It turns out that although HttpFirewall and StrictHttpFirewall contain several design errors (documented in the code below), it is just barely possible to escape Spring Security's One True Firewall and tunnel the HttpFirewall information via a request attribute to a HandlerInterceptor that can pass these flagged requests to a real (persistent) firewall without sacrificing the original business logic that flagged them in the first place. The method documented here should be fairly future-proof, as it conforms to a simple contract from the HttpFirewall interface, and the rest is simply the core Spring Framework and Java Servlet API.
This is essentially a more complicated but more complete alternative to my earlier answer. In this answer, I implemented a new subclass of StrictHttpFirewall that intercepts and logs rejected requests at a specific logging level, but also adds an attribute to the HTTP request that flags it for downstream filters (or controllers) to handle. Also, this AnnotatingHttpFirewall provides an inspect() method that allows subclasses to add custom rules for blocking requests.
This solution is split into two parts: (1) Spring Security and (2) Spring Framework (Core), because that is the divide that caused this problem in the first place, and this shows how to bridge it.
For reference, this is tested on Spring 4.3.17 and Spring Security 4.2.6. There may be significant changes when Spring 5.1 is released.
Part 1: Spring Security
This is the half of the solution that performs the logging and flagging within Spring Security.
AnnotatingHttpFirewall.java
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.security.web.firewall.FirewalledRequest;
import org.springframework.security.web.firewall.RequestRejectedException;
import org.springframework.security.web.firewall.StrictHttpFirewall;
/**
* Overrides the StrictHttpFirewall to log some useful information about blocked requests.
*/
public class AnnotatingHttpFirewall extends StrictHttpFirewall
{
/**
* The name of the HTTP header representing a request that has been rejected by this firewall.
*/
public static final String HTTP_HEADER_REQUEST_REJECTED_FLAG = "X-HttpFirewall-RequestRejectedFlag";
/**
* The name of the HTTP header representing the reason a request has been rejected by this firewall.
*/
public static final String HTTP_HEADER_REQUEST_REJECTED_REASON = "X-HttpFirewall-RequestRejectedReason";
/**
* Logger.
*/
private static final Logger LOGGER = Logger.getLogger(AnnotatingHttpFirewall.class.getName());
/**
* Default constructor.
*/
public AnnotatingHttpFirewall()
{
super();
return;
}
/**
* Provides the request object which will be passed through the filter chain.
*
* @param request The original HttpServletRequest.
* @returns A FirewalledRequest (required by the HttpFirewall interface) which
* inconveniently breaks the general contract of ServletFilter because
* we can't upcast this to an HttpServletRequest. This prevents us
* from re-wrapping this using an HttpServletRequestWrapper.
*/
@Override
public FirewalledRequest getFirewalledRequest(final HttpServletRequest request)
{
try
{
this.inspect(request); // Perform any additional checks that the naive "StrictHttpFirewall" misses.
return super.getFirewalledRequest(request);
} catch (RequestRejectedException ex) {
final String requestUrl = request.getRequestURL().toString();
// Override some of the default behavior because some requests are
// legitimate.
if (requestUrl.contains(";jsessionid="))
{
// Do not block non-cookie serialized sessions. Google's crawler does this often.
} else {
// Log anything that is blocked so we can find these in the catalina.out log.
// This will give us any information we need to make
// adjustments to these special cases and see potentially
// malicious activity.
if (LOGGER.isLoggable(Level.WARNING))
{
LOGGER.log(Level.WARNING, "Intercepted RequestBlockedException: Remote Host: " + request.getRemoteHost() + " User Agent: " + request.getHeader("User-Agent") + " Request URL: " + request.getRequestURL().toString());
}
// Mark this request as rejected.
request.setAttribute(HTTP_HEADER_REQUEST_REJECTED, Boolean.TRUE);
request.setAttribute(HTTP_HEADER_REQUEST_REJECTED_REASON, ex.getMessage());
}
// Suppress the RequestBlockedException and pass the request through
// with the additional attribute.
return new FirewalledRequest(request)
{
@Override
public void reset()
{
return;
}
};
}
}
/**
* Provides the response which will be passed through the filter chain.
