package com.atlassian.seraph.filter;
   
   import com.atlassian.seraph.RequestParameterConstants;
   import com.atlassian.seraph.auth.Authenticator;
   import com.atlassian.seraph.config.SecurityConfig;
   import com.atlassian.seraph.config.SecurityConfigFactory;
   import com.atlassian.seraph.elevatedsecurity.ElevatedSecurityGuard;
   import com.atlassian.seraph.util.RedirectUtils;
   import org.apache.log4j.Logger;
  
  import java.io.IOException;
  import java.net.URI;
  import java.net.URISyntaxException;
  import java.security.Principal;
  import javax.servlet.Filter;
  import javax.servlet.FilterChain;
  import javax.servlet.FilterConfig;
  import javax.servlet.ServletException;
  import javax.servlet.ServletRequest;
  import javax.servlet.ServletResponse;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletRequestWrapper;
  import javax.servlet.http.HttpServletResponse;
  import javax.servlet.http.HttpSession;
  
  /**
   * This is a base authentication filter. It delegates the actual login process to a child class but takes care of the
   * redirection process.
   * <p/>
   * If the authentication is successful, the user will be redirected by the filter to the URL given by the session
   * attribute at SecurityFilter.ORIGINAL_URL_KEY.
   * <p/>
   * If this URL doesn't exist, it will look for a parameter 'os_destination' to use as the redirected URL instead.
   * <p/>
   * If neither is found, it is assumed that the page will check the authorisation status and handle redirection itself.
   * <p/>
   * From the any other filter in the request, or the servlet/JSP/action which processes the request, you can look up the
   * status of the authorisation attempt. The status is a String request attribute, with the key 'os_authstatus'.
   * <p/>
   * The possible statuses are:
   * <ul>
   * <li> LoginFilter.LOGIN_SUCCESS - the login was processed, and user was logged in </li>
   * <li>LoginFilter.LOGIN_FAILURE - the login was processed, the user gave a bad username or password </li>
   * <li>LoginFilter.LOGIN_ERROR - the login was processed, an exception occurred trying to log the user in </li>
   * <li>LoginFilter.LOGIN_NOATTEMPT - the login was no processed, no form parameters existed </li>
   * </ul>
   */
  public abstract class BaseLoginFilter implements Filter
  {
      private static final Logger log = Logger.getLogger(BaseLoginFilter.class);
  
      private FilterConfig filterConfig = null;
      protected static final String ALREADY_FILTERED = "loginfilter.already.filtered";
      public static final String LOGIN_SUCCESS = "success";
      public static final String LOGIN_FAILED = "failed";
      public static final String LOGIN_ERROR = "error";
      public static final String LOGIN_NOATTEMPT = null;
      public static final String OS_AUTHSTATUS_KEY = "os_authstatus";
      private SecurityConfig securityConfig = null;
  
      public BaseLoginFilter()
      {
          super();
      }
  
      public void init(final FilterConfig config)
      {
          this.filterConfig = config;
      }
  
      public void destroy()
      {
          filterConfig = null;
      }
  
      /**
       * @return a FilterConfig
       *
       * @deprecated Not needed in latest version of Servlet 2.3 API
       */
      public FilterConfig getFilterConfig()
      {
          return filterConfig;
      }
  
      /**
       * @param filterConfig a FilterConfig
       *
       * @deprecated Not needed in latest version of Servlet 2.3 API - replaced by init().
       */
      public void setFilterConfig(final FilterConfig filterConfig)
      {
          if (filterConfig != null) //it seems that Orion 1.5.2 calls this with a null config.
          {
              init(filterConfig);
          }
      }
  
      public void doFilter(final ServletRequest servletRequest, final ServletResponse servletResponse, final FilterChain filterChain)
             throws IOException, ServletException
     {
         final String METHOD = "doFilter : ";
         final boolean dbg = log.isDebugEnabled();
         
