Added basic Mojang account authentication support for development time login.

src/main/java/cpw/mods/fml/common/launcher/FMLTweaker.java

@@ -21,11 +21,8 @@ import com.google.common.collect.Maps;
 import cpw.mods.fml.relauncher.FMLLaunchHandler;
 
 public class FMLTweaker implements ITweaker {
-    @SuppressWarnings("unused")
     private List<String> args;
-    @SuppressWarnings("unused")
     private File assetsDir;
-    @SuppressWarnings("unused")
     private String profile;
     private File gameDir;
     private Map<String, String> launchArgs;
@@ -97,6 +94,8 @@ public class FMLTweaker implements ITweaker {
             launchArgs.put("--assetsDir", assetsDir.getAbsolutePath());
         }
 
+        Yggdrasil.login(launchArgs);
+
         try
         {
             jarLocation = getClass().getProtectionDomain().getCodeSource().getLocation().toURI();

src/main/java/cpw/mods/fml/common/launcher/Yggdrasil.java

@@ -0,0 +1,131 @@
+package cpw.mods.fml.common.launcher;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.HttpURLConnection;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.commons.io.IOUtils;
+
+import com.google.common.base.Charsets;
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+
+/**
+ * Basic implementation of Mojang's 'Yggdrasil' login system, purely intended as a dev time bare bones login.
+ * Login errors are not handled.
+ */
+public class Yggdrasil {
+    private static class Request {
+        Agent agent = new Agent();
+        String username;
+        String password;
+        String clientToken = null;
+        boolean requestUser = true;
+
+        public Request(String username, String password){
+          this.username = username;
+          this.password = password;
+        }
+
+        private static class Agent {
+            String name = "Minecraft";
+            int version = 1;
+        }
+    }
+
+    private static class Response {
+        String error;
+        String errorMessage;
+        String cause;
+        String accessToken;
+        String clientToken;
+        Profile selectedProfile;
+        Profile[] availableProfiles;
+        User user;
+
+        private static class Profile {
+            String id;
+            String name;
+            boolean legacy;
+        }
+
+        private static class User {
+            String id;
+            List<Property> properties;
+
+            private static class Property {
+                String name;
+                String value;
+            }
+        }
+    }
+
+    private static void close(Closeable c)
+    {
+        if (c != null) {
+            try {
+                c.close();
+            } catch (IOException e){}
+        }
+    }
+
+    public static void login(Map<String, String> args)
+    {
+        if (!args.containsKey("--username") || !args.containsKey("--password")) return;
+
+        String username = args.get("--username");
+        String password = args.remove("--password");
+
+        Gson GSON = new GsonBuilder().setPrettyPrinting().create();
+        String request = GSON.toJson(new Request(username, password));
+
+        OutputStream out = null;
+        InputStream in = null;
+
+        try 
+        {
+            HttpURLConnection con = (HttpURLConnection)(new URL("https://authserver.mojang.com/authenticate")).openConnection();
+            con.setConnectTimeout(15000);
+            con.setReadTimeout(15000);
+            con.setUseCaches(false);
+
+            byte[] data = request.getBytes(Charsets.UTF_8);
+
+            con.setRequestProperty("Content-Type", "application/json; charset=utf-8");
+            con.setRequestProperty("Content-Length", Integer.toString(data.length));
+            con.setDoOutput(true);
+
+            out = con.getOutputStream();
+            out.write(data);
+
+            in = con.getInputStream();
+            Response result = GSON.fromJson(IOUtils.toString(in, Charsets.UTF_8), Response.class);
+
+            if (result.selectedProfile != null)
+            {
+                args.put("--username", result.selectedProfile.name);
+                args.put("--uuid",     result.selectedProfile.id);
+                args.put("--accessToken", result.accessToken);
+            }
+        }
+        catch (MalformedURLException e)
+        {
+            e.printStackTrace();
+        }
+        catch (IOException e)
+        {
+            e.printStackTrace();
+        }
+        finally
+        {
+            close(out);
+            close(in);
+        }
+    }
+}