Merge pull request #5195 from eclipse/jetty-9.4.x-5185-dosfilter-listener

Issue #5185 - Add DoSFilter Listener to allow extensible behavior

jetty-servlets/src/main/java/org/eclipse/jetty/servlets/DoSFilter.java

@@ -20,9 +20,13 @@ package org.eclipse.jetty.servlets;
 
 import java.io.IOException;
 import java.io.Serializable;
+import java.time.Duration;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
+import java.util.Objects;
 import java.util.Queue;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentLinkedQueue;
@@ -161,10 +165,13 @@ public class DoSFilter implements Filter
     static final String ENABLED_INIT_PARAM = "enabled";
     static final String TOO_MANY_CODE = "tooManyCode";
 
-    private static final int USER_AUTH = 2;
+    public enum RateType
-    private static final int USER_SESSION = 2;
+    {
-    private static final int USER_IP = 1;
+        AUTH,
-    private static final int USER_UNKNOWN = 0;
+        SESSION,
+        IP,
+        UNKNOWN
+    }
 
     private final String _suspended = "DoSFilter@" + Integer.toHexString(hashCode()) + ".SUSPENDED";
     private final String _resumed = "DoSFilter@" + Integer.toHexString(hashCode()) + ".RESUMED";
@@ -181,23 +188,22 @@ public class DoSFilter implements Filter
     private volatile boolean _remotePort;
     private volatile boolean _enabled;
     private volatile String _name;
+    private DoSFilter.Listener _listener = new Listener();
     private Semaphore _passes;
     private volatile int _throttledRequests;
     private volatile int _maxRequestsPerSec;
-    private Queue<AsyncContext>[] _queues;
+    private Map<RateType, Queue<AsyncContext>> _queues = new HashMap<>();
-    private AsyncListener[] _listeners;
+    private Map<RateType, AsyncListener> _listeners = new HashMap<>();
     private Scheduler _scheduler;
     private ServletContext _context;
 
     @Override
     public void init(FilterConfig filterConfig) throws ServletException
     {
-        _queues = new Queue[getMaxPriority() + 1];
+        for (RateType rateType : RateType.values())
-        _listeners = new AsyncListener[_queues.length];
-        for (int p = 0; p < _queues.length; p++)
         {
-            _queues[p] = new ConcurrentLinkedQueue<>();
+            _queues.put(rateType, new ConcurrentLinkedQueue<>());
-            _listeners[p] = new DoSAsyncListener(p);
+            _listeners.put(rateType, new DoSAsyncListener(rateType));
         }
 
         _rateTrackers.clear();
@@ -305,8 +311,13 @@ public class DoSFilter implements Filter
 
         // Look for the rate tracker for this request.
         RateTracker tracker = (RateTracker)request.getAttribute(__TRACKER);
-        if (tracker == null)
+        if (tracker != null)
         {
+            // Redispatched, RateTracker present in request attributes.
+            throttleRequest(request, response, filterChain, tracker);
+            return;
+        }
+
         // This is the first time we have seen this request.
         if (LOG.isDebugEnabled())
             LOG.debug("Filtering {}", request);
@@ -315,10 +326,10 @@ public class DoSFilter implements Filter
         tracker = getRateTracker(request);
 
         // Calculate the rate and check if it is over the allowed limit
-            final boolean overRateLimit = tracker.isRateExceeded(System.currentTimeMillis());
+        final OverLimit overLimit = tracker.isRateExceeded(System.currentTimeMillis());
 
         // Pass it through if we are not currently over the rate limit.
-            if (!overRateLimit)
+        if (overLimit == null)
         {
             if (LOG.isDebugEnabled())
                 LOG.debug("Allowing {}", request);
@@ -328,32 +339,32 @@ public class DoSFilter implements Filter
 
         // We are over the limit.
 
