Error signing an already signed PDF

[DavidBS]

Hi,

I'm successfully signing a PDF using the Syncfusion control.

But, when I try to add another valid signature, I got error 0x80070057 = the document may contain at most one author signature.

I'm following the code described at https://help.syncfusion.com/file-formats/pdf/working-with-digitalsignature?cs-save-lang=1&cs-lang=vb#signing-an-existing-document

The first signature has the following propterties:

signature.TimeStampServer = New TimeStampServer(New Uri("http://rfc3161timestamp.globalsign.com/advanced"))

signature.EnableValidationAppearance = False

signature.EnableLtv = True

signature.Certificated = True

        signature.DocumentPermissions = PdfCertificationFlags.AllowFormFill

The document is loaded as follows:

     Dim signature As PdfSignature = Nothing

     

     Try

          Dim CampoDeAssinatura As PdfLoadedSignatureField = TryCast(loadedDocument.Form.Fields(0), PdfLoadedSignatureField)

          signature = New PdfSignature(loadedDocument, page, pdfCert, "SignatureField", CampoDeAssinatura)

     

     Catch ex As Exception

          signature = New PdfSignature(loadedDocument, page, pdfCert, "SignatureField")

     

     End Try

Everything runs OK until the "Save" command, which raises the above error.

The document being signed is the same of the first signature, I mean, I'm signing it normally and trying to resign with another certificate (and all certificates are 100%).

Do you know what is happening here?

I appreciate any help

[DavidBS]

Hmmm...

I got the problem and I guess it can be a bug:

If the document is virgin (not signed before) I set "signature.Certified = true" and in opposite (the document is already signed) I set "signature.Certified = false" - and at this point the error raises.

I mean, we cannot set "Certified=false" in an already signed document - we need only to discard the property entirelly.

Ok, some people may consider that setting "Certified=false" is uneccessary anyway since it is the default, but I see as a little bug within the code.

I hope have helped anyone with the same behaviour.

[Surya Kumar]

Hi David, 

Greetings from Syncfusion. 

Response	Query
But, when I try to add another valid signature, I got error 0x80070057 = the document may contain at most one author signature.    I'm following the code described at https://help.syncfusion.com/file-formats/pdf/working-with-digitalsignature?cs-save-lang=1&cs-lang=vb#signing-an-existing-document    The first signature has the following propterties:                signature.TimeStampServer = New TimeStampServer(New Uri("http://rfc3161timestamp.globalsign.com/advanced"))              signature.EnableValidationAppearance = False              signature.EnableLtv = True              signature.Certificated = True          signature.DocumentPermissions = PdfCertificationFlags.AllowFormFill    Everything runs OK until the "Save" command, which raises the above error.	Could you please provide us the stack trace of the exception or error you got along with the PDF in which the error occurs so that we can analyze and provide you exact solution.
If the document is virgin (not signed before) I set "signature.Certified = true" and in opposite (the document is already signed) I set "signature.Certified = false" - and at this point the error raises.    I mean, we cannot set "Certified=false" in an already signed document - we need only to discard the property entirelly.	We are analyzing this behavior we will let you know more about this on 04-Sep-19.

Regards, 

Surya Kumar 

[Sowmiya Loganathan]

Hi David, 

Please note that the property “Signature.Certified” can be set only when the signature is field is created and added to the PDF. Modifying the existing signature in PDF will invalidate the signature present in the PDF.  

So could you please provide us your exact requirement for changing the “Signature.Certified= false” in already signed PDF document, so that we can help you with better solution on the same. 

 

Regards, 

Sowmiya L 

[DavidBS]

Thank YOU Sowmyia, yes, you're right but to avoid too much text, let's interact on that:

https://www.syncfusion.com/forums/147103/know-how-many-signatures-pdf-has

I appreciate your time, help and efforts.