Hi i would know an information, I must develop an Android application, I
need to sniff the packages that come from a certain connection.
I know that for this is it possible use tcpdump, but I can't use it because
I need root permission from my device, I can't give to my device these
permission. Exist some alternative that I can considered ?
I got to find out Vpn Service, but i don't understand if I can use it like
tcpdump, for example if I can pass the same parameter that I use in a
tcpdump command.
I need to obtain a .pcap or similar file with the result of the "sniffed"
packed.
someone can help me ?
Actually i have seen different post on internet but nothing help me.
import android.content.Intent;
import android.net.VpnService;
import android.os.Environment;
import android.os.ParcelFileDescriptor;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;
public class MyVpnService extends VpnService {
private Thread mThread;
private ParcelFileDescriptor mInterface;
FileInputStream in;
//a. Configure a builder for the interface.
Builder builder = new Builder();
// Services interface
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
// Start a new session by creating a new thread.
mThread = new Thread(new Runnable() {
@Override
public void run() {
try {
//a. Configure the TUN and get the interface.
mInterface = builder.setSession("MyVPNService")
.addAddress("216.58.210.195", 24)
.addDnsServer("8.8.8.8")
.addRoute("0.0.0.0", 0).establish();
//b. Packets to be sent are queued in this input stream.
in = new FileInputStream(mInterface.getFileDescriptor());
//b. Packets received need to be written to this output stream.
FileOutputStream out = new FileOutputStream(mInterface.getFileDescriptor());
//c. The UDP channel can be used to pass/get ip package to/from server
DatagramChannel tunnel = DatagramChannel.open();
// Connect to the remote server
tunnel.connect(new InetSocketAddress("127.0.0.1", 8087));
//d. Protect this socket, so package send by it will not be feedback to the
vpn service.
protect(tunnel.socket());
//e. Use a loop to pass packets.
ByteBuffer packet = ByteBuffer.allocate(32767);
// We use a timer to determine the status of the tunnel. It
// works on both sides. A positive value means sending, and
// any other means receiving. We start with receiving.
int timer = 0;
File sdCard = Environment.getExternalStorageDirectory();
File dir = new File (sdCard.getAbsolutePath() + "/MYDIR/");
dir.mkdirs();
File file = new File(dir, "report.txt");
// We keep forwarding packets till something goes wrong.
while (true) {
// Assume that we did not make any progress in this iteration.
boolean idle = true;
// Read the outgoing packet from the input stream.
int length = in.read(packet.array());
if (length > 0) {
// Write the outgoing packet to the tunnel.
packet.limit(length);
tunnel.write(packet);
packet.clear();
// There might be more outgoing packets.
idle = false;
// If we were receiving, switch to sending.
if (timer < 1) {
timer = 1;
}
}
// Read the incoming packet from the tunnel.
length = tunnel.read(packet);
if (length > 0) {
// Ignore control messages, which start with zero.
if (packet.get(0) != 0) {
// Write the incoming packet to the output stream.
out.write(packet.array(), 0, length);
// out = new FileOutputStream(file);
System.out.println("TEST"+out.toString());
}
packet.clear();
// There might be more incoming packets.
idle = false;
// If we were sending, switch to receiving.
if (timer > 0) {
timer = 0;
}
}
// If we are idle or waiting for the network, sleep for a
// fraction of time to avoid busy looping.
if (idle) {
Thread.sleep(100);
// Increase the timer. This is inaccurate but good enough,
// since everything is operated in non-blocking mode.
timer += (timer > 0) ? 100 : -100;
// We are receiving for a long time but not sending.
if (timer < -15000) {
// Send empty control messages.
packet.put((byte) 0).limit(1);
for (int i = 0; i < 3; ++i) {
packet.position(0);
tunnel.write(packet);
}
packet.clear();
// Switch to sending.
timer = 1;
}
// We are sending for a long time but not receiving.
if (timer > 20000) {
throw new IllegalStateException("Timed out");
}
}
}
} catch (Exception e) {
// Catch any exception
e.printStackTrace();
} finally {
try {
if (mInterface != null) {
mInterface.close();
mInterface = null;
}
} catch (Exception e) {
}
}
}
}, "MyVpnRunnable");
//start the service
mThread.start();
return START_STICKY;
}
@Override
public void onDestroy() {
// TODO Auto-generated method stub
if (mThread != null) {
mThread.interrupt();
}
super.onDestroy();
}
}
This is one example of code, i dont understand: 1) How to get packet with
VpnService and write a pcap file...
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