be.fedict.eid.dss.spi.utils.TimeStampDigestInput.java Source code

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Here is the source code for be.fedict.eid.dss.spi.utils.TimeStampDigestInput.java

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/*
 * eID Digital Signature Service Project.
 * Copyright (C) 2010 FedICT.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License version
 * 3.0 as published by the Free Software Foundation.
 *
 * This software 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.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, see
 * http://www.gnu.org/licenses/.
 */

package be.fedict.eid.dss.spi.utils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.LinkedList;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.xml.security.c14n.CanonicalizationException;
import org.apache.xml.security.c14n.Canonicalizer;
import org.apache.xml.security.c14n.InvalidCanonicalizerException;
import org.w3c.dom.Node;

/**
 * Helper class to build inputs for time-stamps. The digests for time-stamps are
 * usually calculated over a concatenations of byte-streams, resulting from
 * nodes and/or processed {@code Reference}s, with the proper canonicalization
 * if needed. This class provides methods to build a sequential input by adding
 * DOM {@code Node}s.
 * 
 * @author Frank Cornelis
 */
public class TimeStampDigestInput {

    private static final Log LOG = LogFactory.getLog(TimeStampDigestInput.class);

    private final String canonMethodUri;
    private final List<Node> nodes;

    static {
        org.apache.xml.security.Init.init();
    }

    /**
     * @param canonMethodUri
     *            the canonicalization method to be used, if needed
     * @throws IllegalArgumentException
     *             if {@code canonMethodUri} is {@code null}
     */
    public TimeStampDigestInput(String canonMethodUri) {

        LOG.debug("canonMethodUri: " + canonMethodUri);

        if (null == canonMethodUri) {
            throw new IllegalArgumentException("c14n algo URI is null");
        }

        this.canonMethodUri = canonMethodUri;
        this.nodes = new LinkedList<Node>();
    }

    /**
     * Adds a {@code Node} to the input. The node is canonicalized.
     * 
     * @param n
     *            the node to be added
     * @throws IllegalArgumentException
     *             if {@code n} is {@code null}
     */
    public void addNode(Node n) {
        if (null == n) {
            throw new IllegalArgumentException("DOM node is null");
        }
        LOG.debug("adding digest node: " + n.getLocalName());
        this.nodes.add(n);
    }

    /**
     * Gets the octet-stream corresponding to the actual state of the input.
     * 
     * @return the octet-stream (always a new instance)
     */
    public byte[] getBytes() {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try {
            for (Node node : this.nodes) {
                /*
                 * We have to re-init the canonicalizer each time, else the
                 * namespaces will be cached and will eventually be missing from
                 * the canonicalized nodes.
                 */
                Canonicalizer c14n;
                try {
                    c14n = Canonicalizer.getInstance(this.canonMethodUri);
                } catch (InvalidCanonicalizerException e) {
                    throw new RuntimeException("c14n algo error: " + e.getMessage(), e);
                }
                baos.write(c14n.canonicalizeSubtree(node));
            }
        } catch (CanonicalizationException e) {
            throw new RuntimeException("c14n error: " + e.getMessage(), e);
        } catch (IOException e) {
            throw new RuntimeException("I/O error: " + e.getMessage(), e);
        }
        return baos.toByteArray();
    }
}