前言
Android系统在MarshMallow之前，权限都是在安装的时候授予的，虽然在4.3时，Google就试图在源码里面引入AppOpsManager来达到动态控制权限的目的，但由于不太成熟，在Release版本中都是把这个功能给隐藏掉的。在6.0之后，Google为了简化安装流程且方便用户控制权限，正式引入了runtime-permission，允许用户在运行的时候动态控制权限。对于开发而言就是将targetSdkVersion设置为23，并且在相应的时机动态申请权限，在适配了Android6.0的App运行在Android 6.0+的手机上时，就会调用6.0相关的API，不过在低版本的手机上，仍然是按安装时权限处理。
AppOpsManager动态权限管理：官方预演的权限管理
AppOpsManager是Google在Android4.3引入的动态权限管理方式，不过，Google觉得不成熟，所以在每个发行版的时候，总是会将这个功能给屏蔽掉。该功能跟国内的权限动态管理表现类似，这里用CyanogenMod12里面的实现讲述一下，（国内的ROM源码拿不到，不过从表现来看，实现应该类似）。AppOpsManager实现的动态管理的本质是：将鉴权放在每个服务内部，比如，如果App要申请定位权限，定位服务LocationManagerService会向AppOpsService查询是否授予了App定位权限，如果需要授权，就弹出一个系统对话框让用户操作，并根据用户的操作将结果持久化在文件中，如果在Setting里设置了响应的权限，也会去更新相应的权限操作持久化文件/data/system/appops.xml，下次再次申请服务的时候，服务会再次鉴定权限。
举个栗子-定位服务LocationManagerService: CM12源码
App在使用定位服务的时候，一般是通过LocationManager的requestLocationUpdates获取定位，其实是通过Binder请求LocationManagerService去定位。
/android/location/LocationManager.java
private void requestLocationUpdates(LocationRequest request, LocationListener listener, Looper looper, PendingIntent intent) { ... try { mService.requestLocationUpdates(request, transport, intent, packageName); .../com/android/server/LocationManagerService.java
@Override public void requestLocationUpdates(LocationRequest request, ILocationListener listener, PendingIntent intent, String packageName) { if (request == null) request = DEFAULT_LOCATION_REQUEST; checkPackageName(packageName); <!--关键函数 1 ，查询Manifest文件，是否进行了权限声明 --> int allowedResolutionLevel = getCallerAllowedResolutionLevel(); checkResolutionLevelIsSufficientForProviderUse(allowedResolutionLevel, request.getProvider()); 。。。 <!--获取调用app的pid跟uid--> final int pid = Binder.getCallingPid(); final int uid = Binder.getCallingUid(); // providers may use public location API's, need to clear identity long identity = Binder.clearCallingIdentity(); try { <!--关键函数 2 检查是否动态授权了权限，或者拒绝了权限--> checkLocationAccess(uid, packageName, allowedResolutionLevel); synchronized (mLock) { Receiver receiver = checkListenerOrIntentLocked(listener, intent, pid, uid, packageName, workSource, hideFromAppOps); if (receiver != null) { requestLocationUpdatesLocked(sanitizedRequest, receiver, pid, uid, packageName); } } } finally { Binder.restoreCallingIdentity(identity); } }
getCallerAllowedResolutionLevel主要通过调用getAllowedResolutionLevel查询APP是否在Manifest中进行了声明
private int getCallerAllowedResolutionLevel() {
return getAllowedResolutionLevel(Binder.getCallingPid(), Binder.getCallingUid());
}
private int getAllowedResolutionLevel(int pid, int uid) {
if (mContext.checkPermission(android.Manifest.permission.ACCESS_FINE_LOCATION,
pid, uid) == PackageManager.PERMISSION_GRANTED) {
return RESOLUTION_LEVEL_FINE;
} else if (mContext.checkPermission(android.Manifest.permission.ACCESS_COARSE_LOCATION,
pid, uid) == PackageManager.PERMISSION_GRANTED) {
return RESOLUTION_LEVEL_COARSE;
} else {
return RESOLUTION_LEVEL_NONE;
}
}
checkLocationAccess这里才是动态鉴权的入口，在checkLocationAccess函数中，会调用mAppOps.checkOp去鉴权，mAppOps就是AppOpsManager实例，
