com.tasktop.c2c.server.internal.profile.crypto.OpenSSHPublicKeyReader.java Source code

Introduction

Here is the source code for com.tasktop.c2c.server.internal.profile.crypto.OpenSSHPublicKeyReader.java

Source

/*******************************************************************************
 * Copyright (c) 2010, 2012 Tasktop Technologies
 * Copyright (c) 2010, 2011 SpringSource, a division of VMware
 * 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Tasktop Technologies - initial API and implementation
 ******************************************************************************/
package com.tasktop.c2c.server.internal.profile.crypto;

import java.io.IOException;
import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.RSAPublicKeySpec;
import java.util.Arrays;

import org.apache.commons.codec.binary.Base64;
import org.apache.commons.codec.binary.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.tasktop.c2c.server.profile.domain.internal.SshPublicKey;

/**
 * an implementation of <a href="http://www.ietf.org/rfc/rfc4253.txt">RFC 4253</a>
 * 
 * @author David Green
 * @see http://www.ietf.org/rfc/rfc4253.txt
 */
public class OpenSSHPublicKeyReader implements PublicKeyReader {

    private static final byte[] FORMAT = new byte[] { 's', 's', 'h', '-', 'r', 's', 'a' };

    public SshPublicKey readPublicKey(String keySpec) {
        keySpec = keySpec.trim();
        String[] parts = keySpec.split(" ");
        if (parts.length >= 2) {
            String algorithm = parts[0];
            String base64Data = parts[1];
            if (algorithm.equals("ssh-rsa")) {
                SshPublicKey sshPublicKey = new SshPublicKey();
                sshPublicKey.setAlgorithm("RSA");
                byte[] decodedData = Base64.decodeBase64(StringUtils.getBytesUtf8(base64Data));

                Rfc4253Reader reader = new Rfc4253Reader(decodedData, 0);

                try {
                    byte[] format = reader.readBytes();
                    byte[] exponent = reader.readBytes();
                    byte[] modulus = reader.readBytes();

                    if (Arrays.equals(FORMAT, format)) {
                        BigInteger exp = new BigInteger(exponent);
                        BigInteger mod = new BigInteger(modulus);
                        RSAPublicKeySpec rsaPublicKeySpec = new RSAPublicKeySpec(mod, exp);
                        try {
                            PublicKey publicKey = KeyFactory.getInstance("RSA").generatePublic(rsaPublicKeySpec);
                            sshPublicKey.setKeyData(publicKey.getEncoded());
                            return sshPublicKey;
                        } catch (InvalidKeySpecException t) {
                            getLogger().warn("Invalid key spec: " + t.getMessage(), t);
                        } catch (NoSuchAlgorithmException t) {
                            getLogger().warn("Invalid algorithm: " + t.getMessage(), t);
                        }
                    }

                } catch (IOException e) {
                    // ignore
                }
            }
        }
        return null;
    }

    private Logger getLogger() {
        return LoggerFactory.getLogger(OpenSSHPublicKeyReader.class);
    }

    public String computeEncodedKeyText(SshPublicKey key) {
        try {
            BigInteger exp = ((RSAPublicKey) key.getPublicKey()).getPublicExponent();
            BigInteger mod = ((RSAPublicKey) key.getPublicKey()).getModulus();
            Rfc4253Writer writer = new Rfc4253Writer();
            writer.writeBytes(FORMAT);
            writer.writeMpint(exp);
            writer.writeMpint(mod);
            return "ssh-rsa " + StringUtils.newStringUtf8(Base64.encodeBase64(writer.getBytes()));
        } catch (Exception e) {
            return null;
        }
    }
}