[PDFBOX-3848] Get the exact original PDF that was signed(without signature fields)

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Not A Problem
• Affects Version/s: 2.0.6
• Component/s: AcroForm, Signing
• Assignee: Unassigned
• Reporter: Nikola Radosevic
• Created: 30/Jun/17 10:36
• Updated: 01/Jul/17 03:12
• Resolved: 01/Jul/17 03:12

Description

I am trying to get the original pdf from the signed pdf.

I am able to remove the signature using doc.getSignatureDictionaries().get(0).getSignedContent(signedPDF);

However, the signature field stays.

However, when I try to remove the signature fields using the following code:

PDDocument pdDoc = PDDocument.load(origPDF);
PDDocumentCatalog catalog = pdDoc.getDocumentCatalog();
PDAcroForm form = catalog.getAcroForm();
List<PDField> acroFormFields = form.getFields();
for (PDField field: acroFormFields) {
if (field.getFieldType().equalsIgnoreCase("Sig"))

{ System.out.println("START removing Sign Flags"); field.setReadOnly(true); field.setRequired(false); field.setNoExport(true); System.out.println("END removing Sign Flags"); System.out.println("START flattenning field"); field.getAcroForm().flatten(); field.getAcroForm().refreshAppearances(); System.out.println("END flattenning field"); //field.getAcroForm().refreshAppearances(); }

The signature field is removed, but the image that was used for visible signature, somehow, magically appear. (The document that I load here is the one that has signature removed using origPDF = doc.getSignatureDictionaries().get(0).getSignedContent(signedPDF);

See the attached files:
Example.pdf (Original file)
Example_Signed.pdf (Signed File)
Example_Signed_orig.pdf (after removing the signature)
Example_Signed_final.pdf (after flattening the Example_Signed_orig.pdf)

See the stackoverflow post for more details:

https://stackoverflow.com/questions/44843095/verifying-pdf-signature-in-java-using-bouncy-castle-and-pdfbox