boolean checkLocationAccess(int uid, String packageName, int allowedResolutionLevel) {
int op = resolutionLevelToOp(allowedResolutionLevel);
if (op >= 0) {
int mode = mAppOps.checkOp(op, uid, packageName);
if (mode != AppOpsManager.MODE_ALLOWED && mode != AppOpsManager.MODE_ASK ) {
return false;
}
}
return true;
}
进而通过Binder向AppOpsService服务发送鉴权请求
public int noteOp(int op, int uid, String packageName) {
try {
int mode = mService.noteOperation(op, uid, packageName);
if (mode == MODE_ERRORED) {
throw new SecurityException(buildSecurityExceptionMsg(op, uid, packageName));
}
return mode;
} catch (RemoteException e) {
}
return MODE_IGNORED;
}
AppOpsService负责动态权限的鉴定跟更新，接着看noteOperation代码
@Override
public int noteOperation(int code, int uid, String packageName) {
final Result userDialogResult;
verifyIncomingUid(uid);
verifyIncomingOp(code);
synchronized (this) {
Ops ops = getOpsLocked(uid, packageName, true);
...
<!--关键点 1-->
if (switchOp.mode == AppOpsManager.MODE_IGNORED ||
switchOp.mode == AppOpsManager.MODE_ERRORED) {
op.rejectTime = System.currentTimeMillis();
op.ignoredCount++;
return switchOp.mode;
<!--关键点 2-->
} else if(switchOp.mode == AppOpsManager.MODE_ALLOWED) {
op.time = System.currentTimeMillis();
op.rejectTime = 0;
op.allowedCount++;
return AppOpsManager.MODE_ALLOWED;
} else {
op.noteOpCount++;
<!--关键函数 3-->
userDialogResult = askOperationLocked(code, uid, packageName,
switchOp);
}
}
return userDialogResult.get();
}
在上面的代码里面，1、2是对已经处理过的场景直接返回已授权，或者已经拒绝，而3就是我们常见授权入口对话框，这里是统一在AppOpsServie中进行授权处理的。askOperationLocked会显示一个系统对话框，用户选择授权或者拒绝后，AppOpsServie会将选择记录在案，并通知申请服务提供或者拒绝服务。askOperationLocked通过mHandler发送鉴权Message，看一下实现其实就是新建了一个PermissionDialog授权对话框，并且将AppOpsService的引用传了进去，授权后会通过mService.notifyOperation通知授权结果。
mHandler = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what) {
case SHOW_PERMISSION_DIALOG: {
HashMap<String, Object> data =
(HashMap<String, Object>) msg.obj;
synchronized (this) {
Op op = (Op) data.get("op");
Result res = (Result) data.get("result");
op.dialogResult.register(res);
if(op.dialogResult.mDialog == null) {
Integer code = (Integer) data.get("code");
Integer uid = (Integer) data.get("uid");
String packageName =
(String) data.get("packageName");
Dialog d = new PermissionDialog(mContext,
AppOpsService.this, code, uid,
packageName);
op.dialogResult.mDialog = (PermissionDialog)d;
d.show();
}
}
}break;
}
}
};
Android发行版源码对于动态权限管理的支持（几乎为零）
在Android4.3到5.1之间，虽然App可以获得AppOpsManager的实例，但是真正动态操作权限的接口setMode却被隐藏，如下
/** @hide */
public void setMode(int code, int uid, String packageName, int mode) {
try {
mService.setMode(code, uid, packageName, mode);
} catch (RemoteException e) {
}
}
遍历源码也只有NotificationManagerService这个系统应用使用了setMode，也就是说发行版，只有通知是通过系统的通知管理进行动态管理的。
public void setNotificationsEnabledForPackage(String pkg, int uid, boolean enabled) {
checkCallerIsSystem();
Slog.v(TAG, (enabled?"en":"dis") + "abling notifications for " + pkg);
mAppOps.setMode(AppOpsManager.OP_POST_NOTIFICATION, uid, pkg,
enabled ? AppOpsManager.MODE_ALLOWED : AppOpsManager.MODE_IGNORED);
