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1
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2 package com.trilead.ssh2.crypto;
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3
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4
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5 import java.math.BigInteger;
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6
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7 import com.trilead.ssh2.crypto.digest.HashForSSH2Types;
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8
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9 /**
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10 * Establishes key material for iv/key/mac (both directions).
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11 *
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12 * @author Christian Plattner, plattner@trilead.com
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13 * @version $Id: KeyMaterial.java,v 1.1 2007/10/15 12:49:56 cplattne Exp $
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14 */
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15 public class KeyMaterial {
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16 public byte[] initial_iv_client_to_server;
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17 public byte[] initial_iv_server_to_client;
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18 public byte[] enc_key_client_to_server;
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19 public byte[] enc_key_server_to_client;
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20 public byte[] integrity_key_client_to_server;
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21 public byte[] integrity_key_server_to_client;
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22
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23 private static byte[] calculateKey(HashForSSH2Types sh, BigInteger K, byte[] H, byte type, byte[] SessionID,
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24 int keyLength) {
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25 byte[] res = new byte[keyLength];
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26 int dglen = sh.getDigestLength();
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27 int numRounds = (keyLength + dglen - 1) / dglen;
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28 byte[][] tmp = new byte[numRounds][];
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29 sh.reset();
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30 sh.updateBigInt(K);
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31 sh.updateBytes(H);
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32 sh.updateByte(type);
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33 sh.updateBytes(SessionID);
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34 tmp[0] = sh.getDigest();
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35 int off = 0;
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36 int produced = Math.min(dglen, keyLength);
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37 System.arraycopy(tmp[0], 0, res, off, produced);
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38 keyLength -= produced;
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39 off += produced;
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40
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41 for (int i = 1; i < numRounds; i++) {
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42 sh.updateBigInt(K);
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43 sh.updateBytes(H);
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44
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45 for (int j = 0; j < i; j++)
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46 sh.updateBytes(tmp[j]);
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47
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48 tmp[i] = sh.getDigest();
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49 produced = Math.min(dglen, keyLength);
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50 System.arraycopy(tmp[i], 0, res, off, produced);
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51 keyLength -= produced;
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52 off += produced;
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53 }
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54
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55 return res;
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56 }
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57
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58 public static KeyMaterial create(String hashAlgo, byte[] H, BigInteger K, byte[] SessionID, int keyLengthCS,
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59 int blockSizeCS, int macLengthCS, int keyLengthSC, int blockSizeSC, int macLengthSC)
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60 throws IllegalArgumentException {
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61 KeyMaterial km = new KeyMaterial();
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62 HashForSSH2Types sh = new HashForSSH2Types(hashAlgo);
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63 km.initial_iv_client_to_server = calculateKey(sh, K, H, (byte) 'A', SessionID, blockSizeCS);
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64 km.initial_iv_server_to_client = calculateKey(sh, K, H, (byte) 'B', SessionID, blockSizeSC);
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65 km.enc_key_client_to_server = calculateKey(sh, K, H, (byte) 'C', SessionID, keyLengthCS);
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66 km.enc_key_server_to_client = calculateKey(sh, K, H, (byte) 'D', SessionID, keyLengthSC);
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67 km.integrity_key_client_to_server = calculateKey(sh, K, H, (byte) 'E', SessionID, macLengthCS);
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68 km.integrity_key_server_to_client = calculateKey(sh, K, H, (byte) 'F', SessionID, macLengthSC);
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69 return km;
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70 }
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71 }
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