HnrqKSGM

1import java.net.*;
2import java.io.*;
3import javax.crypto.*;
4import javax.crypto.spec.IvParameterSpec;
5import javax.crypto.spec.SecretKeySpec;
6import java.security.InvalidAlgorithmParameterException;
7import java.security.InvalidKeyException;
8import java.security.MessageDigest;
9import java.security.NoSuchAlgorithmException;
10import java.util.Arrays;
11
12public class Server{
13    public static void main(String args[]){
14        int number=0;
15        try{
16            int serverPort = 4567;
17            ServerSocket listenSocket = new ServerSocket(serverPort);
18            while(true) {
19                Socket clientSocket = listenSocket.accept();
20                new Connection(clientSocket,number);
21                number++;
22            }
23        } catch(IOException e) {
24            System.out.println("Listen:" + e.getMessage());
25        }
26    }
27}
28
29class Connection extends Thread {
30    DataInputStream in;
31    DataOutputStream out;
32    Socket clientSocket;
33    int number;
34    int stopped;
35
36    public Connection (Socket aClientSocket,int clientNumber) {
37        try{
38            number=clientNumber;
39            clientSocket = aClientSocket;
40            in = new DataInputStream(clientSocket.getInputStream());
41            out = new DataOutputStream(clientSocket.getOutputStream());
42            stopped=0;
43            this.start();
44        }catch(IOException e){System.out.println("Connection:" + e.getMessage());}
45    }
46
47    public void run(){
48        try{
49            while(true){
50                //key
51                byte [] key = {1,2,3,4,1,2,3,4,1,2,3,4,1,2,3,4};
52
53                //hash function and new keys
54                MessageDigest md = MessageDigest.getInstance("SHA-256");
55
56                byte [] byte1 = {1};
57                byte [] aux1 = concat(key, byte1);
58                byte [] hash1= md.digest(aux1);
59                SecretKey k1 = new SecretKeySpec(hash1, 0, hash1.length, "AES");
60
61                byte [] byte2 = {2};
62                byte [] aux2 = concat(key, byte2);
63                byte [] hash2= md.digest(aux2);
64                SecretKey k2 = new SecretKeySpec(hash2, 0, hash2.length, "AES");
65
66                //message authentication code
67                Mac mac = Mac.getInstance("HmacSHA256");
68                mac.init(k2);
69                int nSeq = 0;
70
71                //nonce - receives IV in plaintext
72                byte[] nonce=new byte[16];
73                in.read(nonce);
74                IvParameterSpec iv = new IvParameterSpec(nonce);
75
76                //D(m, k1) = c - só se decifra se a autenticação do mac correr bem
77                Cipher c = Cipher.getInstance("AES/CTR/PKCS5Padding");
78                c.init(Cipher.DECRYPT_MODE, k1, iv);
79                int text;
80
81                while (stopped!=1){
82
83                    try{
84                        byte sizeInBytes[] = new byte[4]; // le 4 bytes que dizem o tamanho do pacote
85
86                        if(in.read(sizeInBytes)!=-1){ // se nao houver mais nada para ler acaba
87
88
89
90                            int size=convertByteToInt(sizeInBytes);
91                            //System.out.println("size : "+size);
92
93                            byte authTagClient[] = new byte[32]; // le 256 bits do mac
94                            in.read(authTagClient);
95
96
97                            byte enc[] = new byte[size]; // le o ciphertext
98                            in.read(enc);
99
100
101                            byte [] nSeqByte = intToByteArray(nSeq);
102                            byte [] authTagAux = concat(enc, nSeqByte);
103                            byte [] authTag = mac.doFinal(authTagAux);
104
105                            if(Arrays.equals(authTagClient, authTag)){
106                                byte [] dec=c.doFinal(enc);
107                                System.out.println("Text from client : "+new String (dec));
108                            }
109                            else{
110                                System.out.println("Invalid MAC");
111                            }
112
113                            nSeq++;
114                        }else{
115                            stopped=1;
116                        }
117
118                    }
119                    catch (IOException e) {
120                    }
121                }
122
123            }
124        }
125        catch (NoSuchPaddingException e) {
126            e.printStackTrace();
127        }
128
129        catch (NoSuchAlgorithmException e) {
130            e.printStackTrace();
131        }
132        catch (InvalidKeyException e) {
133            e.printStackTrace();
134        }
135        catch (InvalidAlgorithmParameterException e) {
136            e.printStackTrace();
137        } catch (BadPaddingException e) {
138            e.printStackTrace();
139        } catch (IllegalBlockSizeException e) {
140            e.printStackTrace();
141        } catch (IOException e) {
142            e.printStackTrace();
143        }
144    }
145
146    private byte [] concat(byte[] first, byte[] second) throws IOException {
147        ByteArrayOutputStream baos = new ByteArrayOutputStream();
148        baos.write(first);
149        baos.write(second);
150        byte [] result = baos.toByteArray();
151        baos.reset();
152        return result;
153    }
154
155    //https://stackoverflow.com/questions/2183240/java-integer-to-byte-array
156    public static final byte[] intToByteArray(int value) {
157        return new byte[]{
158                (byte)(value >>> 24),
159                (byte)(value >>> 16),
160                (byte)(value >>> 8),
161                (byte)value};
162    }
163
164    //https://stackoverflow.com/questions/4950598/convert-byte-to-int
165    public int convertByteToInt(byte[] b)
166    {
167        int value= 0;
168        for(int i=0; i<b.length; i++)
169            value = (value << 8) | b[i];
170        return value;
171    }
172}