Subject: Security & draft-deering-ipv6-encap-addr-deletion-00.txt

From: "Christian Huitema" <[email-masked]>
Date: Tue, 11 Dec 2001 09:44:17 -0800

Steve,

In the WG discussion, we alluded to a security risk related to IPSEC
tunnels. The risk is the following. Compare a typical VPN set-up that
uses ESP:

<-- outer IPv6 header ->            <-- inner IPv6 packet, encrypted -> 
+----+--------+--------+------------+----+--------+--------+
+------------ 
|    |        |        |            |    |        |        | | 
|oNAF|  oSRC  |  oDEST | ESP header |iNAF|  iSRC  |  iDEST | |  iPAYLOAD

|    |        |        |            |    |        |        | | 
+----+--------+--------+------------+----+--------+--------+
+------------

Now, with the compression, we would in many cases be able to "compress"
the source address, resulting in:

<-- outer IPv6 header ->            <-- inner IPv6 packet, encrypted -> 
+----+--------+--------+------------+----+--------+ +------------ 
|    |        |        |            |    |        | | 
|oNAF|  oSRC  |  oDEST | ESP header |iNAF|  iDEST | |  iPAYLOAD 
|    |        |        |            |    |        | | 
+----+--------+--------+------------+----+--------+ +------------

The big difference between the two is the iSRC is not protected by the
encryption, but recomposed after decryption by copying oSRC -- which is
not protected. This would open an attack avenue for a hacker or, heavens
forbids, a NAT...

-- Christian Huitema

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