I'm building a chat client and server as part of a class project and running into one problem I can't seem to fix. Text has to be passed in the form of fixed size byte[] (either 32 or 64 bytes) depending on the particular case.
When I change the strings to byte[] with the .getBytes() method it pads out the length of the string with empty squares. This is fine during transit and receipt but at some point I need to change the string to it's original format (currently done with new String(byte[]) and delete the empty squares.
I can't seem to find a good way to do this. Any suggestions?
Relevant code bits client side:
byte[] bigDataByte = new byte[64];
sendData[2] = (bigDataByte = message.getBytes())
for (int i = 0; i < sendData.length; i++){
if (sendData[i] != null){
DatagramPacket sendPacket = new DatagramPacket(sendData[i], sendData[i].length, IPAddress, clientPort);
clientSocket.send(sendPacket);
}
}
Relevant code bits server side:
String name = new String(getBytes(32));
private static byte[] getBytes(int size) throws IOException {
byte[] dataByte = new byte[size];
DatagramPacket dataPacket = new DatagramPacket(dataByte, dataByte.length);
servSocket.receive(dataPacket);
return dataPacket.getData();
}
Not sure, but the issue might be that you are not specifying the charset.
Try using the
constructor: String(byte[] bytes, String charsetName)
and the method: getBytes(String charsetName).
e.g.
byte[] bytes = str.getBytes("UTF-8");
and
String str = new String(bytes, "UTF-8");
The default ones use the platform's default charset, which could lead to a mismatch.
Related
I am converting a piece of javascript code to java and want to encode a string to Base64 in java.
Code in javascript:
let encodedData = btoa(String.fromCharCode.apply(null, new Uint8Array(array)))
This converts Uint8Array to string first and then encode it to Base64. But I am not able to find a way to do same in java.
Java code is
InputStream insputStream = new FileInputStream(file);
long length = file.length();
byte[] bytes = new byte[(int) length];
insputStream.read(bytes);
insputStream.close();
byte[] encodedBytes = Base64.getEncoder().encode(bytes);
Which is encoding bytes. Dues to which, encodedData(js) and encodedBytes(java) are not same.
What I want to do is something like:
String str = new String(bytes);
byte[] encodedBytes = Base64.getEncoder().encode(str); // ERROR: encode doesn't accept string
Is there any way to achieve this?
Base64.getEncoder().encode(str.getBytes(Charset)) may help you
(as Thomas noticed). But i can't guess your charset. The right syntax for Charset will be something like StandartCharsets.SOME_CHARSET or Charset.forName("some_charset")
I developing TCP Server Program but I stucked this Server's Protocol
the header is fixed by 0xAA55, header size is 2 Byte
this is the problem I dont know fill in 0xAA55 to byte array
byte[] tmp = new byte[2];
tmp = 0xAA55;
this is not work..
You could wrap tmp with a ByteBuffer and then use ByteBuffer.putShort(short) like
byte[] tmp = new byte[2];
ByteBuffer bb = ByteBuffer.wrap(tmp);
bb.putShort((short) 0xAA55);
System.out.println(Arrays.toString(tmp));
As shown below I can read the byte[] sent from an IoSession without having a protocol decoder.
IoBuffer in = (IoBuffer) message;
byte[] inBytes = in.array();
int length = inBytes[0];
inBytes = Arrays.copyOfRange(inBytes, 1, length + 1);
ByteString incomingMessage = ByteString.copyFrom(inBytes);
But when I try to do:
someIoSession.write(incomingMessage.toByteArray());
I get the following error.
Don't know how to handle message of type XXXX. Are you missing a protocol encoder?
How can I just write the bytes into an IoSession?
someIoSession.write(IoBuffer.wrap(incomingMessage.toByteArray()));
So I have been working with the Bouncycastle libraries in an attempt to connect with a remote server. This process has been problematic from the get go and now I'm close to getting everything working but some odd things are happening.
When I first started building out the encryption process I was told to use AES 256 with PKCS7Padding. After some nagging I was provided with a c++ example of the server code. It turned out that the IV is 256 bit so I had to use the RijndaelEngine instead. Also in order for this to work correctly I have to use ZeroBytePadding.
