Ndtyjky

I'm making a simple project where a client encrypt a file with JCE (DES) and sends it to the server with sockets. The server receives it and decrypts it.It works perfectly till the part where the server has to decrypt the file.Indeed the CipherInputStream which should return the decrypted plain text results null but the FileInputStream that I use in the function is ok so I don't really know what the problem may be.

Client:

import jdk.internal.util.xml.impl.Input;

import javax.crypto.*;

import javax.crypto.spec.DESKeySpec;

import java.io.*;

import java.security.InvalidKeyException;

import java.security.NoSuchAlgorithmException;

import java.security.SecureRandom;

import java.security.spec.InvalidKeySpecException;

import java.util.Scanner;

import java.net.*;

import java.nio.file.Files;

import java.nio.file.Path;



public class Main {

    static private int porta = 81;

    static private String hostname = "localhost";





    public static void main(String args) {

        OutputStream outputStream = null;

        Socket socket = null;

        boolean bIsConnected = false;

        System.out.println("Inserisci il percorso del file che vuoi criptare");

        Scanner in = new Scanner(System.in);

        String path = in.nextLine(); //percorso da usare



        System.out.println("Inserisci la chiave di criptazione");



        String key = in.nextLine(); //Chiede la chiave di decriptazione (8 caratteri)



        File plaintext = new File(path);

        File encrypted = new File("Criptato.txt"); //salva il file nella cartella locale del progetto



        try {

            Encrypt(key, plaintext, encrypted);

            System.out.println("Crittazione completata");

        } catch (InvalidKeyException | NoSuchAlgorithmException | InvalidKeySpecException | NoSuchPaddingException | IOException e) {

            e.printStackTrace();

        }



        while (!bIsConnected) { //crittato il file aspetta che l'utente si colleghi al portale del server per mandare il file

            try {

                socket = new Socket(hostname, porta);

                bIsConnected = true;

            } catch (SocketException e) {

                e.printStackTrace();

            } catch (IOException e) {

                e.printStackTrace();

            }

        }



        byte bytes = new byte[16 * 1024];

        try {

            InputStream inp = new FileInputStream(encrypted);//converte il file in uno stream

            OutputStream outp = socket.getOutputStream();





            int count;

            while ((count = inp.read(bytes)) > 0) {

                outp.write(bytes, 0, count); //scrive sulla socket del server il contenuto del file byte per byte

            }

        } //si collega all'output stream della socket

        catch (IOException e) {

        }





    }



    private static void write(InputStream in, OutputStream out) throws IOException {

        byte buffer = new byte[64];

        int numOfBytesRead;

        while ((numOfBytesRead = in.read(buffer)) != -1) {

            out.write(buffer, 0, numOfBytesRead);

        }

        out.close();

        in.close();

    }



    public static void Encrypt(String key, File in, File out)

            throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeySpecException, IOException {

        FileInputStream fis = new FileInputStream(in);

        FileOutputStream fos = new FileOutputStream(out);



        DESKeySpec desKeySpec = new DESKeySpec(key.getBytes());



        SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");

        SecretKey secretKey = skf.generateSecret(desKeySpec);



        Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");



        cipher.init(Cipher.ENCRYPT_MODE, secretKey, SecureRandom.getInstance("SHA1PRNG"));

        CipherInputStream cis = new CipherInputStream(fis, cipher);

        write(cis, fos);

    }

}

Server:

import javax.crypto.*;

import javax.crypto.spec.DESKeySpec;

import java.io.*;

import java.nio.file.Paths;

import java.security.InvalidKeyException;

import java.security.NoSuchAlgorithmException;

import java.security.SecureRandom;

import java.security.spec.InvalidKeySpecException;

import java.util.Scanner;

import java.net.*;

import java.nio.file.Files;



public class Main {

    static private int portNumber = 81;



    public static void main(String args) {

        File criptato = new File("CriptatoServer.txt");

        File decriptato = new File("Decrittato.txt");

        System.out.println("Server running");

        // Listening in entrata

        ServerSocket socketServer;

        try {

            socketServer = new ServerSocket(portNumber);

        } catch (IOException e) {

            System.out.println("Impossibile ascoltare sulla porta.");

            e.printStackTrace();

            return;

        }



        while (true) {

            Socket socket = null;

            try {

                socket = socketServer.accept();

            } catch (IOException e) {

                System.out.println("Impossibile accettare client.");

                e.printStackTrace();

                return;

            }

            System.out.println("Ricevuto client socket!");







            InputStream in = null;

            OutputStream out = null;

            try {

                in = socket.getInputStream(); //prende ciò che arriva dal client

            } catch (IOException ex) {

                System.out.println("Can't get socket input stream. ");

            }



            try {

                out = new FileOutputStream(criptato); //scrive nel file criptato (sta copiando dal client)

            } catch (FileNotFoundException ex) {

                System.out.println("File not found. ");

            }



            byte bytes = new byte[16 * 1024];



            int count;

            try {

                while ((count = in.read(bytes)) > 0) {

                    out.write(bytes, 0, count);

                }

            }catch(IOException e){System.out.println("AHIAIAI");}





            System.out.println("Inserisci la chiave per decriptare il file e leggere il messaggio");

            Scanner ins = new Scanner(System.in);

            String key = ins.nextLine(); //chiave





            try {

               Decrypt(key, criptato, decriptato);

                System.out.println("Decrittazione completata");

           } catch (InvalidKeyException | NoSuchAlgorithmException | InvalidKeySpecException | NoSuchPaddingException | IOException e) {

                e.printStackTrace();

           }

        }

    }

    private static void write(InputStream in, OutputStream out) throws IOException {

        byte buffer = new byte[64];

        int numOfBytesRead;

        while ((numOfBytesRead = in.read(buffer)) != -1) {



            out.write(buffer, 0, numOfBytesRead);

        }

        out.close();

        in.close();

    }



    public static void Decrypt(String key, File in, File out)

            throws InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeySpecException, IOException {

        FileInputStream fis = new FileInputStream(in); //seems ok

        FileOutputStream fos = new FileOutputStream(out);



        DESKeySpec desKeySpec = new DESKeySpec(key.getBytes());



        SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");

        SecretKey secretKey = skf.generateSecret(desKeySpec);



        Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");



        cipher.init(Cipher.DECRYPT_MODE, secretKey, SecureRandom.getInstance("SHA1PRNG"));

        CipherInputStream cis = new CipherInputStream(fis, cipher); //returns null

        write(cis, fos);

    }

    public static String getFileContent(

            FileInputStream fis,

            String          encoding ) throws IOException

    {

        try( BufferedReader br =

                     new BufferedReader( new InputStreamReader(fis, encoding )))

        {

            StringBuilder sb = new StringBuilder();

            String line;

            while(( line = br.readLine()) != null ) {

                sb.append( line );

                sb.append( 'n' );

            }

            return sb.toString();

        }

    }

}

I know it's a bit messy but I'm still working on it.

You have neglected to close the output side of the client's socket after you finished writing to it. Thus the connection is left open, and the server side simply blocks in its read loop waiting for more input.

Your exception handling is so complicated it actually obscures the logic of your code. On the client side you can do something like:

InputStream inp = new FileInputStream(encrypted);//converte il file in uno stream

OutputStream outp = socket.getOutputStream();





int count;

while ((count = inp.read(bytes)) > 0) {

    outp.write(bytes, 0, count); //scrive sulla socket del server il contenuto del file byte per byte

}

outp.close();

socket.close();