I'm trying to add an empty signature field to an existing digitally signed pdf (certify signature).
I have a workflow where many users will sign the document (approval signature), the document is created with "n" empty signature fields, one for each user, our application first apply a invisible certify signature, then each user can sign the document in respective field, but due to changes unexpected in the workflow, other users might want to sign, so we want to add the respective empty signature field and then apply the signature.
I tried to add the empty field (a table with a cell event) to the certified document but when I want to add it and associate the field, it breaks the signature, I cannot make it work correctly.
Here is the methods used to sign,add signature field, and set the signature field options. I don't know what I'm doing wrong.
public static String sign(SignRequest signRequest, File certificate, File unsignedDocument, File image, File icon)
throws FileNotFoundException, IOException, DocumentException, StreamParsingException, OCSPException,
OperatorException, URISyntaxException, WriterException, GeneralSecurityException, FontFormatException {
SignatureType sigType = Optional
.ofNullable(SignatureType.get(signRequest.getSignatureProperties().getSignatureType()))
.orElse(SignatureType.APPROVAL_SIGNATURE);
File signedDocument = File.createTempFile("signed",".pdf");
char[] pass = signRequest.getKeyStore().getPassword().toCharArray();
// Load certificate chain
BouncyCastleProvider provider = new BouncyCastleProvider();
Security.addProvider(provider);
KeyStore ks = KeyStore.getInstance("PKCS12", provider.getName());
ks.load(new FileInputStream(certificate.getAbsolutePath()), pass);
String alias = getAliasFromKeyStore(ks);
PrivateKey pk = (PrivateKey) ks.getKey(alias, pass);
Certificate[] chain = ks.getCertificateChain(alias);
// Creating the reader and the stamper
PdfReader reader = new PdfReader(FileUtils.openInputStream(unsignedDocument));
FileOutputStream os = new FileOutputStream(signedDocument);
PdfStamper stamper = PdfStamper.createSignature(reader, os, '\0', null, true);
PdfSignatureAppearance appearance = null;
// Certify o approval signature (approval is the default signature type)
switch (sigType) {
case CERTIFY_SIGNATURE:
if (reader.getAcroFields().getSignatureNames().size() <= 0) {
appearance = setSignatureFieldOptions(stamper.getSignatureAppearance(), reader, chain,
signRequest, image, icon, Boolean.TRUE);
} else {
appearance = setSignatureFieldOptions(stamper.getSignatureAppearance(), reader, chain,
signRequest, image, icon, Boolean.FALSE);
}
break;
case APPROVAL_SIGNATURE:
default:
appearance = setSignatureFieldOptions(stamper.getSignatureAppearance(), reader, chain, signRequest,
image, icon, Boolean.FALSE);
break;
}
// Adding LTV (optional)
OcspClient ocspClient = null;
List<CrlClient> crlList = null;
if (signRequest.getSignatureProperties().getLtv() == Boolean.TRUE) {
ocspClient = new OcspClientBouncyCastle(new OCSPVerifier(null, null));
CrlClient crlClient = new CrlClientOnline(chain);
crlList = new ArrayList<CrlClient>();
crlList.add(crlClient);
}
// Adding timestamp (optional)
TSAClient tsaClient = null;
if (signRequest.getTimestamp() != null
&& StringUtils.isNotBlank(signRequest.getTimestamp().getUrl())) {
tsaClient = new TSAClientBouncyCastle(signRequest.getTimestamp().getUrl(),
signRequest.getTimestamp().getUser(), signRequest.getTimestamp().getPassword());
}
// Creating the signature
ExternalSignature pks = new PrivateKeySignature(pk, signtRequest.getSignatureProperties().getAlgorithm(),
provider.getName());
ExternalDigest digest = new BouncyCastleDigest();
MakeSignature
.signDetached(appearance, digest, pks, chain, crlList, ocspClient, tsaClient,
calculateEstimatedSize(chain, ocspClient, tsaClient, crlList, getEstimatedSizeBonus()), CryptoStandard.CMS);
