Getting "key does not exist" error when saving a PDF

[Charles Southey]

Hi,

We are using the Syncfusion PDF component to assemble externally-source PDF documents into a single document. With some documents, when attempting to save, we are getting this exception:

{"Key does not exist.\r\n"}

    Data: {System.Collections.ListDictionaryInternal}

    HResult: -2146893811

    HelpLink: null

    InnerException: null

    Message: "Key does not exist.\r\n"

    Source: "System.Security"

    StackTrace: "   at System.Security.Cryptography.Pkcs.SignedCms.ComputeSignature(CmsSigner signer, Boolean silent)\r\n   at Syncfusion.Pdf.Security.PdfSignatureDictionary.SignCertificate(Byte[] message, X509Certificate2 cert, Boolean detached)\r\n   at Syncfusion.Pdf.Security.PdfSignatureDictionary.GetStoreCertificate()\r\n   at Syncfusion.Pdf.Security.PdfSignatureDictionary.DocumentSaved(Object sender, DocumentSavedEventArgs e)\r\n   at Syncfusion.Pdf.PdfDocumentBase.OnDocumentSaved(DocumentSavedEventArgs args)\r\n   at Syncfusion.Pdf.Parsing.PdfLoadedDocument.Save(Stream stream)\r\n  "

    TargetSite: {Void ComputeSignature(System.Security.Cryptography.Pkcs.CmsSigner, Boolean)}

Can you explain what this is and how to avoid it?

[Charles Southey]

UPDATE: I have established that the cause is an invalid signature in the document, and have added a workaround to remove all signature fields as follows:

                                        var loadedSignatures = nextPDF?.Form?.Fields?.OfType<PdfLoadedSignatureField>().ToList() ?? new List<PdfLoadedSignatureField>();

                                        foreach (var loadedSignatureField in loadedSignatures)

                                        {

                                            nextPDF.Form.Fields.Remove(loadedSignatureField);

                                        }

However that's quite draconian - it would be better if it failed more gracefully and let us save the document without having to remove the field. Adobe reader identifies the invalid signature but still allows the file to be read etc.

[Surya Kumar]

Hi Charles, 

Greetings from Syncfusion. 

We suspect that the issue which you have mentioned is specific to the document so could you please provide us the PDF in which this issue is reproduced. So that it will be helpful for us to analyze and provide you a solution. 

Regards, 

Surya Kumar