安卓防火墙与VPN服务
2022-09-01 09:07:13
我正在尝试使用VpnService for BS项目为Android实现一个简单的防火墙。我选择VpnService，因为它将在无根设备上工作。它将记录连接并允许您过滤连接。（基于知识产权）
有一个应用程序可以执行此操作，因此可以。
我做了一些研究，发现VpnService创建了一个Tun接口。而已。（没有VPN实现，只有隧道）它允许您为此接口提供地址并添加路由。它返回一个文件描述符。您可以读取传出包和写入传入包。
我创建了一个 VpnService 派生类，并启动了服务。我可以使用 VpnService.Builder 类进行配置。当我查看与它的连接时，它会创建一个具有10.2.3.4 / 32地址的接口。它将所有软件包路由到此专用网络并发送到互联网。我正在尝试同样的事情。创建了一个地址为10.0.0.2/32的接口。添加了具有 addRoute 功能的路由。0.0.0.0/0，因此据我所知，我可以从所有网络捕获所有软件包。（我对这个主题很陌生，还在学习。我在互联网上找到了一些东西，所以我真的不确定。如果我错了，请纠正我。tun0mobiwol'sadb shell netcfgtun0
我在服务中创建了2个线程。一个从文件描述符读取，并使用受保护的套接字将其写入 127.0.0.1。（ 我不太确定我是否应该读/写到127.0.0.1。也许这就是问题所在。)
我分析了从文件描述符读取的数据包。例如：
01000101 byte:69 //ipv4 20byte header
00000000 byte:0 //TOS
00000000 byte:0 //Total Length
00111100 byte:60 //Total Length
11111100 byte:-4 //ID
11011011 byte:-37 //ID
01000000 byte:64 //fragment
00000000 byte:0 //"
01000000 byte:64 //TTL
00000110 byte:6 //Protocol 6 -> TCP
01011110 byte:94 //Header checksum
11001111 byte:-49 //Header checksum
00001010 byte:10 //10.0.0.2
00000000 byte:0
00000000 byte:0
00000010 byte:2
10101101 byte:-83 //173.194.39.78 //google
00111110 byte:-62
00100111 byte:39
******** byte:78
10110100 byte:-76 // IP option
01100101 byte:101
00000001 byte:1
10111011 byte:-69
//20byte IP haeder
01101101 byte:109
. . //40byte data (i couldnt parse TCP header,
I think its not needed when I route this in IP layer)
. .
. .
00000110 byte:6
我在其余数据中没有找到任何其他IP标头。我认为在10.0.0.2网络到本地网络（192.168.2.1）和互联网之间应该有一个封装。我不确定。
我真正的问题是我卡在传入的软件包线程上。我什么都看不懂。无响应。正如您在屏幕截图中看到的，没有传入的数据：
我正在尝试从用于写入127.0.0.1的相同连接读取受保护的套接字。
安卓 <-> Tun Interface （tun0） <-> 互联网连接
所有软件包<-> 10.0.0.2 <-> 127.0.0.1？<-> 192.168.2.1 <->互联网？
我找不到任何关于VpnService的有用信息。（ToyVPN的例子是无用的）我阅读了有关Linux Tun/Tap的文档，但它是关于主机和远程之间的隧道。我希望主机和遥控器在同一台设备上。不像隧道。
我该怎么做？
编辑：请求代码。它处于非常早期的阶段。正如我之前提到的，它是一个 VpnService 派生类。在服务线程中创建的 2 个线程（读取和写入）。
package com.git.firewall;
public class GITVpnService extends VpnService implements Handler.Callback, Runnable {
private static final String TAG = "GITVpnService";
private String mServerAddress = "127.0.0.1";
private int mServerPort = 55555;
private PendingIntent mConfigureIntent;
private Handler mHandler;
private Thread mThread;
private ParcelFileDescriptor mInterface;
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
// The handler is only used to show messages.
if (mHandler == null) {
mHandler = new Handler(this);
}
// Stop the previous session by interrupting the thread.
if (mThread != null) {
mThread.interrupt();
}
// Start a new session by creating a new thread.
mThread = new Thread(this, "VpnThread");
mThread.start();
return START_STICKY;
}
@Override
public void onDestroy() {
if (mThread != null) {
mThread.interrupt();
}
}
@Override
public boolean handleMessage(Message message) {
if (message != null) {
Toast.makeText(this, (String)message.obj, Toast.LENGTH_SHORT).show();
}
return true;
}
@Override
public synchronized void run() {
try {
Log.i(TAG, "Starting");
InetSocketAddress server = new InetSocketAddress(
mServerAddress, mServerPort);
run(server);
} catch (Exception e) {
Log.e(TAG, "Got " + e.toString());
try {
mInterface.close();
} catch (Exception e2) {
// ignore
}
Message msgObj = mHandler.obtainMessage();
msgObj.obj = "Disconnected";
mHandler.sendMessage(msgObj);
} finally {
}
}
DatagramChannel mTunnel = null;
private boolean run(InetSocketAddress server) throws Exception {
boolean connected = false;
android.os.Debug.waitForDebugger();
// Create a DatagramChannel as the VPN tunnel.
