Subject: [tsvwg] RFC 6083: Query regarding NULL AUTH Key in DTLS over SCTP

From: Sidhartha pant <[email-masked]>
Date: Sat, 30 May 2020 09:57:45 +0000

Hi Michael,

I have query regarding RFC 6083 section 4.8, as per this section:-

"The endpoint-pair shared secret for Shared Key Identifier 0 is empty
   and MUST be used when establishing a DTLS connection"

Also according to the RFC 4895 section 9. An endpoint is safe from an attack from the "Man in the Middle" (MTM) if the endpoint pair shared Key is used.

"If an endpoint pair shared key is used, even a true man in the middle

   cannot inject chunks, which are required to be authenticated, even if

   he intercepts the initial message exchange.  The endpoint also knows

   that it is accepting authenticated chunks from a peer who knows the

   endpoint pair shared key."

Now if we assume a Man in the middle exist who can sniff the packets and spoof the Peer IP address.

My question is for the initial SCTP handshake when NULL Key (Shared key id 0) is used how can SCTP protect from an Man In the middle which can inject packets required to be authenticated , for example ABORT. In such case this MTM can Abort the establishment of association even before the Master Secret and an endpoint pair shared key is derived from DTLS handshake.

Is there something I am missing here or SCTP is vulnerable during this initial phase of DTLS over SCTP link setup.

Best Regards,

Sidhartha Pant

Huawei Technologies India Pvt. Ltd.

Survey No. 37, Next to EPIP Area, Kundalahalli, Whitefield

Bengaluru-560066, Karnataka

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