java - How to add custom field in iText signature stamp?

Question

I have a simple signature method to sign PDF documents working fine, it signs the documents with the default stamp that shows Name, Location, Date and Reason.

Now my manager asked me if it is possible to add one more field on it. Let's suppose it is an "Email" field as I haven't been told exactly what they want.

I tried searching and apply somethings I found but nothing has worked.

Also, I was asked if it is possible to remove/hide the label of those 4 default fields (Date, Reason, etc...) and I couldn't manage doing it neither find anything about it, I don't know if it can be really customized.

Here I will show how she signature process are working. In the middel there is some code I found on iText site and tried to use to add the "new field" but without any result different from the default stamp been showed.

public String signPdfFirstTime(String src, String dest, PrivateKey pk, Certificate[] chain, String providerName, String conteudoBase64, X509Certificate cert) throws IOException, DocumentException, GeneralSecurityException {

    byte[] content = Base64.decode(conteudoBase64);

    FileOutputStream fos = new FileOutputStream(path + File.separator + src);
    fos.write(content );
    fos.close();

    File f = new File(path + File.separator + src);

    FileInputStream in = new FileInputStream(f);

    PdfReader reader = new PdfReader(in);

    FileOutputStream os = new FileOutputStream(path + File.separator + dest);
    PdfStamper stamper = PdfStamper.createSignature(reader, os, '');
    // Creating the appearance
    PdfSignatureAppearance appearance = stamper.getSignatureAppearance();
    appearance.setReason("SOME REASON");
    appearance.setLocation("SOMEWHERE");
    //  appearance.getAppearance().curveFromTo(98, 120, 46, 94);
    Rectangle rectangle = new Rectangle(0, 0, 500, 70);

    appearance.setVisibleSignature(rectangle, 1, "SIGNATURE");

    //Here I trid to add fields to the stamp
    //NOT WORKING AS I EXPECTED...
    PdfWriter writer = stamper.getWriter();
    PdfFormField field = PdfFormField.createEmpty(writer);
    field.setFieldName("TEST 1111");
    TextField name = new TextField(writer,rectangle, "TEST 2222");
    PdfFormField personal_name = name.getTextField();
    field.addKid(personal_name);
    TextField password = new TextField(writer, rectangle, "password");
    PdfFormField personal_password = password.getTextField();
    field.addKid(personal_password);
    stamper.addAnnotation(field, 1);

    appearance.setCertificate(cert);
    // Creating the signature
    ExternalSignature pks = new PrivateKeySignature(pk, DigestAlgorithms.SHA256, providerName);
    ExternalDigest digest = new BouncyCastleDigest();
    List<CrlClient> crlList = new ArrayList<CrlClient>();
    crlList.add(new CrlClientOnline());

    LtvVerification v = stamper.getLtvVerification();

    OcspClient ocspClient = new OcspClientBouncyCastle();

    String url = CertificateUtil.getCRLURL(cert);
    CertificateFactory cf = CertificateFactory.getInstance("X.509");

    X509CRL crl = (X509CRL) cf.generateCRL(new URL(url).openStream());
    System.out.println("CRL valid until: " + crl.getNextUpdate());
    System.out.println("Certificate revoked: " + crl.isRevoked(chain[0]));

    if (crl.isRevoked(chain[0])) {

        throw new GeneralSecurityException("CERTIFICADO REVOGADO!");
    }
    else {
        MakeSignature.processCrl(cert, crlList);

        MakeSignature.signDetached(appearance, digest, pks, chain, null, null, null, 0, CryptoStandard.CMS);
        os.close();
        byte[] b = this.read(f);
        return Base64.encodeBytes(b);
    }
}

Answer 1

The PdfSignatureAppearance class allows you to set the text of the automatically generated appearance by

/**
 * Sets the signature text identifying the signer.
 * @param text the signature text identifying the signer. If <CODE>null</CODE> or not set
 * a standard description will be used
 */
public void setLayer2Text(String text)

The font used can be set using

/**
 * Sets the n2 and n4 layer font. If the font size is zero, auto-fit will be used.
 * @param layer2Font the n2 and n4 font
 */
public void setLayer2Font(Font layer2Font)

If you want to control the appearance even more, you can retrieve the layer 2 template and design any content on it you want.

/**
 * Gets a template layer to create a signature appearance. The layers can go from 0 to 4,
 * but only layer 0 and 2 will be used if acro6Layers is true.
 * <p>
 * Consult <A HREF="http://partners.adobe.com/asn/developer/pdfs/tn/PPKAppearances.pdf">PPKAppearances.pdf</A>
 * for further details.
 * @param layer the layer
 * @return a template
 */
public PdfTemplate getLayer(int layer)