Encrypting and decrypting user's API key

.gitignore

@@ -1,3 +1,4 @@
 /bin/
 /samples/
 /PDFs/
+user.enc

src/efakturaplus/App.java

@@ -1,10 +1,37 @@
 package efakturaplus;
 
+import java.io.BufferedInputStream;
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileReader;
+import java.io.InputStreamReader;
+
 import efakturaplus.gui.Window;
+import efakturaplus.models.User;
 
 public class App {
 
 	public static void main(String[] args) {
+		try {	
+			File f = new File("user.enc");
+
+			if(f.exists()) {
+				FileInputStream fis = new FileInputStream(f);
+				BufferedReader br = new BufferedReader(new FileReader(f));
+				StringBuilder sb = new StringBuilder();
+				String line;
+				while((line = br.readLine()) == null) {
+					sb.append(line);
+				}
+
+				User.API_KEY = sb.toString();
+			}
+
+		}catch(Exception e){
+			System.out.println("Error reading a file!");
+		};
+
 		@SuppressWarnings("unused")
 		Window w = new Window();
 	}

src/efakturaplus/gui/KeyPanel.java

@@ -1,66 +1,226 @@
 package efakturaplus.gui;
 
-import java.awt.Color;
-import java.awt.Font;
-import java.awt.event.ActionEvent;
-import java.awt.event.ActionListener;
+import java.awt.*;
+import java.awt.event.*;
+import java.io.*;
+import java.security.AlgorithmParameters;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
+import java.security.Key;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.security.spec.InvalidKeySpecException;
+import java.security.spec.KeySpec;
+
+import javax.crypto.*;
+import javax.crypto.spec.*;
+
+import sun.misc.*;
+
+import java.util.Arrays;
+import java.util.Base64;
 
 import javax.swing.BorderFactory;
+import javax.swing.JComponent;
 import javax.swing.JLabel;
+import javax.swing.JOptionPane;
 import javax.swing.JPanel;
+import javax.swing.JPasswordField;
 import javax.swing.JTextField;
+import javax.swing.border.Border;
+import javax.swing.event.DocumentEvent;
+import javax.swing.event.DocumentListener;
 
+import ch.randelshofer.util.ArrayUtil;
 import efakturaplus.models.User;
 
 public class KeyPanel extends JPanel {
 
 	private static final long serialVersionUID = 1L;
+
+	private String password;
+	private byte[] iv;
+
+	JLabel keyLabel, passLabel, passLabel2;
+	JTextField keyInput;
+	JPasswordField passInput, passInput2;
 
 	private Window parent;
+
+	private boolean registeredUser;
 
 	public KeyPanel(Window parent, int width, int height) {
 		this.parent = parent;
 		this.setSize(width, height);
 		this.setLayout(null);
-
-		addLabel(width, height);
-		addTextField(width, height);
-	}
-
-	private void addLabel(int width, int height) {
-		JLabel label = new JLabel("Please enter your API key here:");
-		label.setFont(new Font("Arial", Font.PLAIN, 20));
-		label.setBounds(width/2-150, height/2-75, 350, 50);
-
-		label.setForeground(Color.black);
-
-		this.add(label);
+
+		addComponents(width, height);
 	}
 
