Dtls secure renegotiation client error when no extensions are used

[kkonieczny-avs]

I am using californium client and server in version 3.12.1. An error occurs if the client sends no extensions in ClientHello, but requests secure renegotiation by adding TLS_EMPTY_RENEGOTIATION_INFO_SCSV to cipher suites. The server will add secure_renegotiation extension to ServerHello as requested, but the client will throw unsupported extension error and terminate the connection. Both client and server are using DtlsSecureRenegotiation.WANTED. I believe this error is thrown in ClientHandshaker.java in line 497. I have zipped .pcapng file, because github doesn't support this extension. secure_renegotation_bug.pcapng.zip

[boaks]

Yes,

            if (clientExtensions == null || clientExtensions.isEmpty()) {
                throw new HandshakeException("Server wants extensions, but client not!",
                        new AlertMessage(AlertLevel.FATAL, AlertDescription.UNSUPPORTED_EXTENSION));
            } else {
                for (HelloExtension serverExtension : serverExtensions.getExtensions()) {
                    if (clientExtensions.getExtension(serverExtension.getType()) == null) {
                        if (serverExtension.getType() == HelloExtension.ExtensionType.RENEGOTIATION_INFO) {
                            hasRenegotiationInfoExtension = true;
                            if (secureRenegotiation != DtlsSecureRenegotiation.NONE) {
                                continue;
                            }
                        }
                        throw new HandshakeException(
                                "Server wants " + serverExtension.getType() + ", but client didn't propose it!",
                                new AlertMessage(AlertLevel.FATAL, AlertDescription.UNSUPPORTED_EXTENSION));
                    }
                }
            }

In the case of empty client extensions, the special handling of RENEGOTIATION_INFO isn't applied ;-). Requires an fix.

As workaround, please enable the extended master secret extension.

# DTLS extended master secret mode.
# [NONE, OPTIONAL, ENABLED, REQUIRED].
# Default: ENABLED
DTLS.EXTENDED_MASTER_SECRET_MODE=ENABLED

[boaks]

Or enable the DTLS CID extension ;-).-

[boaks]

See PR #2262

If possible, please retest with that PR.

[kkonieczny-avs]

It works for me, thank you.

[boaks]

You're welcome.

[boaks]

Any request, when the fix should be released (Minor or Bugfix)?

[kkonieczny-avs]

I would prefer BUGFIX, but if it's a problem MINOR will be sufficient.

[boaks]

It's more a question about the timeline ...

Anyway, though you found the next ... I consider to postpone it after we have a couple of fixes collected ;-).

[boaks]

The minor release is scheduled, see issue #2285