public void doFilter()

in services/idp-core/src/main/java/org/apache/cxf/fediz/service/idp/kerberos/KerberosAuthenticationProcessingFilter.java [70:114]
43 lines of code
11 McCabe index (conditional complexity)

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
        throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        if (skipIfAlreadyAuthenticated) {
            Authentication existingAuth = SecurityContextHolder.getContext().getAuthentication();
            if (existingAuth != null && existingAuth.isAuthenticated()
                && !(existingAuth instanceof AnonymousAuthenticationToken)) {
                chain.doFilter(request, response);
                return;
            }
        }
        String header = request.getHeader("Authorization");
        if (header != null && header.startsWith("Negotiate ")) {
            if (logger.isDebugEnabled()) {
                logger.debug("Received Negotiate Header for request " + request.getRequestURL() + ": " + header);
            }
            byte[] base64Token = header.substring(10).getBytes(StandardCharsets.UTF_8);
            byte[] kerberosTicket = Base64.decode(base64Token);
            KerberosServiceRequestToken authenticationRequest = new KerberosServiceRequestToken(kerberosTicket);
            authenticationRequest.setDetails(authenticationDetailsSource.buildDetails(request));
            Authentication authentication;
            try {
                authentication = authenticationManager.authenticate(authenticationRequest);
            } catch (AuthenticationException e) {
                //That shouldn't happen, as it is most likely a wrong
                //configuration on the server side
                logger.warn("Negotiate Header was invalid: " + header, e);
                SecurityContextHolder.clearContext();
                if (failureHandler != null) {
                    failureHandler.onAuthenticationFailure(request, response, e);
                } else {
                    response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
                    response.flushBuffer();
                }
                return;
            }
            sessionStrategy.onAuthentication(authentication, request, response);
            SecurityContextHolder.getContext().setAuthentication(authentication);
            if (successHandler != null) {
                successHandler.onAuthenticationSuccess(request, response, authentication);
            }
        }
        chain.doFilter(request, response);
    }