Add IMDSv2 support to AwsCandidateHarvester and replace URLConnection… (#297)

* Add IMDSv2 support to AwsCandidateHarvester and replace URLConnection with HttpRequest
---------

Co-authored-by: Daniil Meitis <[email protected]>

Author: dsmeytis

src/main/java/org/ice4j/ice/harvest/AwsCandidateHarvester.java

@@ -19,8 +19,10 @@
 
 import org.ice4j.*;
 
-import java.io.*;
 import java.net.*;
+import java.net.http.*;
+import java.time.*;
+import java.util.*;
 import java.util.logging.*;
 
 /**
@@ -39,6 +41,14 @@ public class AwsCandidateHarvester
     private static final Logger logger
         = Logger.getLogger(AwsCandidateHarvester.class.getName());
 
+    /**
+     * The <tt>HttpClient</tt> used by the <tt>AwsCandidateHarvester</tt>
+     * class and its instances for making requests to IMDS.
+     */
+    private static final HttpClient httpClient = HttpClient.newBuilder()
+            .connectTimeout(Duration.ofMillis(500))
+            .build();
+
     /**
      * The URL where one obtains AWS public addresses.
      */
@@ -52,10 +62,28 @@ public class AwsCandidateHarvester
         = "http://169.254.169.254/latest/meta-data/local-ipv4";
 
     /**
-     * The URL to use to test whether we are running on Amazon EC2.
+     * The URL to get IMDSv2 API token for further meta-data requests.
+     */
+    private static final String IMDS_API_TOKEN_URL
+            = "http://169.254.169.254/latest/api/token";
+
+    /**
+     * The HTTP header name to provide session token.
      */
-    private static final String EC2_TEST_URL
-        = "http://169.254.169.254/latest/meta-data/";
+    private static final String EC2_METADATA_TOKEN_HEADER
+            = "X-aws-ec2-metadata-token";
+
+    /**
+     * The HTTP header name to request session token TTL.
+     */
+    private static final String EC2_METADATA_TOKEN_TTL_HEADER
+            = "X-aws-ec2-metadata-token-ttl-seconds";
+
+    /**
+     * The default session token TTL value.
+     */
+    private static final String EC2_METADATA_TOKEN_DEFAULT_TTL
+            = "21600";
 
     /**
      * Whether we are running on Amazon EC2.
@@ -103,8 +131,11 @@ private static synchronized void obtainEC2Addresses()
 
         try
         {
-            localIPStr = fetch(LOCAL_IP_URL);
-            publicIPStr = fetch(PUBLIC_IP_URL);
+            String metaDataToken = fetch(IMDS_API_TOKEN_URL,
+                    Collections.singletonMap(EC2_METADATA_TOKEN_TTL_HEADER, EC2_METADATA_TOKEN_DEFAULT_TTL), "PUT");
+            Map<String, String> tokenHeader = Collections.singletonMap(EC2_METADATA_TOKEN_HEADER, metaDataToken);
+            localIPStr = fetch(LOCAL_IP_URL, tokenHeader);
+            publicIPStr = fetch(PUBLIC_IP_URL, tokenHeader);
 
             //now let's cross our fingers and hope that what we got above are
             //real IP addresses
@@ -183,11 +214,10 @@ private static boolean doTestEc2()
     {
         try
         {
-            URLConnection conn = new URL(EC2_TEST_URL).openConnection();
-            conn.setConnectTimeout(500); //don't hang for too long
-            conn.getContent();
+            String metaDataToken = fetch(IMDS_API_TOKEN_URL,
+                    Collections.singletonMap(EC2_METADATA_TOKEN_TTL_HEADER, EC2_METADATA_TOKEN_DEFAULT_TTL), "PUT");
 
-            return true;
+            return metaDataToken != null;
         }
         catch(Exception exc)
         {
@@ -201,21 +231,40 @@ private static boolean doTestEc2()
      *
      * @param url the URL we'd like to open and query.
      *
+     * @param headers the HTTP headers to put into the request.
+     *
+     * @throws Exception if anything goes wrong.
+     */
+    private static String fetch(String url, Map<String, String> headers)
+            throws Exception
+    {
+        return fetch(url, headers, "GET");
+    }
+
+    /**
+     * Retrieves the content at the specified <tt>url</tt>. No more, no less.
+     *
+     * @param url the URL we'd like to open and query.
+     *
+     * @param headers the HTTP headers to put into the request.
+     *
+     * @param method the HTTP method we'd like to use.
+     *
      * @return the String we retrieved from the URL.
      *
      * @throws Exception if anything goes wrong.
      */
-    private static String fetch(String url)
+    private static String fetch(String url, Map<String, String> headers, String method)
         throws Exception
     {
-        URLConnection conn = new URL(url).openConnection();
-        BufferedReader in = new BufferedReader(new InputStreamReader(
-                    conn.getInputStream(), "UTF-8"));
-
-        String retString = in.readLine();
-
-        in.close();
-
-        return retString;
+        HttpRequest.Builder builder = HttpRequest.newBuilder()
+                .uri(new URI(url))
+                .method(method, HttpRequest.BodyPublishers.noBody());
+        for (Map.Entry<String, String> header : headers.entrySet())
+        {
+            builder.setHeader(header.getKey(), header.getValue());
+        }
+        HttpResponse<String> response = httpClient.send(builder.build(), HttpResponse.BodyHandlers.ofString());
+        return response.body();
     }
 }