xmlsecurity: pdf incremental updates that are non-commenting are invalid

I.e. it's OK to add incremental updates for annotation/commenting
purposes and that doesn't invalite existing signatures. Everything else
does.

(cherry picked from commit 61834cd574568613f0b0a2ee099a60fa5a8d9804)

Conflicts:
include/vcl/filter/PDFiumLibrary.hxx
vcl/source/pdf/PDFiumLibrary.cxx
xmlsecurity/qa/unit/signing/signing.cxx

Change-Id: I4607c242b3c6f6b01517b02407e9e7a095e2e069
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/106762
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/include/vcl/filter/PDFiumLibrary.hxx b/include/vcl/filter/PDFiumLibrary.hxx
index bc7912c17e81..7e8ef4e3ad48 100644
--- a/include/vcl/filter/PDFiumLibrary.hxx
+++ b/include/vcl/filter/PDFiumLibrary.hxx
@@ -17,6 +17,9 @@
 #include <memory>
 #include <rtl/instance.hxx>
 #include <vcl/dllapi.h>
+#include <vcl/checksum.hxx>
+
+#include <fpdfview.h>
 
 namespace vcl::pdf
 {
@@ -31,6 +34,33 @@ public:
     ~PDFium();
 };
 
+class VCL_DLLPUBLIC PDFiumPage final
+{
+private:
+    FPDF_PAGE mpPage;
+
+private:
+    PDFiumPage(const PDFiumPage&) = delete;
+    PDFiumPage& operator=(const PDFiumPage&) = delete;
+
+public:
+    PDFiumPage(FPDF_PAGE pPage)
+        : mpPage(pPage)
+    {
+    }
+
+    ~PDFiumPage()
+    {
+        if (mpPage)
+            FPDF_ClosePage(mpPage);
+    }
+
+    FPDF_PAGE getPointer() { return mpPage; }
+
+    /// Get bitmap checksum of the page, without annotations/commenting.
+    BitmapChecksum getChecksum();
+};
+
 struct PDFiumLibrary : public rtl::StaticWithInit<std::shared_ptr<PDFium>, PDFiumLibrary>
 {
     std::shared_ptr<PDFium> operator()() { return std::make_shared<PDFium>(); }