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Android权限管理原理（4.3-6.0）下篇
猪小花1号2018-08-29 11:23Android6.0动态申请权限
申请权限可以通过V4包里面的ActivityCompat，它已经对不同版本做了兼容
ActivityCompat.java
public static void requestPermissions(final @NonNull Activity activity,
final @NonNull String[] permissions, final int requestCode) {
if (Build.VERSION.SDK_INT >= 23) {
ActivityCompatApi23.requestPermissions(activity, permissions, requestCode);
} else if (activity instanceof OnRequestPermissionsResultCallback) {
Handler handler = new Handler(Looper.getMainLooper());
handler.post(new Runnable() {
@Override
public void run() {
final int[] grantResults = new int[permissions.length];
PackageManager packageManager = activity.getPackageManager();
String packageName = activity.getPackageName();
final int permissionCount = permissions.length;
for (int i = 0; i < permissionCount; i++) {
grantResults[i] = packageManager.checkPermission(
permissions[i], packageName);
}
((OnRequestPermissionsResultCallback) activity).onRequestPermissionsResult(
requestCode, permissions, grantResults);
}
});
}
}
可以看到，如果是6.0以下，直接通过PKMS查询是否在Manifest里面申请了权限，并把查询结果通过onRequestPermissionsResult回调传给Activity或者Fragment。其实这里只要在Manifest中声明了，就会默认是Granted。接着往下看：ActivityCompatApi23最终会调用activity.requestPermissions去请求权限。
Activity
public final void requestPermissions(@NonNull String[] permissions, int requestCode) {
Intent intent = getPackageManager().buildRequestPermissionsIntent(permissions);
startActivityForResult(REQUEST_PERMISSIONS_WHO_PREFIX, intent, requestCode, null);
}
Intent其实是通过PackageManager（ApplicationPackageManager实现类）获取的Intent
public Intent buildRequestPermissionsIntent(@NonNull String[] permissions) {
if (ArrayUtils.isEmpty(permissions)) {
throw new NullPointerException("permission cannot be null or empty");
}
Intent intent = new Intent(ACTION_REQUEST_PERMISSIONS);
intent.putExtra(EXTRA_REQUEST_PERMISSIONS_NAMES, permissions);
intent.setPackage(getPermissionControllerPackageName());
return intent;
}
这里首先是隐式的获取授权Activity组件相关信息（GrantPermissionsActivity），其实就是对话框样式的授权Activity，它是PackageInstaller系统应用里面的一个Activity。这里的getPermissionControllerPackageName其实就是获取相应的包名，
ApplicationPackageManager.java (android-6.0\frameworks\base\core\java\android\app)
@Override
public String getPermissionControllerPackageName() {
synchronized (mLock) {
if (mPermissionsControllerPackageName == null) {
try {
mPermissionsControllerPackageName = mPM.getPermissionControllerPackageName();
} catch (RemoteException e) {
throw new RuntimeException("Package manager has died", e);
}
}
return mPermissionsControllerPackageName;
}
}
最终通过PackageManagerService获取包名
PackageManagerService.java (android-6.0\frameworks\base\services\core\java\com\android\server\pm)
@Override
public String getPermissionControllerPackageName() {
synchronized (mPackages) {
return mRequiredInstallerPackage;
}
}
mRequiredInstallerPackage这个变量具体赋值是在PMS的构造器中：对于原生Android 6.0，权限管理的APP跟安装器是同一个
mRequiredInstallerPackage = getRequiredInstallerLPr();
这里会得到PackageInstaller应用的相关信息，PackageInstaller负责应用的安装与卸载，里面还包含了对授权管理的一些逻辑。startActivityForResult启动的就是PackageInstaller中的GrantPermissionsActivity，该Activity主要负责权限的授予工作。
<activity android:name=".permission.ui.GrantPermissionsActivity"
android:configChanges="orientation|keyboardHidden|screenSize"
android:excludeFromRecents="true"
android:theme="@style/GrantPermissions">
<intent-filter>
<action android:name="android.content.pm.action.REQUEST_PERMISSIONS" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
这是一个类似于对话框的悬浮窗样式的Activity
<style name="GrantPermissions" parent="Settings">
<item name="android:windowIsFloating">true</item>
<item name="android:windowElevation">@dimen/action_dialog_z</item>
<item name="android:windowSwipeToDismiss">false</item>
</style>
之后就是动态更新权限流程：
如何动态更新RuntimePermission
通过上面的流程，我们进入了GrantPermissionsActivity，在这个Activity里面，如果一开始没有获得权限，就会弹出权限申请对话框，根据用户的操作去更新PKMS中的权限信息，同时将更新的结构持久化到runtime-permissions.xml中去。
GrantPermissionsActivity
GrantPermissionsActivity其实是利用GroupState对象与PKMS通信，远程更新权限的，当然，如果权限都已经授予了，那么就不需要再次弹出权限申请对话框。
public class GrantPermissionsActivity extends OverlayTouchActivity
implements GrantPermissionsViewHandler.ResultListener {
private LinkedHashMap<String, GroupState> mRequestGrantPermissionGroups = new LinkedHashMap<>();
....
