verify digital signature pdf java IText

Question

I was trying to validate the signature I added to a pdf file with IText with my token but I got some errors:

java.security.InvalidKeyException: No installed provider supports this key: (null)

This is my code:

//verifying pdf signatures
public PdfPKCS7 verifySignature(AcroFields fields, String name) throws GeneralSecurityException, IOException {
    System.out.println("Signature covers whole document: " + fields.signatureCoversWholeDocument(name));
    System.out.println("Document revision: " + fields.getRevision(name) + " of " + fields.getTotalRevisions());
    PdfPKCS7 pkcs7 = fields.verifySignature(name);
    System.out.println("Integrity check OK? " + pkcs7.verify());
    return pkcs7;
}

public void verifySignatures(String path) throws IOException, GeneralSecurityException {
    System.out.println(path);
    PdfReader reader = new PdfReader(path);
    AcroFields fields = reader.getAcroFields();
    ArrayList<String> names = fields.getSignatureNames();
    for (String name : names) {
        System.out.println("===== " + name + " =====");
        verifySignature(fields, name);
    }
    System.out.println();
}

This is the whole log:

===== sig_2 =====
Signature covers whole document: true
Document revision: 1 of 1
Exception in thread "main" ExceptionConverter: 
java.security.InvalidKeyException: No installed provider supports this key: (null)
at java.security.Signature$Delegate.chooseProvider(Unknown Source)
at java.security.Signature$Delegate.engineInitVerify(Unknown Source)
at java.security.Signature.initVerify(Unknown Source)
at com.itextpdf.text.pdf.security.PdfPKCS7.<init>(PdfPKCS7.java:452)
at com.itextpdf.text.pdf.AcroFields.verifySignature(AcroFields.java:2317)
at com.itextpdf.text.pdf.AcroFields.verifySignature(AcroFields.java:2270)
at com.pdf.sign.Main.verifySignature(Main.java:91)
at com.pdf.sign.Main.verifySignatures(Main.java:103)
at com.pdf.sign.Main.main(Main.java:147)

Answer 1

Your keystore doesn't seem to get initialized, and so your key is null.

For examples of usage, I found this: http://grepcode.com/file/repo1.maven.org/maven2/com.itextpdf/itextpdf/5.0.6/com/itextpdf/text/pdf/AcroFields.java#AcroFields.verifySignature%28java.lang.String%2Cjava.lang.String%29

There you can also see source code and find where and why the exception is thrown.