[FIXED JENKINS-35004] Disable console auth token at startup.

Otherwise, by default starting with SDK Tools 25.1.6, you need to authenticate
before you can start using the telnet interface.  So here we use the documented
way of disabling this feature, i.e. returning to the old behaviour.

src/main/java/hudson/plugins/android_emulator/AndroidEmulator.java

@@ -298,6 +298,10 @@ private Environment doSetUp(final AbstractBuild<?, ?> build, final Launcher laun
             launcher.getChannel().call(task);
         }
 
+        // Write the auth token file for the emulator
+        Callable<Void, IOException> authFileTask = emuConfig.getEmulatorAuthFileTask();
+        launcher.getChannel().callAsync(authFileTask);
+
         // Delay start up by the configured amount of time
         final int delaySecs = startupDelay;
         if (delaySecs > 0) {

src/main/java/hudson/plugins/android_emulator/EmulatorConfig.java

@@ -248,6 +248,15 @@ public Callable<Void, IOException> getEmulatorConfigTask(HardwareProperty[] hard
         return new EmulatorConfigTask(hardwareProperties, listener);
     }
 
+    /**
+     * Gets a task that writes an empty emulator auth file to the machine where the AVD will run.
+     *
+     * @return A Callable that will write an empty auth file.
+     */
+    public Callable<Void, IOException> getEmulatorAuthFileTask() {
+        return new EmulatorAuthFileTask();
+    }
+
     /**
      * Gets a task that deletes the AVD corresponding to this instance's configuration.
      *
@@ -707,6 +716,30 @@ public Void call() throws IOException {
         }
     }
 
+    /** Writes an empty emulator auth file. */
+    private final class EmulatorAuthFileTask extends MasterToSlaveCallable<Void, IOException> {
+
+        private static final long serialVersionUID = 1L;
+
+        public Void call() throws IOException {
+            // Create an empty auth file to prevent the emulator telnet interface from requiring authentication
+            final File userHome = Utils.getHomeDirectory();
+            if (userHome != null) {
+                try {
+                    FilePath authFile = new FilePath(userHome).child(".emulator_console_auth_token");
+                    authFile.write("", "UTF-8");
+                } catch (IOException e) {
+                    throw new IOException(String.format("Failed to write auth file to %s.", userHome, e));
+                } catch (InterruptedException e) {
+                    throw new IOException(String.format("Interrupted while writing auth file to %s.", userHome, e));
+                }
+            }
+
+            return null;
+        }
+
+    }
+
     /** A task that deletes the AVD corresponding to our local state. */
     private final class EmulatorDeletionTask extends MasterToSlaveCallable<Boolean, Exception> {
 

src/main/java/hudson/plugins/android_emulator/util/Utils.java

@@ -296,6 +296,37 @@ public static File getHomeDirectory(String androidSdkHome) {
         return new File(homeDirPath);
     }
 
+    /**
+     * Locates the current user's home directory using the same scheme as the Android SDK does.
+     *
+     * @return A {@link File} representing the home directory.
+     */
+    public static File getHomeDirectory() {
+        // From https://android.googlesource.com/platform/external/qemu/android/base/system/System.cpp
+        String path = null;
+        if (Functions.isWindows()) {
+            // The emulator queries for the Win32 "CSIDL_PROFILE" path, which should equal USERPROFILE
+            path = System.getenv("USERPROFILE");
+
+            // Otherwise, fall back to the Windows equivalent of HOME
+            if (path == null) {
+                String homeDrive = System.getenv("HOMEDRIVE");
+                String homePath = System.getenv("HOMEPATH");
+                if (homeDrive != null && homePath != null) {
+                    path = homeDrive + homePath;
+                }
+            }
+        } else {
+            path = System.getenv("HOME");
+        }
+
+        // Path may not have been discovered
+        if (path == null) {
+            return null;
+        }
+        return new File(path);
+    }
+
     /**
      * Detects the root directory of an SDK installation based on the Android tools on the PATH.
      *