private static void saveKey(String fileName, Key key) {
try {
FileOutputStream fos = new FileOutputStream(new File(fileName));
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(key);
oos.flush();
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* Sends the specified file to the client. File must exist or client and server threads will hang
* indefinitely. Generates a session key to encrypt the file over transfer; session key is
* encrypted using the client's public (asymmetric) key.
*
* @param aFile The name or path of the file to send.
* @throws IOException Error reading from socket.
*/
private void sendFile(String aFile) throws IOException {
try {
// get client public key
ObjectInputStream clientPubIn = new ObjectInputStream(connectedSocket.getInputStream());
PublicKey clientPublicKey = (PublicKey) clientPubIn.readObject();
// generate key string and send to client using their public key encrypted with RSA
// (asymmetric)
String keyString = generateKeyString();
Cipher keyCipher = Cipher.getInstance("RSA");
keyCipher.init(Cipher.ENCRYPT_MODE, clientPublicKey);
SealedObject sealedKeyString = new SealedObject(keyString, keyCipher);
ObjectOutputStream testOut = new ObjectOutputStream(outToClient);
testOut.writeObject(sealedKeyString);
testOut.flush();
// generate key spec from keyString
SecretKeySpec keySpec = new SecretKeySpec(keyString.getBytes(), "DES");
// set up encryption
Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, keySpec);
CipherOutputStream cipherOut = new CipherOutputStream(outToClient, cipher);
// send file
byte[] fileBuffer = new byte[BUFFER_SIZE];
InputStream fileReader = new BufferedInputStream(new FileInputStream(aFile));
int bytesRead;
while ((bytesRead = fileReader.read(fileBuffer)) != EOF) {
cipherOut.write(fileBuffer, 0, bytesRead);
}
cipherOut.flush();
cipherOut.close();
disconnect();
} catch (NoSuchPaddingException nspe) {
System.out.println("No such padding.");
} catch (NoSuchAlgorithmException nsae) {
System.out.println("Invalid algorithm entered");
} catch (ClassNotFoundException cnfe) {
System.out.println("Class not found.");
} catch (InvalidKeyException ike) {
System.out.println("Invalid key used for file encryption.");
} catch (FileNotFoundException fnfe) {
System.out.println("Invalid file entered.");
return;
} catch (IllegalBlockSizeException ibse) {
System.out.println("Illegal block size used for encryption.");
}
}
public boolean connect(String username, String weakSecret, final String server, final int port) {
System.out.println("attempting to connect");
try {
sock = new Socket();
sock.connect(new InetSocketAddress(server, port));
output = new ObjectOutputStream(sock.getOutputStream());
input = new ObjectInputStream(sock.getInputStream());
output.writeObject(username);
// do DH exchange and agree on starting message index
try {
if (weakSecret != null) // group server connect
{
HashMap<String, SecretKey> secretKeys =
DHKeyExchange.generateSecretKeyWithWeakSecret(username, weakSecret, input, output);
if (secretKeys == null) throw new Exception("Unable to verify server");
encryptionKey = secretKeys.get("encryptionKey");
signingKey = secretKeys.get("signingKey");
} else // file server connect
{
PublicKey fileServerPublicKey = (PublicKey) input.readObject(); // read in public key
File savedKeys = new File("savedkeys.bin");
ArrayList<PublicKey> knownKeys = new ArrayList<PublicKey>();
if (savedKeys.exists()) {
ObjectInputStream in = new ObjectInputStream(new FileInputStream(savedKeys));
knownKeys = (ArrayList<PublicKey>) in.readObject();
}
if (!knownKeys.contains(fileServerPublicKey)) // prompt the user to verify the key
{
MessageDigest sha = MessageDigest.getInstance("SHA-1");
byte[] digest = sha.digest(fileServerPublicKey.getEncoded());
System.out.println("RSA key fingerprint is " + getFingerprint(digest));
System.out.println(
"Please verify this is correct by contacting the file server owner.");
System.out.println(
"Do you want to add this key to your list of saved servers? (yes/no)");
Scanner scanner = new Scanner(System.in);
String answer = scanner.nextLine();
if (answer.toLowerCase().equals("yes")) {
knownKeys.add(fileServerPublicKey);
savedKeys.delete();
savedKeys.createNewFile();
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(savedKeys));
out.writeObject(knownKeys);
out.flush();
out.close();
output.writeObject("yes");
} else {
output.writeObject("no");
System.out.println("Exiting");
System.exit(0);
}
} else // accpet the key without prompt
output.writeObject("yes");
generateRSAKeypair();
output.writeObject(publicKey);
HashMap<String, SecretKey> secretKeys =
DHKeyExchange.generateSecretKeySignedExchange(
input, output, privateKey, fileServerPublicKey);
if (secretKeys == null) throw new Exception("Unable to verify server");
encryptionKey = secretKeys.get("encryptionKey");
signingKey = secretKeys.get("signingKey");
}
encryptCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
decryptCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
MessageDigest sha = MessageDigest.getInstance("SHA-1");
byte[] key = sha.digest(encryptionKey.getEncoded());
key = Arrays.copyOf(key, 16); // use only first 128 bit
SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");
encryptCipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, new IvParameterSpec(ivBytes));
decryptCipher.init(Cipher.DECRYPT_MODE, secretKeySpec, new IvParameterSpec(ivBytes));
BigInteger R = new BigInteger(128, new SecureRandom());
output.writeObject(encryptCipher.doFinal(R.toByteArray()));
BigInteger start = new BigInteger(decryptCipher.doFinal((byte[]) input.readObject()));
if (start.compareTo(R) < 0) throw new Exception("Invalid message index from server");
else messageIndex = start.add(BigInteger.ONE);
} catch (Exception ex) {
System.out.println("Failed to connect: " + ex.getMessage());
// if anything fails, we are not connected
sock = null;
return false;
}
} catch (IOException ex) {
return false;
}
return true;
}
