VPN: add VpnBuilder as the public API of user space VPN. (6abf3987) · Commits · e / os / android_frameworks_base

core/java/android/net/VpnBuilder.java

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+413 −0

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		/*
		* Copyright (C) 2011 The Android Open Source Project
		*
		* Licensed under the Apache License, Version 2.0 (the "License");
		* you may not use this file except in compliance with the License.
		* You may obtain a copy of the License at
		*
		* http://www.apache.org/licenses/LICENSE-2.0
		*
		* Unless required by applicable law or agreed to in writing, software
		* distributed under the License is distributed on an "AS IS" BASIS,
		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		* See the License for the specific language governing permissions and
		* limitations under the License.
		*/

		package android.net;

		import android.app.Activity;
		import android.app.PendingIntent;
		import android.content.Context;
		import android.content.Intent;
		import android.os.ParcelFileDescriptor;
		import android.os.RemoteException;
		import android.os.ServiceManager;

		import com.android.internal.net.VpnConfig;

		import java.net.InetAddress;
		import java.net.Inet4Address;
		import java.net.Inet6Address;
		import java.net.DatagramSocket;
		import java.net.Socket;
		import java.util.ArrayList;

		/**
		* VpnBuilder is a framework which enables applications to build their
		* own VPN solutions. In general, it creates a virtual network interface,
		* configures addresses and routing rules, and returns a file descriptor
		* to the application. Each read from the descriptor retrieves an outgoing
		* packet which was routed to the interface. Each write to the descriptor
		* injects an incoming packet just like it was received from the interface.
		* The framework is running on Internet Protocol (IP), so packets are
		* always started with IP headers. The application then completes a VPN
		* connection by processing and exchanging packets with a remote server
		* over a secured tunnel.
		*
		* <p>Letting applications intercept packets raises huge security concerns.
		* Besides, a VPN application can easily break the network, and two of them
		* may conflict with each other. The framework takes several actions to
		* address these issues. Here are some key points:
		* <ul>
		* <li>User action is required to create a VPN connection.</li>
		* <li>There can be only one VPN connection running at the same time. The
		* existing interface is deactivated when a new one is created.</li>
		* <li>A system-managed notification is shown during the lifetime of a
		* VPN connection.</li>
		* <li>A system-managed dialog gives the information of the current VPN
		* connection. It also provides a button to disconnect.</li>
		* <li>The network is restored automatically when the file descriptor is
		* closed. It also covers the cases when a VPN application is crashed
		* or killed by the system.</li>
		* </ul>
		*
		* <p>There are two primary methods in this class: {@link #prepare} and
		* {@link #establish}. The former deals with the user action and stops
		* the existing VPN connection created by another application. The latter
		* creates a VPN interface using the parameters supplied to this builder.
		* An application must call {@link #prepare} to grant the right to create
		* an interface, and it can be revoked at any time by another application.
		* The application got revoked is notified by an {@link #ACTION_VPN_REVOKED}
		* broadcast. Here are the general steps to create a VPN connection:
		* <ol>
		* <li>When the user press the button to connect, call {@link #prepare}
		* and launch the intent if necessary.</li>
		* <li>Register a receiver for {@link #ACTION_VPN_REVOKED} broadcasts.
		* <li>Connect to the remote server and negotiate the network parameters
		* of the VPN connection.</li>
		* <li>Use those parameters to configure a VpnBuilder and create a VPN
		* interface by calling {@link #establish}.</li>
		* <li>Start processing packets between the returned file descriptor and
		* the VPN tunnel.</li>
		* <li>When an {@link #ACTION_VPN_REVOKED} broadcast is received, the
		* interface is already deactivated by the framework. Close the file
		* descriptor and shut down the VPN tunnel gracefully.
		* </ol>
		* Methods in this class can be used in activities and services. However,
		* the intent returned from {@link #prepare} must be launched from an
		* activity. The broadcast receiver can be registered at any time, but doing
		* it before calling {@link #establish} effectively avoids race conditions.
		*
		* <p class="note">Using this class requires
		* {@link android.Manifest.permission#VPN} permission.
		* @hide
		*/
		public class VpnBuilder {

		/**
		* Broadcast intent action indicating that the VPN application has been
		* revoked. This can be only received by the target application on the
		* receiver explicitly registered using {@link Context#registerReceiver}.
		*
		* <p>This is a protected intent that can only be sent by the system.
		*/
		public static final String ACTION_VPN_REVOKED = VpnConfig.ACTION_VPN_REVOKED;

		/**
		* Use IConnectivityManager instead since those methods are hidden and
		* not available in ConnectivityManager.
		*/
		private static IConnectivityManager getService() {
		return IConnectivityManager.Stub.asInterface(
		ServiceManager.getService(Context.CONNECTIVITY_SERVICE));
		}

