权限分类

• Normal permissions

  只需要在AndroidManifest.xml 中声明，如INTERNET，WAKE_LOCK等

• Signature permissions

  申请该权限的应用和定义该权限的应用有相同签名时，这个权限才会被授予，一些Signature permissions不能被三方应用使用

• Dangerous permissions

  需要申请运行时权限

• Special permissions
  如SYSTEM_ALERT_WINDOW需要应用发送Settings.ACTION_MANAGE_OVERLAY_PERMISSION　intent去提示用户是否开启该权限

权限列表可以参考官网：
https://developer.android.google.cn/guide/topics/permissions/overview?hl=en

代码中的权限列表：
frameworks/base/data/etc/platform.xml

权限类型定义protectionLevel：
frameworks/base/core/res/AndroidManifest.xml

运行时权限申请方法

AndroidMenifest.xml 中添加

 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

代码中添加：

        if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.WRITE_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {

            // Should we show an explanation?
            if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                    Manifest.permission.WRITE_EXTERNAL_STORAGE)) {

                // Show an expanation to the user *asynchronously* -- don't block
                // this thread waiting for the user's response! After the user
                // sees the explanation, try again to request the permission.

            } else {

                // No explanation needed, we can request the permission.

                ActivityCompat.requestPermissions(this,
                        new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                        MY_PERMISSIONS_REQUEST_READ_SDCARD);

                // MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
                // app-defined int constant. The callback method gets the
                // result of the request.
            }
        }

    @Override
    public void onRequestPermissionsResult(int requestCode,
                                           String permissions[], int[] grantResults) {
        switch (requestCode) {
            case MY_PERMISSIONS_REQUEST_READ_SDCARD: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
　　　　　　　　　　　　... ...
                } else {
                    ... ...
                }
                return;
            }
        }
    }

查看应用是否有运行时权限：

adb shell dumpsys package + 包名

Packages:
  Package [com.example.hellojni2] (11f567c):
    userId=10127
    pkg=Package{714cb29 com.example.hellojni2}
    ... ...

    requested permissions:
      android.permission.WRITE_SETTINGS
      android.permission.READ_EXTERNAL_STORAGE
      android.permission.WRITE_EXTERNAL_STORAGE
    User 0: ceDataInode=-4294761261 installed=true hidden=false suspended=false stopped=false notLaunched=false enabled=0 instant=false virtual=false
      runtime permissions:
        android.permission.READ_EXTERNAL_STORAGE: granted=true
        android.permission.WRITE_EXTERNAL_STORAGE: granted=true

查看应用进程是否有某个权限，比如进程mediacodec，pid: 564是否有sdcard_rw权限

A3A_10_4G:/ $ cd proc/564
A3A_10_4G:/proc/564 $ cat status

Name:   omx@1.0-service
State:  S (sleeping)
Tgid:   564
Ngid:   0
Pid:    564
PPid:   1
TracerPid:  0
Uid:    1046    1046    1046    1046
Gid:    1006    1006    1006    1006
FDSize: 256
Groups: 1000 1005 1013 1015 1023 1026 1028 1031 3001 3002 3003 3007 

id sdcard_rw

A3A_10_4G:/ $ id sdcard_rw                                                     
uid=1015(sdcard_rw) gid=1015(sdcard_rw) groups=1015(sdcard_rw), context=u:r:shell:s0

可以看到有1015权限,即SDCard读写错误

运行时权限申请流程

１. 显示权限申请Dialog

frameworks/support/compat/src/main/java/androidx/core/app/ActivityCompat.java

      public static void requestPermissions(final @NonNull Activity activity,
              final @NonNull String[] permissions, final @IntRange(from = 0) int requestCode) {
            ... ...
  
          if (Build.VERSION.SDK_INT >= 23) {
             
              activity.requestPermissions(permissions, requestCode);
          } 
            ... ...
      }

