/* -*- 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 <map>
#include <memory>
#include <vector>

#include <comphelper/scopeguard.hxx>
#include <rtl/strbuf.hxx>
#include <rtl/string.hxx>
#include <sal/log.hxx>
#include <sal/types.h>

#ifdef XMLSEC_CRYPTO_NSS
#include <cert.h>
#include <cms.h>
#include <nss.h>
#include <sechash.h>
#endif

using namespace com::sun::star;

namespace xmlsecurity
{
namespace pdfio
{

class PDFTrailerElement;
class PDFObjectElement;

/// A one-liner comment.
class PDFCommentElement : public PDFElement
{
    OString m_aComment;

public:
    bool Read(SvStream& rStream) override;
};

/// Numbering object: an integer or a real.
class PDFNumberElement : public PDFElement
{
    double m_fValue;

public:
    bool Read(SvStream& rStream) override;
    double GetValue() const;
};

class PDFReferenceElement;

/// Indirect object: something with a unique ID.
class PDFObjectElement : public PDFElement
{
    PDFDocument& m_rDoc;
    double m_fObjectValue;
    double m_fGenerationValue;
    std::map<OString, PDFElement*> m_aDictionary;

public:
    PDFObjectElement(PDFDocument& rDoc, double fObjectValue, double fGenerationValue);
    bool Read(SvStream& rStream) override;
    PDFElement* Lookup(const OString& rDictionaryKey);
    PDFObjectElement* LookupObject(const OString& rDictionaryKey);
    double GetObjectValue() const;
    double GetGenerationValue() const;
};

/// Dictionary object: a set key-value pairs.
class PDFDictionaryElement : public PDFElement
{
public:
    bool Read(SvStream& rStream) override;

    static void Parse(const std::vector< std::unique_ptr<PDFElement> >& rElements, PDFElement* pThis, std::map<OString, PDFElement*>& rDictionary);
    static PDFElement* Lookup(const std::map<OString, PDFElement*>& rDictionary, const OString& rKey);
};

/// End of a dictionary: '>>'.
class PDFEndDictionaryElement : public PDFElement
{
public:
    bool Read(SvStream& rStream) override;
};

/// Name object: a key string.
class PDFNameElement : public PDFElement
{
    OString m_aValue;
public:
    bool Read(SvStream& rStream) override;
    const OString& GetValue() const;
};

/// Reference object: something with a unique ID.
class PDFReferenceElement : public PDFElement
{
    PDFDocument& m_rDoc;
    int m_fObjectValue;
    int m_fGenerationValue;

public:
    PDFReferenceElement(PDFDocument& rDoc, int fObjectValue, int fGenerationValue);
    bool Read(SvStream& rStream) override;
    /// Assuming the reference points to a number object, return its value.
    double LookupNumber(SvStream& rStream) const;
    /// Lookup referenced object, without assuming anything about its contents.
    PDFObjectElement* LookupObject() const;
};

/// Stream object: a byte array with a known length.
class PDFStreamElement : public PDFElement
{
    size_t m_nLength;

public:
    PDFStreamElement(size_t nLength);
    bool Read(SvStream& rStream) override;
};

/// End of a stream: 'endstream' keyword.
class PDFEndStreamElement : public PDFElement
{
public:
    bool Read(SvStream& rStream) override;
};

/// End of a object: 'endobj' keyword.
class PDFEndObjectElement : public PDFElement
{
public:
    bool Read(SvStream& rStream) override;
};

/// Array object: a list.
class PDFArrayElement : public PDFElement
{
    std::vector<PDFElement*> m_aElements;
public:
    bool Read(SvStream& rStream) override;
    void PushBack(PDFElement* pElement);
    const std::vector<PDFElement*>& GetElements();
};

/// End of an array: ']'.
class PDFEndArrayElement : public PDFElement
{
public:
    bool Read(SvStream& rStream) override;
};

/// Boolean object: a 'true' or a 'false'.
class PDFBooleanElement : public PDFElement
{
public:
    PDFBooleanElement(bool bValue);
    bool Read(SvStream& rStream) override;
};

/// Null object: the 'null' singleton.
class PDFNullElement : public PDFElement
{
public:
    bool Read(SvStream& rStream) override;
};