* This method isn't extensible because the request may already be committed.
* Furthermore, this is only invoked for requests that were not blocked, so we can't
* control the status or response for blocked requests here.
*
* @param response The original HttpServletResponse.
* @return the original response or a replacement/wrapper.
*/
@Override
public HttpServletResponse getFirewalledResponse(final HttpServletResponse response)
{
// Note: The FirewalledResponse class is not accessible outside the package.
return super.getFirewalledResponse(response);
}
/**
* Perform any custom checks on the request.
* This method may be overridden by a subclass in order to supplement or replace these tests.
*
* @param request The original HttpServletRequest.
* @throws RequestRejectedException if the request should be rejected immediately.
*/
public void inspect(final HttpServletRequest request) throws RequestRejectedException
{
final String requestUri = request.getRequestURI(); // path without parameters
// final String requestUrl = request.getRequestURL().toString(); // full path with parameters
if (requestUri.endsWith("/wp-login.php"))
{
throw new RequestRejectedException("The request was rejected because it is a vulnerability scan.");
}
if (requestUri.endsWith(".php"))
{
throw new RequestRejectedException("The request was rejected because it is a likely vulnerability scan.");
}
return; // The request passed all custom tests.
}
}
WebSecurityConfig.java
In WebSecurityConfig, set the HTTP firewall to the AnnotatingHttpFirewall.
@EnableWebSecurity
public class WebSecurityConfig extends WebSecurityConfigurerAdapter
{
/**
* Default constructor.
*/
public WebSecurityConfig()
{
super();
return;
}
@Override
public final void configure(final WebSecurity web) throws Exception
{
super.configure(web);
web.httpFirewall(new AnnotatingHttpFirewall()); // Set the custom firewall.
return;
}
}
Part 2: Spring Framework
The second part of this solution could conceivably be implemented as a ServletFilter or HandlerInterceptor. I'm going the path of a HandlerInterceptor because it seems to give the most flexibility and works directly within the Spring Framework.
RequestBlockedException.java
This custom exception can be handled by an Error Controller. This may be extended to add any request headers, parameters or properties available from the raw request (even the full request itself) that may be pertinent to application business logic (e.g., a persistent firewall).
/**
* A custom exception for situations where a request is blocked or rejected.
*/
public class RequestBlockedException extends RuntimeException
{
private static final long serialVersionUID = 1L;
/**
* The requested URL.
*/
private String requestUrl;
/**
* The remote address of the client making the request.
*/
private String remoteAddress;
/**
* A message or reason for blocking the request.
*/
private String reason;
/**
* The user agent supplied by the client the request.
*/
private String userAgent;
/**
* Creates a new Request Blocked Exception.
*
* @param reqUrl The requested URL.
* @param remoteAddr The remote address of the client making the request.
* @param userAgent The user agent supplied by the client making the request.
* @param message A message or reason for blocking the request.
*/
public RequestBlockedException(final String reqUrl, final String remoteAddr, final String userAgent, final String message)
{
this.requestUrl = reqUrl;
this.remoteAddress = remoteAddr;
this.userAgent = userAgent;
this.reason = message;
return;
}
/**
* Gets the requested URL.
*
* @return A URL.
*/
public String getRequestUrl()
{
return this.requestUrl;
}
/**
* Gets the remote address of the client making the request.
*
* @return A remote address.
*/
public String getRemoteAddress()
{
return this.remoteAddress;
}
/**
* Gets the user agent supplied by the client making the request.
*
* @return A user agent string.
*/
public String getUserAgent()
{
return this.userAgent;
}
/**
* Gets the reason for blocking the request.
*
* @return A message or reason for blocking the request.
*/
public String getReason()
{
return this.reason;
}
}
FirewallInterceptor.java
This interceptor is invoked after the Spring Security filters have run (i.e., after AnnotatingHttpFirewall has flagged requests that should be rejected. This interceptor detects those flags (attributes) on the request and raises a custom exception that our Error Controller can handle.
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
/**
* Intercepts requests that were flagged as rejected by the firewall.
*/
public final class FirewallInterceptor implements HandlerInterceptor
{
/**
* Default constructor.
