/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * particular file as subject to the "Classpath" exception as provided

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 */

package sun.security.provider.certpath;

import java.io.BufferedInputStream;

import java.io.ByteArrayInputStream;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.security.cert.CertificateEncodingException;

import java.security.cert.Certificate;

import java.security.cert.CertificateException;

import java.security.cert.CertificateFactory;

import java.security.cert.X509Certificate;

import java.util.*;

import java.security.cert.CertPath;

import sun.security.pkcs.ContentInfo;

import sun.security.pkcs.PKCS7;

import sun.security.pkcs.SignerInfo;

import sun.security.x509.AlgorithmId;

import sun.security.util.DerValue;

import sun.security.util.DerOutputStream;

import sun.security.util.DerInputStream;

/**

 * A {@link java.security.cert.CertPath CertPath} (certification path)

 * consisting exclusively of

 * {@link java.security.cert.X509Certificate X509Certificate}s.

 * <p>

 * By convention, X.509 <code>CertPath</code>s are stored from target

 * to trust anchor.

 * That is, the issuer of one certificate is the subject of the following

 * one. However, unvalidated X.509 <code>CertPath</code>s may not follow

 * this convention. PKIX <code>CertPathValidator</code>s will detect any

 * departure from this convention and throw a

 * <code>CertPathValidatorException</code>.

 *

 * @author      Yassir Elley

 * @since       1.4

 */

public class X509CertPath extends CertPath {

    private static final long serialVersionUID = 4989800333263052980L;

    /**

     * List of certificates in this chain

     */

    private List<X509Certificate> certs;

    /**

     * The names of our encodings.  PkiPath is the default.

     */

    private static final String COUNT_ENCODING = "count";

    private static final String PKCS7_ENCODING = "PKCS7";

    private static final String PKIPATH_ENCODING = "PkiPath";

    /**

     * List of supported encodings

     */

    private static final Collection<String> encodingList;

    static {

        List<String> list = new ArrayList<String>(2);

        list.add(PKIPATH_ENCODING);

        list.add(PKCS7_ENCODING);

        encodingList = Collections.unmodifiableCollection(list);

    }

    /**

     * Creates an <code>X509CertPath</code> from a <code>List</code> of

     * <code>X509Certificate</code>s.

     * <p>

     * The certificates are copied out of the supplied <code>List</code>

     * object.

     *

     * @param certs a <code>List</code> of <code>X509Certificate</code>s

     * @exception CertificateException if <code>certs</code> contains an element

     *                      that is not an <code>X509Certificate</code>

     */

    public X509CertPath(List<? extends Certificate> certs) throws CertificateException {

        super("X.509");

        // Ensure that the List contains only X509Certificates

        for (Object obj : (List<?>)certs) {

            if (obj instanceof X509Certificate == false) {

                throw new CertificateException

                    ("List is not all X509Certificates: "

                    + obj.getClass().getName());

            }

        }

        // Assumes that the resulting List is thread-safe. This is true

        // because we ensure that it cannot be modified after construction

        // and the methods in the Sun JDK 1.4 implementation of ArrayList that

        // allow read-only access are thread-safe.

        this.certs = Collections.unmodifiableList(

                new ArrayList<X509Certificate>((List<X509Certificate>)certs));

    }

    /**

     * Creates an <code>X509CertPath</code>, reading the encoded form

     * from an <code>InputStream</code>. The data is assumed to be in

     * the default encoding.

     *

     * @param is the <code>InputStream</code> to read the data from

     * @exception CertificateException if an exception occurs while decoding

     */

    public X509CertPath(InputStream is) throws CertificateException {

        this(is, PKIPATH_ENCODING);

    }

    /**

     * Creates an <code>X509CertPath</code>, reading the encoded form

     * from an InputStream. The data is assumed to be in the specified

     * encoding.