// Now, cancel any outstanding notifications that are part of a just-disabled app
if (ENABLE_BLOCKED_NOTIFICATIONS && !enabled) {
cancelAllNotificationsInt(pkg, 0, 0, true, UserHandle.getUserId(uid));
}
}
Android 6.0权限管理原理
Android6.0的runtime-permission机制让用户在任何时候都可以取消授权，因此，每次在申请系统服务的时候，都要动态查询是否获取了相应的权限，如果没有获取，就需要动态去申请，首先先看一下权限的查询：
Android6.0权限查询
support-v4兼容包里面提供了一个工具类PermissionChecker，可以用来检查权限获取情况。
PermissionChecker
public static int checkPermission(@NonNull Context context, @NonNull String permission,
int pid, int uid, String packageName) {
if (context.checkPermission(permission, pid, uid) == PackageManager.PERMISSION_DENIED) {
return PERMISSION_DENIED;
}
String op = AppOpsManagerCompat.permissionToOp(permission);
if (op == null) {
return PERMISSION_GRANTED;
}
if (packageName == null) {
String[] packageNames = context.getPackageManager().getPackagesForUid(uid);
if (packageNames == null || packageNames.length <= 0) {
return PERMISSION_DENIED;
}
packageName = packageNames[0];
}
if (AppOpsManagerCompat.noteProxyOp(context, op, packageName)
!= AppOpsManagerCompat.MODE_ALLOWED) {
return PERMISSION_DENIED_APP_OP;
}
return PERMISSION_GRANTED;
}这里我们只关心context.checkPermission，从上面对于4.3-5.1的APPOpsManager的分析，我们知道AppOpsManagerCompat本身的一些操作对于权限管理并没有实际意义，只是用来做一些标记，最多就是对于通知权限有些用，接下来看checkPermission：
ContextImple.java
/** @hide */ @Override public int checkPermission(String permission, int pid, int uid, IBinder callerToken) { if (permission == null) { throw new IllegalArgumentException("permission is null"); } try { return ActivityManagerNative.getDefault().checkPermissionWithToken( permission, pid, uid, callerToken); } catch (RemoteException e) { return PackageManager.PERMISSION_DENIED; } }
接着往下看
ActivityManagerNative.java
public int checkPermission(String permission, int pid, int uid)
throws RemoteException {
Parcel data = Parcel.obtain();
Parcel reply = Parcel.obtain();
data.writeInterfaceToken(IActivityManager.descriptor);
data.writeString(permission);
data.writeInt(pid);
data.writeInt(uid);
mRemote.transact(CHECK_PERMISSION_TRANSACTION, data, reply, 0);
reply.readException();
int res = reply.readInt();
data.recycle();
reply.recycle();
return res;
}
ActivityManagerService
public int checkPermission(String permission, int pid, int uid) { if (permission == null) { return PackageManager.PERMISSION_DENIED; } return checkComponentPermission(permission, pid, UserHandle.getAppId(uid), -1, true); }进而调用ActivityManager.checkComponentPermission，调用AppGlobals.getPackageManager().checkUidPermission(permission, uid);
ActivityManager.java
/** @hide */ public static int checkComponentPermission(String permission, int uid, int owningUid, boolean exported) { // Root, system server get to do everything. <!--root及System能获取所有权限--> if (uid == 0 || uid == Process.SYSTEM_UID) { return PackageManager.PERMISSION_GRANTED; } 。。。 <!--普通的权限查询--> try { return AppGlobals.getPackageManager() .checkUidPermission(permission, uid); } catch (RemoteException e) { // Should never happen, but if it does... deny! Slog.e(TAG, "PackageManager is dead?!?", e); } return PackageManager.PERMISSION_DENIED; }最终调用PackageManagerService.java去查看是否有权限，到这里，我们只需要知道权限的查询其实是通过PKMS来进行的。心里先有个底，权限的更新，持久化，恢复都是通过PKMS来进行的。
