i2psnark standalone: Add DNS rebinding protection

Add context config file to turn it off
Console: Mark request handled when rejecting in HostCheckHandler
XSSFilter: Catch cascaded ISE

apps/i2psnark/i2psnark-appctx.config

@@ -0,0 +1,4 @@
+#
+# This is for app context configuration of standalone i2psnark.
+# Almost all configuration settings are in i2psnark.config.d/i2psnark.config
+#

apps/i2psnark/java/build.xml

@@ -50,10 +50,11 @@
                 <pathelement location="../../jetty/jettylib/javax.servlet.jar" />
                 <!-- jsp-api.jar only present for debian builds -->
                 <pathelement location="../../jetty/jettylib/jsp-api.jar" />
-                <!-- jetty-i2p.jar only for RunStandalone -->
+                <!-- following jars only for standalone builds -->
                 <pathelement location="../../jetty/jettylib/jetty-i2p.jar" />
-                <!-- systray.jar only for RunStandalone -->
                 <pathelement location="../../systray/java/build/systray.jar" />
+                <pathelement location="../../jetty/jettylib/org.mortbay.jetty.jar" />
+                <pathelement location="../../jetty/jettylib/jetty-util.jar" />
             </classpath>
         </javac>
     </target>
@@ -319,6 +320,7 @@
         <mkdir dir="./dist/webapps" />
         <copy file="../i2psnark.war" tofile="./dist/webapps/i2psnark.war" />
         <copy file="../jetty-i2psnark.xml" tofile="./dist/jetty-i2psnark.xml" />
+        <copy file="../i2psnark-appctx.config" tofile="./dist/i2psnark-appctx.config" />
         <copy file="./build/i2psnark-standalone.jar" tofile="./dist/i2psnark.jar" />
         <copy file="../readme-standalone.txt" tofile="./dist/readme.txt" />
         <!-- temp so announces work -->

apps/i2psnark/java/src/org/klomp/snark/standalone/HostCheckHandler.java

@@ -0,0 +1,136 @@
+package org.klomp.snark.standalone;
+
+import java.io.IOException;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.StringTokenizer;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+import net.i2p.I2PAppContext;
+import net.i2p.util.Log;
+
+import org.apache.http.conn.util.InetAddressUtils;
+
+import org.eclipse.jetty.server.Request;
+import org.eclipse.jetty.server.handler.AbstractHandler;
+
+/**
+ * Block certain Host headers to prevent DNS rebinding attacks.
+ *
+ * Unlike in the console, this is an AbstractHandler, not a HandlerWrapper.
+ *
+ * @since 0.9.34 adapted from router console
+ */
+public class HostCheckHandler extends AbstractHandler {
+    private final I2PAppContext _context;
+    private final Set<String> _listenHosts;
+    private static final String PROP_ALLOWED_HOSTS = "i2psnark.allowedHosts";
+
+    public HostCheckHandler() {
+        this(I2PAppContext.getGlobalContext());
+    }
+
+    public HostCheckHandler(I2PAppContext ctx) {
+        super();
+        _context = ctx;
+        _listenHosts = new HashSet<String>(8);
+        _listenHosts.add("127.0.0.1");
+        _listenHosts.add("::1");
+        _listenHosts.add("localhost");
+        String allowed = _context.getProperty(PROP_ALLOWED_HOSTS);
+        if (allowed != null) {
+            StringTokenizer tok = new StringTokenizer(allowed, " ,");
+            while (tok.hasMoreTokens()) {
+                _listenHosts.add(tok.nextToken());
+            }
+        }
+    }
+    
+    /**
+     *  Unused, we can't get here from RunStandalone
+     *
+     *  @param hosts contains hostnames or IPs. But we allow all IPs anyway.
+     */
+    public void setListenHosts(Set<String> hosts) {
+        _listenHosts.clear();
+        _listenHosts.addAll(hosts);
+    }
+
+    /**
+     *  Block by Host header,
+     *  redirect HTTP to HTTPS,
+     *  pass everything else to the delegate.
+     */
+    public void handle(String pathInContext,
+                       Request baseRequest,
+                       HttpServletRequest httpRequest,
+                       HttpServletResponse httpResponse)
+         throws IOException, ServletException
+    {
+
+        String host = httpRequest.getHeader("Host");
+        if (!allowHost(host)) {
+            Log log = _context.logManager().getLog(HostCheckHandler.class);
+            host = getHost(host);
+            String s = "Console request denied.\n" +
+                       "    To allow access using the hostname \"" + host + "\", add the line \"" +
+                       PROP_ALLOWED_HOSTS + '=' + host +
+                       "\" in the file " + RunStandalone.APP_CONFIG_FILE.getAbsolutePath() + " and restart.";
+            log.logAlways(Log.WARN, s);
+            httpResponse.sendError(403, s);
+            baseRequest.setHandled(true);
+            return;
+        }
+    }
+
+    /**
+     *  Should we allow a request with this Host header?
+     *
+     *  ref: https://en.wikipedia.org/wiki/DNS_rebinding
+     *
+     *  @param host the HTTP Host header, null ok
+     *  @return true if OK
+     */
+    private boolean allowHost(String host) {
+        if (host == null)
+            return true;
+        // common cases
+        if (host.equals("127.0.0.1:8002") ||
+            host.equals("localhost:8002") ||
+            host.equals("[::1]:8002"))
+            return true;
+        // all allowed?
+        if (_listenHosts.isEmpty())
+            return true;
+        host = getHost(host);
+        if (_listenHosts.contains(host))
+            return true;
+        // allow all IP addresses
+        if (InetAddressUtils.isIPv4Address(host) || InetAddressUtils.isIPv6Address(host))
+            return true;
+        //System.out.println(host + " not found in " + s);
+        return false;
+    }
+
+    /**
+     *  Strip [] and port from a host header
+     *
+     *  @param host the HTTP Host header non-null
+     */
+    private static String getHost(String host) {
+        if (host.startsWith("[")) {
+            host = host.substring(1);
+            int brack = host.indexOf(']');
+            if (brack >= 0)
+                host = host.substring(0, brack);
+        } else {
+            int colon = host.indexOf(':');
+            if (colon >= 0)
+                host = host.substring(0, colon);
+        }
+        return host;
+    }
+}

