Update permission check for offloadEngine registration

For an app to register itself as an offloadEngine, it must have either
of the following permissions: NETWORK_STACK,
PERMISSION_MAINLINE_NETWORK_STACK, NETWORK_SETTINGS,
REGISTER_NSD_OFFLOAD_ENGINE.

Bug: 294777050
Test: atest CtsNetTestCases FrameworksNetTests
Change-Id: I19fe9b996a02b1ae23116c02a1b8406d93b3ecf1
diff --git a/service-t/src/com/android/server/NsdService.java b/service-t/src/com/android/server/NsdService.java
index eb73ee5..415159d 100644
--- a/service-t/src/com/android/server/NsdService.java
+++ b/service-t/src/com/android/server/NsdService.java
@@ -17,15 +17,18 @@
 package com.android.server;
 
 import static android.Manifest.permission.NETWORK_SETTINGS;
+import static android.Manifest.permission.NETWORK_STACK;
 import static android.net.ConnectivityManager.NETID_UNSET;
 import static android.net.NetworkCapabilities.TRANSPORT_VPN;
 import static android.net.NetworkCapabilities.TRANSPORT_WIFI;
+import static android.net.NetworkStack.PERMISSION_MAINLINE_NETWORK_STACK;
 import static android.net.nsd.NsdManager.MDNS_DISCOVERY_MANAGER_EVENT;
 import static android.net.nsd.NsdManager.MDNS_SERVICE_EVENT;
 import static android.net.nsd.NsdManager.RESOLVE_SERVICE_SUCCEEDED;
 import static android.provider.DeviceConfig.NAMESPACE_TETHERING;
 
 import static com.android.modules.utils.build.SdkLevel.isAtLeastU;
+import static com.android.networkstack.apishim.ConstantsShim.REGISTER_NSD_OFFLOAD_ENGINE;
 import static com.android.server.connectivity.mdns.MdnsRecord.MAX_LABEL_LENGTH;
 import static com.android.server.connectivity.mdns.util.MdnsUtils.Clock;
 
@@ -75,6 +78,7 @@
 import com.android.internal.util.State;
 import com.android.internal.util.StateMachine;
 import com.android.metrics.NetworkNsdReportedMetrics;
+import com.android.modules.utils.build.SdkLevel;
 import com.android.net.module.util.CollectionUtils;
 import com.android.net.module.util.DeviceConfigUtils;
 import com.android.net.module.util.InetAddressUtils;
@@ -2040,9 +2044,7 @@
         public void registerOffloadEngine(String ifaceName, IOffloadEngine cb,
                 @OffloadEngine.OffloadCapability long offloadCapabilities,
                 @OffloadEngine.OffloadType long offloadTypes) {
-            // TODO: Relax the permission because NETWORK_SETTINGS is a signature permission, and
-            //  it may not be possible for all the callers of this API to have it.
-            PermissionUtils.enforceNetworkStackPermissionOr(mContext, NETWORK_SETTINGS);
+            checkOffloadEnginePermission(mContext);
             Objects.requireNonNull(ifaceName);
             Objects.requireNonNull(cb);
             mNsdStateMachine.sendMessage(
@@ -2053,13 +2055,31 @@
 
         @Override
         public void unregisterOffloadEngine(IOffloadEngine cb) {
-            // TODO: Relax the permission because NETWORK_SETTINGS is a signature permission, and
-            //  it may not be possible for all the callers of this API to have it.
-            PermissionUtils.enforceNetworkStackPermissionOr(mContext, NETWORK_SETTINGS);
+            checkOffloadEnginePermission(mContext);
             Objects.requireNonNull(cb);
             mNsdStateMachine.sendMessage(
                     mNsdStateMachine.obtainMessage(NsdManager.UNREGISTER_OFFLOAD_ENGINE, cb));
         }
+
+        private static void checkOffloadEnginePermission(Context context) {
+            if (!SdkLevel.isAtLeastT()) {
+                throw new SecurityException("API is not available in before API level 33");
+            }
+            // REGISTER_NSD_OFFLOAD_ENGINE was only added to the SDK in V, but may
+            // be back ported to older builds: accept it as long as it's signature-protected
+            if (PermissionUtils.checkAnyPermissionOf(context, REGISTER_NSD_OFFLOAD_ENGINE)
+                    && (SdkLevel.isAtLeastV() || PermissionUtils.isSystemSignaturePermission(
+                    context, REGISTER_NSD_OFFLOAD_ENGINE))) {
+                return;
+            }
+            if (PermissionUtils.checkAnyPermissionOf(context, NETWORK_STACK,
+                    PERMISSION_MAINLINE_NETWORK_STACK, NETWORK_SETTINGS)) {
+                return;
+            }
+            throw new SecurityException("Requires one of the following permissions: "
+                    + String.join(", ", List.of(REGISTER_NSD_OFFLOAD_ENGINE, NETWORK_STACK,
+                    PERMISSION_MAINLINE_NETWORK_STACK, NETWORK_SETTINGS)) + ".");
+        }
     }
 
     private void sendNsdStateChangeBroadcast(boolean isEnabled) {