		/**
		* Prepare to establish a VPN connection. This method returns {@code null}
		* if the VPN application is already prepared. Otherwise, it returns an
		* {@link Intent} to a system activity. The application should launch the
		* activity using {@link Activity#startActivityForResult} to get itself
		* prepared. The activity may pop up a dialog to require user action, and
		* the result will come back to the application through its
		* {@link Activity#onActivityResult}. The application becomes prepared if
		* the result is {@link Activity#RESULT_OK}, and it is granted to create a
		* VPN interface by calling {@link #establish}.
		*
		* <p>Only one application can be granted at the same time. The right
		* is revoked when another application is granted. The application
		* losing the right will be notified by an {@link #ACTION_VPN_REVOKED}
		* broadcast, and its VPN interface will be deactivated by the system.
		* The application should then notify the remote server and disconnect
		* gracefully. Unless the application becomes prepared again, subsequent
		* calls to {@link #establish} will return {@code null}.
		*
		* @see #establish
		* @see #ACTION_VPN_REVOKED
		*/
		public static Intent prepare(Context context) {
		try {
		if (getService().prepareVpn(context.getPackageName(), null)) {
		return null;
		}
		} catch (RemoteException e) {
		// ignore
		}
		return VpnConfig.getIntentForConfirmation();
		}

		private VpnConfig mConfig = new VpnConfig();
		private StringBuilder mAddresses = new StringBuilder();
		private StringBuilder mRoutes = new StringBuilder();

		/**
		* Set the name of this session. It will be displayed in system-managed
		* dialogs and notifications. This is recommended not required.
		*/
		public VpnBuilder setSession(String session) {
		mConfig.session = session;
		return this;
		}

		/**
		* Set the {@link PendingIntent} to an activity for users to configure
		* the VPN connection. If it is not set, the button to configure will
		* not be shown in system-managed dialogs.
		*/
		public VpnBuilder setConfigureIntent(PendingIntent intent) {
		mConfig.configureIntent = intent;
		return this;
		}

		/**
		* Set the maximum transmission unit (MTU) of the VPN interface. If it
		* is not set, the default value in the operating system will be used.
		*
		* @throws IllegalArgumentException if the value is not positive.
		*/
		public VpnBuilder setMtu(int mtu) {
		if (mtu <= 0) {
		throw new IllegalArgumentException("Bad mtu");
		}
		mConfig.mtu = mtu;
		return this;
		}

		/**
		* Private method to validate address and prefixLength.
		*/
		private static void check(InetAddress address, int prefixLength) {
		if (address.isLoopbackAddress()) {
		throw new IllegalArgumentException("Bad address");
		}
		if (address instanceof Inet4Address) {
		if (prefixLength < 0 \|\| prefixLength > 32) {
		throw new IllegalArgumentException("Bad prefixLength");
		}
		} else if (address instanceof Inet6Address) {
		if (prefixLength < 0 \|\| prefixLength > 128) {
		throw new IllegalArgumentException("Bad prefixLength");
		}
		} else {
		throw new IllegalArgumentException("Unsupported family");
		}
		}

		/**
		* Convenience method to add a network address to the VPN interface
		* using a numeric address string. See {@link InetAddress} for the
		* definitions of numeric address formats.
		*
		* @throws IllegalArgumentException if the address is invalid.
		* @see #addAddress(InetAddress, int)
		*/
		public VpnBuilder addAddress(String address, int prefixLength) {
		return addAddress(InetAddress.parseNumericAddress(address), prefixLength);
		}

		/**
		* Add a network address to the VPN interface. Both IPv4 and IPv6
		* addresses are supported. At least one address must be set before
		* calling {@link #establish}.
		*
		* @throws IllegalArgumentException if the address is invalid.
		*/
		public VpnBuilder addAddress(InetAddress address, int prefixLength) {
		check(address, prefixLength);

		if (address.isAnyLocalAddress()) {
		throw new IllegalArgumentException("Bad address");
		}

		mAddresses.append(String.format(" %s/%d", address.getHostAddress(), prefixLength));
		return this;
		}

		/**
		* Convenience method to add a network route to the VPN interface
		* using a numeric address string. See {@link InetAddress} for the
		* definitions of numeric address formats.
		*
		* @see #addRoute(InetAddress, int)
		* @throws IllegalArgumentException if the route is invalid.
		*/
		public VpnBuilder addRoute(String address, int prefixLength) {
		return addRoute(InetAddress.parseNumericAddress(address), prefixLength);
		}

		/**
		* Add a network route to the VPN interface. Both IPv4 and IPv6
		* routes are supported.
		*
		* @throws IllegalArgumentException if the route is invalid.
		*/
		public VpnBuilder addRoute(InetAddress address, int prefixLength) {
		check(address, prefixLength);

		int offset = prefixLength / 8;
		byte[] bytes = address.getAddress();
		if (offset < bytes.length) {
		if ((byte)(bytes[offset] << (prefixLength % 8)) != 0) {
		throw new IllegalArgumentException("Bad address");
		}
		while (++offset < bytes.length) {
		if (bytes[offset] != 0) {
		throw new IllegalArgumentException("Bad address");
		}
		}
		}

		mRoutes.append(String.format(" %s/%d", address.getHostAddress(), prefixLength));
		return this;
		}

