org.kse.utilities.pem.PemUtil.java Source code

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Here is the source code for org.kse.utilities.pem.PemUtil.java

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/*
 * Copyright 2004 - 2013 Wayne Grant
 *           2013 - 2017 Kai Kramer
 *
 * This file is part of KeyStore Explorer.
 *
 * KeyStore Explorer 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 3 of the License, or
 * (at your option) any later version.
 *
 * KeyStore Explorer 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 KeyStore Explorer.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.kse.utilities.pem;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.LineNumberReader;

import org.apache.commons.io.IOUtils;
import org.bouncycastle.util.encoders.Base64;
import org.kse.utilities.io.ReadUtil;

/**
 * Provides utility methods relating to PEM.
 *
 */
public class PemUtil {
    private static final int MAX_PRINTABLE_ENCODING_LINE_LENGTH = 64;

    private PemUtil() {
    }

    /**
     * Encode the supplied information as PEM.
     *
     * @param pemInfo
     *            PEM Information
     * @return PEM encoding
     */
    public static String encode(PemInfo pemInfo) {
        StringBuffer sbPem = new StringBuffer();

        // Ouput header
        sbPem.append("-----BEGIN ");
        sbPem.append(pemInfo.getType());
        sbPem.append("-----");
        sbPem.append("\n");

        // Output any header attributes
        PemAttributes attributes = pemInfo.getAttributes();

        if (attributes != null && attributes.size() > 0) {
            for (PemAttribute attribute : attributes.values()) {
                sbPem.append(attribute);
                sbPem.append('\n');
            }

            // Empty line separator between attributes and content
            sbPem.append('\n');
        }

        // Output content
        String base64 = new String(Base64.encode(pemInfo.getContent()));

        // Limit line lengths
        for (int i = 0; i < base64.length(); i += MAX_PRINTABLE_ENCODING_LINE_LENGTH) {
            int lineLength;

            if (i + MAX_PRINTABLE_ENCODING_LINE_LENGTH > base64.length()) {
                lineLength = base64.length() - i;
            } else {
                lineLength = MAX_PRINTABLE_ENCODING_LINE_LENGTH;
            }

            sbPem.append(base64.substring(i, i + lineLength));
            sbPem.append("\n");
        }

        // Output footer
        sbPem.append("-----END ");
        sbPem.append(pemInfo.getType());
        sbPem.append("-----");
        sbPem.append("\n");

        return sbPem.toString();
    }

    private static String getTypeFromHeader(String header) {
        String type = null;

        if (header.startsWith("-----BEGIN ")) {
            if (header.endsWith("-----")) {
                type = header.substring(11, header.length() - 5);
            }
        }

        return type;
    }

    private static String getTypeFromFooter(String footer) {
        String type = null;

        if (footer.startsWith("-----END ")) {
            if (footer.endsWith("-----")) {
                type = footer.substring(9, footer.length() - 5);
            }
        }

        return type;
    }

    /**
     * Decode the PEM included in the supplied input stream.
     *
     * @param is
     *            Input stream
     * @return PEM information or null if stream does not contain PEM
     * @throws IOException
     *             If an I/O problem occurs
     */
    public static PemInfo decode(InputStream is) throws IOException {
        byte[] streamContents = ReadUtil.readFully(is);

        LineNumberReader lnr = null;

        try {
            lnr = new LineNumberReader(new InputStreamReader(new ByteArrayInputStream(streamContents)));

            String line = lnr.readLine();
            StringBuffer sbBase64 = new StringBuffer();

            if (line != null) {
                line = line.trim();
                String headerType = getTypeFromHeader(line);

                if (headerType != null) {
                    line = lnr.readLine();

                    PemAttributes attributes = null;

                    // Read any header attributes
                    if (line != null && line.contains(": ")) {
                        line = line.trim();

                        attributes = new PemAttributes();

                        while (line != null) {
                            line = line.trim();

                            // Empty line - end of attributes
                            if (line.equals("")) {
                                line = lnr.readLine();
                                break;
                            }

                            // Run out of attributes before blank line - not PEM
                            if (!line.contains(": ")) {
                                return null;
                            }

                            // Parse attribute from line
                            int separator = line.indexOf(':');

                            String attributeName = line.substring(0, separator);
                            String attributeValue = line.substring(separator + 2);

                            attributes.add(new PemAttribute(attributeName, attributeValue));

                            line = lnr.readLine();
                        }
                    }

                    // Read content
                    while (line != null) {
                        line = line.trim();
                        String footerType = getTypeFromFooter(line);

                        if (footerType == null) {
                            sbBase64.append(line);
                        } else {
                            // Header and footer types do not match - not PEM
                            if (!headerType.equals(footerType)) {
                                return null;
                            } else {
                                // Decode base 64 content
                                byte[] content = Base64.decode(sbBase64.toString());

                                return new PemInfo(headerType, attributes, content);
                            }
                        }

                        line = lnr.readLine();
                    }
                }
            }
        } finally {
            IOUtils.closeQuietly(lnr);
        }

        return null; // Not PEM
    }
}