itextpdf-master/itext/src/main/java/com/itextpdf/text/pdf/security/LtvTimestamp.java
/*
 *
 * This file is part of the iText (R) project.
    Copyright (c) 1998-2022 iText Group NV
 * Authors: Bruno Lowagie, Paulo Soares, et al.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
 * OF THIRD PARTY RIGHTS
 *
 * 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 Affero General Public License for more details.
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, see http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License,
 * a covered work must retain the producer line in every PDF that is created
 * or manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the iText software without
 * disclosing the source code of your own applications.
 * These activities include: offering paid services to customers as an ASP,
 * serving PDFs on the fly in a web application, shipping iText with a closed
 * source product.
 *
 * For more information, please contact iText Software Corp. at this
 * address: sales@itextpdf.com
 */
package com.itextpdf.text.pdf.security;

import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.PdfDeveloperExtension;
import com.itextpdf.text.pdf.PdfDictionary;
import com.itextpdf.text.pdf.PdfName;
import com.itextpdf.text.pdf.PdfSignature;
import com.itextpdf.text.pdf.PdfSignatureAppearance;
import com.itextpdf.text.pdf.PdfString;

import java.io.IOException;
import java.io.InputStream;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.util.HashMap;

/**
 * PAdES-LTV Timestamp
 * @author Paulo Soares
 */
public class LtvTimestamp {
    /**
     * Signs a document with a PAdES-LTV Timestamp. The document is closed at the end.
     * @param sap the signature appearance
     * @param tsa the timestamp generator
     * @param signatureName the signature name or null to have a name generated
     * automatically
     * @throws DocumentException 
     * @throws IOException 
     * @throws GeneralSecurityException
     */
    public static void timestamp(PdfSignatureAppearance sap, TSAClient tsa, String signatureName) throws IOException, DocumentException, GeneralSecurityException {
        int contentEstimated = tsa.getTokenSizeEstimate();
        sap.addDeveloperExtension(PdfDeveloperExtension.ESIC_1_7_EXTENSIONLEVEL5);
        sap.setVisibleSignature(new Rectangle(0,0,0,0), 1, signatureName);

        PdfSignature dic = new PdfSignature(PdfName.ADOBE_PPKLITE, PdfName.ETSI_RFC3161);
        dic.put(PdfName.TYPE, PdfName.DOCTIMESTAMP);
        sap.setCryptoDictionary(dic);

        HashMap<PdfName,Integer> exc = new HashMap<PdfName,Integer>();
        exc.put(PdfName.CONTENTS, new Integer(contentEstimated * 2 + 2));
        sap.preClose(exc);
        InputStream data = sap.getRangeStream();
        MessageDigest messageDigest = tsa.getMessageDigest();
        byte[] buf = new byte[4096];
        int n;
        while ((n = data.read(buf)) > 0) {
            messageDigest.update(buf, 0, n);
        }
        byte[] tsImprint = messageDigest.digest();
        byte[] tsToken;
        try {
        	tsToken = tsa.getTimeStampToken(tsImprint);
        }
        catch(Exception e) {
        	throw new GeneralSecurityException(e);
        }

        if (contentEstimated + 2 < tsToken.length)
            throw new IOException("Not enough space");

        byte[] paddedSig = new byte[contentEstimated];
        System.arraycopy(tsToken, 0, paddedSig, 0, tsToken.length);

        PdfDictionary dic2 = new PdfDictionary();
        dic2.put(PdfName.CONTENTS, new PdfString(paddedSig).setHexWriting(true));
        sap.close(dic2);
    }
}