@Override
public void onPermissionGrantResult(String name, boolean granted, boolean doNotAskAgain) {
GroupState groupState = mRequestGrantPermissionGroups.get(name);
if (groupState.mGroup != null) {
if (granted) {
<!--权限更新时机-->
groupState.mGroup.grantRuntimePermissions(doNotAskAgain);
groupState.mState = GroupState.STATE_ALLOWED;
} else {
groupState.mGroup.revokeRuntimePermissions(doNotAskAgain);
groupState.mState = GroupState.STATE_DENIED;
}
updateGrantResults(groupState.mGroup);
}
if (!showNextPermissionGroupGrantRequest()) {
setResultAndFinish();
}
}
具体更新流程：
public boolean grantRuntimePermissions(boolean fixedByTheUser, String[] filterPermissions) {
final int uid = mPackageInfo.applicationInfo.uid;
// We toggle permissions only to apps that support runtime
// permissions, otherwise we toggle the app op corresponding
// to the permission if the permission is granted to the app.
for (Permission permission : mPermissions.values()) {
if (filterPermissions != null
&& !ArrayUtils.contains(filterPermissions, permission.getName())) {
continue;
}
...
<!--一些关键点-->
// Grant the permission if needed.
if (!permission.isGranted()) {
permission.setGranted(true);
mPackageManager.grantRuntimePermission(mPackageInfo.packageName,
permission.getName(), mUserHandle);
}
// Update the permission flags.
if (!fixedByTheUser) {
// Now the apps can ask for the permission as the user
// no longer has it fixed in a denied state.
if (permission.isUserFixed() || permission.isUserSet()) {
permission.setUserFixed(false);
permission.setUserSet(true);
mPackageManager.updatePermissionFlags(permission.getName(),
mPackageInfo.packageName,
PackageManager.FLAG_PERMISSION_USER_FIXED
| PackageManager.FLAG_PERMISSION_USER_SET,
0, mUserHandle);
可以看到最终还是调用PackageManager去更新App的运行时权限,最终走进PackageManagerService服务，
PackageManagerService
@Override
public void grantRuntimePermission(String packageName, String name, final int userId) {
if (!sUserManager.exists(userId)) {
Log.e(TAG, "No such user:" + userId);
return;
}
...一些检查
mContext.enforceCallingOrSelfPermission(
android.Manifest.permission.GRANT_RUNTIME_PERMISSIONS,
"grantRuntimePermission");
enforceCrossUserPermission(Binder.getCallingUid(), userId,
true /* requireFullPermission */, true /* checkShell */,
"grantRuntimePermission");
。。。。。
...
uid = UserHandle.getUid(userId, pkg.applicationInfo.uid);
sb = (SettingBase) pkg.mExtras;
if (sb == null) {
throw new IllegalArgumentException("Unknown package: " + packageName);
}
final PermissionsState permissionsState = sb.getPermissionsState();
...
