vxiHCPd3

1import java.io.*;
2import java.net.*;
3import java.util.*;
4import java.security.*;
5import java.security.spec.*;
6import javax.crypto.*;
7import javax.crypto.spec.*;
8import java.math.BigInteger;
9import java.nio.ByteBuffer;
10
11public class Client {
12
13    public static void main(String [] args) throws Exception {
14
15        String host = args[0];
16        int port = Integer.parseInt(args[1]);
17        String userId = args[2];
18
19        // Connect to server
20        Socket s = new Socket(host, port);
21        DataInputStream din = new DataInputStream(s.getInputStream());
22        DataOutputStream dout = new DataOutputStream(s.getOutputStream());
23        ObjectInputStream oin = new ObjectInputStream(s.getInputStream());
24        ObjectOutputStream oout = new ObjectOutputStream(s.getOutputStream());
25
26        dout.writeUTF(userId);
27        SecretKey desedeKey = keyAgreement(oin, oout,userId,din,dout);
28
29        byte [] encryptedoutput = new byte[din.readInt()];
30        din.readFully(encryptedoutput);
31
32        Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
33        cipher.init(Cipher.DECRYPT_MODE, desedeKey);
34         String fileval = new  String(cipher.doFinal(encryptedoutput));
35
36        System.out.println(fileval);
37
38    }
39
40
41
42
43    // Stage 2: manual DH
44    private static SecretKey keyAgreement(ObjectInputStream oin, ObjectOutputStream oout,String userId,DataInputStream in,DataOutputStream out) throws Exception {
45
46        String skip1024String =
47                "F488FD584E49DBCD20B49DE49107366B336C380D451D0F7C88B31C7C5B2D8EF6"+
48                        "F3C923C043F0A55B188D8EBB558CB85D38D334FD7C175743A31D186CDE33212C"+
49                        "B52AFF3CE1B1294018118D7C84A70A72D686C40319C807297ACA950CD9969FAB"+
50                        "D00A509B0246D3083D66A45D419F9C7CBD894B221926BAABA25EC355E92F78C7";
51
52        BigInteger base = BigInteger.valueOf(2);
53        BigInteger modulus = new BigInteger(skip1024String, 16);
54
55        BigInteger b;
56        do {
57            b = new BigInteger(1024, new Random());
58        }while(b.bitLength() < 1024);
59
60        BigInteger eb = base.modPow(b, modulus);
61        BigInteger ea = (BigInteger)oin.readObject();
62        oout.writeObject(eb);
63
64        BigInteger key = ea.modPow(b, modulus);
65
66        byte[] keyBytes = key.toByteArray();
67        SecretKeyFactory desedeFactory = SecretKeyFactory.getInstance("DESede");
68        KeySpec spec = new DESedeKeySpec(keyBytes);
69
70        SecretKey finalkey =  desedeFactory.generateSecret(spec);
71
72        ObjectInputStream keyIn = new ObjectInputStream(new FileInputStream(userId+".prv"));
73        PrivateKey privateKey = (PrivateKey) keyIn.readObject();
74        keyIn.close();
75
76        Signature sig = Signature.getInstance("DSA");
77        sig.initSign(privateKey);
78        sig.update(eb.toByteArray());
79        sig.update(ea.toByteArray());
80        byte[] signature = sig.sign();
81
82        Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
83        cipher.init(Cipher.ENCRYPT_MODE, finalkey);
84        byte[] output = cipher.doFinal(signature);
85        out.writeInt(output.length);
86        out.write(output);
87
88        byte [] encryptedServerSignature = new byte[in.readInt()];
89        in.readFully(encryptedServerSignature);
90
91        Cipher dcipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
92        dcipher.init(Cipher.DECRYPT_MODE, finalkey);
93        byte [] signatureServer = dcipher.doFinal(encryptedServerSignature);
94
95        ObjectInputStream keyInServer = new ObjectInputStream(new FileInputStream("server.pub"));
96        PublicKey publicKey = (PublicKey) keyInServer.readObject();
97        keyInServer.close();
98
99        Signature sigServer = Signature.getInstance("DSA");
100        sigServer.initVerify(publicKey);
101        sigServer.update(ea.toByteArray());
102        sigServer.update(eb.toByteArray());
103
104        if (sigServer.verify(signatureServer))
105            System.out.println("Client logged in");
106        else {
107            System.out.println("Client failed to log in");
108            System.exit(-1);
109        }
110
111        return finalkey;
112    }
113    
114}