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-rw-r--r--xmlsecurity/source/pdfio/pdfdocument.cxx35
1 files changed, 30 insertions, 5 deletions
diff --git a/xmlsecurity/source/pdfio/pdfdocument.cxx b/xmlsecurity/source/pdfio/pdfdocument.cxx
index c73ee5d55ac9..f3b55a8b67ee 100644
--- a/xmlsecurity/source/pdfio/pdfdocument.cxx
+++ b/xmlsecurity/source/pdfio/pdfdocument.cxx
@@ -699,6 +699,15 @@ bool PDFDocument::Sign(const uno::Reference<security::XCertificate>& xCertificat
// Write stream data.
SvMemoryStream aXRefStream;
+ const size_t nOffsetLen = 3;
+ // 3 additional bytes: predictor, the first and the third field.
+ const size_t nLineLength = nOffsetLen + 3;
+ // This is the line as it appears before tweaking according to the predictor.
+ std::vector<unsigned char> aOrigLine(nLineLength);
+ // This is the previous line.
+ std::vector<unsigned char> aPrevLine(nLineLength);
+ // This is the line as written to the stream.
+ std::vector<unsigned char> aFilteredLine(nLineLength);
for (const auto& rXRef : m_aXRef)
{
const XRefEntry& rEntry = rXRef.second;
@@ -706,6 +715,11 @@ bool PDFDocument::Sign(const uno::Reference<security::XCertificate>& xCertificat
if (!rEntry.m_bDirty)
continue;
+ // Predictor.
+ size_t nPos = 0;
+ // PNG prediction: up (on all rows).
+ aOrigLine[nPos++] = 2;
+
// First field.
unsigned char nType = 0;
switch (rEntry.m_eType)
@@ -720,25 +734,36 @@ bool PDFDocument::Sign(const uno::Reference<security::XCertificate>& xCertificat
nType = 2;
break;
}
- aXRefStream.WriteUChar(nType);
+ aOrigLine[nPos++] = nType;
// Second field.
- const size_t nOffsetLen = 3;
for (size_t i = 0; i < nOffsetLen; ++i)
{
size_t nByte = nOffsetLen - i - 1;
// Fields requiring more than one byte are stored with the
// high-order byte first.
unsigned char nCh = (rEntry.m_nOffset & (0xff << (nByte * 8))) >> (nByte * 8);
- aXRefStream.WriteUChar(nCh);
+ aOrigLine[nPos++] = nCh;
}
// Third field.
- aXRefStream.WriteUChar(0);
+ aOrigLine[nPos++] = 0;
+
+ // Now apply the predictor.
+ aFilteredLine[0] = aOrigLine[0];
+ for (size_t i = 1; i < nLineLength; ++i)
+ {
+ // Count the delta vs the previous line.
+ aFilteredLine[i] = aOrigLine[i] - aPrevLine[i];
+ // Remember the new reference.
+ aPrevLine[i] = aOrigLine[i];
+ }
+
+ aXRefStream.WriteBytes(aFilteredLine.data(), aFilteredLine.size());
}
m_aEditBuffer.WriteUInt32AsString(nXRefStreamId);
- m_aEditBuffer.WriteCharPtr(" 0 obj\n<</Filter/FlateDecode");
+ m_aEditBuffer.WriteCharPtr(" 0 obj\n<</DecodeParms<</Columns 5/Predictor 12>>/Filter/FlateDecode");
// ID.
auto pID = dynamic_cast<PDFArrayElement*>(m_pXRefStream->Lookup("ID"));