vcl PDF import: don't assume larger offset -> newer trailer

Usually when the PDF file contains incremental updates the updates are
appended at the end of the document. But this is not required, the
various trailers can be in any order. Make sure that we look at the last
trailer (logically last, not the one with the largest file offset) when
looking for pages.

Reviewed-on: https://gerrit.libreoffice.org/36527
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>
(cherry picked from commit f15a69bd57e578ca607f14cb62f29a16986b96e6)

Conflicts:
xmlsecurity/qa/unit/pdfsigning/pdfsigning.cxx

Change-Id: Idcd85a7c6bbf08c9436dd73933d79cdb683f482c

2 files changed, 103 insertions, 0 deletions

diff --git a/xmlsecurity/qa/unit/pdfsigning/data/tdf107149.pdf b/xmlsecurity/qa/unit/pdfsigning/data/tdf107149.pdf
new file mode 100644
index 000000000000..db063f366a93
--- /dev/null
+++ b/xmlsecurity/qa/unit/pdfsigning/data/tdf107149.pdf
@@ -0,0 +1,97 @@
+%PDF-1.2
+%����
+3 0 obj 
+<<
+/Length 61
+>>
+stream
+  BT
+  /F1 24 Tf
+  1 0 0 1 260 254 Tm
+  (Hello Worl2)Tj
+  ET
+
+endstream 
+endobj xref
+0 7
+0000000000 65535 f 
+0000000312 00000 n 
+0000000532 00000 n 
+0000000015 00000 n 
+0000000660 00000 n 
+0000000578 00000 n 
+0000000743 00000 n 
+trailer
+
+<<
+/Root 6 0 R
+/Size 7
+>>
+1 0 obj 
+<<
+/Resources 2 0 R
+/Contents 3 0 R
+/Parent 4 0 R
+/Type /Page
+/MediaBox [0 0 612 446]
+>>
+endobj 
+3 0 obj 
+<<
+/Length 61
+>>
+stream
+  BT
+  /F1 24 Tf
+  1 0 0 1 260 254 Tm
+  (Hello World)Tj
+  ET
+
+endstream 
+endobj 
+2 0 obj 
+<<
+/Font 
+<<
+/F1 5 0 R
+>>
+>>
+endobj 
+5 0 obj 
+<<
+/Subtype /Type1
+/Name /F1
+/Type /Font
+/BaseFont /Helvetica
+>>
+endobj 
+4 0 obj 
+<<
+/Kids [1 0 R]
+/Type /Pages
+/MediaBox [0 0 612 446]
+/Count 1
+>>
+endobj 
+6 0 obj 
+<<
+/Type /Catalog
+/Pages 4 0 R
+>>
+endobj xref
+0 7
+0000000000 65535 f 
+0000000015 00000 n 
+0000000235 00000 n 
+0000000121 00000 n 
+0000000363 00000 n 
+0000000281 00000 n 
+0000000446 00000 n 
+trailer
+
+<<
+/Size 7
+>>
+startxref
+128
+%%EOF
diff --git a/xmlsecurity/qa/unit/pdfsigning/pdfsigning.cxx b/xmlsecurity/qa/unit/pdfsigning/pdfsigning.cxx
index 69916d677a98..015e5a02924e 100644
--- a/xmlsecurity/qa/unit/pdfsigning/pdfsigning.cxx
+++ b/xmlsecurity/qa/unit/pdfsigning/pdfsigning.cxx
@@ -395,6 +395,7 @@ void PDFSigningTest::testTokenize()
         OUStringLiteral("noeol.pdf"),
         // File that's intentionally smaller than 1024 bytes.
         OUStringLiteral("small.pdf"),
+        OUStringLiteral("tdf107149.pdf"),
     };
 
     for (const auto& rName : aNames)
@@ -403,6 +404,11 @@ void PDFSigningTest::testTokenize()
         vcl::filter::PDFDocument aDocument;
         // Just make sure the tokenizer finishes without an error, don't look at the signature.
         CPPUNIT_ASSERT(aDocument.Read(aStream));
+
+        OUString aNoPages("tdf107149.pdf");
+        if (aNoPages == rName)
+            // This failed, page list was empty.
+            CPPUNIT_ASSERT_EQUAL(static_cast<size_t>(1), aDocument.GetPages().size());
     }
 }