Invalid SessionRequired messages

[steven-bellock]

The SessionRequired error code was introduced in SPDM 1.2. However libspdm will send this error if the version is 1.1 for the following messages

• END_SESSION
• FINISH
• HEARTBEAT
• KEY_UPDATE
• PSK_FINISH

This error needs to be conditional based on the negotiated version. For 1.1 the error code should probably be Unspecified since none of the other errors fit in this situation. In addition SessionRequired is never exercised in the unit tests, and test cases should be added.

Example

libspdm/library/spdm_responder_lib/libspdm_rsp_end_session.c

Lines 46 to 50 in abbb1a4

	if (!spdm_context->last_spdm_request_session_id_valid) {
	return libspdm_generate_error_response(spdm_context,
	SPDM_ERROR_CODE_SESSION_REQUIRED, 0,
	response_size, response);
	}

[steven-bellock]

This was introduced in #690 when the error code was InvalidRequest.

[jyao1]

Maybe do the check and convert in libspdm_generate_error_response().

[steven-bellock]

Keep the error code the same in libspdm_rsp_end_session.c but "downgrade" the error code in libspdm_generate_error_response()? That might be misleading.