Merge "Check system_server PID in NetworkStack calls" (ebc3a5ce) · Commits · e / os / android_packages_modules_NetworkStack

src/com/android/server/NetworkStackService.java

+3 −0

Original line number	Diff line number	Diff line
		@@ -189,6 +189,7 @@ public class NetworkStackService extends Service {
		@Override
		public void makeNetworkMonitor(Network network, String name, INetworkMonitorCallbacks cb)
		throws RemoteException {
		checkNetworkStackCallingPermission();
		updateSystemAidlVersion(cb.getInterfaceVersion());
		final SharedLog log = addValidationLogs(network, name);
		final NetworkMonitor nm = new NetworkMonitor(mContext, cb, network, log);
		@@ -197,6 +198,7 @@ public class NetworkStackService extends Service {

		@Override
		public void makeIpClient(String ifName, IIpClientCallbacks cb) throws RemoteException {
		checkNetworkStackCallingPermission();
		updateSystemAidlVersion(cb.getInterfaceVersion());
		final IpClient ipClient = new IpClient(mContext, ifName, cb, mObserverRegistry, this);

		@@ -222,6 +224,7 @@ public class NetworkStackService extends Service {
		@Override
		public void fetchIpMemoryStore(@NonNull final IIpMemoryStoreCallbacks cb)
		throws RemoteException {
		checkNetworkStackCallingPermission();
		updateSystemAidlVersion(cb.getInterfaceVersion());
		cb.onIpMemoryStoreFetched(mIpMemoryStoreService);
		}

src/com/android/server/util/PermissionUtil.java

+30 −4

Original line number	Diff line number	Diff line
		@@ -16,30 +16,56 @@

		package com.android.server.util;

		import static android.os.Binder.getCallingPid;
		import static android.os.Binder.getCallingUid;

		import android.os.Process;
		import android.os.UserHandle;

		import java.util.concurrent.atomic.AtomicInteger;

		/**
		* Utility class to check calling permissions on the network stack.
		*/
		public final class PermissionUtil {
		private static final AtomicInteger sSystemPid = new AtomicInteger(-1);

		/**
		* Check that the caller is allowed to communicate with the network stack.
		* @throws SecurityException The caller is not allowed to communicate with the network stack.
		*/
		public static void checkNetworkStackCallingPermission() {
		// TODO: check that the calling PID is the system server.
		final int caller = getCallingUid();
		if (caller != Process.SYSTEM_UID
		&& UserHandle.getAppId(caller) != Process.BLUETOOTH_UID
		&& UserHandle.getAppId(caller) != Process.PHONE_UID) {
		if (caller == Process.SYSTEM_UID) {
		checkConsistentSystemPid();
		return;
		}

		if (UserHandle.getAppId(caller) != Process.BLUETOOTH_UID) {
		throw new SecurityException("Invalid caller: " + caller);
		}
		}

		private static void checkConsistentSystemPid() {
		// Apart from the system server process, no process with a system UID should try to
		// communicate with the network stack. This is to ensure that the network stack does not
		// need to maintain behavior for clients it was not designed to work with.
		// Checking that all calls from a system UID originate from the same PID loosely enforces
		// this restriction as if another system process calls the network stack first, the system
		// server would lose access to the network stack and cause obvious failures. If the system
		// server calls the network stack first, other clients would lose access as expected.
		final int systemPid = getCallingPid();
		if (sSystemPid.compareAndSet(-1, systemPid)) {
		// sSystemPid was unset (-1): this was the first call
		return;
		}

		if (sSystemPid.get() != systemPid) {
		throw new SecurityException("Invalid PID for the system server, expected "
		+ sSystemPid.get() + " but was called from " + systemPid);
		}
		}

		/**
		* Check that the caller is allowed to dump the network stack, e.g. dumpsys.
		* @throws SecurityException The caller is not allowed to dump the network stack.