     *

     * @param is the <code>InputStream</code> to read the data from

     * @param encoding the encoding used

     * @exception CertificateException if an exception occurs while decoding or

     *   the encoding requested is not supported

     */

    public X509CertPath(InputStream is, String encoding)

            throws CertificateException {

        super("X.509");

        if (PKIPATH_ENCODING.equals(encoding)) {

            certs = parsePKIPATH(is);

        } else if (PKCS7_ENCODING.equals(encoding)) {

            certs = parsePKCS7(is);

        } else {

            throw new CertificateException("unsupported encoding");

        }

    }

    /**

     * Parse a PKIPATH format CertPath from an InputStream. Return an

     * unmodifiable List of the certificates.

     *

     * @param is the <code>InputStream</code> to read the data from

     * @return an unmodifiable List of the certificates

     * @exception CertificateException if an exception occurs

     */

    private static List<X509Certificate> parsePKIPATH(InputStream is)

            throws CertificateException {

        List<X509Certificate> certList = null;

        CertificateFactory certFac = null;

        if (is == null) {

            throw new CertificateException("input stream is null");

        }

        try {

            DerInputStream dis = new DerInputStream(readAllBytes(is));

            DerValue[] seq = dis.getSequence(3);

            if (seq.length == 0) {

                return Collections.<X509Certificate>emptyList();

            }

            certFac = CertificateFactory.getInstance("X.509");

            certList = new ArrayList<X509Certificate>(seq.length);

            // append certs in reverse order (target to trust anchor)

            for (int i = seq.length-1; i >= 0; i--) {

                certList.add((X509Certificate)certFac.generateCertificate

                    (new ByteArrayInputStream(seq[i].toByteArray())));

            }

            return Collections.unmodifiableList(certList);

        } catch (IOException ioe) {

            CertificateException ce = new CertificateException("IOException" +

                " parsing PkiPath data: " + ioe);

            ce.initCause(ioe);

            throw ce;

        }

    }

    /**

     * Parse a PKCS#7 format CertPath from an InputStream. Return an

     * unmodifiable List of the certificates.

     *

     * @param is the <code>InputStream</code> to read the data from

     * @return an unmodifiable List of the certificates

     * @exception CertificateException if an exception occurs

     */

    private static List<X509Certificate> parsePKCS7(InputStream is)

            throws CertificateException {

        List<X509Certificate> certList;

        if (is == null) {

            throw new CertificateException("input stream is null");

        }

        try {

            if (is.markSupported() == false) {

                // Copy the entire input stream into an InputStream that does

                // support mark

                is = new ByteArrayInputStream(readAllBytes(is));

            };

            PKCS7 pkcs7 = new PKCS7(is);

            X509Certificate[] certArray = pkcs7.getCertificates();

            // certs are optional in PKCS #7

            if (certArray != null) {

                certList = Arrays.asList(certArray);

            } else {

                // no certs provided

                certList = new ArrayList<X509Certificate>(0);

            }

        } catch (IOException ioe) {

            throw new CertificateException("IOException parsing PKCS7 data: " +

                                        ioe);

        }

        // Assumes that the resulting List is thread-safe. This is true

        // because we ensure that it cannot be modified after construction

        // and the methods in the Sun JDK 1.4 implementation of ArrayList that

        // allow read-only access are thread-safe.

        return Collections.unmodifiableList(certList);

    }

    /*

     * Reads the entire contents of an InputStream into a byte array.

     *

     * @param is the InputStream to read from

     * @return the bytes read from the InputStream

     */

    private static byte[] readAllBytes(InputStream is) throws IOException {

        byte[] buffer = new byte[8192];

        ByteArrayOutputStream baos = new ByteArrayOutputStream(2048);

        int n;

        while ((n = is.read(buffer)) != -1) {

            baos.write(buffer, 0, n);

        }

        return baos.toByteArray();

    }

    /**

     * Returns the encoded form of this certification path, using the

     * default encoding.

