com.esec.signature.MakeExternalSignature Maven / Gradle / Ivy

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This library is used to sign PDFs.
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package com.esec.signature;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.GeneralSecurityException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.Certificate;
import java.util.Calendar;
import java.util.HashMap;

import com.esec.text.DocumentException;
import com.esec.text.pdf.PdfDate;
import com.esec.text.pdf.PdfDictionary;
import com.esec.text.pdf.PdfName;
import com.esec.text.pdf.PdfPKCS7;
import com.esec.text.pdf.PdfSignature;
import com.esec.text.pdf.PdfSignatureAppearance;
import com.esec.text.pdf.PdfString;

/**
 * Class that signs your PDF.
 * 
 */
public class MakeExternalSignature {

	private static final int ESTIMATED_SIZE = 8192;
	
	public static InputStream getData(PdfSignatureAppearance sap, Certificate signerCert) throws IOException, DocumentException, GeneralSecurityException {
		sap.setCertificate(signerCert);
		PdfSignature dic = new PdfSignature(PdfName.ADOBE_PPKLITE, PdfName.ADBE_PKCS7_DETACHED);
		dic.setReason(sap.getReason());
		dic.setLocation(sap.getLocation());
		dic.setContact(sap.getContact());
		dic.setDate(new PdfDate(sap.getSignDate())); // time-stamp will over-rule this
		sap.setCryptoDictionary(dic);

		HashMap exc = new HashMap();
		exc.put(PdfName.CONTENTS, new Integer(ESTIMATED_SIZE * 2 + 2));
		sap.preCloseWithExternalSignature(exc);

		return sap.getRangeStream();
	}

	public static void attachSignature(PdfSignatureAppearance sap, Certificate signerCert, byte[] encodedSig) throws IOException, DocumentException, GeneralSecurityException {
        sap.setCertificate(signerCert);
        PdfSignature dic = new PdfSignature(PdfName.ADOBE_PPKLITE, PdfName.ADBE_PKCS7_DETACHED);
        dic.setReason(sap.getReason());
        dic.setLocation(sap.getLocation());
        dic.setContact(sap.getContact());
        dic.setDate(new PdfDate(sap.getSignDate())); // time-stamp will over-rule this
        sap.setCryptoDictionary(dic);

        HashMap exc = new HashMap();
        exc.put(PdfName.CONTENTS, new Integer(ESTIMATED_SIZE * 2 + 2));
        sap.preCloseWithExternalSignature(exc);

//        InputStream data = sap.getRangeStream();

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

        byte[] paddedSig = new byte[ESTIMATED_SIZE];
        System.arraycopy(encodedSig, 0, paddedSig, 0, encodedSig.length);

        PdfDictionary dic2 = new PdfDictionary();
        dic2.put(PdfName.CONTENTS, new PdfString(paddedSig).setHexWriting(true));
        sap.close(dic2);
	}
	
	/**
	 * Signs the document using the detached mode, CMS or CAdES equivalent.
	 *  
	 * @param sap  the PdfSignatureAppearance
	 * @param externalDigest the interface providing the actual signing
	 * @param externalSignature
	 * @param chain the certificate chain
	 * @throws IOException
	 * @throws DocumentException
	 * @throws GeneralSecurityException
	 */
    public static void signDetached(PdfSignatureAppearance sap, ExternalDigest externalDigest, ExternalSignature externalSignature, Certificate[] chain) throws IOException, DocumentException, GeneralSecurityException {
        sap.setCertificate(chain[0]);
        PdfSignature dic = new PdfSignature(PdfName.ADOBE_PPKLITE, PdfName.ADBE_PKCS7_DETACHED);
        dic.setReason(sap.getReason());
        dic.setLocation(sap.getLocation());
        dic.setContact(sap.getContact());
        dic.setDate(new PdfDate(sap.getSignDate())); // time-stamp will over-rule this
        sap.setCryptoDictionary(dic);

        HashMap exc = new HashMap();
        exc.put(PdfName.CONTENTS, new Integer(ESTIMATED_SIZE * 2 + 2));
        sap.preCloseWithExternalSignature(exc);

        String hashAlgorithm = externalSignature.getHashAlgorithm();
        PdfPKCS7 sgn = new PdfPKCS7(null, chain, null, hashAlgorithm, null, false);
        InputStream data = sap.getRangeStream();
        
        byte hash[] = DigestAlgorithms.digest(data, externalDigest.getMessageDigest(hashAlgorithm));
        Calendar cal = Calendar.getInstance();
        byte[] sh = sgn.getAuthenticatedAttributeBytes(hash, cal, null);
        byte[] extSignature = externalSignature.sign(new ByteArrayInputStream(sh));
        sgn.setExternalDigest(extSignature, null, externalSignature.getEncryptionAlgorithm());

        byte[] encodedSig = sgn.getEncodedPKCS7(hash, cal);

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

        byte[] paddedSig = new byte[ESTIMATED_SIZE];
        System.arraycopy(encodedSig, 0, paddedSig, 0, encodedSig.length);

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