return signedDocument.getAbsolutePath();
}
private static PdfSignatureAppearance setSignatureFieldOptions(PdfSignatureAppearance appearance, PdfReader reader, Certificate[] chain, SignRequest signRequest, File image, File icon, Boolean certifySignature) throws MalformedURLException, IOException, DocumentException {
SignatureProperties sigProperties = signRequest.getSignatureProperties();
SignatureField sigField = sigProperties.getSignatureField();
// Creating the appearance
appearance.setSignatureCreator(Constant.SIGNATURE_CREATOR);
Optional.ofNullable(sigProperties.getReason()).ifPresent(appearance::setReason);
Optional.ofNullable(sigProperties.getLocation()).ifPresent(appearance::setLocation);
if (certifySignature) {
appearance.setCertificationLevel(PdfSignatureAppearance.CERTIFIED_FORM_FILLING_AND_ANNOTATIONS);
} else {
appearance.setCertificationLevel(PdfSignatureAppearance.NOT_CERTIFIED);
}
/**
* Signature Field Name
*/
BoundingBox box = sigProperties.getSignatureField().getBoundingBox();
String fieldName = sigField.getName();
int pageNumber = sigProperties.getSignatureField().getPage();
if (!sigField.isVisible()) {
if (StringUtils.isBlank(sigField.getName())) {
fieldName = generateFieldName();
appearance.setVisibleSignature(new Rectangle(0, 0, 0, 0), pageNumber, fieldName);
} else {
appearance.setVisibleSignature(new Rectangle(0, 0, 0, 0), pageNumber, fieldName);
}
} else {
Font font = FontFactory.getFont(Optional.ofNullable(sigField.getFontName()).orElse(BaseFont.HELVETICA),
Optional.ofNullable(sigField.getFontSize()).orElse(6));
Rectangle rect = null;
FieldPosition fieldPosition = null;
//ADD EMPTY FIELD
if (StringUtils.isBlank(sigField.getName()) && box != null) {
fieldName = generateFieldName();
rect = new Rectangle(box.getLowerLeftX(), box.getLowerLeftY(), box.getLowerLeftX() + box.getWidth(),
box.getLowerLeftY() + box.getHeight());
appearance.setVisibleSignature(rect, pageNumber, fieldName);
////////////////////////////////// TRY TO ADD EXTRA SIGNATURE FIELD///////////////////////////////////////////
Rectangle documentRectangle = reader.getPageSize(pageNumber);
PdfStamper stamper = appearance.getStamper();
float pageMargin = 10;
float tableMargin = 15;
int numberOfFields = 1; // 1 sigField
float headerWidth = (documentRectangle.getWidth() - (pageMargin * 2));
// Table with signature field
PdfPTable table = new PdfPTable(1);
table.setTotalWidth(headerWidth - (tableMargin * 4));
table.setLockedWidth(Boolean.TRUE);
table.setWidthPercentage(100);
float posXTable = (pageMargin + (headerWidth - table.getTotalWidth()) / 2);
float posYTable = 400; // custom y position
int height = 70; // custom height
for (int i = 0; i < numberOfFields; i++) {
String sigFieldName = String.format(Constant.SIGNATURE_FIELD_PREFIX + "%s", (i + 1));
table.addCell(createSignatureFieldCell(stamper, sigFieldName, height, pageNumber));
}
table.writeSelectedRows(0, -1, posXTable, posYTable, stamper.getOverContent(pageNumber));
////////////////////////////////// END TRY TO ADD EXTRA SIGNATURE FIELD///////////////////////////////////////////
} else {
//APPLY SIGNATURE TO EXISTING EMPTY FIELD
List<FieldPosition> acroFields = reader.getAcroFields().getFieldPositions(sigField.getName());
fieldPosition = acroFields.get(0);
appearance.setVisibleSignature(fieldName);
}
// --------------------------- Custom signature appearance ---------------------
PdfTemplate t = appearance.getLayer(2);
Rectangle sigRect = null;
if (fieldPosition != null) {
sigRect = fieldPosition.position;
} else {
sigRect = new Rectangle(box.getLowerLeftX(), box.getLowerLeftY(), box.getLowerLeftX() + box.getWidth(),
box.getLowerLeftY() + box.getHeight());
}
// Left rectangle
Rectangle leftRect = new Rectangle(0, 0, (sigRect.getWidth() / 5), (sigRect.getHeight() / 2));
