Subject: [tsvwg] RFC6083 and interoperability with OpenSSL on top of LKSCTP

From: "Proshin, Maksim" <[email-masked]>
Date: Mon, 26 Nov 2018 13:30:05 +0000

Hi,

During implementation of DTLS over SCTP specified in RFC6083 and interoperability testing we found a few interoperability issues with the peer where OpenSSL on top of Linux Kernel SCTP is running. We think it might be caused by unclarity in the RFC so we ask the WG to provide some explanations if possible.

One issue is about the exporter label which is defined in Section 5 of RFC6083 as "EXPORTER_DTLS_OVER_SCTP". According to RFC5705 the labels are given with no terminating NULL. Does it mean that the implementation should add or should _not_ add the null-terminating symbol when it calculates an endpoint-pair shared key?

The other issue is about the FORWARD-TSN chunk which must be sent in an authenticated way according to RFC6083 if PR-SCTP mechanism is used. The issue is that regardless of whether the PR-SCTP mechanism is enabled or not, the peer always requires the FORWARD-TSN chunk to be present in the CHUNKS parameter of INIT/INIT ACK. We consider it as an implementation fault but want the WG to confirm it.

BR, Maxim