diff --git a/zxingorg/src/main/java/com/google/zxing/web/DoSFilter.java b/zxingorg/src/main/java/com/google/zxing/web/DoSFilter.java new file mode 100644 index 000000000..69805057b --- /dev/null +++ b/zxingorg/src/main/java/com/google/zxing/web/DoSFilter.java @@ -0,0 +1,129 @@ +/* + * Copyright 2015 ZXing authors + * + * Licensed 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 com.google.zxing.web; + +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.annotation.WebFilter; +import javax.servlet.http.HttpServletRequest; +import javax.servlet.http.HttpServletResponse; +import java.io.IOException; +import java.util.Collections; +import java.util.HashSet; +import java.util.LinkedHashMap; +import java.util.Map; +import java.util.Set; +import java.util.Timer; +import java.util.TimerTask; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicInteger; +import java.util.logging.Logger; + +/** + * A simplistic {@link Filter} that rejects requests from hosts that are sending too many + * requests in too short a time. + * + * @author Sean Owen + */ +@WebFilter("/w/decode") +public final class DoSFilter implements Filter { + + private static final Logger log = Logger.getLogger(DoSFilter.class.getName()); + + private static final int MAX_ACCESSES_PER_IP_PER_TIME = 10; + private static final int MAX_RECENT_ACCESS_MAP_SIZE = 100_000; + + private Map numRecentAccesses; + private Set bannedIPAddresses; + private Timer timer; + + @Override + public void init(FilterConfig filterConfig) { + numRecentAccesses = Collections.synchronizedMap(new LinkedHashMap() { + @Override + protected boolean removeEldestEntry(Map.Entry eldest) { + return size() > MAX_RECENT_ACCESS_MAP_SIZE; + } + }); + bannedIPAddresses = Collections.synchronizedSet(new HashSet()); + timer = new Timer("DoSFilter reset timer"); + timer.scheduleAtFixedRate( + new TimerTask() { + @Override + public void run() { + numRecentAccesses.clear(); + } + }, 0L, TimeUnit.MILLISECONDS.convert(1, TimeUnit.MINUTES)); + timer.scheduleAtFixedRate( + new TimerTask() { + @Override + public void run() { + bannedIPAddresses.clear(); + } + }, 0L, TimeUnit.MILLISECONDS.convert(15, TimeUnit.MINUTES)); + } + + @Override + public void doFilter(ServletRequest request, + ServletResponse response, + FilterChain chain) throws IOException, ServletException { + if (isBanned((HttpServletRequest) request)) { + HttpServletResponse servletResponse = (HttpServletResponse) response; + servletResponse.sendError(HttpServletResponse.SC_FORBIDDEN); + } else { + chain.doFilter(request, response); + } + } + + private boolean isBanned(HttpServletRequest request) { + String remoteIPAddress = request.getHeader("x-forwarded-for"); + if (remoteIPAddress == null) { + remoteIPAddress = request.getRemoteAddr(); + } + if (remoteIPAddress == null || bannedIPAddresses.contains(remoteIPAddress)) { + return true; + } + if (getCount(remoteIPAddress) > MAX_ACCESSES_PER_IP_PER_TIME) { + log.warning("Possible DoS attack from " + remoteIPAddress); + bannedIPAddresses.add(remoteIPAddress); + return true; + } + return false; + } + + private int getCount(String remoteIPAddress) { + synchronized (numRecentAccesses) { + AtomicInteger count = numRecentAccesses.get(remoteIPAddress); + if (count == null) { + numRecentAccesses.put(remoteIPAddress, new AtomicInteger(1)); + return 1; + } else { + return count.incrementAndGet(); + } + } + } + + @Override + public void destroy() { + timer.cancel(); + } + +} \ No newline at end of file