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xmlsecurity PDF verify: fix reading multiple subsections from an xref stream

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This is especially needed, as we don't bother compressing updated
objects into sections on signing, we simply use a separate section for
each updated object.

Work towards supporting xref streams and incremental updates at the same
time.

Change-Id: Ie9759edbba816991615fafc6602cdd440141b989
This commit is contained in:
Miklos Vajna
2016-11-10 10:33:02 +01:00
parent 7cde8def93
commit bec9e673ad
1 changed files with 105 additions and 87 deletions
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192
xmlsecurity/source/pdfio/pdfdocument.cxx
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@@ -1265,7 +1265,7 @@ bool PDFDocument::Read(SvStream& rStream)
SAL_INFO("xmlsecurity.pdfio", "PDFDocument::Read: nStartXRef is " << nStartXRef); SAL_INFO("xmlsecurity.pdfio", "PDFDocument::Read: nStartXRef is " << nStartXRef);
if (nStartXRef == 0) if (nStartXRef == 0)
{ {
SAL_WARN("xmlsecurity.pdfio", "PDFDocument::Read: found no xref statrt offset"); SAL_WARN("xmlsecurity.pdfio", "PDFDocument::Read: found no xref start offset");
return false; return false;
} }
while (true) while (true)
@@ -1466,37 +1466,49 @@ void PDFDocument::ReadXRefStream(SvStream& rStream)
// Look up the first and the last entry we need to read. // Look up the first and the last entry we need to read.
auto pIndex = dynamic_cast<PDFArrayElement*>(pObject->Lookup("Index")); auto pIndex = dynamic_cast<PDFArrayElement*>(pObject->Lookup("Index"));
size_t nFirstObject = 0; std::vector<size_t> aFirstObjects;
size_t nNumberOfObjects = 0; std::vector<size_t> aNumberOfObjects;
if (!pIndex || pIndex->GetElements().size() < 2) if (!pIndex)
{ {
auto pSize = dynamic_cast<PDFNumberElement*>(pObject->Lookup("Size")); auto pSize = dynamic_cast<PDFNumberElement*>(pObject->Lookup("Size"));
if (pSize) if (pSize)
nNumberOfObjects = pSize->GetValue(); {
aFirstObjects.push_back(0);
aNumberOfObjects.push_back(pSize->GetValue());
}
else else
{ {
SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRefStream: Index not found or has < 2 elements"); SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRefStream: Index and Size not found");
return; return;
} }
} }
else else
{ {
const std::vector<PDFElement*>& rIndexElements = pIndex->GetElements(); const std::vector<PDFElement*>& rIndexElements = pIndex->GetElements();
auto pFirstObject = dynamic_cast<PDFNumberElement*>(rIndexElements[0]); size_t nFirstObject = 0;
if (!pFirstObject) for (size_t i = 0; i < rIndexElements.size(); ++i)
{ {
SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRefStream: Index has no first object"); if (i % 2 == 0)
return; {
} auto pFirstObject = dynamic_cast<PDFNumberElement*>(rIndexElements[i]);
nFirstObject = pFirstObject->GetValue(); if (!pFirstObject)
{
SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRefStream: Index has no first object");
return;
}
nFirstObject = pFirstObject->GetValue();
continue;
}
auto pNumberOfObjects = dynamic_cast<PDFNumberElement*>(rIndexElements[1]); auto pNumberOfObjects = dynamic_cast<PDFNumberElement*>(rIndexElements[i]);
if (!pNumberOfObjects) if (!pNumberOfObjects)
{ {
SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRefStream: Index has no number of objects"); SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRefStream: Index has no number of objects");
return; return;
}
aFirstObjects.push_back(nFirstObject);
aNumberOfObjects.push_back(pNumberOfObjects->GetValue());
} }
nNumberOfObjects = pNumberOfObjects->GetValue();
} }
// Look up the format of a single entry. // Look up the format of a single entry.
@@ -1529,89 +1541,95 @@ void PDFDocument::ReadXRefStream(SvStream& rStream)
} }
aStream.Seek(0); aStream.Seek(0);
// This is the line as read from the stream. for (size_t nSubSection = 0; nSubSection < aFirstObjects.size(); ++nSubSection)
std::vector<unsigned char> aOrigLine(nLineLength);