     *

     * @return the encoded bytes

     * @exception CertificateEncodingException if an encoding error occurs

     */

    public byte[] getEncoded() throws CertificateEncodingException {

        // @@@ Should cache the encoded form

        return encodePKIPATH();

    }

    /**

     * Encode the CertPath using PKIPATH format.

     *

     * @return a byte array containing the binary encoding of the PkiPath object

     * @exception CertificateEncodingException if an exception occurs

     */

    private byte[] encodePKIPATH() throws CertificateEncodingException {

        ListIterator<X509Certificate> li = certs.listIterator(certs.size());

        try {

            DerOutputStream bytes = new DerOutputStream();

            // encode certs in reverse order (trust anchor to target)

            // according to PkiPath format

            while (li.hasPrevious()) {

                X509Certificate cert = li.previous();

                // check for duplicate cert

                if (certs.lastIndexOf(cert) != certs.indexOf(cert)) {

                    throw new CertificateEncodingException

                        ("Duplicate Certificate");

                }

                // get encoded certificates

                byte[] encoded = cert.getEncoded();

                bytes.write(encoded);

            }

            // Wrap the data in a SEQUENCE

            DerOutputStream derout = new DerOutputStream();

            derout.write(DerValue.tag_SequenceOf, bytes);

            return derout.toByteArray();

        } catch (IOException ioe) {

           CertificateEncodingException ce = new CertificateEncodingException

                ("IOException encoding PkiPath data: " + ioe);

           ce.initCause(ioe);

           throw ce;

        }

    }

    /**

     * Encode the CertPath using PKCS#7 format.

     *

     * @return a byte array containing the binary encoding of the PKCS#7 object

     * @exception CertificateEncodingException if an exception occurs

     */

    private byte[] encodePKCS7() throws CertificateEncodingException {

        PKCS7 p7 = new PKCS7(new AlgorithmId[0],

                             new ContentInfo(ContentInfo.DATA_OID, null),

                             certs.toArray(new X509Certificate[certs.size()]),

                             new SignerInfo[0]);

        DerOutputStream derout = new DerOutputStream();

        try {

            p7.encodeSignedData(derout);

        } catch (IOException ioe) {

            throw new CertificateEncodingException(ioe.getMessage());

        }

        return derout.toByteArray();

    }

    /**

     * Returns the encoded form of this certification path, using the

     * specified encoding.

     *

     * @param encoding the name of the encoding to use

     * @return the encoded bytes

     * @exception CertificateEncodingException if an encoding error occurs or

     *   the encoding requested is not supported

     */

    public byte[] getEncoded(String encoding)

            throws CertificateEncodingException {

        if (PKIPATH_ENCODING.equals(encoding)) {

            return encodePKIPATH();

        } else if (PKCS7_ENCODING.equals(encoding)) {

            return encodePKCS7();

        } else {

            throw new CertificateEncodingException("unsupported encoding");

        }

    }

    /**

     * Returns the encodings supported by this certification path, with the

     * default encoding first.

     *

     * @return an <code>Iterator</code> over the names of the supported

     *         encodings (as Strings)

     */

    public static Iterator<String> getEncodingsStatic() {

        return encodingList.iterator();

    }

    /**

     * Returns an iteration of the encodings supported by this certification

     * path, with the default encoding first.

     * <p>

     * Attempts to modify the returned <code>Iterator</code> via its

     * <code>remove</code> method result in an

     * <code>UnsupportedOperationException</code>.

     *

     * @return an <code>Iterator</code> over the names of the supported

     *         encodings (as Strings)

     */

    public Iterator<String> getEncodings() {

        return getEncodingsStatic();

    }

    /**

     * Returns the list of certificates in this certification path.

     * The <code>List</code> returned must be immutable and thread-safe.

     *

     * @return an immutable <code>List</code> of <code>X509Certificate</code>s

     *         (may be empty, but not null)

     */

    public List<X509Certificate> getCertificates() {

        return certs;

    }

}