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2 package com.trilead.ssh2.crypto.dh;
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3
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4 import java.io.IOException;
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5 import java.io.UnsupportedEncodingException;
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6 import java.math.BigInteger;
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7
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8 import com.trilead.ssh2.crypto.digest.HashForSSH2Types;
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9 import com.trilead.ssh2.log.Logger;
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10
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11
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12 /**
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13 * DhExchange.
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14 *
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15 * @author Christian Plattner, plattner@trilead.com
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16 * @version $Id: DhExchange.java,v 1.2 2008/04/01 12:38:09 cplattne Exp $
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17 */
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18 public abstract class GenericDhExchange {
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19 private static final Logger log = Logger.getLogger(GenericDhExchange.class);
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20
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21 /* Shared secret */
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22
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23 BigInteger sharedSecret;
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24
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25 protected GenericDhExchange() {
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26 }
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27
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28 public static GenericDhExchange getInstance(String algo) {
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29 if (algo.startsWith("ecdh-sha2-")) {
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30 return new EcDhExchange();
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31 }
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32 else {
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33 return new DhExchange();
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34 }
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35 }
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36
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37 public abstract void init(String name) throws IOException;
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38
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39 /**
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40 * @return Returns the e (public value)
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41 * @throws IllegalStateException
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42 */
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43 public abstract byte[] getE();
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44
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45 /**
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46 * @return Returns the server's e (public value)
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47 * @throws IllegalStateException
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48 */
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49 protected abstract byte[] getServerE();
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50
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51 /**
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52 * @return Returns the shared secret k.
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53 * @throws IllegalStateException
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54 */
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55 public BigInteger getK() {
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56 if (sharedSecret == null)
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57 throw new IllegalStateException("Shared secret not yet known, need f first!");
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58
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59 return sharedSecret;
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60 }
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61
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62 /**
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63 * @param f
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64 */
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65 public abstract void setF(byte[] f) throws IOException;
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66
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67 public byte[] calculateH(byte[] clientversion, byte[] serverversion, byte[] clientKexPayload,
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68 byte[] serverKexPayload, byte[] hostKey) throws UnsupportedEncodingException {
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69 HashForSSH2Types hash = new HashForSSH2Types(getHashAlgo());
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70
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71 if (log.isEnabled()) {
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72 log.log(90, "Client: '" + new String(clientversion, "ISO-8859-1") + "'");
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73 log.log(90, "Server: '" + new String(serverversion, "ISO-8859-1") + "'");
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74 }
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75
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76 hash.updateByteString(clientversion);
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77 hash.updateByteString(serverversion);
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78 hash.updateByteString(clientKexPayload);
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79 hash.updateByteString(serverKexPayload);
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80 hash.updateByteString(hostKey);
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81 hash.updateByteString(getE());
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82 hash.updateByteString(getServerE());
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83 hash.updateBigInt(sharedSecret);
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84 return hash.getDigest();
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85 }
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86
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87 public abstract String getHashAlgo();
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88 }
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