear to work fine, until the two topologies get out of sync. Then forwarding fails, or your packets go silently unencrypted. > In practice the problem presented in the paper is commonly solved in > a different fashion: By using GRE or IPIP encapsulation *plus* tunnel > mode. Why tunnel mode, specifically? Thanks, Lars -- Lars Eggert <larse@isi.edu> USC Information Sciences Institute --------------ms050303050109080107010608 Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIJtjCC AzgwggKhoAMCAQICEGZFcrfMdPXPY3ZFhNAukQEwDQYJKoZIhvcNAQEEBQAwgdExCzAJBgNV BAYTAlpBMRUwEwYDVQQIEwxXZXN0ZXJuIENhcGUxEjAQBgNVBAcTCUNhcGUgVG93bjEaMBgG A1UEChMRVGhhd3RlIENvbnN1bHRpbmcxKDAmBgNVBAsTH0NlcnRpZmljYXRpb24gU2Vydmlj ZXMgRGl2aXNpb24xJDAiBgNVBAMTG1RoYXd0ZSBQZXJzb25hbCBGcmVlbWFpbCBDQTErMCkG CSqGSIb3DQEJARYccGVyc29uYWwtZnJlZW1haWxAdGhhd3RlLmNvbTAeFw0wMDA4MzAwMDAw MDBaFw0wNDA4MjcyMzU5NTlaMIGSMQswCQYDVQQGEwJaQTEVMBMGA1UECBMMV2VzdGVybiBD YXBlMRIwEAYDVQQHEwlDYXBlIFRvd24xDzANBgNVBAoTBlRoYXd0ZTEdMBsGA1UECxMUQ2Vy dGlmaWNhdGUgU2VydmljZXMxKDAmBgNVBAMTH1BlcnNvbmFsIEZyZWVtYWlsIFJTQSAyMDAw 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