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  1. import java.io.IOException;
  2. import java.io.OutputStream;
  3. import java.io.UnsupportedEncodingException;
  4. import java.net.InetSocketAddress;
  5. import java.util.Random;
  6. import java.io.File;
  7. import java.io.FileInputStream;
  8. import java.io.FileReader;
  9. import java.io.BufferedReader;
  10. import java.io.InputStreamReader;
  11. import java.util.Map;
  12. import java.util.HashMap;
  13. import java.util.Arrays;
  14. import java.security.MessageDigest;
  15.  
  16. import com.sun.net.httpserver.HttpExchange;
  17. import com.sun.net.httpserver.HttpHandler;
  18. import com.sun.net.httpserver.HttpServer;
  19.  
  20. public class Challenge16 {
  21.  
  22.     static private String data = "";
  23.     static private String adminPasswordHash = "";
  24.  
  25.     public static void main(String[] args) throws Exception {
  26.         // hashing the password helps security
  27.         // this hash corresponds to one of the commonly used passwords in 2018
  28.         // just for testing purposes, please change when deploying in production!!!
  29.         adminPasswordHash = "0571749e2ac330a7455809c6b0e7af90";
  30.  
  31.         // read the challenge file and store it in the data
  32.         File file = new File("flag16.txt");
  33.         BufferedReader br = new BufferedReader(new FileReader(file));
  34.         String line = "";
  35.         while ((line = br.readLine()) != null) data += line + "<br>";
  36.         br.close();
  37.  
  38.         // run the HTTP server to listen for connections
  39.         int port = 7006;
  40.         HttpServer server = HttpServer.create(new InetSocketAddress(7006), 0);
  41.         server.createContext("/login/", new LoginHandler());
  42.         server.createContext("/", new IndexHandler());
  43.         server.setExecutor(null);
  44.         server.start();
  45.         System.out.println("Started the server on port " + port + "...");
  46.     }
  47.  
  48.     // this class takes care of the action when the user clicks on Login
  49.     static class LoginHandler implements HttpHandler {
  50.         @Override
  51.         public void handle(HttpExchange t) throws IOException {
  52.             String output = "";
  53.             Map<String, String> GETRequestParams = queryToMap(t.getRequestURI().getQuery());
  54.             if (GETRequestParams.containsKey("username") && GETRequestParams.containsKey("password")) {
  55.                 String username = GETRequestParams.get("username");
  56.                 String password = GETRequestParams.get("password");
  57.  
  58.                 if (username.equals("admin") && md5hash(password).equals(adminPasswordHash)) {
  59.                     output += data;
  60.                 }
  61.                 else {
  62.                     output += "Username/password are not correct! Good luck next time.";
  63.                 }
  64.             }
  65.             else {
  66.                 output += "GET parameters are wrong, don't mess with us ;)";
  67.             }
  68.  
  69.             generateResponse(t, output);
  70.         }
  71.     }
  72.  
  73.     // this class takes care of the action when the user navigates to this challenge
  74.     static class IndexHandler implements HttpHandler {
  75.         @Override
  76.         public void handle(HttpExchange t) throws IOException {
  77.             generateResponse(t, "Hash the cash, cash the hash");
  78.         }
  79.     }
  80.  
  81.     // a method for a generic response to the user
  82.     static void generateResponse(HttpExchange t, String output) throws IOException {
  83.         String line = "", response = "";
  84.         try {
  85.             File indexFile = new File("index.html").getCanonicalFile();
  86.             BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream(indexFile)));
  87.             while ((line = bufferedReader.readLine()) != null) {
  88.                 response += line;
  89.             }
  90.             response = response.replaceAll("CONTENT_PLACEMENT", output);
  91.             bufferedReader.close();
  92.         } catch (IOException e) {
  93.             e.printStackTrace();
  94.         }
  95.         t.getResponseHeaders().add("Content-Type", "text/html");
  96.         t.sendResponseHeaders(200, response.length());
  97.         OutputStream os = t.getResponseBody();
  98.         os.write(response.getBytes());
  99.         os.close();
  100.     }
  101.  
  102.     // calculates MD5 hash of the input String
  103.     static public String md5hash(String s) {
  104.         try {
  105.             byte[] bytesOfMessage = s.getBytes("UTF-8");
  106.             MessageDigest md = MessageDigest.getInstance("MD5");
  107.             StringBuffer sb = new StringBuffer();
  108.             for (byte b : md.digest(bytesOfMessage)) {
  109.                 sb.append(String.format("%02x", b & 0xff));
  110.             }
  111.             return sb.toString();
  112.         }
  113.         catch(Exception e) {
  114.             System.out.println(e.getMessage());
  115.         }
  116.         return null;
  117.     }
  118.  
  119.     static public Map<String, String> queryToMap(String query) {
  120.         Map<String, String> result = new HashMap<>();
  121.         for (String param : query.split("&")) {
  122.             String[] entry = param.split("=");
  123.             if (entry.length > 1) { // proceed only when there is a pair of parameters
  124.                 result.put(entry[0], entry[1]);
  125.             }
  126.         }
  127.         return result;
  128.     }
  129.  
  130. }
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin
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Standard input is empty
compilation info 
Main.java:20: error: class Challenge16 is public, should be declared in a file named Challenge16.java
public class Challenge16 {
       ^
1 error
stdout
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Standard output is empty
https://ideone.com/JRq6hA
language:
Java (HotSpot 12)
created:
3 years ago
visibility:
public

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