/**
* 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.");
}
}
