PEMReader.java

/****************************************************************************
 * Copyright (c) 1998-2009 AOL LLC. 
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 ****************************************************************************
 * 
 * @author:     zhang
 * @version:    $Revision: 73016 $
 * @created:    Apr 24, 2009
 *
 * Description: A class to decode PEM files
 * 
 ****************************************************************************/
package net.oauth.signature.pem;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import net.oauth.signature.OAuthSignatureMethod;

/**
 * This class convert PEM into byte array. The begin marker
 * is saved and it can be used to determine the type of the
 * PEM file.
 * 
 * @author zhang
 */
public class PEMReader {

    // Begin markers for all supported PEM files 
    public static final String PRIVATE_PKCS1_MARKER =
        "-----BEGIN RSA PRIVATE KEY-----";
    public static final String PRIVATE_PKCS8_MARKER = 
        "-----BEGIN PRIVATE KEY-----";
    public static final String CERTIFICATE_X509_MARKER =
        "-----BEGIN CERTIFICATE-----";
    public static final String PUBLIC_X509_MARKER = 
        "-----BEGIN PUBLIC KEY-----";

    private static final String BEGIN_MARKER = "-----BEGIN ";

    private InputStream stream;
    private byte[] derBytes;
    private String beginMarker;

    public PEMReader(InputStream inStream) throws IOException {
        stream = inStream;
        readFile();
    }

    public PEMReader(byte[] buffer) throws IOException {
        this(new ByteArrayInputStream(buffer));
    }

    public PEMReader(String fileName) throws IOException {
        this(new FileInputStream(fileName));
    }

    public byte[] getDerBytes() {
        return derBytes;
    }

    public String getBeginMarker() {
        return beginMarker;
    }

    /**
     * Read the PEM file and save the DER encoded octet
     * stream and begin marker.
     * 
     * @throws IOException
     */
    protected void readFile() throws IOException {

        String  line;
        BufferedReader reader = new BufferedReader(
                new InputStreamReader(stream));
        try {
            while ((line = reader.readLine()) != null)
            {
                if (line.indexOf(BEGIN_MARKER) != -1)
                {
                    beginMarker = line.trim();
                    String endMarker = beginMarker.replace("BEGIN", "END");
                    derBytes = readBytes(reader, endMarker);
                    return;
                }
            }	        
            throw new IOException("Invalid PEM file: no begin marker");
        } finally {
            reader.close();
        }
    }


    /**
     * Read the lines between BEGIN and END marker and convert
     * the Base64 encoded content into binary byte array.
     * 
     * @return DER encoded octet stream
     * @throws IOException
     */
    private byte[] readBytes(BufferedReader reader, String endMarker) throws IOException
    {
        String          line = null;
        StringBuffer    buf = new StringBuffer();

        while ((line = reader.readLine()) != null)
        {
            if (line.indexOf(endMarker) != -1) {

                return OAuthSignatureMethod.decodeBase64(buf.toString());
            }

            buf.append(line.trim());        
        }

        throw new IOException("Invalid PEM file: No end marker");
    }    
}