Implement Settings#checkAndNoteChangeNetworkStateOperation on CS

Connectivity is becoming a mainline module in S and
ConnectivityManager#enforceChangePermission is using
Settings#checkAndNoteChangeNetworkStateOperation for performing a
strict and comprehensive check of whether a calling package is
allowed to change the state of network. However, Mainline modules
are not allowed to use non-formal APIs, fortunately CS is the
only caller of this ConnectivityManager#enforceChangePermission.
Thus, implement the Settings API on ConnectivityService and remove
the ConnectivityManager#enforceChangePermission and
Settings#checkAndNoteChangeNetworkStateOperation.

Bug: 178565313
Test: atest FrameworksNetTests
Change-Id: I6f03398c1735b89470ad5bdbe3a036929daeb53c
Merged-In: I6f03398c1735b89470ad5bdbe3a036929daeb53c

framework/src/android/net/ConnectivityManager.java

@@ -2245,31 +2245,6 @@ public class ConnectivityManager {
         }
     }
 
-    /* TODO: These permissions checks don't belong in client-side code. Move them to
-     * services.jar, possibly in com.android.server.net. */
-
-    /** {@hide} */
-    public static final void enforceChangePermission(Context context,
-            String callingPkg, String callingAttributionTag) {
-        int uid = Binder.getCallingUid();
-        checkAndNoteChangeNetworkStateOperation(context, uid, callingPkg,
-                callingAttributionTag, true /* throwException */);
-    }
-
-    /**
-     * Check if the package is a allowed to change the network state. This also accounts that such
-     * an access happened.
-     *
-     * @return {@code true} iff the package is allowed to change the network state.
-     */
-    // TODO: Remove method and replace with direct call once R code is pushed to AOSP
-    private static boolean checkAndNoteChangeNetworkStateOperation(@NonNull Context context,
-            int uid, @NonNull String callingPackage, @Nullable String callingAttributionTag,
-            boolean throwException) {
-        return Settings.checkAndNoteChangeNetworkStateOperation(context, uid, callingPackage,
-                throwException);
-    }
-
     /**
      * Check if the package is a allowed to write settings. This also accounts that such an access
      * happened.

services/core/java/com/android/server/ConnectivityService.java

@@ -2190,8 +2190,45 @@ public class ConnectivityService extends IConnectivityManager.Stub
                 "ConnectivityService");
     }
 
+    /**
+     * 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. 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 succeeds because the application holds WRITE_SETTINGS, the operation
+     * of this app will be updated to the current time.
+     */
     private void enforceChangePermission(String callingPkg, String callingAttributionTag) {
-        ConnectivityManager.enforceChangePermission(mContext, callingPkg, callingAttributionTag);
+        if (mContext.checkCallingOrSelfPermission(android.Manifest.permission.CHANGE_NETWORK_STATE)
+                == PackageManager.PERMISSION_GRANTED) {
+            return;
+        }
+
+        if (callingPkg == null) {
+            throw new SecurityException("Calling package name is null.");
+        }
+
+        final AppOpsManager appOpsMgr = mContext.getSystemService(AppOpsManager.class);
+        final int uid = mDeps.getCallingUid();
+        final int mode = appOpsMgr.noteOpNoThrow(AppOpsManager.OPSTR_WRITE_SETTINGS, uid,
+                callingPkg, callingAttributionTag, null /* message */);
+
+        if (mode == AppOpsManager.MODE_ALLOWED) {
+            return;
+        }
+
+        if ((mode == AppOpsManager.MODE_DEFAULT) && (mContext.checkCallingOrSelfPermission(
+                android.Manifest.permission.WRITE_SETTINGS) == PackageManager.PERMISSION_GRANTED)) {
+            return;
+        }
+
+        throw new SecurityException(callingPkg + " was not granted either of these permissions:"
+                + android.Manifest.permission.CHANGE_NETWORK_STATE + ","
+                + android.Manifest.permission.WRITE_SETTINGS + ".");
     }
 
     private void enforceSettingsPermission() {