Thread Coaps (DTS handshake) fails.

[Fränz Ney]

Hi,

With the NRF Connect SDK version 1.9.1 it is not possible to setup a Thread Coaps connection.

The DTLS handshake fails after Client Hello with an Alert message (Illegal Parameter).

Error is triggered in the mbedTLS library => ssl_srv.c => Line 443 => "mbedtls_ecjpake_read_round_one"

Example: Open Thread CLI example => using 2 nrf52840 USB dongles.

I'm using the following CLI guide to establish the COAPS connection: https://github.com/openthread/openthread/blob/main/src/cli/README_COAPS.md

SDK version 1.7.1 works fine!

Cheers,

Fränz

DTS_ERROR.pdfDTS_ERROR_2.pdf

[Amanda Hsieh]

Hi, 

Bug identified in mbedtls SSL Client: https://github.com/nrfconnect/sdk-mbedtls/blob/development/library/ssl_cli.c#L1248-L1256

ECJPAKE extension is added unconditionally to the Client Hello message.

Bugfix can be fixed by adding the extension only when `uses_ec` is True (https://github.com/nrfconnect/sdk-mbedtls/blob/development/library/ssl_cli.c#L1228).

Regards,
Amanda