ColumnText ct1 = new ColumnText(t);
ct1.setSimpleColumn(leftRect);
Image im1 = Image.getInstance(icon.getAbsolutePath());
float ratio1 = leftRect.getHeight() / im1.getHeight();
im1.scaleToFit(im1.getWidth() * ratio1, im1.getHeight() * ratio1);
Paragraph p = createParagraph("Digital sign", font, Constant.PARAGRAPH_LEADING, Constant.MARGIN * 9);
ct1.addElement(new Chunk(im1, Constant.MARGIN * 10, 0));
ct1.addElement(p);
ct1.go();
// Middle rectangle
Rectangle middleRect = new Rectangle((sigRect.getWidth() / 5), 0,
(leftRect.getWidth() + sigRect.getWidth() / 5), (sigRect.getHeight() / 2));
ColumnText ct2 = new ColumnText(t);
ct2.setSimpleColumn(middleRect);
if (visibleSignatureImage != null) {
Image im2 = Image.getInstance(image.getAbsolutePath());
float ratio2 = sigRect.getHeight() / im2.getHeight();
im2.scaleToFit(im2.getWidth() * ratio2, im2.getHeight() * ratio2);
ct2.addElement(new Chunk(im2, 0, 0));
ct2.go();
}
// TextFields
List<TextField> textFields = fillSignatureFieldText(chain, sigProperties, font);
// Right rectangle - Names
Rectangle rightRectNames = new Rectangle(
(Constant.MARGIN * 5 + leftRect.getWidth() + middleRect.getWidth()), 0,
(leftRect.getWidth() + middleRect.getWidth() + sigRect.getWidth() / 4),
sigRect.getHeight() - Constant.MARGIN);
ColumnText ct31 = new ColumnText(t);
ct31.setSimpleColumn(rightRectNames);
List<Paragraph> paragraphsNames = textFields.stream()
.map(e -> createParagraph(e.getName(), font, Constant.PARAGRAPH_LEADING, 0))
.collect(Collectors.toList());
paragraphsNames.forEach(ct31::addElement);
ct31.go();
// Right rectangle - Values
Rectangle rightRectValues = new Rectangle(
(Constant.MARGIN * 4 + leftRect.getWidth() + middleRect.getWidth() + rightRectNames.getWidth()), 0,
sigRect.getWidth(), (sigRect.getHeight() - Constant.MARGIN));
ColumnText ct32 = new ColumnText(t);
ct32.setSimpleColumn(rightRectValues);
List<Paragraph> paragraphsValues = textFields.stream()
.map(e -> createParagraph(e.getValue(), font, Constant.PARAGRAPH_LEADING, 0))
.collect(Collectors.toList());
paragraphsValues.forEach(ct32::addElement);
ct32.go();
// --------------------------- Custom signature appearance ---------------------
}
return appearance;
}
//this is used to first create the empty fields
protected static PdfPCell createSignatureFieldCell(PdfWriter writer, String name, int height) {
PdfPCell cell = new PdfPCell();
cell.setMinimumHeight(height);
cell.setBackgroundColor(BaseColor.WHITE);
PdfFormField field = PdfFormField.createSignature(writer);
field.setFieldName(name);
field.setFlags(PdfAnnotation.FLAGS_PRINT);
cell.setCellEvent(new MySignatureFieldEvent(field, null, 0));
return cell;
}
//this is used to try to add the extra empty field to signed document
protected static PdfPCell createSignatureFieldCell(PdfStamper stamper, String name, int height, int pageNumber) {
PdfPCell cell = new PdfPCell();
cell.setMinimumHeight(height);
cell.setBackgroundColor(BaseColor.WHITE);
PdfFormField field = PdfFormField.createSignature(stamper.getWriter());
field.setFieldName(name);
field.setFlags(PdfAnnotation.FLAGS_PRINT);
cell.setCellEvent(new MySignatureFieldEvent(field, stamper, pageNumber));
return cell;
}
public static class MySignatureFieldEvent implements PdfPCellEvent {
public PdfFormField field;
public PdfStamper stamper;
public int pageField;
public MySignatureFieldEvent(PdfFormField field, PdfStamper stamper, int pageField) {
this.field = field;
this.stamper = stamper;
this.pageField = pageField;
}
public void cellLayout(PdfPCell cell, Rectangle position, PdfContentByte[] canvases) {
PdfWriter writer = canvases[0].getPdfWriter();
field.setPage();
field.setWidget(position, PdfAnnotation.HIGHLIGHT_INVERT);
if (stamper == null) {
writer.addAnnotation(field);
}else {
stamper.addAnnotation(field, pageField);
}
}
}