...授权
final int result = permissionsState.grantRuntimePermission(bp, userId);
switch (result) {
case PermissionsState.PERMISSION_OPERATION_FAILURE: {
return;
}
case PermissionsState.PERMISSION_OPERATION_SUCCESS_GIDS_CHANGED: {
final int appId = UserHandle.getAppId(pkg.applicationInfo.uid);
mHandler.post(new Runnable() {
@Override
public void run() {
killUid(appId, userId, KILL_APP_REASON_GIDS_CHANGED);
}
});
}
break;
}
mOnPermissionChangeListeners.onPermissionsChanged(uid);
<!--持久化-->
// Not critical if that is lost - app has to request again.
mSettings.writeRuntimePermissionsForUserLPr(userId, false);
}
private static void enforceDeclaredAsUsedAndRuntimeOrDevelopmentPermission(PackageParser.Package pkg,
BasePermission bp) {
int index = pkg.requestedPermissions.indexOf(bp.name);
if (index == -1) {
throw new SecurityException("Package " + pkg.packageName
+ " has not requested permission " + bp.name);
}
if (!bp.isRuntime() && !bp.isDevelopment()) {
throw new SecurityException("Permission " + bp.name
+ " is not a changeable permission type");
}
}
首先要更新内存中的权限授予情况
PermissionsState.java
private int grantPermission(BasePermission permission, int userId) {
if (hasPermission(permission.name, userId)) {
return PERMISSION_OPERATION_FAILURE;
}
final boolean hasGids = !ArrayUtils.isEmpty(permission.computeGids(userId));
final int[] oldGids = hasGids ? computeGids(userId) : NO_GIDS;
PermissionData permissionData = ensurePermissionData(permission);
if (!permissionData.grant(userId)) {
return PERMISSION_OPERATION_FAILURE;
}
if (hasGids) {
final int[] newGids = computeGids(userId);
if (oldGids.length != newGids.length) {
return PERMISSION_OPERATION_SUCCESS_GIDS_CHANGED;
}
}
return PERMISSION_OPERATION_SUCCESS;
}
private PermissionData ensurePermissionData(BasePermission permission) {
if (mPermissions == null) {
mPermissions = new ArrayMap<>();
}
PermissionData permissionData = mPermissions.get(permission.name);
if (permissionData == null) {
permissionData = new PermissionData(permission);
mPermissions.put(permission.name, permissionData);
}
return permissionData;
}
下一步，要将更新的权限持久化到文件中去 mSettings.writeRuntimePermissionsForUserLPr
RuntimePermission持久化
Settings.java
public void writeRuntimePermissionsForUserLPr(int userId, boolean sync) {
if (sync) {
mRuntimePermissionsPersistence.writePermissionsForUserSyncLPr(userId);
} else {
mRuntimePermissionsPersistence.writePermissionsForUserAsyncLPr(userId);
}
}
Settings.getPackageLPw这个方法，这是在安装应用扫描的时候scanPackageDirtyLI方法调用的，里面可以看到Settings类中的mUserIds、mPackages里面存的value还有PackageManagerService中的mPackages.pkg. mExtras都是同一个玩意奏是个PackageSetting。
private File getUserRuntimePermissionsFile(int userId) {
// TODO: Implement a cleaner solution when adding tests.
// This instead of Environment.getUserSystemDirectory(userId) to support testing.
File userDir = new File(new File(mSystemDir, "users"), Integer.toString(userId));
return new File(userDir, RUNTIME_PERMISSIONS_FILE_NAME);
}
在目录data/system/0/runtime-permissions.xml存放需要运行时申请的权限，Android6.0以上才有
<pkg name="com.snail.labaffinity">
<item name="android.permission.CALL_PHONE" granted="true" flags="0" />
<item name="android.permission.CAMERA" granted="false" flags="1" />
</pkg>
RuntimePermission恢复（其实这里也包含普通权限）
这些持久化的数据会在手机启动的时候由PMS读取,开机启动，PKMS扫描Apk，并更新package信息，检查/data/system/packages.xml是否存在，这个文件是在解析apk时由writeLP()创建的，里面记录了系统的permissions，以及每个apk的name,codePath,flags,ts,version,uesrid等信息，这些信息主要通过apk的AndroidManifest.xml解析获取，解析完apk后将更新信息写入这个文件并保存到flash，下次开机直接从里面读取相关信息添加到内存相关列表中，当有apk升级，安装或删除时会更新这个文件，packages.xml放的只包括installpermission，runtimepermissiono由runtime-permissions.xml存放。
public PackageManagerService(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
....
