星光/宝骏/缤果/长安 车机CarPlay盒子权限破解原理普及----码农版本

从 app 申请 usbdevice 权限说起，通用 app 申请 usbdevice 权限代码如下

一般通过监听 ACTION_USB_DEVICE_ATTACHED usb 设备插入广播获取 UsbDevice 设备，或者通过 UsbManager 枚举出我们感兴趣的 UsbDevice 设备

然后调用 requestPermission(UsbDevice, PendingIntent) 申请权限，这时候系统一般会弹对话框询问是否允许访问usb设备，用户点确定或取消都将

收到自定义的回调广播 ACTION_USB_PERMISSION

 private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";public void getPermission() {HashMap<String, UsbDevice> deviceList = usbManager.getDeviceList();Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();PendingIntent mPermissionIntent = PendingIntent.getBroadcast(AdbActivity.this, 0, new Intent(ACTION_USB_PERMISSION), 0);IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);registerReceiver(mUsbReceiver, filter);while(deviceIterator.hasNext()){UsbDevice device = deviceIterator.next();Log.d("AdbActivity", "getPermission: "+device.getDeviceName());if (device.getDeviceName().contains("/dev/bus/usb/001")) {if (usbManager.hasPermission(device)){Toast.makeText(AdbActivity.this,"已授权", Toast.LENGTH_SHORT).show();usbManager.openDevice(device);}else {usbManager.requestPermission(device, mPermissionIntent);}}}}private BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {public void onReceive(Context context, Intent intent) {String action = intent.getAction();if (ACTION_USB_PERMISSION.equals(action)){synchronized (this) {UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {if(device != null){usbManager.openDevice(device);hintText.setText("openDevice");}}else {Toast.makeText(context,"permission denied for device ", Toast.LENGTH_SHORT).show();Log.d("AdbActivity", "permission denied for device " + device);}}}}};

接下来分析下系统弹权限框已经授权流程

UsbManager 其实调用 UsbService 中 requestDevicePermission()

UsbService 调用 UsbUserSettingsManager 中 requestPermission()

frameworks\base\services\usb\java\com\android\server\usb\UsbService.java

    @Overridepublic void requestDevicePermission(UsbDevice device, String packageName, PendingIntent pi) {final int uid = Binder.getCallingUid();final int userId = UserHandle.getUserId(uid);final long token = Binder.clearCallingIdentity();try {getSettingsForUser(userId).requestPermission(device, packageName, pi, uid);} finally {Binder.restoreCallingIdentity(token);}}private UsbUserSettingsManager getSettingsForUser(@UserIdInt int userIdInt) {return mSettingsManager.getSettingsForUser(userIdInt);}

frameworks\base\services\usb\java\com\android\server\usb\UsbSettingsManager.java

	@NonNull UsbUserSettingsManager getSettingsForUser(@UserIdInt int userId) {synchronized (mSettingsByUser) {UsbUserSettingsManager settings = mSettingsByUser.get(userId);if (settings == null) {settings = new UsbUserSettingsManager(mContext, UserHandle.of(userId),new UsbPermissionManager(mContext, UserHandle.of(userId)));mSettingsByUser.put(userId, settings);}return settings;}}

先判断 UsbDevice 是否已经授权，若已授权，直接将 PendingIntent 扔回去

若无授权，则准备走弹出申请权限框 requestPermissionDialog()

其实最终调用 UsbPermissionManager 中 requestPermissionDialog()

frameworks\base\services\usb\java\com\android\server\usb\UsbUserSettingsManager.java

