Android 在Framework默认授予launcher runtime权限

Android版本： 8.1
问题描述： 要在launcher显示通话记录calllog 和未读短信等内容，涉及运行时权限，导致必须申请运行时权限，这样就会弹窗提示，客户的需求当然是不许弹窗咯，第一次开机就要默认授权。

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一，privapp-permissions-mediatek.xml无效了

记得以前做这种权限问题，都是直接在privapp-permissions权限白名单里加上对应权限，但是在当前项目不支持，找不到具体原因，猜测是签名不同导致的，然而具体原因，在此只能打问号了。总之权限白名单失效了。

二，context.checkSelfPermission() 的流程

在前面白名单里已经写了，但是checkSelfPermission的时候还是返回了deny,于是我开始追寻checkSelfPermission的检测过程了。

Context.java

    @PackageManager.PermissionResult
    public abstract int checkSelfPermission(@NonNull String permission);

checkSelfPermission是抽象方法，自然它的实际实现者就是ContextImpl了

ContextImpl.java

    @Override
    public int checkSelfPermission(String permission) {
        if (permission == null) {
            throw new IllegalArgumentException("permission is null");
        }

        return checkPermission(permission, Process.myPid(), Process.myUid());
    }

@Override
    public int checkPermission(String permission, int pid, int uid) {
        if (permission == null) {
            throw new IllegalArgumentException("permission is null");
        }
        final IActivityManager am = ActivityManager.getService();
        if (am == null) {
            // Well this is super awkward; we somehow don't have an active
            // ActivityManager instance. If we're testing a root or system
            // UID, then they totally have whatever permission this is.
            final int appId = UserHandle.getAppId(uid);
            if (appId == Process.ROOT_UID || appId == Process.SYSTEM_UID) {
                Slog.w(TAG, "Missing ActivityManager; assuming " + uid + " holds " + permission);
                return PackageManager.PERMISSION_GRANTED;
            }
        }
        try {
            return am.checkPermission(permission, pid, uid);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

这里是通过IActivityManager接口来处理，当然实现IActivityManager接口的才是实体类，ActivityManagerService extends IActivityManager.Stub

在ActivityManagerService 里 checkPermission

    @Override
    public int checkPermission(String permission, int pid, int uid) {
        if (permission == null) {
            return PackageManager.PERMISSION_DENIED;
        }
        return checkComponentPermission(permission, pid, uid, -1, true);
    }

    int checkComponentPermission(String permission, int pid, int uid,
            int owningUid, boolean exported) {
        if (pid == MY_PID) {
            return PackageManager.PERMISSION_GRANTED;
        }
        return ActivityManager.checkComponentPermission(permission, uid,
                owningUid, exported);
    }

接着进入了ActivityManager里

/** @hide */
    public static int checkComponentPermission(String permission, int uid,
            int owningUid, boolean exported) {
        // Root, system server get to do everything.
        final int appId = UserHandle.getAppId(uid);
        if (appId == Process.ROOT_UID || appId == Process.SYSTEM_UID) {
            return PackageManager.PERMISSION_GRANTED;
        }
        // Isolated processes don't get any permissions.
        if (UserHandle.isIsolated(uid)) {
            return PackageManager.PERMISSION_DENIED;
        }
        // If there is a uid that owns whatever is being accessed, it has
        // blanket access to it regardless of the permissions it requires.
        if (owningUid >= 0 && UserHandle.isSameApp(uid, owningUid)) {
            return PackageManager.PERMISSION_GRANTED;
        }
        // If the target is not exported, then nobody else can get to it.
        if (!exported) {
            /*
            RuntimeException here = new RuntimeException("here");
            here.fillInStackTrace();
            Slog.w(TAG, "Permission denied: checkComponentPermission() owningUid=" + owningUid,
                    here);
            */
            return PackageManager.PERMISSION_DENIED;
        }
        if (permission == null) {
            return PackageManager.PERMISSION_GRANTED;
        }
        try {
            return AppGlobals.getPackageManager()
                    .checkUidPermission(permission, uid);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

前面都是判断特殊情况，比如

1. appId == Process.ROOT_UID 意思就是appId是属于root 用户就直接返回PERMISSION_GRANTED
2. exported == false,意思就是说比如这个组件 contentprovider, 或者activity 设置了exported false, 就直接返回PERMISSION_DENIED

而其余普通情况就是走进AppGlobals.getPackageManager() .checkUidPermission

这里获取到的是Packagemanager接口

    public static IPackageManager getPackageManager() {
        return ActivityThread.getPackageManager();
    }