-            // So either reject it, delay it or throttle it.
+        // Ask listener what to perform.
+        Action action = _listener.onRequestOverLimit(request, overLimit, this);
+
+        // Perform action
         long delayMs = getDelayMs();
         boolean insertHeaders = isInsertHeaders();
-            switch ((int)delayMs)
+        switch (action)
         {
-                case -1:
+            case NO_ACTION:
-                {
+                if (LOG.isDebugEnabled())
-                    // Reject this request.
+                    LOG.debug("Allowing over-limit request {}", request);
-                    LOG.warn("DOS ALERT: Request rejected ip={}, session={}, user={}", request.getRemoteAddr(), request.getRequestedSessionId(), request.getUserPrincipal());
+                doFilterChain(filterChain, request, response);
+                break;
+            case ABORT:
+                if (LOG.isDebugEnabled())
+                    LOG.debug("Aborting over-limit request {}", request);
+                response.sendError(-1);
+                return;
+            case REJECT:
                 if (insertHeaders)
                     response.addHeader("DoSFilter", "unavailable");
                 response.sendError(getTooManyCode());
                 return;
-                }
+            case DELAY:
-                case 0:
-                {
-                    // Fall through to throttle the request.
-                    LOG.warn("DOS ALERT: Request throttled ip={}, session={}, user={}", request.getRemoteAddr(), request.getRequestedSessionId(), request.getUserPrincipal());
-                    request.setAttribute(__TRACKER, tracker);
-                    break;
-                }
-                default:
-                {
                 // Insert a delay before throttling the request,
                 // using the suspend+timeout mechanism of AsyncContext.
-                    LOG.warn("DOS ALERT: Request delayed={}ms, ip={}, session={}, user={}", delayMs, request.getRemoteAddr(), request.getRequestedSessionId(), request.getUserPrincipal());
                 if (insertHeaders)
                     response.addHeader("DoSFilter", "delayed");
                 request.setAttribute(__TRACKER, tracker);
@@ -361,11 +372,15 @@ public class DoSFilter implements Filter
                 if (delayMs > 0)
                     asyncContext.setTimeout(delayMs);
                 asyncContext.addListener(new DoSTimeoutAsyncListener());
-                    return;
+                break;
-                }
+            case THROTTLE:
+                throttleRequest(request, response, filterChain, tracker);
+                break;
         }
     }
 
+    private void throttleRequest(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain, RateTracker tracker) throws IOException, ServletException
+    {
         if (LOG.isDebugEnabled())
             LOG.debug("Throttling {}", request);
 
@@ -383,15 +398,15 @@ public class DoSFilter implements Filter
                 long throttleMs = getThrottleMs();
                 if (!Boolean.TRUE.equals(throttled) && throttleMs > 0)
                 {
-                    int priority = getPriority(request, tracker);
+                    RateType priority = getPriority(request, tracker);
                     request.setAttribute(__THROTTLED, Boolean.TRUE);
                     if (isInsertHeaders())
                         response.addHeader("DoSFilter", "throttled");
                     AsyncContext asyncContext = request.startAsync();
                     request.setAttribute(_suspended, Boolean.TRUE);
                     asyncContext.setTimeout(throttleMs);
-                    asyncContext.addListener(_listeners[priority]);
+                    asyncContext.addListener(_listeners.get(priority));
-                    _queues[priority].add(asyncContext);
+                    _queues.get(priority).add(asyncContext);
                     if (LOG.isDebugEnabled())
                         LOG.debug("Throttled {}, {}ms", request, throttleMs);
                     return;
@@ -436,9 +451,9 @@ public class DoSFilter implements Filter
                 try
                 {
                     // Wake up the next highest priority request.
-                    for (int p = _queues.length - 1; p >= 0; --p)
+                    for (RateType rateType : RateType.values())
                     {
-                        AsyncContext asyncContext = _queues[p].poll();
+                        AsyncContext asyncContext = _queues.get(rateType).poll();
                         if (asyncContext != null)
                         {
                             ServletRequest candidate = asyncContext.getRequest();
@@ -530,21 +545,31 @@ public class DoSFilter implements Filter
      * @param tracker the rate tracker for this request
      * @return the priority for this request
      */
-    private int getPriority(HttpServletRequest request, RateTracker tracker)
+    private RateType getPriority(HttpServletRequest request, RateTracker tracker)
     {
         if (extractUserId(request) != null)
-            return USER_AUTH;
+            return RateType.AUTH;
         if (tracker != null)
             return tracker.getType();
-        return USER_UNKNOWN;
+        return RateType.UNKNOWN;
     }
 
     /**
      * @return the maximum priority that we can assign to a request
      */
-    protected int getMaxPriority()
+    protected RateType getMaxPriority()
     {
-        return USER_AUTH;
+        return RateType.AUTH;
+    }
+
+    public void setListener(DoSFilter.Listener listener)
+    {
+        _listener = Objects.requireNonNull(listener, "Listener may not be null");
+    }
+
+    public DoSFilter.Listener getListener()
+    {
+        return _listener;
     }
 
     private void schedule(RateTracker tracker)
@@ -573,22 +598,22 @@ public class DoSFilter implements Filter
         HttpSession session = ((HttpServletRequest)request).getSession(false);
 
         String loadId = extractUserId(request);
-        final int type;
+        final RateType type;
         if (loadId != null)
         {
-            type = USER_AUTH;
+            type = RateType.AUTH;
         }
         else
         {
             if (isTrackSessions() && session != null && !session.isNew())
             {
                 loadId = session.getId();
-                type = USER_SESSION;
+                type = RateType.SESSION;
             }
             else
             {
                 loadId = isRemotePort() ? createRemotePortId(request) : request.getRemoteAddr();
-                type = USER_IP;
+                type = RateType.IP;
             }
         }
 