PKMS不同版本的权限查询
Android5.0的checkUidPermission
public int checkUidPermission(String permName, int uid) {
final boolean enforcedDefault = isPermissionEnforcedDefault(permName);
synchronized (mPackages) {
<!--PackageManagerService.Setting.mUserIds数组中，根据uid查找uid（也就是package）的权限列表-->
Object obj = mSettings.getUserIdLPr(UserHandle.getAppId(uid));
if (obj != null) {
GrantedPermissions gp = (GrantedPermissions)obj;
if (gp.grantedPermissions.contains(permName)) {
return PackageManager.PERMISSION_GRANTED;
}
} else {
<!--mSystemPermissions记录一些系统级的应用的 uid 对应的 permission->
HashSet<String> perms = mSystemPermissions.get(uid);
if (perms != null && perms.contains(permName)) {
return PackageManager.PERMISSION_GRANTED;
}
}
if (!isPermissionEnforcedLocked(permName, enforcedDefault)) {
return PackageManager.PERMISSION_GRANTED;
}
}
return PackageManager.PERMISSION_DENIED;
}
Android6.0+的checkUidPermission
@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;
}
// Special case: ACCESS_FINE_LOCATION permission includes ACCESS_COARSE_LOCATION
if (Manifest.permission.ACCESS_COARSE_LOCATION.equals(permName) && permissionsState
.hasPermission(Manifest.permission.ACCESS_FINE_LOCATION, userId)) {
return PackageManager.PERMISSION_GRANTED;
}
} else {
ArraySet<String> perms = mSystemPermissions.get(uid);
if (perms != null) {
if (perms.contains(permName)) {
return PackageManager.PERMISSION_GRANTED;
}
if (Manifest.permission.ACCESS_COARSE_LOCATION.equals(permName) && perms
.contains(Manifest.permission.ACCESS_FINE_LOCATION)) {
return PackageManager.PERMISSION_GRANTED;
}
}
}
}
return PackageManager.PERMISSION_DENIED;
}
可以看到Android6.0之后，对权限的操作是PermissionsState
PermissionsState.java (android-6.0frameworksbaseservicescorejavacomandroidserverpm)
public boolean hasPermission(String name, int userId) { enforceValidUserId(userId); if (mPermissions == null) { return false; } PermissionData permissionData = mPermissions.get(name); return permissionData != null && permissionData.isGranted(userId); }从上面的代码可以很清晰看出，6.0之后，除了声明了权限之外，还必须是授权了的。运行时权限跟install权限有所不同，对于install权限isGranted一直返回是True，这里先不必深究PermissionsState是怎么存进内存，先记住，后面会将讲。
Android6.0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-6.0frameworksbasecorejavaandroidapp)
@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-6.0frameworksbaseservicescorejavacomandroidserverpm)
@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); }<!--查询是否在Manifest声明过权限-->
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;
}
<!--动态添加更新内存Permison -->
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之前的 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。
参考文档
1、Android 安全機制概述 Permission
2、android permission权限与安全机制解析
3、android6.0权限管理原理
4、深入理解 PackageManagerService
5、Android 4.3 隐藏功能 App Ops 分析
6、Android 权限机制，你真的了解吗？
7、Android原生权限管理：AppOps
8、 Android 5.1 AppOps总结
9、CM12源码
android
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