实际对象是PackageManagerService

@Override
    public int checkUidPermission(String permName, int uid) {
        final int callingUid = Binder.getCallingUid();
        final int callingUserId = UserHandle.getUserId(callingUid);
        final boolean isCallerInstantApp = getInstantAppPackageName(callingUid) != null;
        final boolean isUidInstantApp = getInstantAppPackageName(uid) != null;
        final int userId = UserHandle.getUserId(uid);
        if (!sUserManager.exists(userId)) {
            return PackageManager.PERMISSION_DENIED;
        }
        /// M: CTA requirement - permission control  @{
        sCtaManager.reportPermRequestUsage(permName, uid);
        //@}
        synchronized (mPackages) {
            Object obj = mSettings.getUserIdLPr(UserHandle.getAppId(uid));
            if (obj != null) {
                if (obj instanceof SharedUserSetting) {
                    if (isCallerInstantApp) {
                        return PackageManager.PERMISSION_DENIED;
                    }
                } else if (obj instanceof PackageSetting) {
                    final PackageSetting ps = (PackageSetting) obj;
                    if (filterAppAccessLPr(ps, callingUid, callingUserId)) {
                        return PackageManager.PERMISSION_DENIED;
                    }
                }
                final SettingBase settingBase = (SettingBase) obj;
                final PermissionsState permissionsState = settingBase.getPermissionsState();
                if (permissionsState.hasPermission(permName, userId)) {
                    if (isUidInstantApp) {
                        BasePermission bp = mSettings.mPermissions.get(permName);
                        if (bp != null && bp.isInstant()) {
                            return PackageManager.PERMISSION_GRANTED;
                        }
                    } else {
                        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;
    }

这个方法很重要，结果就是在这里判断的，
根据打印可知，mSettings.getUserIdLPr 返回对应于launcher id的object不是空，于是obj != null
而检测结果显示
permissionsState.hasPermission(permName, userId) == false
这就说明 ，在launcher的PermissionsState里是不包含我们所要的运行权限的。

但是这个permissionsState是系统初始化的时候就对应好了的，也就是初始化的时候根本就没有这个授予权限。

三，从系统初始化找为什么没有自动授权

在系统初始化完成后PackageManagerService自然也要调用systemReady；

PackageManagerService–systemReady()

    @Override
    public void systemReady() {
		...
        // If we upgraded grant all default permissions before kicking off.
        for (int userId : grantPermissionsUserIds) {
            mDefaultPermissionPolicy.grantDefaultPermissions(userId);
        }
        ...
   }

这里有个默认授权的地方。

    public void grantDefaultPermissions(int userId) {
        if (mService.hasSystemFeature(PackageManager.FEATURE_EMBEDDED, 0)) {
            grantAllRuntimePermissions(userId);
        } else {
            grantPermissionsToSysComponentsAndPrivApps(userId);
            grantDefaultSystemHandlerPermissions(userId);
            grantDefaultPermissionExceptions(userId);
        }
    }

这里PackageManager.FEATURE_EMBEDDED是没有支持的，接着走下面三个方法，重点在第一个方法里。

grantPermissionsToSysComponentsAndPrivApps
看这方法名不就是授权给系统组件和特权app吗？ 但是为什么launcher明明是priv app里的，还是没有权限？

    private void grantPermissionsToSysComponentsAndPrivApps(int userId) {
        Log.i(TAG, "Granting permissions to platform components for user " + userId);

        synchronized (mService.mPackages) {
            for (PackageParser.Package pkg : mService.mPackages.values()) {
                if (!isSysComponentOrPersistentPlatformSignedPrivAppLPr(pkg)
                        || !doesPackageSupportRuntimePermissions(pkg)
                        || pkg.requestedPermissions.isEmpty()) {
                    continue;
                }
                grantRuntimePermissionsForPackageLocked(userId, pkg);
            }
        }
    }

遍历系统packages， 做了三个判断，只有通过判断才能走下去

1. isSysComponentOrPersistentPlatformSignedPrivAppLPr
2. doesPackageSupportRuntimePermissions
3. pkg.requestedPermissions.isEmpty()

