ssh2keyfingerprint.java

一个非常好的ssh客户端实现

/******************************************************************************
 *
 * Copyright (c) 1999-2003 AppGate Network Security AB. All Rights Reserved.
 * 
 * This file contains Original Code and/or Modifications of Original Code as
 * defined in and that are subject to the MindTerm Public Source License,
 * Version 2.0, (the 'License'). You may not use this file except in compliance
 * with the License.
 * 
 * You should have received a copy of the MindTerm Public Source License
 * along with this software; see the file LICENSE.  If not, write to
 * AppGate Network Security AB, Otterhallegatan 2, SE-41118 Goteborg, SWEDEN
 *
 *****************************************************************************/

package com.mindbright.ssh2;

import com.mindbright.jca.security.MessageDigest;
import com.mindbright.jca.security.NoSuchAlgorithmException;

import com.mindbright.util.HexDump;

/**
 * Contains static methods for calculating fingerprints on keys.
 */
public final class SSH2KeyFingerprint {

    /**
     * Calculates the MD5 checksum of the given blob.
     *
     * @param blob Data to calculate checksum of.
     *
     * @return The checksum expressed as a hexadecimal string.
     */
    public static String md5Hex(byte[] blob) {
	MessageDigest md5 = null;
	try {
	    md5 = MessageDigest.getInstance("MD5");
	    md5.update(blob);
	} catch (NoSuchAlgorithmException e) {
	    throw new Error("SSH2KeyFingerprint.md5Hex: " + e);
	}

	byte[] raw       = md5.digest();
	String hex       = HexDump.toString(raw);
	StringBuffer fps = new StringBuffer();
	for(int i = 0; i < hex.length(); i += 2) {
	    fps.append(hex.substring(i, i + 2));
	    if(i < hex.length() - 2) {
		fps.append(":");
	    }
	}
	return fps.toString();
    }

    /**
     * Calculates the bubble-babble checksum of the given blob.
     *
     * @param blob Data to calculate checksum of.
     *
     * @return The bubble-babble checksum string.
     */
    public static String bubbleBabble(byte[] blob) {
	MessageDigest sha1 = null;
	try {
	    sha1 = MessageDigest.getInstance("SHA1");
	    sha1.update(blob);
	} catch (NoSuchAlgorithmException e) {
	    throw new Error("SSH2KeyFingerprint.bubbleBabble: " + e);
	}

	byte[]       raw        = sha1.digest();
	StringBuffer retval     = new StringBuffer();
	char[]       consonants = { 'b', 'c', 'd', 'f', 'g', 'h', 'k', 'l', 'm',
				    'n', 'p', 'r', 's', 't', 'v', 'z', 'x' };
	char[]       vowels     = { 'a', 'e', 'i', 'o', 'u', 'y' };
	int          rounds     = (raw.length / 2) + 1;
	int          seed       = 1;

	retval.append('x');

	for(int i = 0; i < rounds; i++) {
	    int idx0, idx1, idx2, idx3, idx4;
	    if((i + 1 < rounds) || ((raw.length % 2) != 0)) {
		idx0 = ((((((int)(raw[2 * i])) & 0xff) >>> 6) & 3) + seed) % 6;
		idx1 = ((((int)(raw[2 * i])) & 0xff) >>> 2) & 15;
		idx2 = (((((int)(raw[2 * i])) & 0xff) & 3) + (seed / 6)) % 6;
		retval.append(vowels[idx0]);
		retval.append(consonants[idx1]);
		retval.append(vowels[idx2]);
		if((i + 1) < rounds) {
		    idx3 = ((((int)(raw[(2 * i) + 1])) & 0xff) >>> 4) & 15;
		    idx4 = (((int)(raw[(2 * i) + 1])) & 0xff) & 15;
		    retval.append(consonants[idx3]);
		    retval.append('-');
		    retval.append(consonants[idx4]);
		    seed = ((seed * 5) +
			    (((((int)(raw[2 * i])) & 0xff) * 7) +
			     (((int)(raw[(2 * i) + 1])) & 0xff))) % 36;
		}
	    } else {
		idx0 = seed % 6;
		idx1 = 16;
		idx2 = seed / 6;
		retval.append(vowels[idx0]);
		retval.append(consonants[idx1]);
		retval.append(vowels[idx2]);
	    }
	}
	retval.append('x');

	return retval.toString();
    }
}