[okular] [Bug 482682] Digital Signature not referenced in AcroForm

[Tobias Wich]

https://bugs.kde.org/show_bug.cgi?id=482682

--- Comment #6 from Tobias Wich <tobias.wich at electrologic.org> ---
(In reply to Sune Vuorela from comment #5)
> Created attachment 166594 [details]
> Unsigned document with form
> 
> I guess we should investigate how this form differs from your form ...

I see several differences. I will refer to doc A for my document and doc B for
yours.
1) Doc A embeds the AcroForm as a nested object in the Catalog dict, while doc
B puts the AcroForm into an indirect object and references it in the Catalog
2) Doc B contains NeedAppearances=true in the AcroForm, while A lacks this
property
3) Doc B contains a DA property, doc A not
4) Doc A has DR as an object reference, doc B embeds the object
5) Doc B contains an unsigned signature field (/FT=/Sig), while A does not

I think 1) is a good candidate to look further, as it certainly makes a
difference in the implementation if the AcroForm is just an object which can be
rewritten in the increment, or if the parent element containing the AcroForm
has to be modified as well.

In doc B it makes no difference whether I sign the existing signature field, or
if I let Okular add a new one. In both cases the signature entry is either
updated, or added in the AcroForm, so it validates just fine. 

Btw, I created the document with LibreOffice 6.3 quite some time ago. The
current LibreOffice (24.2.0.3) yields the same structure. So maybe having a
document built in this way is maybe not completely out of the ordinary.

-- 
You are receiving this mail because:
You are the assignee for the bug.