	public void requestPermission(UsbDevice device, String packageName, PendingIntent pi, int uid) {Intent intent = new Intent();// respond immediately if permission has already been grantedif (hasPermission(device, packageName, uid)) {intent.putExtra(UsbManager.EXTRA_DEVICE, device);intent.putExtra(UsbManager.EXTRA_PERMISSION_GRANTED, true);try {pi.send(mUserContext, 0, intent);} catch (PendingIntent.CanceledException e) {if (DEBUG) Slog.d(TAG, "requestPermission PendingIntent was cancelled");}return;}if (isCameraDevicePresent(device)) {if (!isCameraPermissionGranted(packageName, uid)) {intent.putExtra(UsbManager.EXTRA_DEVICE, device);intent.putExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false);try {pi.send(mUserContext, 0, intent);} catch (PendingIntent.CanceledException e) {if (DEBUG) Slog.d(TAG, "requestPermission PendingIntent was cancelled");}return;}}requestPermissionDialog(device, null, canBeDefault(device, packageName), packageName, pi,uid);}private void requestPermissionDialog(@Nullable UsbDevice device,@Nullable UsbAccessory accessory,boolean canBeDefault,String packageName,PendingIntent pi,int uid) {// compare uid with packageName to foil apps pretending to be someone elsetry {ApplicationInfo aInfo = mPackageManager.getApplicationInfo(packageName, 0);if (aInfo.uid != uid) {throw new IllegalArgumentException("package " + packageName +" does not match caller's uid " + uid);}} catch (PackageManager.NameNotFoundException e) {throw new IllegalArgumentException("package " + packageName + " not found");}mUsbPermissionManager.requestPermissionDialog(device,accessory, canBeDefault, packageName, uid, mUserContext, pi);}

可以看到直接指定了包名和类名，最终是拉起 SystemUI 中 UsbPermissionActivity

frameworks\base\services\usb\java\com\android\server\usb\UsbPermissionManager.java

 /*** Creates UI dialog to request permission for the given package to access the device* or accessory.** @param device The USB device attached* @param accessory The USB accessory attached* @param canBeDefault Whether the calling pacakge can set as default handler* of the USB device or accessory* @param packageName The package name of the calling package* @param uid The uid of the calling package* @param userContext The context to start the UI dialog* @param pi PendingIntent for returning result*/void requestPermissionDialog(@Nullable UsbDevice device,@Nullable UsbAccessory accessory,boolean canBeDefault,@NonNull String packageName,int uid,@NonNull Context userContext,@NonNull PendingIntent pi) {long identity = Binder.clearCallingIdentity();Intent intent = new Intent();if (device != null) {intent.putExtra(UsbManager.EXTRA_DEVICE, device);} else {intent.putExtra(UsbManager.EXTRA_ACCESSORY, accessory);}intent.putExtra(Intent.EXTRA_INTENT, pi);intent.putExtra(Intent.EXTRA_UID, uid);intent.putExtra(UsbManager.EXTRA_CAN_BE_DEFAULT, canBeDefault);intent.putExtra(UsbManager.EXTRA_PACKAGE, packageName);intent.setClassName("com.android.systemui","com.android.systemui.usb.UsbPermissionActivity");intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);try {userContext.startActivityAsUser(intent, mUser);} catch (ActivityNotFoundException e) {Slog.e(LOG_TAG, "unable to start UsbPermissionActivity");} finally {Binder.restoreCallingIdentity(identity);}}

UsbPermissionActivity 就一个普通 AlertActivity，通常很多系统开发人员做默认授权时都会来改这里，

将 mPermissionGranted=true，直接 finish() 这样就能达到默认授权且不弹框的目的，因为最终授权是在ondestory()中

核心方法就下面两个，一个是仅授权一次，另一个是总是授权(前提是apk没被卸载，apk卸载后授权也会情况)

service.grantDevicePermission(mDevice, mUid);

service.setDevicePackage(mDevice, mPackageName, userId);

饶了半天又得回到 UsbService 中了

frameworks\base\packages\SystemUI\src\com\android\systemui\usb\UsbPermissionActivity.java