mSettings = new Settings(mPackages);
//汇总并更新和Permission相关的信息
updatePermissionsLPw(null, null, true,
regrantPermissions,regrantPermissions);
//将信息写到package.xml、package.list及package-stopped.xml文件中
mSettings.writeLPr();
....
mFirstBoot = !mSettings.readLPw(sUserManager.getUsers(false));
Settings(File dataDir, Object lock) {
mRuntimePermissionsPersistence = new RuntimePermissionPersistence(mLock);
<!--加载package信息-->
根据SettingsFile或者BackupSettingsFile读取相应的设置信息 生成PackageSetting对象，里面有权限列表字段protected final PermissionsState mPermissionsState;，之后再运行中，动态权限的操作都是针对这个对象
boolean readLPw(@NonNull List<UserInfo> users) {
FileInputStream str = null;
if (mBackupSettingsFilename.exists()) {
try {
str = new FileInputStream(mBackupSettingsFilename);
mReadMessages.append("Reading from backup settings file\n");
...
while ((type = parser.next()) != XmlPullParser.END_DOCUMENT
&& (type != XmlPullParser.END_TAG || parser.getDepth() > outerDepth)) {
String tagName = parser.getName();
if (tagName.equals("package")) {
!--读取package信息，包括install权限信息（对于Android6.0package.xml）-->
readPackageLPw(parser);
...
<!--读取runtime权限信息-->
for (UserInfo user : users) {
mRuntimePermissionsPersistence.readStateForUserSyncLPr(user.id);
}
}
private void readPackageLPw(XmlPullParser parser) throws XmlPullParserException, IOException {
String name = null;
...
(tagName.equals(TAG_PERMISSIONS)) {
readInstallPermissionsLPr(parser,
packageSetting.getPermissionsState());
之后就可以checkpermission了
@Override
public int checkUidPermission(String permName, int uid) {
final int userId = UserHandle.getUserId(uid);
if (!sUserManager.exists(userId)) {
return PackageManager.PERMISSION_DENIED;
}
synchronized (mPackages) {
Object obj = mSettings.getUserIdLPr(UserHandle.getAppId(uid));
if (obj != null) {
final SettingBase ps = (SettingBase) obj;
final PermissionsState permissionsState = ps.getPermissionsState();
if (permissionsState.hasPermission(permName, userId)) {
return PackageManager.PERMISSION_GRANTED;
}
原来的权限存放位置在哪？不会都从Android Manifest清单去读取，只会在启动时读取一次。Android6.0之前会吧所有的权限都放置在data/system/packages.xml文件中。Android6.0之后，分为运行时权限跟普通权限，普通权限还是放在data/system/packages.xml中，运行时权限防止在data/system/users/0/runtime-permissions.xml文件中。根据运行时是否动态申请去更新权限。
Android6.0申请普通权限会怎么样
Android6.0里，普通权限仍然按照运行时权限的模型，只是granted="true"，就是永远是取得授权的。所以可以直接获得权限申请成功的回调。如果查看packages.xml，就会发现：如下信息：
<perms>
<item name="android.permission.INTERNET" granted="true" flags="0" />
<item name="android.permission.ACCESS_WIFI_STATE" granted="true" flags="0" />
</perms>
Android的关键节点，在哪里？
关键节点并不是查询是否具有该权限，Android6.0之前，权限查询是不会触发权限申请与授权的，只有在请求系统服务的时候，由系统服务调用AppopsManager去查询是否赋予了该权限，第一次未操作肯定是null，未赋予就可能会触发权限申请逻辑，这个点在各个系统服务内部，由AppOpsService服务统一管理，不过对于官方的Release版本，其实只有系统通知APP才有动态权限管理的能力，其他都没有操作能力。Android6.0之后，便是显示的runtime-permission，将申请逻辑交给App分别申请，虽然仍有后端维护，但是，相对还是灵活些。
作者水平有限，文章有不准确、不完善的地方，希望大家包涵指正！
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