Merge pull request #314 from DataDog/vickenty/dhh

AGTMETRICS-489 Harden forwarder implementation

Author: vickenty

dogstatsd-http-forwarder/src/main/java/com/datadoghq/dogstatsd/http/forwarder/Forwarder.java

@@ -17,9 +17,11 @@
 import java.net.http.HttpResponse;
 import java.time.Duration;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Random;
 import java.util.logging.Level;
 import java.util.logging.Logger;
+import java.util.regex.Pattern;
 
 /**
  * An HTTP forwarder that delivers DogStatsD HTTP payloads to a remote endpoint.
@@ -77,12 +79,14 @@ public Telemetry.Snapshot snapshot() {
     /** Runs the forwarding loop, delivering queued payloads until the thread is interrupted. */
     @Override
     public void run() {
-        try {
-            while (true) {
+        while (true) {
+            try {
                 runOnce(queue.next());
+            } catch (InterruptedException e) {
+                return;
+            } catch (Exception t) {
+                logger.log(Level.SEVERE, "unexpected error in forwarder loop", t);
             }
-        } catch (InterruptedException e) {
-            return;
         }
     }
 
@@ -98,6 +102,8 @@ public void run() {
      *     ({@link WhenFull#BLOCK} mode only)
      */
     public void send(URI url, byte[] payload) throws InterruptedException {
+        Objects.requireNonNull(url, "url");
+        Objects.requireNonNull(payload, "payload");
         queue.add(new Payload(url, payload));
         telemetry.onEnqueue(payload.length);
     }
@@ -193,6 +199,7 @@ void backoff() throws InterruptedException {
      * @param data the local-data string, or {@code null} to omit the header
      */
     public void setLocalData(String data) {
+        validateHeaderValue(data);
         logger.log(Level.INFO, "using local data: {0}", data);
         localData = data;
     }
@@ -207,7 +214,19 @@ public void setLocalData(String data) {
      * @param data the external-data string, or {@code null} to omit the header
      */
     public void setExternalData(String data) {
+        validateHeaderValue(data);
         logger.log(Level.INFO, "using external data: {0}", data);
         externalData = data;
     }
+
+    private static final Pattern validHeaderValue = Pattern.compile("[\\t\\x20-\\x7E\\x80-\\xFF]*");
+
+    private static void validateHeaderValue(String value) {
+        if (value == null) {
+            return;
+        }
+        if (!validHeaderValue.matcher(value).matches()) {
+            throw new IllegalArgumentException("invalid character");
+        }
+    }
 }