这里第一个方法就是判断该组件是不是系统组件或者是Persistent的系统签名的app

private boolean isSysComponentOrPersistentPlatformSignedPrivAppLPr(PackageParser.Package pkg) {
        if (UserHandle.getAppId(pkg.applicationInfo.uid) < FIRST_APPLICATION_UID) {
            return true;
        }
        if (!pkg.isPrivilegedApp()) {
            return false;
        }
        PackageSetting sysPkg = mService.mSettings.getDisabledSystemPkgLPr(pkg.packageName);
        if (sysPkg != null && sysPkg.pkg != null) {
            if ((sysPkg.pkg.applicationInfo.flags & ApplicationInfo.FLAG_PERSISTENT) == 0) {
                return false;
            }
        } else if ((pkg.applicationInfo.flags & ApplicationInfo.FLAG_PERSISTENT) == 0) {
            return false;
        }
        return PackageManagerService.compareSignatures(mService.mPlatformPackage.mSignatures,
                pkg.mSignatures) == PackageManager.SIGNATURE_MATCH;
    }

对laucnher来说pkg.isPrivilegedApp()肯定是true ,但是这里的ApplicationInfo.FLAG_PERSISTENT，launcher是没有这个属性的，然后后面就是系统签名匹配，pkg.mSignatures，
也就是LOCAL_CERTIFICATE := platform ，launcher也是没有设置的。所以这里返回肯定是false。

然后第二项，检查package 的targetSdkVersion是不是大于22，也就是android 6.0

    private static boolean doesPackageSupportRuntimePermissions(PackageParser.Package pkg) {
        return pkg.applicationInfo.targetSdkVersion > Build.VERSION_CODES.LOLLIPOP_MR1;
    }

第三项，pkg.requestedPermissions.isEmpty()
权限列表是否为空，

根据条件判断，这里必然三项检查返回必须都是false才能走下去，也就是 必须是 系统签名且FLAG_PERSISTENT的app 且 targetsdk>22 且 permissions 不为空才会往下走，否则continue跳到下一个package

只有满足条件的app
才能走后面的grantRuntimePermissionsForPackageLocked

    private void grantRuntimePermissionsForPackageLocked(int userId, PackageParser.Package pkg) {
        Set<String> permissions = new ArraySet<>();
        for (String permission :  pkg.requestedPermissions) {
            BasePermission bp = mService.mSettings.mPermissions.get(permission);
            if (bp != null && bp.isRuntime()) {
                permissions.add(permission);
            }
        }
        if (!permissions.isEmpty()) {
            grantRuntimePermissionsLPw(pkg, permissions, true, userId);
        }
    }

    private void grantRuntimePermissionsLPw(PackageParser.Package pkg, Set<String> permissions,
            boolean systemFixed, int userId) {
        grantRuntimePermissionsLPw(pkg, permissions, systemFixed, false, userId);
    }

接下来所做的就是授权了

    private void grantRuntimePermissionsLPw(PackageParser.Package pkg, Set<String> permissions,
            boolean systemFixed, boolean isDefaultPhoneOrSms, int userId) {
		......
		mService.grantRuntimePermission(pkg.packageName, permission, userId);
		......
		省略

private void grantRuntimePermission(String packageName, String name, final int userId,
            boolean overridePolicy) {
        ......
		final int result = permissionsState.grantRuntimePermission(bp, userId);
		......
}

也就是前面提到的permissionsState里给与对应权限，

    public int grantRuntimePermission(BasePermission permission, int userId) {
        enforceValidUserId(userId);
        if (userId == UserHandle.USER_ALL) {
            return PERMISSION_OPERATION_FAILURE;
        }
        return grantPermission(permission, userId);
    }

流程就是这样，后面不看了，对于launcher的问题，是出在前面的判断里，
打印知道，在launcher包做判断检查是否系统组件的时候返回了false,这就导致系统初始化的时候并不会自动授权launcher的运行权限。
而关键的地方

(pkg.applicationInfo.flags & ApplicationInfo.FLAG_PERSISTENT) == 0

PackageManagerService.compareSignatures(mService.mPlatformPackage.mSignatures,
                pkg.mSignatures) == PackageManager.SIGNATURE_MATCH

这两项必须满足，所以要在 标签里添加

android:persistent="true"

以及在makefile里添加

LOCAL_CERTIFICATE := platform

只有这样才会满足前面的条件。

重新编译，launcher 再检查权限，就是返回已经授权通话相关权限了。解决了默认runtime授权。

int result = mcontext.checkSelfPermission("android.permission.READ_PHONE_STATE")
result = PackageManager.PERMISSION_GRANTED

其实对于开发来说，还有更粗暴的方式，就是直接在前面判断launcher包名返回true,不过这样实在太粗暴了

if (pkg.packageName.contains("launcher3")) {
            return true;
}

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总结：

由于运行权限的问题，导致好几个地方不能正确获取权限，而又不允许弹窗申请，所以必须默认授权，这就一定要走源码，通过走一下权限检查流程，加深了我对权限这一块的理解。以后再有这种问题，就直接上了。