Review

finding-14

/mubench/checkouts/chensun/cf23b99/build/CS5430/src/crypto/SharedKeyCryptoComm.java

receiveBytes(InputStream, Cipher, SecretKey, BigInteger)

class SharedKeyCryptoComm {
	/**
	 * RETURNS NULL IF CHECKSUM CHECK FAILS!!!
	 * @throws ConnectionException 
	 */
	public static byte[] receiveBytes(InputStream is, Cipher c, SecretKey sk, 
			BigInteger recvNonce) throws ConnectionException {
		int blockSize = c.getBlockSize();
		byte[] checksum = new byte[MD5CHECKSUMLEN]; //MD5
		byte[] recvnonce = new byte [NONCE_LENGTH];
		byte[] expctnonce = Arrays.copyOf(recvNonce.toByteArray(), NONCE_LENGTH);
		byte[] iv = new byte[blockSize];
		byte[] size = new byte[4]; //int

		//first fetch the checksum
		if (!readIntoBuffer(is, checksum)) {
			System.out.println("Error/Timeout receiving the message. (checksum)");
			System.out.println("Closing the connection...");
			throw new ConnectionException();
		}
		
		if (!readIntoBuffer(is, recvnonce)) {
			System.out.println("Error/Timeout receiving the message. (recvnonce)");
			System.out.println("Closing the connection...");
			throw new ConnectionException();
		}

		//fetch iv
		if (!readIntoBuffer(is, iv)) {
			System.out.println("Error/Timeout receiving the message. (iv)");
			System.out.println("Closing the connection...");
			throw new ConnectionException();
		}

		//fetch size of enc msg
		if (!readIntoBuffer(is, size)) {
			System.out.println("Error/Timeout receiving the message. (encmsglen)");
			System.out.println("Closing the connection...");
			throw new ConnectionException();
		}

		int encmsglen = ByteBuffer.wrap(size).getInt();

		byte[] encmsg = new byte[encmsglen];

		//read the actual message in
		if (!readIntoBuffer(is, encmsg)) {
			System.out.println("Error/Timeout receiving the message. (encmsg)");
			System.out.println("Closing the connection...");
			throw new ConnectionException();
		}
		
		IvParameterSpec ivp = new IvParameterSpec(iv);
		try {
			c.init(Cipher.DECRYPT_MODE, sk, ivp);
		}
		catch (Exception e) {/*cannot happen*/}

		byte[] msgbytes = null;
		try {
			msgbytes = c.doFinal(encmsg);
			//msg = new String(msgbytes, "UTF8");
		} catch (Exception e) {
			e.printStackTrace(); //this should not happen
		} 
		
		//generate checksum of received msg.
		byte[] wholeMessage = new byte[NONCE_LENGTH + iv.length + size.length + msgbytes.length];
		System.arraycopy(recvnonce, 0, wholeMessage, 0, NONCE_LENGTH);
		System.arraycopy(iv, 0, wholeMessage, NONCE_LENGTH, iv.length);
		System.arraycopy(size, 0, wholeMessage, NONCE_LENGTH + iv.length, size.length);
		System.arraycopy(msgbytes, 0, wholeMessage, NONCE_LENGTH + iv.length + size.length, msgbytes.length);
		
		//compare the checksum received to the generated checksum.
		if (Arrays.equals(checksum, Hash.generateChecksum(wholeMessage)) && 
				Arrays.equals(recvnonce, expctnonce)) {
			// zero out the wholeMessage array
			Arrays.fill(wholeMessage, (byte)0x00);
			return msgbytes;
		}
		if (!Arrays.equals(checksum, Hash.generateChecksum(wholeMessage))) {
				System.out.println("Generated checksum for message does not equal the received checksum!");
		}
		else {
			System.out.println("Received nonce for the message does not equal the expected nonce!");
		}
		System.out.println("Closing the connection...");
		throw new ConnectionException();
	}

}