OpenSystemsDevelopment / qpdf

Commit 06b818dcd39b5aeaeeee5c247483633a02a0222e

Authored by Masamichi Hosoda
Committed by Jay Berkenbilt
1 parent 5e0ba126

Exclude signature dictionary from compressible objects 

It seems better not to compress signature dictionaries. Various PDF
digital signing tools, including Adobe Acrobat Reader DC, do not
compress signature dictionaries.

Table 8.93 "Entries in a signature dictionary" in PDF 1.5 reference
describes that /ByteRange in the signature dictionary shall be used to
describe a digest that does not include the signature value
(/Contents) itself.

The byte ranges cannot be determined if the dictionary is compressed.
Inline Side-by-side
Showing 2 changed files with 9 additions and 3 deletions
libqpdf/QPDF.cc
  View file @06b818d
... ... @@ -2673,7 +2673,13 @@ QPDF::getCompressibleObjGens()
2673 2673 {
2674 2674 QTC::TC("qpdf", "QPDF exclude encryption dictionary");
2675 2675 }
2676   - else if (! obj.isStream())
  2676 + else if ((! obj.isStream()) &&
  2677 + (! (obj.isDictionary() &&
  2678 + obj.hasKey("/ByteRange") &&
  2679 + obj.hasKey("/Contents") &&
  2680 + obj.hasKey("/Type") &&
  2681 + obj.getKey("/Type").isName() &&
  2682 + obj.getKey("/Type").getName() == "/Sig")))
2677 2683 {
2678 2684 result.push_back(og);
2679 2685 }
... ...
qpdf/qtest/qpdf.test
  View file @06b818d
... ... @@ -3998,9 +3998,9 @@ $td->runtest("fix-qdf with big object stream", # > 255 objects in a stream
3998 3998 show_ntests();
3999 3999 # ----------
4000 4000 $td->notify("--- Signature Dictionary ---");
4001   -$n_tests += 4;
  4001 +$n_tests += 6;
4002 4002  
4003   -foreach my $i (qw(preserve disable))
  4003 +foreach my $i (qw(preserve disable generate))
4004 4004 {
4005 4005 $td->runtest("sig dict contents hex (object-streams=$i)",
4006 4006 {$td->COMMAND =>
... ...