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  1. import java.io.IOException;
  2. import java.io.OutputStream;
  3. import java.net.InetSocketAddress;
  4. import java.util.Random;
  5. import java.io.File;
  6. import java.io.FileInputStream;
  7. import java.io.FileReader;
  8. import java.io.BufferedReader;
  9. import java.io.InputStreamReader;
  10. import java.util.Map;
  11. import java.util.HashMap;
  12.  
  13. import com.sun.net.httpserver.HttpExchange;
  14. import com.sun.net.httpserver.HttpHandler;
  15. import com.sun.net.httpserver.HttpServer;
  16.  
  17. public class Challenge15 {
  18.  
  19.     static private String data = "";
  20.     static private String adminPassword = "";
  21.  
  22.     public static void main(String[] args) throws Exception {
  23.         // create a secure admin!
  24.         // we will generate a random password
  25.         // so that nobody will be able to log in as admin
  26.         // even we do not know what the password is,
  27.         // how smart is that, huh?
  28.         adminPassword = generateSecurePassword();
  29.  
  30.         // read the challenge file and store it in the data
  31.         File file = new File("flag15.txt");
  32.         BufferedReader br = new BufferedReader(new FileReader(file));
  33.         String line = "";
  34.         while ((line = br.readLine()) != null) data += line + "<br>";
  35.         br.close();
  36.  
  37.         // run the HTTP server to listen for connections
  38.         int port = 7005;
  39.         HttpServer server = HttpServer.create(new InetSocketAddress(port), 0);
  40.         server.createContext("/login/", new LoginHandler());
  41.         server.createContext("/", new IndexHandler());
  42.         server.setExecutor(null);
  43.         server.start();
  44.         System.out.println("Started the server on port " + port + "...");
  45.     }
  46.  
  47.     // this class takes care of the action when the user clicks on Login
  48.     static class LoginHandler implements HttpHandler {
  49.         @Override
  50.         public void handle(HttpExchange t) throws IOException {
  51.             String output = "";
  52.             Map<String, String> GETRequestParams = queryToMap(t.getRequestURI().getQuery());
  53.             if (GETRequestParams.containsKey("username") && GETRequestParams.containsKey("password")) {
  54.                 String username = GETRequestParams.get("username");
  55.                 String password = GETRequestParams.get("password");
  56.  
  57.                 if (username.equals("admin") && password.equals(adminPassword)) {
  58.                     output += data;
  59.                 }
  60.                 else {
  61.                     output += "Username/password are not correct! Good luck next time.";
  62.                 }
  63.             }
  64.             else {
  65.                 output += "GET parameters are wrong, don't mess with us ;)";
  66.             }
  67.  
  68.             generateResponse(t, output);
  69.         }
  70.     }
  71.  
  72.     // this class takes care of the action when the user navigates to this challenge
  73.     static class IndexHandler implements HttpHandler {
  74.         @Override
  75.         public void handle(HttpExchange t) throws IOException {
  76.             generateResponse(t, "Dear admin, hopefully, you remember your password!");
  77.         }
  78.     }
  79.  
  80.     // a method for a generic response to the user
  81.     static void generateResponse(HttpExchange t, String output) throws IOException {
  82.         String line = "", response = "";
  83.         try {
  84.             File indexFile = new File("index.html").getCanonicalFile();
  85.             BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream(indexFile)));
  86.             while ((line = bufferedReader.readLine()) != null) {
  87.                 response += line;
  88.             }
  89.             response = response.replaceAll("CONTENT_PLACEMENT", output);
  90.             bufferedReader.close();
  91.         } catch (IOException e) {
  92.             e.printStackTrace();
  93.         }
  94.         t.getResponseHeaders().add("Content-Type", "text/html");
  95.         t.sendResponseHeaders(200, response.length());
  96.         OutputStream os = t.getResponseBody();
  97.         os.write(response.getBytes());
  98.         os.close();
  99.     }
  100.  
  101.     static public Map<String, String> queryToMap(String query) {
  102.         Map<String, String> result = new HashMap<>();
  103.         for (String param : query.split("&")) {
  104.             String[] entry = param.split("=");
  105.             if (entry.length > 1) { // proceed only when there is a pair of parameters
  106.                 result.put(entry[0], entry[1]);
  107.             }
  108.         }
  109.         return result;
  110.     }
  111.  
  112.     static private String generateSecurePassword() {
  113.         String password = "magicallysecure";  
  114.         Random rnd = new Random();
  115.  
  116.         // generate a random number between 0 and 20 and based on that, create a password
  117.         Integer random = rnd.nextInt(20);
  118.  
  119.         // let's do some math on that number
  120.         // btw, this code can be run on the website like https://w...content-available-to-author-only...e.com/online-java-compiler
  121.         // just don't forget to import java.util.Random; at the top of the code editor
  122.         random = random * 16578;
  123.         random = random ^ 654321;
  124.         for (int i = 0; i < password.length(); i++) {
  125.             random += (int)password.charAt(i); // convert every character from password to an integer according to ASCII table and add that number to random
  126.         }
  127.  
  128.         password = random.toString();
  129.  
  130.         return password;
  131.     }
  132.  
  133. }
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin
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Standard input is empty
compilation info 
Main.java:17: error: class Challenge15 is public, should be declared in a file named Challenge15.java
public class Challenge15 {
       ^
1 error
stdout
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Standard output is empty
https://ideone.com/rJaWIA
language:
Java (HotSpot 12)
created:
3 years ago
visibility:
public

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