Caching Secured Content caching-secured-content

Permission-sensitive caching enables you to cache secured pages. Dispatcher checks the user’s access permissions for a page before delivering the cached page.

Dispatcher includes the AuthChecker module that implements permission-sensitive caching. When the module is activated, the Dispatcher calls an AEM servlet to perform user authentication and authorization for the requested content. The servlet response determines whether the content is delivered to the web browser from the cache or not.

Because the methods of authentication and authorization are specific to the AEM deployment, you are required to create the servlet.

The following diagrams illustrate the order of events that occur when a web browser requests a page for which permission-sensitive caching is used.

Page is cached and user is authorized page-is-cached-and-user-is-authorized

Page is not cached and user is authorized page-is-not-cached-and-user-is-authorized

User is not authorized user-is-not-authorized

Implementing permission-sensitive caching implementing-permission-sensitive-caching

To implement permission-sensitive caching, perform the following tasks:

Create the Auth Checker servlet create-the-auth-checker-servlet

Create and deploy a servlet that performs the authentication and authorization of the user who requests the web content. The servlet can use any authentication. It can also use any authorization method. For example, it can use the AEM user account and repository ACLs. Or, it can use an LDAP lookup service. You deploy the servlet to the AEM instance that Dispatcher uses as the render.

The servlet must be accessible to all users. Therefore, your servlet should extend the org.apache.sling.api.servlets.SlingSafeMethodsServlet class, which provides read-only access to the system.

The servlet receives only HEAD requests from the render, so you only must implement the doHead method.

The render includes the URI of the requested resource as a parameter of the HTTP request. For example, an authorization servlet is accessed via /bin/permissioncheck. To perform a security check on the /content/geometrixx-outdoors/en.html page, the render includes the following URL in the HTTP request:

/bin/permissioncheck?uri=/content/geometrixx-outdoors/en.html

The servlet response message must contain the following HTTP status codes:

The following example servlet obtains the URL of the requested resource from the HTTP request. The code uses the Felix SCR Property annotation to set the value of the sling.servlet.paths property to /bin/permissioncheck. In the doHead method, the servlet obtains the session object and uses the checkPermission method to determine the appropriate response code.

Example servlet example-servlet

package com.adobe.example;

import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Service;
import org.apache.felix.scr.annotations.Property;

import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.api.servlets.SlingSafeMethodsServlet;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.jcr.Session;

@Component(metatype=false)
@Service
public class AuthcheckerServlet extends SlingSafeMethodsServlet {

    @Property(value="/bin/permissioncheck")
    static final String SERVLET_PATH="sling.servlet.paths";

    private Logger logger = LoggerFactory.getLogger(this.getClass());

    public void doHead(SlingHttpServletRequest request, SlingHttpServletResponse response) {
     try{
      //retrieve the requested URL
      String uri = request.getParameter("uri");
      //obtain the session from the request
      Session session = request.getResourceResolver().adaptTo(javax.jcr.Session.class);
      //perform the permissions check
      try {
       session.checkPermission(uri, Session.ACTION_READ);
       logger.info("authchecker says OK");
       response.setStatus(SlingHttpServletResponse.SC_OK);
      } catch(Exception e) {
       logger.info("authchecker says READ access DENIED!");
       response.setStatus(SlingHttpServletResponse.SC_FORBIDDEN);
      }
     }catch(Exception e){
      logger.error("authchecker servlet exception: " + e.getMessage());
     }
    }
}

Configure Dispatcher for permission-sensitive caching configure-dispatcher-for-permission-sensitive-caching

The auth_checker section of the dispatcher.any file controls the behavior of permission-sensitive caching. The auth_checker section includes the following subsections:

When Dispatcher starts, the Dispatcher log file includes the following debug-level message:

AuthChecker: initialized with URL 'configured_url'.

The following example auth_checker section configures the Dispatcher to use the servlet of the previous topic. The filter section causes permission checks to be performed only on secure HTML resources.

Example configuration example-configuration

/auth_checker
  {
  # request is sent to this URL with '?uri=<page>' appended
  /url "/bin/permissioncheck"

  # only the requested pages matching the filter section below are checked,
  # all other pages get delivered unchecked
  /filter
    {
    /0000
      {
      /glob "*"
      /type "deny"
      }
    /0001
      {
      /glob "/content/secure/*.html"
      /type "allow"
      }
    }
  # any header line returned from the auth_checker's HEAD request matching
  # the section below will be returned as well
  /headers
    {
    /0000
      {
      /glob "*"
      /type "deny"
      }
    /0001
      {
      /glob "Set-Cookie:*"
      /type "allow"
      }
    }
  }