/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  package org.apache.shiro.web.servlet;
  
  import org.apache.shiro.SecurityUtils;
  import org.apache.shiro.session.Session;
  import org.apache.shiro.subject.ExecutionException;
  import org.apache.shiro.subject.Subject;
  import org.apache.shiro.web.filter.mgt.FilterChainResolver;
  import org.apache.shiro.web.mgt.DefaultWebSecurityManager;
  import org.apache.shiro.web.mgt.WebSecurityManager;
  import org.apache.shiro.web.subject.WebSubject;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import javax.servlet.FilterChain;
  import javax.servlet.ServletException;
  import javax.servlet.ServletRequest;
  import javax.servlet.ServletResponse;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import java.io.IOException;
  import java.util.concurrent.Callable;
  
  /**
   * Abstract base class that provides all standard Shiro request filtering behavior and expects
   * subclasses to implement configuration-specific logic (INI, XML, .properties, etc).
   * <p/>
   * Subclasses should perform configuration and construction logic in an overridden
   * {@link #init()} method implementation.  That implementation should make available any constructed
   * {@code SecurityManager} and {@code FilterChainResolver} by calling
   * {@link #setSecurityManager(org.apache.shiro.web.mgt.WebSecurityManager)} and
   * {@link #setFilterChainResolver(org.apache.shiro.web.filter.mgt.FilterChainResolver)} methods respectively.
   * <h3>Static SecurityManager</h3>
   * By default the {@code SecurityManager} instance enabled by this filter <em>will not</em> be enabled in static
   * memory via the {@code SecurityUtils.}{@link SecurityUtils#setSecurityManager(org.apache.shiro.mgt.SecurityManager) setSecurityManager}
   * method.  Instead, it is expected that Subject instances will always be constructed on a request-processing thread
   * via instances of this Filter class.
   * <p/>
   * However, if you need to construct {@code Subject} instances on separate (non request-processing) threads, it might
   * be easiest to enable the SecurityManager to be available in static memory via the
   * {@link SecurityUtils#getSecurityManager()} method.  You can do this by additionally specifying an {@code init-param}:
   * <pre>
   * &lt;filter&gt;
   *     ... other config here ...
   *     &lt;init-param&gt;
   *         &lt;param-name&gt;staticSecurityManagerEnabled&lt;/param-name&gt;
   *         &lt;param-value&gt;true&lt;/param-value&gt;
   *     &lt;/init-param&gt;
   * &lt;/filter&gt;
   * </pre>
   * See the Shiro <a href="http://shiro.apache.org/subject.html">Subject documentation</a> for more information as to
   * if you would do this, particularly the sections on the {@code Subject.Builder} and Thread Association.
   *
   * @since 1.0
   * @see <a href="http://shiro.apache.org/subject.html">Subject documentation</a>
   */
  public abstract class AbstractShiroFilter extends OncePerRequestFilter {
  
      private static final Logger log = LoggerFactory.getLogger(AbstractShiroFilter.class);
  
      private static final String STATIC_INIT_PARAM_NAME = "staticSecurityManagerEnabled";
  
      // Reference to the security manager used by this filter
      private WebSecurityManager securityManager;
  
      // Used to determine which chain should handle an incoming request/response
      private FilterChainResolver filterChainResolver;
  
      /**
       * Whether or not to bind the constructed SecurityManager instance to static memory (via
       * SecurityUtils.setSecurityManager).  This was added to support https://issues.apache.org/jira/browse/SHIRO-287
       * @since 1.2
       */
      private boolean staticSecurityManagerEnabled;
  
      protected AbstractShiroFilter() {
          this.staticSecurityManagerEnabled = false;
      }
  
      public WebSecurityManager getSecurityManager() {
          return securityManager;
      }
 
     public void setSecurityManager(WebSecurityManager sm) {
         this.securityManager = sm;
     }
 
     public FilterChainResolver getFilterChainResolver() {
         return filterChainResolver;
     }
 
     public void setFilterChainResolver(FilterChainResolver filterChainResolver) {
         this.filterChainResolver = filterChainResolver;
     }
 
     /**
      * Returns {@code true} if the constructed {@link #getSecurityManager() securityManager} reference should be bound
      * to static memory (via
      * {@code SecurityUtils.}{@link SecurityUtils#setSecurityManager(org.apache.shiro.mgt.SecurityManager) setSecurityManager}),
      * {@code false} otherwise.
      * <p/>
      * The default value is {@code false}.
      * <p/>
      *
      *
      * @return {@code true} if the constructed {@link #getSecurityManager() securityManager} reference should be bound
      *         to static memory (via {@code SecurityUtils.}{@link SecurityUtils#setSecurityManager(org.apache.shiro.mgt.SecurityManager) setSecurityManager}),
      *         {@code false} otherwise.
      * @since 1.2
      * @see <a href="https://issues.apache.org/jira/browse/SHIRO-287">SHIRO-287</a>
      */
     public boolean isStaticSecurityManagerEnabled() {
         return staticSecurityManagerEnabled;
     }
 
