/*
 *  SSHTools - Java SSH2 API
 *
 *  Copyright (C) 2002-2003 Lee David Painter and Contributors.
 *
 *  Contributions made by:
 *
 *  Brett Smith
 *  Richard Pernavas
 *  Erwin Bolwidt
 *
 *  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; either version 2
 *  of the License, or (at your option) any later version.
 *
 *  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.
 */
package com.sshtools.j2ssh.openssh;

import com.sshtools.j2ssh.util.Base64;

import java.io.IOException;
import java.io.LineNumberReader;
import java.io.Reader;

import java.security.GeneralSecurityException;
import java.security.NoSuchAlgorithmException;

import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;


/**
 *
 *
 * @author $author$
 * @version $Revision: 1.13 $
 */
public class PEMReader extends PEM {
    private LineNumberReader reader;
    private String type;
    private Map header;
    private byte[] payload;

    /**
     * Creates a new PEMReader object.
     *
     * @param r
     *
     * @throws IOException
     */
    public PEMReader(Reader r) throws IOException {
        reader = new LineNumberReader(r);
        read();
    }

    private void read() throws IOException {
        String line;

        while ((line = reader.readLine()) != null) {
            if (line.startsWith(PEM_BOUNDARY) && line.endsWith(PEM_BOUNDARY)) {
                if (line.startsWith(PEM_BEGIN)) {
                    type = line.substring(PEM_BEGIN.length(),
                            line.length() - PEM_BOUNDARY.length());

                    break;
                } else {
                    throw new IOException("Invalid PEM boundary at line " +
                        reader.getLineNumber() + ": " + line);
                }
            }
        }

        header = new HashMap();

        while ((line = reader.readLine()) != null) {
            int colon = line.indexOf(':');

            if (colon == -1) {
                break;
            }

            String key = line.substring(0, colon).trim();

            if (line.endsWith("\\")) {
                String v = line.substring(colon + 1, line.length() - 1).trim();

                // multi-line value
                StringBuffer value = new StringBuffer(v);

                while ((line = reader.readLine()) != null) {
                    if (line.endsWith("\\")) {
                        value.append(" ").append(line.substring(0,
                                line.length() - 1).trim());
                    } else {
                        value.append(" ").append(line.trim());

                        break;
                    }
                }
            } else {
                String value = line.substring(colon + 1).trim();
                header.put(key, value);
            }
        }

        // first line that is not part of the header
        // could be an empty line, but if there is no header and the body begins straight after the -----
        // then this line contains data
        if (line == null) {
            throw new IOException(
                "The key format is invalid! OpenSSH formatted keys must begin with -----BEGIN RSA or -----BEGIN DSA");
        }

        StringBuffer body = new StringBuffer(line);

        while ((line = reader.readLine()) != null) {
            if (line.startsWith(PEM_BOUNDARY) && line.endsWith(PEM_BOUNDARY)) {
                if (line.startsWith(PEM_END + type)) {
                    break;
                } else {
                    throw new IOException("Invalid PEM end boundary at line " +
                        reader.getLineNumber() + ": " + line);
                }
            }

            body.append(line);
        }

        payload = Base64.decode(body.toString());
    }

    /**
     *
     *
     * @return
     */
    public Map getHeader() {
        return header;
    }

    /**
     *
     *
     * @return
     */
    public byte[] getPayload() {
        return payload;
    }

    /**
     *
     *
     * @return
     */
    public String getType() {
        return type;
    }

    /**
     *
     *
     * @param passphrase
     *
     * @return
     *
     * @throws GeneralSecurityException
     * @throws NoSuchAlgorithmException
     */
    public byte[] decryptPayload(String passphrase)
        throws GeneralSecurityException {
        String dekInfo = (String) header.get("DEK-Info");

        if (dekInfo != null) {
            int comma = dekInfo.indexOf(',');
            String keyAlgorithm = dekInfo.substring(0, comma);

            if (!"DES-EDE3-CBC".equals(keyAlgorithm)) {
                throw new NoSuchAlgorithmException(
                    "Unsupported passphrase algorithm: " + keyAlgorithm);
            }

            String ivString = dekInfo.substring(comma + 1);
            byte[] iv = new byte[ivString.length() / 2];

            for (int i = 0; i < ivString.length(); i += 2) {
                iv[i / 2] = (byte) Integer.parseInt(ivString.substring(i, i +
                            2), 16);
            }

            Cipher cipher = Cipher.getInstance("DESede/CBC/NoPadding");
            SecretKey key = getKeyFromPassphrase(passphrase, iv, 24);
            cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(iv));

            byte[] plain = new byte[payload.length];
            cipher.update(payload, 0, payload.length, plain, 0);

            return plain;
        } else {
            return payload;
        }
    }
}
