Sign a signed-PDF with it's hash value

Since you are using an API which claims to do want you want, but doesn't seem to be doing that, you need to contact the support for PDFBox. 

Well, actually he feeds the API other data than the API is designed for (a hash where the to-be signed byte ranges are expected), so that wouldn't be a support call but a request for a different feature...

Many thanks for your replies. Here are the main portions of my code.

public class PdfBoxLTV implements SignatureInterface {

public static void main(String[] args) throws Exception {
try {
String certificatePass = "123456";
String certificateFilePath = "C:\\pathToCertificate\\certificate.p12";
String pdfFilePath = "C:\\pathToPDF\\file.pdf";
String cryptographic = "SHA-256"; //"SHA-256";

initialise(certificatePass, certificateFilePath, pdfFilePath);

scanAndSetSignature();

InputStream documentHash = getDocumentHash(cryptographic);

signSignature(documentHash);

AddValidationInformation.setLTV(signedFile);
} catch (FileNotFoundException fex) {
fex.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

....

public static void signSignature(InputStream documentHash) throws Exception {
PdfBoxLTV detachedPkcs7 = new PdfBoxLTV();

// get the pdf document hash, and apply signature to pdf
byte[] cmsSignature = detachedPkcs7.sign(documentHash);

// apply signature to the pdf using the returned signed bytes
externalSigning.setSignature(cmsSignature);
}

private static void scanAndSetSignature() {
int accessPermissions = SigUtils.getMDPPermission(document);
if (accessPermissions == 1) {
throw new IllegalStateException("No changes to the document are permitted due to DocMDP transform parameters dictionary");
}

System.out.println("ENTER NAME: ");
Scanner s = new Scanner(System.in);
final String mName = s.nextLine();
System.out.println("ENTER LOCATION: ");
final String mLocation = s.nextLine();
System.out.println("ENTER REASON: ");
final String mReason = s.nextLine();
s.close();

System.out.println("You entered : \nNAME : " + mName + "\nLOCATION : " + mLocation + "\nREASON : " + mReason);
System.out.println("Signing...");

// sign a PDF with an existing empty signature, as created by the CreateEmptySignatureForm example.
signature = findExistingSignature(document, null);

if (signature == null) {
// create signature dictionary
signature = new PDSignature();
}

signature.setFilter(PDSignature.FILTER_ADOBE_PPKLITE);
signature.setSubFilter(PDSignature.SUBFILTER_ADBE_PKCS7_DETACHED);
signature.setName(mName);
signature.setLocation(mLocation);
signature.setReason(mReason);

Calendar date = Calendar.getInstance();
signature.setSignDate(date);
}
public static InputStream getDocumentHash(String cryptographic) throws Exception {
document.addSignature(signature);

externalSigning = document.saveIncrementalForExternalSigning(signedOutputStream);

if (cryptographic.length() == 0) {
return externalSigning.getContent();
}

byte[] contentBytes = externalSigning.getContent().readAllBytes();
byte[] hashBytes = MessageDigest.getInstance(cryptographic, new BouncyCastleProvider()).digest(contentBytes);
InputStream hashedInputStream = new ByteArrayInputStream(hashBytes);

return hashedInputStream;
//return externalSigning.getContent();
}

[reply edited by moderator]

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