     /**
      * Sets if the constructed {@link #getSecurityManager() securityManager} reference should be bound
      * to static memory (via {@code SecurityUtils.}{@link SecurityUtils#setSecurityManager(org.apache.shiro.mgt.SecurityManager) setSecurityManager}).
      * <p/>
      * The default value is {@code false}.
      *
      * @param staticSecurityManagerEnabled if the constructed {@link #getSecurityManager() securityManager} reference
      *                                       should be bound to static memory (via
      *                                       {@code SecurityUtils.}{@link SecurityUtils#setSecurityManager(org.apache.shiro.mgt.SecurityManager) setSecurityManager}).
      * @since 1.2
      * @see <a href="https://issues.apache.org/jira/browse/SHIRO-287">SHIRO-287</a>
      */
     public void setStaticSecurityManagerEnabled(boolean staticSecurityManagerEnabled) {
         this.staticSecurityManagerEnabled = staticSecurityManagerEnabled;
     }
 
     protected final void onFilterConfigSet() throws Exception {
         //added in 1.2 for SHIRO-287:
         applyStaticSecurityManagerEnabledConfig();
         init();
         ensureSecurityManager();
         //added in 1.2 for SHIRO-287:
         if (isStaticSecurityManagerEnabled()) {
             SecurityUtils.setSecurityManager(getSecurityManager());
         }
     }
 
     /**
      * Checks if the init-param that configures the filter to use static memory has been configured, and if so,
      * sets the {@link #setStaticSecurityManagerEnabled(boolean)} attribute with the configured value.
      *
      * @since 1.2
      * @see <a href="https://issues.apache.org/jira/browse/SHIRO-287">SHIRO-287</a>
      */
     private void applyStaticSecurityManagerEnabledConfig() {
         String value = getInitParam(STATIC_INIT_PARAM_NAME);
         if (value != null) {
             Boolean b = Boolean.valueOf(value);
             if (b != null) {
                 setStaticSecurityManagerEnabled(b);
             }
         }
     }
 
     public void init() throws Exception {
     }
 
     /**
      * A fallback mechanism called in {@link #onFilterConfigSet()} to ensure that the
      * {@link #getSecurityManager() securityManager} property has been set by configuration, and if not,
      * creates one automatically.
      */
     private void ensureSecurityManager() {
         WebSecurityManager securityManager = getSecurityManager();
         if (securityManager == null) {
             log.info("No SecurityManager configured.  Creating default.");
             securityManager = createDefaultSecurityManager();
             setSecurityManager(securityManager);
         }
     }
 
     protected WebSecurityManager createDefaultSecurityManager() {
         return new DefaultWebSecurityManager();
     }
 
     protected boolean isHttpSessions() {
         return getSecurityManager().isHttpSessionMode();
     }
 
     /**
      * Wraps the original HttpServletRequest in a {@link ShiroHttpServletRequest}, which is required for supporting
      * Servlet Specification behavior backed by a {@link org.apache.shiro.subject.Subject Subject} instance.
      *
      * @param orig the original Servlet Container-provided incoming {@code HttpServletRequest} instance.
      * @return {@link ShiroHttpServletRequest ShiroHttpServletRequest} instance wrapping the original.
      * @since 1.0
      */
     protected ServletRequest wrapServletRequest(HttpServletRequest orig) {
         return new ShiroHttpServletRequest(orig, getServletContext(), isHttpSessions());
     }
 
     /**
      * Prepares the {@code ServletRequest} instance that will be passed to the {@code FilterChain} for request
      * processing.
      * <p/>
      * If the {@code ServletRequest} is an instance of {@link HttpServletRequest}, the value returned from this method
      * is obtained by calling {@link #wrapServletRequest(javax.servlet.http.HttpServletRequest)} to allow Shiro-specific
      * HTTP behavior, otherwise the original {@code ServletRequest} argument is returned.
      *
      * @param request  the incoming ServletRequest
      * @param response the outgoing ServletResponse
      * @param chain    the Servlet Container provided {@code FilterChain} that will receive the returned request.
      * @return the {@code ServletRequest} instance that will be passed to the {@code FilterChain} for request processing.
      * @since 1.0
      */
     @SuppressWarnings({"UnusedDeclaration"})
     protected ServletRequest prepareServletRequest(ServletRequest request, ServletResponse response, FilterChain chain) {
         ServletRequest toUse = request;
         if (request instanceof HttpServletRequest) {
             HttpServletRequest http = (HttpServletRequest) request;
             toUse = wrapServletRequest(http);
         }
         return toUse;
     }
 