Here is my code:
socket = new Socket(remoteIP, port);
outputStream = new PrintWriter(socket.getOutputStream());
inputStream = new BufferedReader(new InputStreamReader(socket.getInputStream()));
byte[] base_64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".getBytes("UTF-8");
Security.addProvider(new BouncyCastleProvider());
public String AESEncrypt(String out) throws IOException, DataLengthException, IllegalStateException, InvalidCipherTextException {
byte[] EncKey = key;
byte randKey;
Random randNumber = new Random();
randKey = base_64[randNumber.nextInt(base_64.length)];
EncKey[randKey&0x1f] = randKey;
RijndaelEngine rijndaelEngine = new RijndaelEngine(256);
PaddedBufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(rijndaelEngine), new ZeroBytePadding());
ParametersWithIV keyParameter = new ParametersWithIV(new KeyParameter(EncKey), iv);
cipher.init(true, keyParameter);
byte[] txt = out.getBytes();
byte[] encoded = new byte[cipher.getOutputSize(txt.length)];
int len = cipher.processBytes(txt, 0, txt.length, encoded, 0);
cipher.doFinal(encoded, len);
char keyChar = (char) randKey;
String encString = new String(Base64.encode(encoded));
encString = encString.substring(0, encString.length()-1) + randKey;
return encString;
}
public void AESDecrypt(String in) throws DataLengthException, IllegalStateException, IOException, InvalidCipherTextException {
byte[] decKey = key;
byte[] msg = in.getBytes();
byte randKey = msg[msg.length-1];
decKey[randKey&0x1f] = randKey;
byte[] trimMsg = new byte[msg.length-1];
System.arraycopy(msg, 0, trimMsg, 0, trimMsg.length);
in = new String(trimMsg);
RijndaelEngine rijndaelEngine = new RijndaelEngine(256);
PaddedBufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(rijndaelEngine), new ZeroBytePadding());
ParametersWithIV keyParameter = new ParametersWithIV(new KeyParameter(decKey), iv);
cipher.init(false, keyParameter);
byte[] encoded = Base64.decode(in.trim());
byte[] decoded = new byte[cipher.getOutputSize(encoded.length)];
int len = cipher.processBytes(encoded, 0, encoded.length, decoded, 0);
cipher.doFinal(decoded, len);
String decString = new String(decoded);
}
Here is a test function I am using to send and receive messages:
public void serverTest() throws DataLengthException, IllegalStateException, InvalidCipherTextException, IOException {
//out = AESEncrypt(out);
outputStream.write(out + "\n");
outputStream.flush();
String msg = "";
while ((msg = inputStream.readLine()) != null) {
AESDecrypt(msg);
}
}
The key and iv don't change with the exception of the last byte in the key. If I am encrypting I get a random base64 char and change the last byte to that. If its decryption I get the last byte from the message and set the last value of the key to it for decryption.
In the c++ example there was an unencrypted message and two encrypted messages. I could deal with those fine.
Here is the problem, when I send my message to the remote server "encrypted" the app waits for a response until the connection times out but never gets one. If I send the message unencrypted I get either 7 responses which I can successfully decrypt and finally
org.bouncycastle.util.encoders.DecoderException: unable to decode base64 string:
String index out of range: -4 at org.bouncycastle.util.encoders.Base64.decode(Unknown Source)
or my last line before the error will look like this:
?"??n?i???el????s???!_S=??ah????CR??l6??]?{?l??Y?????Gn???+?????9!'??gU&4>??{X????G?.$c=??0?5??GP???_Q5????8??Z\?~???<Kr?????[2\ ???a$?C??z%?W???{?.?????eR?j????~?B"$??"z??W;???<?Yu??Y*???Z?K?e!?????f?;O(?Zw0B??g<???????????,)?L>???A"?????<?????W??#\???f%??j ?EhY/?? ?5R?34r???#?1??I??????M
If I set the encryption/decryption to use PKCS7Padding I get no response when my message is encrypted still but with decryption from the server I get between 2 to 6 responses and then
org.bouncycastle.crypto.InvalidCipherTextException: pad block corrupted
I am at a loss with this. I don't know what I might be doing wrong so I have come here. I'm hoping the so community can point out my errors and guide me in the right direction.
