Allow connecting to WiFi networks via Quick Settings

System UI acts on behalf of the current foreground user and should
thus be allowed to connect to WiFi networks, even if it actually runs
as user 0.

BUG=28799309

Change-Id: I50c3bdf30c9a1fd7780b47cac3f8ff3d0fb34f36

service/java/com/android/server/wifi/WifiStateMachine.java

@@ -990,6 +990,8 @@ public class WifiStateMachine extends StateMachine implements WifiNative.WifiRss
 
     private final BackupManagerProxy mBackupManagerProxy;
 
+    private int mSystemUiUid = -1;
+
     public WifiStateMachine(Context context, FrameworkFacade facade, Looper looper,
                             UserManager userManager, WifiInjector wifiInjector,
                             BackupManagerProxy backupManagerProxy,
@@ -1201,6 +1203,13 @@ public class WifiStateMachine extends StateMachine implements WifiNative.WifiRss
         intent.putExtra(WifiManager.EXTRA_SCAN_AVAILABLE, WIFI_STATE_DISABLED);
         mContext.sendStickyBroadcastAsUser(intent, UserHandle.ALL);
 
+        try {
+            mSystemUiUid = mContext.getPackageManager().getPackageUidAsUser("com.android.systemui",
+                    PackageManager.MATCH_SYSTEM_ONLY, UserHandle.USER_SYSTEM);
+        } catch (PackageManager.NameNotFoundException e) {
+            loge("Unable to resolve SystemUI's UID.");
+        }
+
         mVerboseLoggingLevel = mFacade.getIntegerSetting(
                 mContext, Settings.Global.WIFI_VERBOSE_LOGGING_ENABLED, 0);
         updateLoggingLevel();
@@ -5808,9 +5817,11 @@ public class WifiStateMachine extends StateMachine implements WifiNative.WifiRss
                     mWifiConfigManager.removeNetworksForUser(message.arg1);
                     break;
                 case WifiManager.CONNECT_NETWORK:
-                    // Only the current foreground user can modify networks.
+                    // Only the current foreground user and System UI (which runs as user 0 but acts
+                    // on behalf of the current foreground user) can modify networks.
                     if (!mWifiConfigManager.isCurrentUserProfile(
-                            UserHandle.getUserId(message.sendingUid))) {
+                            UserHandle.getUserId(message.sendingUid)) &&
+                            message.sendingUid != mSystemUiUid) {
                         loge("Only the current foreground user can modify networks "
                                 + " currentUserId=" + mWifiConfigManager.getCurrentUserId()
                                 + " sendingUserId=" + UserHandle.getUserId(message.sendingUid));