*/
public FirewallInterceptor()
{
return;
}
@Override
public boolean preHandle(final HttpServletRequest request, final HttpServletResponse response, final Object handler) throws Exception
{
if (Boolean.TRUE.equals(request.getAttribute(AnnotatingHttpFirewall.HTTP_HEADER_REQUEST_REJECTED)))
{
// Throw a custom exception that can be handled by a custom error controller.
final String reason = (String) request.getAttribute(AnnotatingHttpFirewall.HTTP_HEADER_REQUEST_REJECTED_REASON);
throw new RequestRejectedByFirewallException(request.getRequestURL().toString(), request.getRemoteAddr(), request.getHeader(HttpHeaders.USER_AGENT), reason);
}
return true; // Allow the request to proceed normally.
}
@Override
public void postHandle(final HttpServletRequest request, final HttpServletResponse response, final Object handler, final ModelAndView modelAndView) throws Exception
{
return;
}
@Override
public void afterCompletion(final HttpServletRequest request, final HttpServletResponse response, final Object handler, final Exception ex) throws Exception
{
return;
}
}
WebConfig.java
In WebConfig, add the FirewallInterceptor to the registry.
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter
{
/**
* Among your other methods in this class, make sure you register
* your Interceptor.
*/
@Override
public void addInterceptors(final InterceptorRegistry registry)
{
// Register firewall interceptor for all URLs in webapp.
registry.addInterceptor(new FirewallInterceptor()).addPathPatterns("/**");
return;
}
}
ErrorController.java
This specifically handles the custom exception above, and produces a clean error page for the client while logging all of the relevant information and invoking any special business logic for a custom application firewall.
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.springframework.web.servlet.NoHandlerFoundException;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseStatus;
import RequestBlockedException;
@ControllerAdvice
public final class ErrorController
{
/**
* Logger.
*/
private static final Logger LOGGER = Logger.getLogger(ErrorController.class.getName());
/**
* Generates an Error page by intercepting exceptions generated from AnnotatingHttpFirewall.
*
* @param request The original HTTP request.
* @param ex A RequestBlockedException exception.
* @return The tile definition name for the page.
*/
@ExceptionHandler(RequestBlockedException.class)
@ResponseStatus(HttpStatus.BAD_REQUEST)
public String handleRequestBlockedException(final RequestBlockedException ex)
{
if (LOGGER.isLoggable(Level.WARNING))
{
LOGGER.log(Level.WARNING, "Rejected request from " + ex.getRemoteAddress() + " for [" + ex.getRequestUrl() + "]. Reason: " + ex.getReason());
}
// Note: Perform any additional business logic or logging here.
return "errorPage"; // Returns a nice error page with the specified status code.
}
/**
* Generates a Page Not Found page.
*
* @param ex A NoHandlerFound exception.
* @return The tile definition name for the page.
*/
@ExceptionHandler(NoHandlerFoundException.class)
@ResponseStatus(HttpStatus.NOT_FOUND)
public String handleException(final NoHandlerFoundException ex)
{
return "notFoundPage";
}
}
FirewallController.java
A controller with a default mapping that throws a NoHandlerFoundException.
This circumvents the chicken-and-egg strategy in DispatcherServlet.noHandlerFound, allowing that method to always find a mapping so that FirewallInterceptor.preHandle is always invoked. This gives RequestRejectedByFirewallException priority over NoHandlerFoundException.
Why this is necessary:
As mentioned here, when a NoHandlerFoundException is thrown from DispatcherServlet (i.e., when a requested URL has no corresponding mapping), there is no way to handle the exceptions generated from the above firewall (NoHandlerFoundException is thrown prior to invoking preHandle()), so those requests will fall through to your 404 view (which is not the desired behavior in my case - you will see a lot of "No mapping found for HTTP request with URI..." messages). This could be fixed by moving the check for the special header into the noHandlerFound method. Unfortunately, there is no way to do this without writing a new Dispatcher Servlet from scratch, and then you may as well throw out the entire Spring Framework. It is impossible to extend DispatcherServlet due to the mix of protected, private and final methods, and the fact that its properties are inaccessible (no getters or setters). It is also impossible to wrap the class because there is no common interface that can be implemented. The default mapping in this class provides an elegant way to circumvent all of that logic.