         // wrap the request with one that returns the User as the Principal
         HttpServletRequest httpServletRequest = new SecurityHttpRequestWrapper((HttpServletRequest) servletRequest);
         HttpServletResponse httpServletResponse = (HttpServletResponse) servletResponse;
 
         if (servletRequest.getAttribute(ALREADY_FILTERED) == null && getSecurityConfig().getController().isSecurityEnabled())
         {
             httpServletRequest.setAttribute(ALREADY_FILTERED, Boolean.TRUE);
             httpServletRequest.setAttribute(OS_AUTHSTATUS_KEY, LOGIN_NOATTEMPT);
 
             if (dbg)
             {
                 log.debug(METHOD + "____ Attempting login for : '" + getRequestUrl(httpServletRequest) + "'");
             }
             //
             // this will call the derived classes to perform the actual login process
             //
             String status = login(httpServletRequest, httpServletResponse);
             httpServletRequest.setAttribute(OS_AUTHSTATUS_KEY, status);
             if (dbg)
             {
                 final String userName = httpServletRequest.getRemoteUser();
                 log.debug(METHOD + "Login completed for '" + userName + "' - " + OS_AUTHSTATUS_KEY + " = '" + status + "'");
             }
 
             // if we successfully logged in - look for an original URL to forward to
             if (LOGIN_SUCCESS.equals(status) && redirectToOriginalDestination(httpServletRequest, httpServletResponse))
             {
                 return;
             }
             // NOTE : LOGIN_NOATTEMPT is a symbolic constant for null which is a language level symbolic constant for...well...null
             if (status == LOGIN_NOATTEMPT)
             {
                 issuePossibleRedirectIfUserIsAlreadyLoggedIn(httpServletRequest, httpServletResponse);
             }
         }
         filterChain.doFilter(httpServletRequest, httpServletResponse);
     }
 
     private String getRequestUrl(final HttpServletRequest httpServletRequest)
     {
         return httpServletRequest.getServletPath() +
                 (httpServletRequest.getPathInfo() == null ? "" : httpServletRequest.getPathInfo()) +
                 (httpServletRequest.getQueryString() == null ? "" : "?" + httpServletRequest.getQueryString());
     }
 
     private void issuePossibleRedirectIfUserIsAlreadyLoggedIn(final HttpServletRequest httpServletRequest, final HttpServletResponse httpServletResponse)
             throws IOException
     {
         /*
           Allow a redirect for an already logged in user under the following conditions
             1: They are already logged in
             2: They have os_destination in their request parameters
             3: They do NOT have seraph_originalurl in their session. This avoids circular redirects when a User
             tries to access a URL they do not have (role-based) privileges to view.
         */
         if (httpServletRequest.getParameterMap().get(RequestParameterConstants.OS_DESTINATION) != null)
         {
             Principal principal = getAuthenticator().getUser(httpServletRequest, httpServletResponse);
             if (principal != null)
             {
                 HttpSession session = httpServletRequest.getSession();
                 if (session != null && session.getAttribute(SecurityConfigFactory.getInstance().getOriginalURLKey()) == null)
                 {
                     redirectToOriginalDestination(httpServletRequest, httpServletResponse);
                 }
             }
         }
     }
 
     /**
      * Performs the actual authentication (if required) and returns the status code. Status code is chosen to be one of
      * these:
      * <p/>
      * The possible statuses are:
      * <ul>
      * <li> BaseLoginFilter.LOGIN_SUCCESS - the login was processed, and user was logged in
      * <li> BaseLoginFilter.LOGIN_FAILURE - the login was processed, the user gave a bad username or password
      * <li> BaseLoginFilter.LOGIN_ERROR - the login was processed, an exception occurred trying to log the user in
      * <li> BaseLoginFilter.LOGIN_NOATTEMPT - the login was no processed, no form parameters existed
      * </ul>
      *
      * @param httpServletRequest  the HTTP request in play
      * @param httpServletResponse the HTTP response in play
      *
      * @return authentication status
      */
     public abstract String login(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse);
 
