How to verify PDF signature

[Lajos Djerfi]

I need to verify if PDF document is signed (by Sincfusion library or other application) and is it modified after initially digitaly signed.

Is it possible with Syncfusion library?

[Sowmiya Loganathan]

Hi Lajos, 

Thank you for contacting Syncfusion support. 

At present we do not have support to validate digital signature in an existing PDF document. We have already logged a feature request and added it to our feature request list. We do not have any immediate plans to implement this feature. We will let you know once the feature is implemented.  

Please find our support list in the below link: 

https://www.syncfusion.com/products/file-formats/pdf#feature-matrix  

Please let us know if you have any further assistance on this. 

Regards, 

Sowmiya L 

[Lajos Djerfi]

All right,

I understand that I can not do integrity checking with your library. Can I enumerate all signatures from file and get all fields from signatures and from certificates.

Best regards.

[Sowmiya Loganathan]

Hi Lajos, 

We can get all the signature fields and its signature properties from the existing PDF document, but it is not possible to get the certificates from the PDF document. Please refer the below code snippet for your reference, 

            //Loads a PDF document 

            PdfLoadedDocument loadedDocument = new PdfLoadedDocument("Input.pdf"); 

 

            //Gets the form fields collection 

            PdfLoadedFormFieldCollection fields = loadedDocument.Form.Fields; 

 

            //Gets the first signature field of the PDF document 

            PdfLoadedSignatureField field = fields[0] as PdfLoadedSignatureField; 

 

            //Gets the signature from the signature field 

            PdfSignature sigature = field.Signature; 

Please let us know if you need any further assistance on this. 

Regards, 

Sowmiya L 

[Sowmiya Loganathan]

Hi Lajos, 

 

We glad to announce that the feature “Support for validating digital signatures in existing PDF document” is implemented and it is included in our Essential Studio 2019 Volume 3 Beta release v17.3.0.9. This is rolled out and is available for download under the following link,  

https://www.syncfusion.com/forums/147704/essential-studio-2019-volume-3-beta-release-v17-3-0-9-is-available-for-download   

  

Please find the code snippet to illustrate this from below,  

  

//Load an existing signed PDF document  

PdfLoadedDocument loadedDocument = new PdfLoadedDocument("Input.pdf"); 

 

//Get signature field  

PdfLoadedSignatureField signatureField = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField; 

 

//X509Certificate2Collection to check the signer's identity using root certificates  

X509CertificateCollection collection = new X509CertificateCollection(); 

 

//Create new X509Certificate2 with the root certificate  

X509Certificate2 certificate = new X509Certificate2("PDF.pfx", "syncfusion"); 

 

//Add the certificate to the collection  

collection.Add(certificate); 

 

//Validate signature and get the validation result  

PdfSignatureValidationResult result = signatureField.ValidateSignature(collection); 

 

//Checks whether the signature is valid or not  

SignatureStatus status = result.SignatureStatus; 

 

//Checks whether the document is modified or not  

bool isModified = result.IsDocumentModified; 

 

//Signature details  

string issuerName = signatureField.Signature.Certificate.IssuerName; 

DateTime validFrom = signatureField.Signature.Certificate.ValidFrom; 

DateTime validTo = signatureField.Signature.Certificate.ValidTo; 

string signatureAlgorithm = result.SignatureAlgorithm; 

DigestAlgorithm digestAlgorithm = result.DigestAlgorithm; 

 

//Revocation validation details  

RevocationResult revocationDetails = result.RevocationResult; 

RevocationStatus revocationStatus = revocationDetails.OcspRevocationStatus; 

bool isRevokedCRL = revocationDetails.IsRevokedCRL; 

 

//Checks whether the signature is valid or not based on the overall validation  

bool isSignatureValid = result.IsSignatureValid; 

 

//Close the document  

loadedDocument.Close(true); 

 

Regards,              

Sowmiya Loganathan