@@ -605,7 +630,7 @@ public class DoSFilter implements Filter
             if (existing != null)
                 tracker = existing;
 
-            if (type == USER_IP)
+            if (type == RateType.IP)
             {
                 // USER_IP expiration from _rateTrackers is handled by the _scheduler
                 _scheduler.schedule(tracker, getMaxIdleTrackerMs(), TimeUnit.MILLISECONDS);
@@ -1062,6 +1087,11 @@ public class DoSFilter implements Filter
         _enabled = enabled;
     }
 
+    /**
+     * Status code for Rejected for too many requests.
+     *
+     * @return the configured status code (default: 429 - Too Many Requests)
+     */
     public int getTooManyCode()
     {
         return _tooManyCode;
@@ -1150,6 +1180,13 @@ public class DoSFilter implements Filter
         return _whitelist.remove(address);
     }
 
+    private String createRemotePortId(ServletRequest request)
+    {
+        String addr = request.getRemoteAddr();
+        int port = request.getRemotePort();
+        return addr + ":" + port;
+    }
+
     /**
      * A RateTracker is associated with a connection, and stores request rate
      * data.
@@ -1161,17 +1198,19 @@ public class DoSFilter implements Filter
         protected final String _filterName;
         protected transient ServletContext _context;
         protected final String _id;
-        protected final int _type;
+        protected final RateType _type;
+        protected final int _maxRequestsPerSecond;
         protected final long[] _timestamps;
 
         protected int _next;
 
-        public RateTracker(ServletContext context, String filterName, String id, int type, int maxRequestsPerSecond)
+        public RateTracker(ServletContext context, String filterName, String id, RateType type, int maxRequestsPerSecond)
         {
             _context = context;
             _filterName = filterName;
             _id = id;
             _type = type;
+            _maxRequestsPerSecond = maxRequestsPerSecond;
             _timestamps = new long[maxRequestsPerSecond];
             _next = 0;
         }
@@ -1180,7 +1219,7 @@ public class DoSFilter implements Filter
          * @param now the time now (in milliseconds)
          * @return the current calculated request rate over the last second
          */
-        public boolean isRateExceeded(long now)
+        public OverLimit isRateExceeded(long now)
         {
             final long last;
             synchronized (this)
@@ -1190,7 +1229,17 @@ public class DoSFilter implements Filter
                 _next = (_next + 1) % _timestamps.length;
             }
 
-            return last != 0 && (now - last) < 1000L;
+            if (last == 0)
+            {
+                return null;
+            }
+
+            long rate = (now - last);
+            if (rate < 1000L)
+            {
+                return new Overage(Duration.ofMillis(rate), _maxRequestsPerSecond);
+            }
+            return null;
         }
 
         public String getId()
@@ -1198,7 +1247,7 @@ public class DoSFilter implements Filter
             return _id;
         }
 
-        public int getType()
+        public RateType getType()
         {
             return _type;
         }
@@ -1271,7 +1320,7 @@ public class DoSFilter implements Filter
         {
             if (_context == null)
             {
-                LOG.warn("Unknkown context for rate tracker {}", this);
+                LOG.warn("Unknown context for rate tracker {}", this);
                 return;
             }
 
@@ -1297,17 +1346,66 @@ public class DoSFilter implements Filter
         {
             return "RateTracker/" + _id + "/" + _type;
         }
+
+        public class Overage implements OverLimit
+        {
+            private final Duration duration;
+            private final long count;
+
+            public Overage(Duration dur, long count)
+            {
+                this.duration = dur;
+                this.count = count;
+            }
+
+            @Override
+            public RateType getRateType()
+            {
+                return _type;
+            }
+
+            @Override
+            public String getRateId()
+            {
+                return _id;
+            }
+
+            @Override
+            public Duration getDuration()
+            {
+                return duration;
+            }
+
+            @Override
+            public long getCount()
+            {
+                return count;
+            }
+
+            @Override
+            public String toString()
+            {
+                final StringBuilder sb = new StringBuilder(OverLimit.class.getSimpleName());
+                sb.append('@').append(Integer.toHexString(hashCode()));
+                sb.append("[type=").append(getRateType());
+                sb.append(", id=").append(getRateId());
+                sb.append(", duration=").append(duration);
+                sb.append(", count=").append(count);
+                sb.append(']');
+                return sb.toString();
+            }
+        }
     }
 
     private static class FixedRateTracker extends RateTracker
     {
-        public FixedRateTracker(ServletContext context, String filterName, String id, int type, int numRecentRequestsTracked)
+        public FixedRateTracker(ServletContext context, String filterName, String id, RateType type, int numRecentRequestsTracked)
         {
             super(context, filterName, id, type, numRecentRequestsTracked);
         }
 