I have a bit of an update I found my error in the encryption. I wasn't placing the random base64 value at the end of the encrypted string correctly so now I am doing like this.
encString += (char)randKey;
I can get response from the server now. Now the problem is I will some times get one or two readable lines but the rest are all garbage. I asked the individuals who run the server about it and they said in some c# code that they reference the have
return UTF8Encoding.UTF8.GetString(resultArray);
and thats all I have to go off of. I have tried UTF-8 encoding any place where I do getBytes or new String, and I have tried making the BurrferReader stream UTF-8 but it's still garbage.
Have you seedn the BCgit? this has bouncycastle code and examples. I am using the Csharp version in this repository. https://github.com/bcgit/bc-java
All crypto primitive examples are stored here: https://github.com/bcgit/bc-java/tree/master/core/src/test/java/org/bouncycastle/crypto/test
Try this code for testing Aes-CBC
private void testNullCBC()
throws InvalidCipherTextException
{
BufferedBlockCipher b = new BufferedBlockCipher(new CBCBlockCipher(new AESEngine()));
KeyParameter kp = new KeyParameter(Hex.decode("5F060D3716B345C253F6749ABAC10917"));
b.init(true, new ParametersWithIV(kp, new byte[16]));
byte[] out = new byte[b.getOutputSize(tData.length)];
int len = b.processBytes(tData, 0, tData.length, out, 0);
len += b.doFinal(out, len);
if (!areEqual(outCBC1, out))
{
fail("no match on first nullCBC check");
}
b.init(true, new ParametersWithIV(null, Hex.decode("000102030405060708090a0b0c0d0e0f")));
len = b.processBytes(tData, 0, tData.length, out, 0);
len += b.doFinal(out, len);
if (!areEqual(outCBC2, out))
{
fail("no match on second nullCBC check");
}
}
I am trying to read byte[] that is being send from a client to a server.
This is my client code...
din = new DataInputStream(socket.getInputStream());
dout = new DataOutputStream(socket.getOutputStream());
Cipher cipher = Cipher.getInstance("RSA");
// encrypt the aeskey using the public key
cipher.init(Cipher.ENCRYPT_MODE, pk);
byte[] cipherText = cipher.doFinal(aesKey.getEncoded());
dout.write(cipherText);
And this is my server code...
DataInputStream dis = new DataInputStream(socket.getInputStream());
DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
String chiper = dis.readUTF();
System.out.println(chiper);
However, the dis.readUTF(); line fails with an exception...
java.io.EOFException at java.io.DataInputStream.readFully(DataInputStream.java:197)
at java.io.DataInputStream.readUTF(DataInputStream.java:609)
at java.io.DataInputStream.readUTF(DataInputStream.java:564)
at gameserver.ClientHandler.run(GameServer.java:65)
Could someone please help me understand why this doesn't work.
For starters, if you write a sequence of (encrypted!) bytes at one end, and trying to read a UTF-formatted string at the other end...you're going to have a bad time.
I'd suggest that on the client side you should do something like
dout.writeInt(cipherText.length);
dout.write(cipherText);
and then on the server side you should do something like
int byteLength = dis.readInt(); // now I know how many bytes to read
byte[] theBytes = new byte[byteLength];
dis.readFully(theBytes);
DataIputStream.readUTF() is for data that you have written with DataOutputStream.writeUTF()`. You haven't written UTF so you can't read it.
This is binary data so you shouldn't be thinking about UTF or strings at all. Write the length of the array with writeInt(), then the array with write(). At the other end, read the length with readInt(), allocate a byte[] buffer that big and then read the ciphertext into it with readFully().
Yo have to get the message with the read method and get the number of characters of the real messages and then convert this to a string
int bytesRead = 0;
byte[] messageByte = new byte[1000];
bytesRead = dis.read(messageByte);
String chiper = new String(messageByte, 0, bytesRead);
System.out.println(chiper);
on client side, you should convert the byte[] array to String and use
dout.writeUTF() to send the converted String.