Java tutorial
/* Copyright (C) 2010 Steffen Dienst This program 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 2 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 General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.security.InvalidKeyException; import java.security.KeyStoreException; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.security.PrivateKey; import java.security.Security; import java.security.Signature; import java.security.SignatureException; import java.security.cert.CRL; import java.security.cert.X509Certificate; import java.util.Calendar; import java.util.HashMap; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.bouncycastle.jce.provider.BouncyCastleProvider; import com.lowagie.text.DocumentException; import com.lowagie.text.Rectangle; import com.lowagie.text.pdf.PdfDate; import com.lowagie.text.pdf.PdfDictionary; import com.lowagie.text.pdf.PdfLiteral; import com.lowagie.text.pdf.PdfName; import com.lowagie.text.pdf.PdfPKCS7; import com.lowagie.text.pdf.PdfReader; import com.lowagie.text.pdf.PdfSigGenericPKCS; import com.lowagie.text.pdf.PdfSignatureAppearance; import com.lowagie.text.pdf.PdfStamper; import com.lowagie.text.pdf.PdfString; import com.lowagie.text.pdf.TSAClientBouncyCastle; /** * Sign pdfs using a cryptographic key. Also add a timestamp that proves reliably that the document was signed at this * specific point in time. * * @author Steffen Dienst * */ public class SignPdf { protected final static Log log = LogFactory.getLog(SignPdf.class); public static void main(final String[] args) throws IOException, SignatureException, KeyStoreException, DocumentException { final SignatureInfos infos = new SignatureInfos(); infos.setKeyAlias("duke2"); infos.setCertificateChainAlias("duke2"); infos.setKeystorePassword("a123456"); infos.setPrivateKeyPassword("a123456"); signAndTimestamp(new FileInputStream(new File("pfad.pdf")), new FileOutputStream(new File("pfad2.pdf")), infos); } /** * Add a signature and a cryptographic timestamp to a pdf document. See www.ietf.org/rfc/rfc3161.txt. Proves that this * pdf had the current content at the current point in time. * * @param originalPdf * @param targetPdf * @param infos * @throws SignatureException * @throws KeyStoreException * @throws IOException * @throws DocumentException */ public static void signAndTimestamp(final InputStream originalPdf, final OutputStream targetPdf, final SignatureInfos infos) throws SignatureException, KeyStoreException, IOException, DocumentException { signAndTimestamp(originalPdf, targetPdf, infos.getPrivateKey(), infos.getCertificateChain(), null, infos.getTimestampServerUrl(), infos.getSignatureReason(), infos.getSignatureLocation(), infos.getSignatureContact()); } private static void AsignAndTimestamp(final File fIn, final File fOut) throws SignatureException, KeyStoreException, FileNotFoundException, IOException, DocumentException { signAndTimestamp(new FileInputStream(fIn), new FileOutputStream(fOut), new SignatureInfos()); } /** * Add a signature and a cryptographic timestamp to a pdf document. See www.ietf.org/rfc/rfc3161.txt. Proves that this * pdf had the current content at the current point in time. * * @param originalPdf * @param targetPdf * @param pk * @param certChain * @param revoked * @param tsaAddress * address of a rfc 3161 compatible timestamp server * @param reason * reason for the signature * @param location * location of signing * @param contact * emailaddress of the person who is signing * @throws IOException * @throws DocumentException * @throws SignatureException */ public static void signAndTimestamp(final InputStream originalPdf, final OutputStream targetPdf, final PrivateKey pk, final X509Certificate[] certChain, final CRL[] revoked, final String tsaAddress, final String reason, final String location, final String contact) throws IOException, DocumentException, SignatureException { // only an estimate, depends on the certificates returned by the TSA final int timestampSize = 4400; Security.addProvider(new BouncyCastleProvider()); final PdfReader reader = new PdfReader(originalPdf); final PdfStamper stamper = PdfStamper.createSignature(reader, targetPdf, '\0'); final PdfSignatureAppearance sap = stamper.getSignatureAppearance(); // comment next lines to have an invisible signature Rectangle cropBox = reader.getCropBox(1); float width = 50; float height = 50; Rectangle rectangle = new Rectangle(cropBox.getRight(width) - 20, cropBox.getTop(height) - 20, cropBox.getRight() - 20, cropBox.getTop() - 20); sap.setVisibleSignature(rectangle, 1, null); //sap.setVisibleSignature(new Rectangle(450, 650, 500, 700), 1, null); sap.setLayer2Text(""); final PdfSigGenericPKCS sig = new PdfSigGenericPKCS.PPKMS("BC"); final HashMap<PdfName, Integer> exclusionSizes = new HashMap<PdfName, Integer>(); // some informational fields sig.setReason(reason); sig.setLocation(location); sig.setContact(contact); sig.setName(PdfPKCS7.getSubjectFields(certChain[0]).getField("CN")); sig.setDate(new PdfDate(Calendar.getInstance())); // signing stuff final byte[] digest = new byte[256]; final byte[] rsaData = new byte[20]; sig.setExternalDigest(digest, rsaData, "RSA"); sig.setSignInfo(pk, certChain, revoked); final PdfString contents = (PdfString) sig.get(PdfName.CONTENTS); // *2 to get hex size, +2 for delimiters PdfLiteral contentsLit = new PdfLiteral((contents.toString().length() + timestampSize) * 2 + 2); exclusionSizes.put(PdfName.CONTENTS, new Integer(contentsLit.getPosLength())); sig.put(PdfName.CONTENTS, contentsLit); // certification; will display dialog or blue bar in Acrobat Reader sap.setCertificationLevel(PdfSignatureAppearance.CERTIFIED_NO_CHANGES_ALLOWED); // process all the information set above sap.setCryptoDictionary(sig); sap.preClose(exclusionSizes); // calculate digest (hash) try { final MessageDigest messageDigest = MessageDigest.getInstance("SHA1"); final byte[] buf = new byte[8192]; int n; final InputStream inp = sap.getRangeStream(); while ((n = inp.read(buf)) != -1) { messageDigest.update(buf, 0, n); } final byte[] hash = messageDigest.digest(); // make signature (SHA1 the hash, prepend algorithm ID, pad, and encrypt with RSA) final Signature sign = Signature.getInstance("SHA1withRSA"); sign.initSign(pk); sign.update(hash); final byte[] signature = sign.sign(); // prepare the location of the signature in the target PDF contentsLit = (PdfLiteral) sig.get(PdfName.CONTENTS); final byte[] outc = new byte[(contentsLit.getPosLength() - 2) / 2]; final PdfPKCS7 pkcs7 = sig.getSigner(); pkcs7.setExternalDigest(signature, hash, "RSA"); final PdfDictionary dic = new PdfDictionary(); byte[] ssig = pkcs7.getEncodedPKCS7(); try { // try to retrieve cryptographic timestamp from configured tsa server ssig = pkcs7.getEncodedPKCS7(null, null, new TSAClientBouncyCastle(tsaAddress), null); } catch (final RuntimeException e) { log.error("Could not retrieve timestamp from server.", e); } System.arraycopy(ssig, 0, outc, 0, ssig.length); // add the timestamped signature dic.put(PdfName.CONTENTS, new PdfString(outc).setHexWriting(true)); // finish up sap.close(dic); } catch (final InvalidKeyException e) { throw new RuntimeException("Internal implementation error! No such signature type.", e); } catch (final NoSuchAlgorithmException e) { throw new RuntimeException("Internal implementation error! No such algorithm type.", e); } } }