Important caveat: The RequestMapping below will prevent resolution of static resources because it takes precedence over all registered ResourceHandlers. I am still looking for a workaround for this, but one possibility might be to try one of the methods for handling static resources suggested in this answer.
import org.springframework.http.HttpHeaders;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.NoHandlerFoundException;
@Controller
public final class FirewallController
{
/**
* The name of the model attribute (or request parameter for advertisement click tracking) that contains the request URL.
*/
protected static final String REQUEST_URL = "requestUrl";
/**
* The name of the model attribute that contains the request method.
*/
protected static final String REQUEST_METHOD = "requestMethod";
/**
* The name of the model attribute that contains all HTTP headers.
*/
protected static final String REQUEST_HEADERS = "requestHeaders";
/**
* Default constructor.
*/
public FirewallController()
{
return;
}
/**
* Populates the request URL model attribute from the HTTP request.
*
* @param request The HTTP request.
* @return The request URL.
*/
@ModelAttribute(REQUEST_URL)
public final String getRequestURL(final HttpServletRequest request)
{
return request.getRequestURL().toString();
}
/**
* Populates the request method from the HTTP request.
*
* @param request The HTTP request.
* @return The request method (GET, POST, HEAD, etc.).
*/
@ModelAttribute(REQUEST_METHOD)
public final String getRequestMethod(final HttpServletRequest request)
{
return request.getMethod();
}
/**
* Gets all headers from the HTTP request.
*
* @param request The HTTP request.
* @return The request headers.
*/
@ModelAttribute(REQUEST_HEADERS)
public final HttpHeaders getRequestHeaders(final HttpServletRequest request)
{
return FirewallController.headers(request);
}
/**
* A catch-all default mapping that throws a NoHandlerFoundException.
* This will be intercepted by the ErrorController, which allows preHandle to work normally.
*
* @param requestMethod The request method.
* @param requestUrl The request URL.
* @param requestHeaders The request headers.
* @throws NoHandlerFoundException every time this method is invoked.
*/
@RequestMapping(value = "/**") // NOTE: This prevents resolution of static resources. Still looking for a workaround for this.
public void getNotFoundPage(@ModelAttribute(REQUEST_METHOD) final String requestMethod, @ModelAttribute(REQUEST_URL) final String requestUrl, @ModelAttribute(REQUEST_HEADERS) final HttpHeaders requestHeaders) throws NoHandlerFoundException
{
throw new NoHandlerFoundException(requestMethod, requestUrl, requestHeaders);
}
/**
* Gets all headers from a HTTP request.
*
* @param request The HTTP request.
* @return The request headers.
*/
public static HttpHeaders headers(final HttpServletRequest request)
{
final HttpHeaders headers = new HttpHeaders();
for (Enumeration<?> names = request.getHeaderNames(); names.hasMoreElements();)
{
final String headerName = (String) names.nextElement();
for (Enumeration<?> headerValues = request.getHeaders(headerName); headerValues.hasMoreElements();)
{
headers.add(headerName, (String) headerValues.nextElement());
}
}
return headers;
}
}
Results
When both parts of this are working, you'll see the following two warnings logged (the first one is in Spring Security, the second one is the Spring Framework (Core) ErrorController). Now you have full control over logging, and an extensible application firewall that you can adjust however you need.
Sep 12, 2018 10:24:37 AM com.mycompany.spring.security.AnnotatingHttpFirewall getFirewalledRequest
WARNING: Intercepted org.springframework.security.web.firewall.RequestRejectedException: Remote Host: 0:0:0:0:0:0:0:1 User Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:62.0) Gecko/20100101 Firefox/62.0 Request URL: http://localhost:8080/webapp-www-mycompany-com/login.php
Sep 12, 2018 10:24:37 AM com.mycompany.spring.controller.ErrorController handleException
WARNING: Rejected request from 0:0:0:0:0:0:0:1 for [http://localhost:8080/webapp-www-mycompany-com/login.php]. Reason: The request was rejected because it is a likely vulnerability scan.