-	private void addTextField(int width, int height) {
-		JTextField keyInput = new JTextField();
-		keyInput.setBounds(width/2-150, height/2-25, 300, 60);
-
-		keyInput.setBorder(BorderFactory.createLineBorder(Color.black, 3, true));
-
-		keyInput.setBorder(BorderFactory.createCompoundBorder(
-				keyInput.getBorder(),
-		        BorderFactory.createEmptyBorder(15, 15, 15, 15)));
-
-		keyInput.setFont(new Font("Arial", Font.PLAIN, 20));
-
-		keyInput.addActionListener(new ActionListener() {
-
+	private void addComponents(int width, int height) {
+
+		Font font = new Font("Arial", Font.PLAIN, 20);
+
+		passLabel = new JLabel("Please enter your password here:");
+		passLabel.setFont(font);
+		passLabel.setForeground(Color.black);
+
+		passInput = new JPasswordField();
+		addBorder(passInput, Color.black);
+		passInput.setFont(font);
+
+		passInput.addActionListener(new ActionListener() {
 			@Override
 			public void actionPerformed(ActionEvent e) {
-				User.API_KEY = keyInput.getText();
-				System.out.println(User.API_KEY);
-
-				parent.showMainPanel();
+				submitData();
 			}
 		});
-
-		this.add(keyInput);
+
+		File userData = new File("user.enc");
+
+		if(!userData.exists()) {
+			keyLabel = new JLabel("Please enter your API key here:");
+			keyLabel.setFont(font);
+			keyLabel.setForeground(Color.black);
+			keyLabel.setBounds(width/2-150, height/4-75, 350, 50);
+
+			keyInput = new JTextField();
+			keyInput.setBounds(width/2-150, height/4-25, 300, 60);
+			addBorder(keyInput, Color.black);
+			keyInput.setFont(font);
+
+			keyInput.addActionListener(new ActionListener() {
+
+				@Override
+				public void actionPerformed(ActionEvent e) {
+					submitData();
+				}
+			});
+
+			passLabel.setText("Please enter new password:");
+			passLabel.setBounds(width/2-150, height/2-75, 350, 50);
+			passInput.setBounds(width/2-150, height/2-25, 300, 60);
+
+			passLabel2 = new JLabel("Please enter your password again:");
+			passLabel2.setFont(font);
+			passLabel2.setForeground(Color.black);
+			passLabel2.setBounds(width/2-150, height*3/4-75, 350, 50);
+
+
+			passInput2 = new JPasswordField();
+			addBorder(passInput2, Color.black);
+			passInput2.setFont(font);
+			passInput2.setBounds(width/2-150, height*3/4-25, 300, 60);
+
+			passInput2.addActionListener(new ActionListener() {
+				@Override
+				public void actionPerformed(ActionEvent e) {
+					submitData();
+				}
+			});
+
+			this.add(keyLabel);
+			this.add(keyInput);
+			this.add(passLabel);
+			this.add(passInput);
+			this.add(passLabel2);
+			this.add(passInput2);
+		}else {
+			passLabel.setBounds(width/2-150, height/2-75, 350, 50);
+			passInput.setBounds(width/2-150, height/2-25, 300, 60);
+			this.add(passLabel);
+			this.add(passInput);
+		}
+	}
+
+	private void addBorder(JComponent comp, Color c) {
+		comp.setBorder(BorderFactory.createCompoundBorder(
+				BorderFactory.createLineBorder(c, 3, true),
+		        BorderFactory.createEmptyBorder(15, 15, 15, 15)));
+	}
+
+	private void submitData() {
+		File userData = new File("user.enc");
+
+		if(!userData.exists()) {
+			User.API_KEY = keyInput.getText();
+
+			try {
+				encryptData();
+			} catch (Exception e) {
+				e.printStackTrace();
+			}
+
+			addComponents(getWidth(), getHeight());
+		}
+		else {
+			try {
+				System.out.println("Decrypted: "+decryptData());
+			} catch (Exception e) {
+				e.printStackTrace();
+			}
+		}
+	}
+
+	private void encryptData() throws NoSuchAlgorithmException, InvalidKeySpecException {
+		SecureRandom random = new SecureRandom();
+		byte[] salt = new byte[8];
+		random.nextBytes(salt);
+
+		SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
+		KeySpec spec = new PBEKeySpec(passInput.getPassword(), salt, 65536, 256);
+		SecretKey tmp = factory.generateSecret(spec);
+		SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "AES");
+
+		try {
+			Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
+			cipher.init(Cipher.ENCRYPT_MODE, secret);
+			AlgorithmParameters params = cipher.getParameters();
+			byte[] iv = params.getParameterSpec(IvParameterSpec.class).getIV();
+			byte[] ciphertext = cipher.doFinal(keyInput.getText().getBytes());
+
+			System.out.println("IV length: "+iv.length);
+			System.out.println("Cipher text length: "+ciphertext.length);
+
+			FileOutputStream fos = new FileOutputStream("user.enc");
+
+			fos.write(iv);
+			fos.write(salt);
+			fos.write(ciphertext);
+		} catch (Exception e) {
+			e.printStackTrace();
+		}
+	}
+
+	private String decryptData() {
+		String content = "";
+
+	    try (FileInputStream fileIn = new FileInputStream("user.enc")) {
+	        byte[] fileIv = new byte[16];
+	        byte[] salt = new byte[8];
+	        byte[] data = new byte[16];
+
+	        fileIn.read(fileIv);
+	        fileIn.read(salt);
+	        fileIn.read(data);
+
+	        SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
+	        KeySpec spec = new PBEKeySpec(passInput.getPassword(), salt, 65536, 256);
+	        SecretKey tmp = factory.generateSecret(spec);
+	        SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "AES");
+
+	        System.out.println(fileIv.toString());
+
+	        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
+	        cipher.init(Cipher.DECRYPT_MODE, secret, new IvParameterSpec(fileIv));
+	        String plaintext = new String(cipher.doFinal(data));
+
+	        content = plaintext;
+
+	    }catch(Exception e) {
+	    	e.printStackTrace();
+	    }
+
+	    return content;
 	}
-
 }

src/efakturaplus/gui/Window.java

@@ -47,11 +47,7 @@ public Window(String title) {
 		this.add(keyPanel, "KEY_PANEL");
 		this.add(mainPanel, "MAIN_PANEL");
 
-		if(User.API_KEY == "") {
-			showKeyPanel();
-		}else {
-			showMainPanel();
-		}
+		showKeyPanel();
 
 		this.setVisible(true);
 	}