How do i modify HTTP headers for a JAX-WS response

I have been working on developing CXF web services that sit behind a security proxy which asks for HTTP basic authentication prior service invocation. These services communicate between each other and require authentication for both request and response.

So far i have been able to set HTTP basic authentication via the HTTPConduit for the request like so:

    Client client = ClientProxy.getClient(port);
    HTTPConduit conduit = (HTTPConduit) client.getConduit();
    AuthorizationPolicy authorizationPolicy = new AuthorizationPolicy();
    authorizationPolicy.setUserName(username);
    authorizationPolicy.setPassword(password);
    authorizationPolicy.setAuthorizationType("Basic");
    conduit.setAuthorization(authorizationPolicy);

The method above is called on every service method invocation and i'm getting correct inbound messages in the form of

INFO: Inbound Message
----------------------------
ID: 1
Address: http://someURL/someService?wsdl
Encoding: UTF-8
Http-Method: POST
Content-Type: text/xml; charset=UTF-8
Headers: {Accept=[*/*], Authorization=[Basic {TOKEN}], 
                cache-control=[no-cache], connection=[keep-alive], 
                Content-Length=[735], content-type=[text/xml; charset=UTF-8], 
                pragma=[no-cache], ...}
Payload: <soap:Envelope>...</soap:Envelope>
--------------------------------------

The response, however, doesn't contain the required headers

INFO: Outbound Message
---------------------------
ID: 2
Encoding: UTF-8
Content-Type: text/xml
Headers: {}
Payload: <soap:Envelope/">...</soap:Envelope>
--------------------------------------

How can i modify response HTTP headers? I've tried

((BindingProvider)port).getResponseContext().put(
           MessageContext.HTTP_RESPONSE_HEADERS, 
           Collections.singletonMap("Authentication", 
           Collections.singletonList("Basic "+token)));

without getting the desired result.

One approach would be creating a CXF interceptor.

public class BasicAuthOutInterceptor extends AbstractPhaseInterceptor<Message> {

    public BasicAuthOutInterceptor() {
        super(Phase.PRE_STREAM);
    }

    @Override
    public void handleMessage(Message message) throws Fault {
        String token = "basic auth token";

        @SuppressWarnings("unchecked")
        Map<String, List<String>> headers = (Map<String, List<String>>) message
                .get(Message.PROTOCOL_HEADERS);
        if (headers == null) {
            headers = new TreeMap<String, List<String>>(
                    String.CASE_INSENSITIVE_ORDER);
            message.put(Message.PROTOCOL_HEADERS, headers);
        }

        headers.put("Authentication", Arrays.asList("Basic "+ token));
    }

}

and registering it as an out and outFault interceptor.

    <bean id="basicAuthOutInterceptor class="BasicAuthOutInterceptor" />

    <cxf:bus>
        <cxf:outInterceptors>
            <ref bean="basicAuthOutInterceptor"/>
        </cxf:outInterceptors>
        <cxf:outFaultInterceptors>
            <ref bean="basicAuthOutInterceptor"/>
        </cxf:outFaultInterceptors>        
    </cxf:bus>