         @Override
-        public boolean isRateExceeded(long now)
+        public OverLimit isRateExceeded(long now)
         {
             // rate limit is never exceeded, but we keep track of the request timestamps
             // so that we know whether there was recent activity on this tracker
@@ -1318,7 +1416,7 @@ public class DoSFilter implements Filter
                 _next = (_next + 1) % _timestamps.length;
             }
 
-            return false;
+            return null;
         }
 
         @Override
@@ -1354,9 +1452,9 @@ public class DoSFilter implements Filter
 
     private class DoSAsyncListener extends DoSTimeoutAsyncListener
     {
-        private final int priority;
+        private final RateType priority;
 
-        public DoSAsyncListener(int priority)
+        public DoSAsyncListener(RateType priority)
         {
             this.priority = priority;
         }
@@ -1364,15 +1462,93 @@ public class DoSFilter implements Filter
         @Override
         public void onTimeout(AsyncEvent event) throws IOException
         {
-            _queues[priority].remove(event.getAsyncContext());
+            _queues.get(priority).remove(event.getAsyncContext());
             super.onTimeout(event);
         }
     }
 
-    private String createRemotePortId(ServletRequest request)
+    public enum Action
     {
-        String addr = request.getRemoteAddr();
+        /**
-        int port = request.getRemotePort();
+         * No action is taken against the Request, it is allowed to be processed normally.
-        return addr + ":" + port;
+         */
+        NO_ACTION,
+        /**
+         * The request and response is aborted, no response is sent.
+         */
+        ABORT,
+        /**
+         * The request is rejected by sending an error based on {@link DoSFilter#getTooManyCode()}
+         */
+        REJECT,
+        /**
+         * The request is delayed based on {@link DoSFilter#getDelayMs()}
+         */
+        DELAY,
+        /**
+         * The request is throttled.
+         */
+        THROTTLE;
+
+        /**
+         * Obtain the Action based on configured {@link DoSFilter#getDelayMs()}
+         *
+         * @param delayMs the delay in milliseconds.
+         * @return the Action proposed.
+         */
+        public static Action fromDelay(long delayMs)
+        {
+            if (delayMs < 0)
+                return Action.REJECT;
+
+            if (delayMs == 0)
+                return Action.THROTTLE;
+
+            return Action.DELAY;
+        }
+    }
+
+    public interface OverLimit
+    {
+        RateType getRateType();
+
+        String getRateId();
+
+        Duration getDuration();
+
+        long getCount();
+    }
+
+    /**
+     * Listener for actions taken against specific requests.
+     */
+    public static class Listener
+    {
+        /**
+         * Process the onRequestOverLimit() behavior.
+         *
+         * @param request the request that is over the limit
+         * @param dosFilter the {@link DoSFilter} that this event occurred on
+         * @return the action to actually perform.
+         */
+        public Action onRequestOverLimit(HttpServletRequest request, OverLimit overlimit, DoSFilter dosFilter)
+        {
+            Action action = Action.fromDelay(dosFilter.getDelayMs());
+
+            switch (action)
+            {
+                case REJECT:
+                    LOG.warn("DOS ALERT: Request rejected ip={}, overlimit={}, session={}, user={}", request.getRemoteAddr(), overlimit, request.getRequestedSessionId(), request.getUserPrincipal());
+                    break;
+                case DELAY:
+                    LOG.warn("DOS ALERT: Request delayed={}ms, ip={}, overlimit={}, session={}, user={}", dosFilter.getDelayMs(), request.getRemoteAddr(), overlimit, request.getRequestedSessionId(), request.getUserPrincipal());
+                    break;
+                case THROTTLE:
+                    LOG.warn("DOS ALERT: Request throttled ip={}, overlimit={}, session={}, user={}", request.getRemoteAddr(), overlimit, request.getRequestedSessionId(), request.getUserPrincipal());
+                    break;
+            }
+
+            return action;
+        }
     }
 }

jetty-servlets/src/test/java/org/eclipse/jetty/servlets/DoSFilterTest.java

@@ -174,12 +174,12 @@ public class DoSFilterTest extends AbstractDoSFilterTest
     {
         boolean exceeded = false;
         ServletContext context = new ContextHandler.StaticContext();
-        RateTracker rateTracker = new RateTracker(context, doSFilter.getName(), "test2", 0, 4);
+        RateTracker rateTracker = new RateTracker(context, doSFilter.getName(), "test2", DoSFilter.RateType.UNKNOWN, 4);
 
         for (int i = 0; i < 5; i++)
         {
             Thread.sleep(sleep);
-            if (rateTracker.isRateExceeded(TimeUnit.NANOSECONDS.toMillis(System.nanoTime())))
+            if (rateTracker.isRateExceeded(TimeUnit.NANOSECONDS.toMillis(System.nanoTime())) != null)
                 exceeded = true;
         }
         return exceeded;