Error when signing malformed docs (fix available)

[julienrffr]

PDFsharp/src/foundation/src/PDFsharp/src/PdfSharp/Pdf.Signatures/PdfSignatureHandler.cs

Line 156 in 6aacefa

Document.Pages[Options.PageIndex].Elements.Add(PdfPage.Keys.Annots, new PdfArray(Document, signatureField));

Using .Add(...) throw an exception when the /Annots key exists.

I stumbled upon some PDF documents generated by www.princexml.com that has the /Annots key present in this dictionary, but the reference PDF object does not exist, in PdfSharp this gives a null value for the /Annots key in the dictionary.
For example the /Annots element references an object '70 0 R' but there is no element with this reference in the document.
Leading to .Add(...) throwing an exception.

Simple fix is to use the indexer of the dictionary to overwrite the value instead of throwing:
KDS@233b486

[ThomasHoevel]

I stumbled upon some PDF documents [...]

Can you share some of those with us for testing?

[julienrffr]

I stumbled upon some PDF documents [...]

Can you share some of those with us for testing?

Hi, I cannot share the documents where I saw the issue as they are customer confidential documents.
However I can see the issue seems to be still present on latest version of the software:
Go to https://www.princexml.com/samples/ and download the first sample (dictionary)

dictionary.pdf

/Annots 701 0 R>>

But there is no pdf object defined for '701 0 obj'

[julienrffr]

Created #255 as a fix for this issue, and added a reproduction document

@ThomasHoevel

[Volkmire]

Hi @ThomasHoevel , we have a similar issue, but when trying to copy a document page by page (we have some cases where pdfs are protected with an owner password that we need to replace). Can't share the document, unfortunately.

Example stack trace:

System.Collections.Generic.KeyNotFoundException: The given key '719 0' was not present in the dictionary.    at 
PdfSharp.Pdf.Advanced.PdfImportedObjectTable.get_Item(PdfObjectID externalID)    at 
PdfSharp.Pdf.PdfObject.FixUpObject(PdfImportedObjectTable iot, PdfDocument owner, PdfObject value)    at 
PdfSharp.Pdf.PdfObject.ImportClosure(PdfImportedObjectTable importedObjectTable, PdfDocument owner, PdfObject externalObject)    at 
PdfSharp.Pdf.PdfPages.CloneElement(PdfPage page, PdfPage importPage, String key, Boolean deepCopy)    at 
PdfSharp.Pdf.PdfPages.ImportExternalPage(PdfPage importPage)    at PdfSharp.Pdf.PdfPages.Insert(Int32 index, PdfPage page)
```****