     /**
      * This request wrapper class overrrides the {@link javax.servlet.http.HttpServletRequest#getRemoteUser()} and
      * {@link javax.servlet.http.HttpServletRequest#getUserPrincipal()} methods and calls the current {@link
      * com.atlassian.seraph.auth.Authenticator} to provide these values.
      */
     class SecurityHttpRequestWrapper extends HttpServletRequestWrapper
     {
         private HttpServletRequest delegateHttpServletRequest;
 
         public SecurityHttpRequestWrapper(final HttpServletRequest delegateHttpServletRequest)
         {
             super(delegateHttpServletRequest);
             this.delegateHttpServletRequest = delegateHttpServletRequest;
         }
 
         public String getRemoteUser()
         {
             Principal user = getUserPrincipal();
             return (user == null) ? null : user.getName();
         }
 
         public Principal getUserPrincipal()
         {
             return getSecurityConfig().getAuthenticator().getUser(delegateHttpServletRequest);
         }
     }
 
     /**
      * Redirect the response to the original destination if present
      *
      * @param httpServletRequest  the HTTP request in play
      * @param httpServletResponse the HTTP response in play
      *
      * @return true if a redirect was needed and issued
      *
      * @throws IOException If the redirect thorws IOException. See {@link HttpServletResponse#sendRedirect}
      */
     protected boolean redirectToOriginalDestination(final HttpServletRequest httpServletRequest, final HttpServletResponse httpServletResponse)
             throws IOException
     {
         final String METHOD = "redirectToOriginalDestination : ";
         final boolean dbg = log.isDebugEnabled();
 
         // First try to get a redirect URL from the session
         String redirectURL = (String) httpServletRequest.getSession().getAttribute(getSecurityConfig().getOriginalURLKey());
         if (redirectURL != null)
         {
             // remove the session parameter
             httpServletRequest.getSession().setAttribute(getSecurityConfig().getOriginalURLKey(), null);
         }
         else
         {
             // No session attribute - try to get a redirect from the request.
             redirectURL = httpServletRequest.getParameter(RequestParameterConstants.OS_DESTINATION);
         }
 
         if (redirectURL == null)
         {
             return false;
         }
 
         // Check redirect for header injection and potential phishing attack - see SER-127 and SER-128
         if (!getSecurityConfig().getRedirectPolicy().allowedRedirectDestination(redirectURL, httpServletRequest))
         {
             // Redirect Destination is not allowed.
             log.warn(METHOD + "Redirect request to '" + redirectURL + "' is not allowed. Will send user to the context root instead.");
             // note that the context path will get added below.
             redirectURL = "/";
         }
 
         if (!isAbsoluteUrl(redirectURL))
         {
             // Reading the javadoc for HttpServletResponse.sendRedirect() leads me to believe that this is overkill or wrong.
             // We should just leave the leading slash of relative paths, and the Servlet container will interpret the context for us.
             redirectURL = RedirectUtils.appendPathToContext(httpServletRequest.getContextPath(), redirectURL);
         }
 
         if (dbg)
         {
             log.debug(METHOD + "Login redirect to: " + redirectURL);
         }
 
         httpServletResponse.sendRedirect(redirectURL);
         return true;
     }
 
     protected boolean isAbsoluteUrl(final String url)
     {
         try
         {
             URI uri = new URI(url);
             return uri.isAbsolute();
         }
         catch (URISyntaxException e)
         {
             return false;
         }
     }
 
     protected Authenticator getAuthenticator()
     {
         return getSecurityConfig().getAuthenticator();
     }
 
     protected ElevatedSecurityGuard getElevatedSecurityGuard()
     {
         return getSecurityConfig().getElevatedSecurityGuard();
     }
 
     protected SecurityConfig getSecurityConfig()
     {
         if (securityConfig == null)
         {
             securityConfig = (SecurityConfig) filterConfig.getServletContext().getAttribute(SecurityConfig.STORAGE_KEY);
         }
         return securityConfig;
     }
 }