打开全透明GrantPermissionsActivity

      public final void requestPermissions(@NonNull String[] permissions, int requestCode) {
          ... ...
          //没有申请过权限弹出权限申请dialog
          Intent intent = getPackageManager().buildRequestPermissionsIntent(permissions);
          startActivityForResult(REQUEST_PERMISSIONS_WHO_PREFIX, intent, requestCode, null);
          mHasCurrentPermissionsRequest = true;
      }

GrantPermissionsActivity实现接口GrantPermissionsViewHandler.ResultListener，用户点击允许添加权限时，回调　onPermissionGrantResult

      @Override
      public void onPermissionGrantResult(String name, boolean granted, boolean doNotAskAgain) {

            ... ...  
          GroupState groupState = mRequestGrantPermissionGroups.get(name);
          if (groupState != null && groupState.mGroup != null) {
              if (granted) {
                  //如果允许将整个权限组权限设为STATE_ALLOWED
                  groupState.mGroup.grantRuntimePermissions(doNotAskAgain,
                          groupState.affectedPermissions);
                  groupState.mState = GroupState.STATE_ALLOWED;
              } else {
               ... ... 
      }

２. 最终调用到PMS的grantRuntimePermission更新权限

frameworks/base/services/core/java/com/android/server/pm/permission/PermissionManagerService.java

private void grantRuntimePermission(String permName, String packageName, boolean overridePolicy,
              int callingUid, final int userId, PermissionCallback callback) {
  
          mContext.enforceCallingOrSelfPermission(
                  android.Manifest.permission.GRANT_RUNTIME_PERMISSIONS,
                  "grantRuntimePermission");
  
          enforceCrossUserPermission(callingUid, userId,
                  true,  // requireFullPermission
                  true,  // checkShell
                  false, // requirePermissionWhenSameUser
                  "grantRuntimePermission");
  
          final PackageParser.Package pkg = mPackageManagerInt.getPackage(packageName);
          if (pkg == null || pkg.mExtras == null) {
              throw new IllegalArgumentException("Unknown package: " + packageName);
          }
          final BasePermission bp;
          synchronized(mLock) {
              bp = mSettings.getPermissionLocked(permName);
          }
　　　　　　　... ...
          //检查AndroidManifest.xml中是否有声明过权限，如果没有抛出SecurityException异常
          bp.enforceDeclaredUsedAndRuntimeOrDevelopment(pkg);
  
  
          final int uid = UserHandle.getUid(userId, pkg.applicationInfo.uid);
  
          final PackageSetting ps = (PackageSetting) pkg.mExtras;
          final PermissionsState permissionsState = ps.getPermissionsState();
  　　　　?。÷砸恍┒园姹竞腿ㄏ蘩嘈图觳?  　　　　　... ...
  
          final int result = permissionsState.grantRuntimePermission(bp, userId);
          switch (result) {
              case PermissionsState.PERMISSION_OPERATION_FAILURE: {
                  return;
              }
  
              case PermissionsState.PERMISSION_OPERATION_SUCCESS_GIDS_CHANGED: {
                  if (callback != null) {
                      callback.onGidsChanged(UserHandle.getAppId(pkg.applicationInfo.uid), userId);
                  }
              }
              break;
          }
  

              //存在runtime-permissions.xml中
          if (callback != null) {
              callback.onPermissionGranted(uid, userId);
          }
  　　　　　... ...
      }

３．权限信息存储

frameworks/base/services/core/java/com/android/server/pm/permission/PermissionsState.java

      private int grantPermission(BasePermission permission, int userId) {
          if (hasPermission(permission.getName(), 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);
          得到权限信息后，将权限和userid存在一个 SparseArray数据结构中，用于查看对应权限是否申请
          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 PermissionCallback mPermissionCallback = new PermissionCallback() {

        @Override
        public void onPermissionGranted(int uid, int userId) {
            mOnPermissionChangeListeners.onPermissionsChanged(uid);

            // 应用权限存储在data/system/user/0/runtime-permissions.xml 手机启动时由PackageManagerService读取
            synchronized (mPackages) {
                mSettings.writeRuntimePermissionsForUserLPr(userId, false);
            }
        }
        ... ...
    }