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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
#include <pdfio/pdfdocument.hxx>
#include <memory>
#include <vector>
#include <rtl/string.hxx>
#include <rtl/ustrbuf.hxx>
#include <sal/log.hxx>
#include <sal/types.h>
#include <svl/sigstruct.hxx>
#include <svl/cryptosign.hxx>
#include <vcl/filter/pdfdocument.hxx>
using namespace com::sun::star;
namespace xmlsecurity
{
namespace pdfio
{
bool ValidateSignature(SvStream& rStream, vcl::filter::PDFObjectElement* pSignature,
SignatureInformation& rInformation, bool bLast)
{
vcl::filter::PDFObjectElement* pValue = pSignature->LookupObject("V");
if (!pValue)
{
SAL_WARN("xmlsecurity.pdfio", "ValidateSignature: no value");
return false;
}
auto pContents = dynamic_cast<vcl::filter::PDFHexStringElement*>(pValue->Lookup("Contents"));
if (!pContents)
{
SAL_WARN("xmlsecurity.pdfio", "ValidateSignature: no contents");
return false;
}
auto pByteRange = dynamic_cast<vcl::filter::PDFArrayElement*>(pValue->Lookup("ByteRange"));
if (!pByteRange || pByteRange->GetElements().size() < 2)
{
SAL_WARN("xmlsecurity.pdfio", "ValidateSignature: no byte range or too few elements");
return false;
}
auto pSubFilter = dynamic_cast<vcl::filter::PDFNameElement*>(pValue->Lookup("SubFilter"));
const bool bNonDetached = pSubFilter && pSubFilter->GetValue() == "adbe.pkcs7.sha1";
if (!pSubFilter
|| (pSubFilter->GetValue() != "adbe.pkcs7.detached" && !bNonDetached
&& pSubFilter->GetValue() != "ETSI.CAdES.detached"))
{
if (!pSubFilter)
SAL_WARN("xmlsecurity.pdfio", "ValidateSignature: missing sub-filter");
else
SAL_WARN("xmlsecurity.pdfio", "ValidateSignature: unsupported sub-filter: '"
<< pSubFilter->GetValue() << "'");
return false;
}
// Reason / comment / description is optional.
auto pReason = dynamic_cast<vcl::filter::PDFHexStringElement*>(pValue->Lookup("Reason"));
if (pReason)
{
// See appendUnicodeTextString() for the export equivalent of this.
std::vector<unsigned char> aReason = vcl::filter::PDFDocument::DecodeHexString(pReason);
OUStringBuffer aBuffer;
sal_uInt16 nByte = 0;
for (size_t i = 0; i < aReason.size(); ++i)
{
if (i % 2 == 0)
nByte = aReason[i];
else
{
sal_Unicode nUnicode;
nUnicode = (nByte << 8);
nUnicode |= aReason[i];
aBuffer.append(nUnicode);
}
}
if (!aBuffer.isEmpty())
rInformation.ouDescription = aBuffer.makeStringAndClear();
}
// Date: used only when the time of signing is not available in the
// signature.
auto pM = dynamic_cast<vcl::filter::PDFLiteralStringElement*>(pValue->Lookup("M"));
if (pM)
{
// Example: "D:20161027100104".
const OString& rM = pM->GetValue();
if (rM.startsWith("D:") && rM.getLength() >= 16)
{
rInformation.stDateTime.Year = rM.copy(2, 4).toInt32();
rInformation.stDateTime.Month = rM.copy(6, 2).toInt32();
rInformation.stDateTime.Day = rM.copy(8, 2).toInt32();
rInformation.stDateTime.Hours = rM.copy(10, 2).toInt32();
rInformation.stDateTime.Minutes = rM.copy(12, 2).toInt32();
rInformation.stDateTime.Seconds = rM.copy(14, 2).toInt32();
}
}
// Build a list of offset-length pairs, representing the signed bytes.
std::vector<std::pair<size_t, size_t>> aByteRanges;
size_t nByteRangeOffset = 0;
const std::vector<vcl::filter::PDFElement*>& rByteRangeElements = pByteRange->GetElements();
for (size_t i = 0; i < rByteRangeElements.size(); ++i)
{
auto pNumber = dynamic_cast<vcl::filter::PDFNumberElement*>(rByteRangeElements[i]);
if (!pNumber)
{
SAL_WARN("xmlsecurity.pdfio",
"ValidateSignature: signature offset and length has to be a number");
return false;
}
if (i % 2 == 0)
{
nByteRangeOffset = pNumber->GetValue();
continue;
}
size_t nByteRangeLength = pNumber->GetValue();
aByteRanges.emplace_back(nByteRangeOffset, nByteRangeLength);
}
// Detect if the byte ranges don't cover everything, but the signature itself.
if (aByteRanges.size() < 2)
{
SAL_WARN("xmlsecurity.pdfio", "ValidateSignature: expected 2 byte ranges");
return false;
}
if (aByteRanges[0].first != 0)
{
SAL_WARN("xmlsecurity.pdfio", "ValidateSignature: first range start is not 0");
return false;
}
// 2 is the leading "<" and the trailing ">" around the hex string.
size_t nSignatureLength = static_cast<size_t>(pContents->GetValue().getLength()) + 2;
if (aByteRanges[1].first != (aByteRanges[0].second + nSignatureLength))
{
SAL_WARN("xmlsecurity.pdfio",
"ValidateSignature: second range start is not the end of the signature");
return false;
}
rStream.Seek(STREAM_SEEK_TO_END);
size_t nFileEnd = rStream.Tell();
if (bLast && (aByteRanges[1].first + aByteRanges[1].second) != nFileEnd)
// Second range end is not the end of the file.
rInformation.bPartialDocumentSignature = true;
// At this point there is no obviously missing info to validate the
// signature.
std::vector<unsigned char> aSignature = vcl::filter::PDFDocument::DecodeHexString(pContents);
if (aSignature.empty())
{
SAL_WARN("xmlsecurity.pdfio", "ValidateSignature: empty contents");
return false;
}
return svl::crypto::Signing::Verify(rStream, aByteRanges, bNonDetached, aSignature,
rInformation);
}
} // namespace pdfio
} // namespace xmlsecurity
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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