Subject: [mobile-ip] Unresolved issue #5: Alternate CoA

From: Jari Arkko <[email-masked]>
Date: Tue, 09 Apr 2002 21:14:03 +0300

I think this too has consensus, but here it is just in case:

Background: Bombing vulnerabilities may open if Alternate CoA
parameter can be used with address CoA2 and the RR authorization
was performed on CoA1.

Question: Should this vulnerability be closed? If it is closed
by requiring the RR and Alternative CoA parameter to use the
same CoA, will the remaining Alternative CoA be useful for FMIP,
HMIP, and other MIPv6 extensions that may use it.

Proposal: The vulnerability must be closed. It seems that
the remaining Alternative CoA functionality is still useful.
Further work is of course needed to ensure that MIPv6 extensions
don't open new security vulnerabilities.

Text: State the following under 5.1.7:
The care-of address for the binding given in the Binding Update
message is normally that which was received as the value in the Source
Address field in the IPv6 header of the packet carrying the Binding
Update message. However, a care-of address different from the Source
Address MAY be specified by including an Alternate Care-of Address
option in the Binding Update message. When such message is sent to
the correspondent node, the Care-of Test Init and Care-of Test
messages MUST have been performed for the address in the Alternate
Care-of Address option (not the Source Address). The contents of
the Nonce Indices and the Authenticator options MUST be based on
information gained in this test.

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From: "James Kempf" <[email-masked]>
Date: Tue, 9 Apr 2002 14:33:27 -0700

One minor nit: The current text leaves no space for alternative security
mechanisms. Is this the intent, that is, would CoTI and CoT need to be
done if a CGA-like mechanism was in use?

The reason I'm asking is because the major interest in an alternate
security mechanism is for better performance, since some of the intended
uses are performance sensitive.

            jak

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From: Francis Dupont <[email-masked]>
Date: Wed, 10 Apr 2002 10:11:29 +0200

=> alternative CoA is the common way to repeat the CoA when the BU
is protected by ESP so we really need it.
BTW I don't believe in attacks using a fake CoA because the real Home
Address will be in the RH in all packets/fragments so the only difference
with a direct attack is the fake CoA adds a reflection...

   ...

=> agree

[email-masked]

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From: Jari Arkko <[email-masked]>
Date: Wed, 10 Apr 2002 20:23:54 +0300

> done if a CGA-like mechanism was in use?

Yes, and this would also apply to the "military key management mechanism"
that Charlie brought up. Indeed, the text should be clarified that the
this and possibly some other requirements apply only if the RR scheme is
used.

Jari