   <activity android:name=".usb.UsbPermissionActivity"android:exported="true"android:permission="android.permission.MANAGE_USB"android:theme="@style/Theme.SystemUI.Dialog.Alert"android:finishOnCloseSystemDialogs="true"android:excludeFromRecents="true"></activity>@Overridepublic void onDestroy() {IBinder b = ServiceManager.getService(USB_SERVICE);IUsbManager service = IUsbManager.Stub.asInterface(b);// send response via pending intentIntent intent = new Intent();try {if (mDevice != null) {intent.putExtra(UsbManager.EXTRA_DEVICE, mDevice);if (mPermissionGranted) {service.grantDevicePermission(mDevice, mUid);if (mAlwaysUse != null && mAlwaysUse.isChecked()) {final int userId = UserHandle.getUserId(mUid);service.setDevicePackage(mDevice, mPackageName, userId);}}}if (mAccessory != null) {intent.putExtra(UsbManager.EXTRA_ACCESSORY, mAccessory);if (mPermissionGranted) {service.grantAccessoryPermission(mAccessory, mUid);if (mAlwaysUse != null && mAlwaysUse.isChecked()) {final int userId = UserHandle.getUserId(mUid);service.setAccessoryPackage(mAccessory, mPackageName, userId);}}}intent.putExtra(UsbManager.EXTRA_PERMISSION_GRANTED, mPermissionGranted);mPendingIntent.send(this, 0, intent);} catch (PendingIntent.CanceledException e) {Log.w(TAG, "PendingIntent was cancelled");} catch (RemoteException e) {Log.e(TAG, "IUsbService connection failed", e);}if (mDisconnectedReceiver != null) {unregisterReceiver(mDisconnectedReceiver);}super.onDestroy();}

frameworks\base\services\usb\java\com\android\server\usb\UsbService.java
frameworks\base\services\usb\java\com\android\server\usb\UsbUserSettingsManager.java
frameworks\base\services\usb\java\com\android\server\usb\UsbPermissionManager.java

可以看到仅授权一次其实最终就是将 device 和 uid 保存到 mDevicePermissionMap 中

看注释可知这只是一个临时的权限机制

/** Temporary mapping USB device name to list of UIDs with permissions for the device*/
private final HashMap<String, SparseBooleanArray> mDevicePermissionMap = new HashMap<>();

	@Overridepublic void grantDevicePermission(UsbDevice device, int uid) {mContext.enforceCallingOrSelfPermission(android.Manifest.permission.MANAGE_USB, null);final int userId = UserHandle.getUserId(uid);final long token = Binder.clearCallingIdentity();try {getSettingsForUser(userId).grantDevicePermission(device, uid);} finally {Binder.restoreCallingIdentity(token);}}public void grantDevicePermission(UsbDevice device, int uid) {mUsbPermissionManager.grantDevicePermission(device, uid);}void grantDevicePermission(@NonNull UsbDevice device, int uid) {synchronized (mLock) {String deviceName = device.getDeviceName();SparseBooleanArray uidList = mDevicePermissionMap.get(deviceName);if (uidList == null) {uidList = new SparseBooleanArray(1);mDevicePermissionMap.put(deviceName, uidList);}uidList.put(uid, true);}}boolean hasPermission(@NonNull UsbDevice device, int uid) {synchronized (mLock) {if (uid == Process.SYSTEM_UID || mDisablePermissionDialogs) {return true;}SparseBooleanArray uidList = mDevicePermissionMap.get(device.getDeviceName());if (uidList == null) {return false;}return uidList.get(uid);}}

再看看下持久保存授权是怎么做到的，调用 UsbProfileGroupSettingsManager 中 setDevicePackage()

packageName 为空，将 device 信息从 mDevicePreferenceMap 中移除，changed 改变重新修改 mSettingsFile 内容

mSettingsFile 实际路径为 data/system/users/0/usb_device_manager.xml

因为安卓支持多用户登录，默认用户id为0，这就是参数中为什么有 userId 原因，用于区分不同用户的操作数据

packageName 不为空，将 device 信息添加到 mDevicePreferenceMap 中，changed 改变写入数据到 mSettingsFile

frameworks\base\services\usb\java\com\android\server\usb\UsbService.java
frameworks\base\services\usb\java\com\android\server\usb\UsbProfileGroupSettingsManager.java