// This is the line as it appears after tweaking according to nPredictor.
std::vector<unsigned char> aFilteredLine(nLineLength);
for (size_t nEntry = 0; nEntry < nNumberOfObjects; ++nEntry)
{ {
size_t nIndex = nFirstObject + nEntry; size_t nFirstObject = aFirstObjects[nSubSection];
size_t nNumberOfObjects = aNumberOfObjects[nSubSection];
aStream.ReadBytes(aOrigLine.data(), aOrigLine.size()); // This is the line as read from the stream.
if (aOrigLine[0] + 10 != nPredictor) std::vector<unsigned char> aOrigLine(nLineLength);
// This is the line as it appears after tweaking according to nPredictor.
std::vector<unsigned char> aFilteredLine(nLineLength);
for (size_t nEntry = 0; nEntry < nNumberOfObjects; ++nEntry)
{ {
SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRefStream: in-stream predictor is inconsistent with /DecodeParms/Predictor for object #" << nIndex); size_t nIndex = nFirstObject + nEntry;
return;
}
for (int i = 0; i < nLineLength; ++i) aStream.ReadBytes(aOrigLine.data(), aOrigLine.size());
{ if (aOrigLine[0] + 10 != nPredictor)
switch (nPredictor)
{ {
case 1: SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRefStream: in-stream predictor is inconsistent with /DecodeParms/Predictor for object #" << nIndex);
// No prediction.
break;
case 12:
// PNG prediction: up (on all rows).
aFilteredLine[i] = aFilteredLine[i] + aOrigLine[i];
break;
default:
SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRefStream: unexpected predictor: " << nPredictor);
return; return;
break;
} }
}
// First character is already handled above. for (int i = 0; i < nLineLength; ++i)
int nPos = 1;
size_t nType = 0;
// Start of the current field in the stream data.
int nOffset = nPos;
for (; nPos < nOffset + aW[0]; ++nPos)
{
unsigned char nCh = aFilteredLine[nPos];
nType = (nType << 8) + nCh;
}
// Start of the object in the file stream.
size_t nStreamOffset = 0;
nOffset = nPos;
for (; nPos < nOffset + aW[1]; ++nPos)
{
unsigned char nCh = aFilteredLine[nPos];
nStreamOffset = (nStreamOffset << 8) + nCh;
}
// Generation number of the object.
size_t nGenerationNumber = 0;
nOffset = nPos;
for (; nPos < nOffset + aW[2]; ++nPos)
{
unsigned char nCh = aFilteredLine[nPos];
nGenerationNumber = (nGenerationNumber << 8) + nCh;
}
// Ignore invalid nType.
if (nType <= 2)
{
if (m_aXRef.find(nIndex) == m_aXRef.end())
{ {
XRefEntry aEntry; switch (nPredictor)
switch (nType)
{ {
case 0:
aEntry.m_eType = XRefEntryType::FREE;
break;
case 1: case 1:
aEntry.m_eType = XRefEntryType::NOT_COMPRESSED; // No prediction.
break; break;
case 2: case 12:
aEntry.m_eType = XRefEntryType::COMPRESSED; // PNG prediction: up (on all rows).
aFilteredLine[i] = aFilteredLine[i] + aOrigLine[i];
break;
default:
SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRefStream: unexpected predictor: " << nPredictor);
return;
break; break;
} }
aEntry.m_nOffset = nStreamOffset; }
aEntry.m_nGenerationNumber = nGenerationNumber;
m_aXRef[nIndex] = aEntry; // First character is already handled above.
int nPos = 1;
size_t nType = 0;
// Start of the current field in the stream data.
int nOffset = nPos;
for (; nPos < nOffset + aW[0]; ++nPos)
{
unsigned char nCh = aFilteredLine[nPos];
nType = (nType << 8) + nCh;
}
// Start of the object in the file stream.
size_t nStreamOffset = 0;
nOffset = nPos;
for (; nPos < nOffset + aW[1]; ++nPos)
{
unsigned char nCh = aFilteredLine[nPos];
nStreamOffset = (nStreamOffset << 8) + nCh;
}
// Generation number of the object.
size_t nGenerationNumber = 0;
nOffset = nPos;
for (; nPos < nOffset + aW[2]; ++nPos)
{
unsigned char nCh = aFilteredLine[nPos];
nGenerationNumber = (nGenerationNumber << 8) + nCh;
}
// Ignore invalid nType.
if (nType <= 2)
{
if (m_aXRef.find(nIndex) == m_aXRef.end())
{
XRefEntry aEntry;
switch (nType)
{
case 0:
aEntry.m_eType = XRefEntryType::FREE;
break;
case 1:
aEntry.m_eType = XRefEntryType::NOT_COMPRESSED;
break;
case 2:
aEntry.m_eType = XRefEntryType::COMPRESSED;
break;
}
aEntry.m_nOffset = nStreamOffset;
aEntry.m_nGenerationNumber = nGenerationNumber;
m_aXRef[nIndex] = aEntry;
}
} }
} }
} }