mTunnel = DatagramChannel.open();
// Protect the tunnel before connecting to avoid loopback.
if (!protect(mTunnel.socket())) {
throw new IllegalStateException("Cannot protect the tunnel");
}
// Connect to the server.
mTunnel.connect(server);
// For simplicity, we use the same thread for both reading and
// writing. Here we put the tunnel into non-blocking mode.
mTunnel.configureBlocking(false);
// Authenticate and configure the virtual network interface.
handshake();
// Now we are connected. Set the flag and show the message.
connected = true;
Message msgObj = mHandler.obtainMessage();
msgObj.obj = "Connected";
mHandler.sendMessage(msgObj);
new Thread ()
{
public void run ()
{
// Packets to be sent are queued in this input stream.
FileInputStream in = new FileInputStream(mInterface.getFileDescriptor());
// Allocate the buffer for a single packet.
ByteBuffer packet = ByteBuffer.allocate(32767);
int length;
try
{
while (true)
{
while ((length = in.read(packet.array())) > 0) {
// Write the outgoing packet to the tunnel.
packet.limit(length);
debugPacket(packet); // Packet size, Protocol, source, destination
mTunnel.write(packet);
packet.clear();
}
}
}
catch (IOException e)
{
e.printStackTrace();
}
}
}.start();
new Thread ()
{
public void run ()
{
DatagramChannel tunnel = mTunnel;
// Allocate the buffer for a single packet.
ByteBuffer packet = ByteBuffer.allocate(8096);
// Packets received need to be written to this output stream.
FileOutputStream out = new FileOutputStream(mInterface.getFileDescriptor());
while (true)
{
try
{
// Read the incoming packet from the tunnel.
int length;
while ((length = tunnel.read(packet)) > 0)
{
// Write the incoming packet to the output stream.
out.write(packet.array(), 0, length);
packet.clear();
}
}
catch (IOException ioe)
{
ioe.printStackTrace();
}
}
}
}.start();
return connected;
}
private void handshake() throws Exception {
if (mInterface == null)
{
Builder builder = new Builder();
builder.setMtu(1500);
builder.addAddress("10.0.0.2",32);
builder.addRoute("0.0.0.0", 0);
//builder.addRoute("192.168.2.0",24);
//builder.addDnsServer("8.8.8.8");
// Close the old interface since the parameters have been changed.
try {
mInterface.close();
} catch (Exception e) {
// ignore
}
// Create a new interface using the builder and save the parameters.
mInterface = builder.setSession("GIT VPN")
.setConfigureIntent(mConfigureIntent)
.establish();
}
}
private void debugPacket(ByteBuffer packet)
{
/*
for(int i = 0; i < length; ++i)
{
byte buffer = packet.get();
Log.d(TAG, "byte:"+buffer);
}*/
int buffer = packet.get();
int version;
int headerlength;
version = buffer >> 4;
headerlength = buffer & 0x0F;
headerlength *= 4;
Log.d(TAG, "IP Version:"+version);
Log.d(TAG, "Header Length:"+headerlength);
String status = "";
status += "Header Length:"+headerlength;
buffer = packet.get(); //DSCP + EN
buffer = packet.getChar(); //Total Length
Log.d(TAG, "Total Length:"+buffer);
buffer = packet.getChar(); //Identification
buffer = packet.getChar(); //Flags + Fragment Offset
buffer = packet.get(); //Time to Live
buffer = packet.get(); //Protocol
Log.d(TAG, "Protocol:"+buffer);
status += " Protocol:"+buffer;
buffer = packet.getChar(); //Header checksum
String sourceIP = "";
buffer = packet.get(); //Source IP 1st Octet
sourceIP += buffer;
sourceIP += ".";
buffer = packet.get(); //Source IP 2nd Octet
sourceIP += buffer;
sourceIP += ".";
buffer = packet.get(); //Source IP 3rd Octet
sourceIP += buffer;
sourceIP += ".";
buffer = packet.get(); //Source IP 4th Octet
sourceIP += buffer;
Log.d(TAG, "Source IP:"+sourceIP);
status += " Source IP:"+sourceIP;
String destIP = "";
buffer = packet.get(); //Destination IP 1st Octet
destIP += buffer;
destIP += ".";
buffer = packet.get(); //Destination IP 2nd Octet
destIP += buffer;
destIP += ".";
buffer = packet.get(); //Destination IP 3rd Octet
destIP += buffer;
destIP += ".";
buffer = packet.get(); //Destination IP 4th Octet
destIP += buffer;
Log.d(TAG, "Destination IP:"+destIP);
status += " Destination IP:"+destIP;
/*
msgObj = mHandler.obtainMessage();
msgObj.obj = status;
mHandler.sendMessage(msgObj);
*/
//Log.d(TAG, "version:"+packet.getInt());
//Log.d(TAG, "version:"+packet.getInt());
//Log.d(TAG, "version:"+packet.getInt());
}
}
