org.xdi.oxauth.cert.fingerprint.FingerprintHelper.java Source code

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Here is the source code for org.xdi.oxauth.cert.fingerprint.FingerprintHelper.java

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/*
 * oxAuth is available under the MIT License (2008). See http://opensource.org/licenses/MIT for full text.
 *
 * Copyright (c) 2014, Gluu
 */

package org.xdi.oxauth.cert.fingerprint;

import org.apache.commons.codec.binary.Hex;
import org.apache.log4j.Logger;

import java.io.ByteArrayOutputStream;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.interfaces.RSAPublicKey;

/**
 * Utility which help to calculate SSH RSA public key fingerprint
 * 
 * @author Yuriy Movchan
 * @version March 03, 2016
 */
public class FingerprintHelper {

    private static final Logger log = Logger.getLogger(FingerprintHelper.class);

    /*
     * Return SSH RSA public key fingerprint
     */
    public static String getPublicKeySshFingerprint(PublicKey publicKey)
            throws NoSuchAlgorithmException, IOException {
        if (publicKey instanceof RSAPublicKey) {
            return getPublicKeySshFingerprint((RSAPublicKey) publicKey);
        }

        throw new NoSuchAlgorithmException("Unsopported PublicKey type");
    }

    public static String getPublicKeySshFingerprint(RSAPublicKey publicKey)
            throws NoSuchAlgorithmException, IOException {
        MessageDigest digest = MessageDigest.getInstance("MD5");

        byte[] derEncoded = getDerEncoding(publicKey);
        byte[] fingerprint = digest.digest(derEncoded);

        return Hex.encodeHexString(fingerprint);
    }

    private static byte[] getDerEncoding(RSAPublicKey key) throws IOException {
        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
        DataOutputStream dataOutput = new DataOutputStream(buffer);
        writeDataWithLength("ssh-rsa".getBytes(), dataOutput);
        writeDataWithLength(key.getPublicExponent().toByteArray(), dataOutput);
        writeDataWithLength(key.getModulus().toByteArray(), dataOutput);

        return buffer.toByteArray();
    }

    private static void writeDataWithLength(byte[] data, DataOutput byteBuffer) throws IOException {
        byteBuffer.writeInt(data.length);
        byteBuffer.write(data);
    }

}