apps/i2psnark/java/src/org/klomp/snark/standalone/RunStandalone.java

@@ -1,9 +1,12 @@
 package org.klomp.snark.standalone;
 
 import java.io.File;
+import java.io.IOException;
+import java.util.Properties;
 
 import net.i2p.I2PAppContext;
 import net.i2p.apps.systray.UrlLauncher;
+import net.i2p.data.DataHelper;
 import net.i2p.jetty.JettyStart;
 
 /**
@@ -16,9 +19,16 @@ public class RunStandalone {
     private int _port = 8002;
     private String _host = "127.0.0.1";
     private static RunStandalone _instance;
+    static final File APP_CONFIG_FILE = new File("i2psnark-appctx.config");
 
     private RunStandalone(String args[]) throws Exception {
-        _context = I2PAppContext.getGlobalContext();
+        Properties p = new Properties();
+        if (APP_CONFIG_FILE.exists()) {
+            try {
+                DataHelper.loadProps(p, APP_CONFIG_FILE);
+            } catch (IOException ioe) {}
+        }
+        _context = new I2PAppContext(p);
         File base = _context.getBaseDir();
         File xml = new File(base, "jetty-i2psnark.xml");
         _jettyStart = new JettyStart(_context, null, new String[] { xml.getAbsolutePath() } );

apps/i2psnark/java/src/org/klomp/snark/standalone/package.html

@@ -0,0 +1,7 @@
+<html>
+<body>
+<p>
+Classes only used for, and bundled with, the standalone installation. Since 0.9.27.
+</p>
+</body>
+</html>

apps/i2psnark/jetty-i2psnark.xml

@@ -55,6 +55,9 @@
       <New id="Handlers" class="org.eclipse.jetty.server.handler.HandlerCollection">
         <Set name="handlers">
          <Array type="org.eclipse.jetty.server.Handler">
+           <Item>
+             <New id="HostChecker" class="org.klomp.snark.standalone.HostCheckHandler"/>
+           </Item>
            <Item>
              <New id="Contexts" class="org.eclipse.jetty.server.handler.ContextHandlerCollection"/>
            </Item>

apps/jetty/java/src/net/i2p/servlet/filters/XSSFilter.java

@@ -33,7 +33,11 @@ public class XSSFilter implements Filter {
             // We need to send the error quickly, if we just throw a ServletException,
             // the data keeps coming and the connection gets reset.
             // This way we at least get the error to the browser.
+            try {
                 ((HttpServletResponse)response).sendError(413, ise.getMessage());
+            } catch (IllegalStateException ise2) {
+                // Committed, probably wasn't a multipart form error after all
+            }
         }
     }
 }

apps/routerconsole/java/src/net/i2p/router/web/HostCheckHandler.java

@@ -78,6 +78,7 @@ public class HostCheckHandler extends HandlerWrapper
                        "\" to advanced configuration and restart.";
             log.logAlways(Log.WARN, s);
             httpResponse.sendError(403, s);
+            baseRequest.setHandled(true);
             return;
         }
 
@@ -92,6 +93,7 @@ public class HostCheckHandler extends HandlerWrapper
                 if (Boolean.valueOf(redir) ||
                     (redir == null && "1".equals(httpRequest.getHeader("Upgrade-Insecure-Requests")))) {
                     sendRedirect(httpsPort, httpRequest, httpResponse);
+                    baseRequest.setHandled(true);
                     return;
                 }
             }