JkQVH599

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 Server {
12
13    static ArrayList<Double> pastRand;
14
15    public static void main(String args[]) throws Exception {
16
17        // Listen for connections
18        int port = Integer.parseInt(args[0]);
19        ServerSocket ss = new ServerSocket(port);
20
21        // infinite loop
22        while(true) {
23
24            try {
25
26                Socket s = ss.accept();
27                DataInputStream din = new DataInputStream(s.getInputStream());
28                DataOutputStream dout = new DataOutputStream(s.getOutputStream());
29                ObjectOutputStream oout = new ObjectOutputStream(s.getOutputStream());
30                ObjectInputStream oin = new ObjectInputStream(s.getInputStream());
31
32                String userid = din.readUTF();
33
34                SecretKey desedeKey = keyAgreement(oin, oout,userid,dout,din);
35
36                BufferedReader br = new BufferedReader(new FileReader(userid));
37                String message = br.readLine();
38
39                Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
40                cipher.init(Cipher.ENCRYPT_MODE, desedeKey);
41                byte[] output = cipher.doFinal(message.getBytes("UTF8"));
42                dout.writeInt(output.length);
43                dout.write(output);
44
45
46            }
47            catch (EOFException e) {
48                System.err.println("client disconnected.");
49                continue;
50            }
51        }
52    }
53
54
55
56
57
58    // Stage 2: manual DH
59
60    private static SecretKey keyAgreement(ObjectInputStream oin, ObjectOutputStream oout,String userId,DataOutputStream dout,DataInputStream in) throws Exception {
61
62        String skip1024String =
63                "F488FD584E49DBCD20B49DE49107366B336C380D451D0F7C88B31C7C5B2D8EF6"+
64                        "F3C923C043F0A55B188D8EBB558CB85D38D334FD7C175743A31D186CDE33212C"+
65                        "B52AFF3CE1B1294018118D7C84A70A72D686C40319C807297ACA950CD9969FAB"+
66                        "D00A509B0246D3083D66A45D419F9C7CBD894B221926BAABA25EC355E92F78C7";
67        BigInteger base = BigInteger.valueOf(2);
68        BigInteger modulus = new BigInteger(skip1024String, 16);
69
70        BigInteger a;
71        do {
72            a = new BigInteger(1024, new Random());
73        }while(a.bitLength() < 1024);
74
75        BigInteger ea = base.modPow(a, modulus);
76        oout.writeObject(ea);
77        BigInteger eb = (BigInteger)oin.readObject();
78        BigInteger key = eb.modPow(a, modulus);
79
80        byte[] keyBytes = key.toByteArray();
81        SecretKeyFactory desedeFactory = SecretKeyFactory.getInstance("DESede");
82        KeySpec spec = new DESedeKeySpec(keyBytes);
83
84        SecretKey finalkey =  desedeFactory.generateSecret(spec);
85
86        byte [] encryptedsignature = new byte[in.readInt()];
87        in.readFully(encryptedsignature);
88
89        Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
90        cipher.init(Cipher.DECRYPT_MODE, finalkey);
91        byte [] signature = cipher.doFinal(encryptedsignature);
92
93        ObjectInputStream keyIn = new ObjectInputStream(new FileInputStream(userId+".pub"));
94        PublicKey publicKey = (PublicKey) keyIn.readObject();
95        keyIn.close();
96
97        Signature sig = Signature.getInstance("DSA");
98        sig.initVerify(publicKey);
99        sig.update(eb.toByteArray());
100        sig.update(ea.toByteArray());
101
102        if (sig.verify(signature))
103            System.out.println("Client logged in");
104        else {
105            System.out.println("Client failed to log in");
106            System.exit(-1);
107        }
108
109
110        ObjectInputStream keyInServer = new ObjectInputStream(new FileInputStream("server.prv"));
111        PrivateKey privateKey = (PrivateKey) keyInServer.readObject();
112        keyInServer.close();
113
114        Signature sigServer = Signature.getInstance("DSA");
115        sigServer.initSign(privateKey);
116        sigServer.update(ea.toByteArray());
117        sigServer.update(eb.toByteArray());
118        byte[] signatureServer = sigServer.sign();
119
120        Cipher ecipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
121        ecipher.init(Cipher.ENCRYPT_MODE, finalkey);
122        byte[] output = ecipher.doFinal(signatureServer);
123        dout.writeInt(output.length);
124        dout.write(output);
125        return finalkey;
126    }
127
128
129
130
131
132}