// --- BEGIN COPYRIGHT BLOCK ---
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; version 2 of the License.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
//
// (C) 2007 Red Hat, Inc.
// All rights reserved.
// --- END COPYRIGHT BLOCK ---
package org.mozilla.jss.netscape.security.x509;

import java.io.IOException;
import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.SignatureException;
import java.security.cert.CertificateEncodingException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.Date;

import org.mozilla.jss.netscape.security.pkcs.PKCS10;

/**
 * Generate a pair of keys, and provide access to them. This class is
 * provided primarily for ease of use.
 *
 * <P>
 * This provides some simple certificate management functionality. Specifically, it allows you to create self-signed
 * X.509 certificates as well as PKCS 10 based certificate signing requests.
 *
 * <P>
 * Keys for some public key signature algorithms have algorithm parameters, such as DSS/DSA. Some sites' Certificate
 * Authorities adopt fixed algorithm parameters, which speeds up some operations including key generation and signing.
 * <em>At this time, this interface
 * does not provide a way to provide such algorithm parameters, e.g.
 * by providing the CA certificate which includes those parameters.</em>
 *
 * <P>
 * Also, note that at this time only signature-capable keys may be acquired through this interface. Diffie-Hellman keys,
 * used for secure key exchange, may be supported later.
 *
 * @author David Brownell
 * @author Hemma Prafullchandra
 * @version 1.44
 * @see PKCS10
 * @see X509CertImpl
 */
public final class CertAndKeyGen {
    /**
     * Creates a CertAndKeyGen object for a particular key type
     * and signature algorithm.
     *
     * @param keyType type of key, e.g. "RSA", "DSA"
     * @param sigAlg name of the signature algorithm, e.g. "MD5WithRSA",
     *            "MD2WithRSA", "SHAwithDSA".
     * @exception NoSuchAlgorithmException on unrecognized algorithms.
     */
    public CertAndKeyGen(String keyType, String sigAlg)
            throws NoSuchAlgorithmException {
        keyGen = KeyPairGenerator.getInstance(keyType);
        this.sigAlg = sigAlg;
    }

    // want "public void generate (X509Certificate)" ... inherit DSA/D-H param

    /**
     * Generates a random public/private key pair, with a given key
     * size. Different algorithms provide different degrees of security
     * for the same key size, because of the "work factor" involved in
     * brute force attacks. As computers become faster, it becomes
     * easier to perform such attacks. Small keys are to be avoided.
     *
     * <P>
     * Note that not all values of "keyBits" are valid for all algorithms, and not all public key algorithms are
     * currently supported for use in X.509 certificates. If the algorithm you specified does not produce X.509
     * compatible keys, an invalid key exception is thrown.
     *
     * @param keyBits the number of bits in the keys.
     * @exception InvalidKeyException if the environment does not
     *                provide X.509 public keys for this signature algorithm.
     */
    public void generate(int keyBits)
            throws InvalidKeyException {
        KeyPair pair;

        try {
            keyGen.initialize(keyBits);
            pair = keyGen.generateKeyPair();

        } catch (Exception e) {
            throw new IllegalArgumentException(e.getMessage());
        }

        PublicKey publicKey = pair.getPublic();

        if (publicKey instanceof X509Key) {
            this.publicKey = (X509Key) publicKey;

        } else {
            throw new InvalidKeyException("public key " + publicKey +
                      " not an X509Key.");
        }
        privateKey = pair.getPrivate();
    }

    /**
     * Returns the public key of the generated key pair.
     */
    public X509Key getPublicKey() {
        return publicKey;
    }

    /**
     * Returns the private key of the generated key pair.
     *
     * <P>
     * <STRONG><em>Be extremely careful when handling private keys.
     * When private keys are not kept secret, they lose their ability
     * to securely authenticate specific entities ... that is a huge
     * security risk!</em></STRONG>
     */
    public PrivateKey getPrivateKey() {
        return privateKey;
    }

