[PDFBOX-912] PDF signing interface and improvments

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.4.0
• Fix Version/s: 1.6.0
• Component/s: AcroForm, PDModel, Swing GUI, Writing
• Assignee: Adam Nichols
• Reporter: Thomas Chojecki
• Created: 29/Nov/10 23:00
• Updated: 24/Jan/14 13:50
• Resolved: 16/May/11 22:10

Description

This is a first version of a signing interface for pdfbox. There are some design issues i could not handle without rewriting too much of the code.

Here we go:

• incremental update support (tested for signatures with pdf/a compatibility), not compatible with encrypted documents nor with xref-streams

• cos object improvment
  • COSString with ability to force writing hexbin for given string
  • COSBase with ability to write direct into a dictionary (that means if this is set, no indirect object will be wrote) (sry hard to explain what i mean, actualy needed for incremental update to lower the rate of indirect objects)
  • COSBase with ability to force writing object (this hook help the COSWriter write needed objects for inkremental update)
  • COSName added new names
  • COSDocument some getter and setter for handling new signature and incremental features

• SignatureException with some exceptions for handling the bunch of new possible errors

-Parser improvments
– PDFParser saves now the position of the last startxref
– VisualSignatureParser (hook for parsing visual signature templates) (it's only for prepared visualisation that should be merged with the document)

-IO improvments
– COSFilterInput helps to find the proper content that should be hashed / signed
– COSStandardOutputStream is tricky, it helps the writer to jump to the right place in the document
– COSWriter got some improvments for incremental update
– COSWriterXRefEntry needed for incremental updates and writing the new Xref table

• PDDocument
  • got a new method addSignature with the needed implementation (do the whole signature stuff)
  • cleanup

• Fields and Annotations
  • PDSignature represent the signature dictionary
  • PDSignatureFild / Annotation are the visible & unvisible signature representations

• Signature Interface and options
  • SignatureInterface the interface that shall be implemented for proper signing
  • SignatureOptions, some additional options for signing

Patch splited into pieces

sry for spelling, didn't include a spellchecker for english.

Issue Links

• relates to: PDFBOX-911 Method PDDocument.getNumberOfPages() returns wrong number of pages
• relates to: PDFBOX-13 Add ability to digitally sign a PDF
• relates to: PDFBOX-275 add digital signature support