EncFSConfigWriter.java

/*
 * EncFS Java Library
 * Copyright (C) 2011-2012 Mark R. Pariente
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 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 Lesser General Public License for more details.
 */
package org.mrpdaemon.sec.encfs;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Properties;


/**
 * Writer methods that write an EncFSConfig into a file
 */
public final class EncFSConfigWriter {

    // Version to use if the properties file can't be read
    private static final String ENCFS_JAVA_LIB_VERSION_DEV = "JFileSync3";

    // Property file
    private static final String ENCFS_JAVA_LIB_PROPERTY_FILE = "library.properties";

    // Property key for version
    private static final String ENCFS_JAVA_LIB_VERSION_KEY = "library.version";


    private EncFSConfigWriter() {
    }


    // Retrieve library version

    private static String getLibraryVersion() {
        Properties prop = new Properties();
        InputStream in = EncFSConfigWriter.class
                .getResourceAsStream(ENCFS_JAVA_LIB_PROPERTY_FILE);

        if (in!=null) {
            try {
                prop.load(in);
                String version = prop.getProperty(ENCFS_JAVA_LIB_VERSION_KEY);
                if (version!=null) {
                    return version;
                } else {
                    return ENCFS_JAVA_LIB_VERSION_DEV;
                }
            } catch (IOException e) {
                return ENCFS_JAVA_LIB_VERSION_DEV;
            }
        } else {
            return ENCFS_JAVA_LIB_VERSION_DEV;
        }
    }


    // Create config file contents from a given EncFSConfig / password

    private static String createConfigFileContents(EncFSConfig config) {
        // TODO: This implementation is pretty horrible, but it works :)
        String result = "";

        result += "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n";
        result += "<!DOCTYPE boost_serialization>\n";
        result += "<boost_serialization signature=\"serialization::archive\" version=\"9\">\n";
        result += " <cfg class_id=\"0\" tracking_level=\"0\" version=\"20\">\n";
        result += "\t<version>20100713</version>\n";
        result += "\t<creator>encfs-java "+getLibraryVersion()
                +"</creator>\n";
        result += "\t<cipherAlg class_id=\"1\" tracking_level=\"0\" version=\"0\">\n";
        result += "\t\t<name>ssl/aes</name>\n";
        result += "\t\t<major>3</major>\n";
        result += "\t\t<minor>0</minor>\n";
        result += "\t</cipherAlg>\n";

        result += "\t<nameAlg>\n";

        EncFSFilenameEncryptionAlgorithm algorithm = config
                .getFilenameAlgorithm();
        result += "\t\t<name>"+algorithm.getIdentifier()+"</name>\n";
        result += "\t\t<major>"+algorithm.getMajor()+"</major>\n";
        result += "\t\t<minor>"+algorithm.getMinor()+"</minor>\n";

        result += "\t</nameAlg>\n";

        result += "\t<keySize>"
                +Integer.toString(config.getVolumeKeySizeInBits())
                +"</keySize>\n";

        result += "\t<blockSize>"
                +Integer.toString(config.getEncryptedFileBlockSizeInBytes())
                +"</blockSize>\n";

        result += "\t<uniqueIV>"+(config.isUseUniqueIV() ? "1" : "0")
                +"</uniqueIV>\n";

        result += "\t<chainedNameIV>"+(config.isChainedNameIV() ? "1" : "0")
                +"</chainedNameIV>\n";

        result += "\t<externalIVChaining>"
                +(config.isSupportedExternalIVChaining() ? "1" : "0")
                +"</externalIVChaining>\n";

        result += "\t<blockMACBytes>"
                +Integer
                .toString(config.getNumberOfMACBytesForEachFileBlock())
                +"</blockMACBytes>\n";
        result += "\t<blockMACRandBytes>"
                +Integer.toString(config
                        .getNumberOfRandomBytesInEachMACHeader())
                +"</blockMACRandBytes>\n";

        result += "\t<allowHoles>"
                +(config.isHolesAllowedInFiles() ? "1" : "0")
                +"</allowHoles>\n";

        result += "\t<encodedKeySize>"
                +Integer.toString(config.getEncodedKeyLengthInBytes())
                +"</encodedKeySize>\n";
        result += "\t<encodedKeyData>"+config.getBase64EncodedVolumeKey()
                +"\n</encodedKeyData>\n";

        result += "\t<saltLen>"+Integer.toString(config.getSaltLengthBytes())
                +"</saltLen>\n";
        result += "\t<saltData>"+config.getBase64Salt()+"\n</saltData>\n";

        result += "\t<kdfIterations>"
                +Integer.toString(config
                        .getIterationForPasswordKeyDerivationCount())
                +"</kdfIterations>\n";

        // XXX: We don't support custom KDF durations
        result += "\t<desiredKDFDuration>500</desiredKDFDuration>\n";

        result += "  </cfg>\n";
        result += "</boost_serialization>\n";

        return result;
    }


    /**
     * Create a configuration file from the given EncFSConfig and write it to
     * the root directory of the given EncFSFileProvider
     */
    public static void writeConfig(EncFSFileProvider fileProvider,
            EncFSConfig config) throws EncFSUnsupportedException, IOException {
        String configFileName = fileProvider.getFilesystemRootPath()
                +EncFSVolume.CONFIG_FILE_NAME;

        if (fileProvider.exists(configFileName)) {
            throw new EncFSUnsupportedException("Config file already exists");
        }

        String configFileContents = createConfigFileContents(config);

        OutputStream os = fileProvider.openOutputStream(configFileName,
                configFileContents.length());

        os.write(configFileContents.getBytes());
        os.close();
    }

}