[PDFBOX-3017] Improve document signing

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.0, 3.0.0 PDFBox
• Fix Version/s: 2.0.23, 3.0.0 PDFBox
• Component/s: AcroForm, Signing
• Assignee: Unassigned
• Reporter: Tilman Hausherr
• Created: 09/Oct/15 19:07
• Updated: 17/Aug/21 16:50
• Resolved: 14/Jan/21 18:09

Description

Improve signing code:

• incremental save only works for signatures and doesn't respect certificates such as Adobe Extended Usage Rights
• prepareNonVisualSignature clears the AcroForm DR acroForm.setDefaultResources(null) which is not good if there are other form fields
• visual/nonVisualSignature should move into the interactive.forms package and be handled within the signature field
• verify signature (to have tests that go full circle) done June 2016
• document or refactor / rewrite visible labyrinthine signature code
• why is it not possible to pass only the signatureField to addSignature, instead having to create a COSDocument with a page and annotations that has the signature field, and that must be searched for in prepareVisibleSignature()?
• support rotated pages (see https://stackoverflow.com/questions/34012293/pdfbox-sign-landscape-file-error/34359956#34359956 ) done in PDFBOX-3671
• make sure that signed PDF/A files are still PDF/A (see http://www.pdfa.org/wp-content/uploads/2011/08/tn0006_digital_signatures_in_pdfa-1_2008-03-14.pdf ); /ID possibly not OK; /Annots is possibly required (tilman removed this for invisible signatures); test signed files with PDF-Tools and with preflight tested, they are OK with PDF-Tools and preflight
• test whether "bad" signatures are detected by preflight (search in old issues)
• PDFBOX-3363 - why is the stream cached in a file? Should it be done in memory? done on July 15, 2016
• remove setVisualSignature(PDVisibleSigProperties visSignatureProperties) from SignatureOptions.java, all it does is to call visSignatureProperties.getVisibleSignature() which returns an InputStream, and this is already available
• checkSignatureField violates the "do one thing" rule
• decide whether the whole certificate chain should be passed in the sample code, instead of only the first one yes the whole chain is stored
• check certificate chain, revocation lists, etc, only if needed by users, code here
• deprecate / remove all PDVisibleSignDesigner constructors except those with a PDDocument object, to avoid a file being opened twice
• ... your ideas...

Issue Links

• is depended upon by: PDFBOX-3198 Visible Signature N2 layer / Support signature with text
• links to: GitHub Pull Request #39
• links to: Stackoverflow: PDFBox 1.8.10: Fill and Sign Document, Filling again fails
• links to: Unhelpful error message when using X509CRL.verify(java.security.PublicKey, java.security.Provider) in project intended for jdk 1.7 #60