     /**
      * Returns a new {@link ShiroHttpServletResponse} instance, wrapping the {@code orig} argument, in order to provide
      * correct URL rewriting behavior required by the Servlet Specification when using Shiro-based sessions (and not
      * Servlet Container HTTP-based sessions).
      *
      * @param orig    the original {@code HttpServletResponse} instance provided by the Servlet Container.
      * @param request the {@code ShiroHttpServletRequest} instance wrapping the original request.
      * @return the wrapped ServletResponse instance to use during {@link FilterChain} execution.
      * @since 1.0
      */
     protected ServletResponse wrapServletResponse(HttpServletResponse orig, ShiroHttpServletRequest request) {
         return new ShiroHttpServletResponse(orig, getServletContext(), request);
     }
 
     /**
      * Prepares the {@code ServletResponse} instance that will be passed to the {@code FilterChain} for request
      * processing.
      * <p/>
      * This implementation delegates to {@link #wrapServletRequest(javax.servlet.http.HttpServletRequest)}
      * only if Shiro-based sessions are enabled (that is, !{@link #isHttpSessions()}) and the request instance is a
      * {@link ShiroHttpServletRequest}.  This ensures that any URL rewriting that occurs is handled correctly using the
      * Shiro-managed Session's sessionId and not a servlet container session ID.
      * <p/>
      * If HTTP-based sessions are enabled (the default), then this method does nothing and just returns the
      * {@code ServletResponse} argument as-is, relying on the default Servlet Container URL rewriting logic.
      *
      * @param request  the incoming ServletRequest
      * @param response the outgoing ServletResponse
      * @param chain    the Servlet Container provided {@code FilterChain} that will receive the returned request.
      * @return the {@code ServletResponse} instance that will be passed to the {@code FilterChain} during request processing.
      * @since 1.0
      */
     @SuppressWarnings({"UnusedDeclaration"})
     protected ServletResponse prepareServletResponse(ServletRequest request, ServletResponse response, FilterChain chain) {
         ServletResponse toUse = response;
         if (!isHttpSessions() && (request instanceof ShiroHttpServletRequest) &&
                 (response instanceof HttpServletResponse)) {
             //the ShiroHttpServletResponse exists to support URL rewriting for session ids.  This is only needed if
             //using Shiro sessions (i.e. not simple HttpSession based sessions):
             toUse = wrapServletResponse((HttpServletResponse) response, (ShiroHttpServletRequest) request);
         }
         return toUse;
     }
 
     /**
      * Creates a {@link WebSubject} instance to associate with the incoming request/response pair which will be used
      * throughout the request/response execution.
      *
      * @param request  the incoming {@code ServletRequest}
      * @param response the outgoing {@code ServletResponse}
      * @return the {@code WebSubject} instance to associate with the request/response execution
      * @since 1.0
      */
     protected WebSubject createSubject(ServletRequest request, ServletResponse response) {
         return new WebSubject.Builder(getSecurityManager(), request, response).buildWebSubject();
     }
 
     /**
      * Updates any 'native'  Session's last access time that might exist to the timestamp when this method is called.
      * If native sessions are not enabled (that is, standard Servlet container sessions are being used) or there is no
      * session ({@code subject.getSession(false) == null}), this method does nothing.
      * <p/>This method implementation merely calls
      * <code>Session.{@link org.apache.shiro.session.Session#touch() touch}()</code> on the session.
      *
      * @param request  incoming request - ignored, but available to subclasses that might wish to override this method
      * @param response outgoing response - ignored, but available to subclasses that might wish to override this method
      * @since 1.0
      */
     @SuppressWarnings({"UnusedDeclaration"})
     protected void updateSessionLastAccessTime(ServletRequest request, ServletResponse response) {
         if (!isHttpSessions()) { //'native' sessions
             Subject subject = SecurityUtils.getSubject();
             //Subject should never _ever_ be null, but just in case:
             if (subject != null) {
                 Session session = subject.getSession(false);
                 if (session != null) {
                     try {
                         session.touch();
                     } catch (Throwable t) {
                         log.error("session.touch() method invocation has failed.  Unable to update " +
                                 "the corresponding session's last access time based on the incoming request.", t);
                     }
                 }
             }
         }
     }
 
