Reinstate CHANGE_NETWORK_STATE as a normal permission.

This is a partial revert of http://ag/738523 , but not a full
revert because M apps that have gone through the WRITE_SETTINGS
route to obtain permission to change network state should
continue to have permission to do so.

Specifically:

1. Change the protection level of CHANGE_NETWORK_STATE back from
   "signature|preinstalled|appop|pre23" to "normal". This allows
   apps that declare CHANGE_NETWORK_STATE in their manifest to
   acquire it, even if they target the M SDK or above.
2. Change the ConnectivityManager permission checks so that they
   first check CHANGE_NETWORK_STATE, and then ask Settings
   if the app has the WRITE_SETTINGS runtime permission.
3. Slightly simplify the code in the Settings provider code that
   deals specifically with the ability to change network state.
4. Make the ConnectivityService permissions checks use the
   ConnectivityManager code to avoid code duplication.
5. Update the ConnectivityManager public Javadoc to list both
   CHANGE_NETWORK_STATE and WRITE_SETTINGS.

Bug: 21588539
Bug: 23597341
Change-Id: Ic06a26517c95f9ad94183f6d126fd0de45de346e

1 files changed, 12 insertions, 40 deletions

diff --git a/core/java/android/provider/Settings.java b/core/java/android/provider/Settings.java
index 1822067..53897e0 100644
--- a/core/java/android/provider/Settings.java
+++ b/core/java/android/provider/Settings.java
@@ -1434,25 +1434,6 @@ public final class Settings {
     }
 
     /**
-     * An app can use this method to check if it is currently allowed to change the network
-     * state. In order to be allowed to do so, an app must first declare either the
-     * {@link android.Manifest.permission#CHANGE_NETWORK_STATE} or
-     * {@link android.Manifest.permission#WRITE_SETTINGS} permission in its manifest. If it
-     * is currently disallowed, it can prompt the user to grant it this capability through a
-     * management UI by sending an Intent with action
-     * {@link android.provider.Settings#ACTION_MANAGE_WRITE_SETTINGS}.
-     *
-     * @param context A context
-     * @return true if the calling app can change the state of network, false otherwise.
-     * @hide
-     */
-    public static boolean canChangeNetworkState(Context context) {
-        int uid = Binder.getCallingUid();
-        return Settings.isCallingPackageAllowedToChangeNetworkState(context, uid, Settings
-                .getPackageNameForUid(context, uid), false);
-    }
-
-    /**
      * System settings, containing miscellaneous system preferences.  This
      * table holds simple name/value pairs.  There are convenience
      * functions for accessing individual settings entries.
@@ -8343,7 +8324,7 @@ public final class Settings {
      * write/modify system settings, as the condition differs for pre-M, M+, and
      * privileged/preinstalled apps. If the provided uid does not match the
      * callingPackage, a negative result will be returned. The caller is expected to have
-     * either WRITE_SETTINGS or CHANGE_NETWORK_STATE permission declared.
+     * the WRITE_SETTINGS permission declared.
      *
      * Note: if the check is successful, the operation of this app will be updated to the
      * current time.
@@ -8359,31 +8340,22 @@ public final class Settings {
     /**
      * Performs a strict and comprehensive check of whether a calling package is allowed to
      * change the state of network, as the condition differs for pre-M, M+, and
-     * privileged/preinstalled apps. If the provided uid does not match the
-     * callingPackage, a negative result will be returned. The caller is expected to have
-     * either of CHANGE_NETWORK_STATE or WRITE_SETTINGS permission declared.
-     * @hide
-     */
-    public static boolean isCallingPackageAllowedToChangeNetworkState(Context context, int uid,
-            String callingPackage, boolean throwException) {
-        return isCallingPackageAllowedToPerformAppOpsProtectedOperation(context, uid,
-                callingPackage, throwException, AppOpsManager.OP_WRITE_SETTINGS,
-                PM_CHANGE_NETWORK_STATE, false);
-    }
-
-    /**
-     * Performs a strict and comprehensive check of whether a calling package is allowed to
-     * change the state of network, as the condition differs for pre-M, M+, and
-     * privileged/preinstalled apps. If the provided uid does not match the
-     * callingPackage, a negative result will be returned. The caller is expected to have
-     * either CHANGE_NETWORK_STATE or WRITE_SETTINGS permission declared.
+     * privileged/preinstalled apps. The caller is expected to have either the
+     * CHANGE_NETWORK_STATE or the WRITE_SETTINGS permission declared. Either of these
+     * permissions allow changing network state; WRITE_SETTINGS is a runtime permission and
+     * can be revoked, but (except in M, excluding M MRs), CHANGE_NETWORK_STATE is a normal
+     * permission and cannot be revoked. See http://b/23597341
      *
-     * Note: if the check is successful, the operation of this app will be updated to the
-     * current time.
+     * Note: if the check succeeds because the application holds WRITE_SETTINGS, the operation
+     * of this app will be updated to the current time.
      * @hide
      */
     public static boolean checkAndNoteChangeNetworkStateOperation(Context context, int uid,
             String callingPackage, boolean throwException) {
+        if (context.checkCallingOrSelfPermission(android.Manifest.permission.CHANGE_NETWORK_STATE)
+                == PackageManager.PERMISSION_GRANTED) {
+            return true;
+        }
         return isCallingPackageAllowedToPerformAppOpsProtectedOperation(context, uid,
                 callingPackage, throwException, AppOpsManager.OP_WRITE_SETTINGS,
                 PM_CHANGE_NETWORK_STATE, true);