		/**
		* Convenience method to add a DNS server to the VPN connection
		* using a numeric address string. See {@link InetAddress} for the
		* definitions of numeric address formats.
		*
		* @throws IllegalArgumentException if the address is invalid.
		* @see #addDnsServer(InetAddress)
		*/
		public VpnBuilder addDnsServer(String address) {
		return addDnsServer(InetAddress.parseNumericAddress(address));
		}

		/**
		* Add a DNS server to the VPN connection. Both IPv4 and IPv6
		* addresses are supported. If none is set, the DNS servers of
		* the default network will be used.
		*
		* @throws IllegalArgumentException if the address is invalid.
		*/
		public VpnBuilder addDnsServer(InetAddress address) {
		if (address.isLoopbackAddress() \|\| address.isAnyLocalAddress()) {
		throw new IllegalArgumentException("Bad address");
		}
		if (mConfig.dnsServers == null) {
		mConfig.dnsServers = new ArrayList<String>();
		}
		mConfig.dnsServers.add(address.getHostAddress());
		return this;
		}

		/**
		* Add a search domain to the DNS resolver.
		*/
		public VpnBuilder addSearchDomain(String domain) {
		if (mConfig.searchDomains == null) {
		mConfig.searchDomains = new ArrayList<String>();
		}
		mConfig.searchDomains.add(domain);
		return this;
		}

		/**
		* Create a VPN interface using the parameters supplied to this builder.
		* The interface works on IP packets, and a file descriptor is returned
		* for the application to access them. Each read retrieves an outgoing
		* packet which was routed to the interface. Each write injects an
		* incoming packet just like it was received from the interface. The file
		* descriptor is put into non-blocking mode by default to avoid blocking
		* Java threads. To use the file descriptor completely in native space,
		* see {@link ParcelFileDescriptor#detachFd()}. The application MUST
		* close the file descriptor when the VPN connection is terminated. The
		* VPN interface will be removed and the network will be restored by the
		* framework automatically.
		*
		* <p>To avoid conflicts, there can be only one active VPN interface at
		* the same time. Usually network parameters are never changed during the
		* lifetime of a VPN connection. It is also common for an application to
		* create a new file descriptor after closing the previous one. However,
		* it is rare but not impossible to have two interfaces while performing a
		* seamless handover. In this case, the old interface will be deactivated
		* when the new one is configured successfully. Both file descriptors are
		* valid but now outgoing packets will be routed to the new interface.
		* Therefore, after draining the old file descriptor, the application MUST
		* close it and start using the new file descriptor. If the new interface
		* cannot be created, the existing interface and its file descriptor remain
		* untouched.
		*
		* <p>An exception will be thrown if the interface cannot be created for
		* any reason. However, this method returns {@code null} if the application
		* is not prepared or is revoked by another application. This helps solve
		* possible race conditions while handling {@link #ACTION_VPN_REVOKED}
		* broadcasts.
		*
		* @return {@link ParcelFileDescriptor} of the VPN interface, or
		* {@code null} if the application is not prepared.
		* @throws IllegalArgumentException if a parameter is not accepted by the
		* operating system.
		* @throws IllegalStateException if a parameter cannot be applied by the
		* operating system.
		* @see #prepare
		*/
		public ParcelFileDescriptor establish() {
		mConfig.addresses = mAddresses.toString();
		mConfig.routes = mRoutes.toString();

		try {
		return getService().establishVpn(mConfig);
		} catch (RemoteException e) {
		throw new IllegalStateException(e);
		}
		}

		/**
		* Protect a socket from VPN connections. The socket will be bound to the
		* current default network interface, so its traffic will not be forwarded
		* through VPN. This method is useful if some connections need to be kept
		* outside of VPN. For example, a VPN tunnel should protect itself if its
		* destination is covered by VPN routes. Otherwise its outgoing packets
		* will be sent back to the VPN interface and cause an infinite loop.
		*
		* <p>The socket is NOT closed by this method.
		*
		* @return {@code true} on success.
		*/
		public static boolean protect(int socket) {
		ParcelFileDescriptor dup = null;
		try {
		dup = ParcelFileDescriptor.fromFd(socket);
		return getService().protectVpn(dup);
		} catch (Exception e) {
		return false;
		} finally {
		try {
		dup.close();
		} catch (Exception e) {
		// ignore
		}
		}
		}

		/**
		* Protect a {@link Socket} from VPN connections.
		*
		* @return {@code true} on success.
		* @see #protect(int)
		*/
		public static boolean protect(Socket socket) {
		return protect(socket.getFileDescriptor$().getInt$());
		}

		/**
		* Protect a {@link DatagramSocket} from VPN connections.
		*
		* @return {@code true} on success.
		* @see #protect(int)
		*/
		public static boolean protect(DatagramSocket socket) {
		return protect(socket.getFileDescriptor$().getInt$());
		}
		}