Implement startsecure() and login() on client

src/main/java/dslab/client/MessageClient.java

@@ -13,6 +13,7 @@ import java.util.Base64;
 import java.util.logging.Logger;
 
 import dslab.ComponentFactory;
+import dslab.exception.FailedVerificationException;
 import dslab.util.Config;
 
 import javax.crypto.*;
@@ -40,7 +41,8 @@ public class MessageClient implements IMessageClient, Runnable {
     private PrintWriter dmapOut;
     private BufferedReader dmapIn;
 
-    private Cipher aesCipher;
+    private Cipher aesEncryptCipher;
+    private Cipher aesDecryptCipher;
     private byte[] challenge;
 
     /**
@@ -73,20 +75,36 @@ public class MessageClient implements IMessageClient, Runnable {
             this.dmapOut = new PrintWriter(this.dmapSocket.getOutputStream(), true);
 
             String input = null;
+            String message = null;
+
             if (!(input = this.dmapIn.readLine()).startsWith("ok DMAP2.0"))
                 shutdown();
 
+            startSecure();
+            loginUser();
+
             while (!Thread.currentThread().isInterrupted() && ((input = this.dmapIn.readLine()) != null)) {
-                // TODO initiate startsecure command
+                // TODO implement commands
-                // TODO login user (mailboxUser, mailboxPassword)
-                // startSecure()
             }
         } catch (IOException e) {
             logger.severe("Could not connect to MailboxHost " + this.mailboxHost + " on port " + this.mailboxPort);
             shutdown();
+        } catch (IllegalBlockSizeException | BadPaddingException e) {
+            logger.severe(e.getMessage());
+            shutdown();
         }
     }
 
+    private void loginUser() throws BadPaddingException, IllegalBlockSizeException, IOException {
+        String message;
+        logger.info("Trying to log in using " + this.mailboxUser + " " + this.mailboxPassword);
+        message = "login " + this.mailboxUser + " " + this.mailboxPassword;
+        this.dmapOut.println(getAesCiphertext(message));
+        String response = getAesPlaintext(this.dmapIn.readLine());
+        if (!response.startsWith("ok DMAP2.0"))
+            shutdown();
+    }
+
     private void startSecure() throws IOException {
         String input;
         String componentId;
@@ -108,18 +126,65 @@ public class MessageClient implements IMessageClient, Runnable {
                 serverPublicKey = kf.generatePublic(spec);
                 logger.info("Server's Public Key: " + serverPublicKey);
                 String clientChallenge = generateChallengeMessage(serverPublicKey);
-                // TODO send clientChallenge to server
+                // Send clientChallenge to server
-                // TODO Receive AES encrypted message saying "ok <client-challenge>"
+                this.dmapOut.println(clientChallenge);
-                // TODO Compare received client challenge with generated client challenge
+                // Receive AES encrypted message saying "ok <client-challenge>"
-                // TODO Answer with AES encrypted "ok" if matching and use AES cipher for subsequent communication
+                String response = this.dmapIn.readLine();
-                // TODO immediately terminate upon encountering an error (pull try-catch out of submethods)
+                // Compare received client challenge with generated client challenge
-            } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
+                verifyChallenge(response);
+                // Answer with AES encrypted "ok" if matching and use AES cipher for subsequent communication
+                this.dmapOut.println(getAesCiphertext("ok"));
+            } catch (NoSuchAlgorithmException | InvalidKeySpecException | IllegalBlockSizeException | BadPaddingException | FailedVerificationException e) {
                 logger.severe(e.getMessage());
                 shutdown();
             }
+        } else {
+            logger.severe("MailboxHost " + mailboxHost + " on port " + mailboxPort + " did not respond with 'ok' <component-id>");
+            shutdown();
         }
     }
 
+    /**
+     * Takes a plaintext message, encrypts and encodes it and returns the encoded ciphertext ready for sending.
+     * @param message Plaintext message
+     * @return B64 encoded and AES encrypted ciphertext
+     */
+    private String getAesCiphertext(String message) throws IllegalBlockSizeException, BadPaddingException {
+        byte[] cipherText = aesEncryptCipher.doFinal(message.getBytes(StandardCharsets.UTF_8));
+        return Base64.getEncoder().encodeToString(cipherText);
+    }
+
+    /**
+     * Takes an AES encrypted message, decrypts and decodes it and returns the plaintext.
+     * @param message B64 encoded and AES encrypted message
+     * @return B64 decoded and AES decrypted plaintext
+     */
+    private String getAesPlaintext(String message) throws BadPaddingException, IllegalBlockSizeException {
+        byte[] cipherText = Base64.getDecoder().decode(message.getBytes(StandardCharsets.UTF_8));
+        return new String(aesDecryptCipher.doFinal(cipherText));
+    }
+
+    private void verifyChallenge(String response) throws FailedVerificationException {
+        // Decrypt to base64 encoded byte array
+        String plainText;
+        try {
+            plainText = new String(aesDecryptCipher.doFinal(Base64.getDecoder().decode(response)));
+            logger.info("Decrypted AES challenge: " + plainText);
+        } catch (IllegalBlockSizeException | BadPaddingException e) {
+            logger.severe("Error during decryption of client challenge. Aborting...");
+            shutdown();
+            return;
+        }
+        // Decode <client-challenge>
+        if (plainText.split("\\s+").length != 2)
+            shutdown();
+        String clientChallenge = new String(Base64.getDecoder().decode(plainText.split("\\s+")[1]));
+        // Compare received challenge with sent
+
+        if (!clientChallenge.equals(new String(this.challenge)))
+            throw new FailedVerificationException("Server's clientChallenge " + clientChallenge + " does not match sent clientChallenge " + new String(this.challenge));
+    }
+
     private SecretKeySpec generateSecretKey() {
         try {
             KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
@@ -142,7 +207,8 @@ public class MessageClient implements IMessageClient, Runnable {
 
     private void setAesCipher(SecretKeySpec secretKey, IvParameterSpec iv) {
         try {
-            this.aesCipher = Cipher.getInstance("AES/CTR/NoPadding");
+            this.aesEncryptCipher = Cipher.getInstance("AES/CTR/NoPadding");
+            this.aesDecryptCipher = Cipher.getInstance("AES/CTR/NoPadding");
         } catch (NoSuchAlgorithmException | NoSuchPaddingException e) {
             logger.severe("This should not be happening!");
             e.printStackTrace();
@@ -150,7 +216,8 @@ public class MessageClient implements IMessageClient, Runnable {
         }
 
         try {
-            this.aesCipher.init(Cipher.ENCRYPT_MODE, secretKey, iv);
+            this.aesEncryptCipher.init(Cipher.ENCRYPT_MODE, secretKey, iv);
+            this.aesDecryptCipher.init(Cipher.DECRYPT_MODE, secretKey, iv);
         } catch (InvalidKeyException | InvalidAlgorithmParameterException e) {
             logger.severe("This should not be happening!");
             e.printStackTrace();

src/main/java/dslab/exception/FailedVerificationException.java

@@ -0,0 +1,7 @@
+package dslab.exception;
+
+public class FailedVerificationException extends Exception {
+    public FailedVerificationException(String errorMessage) {
+        super(errorMessage);
+    }
+}