     /**
      * {@code doFilterInternal} implementation that sets-up, executes, and cleans-up a Shiro-filtered request.  It
      * performs the following ordered operations:
      * <ol>
      * <li>{@link #prepareServletRequest(ServletRequest, ServletResponse, FilterChain) Prepares}
      * the incoming {@code ServletRequest} for use during Shiro's processing</li>
      * <li>{@link #prepareServletResponse(ServletRequest, ServletResponse, FilterChain) Prepares}
      * the outgoing {@code ServletResponse} for use during Shiro's processing</li>
      * <li> {@link #createSubject(javax.servlet.ServletRequest, javax.servlet.ServletResponse) Creates} a
      * {@link Subject} instance based on the specified request/response pair.</li>
      * <li>Finally {@link Subject#execute(Runnable) executes} the
      * {@link #updateSessionLastAccessTime(javax.servlet.ServletRequest, javax.servlet.ServletResponse)} and
      * {@link #executeChain(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)}
      * methods</li>
      * </ol>
      * <p/>
      * The {@code Subject.}{@link Subject#execute(Runnable) execute(Runnable)} call in step #4 is used as an
      * implementation technique to guarantee proper thread binding and restoration is completed successfully.
      *
      * @param servletRequest  the incoming {@code ServletRequest}
      * @param servletResponse the outgoing {@code ServletResponse}
      * @param chain           the container-provided {@code FilterChain} to execute
      * @throws IOException                    if an IO error occurs
      * @throws javax.servlet.ServletException if an Throwable other than an IOException
      */
     protected void doFilterInternal(ServletRequest servletRequest, ServletResponse servletResponse, final FilterChain chain)
             throws ServletException, IOException {
 
         Throwable t = null;
 
         try {
             final ServletRequest request = prepareServletRequest(servletRequest, servletResponse, chain);
             final ServletResponse response = prepareServletResponse(request, servletResponse, chain);
 
             final Subject subject = createSubject(request, response);
 
             //noinspection unchecked
             subject.execute(new Callable() {
                 public Object call() throws Exception {
                     updateSessionLastAccessTime(request, response);
                     executeChain(request, response, chain);
                     return null;
                 }
             });
         } catch (ExecutionException ex) {
             t = ex.getCause();
         } catch (Throwable throwable) {
             t = throwable;
         }
 
         if (t != null) {
             if (t instanceof ServletException) {
                 throw (ServletException) t;
             }
             if (t instanceof IOException) {
                 throw (IOException) t;
             }
             //otherwise it's not one of the two exceptions expected by the filter method signature - wrap it in one:
             String msg = "Filtered request failed.";
             throw new ServletException(msg, t);
         }
     }
 
     /**
      * Returns the {@code FilterChain} to execute for the given request.
      * <p/>
      * The {@code origChain} argument is the
      * original {@code FilterChain} supplied by the Servlet Container, but it may be modified to provide
      * more behavior by pre-pending further chains according to the Shiro configuration.
      * <p/>
      * This implementation returns the chain that will actually be executed by acquiring the chain from a
      * {@link #getFilterChainResolver() filterChainResolver}.  The resolver determines exactly which chain to
      * execute, typically based on URL configuration.  If no chain is returned from the resolver call
      * (returns {@code null}), then the {@code origChain} will be returned by default.
      *
      * @param request   the incoming ServletRequest
      * @param response  the outgoing ServletResponse
      * @param origChain the original {@code FilterChain} provided by the Servlet Container
      * @return the {@link FilterChain} to execute for the given request
      * @since 1.0
      */
     protected FilterChain getExecutionChain(ServletRequest request, ServletResponse response, FilterChain origChain) {
         FilterChain chain = origChain;
 
         FilterChainResolver resolver = getFilterChainResolver();
         if (resolver == null) {
             log.debug("No FilterChainResolver configured.  Returning original FilterChain.");
             return origChain;
         }
 
         FilterChain resolved = resolver.getChain(request, response, origChain);
         if (resolved != null) {
             log.trace("Resolved a configured FilterChain for the current request.");
             chain = resolved;
         } else {
             log.trace("No FilterChain configured for the current request.  Using the default.");
         }
 
         return chain;
     }
 
     /**
      * Executes a {@link FilterChain} for the given request.
      * <p/>
      * This implementation first delegates to
      * <code>{@link #getExecutionChain(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain) getExecutionChain}</code>
      * to allow the application's Shiro configuration to determine exactly how the chain should execute.  The resulting
      * value from that call is then executed directly by calling the returned {@code FilterChain}'s
      * {@link FilterChain#doFilter doFilter} method.  That is:
      * <pre>
      * FilterChain chain = {@link #getExecutionChain}(request, response, origChain);
      * chain.{@link FilterChain#doFilter doFilter}(request,response);</pre>
      *
      * @param request   the incoming ServletRequest
      * @param response  the outgoing ServletResponse
      * @param origChain the Servlet Container-provided chain that may be wrapped further by an application-configured
      *                  chain of Filters.
      * @throws IOException      if the underlying {@code chain.doFilter} call results in an IOException
      * @throws ServletException if the underlying {@code chain.doFilter} call results in a ServletException
      * @since 1.0
      */
     protected void executeChain(ServletRequest request, ServletResponse response, FilterChain origChain)
             throws IOException, ServletException {
         FilterChain chain = getExecutionChain(request, response, origChain);
         chain.doFilter(request, response);
     }
 }