    /**
     * Returns a self-signed X.509v3 certificate for the public key.
     * The certificate is immediately valid. No extensions.
     *
     * <P>
     * Such certificates normally are used to identify a "Certificate Authority" (CA). Accordingly, they will not always
     * be accepted by other parties. However, such certificates are also useful when you are bootstrapping your security
     * infrastructure, or deploying system prototypes.
     *
     * @param myname X.500 name of the subject (who is also the issuer)
     * @param validity how long the certificate should be valid, in seconds
     * @exception CertificateException on certificate handling errors.
     * @exception InvalidKeyException on key handling errors.
     * @exception SignatureException on signature handling errors.
     * @exception NoSuchAlgorithmException on unrecognized algorithms.
     * @exception NoSuchProviderException on unrecognized providers.
     */
    public X509Certificate getSelfCertificate(X500Name myname, long validity)
            throws CertificateException, InvalidKeyException, SignatureException,
            NoSuchAlgorithmException, NoSuchProviderException {
        X500Signer issuer;
        X509CertImpl cert;
        Date firstDate, lastDate;

        try {
            issuer = getSigner(myname);

            firstDate = new Date();
            lastDate = new Date();
            lastDate.setTime(lastDate.getTime() + validity * 1000);

            CertificateValidity interval =
                                   new CertificateValidity(firstDate, lastDate);

            X509CertInfo info = new X509CertInfo();
            // Add all mandatory attributes
            info.set(X509CertInfo.VERSION,
                     new CertificateVersion(CertificateVersion.V1));
            info.set(X509CertInfo.SERIAL_NUMBER,
                    new CertificateSerialNumber((int) (firstDate.getTime() / 1000)));
            AlgorithmId algID = issuer.getAlgorithmId();
            info.set(X509CertInfo.ALGORITHM_ID,
                     new CertificateAlgorithmId(algID));
            info.set(X509CertInfo.SUBJECT, new CertificateSubjectName(myname));
            info.set(X509CertInfo.KEY, new CertificateX509Key(publicKey));
            info.set(X509CertInfo.VALIDITY, interval);
            info.set(X509CertInfo.ISSUER,
                     new CertificateIssuerName(issuer.getSigner()));

            cert = new X509CertImpl(info);
            cert.sign(privateKey, algID.getName());

            return cert;

        } catch (IOException e) {
            throw new CertificateEncodingException("getSelfCertificate: " +
                                                    e.getMessage());
        }
    }

    /**
     * Returns a PKCS #10 certificate request. The caller uses either <code>PKCS10.print</code> or
     * <code>PKCS10.toByteArray</code> operations on the result, to get the request in an appropriate
     * transmission format.
     *
     * <P>
     * PKCS #10 certificate requests are sent, along with some proof of identity, to Certificate Authorities (CAs) which
     * then issue X.509 public key certificates.
     *
     * @param myname X.500 name of the subject
     * @exception InvalidKeyException on key handling errors.
     * @exception SignatureException on signature handling errors.
     */
    public PKCS10 getCertRequest(X500Name myname)
            throws InvalidKeyException, SignatureException {
        PKCS10 req = new PKCS10(publicKey);

        try {
            req.encodeAndSign(getSigner(myname));

        } catch (CertificateException e) {
            throw new SignatureException(sigAlg + " CertificateException");

        } catch (IOException e) {
            throw new SignatureException(sigAlg + " IOException");

        } catch (NoSuchAlgorithmException e) {
            // "can't happen"
            throw new SignatureException(sigAlg + " unavailable?");
        }
        return req;
    }

    private X500Signer getSigner(X500Name me)
            throws InvalidKeyException, NoSuchAlgorithmException {
        Signature signature = Signature.getInstance(sigAlg);

        signature.initSign(privateKey);
        return new X500Signer(signature, me);
    }

    private String sigAlg;
    private KeyPairGenerator keyGen;
    private X509Key publicKey;
    private PrivateKey privateKey;
}
