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package de.fhswf.in.inf.fit.aufgabe3;
import java.io.IOException;
import java.io.PrintWriter;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class LoginServlet
*/
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet
{
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public LoginServlet()
{
super();
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException
{
response.sendRedirect("LoginForm.jsp");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException
{
String validUsername = getServletContext().getInitParameter("username")
.toLowerCase();
String validPassword = getServletContext().getInitParameter("password");
String salt = getServletContext().getInitParameter("salt");
String requestUsername = request.getParameter("username").toLowerCase();
String requestPassword = request.getParameter("password");
if (requestUsername == null || requestPassword == null)
{
doGet(request, response);
}
PrintWriter pw = response.getWriter();
pw.println("<!DOCTYPE html>");
pw.println("<html>");
pw.println("<head>");
pw.println("<meta charset=\"utf-8\" />");
pw.println("<title>Login Answer</title>");
pw.println("</head>");
pw.println("<body>");
// This is very insecure and can be exploited via timing attacks
if (requestUsername.equals(validUsername)
&& createSaltedPasswordHash(validPassword, salt)
.equals(createSaltedPasswordHash(requestPassword, salt)))
{
pw.println("<h1>Success</h1>");
request.getSession().setAttribute("loggedin", true);
}
else
{
pw.println("<h1>Failed</h1>");
pw.println("<a href=\"LoginForm.jsp\">Retry</a>");
}
pw.println("</body>");
pw.println("</html>");
}
/**
* Generate a SHA-1 encoded password that is salted.
*
* @param password
* The password to encode.
* @param salt
* The salt for salting the password.
* @return The salted and encoded password hash.
*/
public static String createSaltedPasswordHash(String password, String salt)
{
if (password == null)
{
throw new IllegalArgumentException("Password can't be null");
}
if (salt == null)
{
throw new IllegalArgumentException("Salt can't be null");
}
try
{
MessageDigest md = MessageDigest.getInstance("SHA-1");
md.update((password + salt).getBytes());
return new String(md.digest());
}
catch (NoSuchAlgorithmException e)
{
throw new IllegalStateException(
"SHA-1 for some reason is not supported.", e);
}
}
}
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