Fixed a minecraft exploit allowing anyone to pick their username

src/main/java/net/minecraft/server/ThreadLoginVerifier.java

@@ -0,0 +1,37 @@
+package net.minecraft.server;
+
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.net.URL;
+import java.net.URLEncoder;
+
+class ThreadLoginVerifier extends Thread {
+
+    final Packet1Login a;
+
+    final NetLoginHandler b;
+
+    ThreadLoginVerifier(NetLoginHandler netloginhandler, Packet1Login packet1login) {
+        this.b = netloginhandler;
+        this.a = packet1login;
+    }
+
+    public void run() {
+        try {
+            String s = NetLoginHandler.a(this.b);
+            // Craftbukkit
+            URL url = new URL("http://www.minecraft.net/game/checkserver.jsp?user=" + URLEncoder.encode(this.a.b, "UTF-8") + "&serverId=" + URLEncoder.encode(s, "UTF-8"));
+            BufferedReader bufferedreader = new BufferedReader(new InputStreamReader(url.openStream()));
+            String s1 = bufferedreader.readLine();
+
+            bufferedreader.close();
+            if (s1.equals("YES")) {
+                NetLoginHandler.a(this.b, this.a);
+            } else {
+                this.b.a("Failed to verify username!");
+            }
+        } catch (Exception exception) {
+            exception.printStackTrace();
+        }
+    }
+}