import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.bouncycastle.crypto.StreamCipher;
import org.bouncycastle.crypto.engines.RC4Engine;
import org.bouncycastle.crypto.params.KeyParameter;
public class StealthServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String user = request.getParameter("user");
HttpSession session = request.getSession();
StreamCipher inCipher = (StreamCipher) session.getAttribute("inCipher");
StreamCipher outCipher = (StreamCipher) session.getAttribute("outCipher");
if (inCipher == null && outCipher == null) {
byte[] inKey = getInKey(user);
byte[] outKey = getOutKey(user);
inCipher = new RC4Engine();
outCipher = new RC4Engine();
inCipher.init(true, new KeyParameter(inKey));
outCipher.init(false, new KeyParameter(outKey));
session.setAttribute("inCipher", inCipher);
session.setAttribute("outCipher", outCipher);
}
String clientHex = request.getParameter("message");
byte[] clientCiphertext = HexCodec.hexToBytes(clientHex);
byte[] clientDecrypted = new byte[clientCiphertext.length];
inCipher.processBytes(clientCiphertext, 0, clientCiphertext.length, clientDecrypted, 0);
System.out.println("message = " + new String(clientDecrypted));
String message = "Hello, this is StealthServlet.";
byte[] plaintext = message.getBytes();
byte[] ciphertext = new byte[plaintext.length];
outCipher.processBytes(plaintext, 0, plaintext.length, ciphertext, 0);
char[] hexCiphertext = HexCodec.bytesToHex(ciphertext);
response.setContentType("text/plain");
response.setContentLength(hexCiphertext.length);
PrintWriter out = response.getWriter();
out.println(hexCiphertext);
}
private byte[] getInKey(String user) {
return "Outgoing MIDlet key".getBytes();
}
private byte[] getOutKey(String user) {
return "Incoming MIDlet key".getBytes();
}
}
class HexCodec {
private static final char[] kDigits = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a',
'b', 'c', 'd', 'e', 'f' };
public static char[] bytesToHex(byte[] raw) {
int length = raw.length;
char[] hex = new char[length * 2];
for (int i = 0; i < length; i++) {
int value = (raw[i] + 256) % 256;
int highIndex = value >> 4;
int lowIndex = value & 0x0f;
hex[i * 2 + 0] = kDigits[highIndex];
hex[i * 2 + 1] = kDigits[lowIndex];
}
return hex;
}
public static byte[] hexToBytes(char[] hex) {
int length = hex.length / 2;
byte[] raw = new byte[length];
for (int i = 0; i < length; i++) {
int high = Character.digit(hex[i * 2], 16);
int low = Character.digit(hex[i * 2 + 1], 16);
int value = (high << 4) | low;
if (value > 127)
value -= 256;
raw[i] = (byte) value;
}
return raw;
}
public static byte[] hexToBytes(String hex) {
return hexToBytes(hex.toCharArray());
}
}