	@Overridepublic void setDevicePackage(UsbDevice device, String packageName, int userId) {device = Preconditions.checkNotNull(device);mContext.enforceCallingOrSelfPermission(android.Manifest.permission.MANAGE_USB, null);UserHandle user = UserHandle.of(userId);final long token = Binder.clearCallingIdentity();try {mSettingsManager.getSettingsForProfileGroup(user).setDevicePackage(device, packageName,user);} finally {Binder.restoreCallingIdentity(token);}}void setDevicePackage(@NonNull UsbDevice device, @Nullable String packageName,@NonNull UserHandle user) {DeviceFilter filter = new DeviceFilter(device);boolean changed;synchronized (mLock) {if (packageName == null) {changed = (mDevicePreferenceMap.remove(filter) != null);} else {UserPackage userPackage = new UserPackage(packageName, user);changed = !userPackage.equals(mDevicePreferenceMap.get(filter));if (changed) {mDevicePreferenceMap.put(filter, userPackage);}}if (changed) {scheduleWriteSettingsLocked();}}}mSettingsFile = new AtomicFile(new File(Environment.getUserSystemDirectory(user.getIdentifier()),"usb_device_manager.xml"), "usb-state");private void scheduleWriteSettingsLocked() {if (mIsWriteSettingsScheduled) {return;} else {mIsWriteSettingsScheduled = true;}AsyncTask.execute(() -> {synchronized (mLock) {FileOutputStream fos = null;try {fos = mSettingsFile.startWrite();FastXmlSerializer serializer = new FastXmlSerializer();serializer.setOutput(fos, StandardCharsets.UTF_8.name());serializer.startDocument(null, true);serializer.setFeature("http://xmlpull.org/v1/doc/features.html#indent-output",true);serializer.startTag(null, "settings");for (DeviceFilter filter : mDevicePreferenceMap.keySet()) {serializer.startTag(null, "preference");serializer.attribute(null, "package",mDevicePreferenceMap.get(filter).packageName);serializer.attribute(null, "user",String.valueOf(getSerial(mDevicePreferenceMap.get(filter).user)));filter.write(serializer);serializer.endTag(null, "preference");}for (AccessoryFilter filter : mAccessoryPreferenceMap.keySet()) {serializer.startTag(null, "preference");serializer.attribute(null, "package",mAccessoryPreferenceMap.get(filter).packageName);serializer.attribute(null, "user", String.valueOf(getSerial(mAccessoryPreferenceMap.get(filter).user)));filter.write(serializer);serializer.endTag(null, "preference");}serializer.endTag(null, "settings");serializer.endDocument();mSettingsFile.finishWrite(fos);} catch (IOException e) {Slog.e(TAG, "Failed to write settings", e);if (fos != null) {mSettingsFile.failWrite(fos);}}mIsWriteSettingsScheduled = false;}});}

最终 DeviceFilter write() 将 usbdevice 关键信息写入 xml 中

frameworks/base/core/java/android/hardware/usb/DeviceFilter.java

public void write(XmlSerializer serializer) throws IOException {serializer.startTag(null, "usb-device");if (mVendorId != -1) {serializer.attribute(null, "vendor-id", Integer.toString(mVendorId));}if (mProductId != -1) {serializer.attribute(null, "product-id", Integer.toString(mProductId));}if (mClass != -1) {serializer.attribute(null, "class", Integer.toString(mClass));}if (mSubclass != -1) {serializer.attribute(null, "subclass", Integer.toString(mSubclass));}if (mProtocol != -1) {serializer.attribute(null, "protocol", Integer.toString(mProtocol));}if (mManufacturerName != null) {serializer.attribute(null, "manufacturer-name", mManufacturerName);}if (mProductName != null) {serializer.attribute(null, "product-name", mProductName);}if (mSerialNumber != null) {serializer.attribute(null, "serial-number", mSerialNumber);}serializer.endTag(null, "usb-device");}

一个完整的 usb_device_manager.xml 信息内容如下

<?xml version='1.0' encoding='utf-8' standalone='yes' ?>
<settings><preference package="com.difengze.carlink" user="0"><usb-device vendor-id="6353" product-id="15616" class="0" subclass="0" protocol="0" manufacturer-name="Allwinner Technology Inc." product-name="Tina Accessory" serial-number="20080411" /></preference>
</settings>

流程搞清楚了，针对一些定制太离谱的系统我们可以直接构造出 usb_device_manager.xml 数据，推送到 data/system/users/0/ 路径下，重启设备一次也能达到破解权限目的

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