/// Hex string: in <AABB> form.
class PDFHexStringElement : public PDFElement
{
    OString m_aValue;
public:
    bool Read(SvStream& rStream) override;
    const OString& GetValue() const;
};

/// Literal string: in (asdf) form.
class PDFLiteralStringElement : public PDFElement
{
    OString m_aValue;
public:
    bool Read(SvStream& rStream) override;
};

/// The trailer signleton is at the end of the doc.
class PDFTrailerElement : public PDFElement
{
    PDFDocument& m_rDoc;
    std::map<OString, PDFElement*> m_aDictionary;

public:
    PDFTrailerElement(PDFDocument& rDoc);
    bool Read(SvStream& rStream) override;
    PDFElement* Lookup(const OString& rDictionaryKey);
};

PDFDocument::PDFDocument()
    : m_pTrailer(nullptr)
{
}

bool PDFDocument::Read(SvStream& rStream)
{
    // First look up the offset of the xref table.
    size_t nStartXRef = FindStartXRef(rStream);
    SAL_INFO("xmlsecurity.pdfio", "PDFDocument::Read: nStartXRef is " << nStartXRef);
    if (nStartXRef == 0)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::Read: found no xref statrt offset");
        return false;
    }
    rStream.Seek(nStartXRef);
    char ch;
    ReadXRef(rStream);

    // Then we can tokenize the stream.
    rStream.Seek(0);
    bool bInXRef = false;
    while (true)
    {
        rStream.ReadChar(ch);
        if (rStream.IsEof())
            break;

        switch (ch)
        {
        case '%':
        {
            m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFCommentElement()));
            rStream.SeekRel(-1);
            if (!m_aElements.back()->Read(rStream))
                return false;
            break;
        }
        case '<':
        {
            // Dictionary or hex string.
            rStream.ReadChar(ch);
            rStream.SeekRel(-2);
            if (ch == '<')
                m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFDictionaryElement()));
            else
                m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFHexStringElement()));
            if (!m_aElements.back()->Read(rStream))
                return false;
            break;
        }
        case '>':
        {
            m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFEndDictionaryElement()));
            rStream.SeekRel(-1);
            if (!m_aElements.back()->Read(rStream))
                return false;
            break;
        }
        case '[':
        {
            m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFArrayElement()));
            rStream.SeekRel(-1);
            if (!m_aElements.back()->Read(rStream))
                return false;
            break;
        }
        case ']':
        {
            m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFEndArrayElement()));
            rStream.SeekRel(-1);
            if (!m_aElements.back()->Read(rStream))
                return false;
            break;
        }
        case '/':
        {
            m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFNameElement()));
            rStream.SeekRel(-1);
            if (!m_aElements.back()->Read(rStream))
                return false;
            break;
        }
        case '(':
        {
            m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFLiteralStringElement()));
            rStream.SeekRel(-1);
            if (!m_aElements.back()->Read(rStream))
                return false;
            break;
        }
        default:
        {
            if (isdigit(ch) || ch == '-')
            {
                // Numbering object: an integer or a real.
                m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFNumberElement()));
                rStream.SeekRel(-1);
                if (!m_aElements.back()->Read(rStream))
                    return false;
            }
            else if (isalpha(ch))
            {
                // Possible keyword, like "obj".
                rStream.SeekRel(-1);
                OString aKeyword = ReadKeyword(rStream);

                bool bObj = aKeyword == "obj";
                if (bObj || aKeyword == "R")
                {
                    size_t nElements = m_aElements.size();
                    if (nElements < 2)
                    {
                        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::Read: expected at least two tokens before 'obj' or 'R' keyword");
                        return false;
                    }

                    auto pObjectNumber = dynamic_cast<PDFNumberElement*>(m_aElements[nElements - 2].get());
                    auto pGenerationNumber = dynamic_cast<PDFNumberElement*>(m_aElements[nElements - 1].get());
                    if (!pObjectNumber || !pGenerationNumber)
                    {
                        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::Read: missing object or generation number before 'obj' or 'R' keyword");
                        return false;
                    }

                    if (bObj)
                        m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFObjectElement(*this, pObjectNumber->GetValue(), pGenerationNumber->GetValue())));
                    else
                        m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFReferenceElement(*this, pObjectNumber->GetValue(), pGenerationNumber->GetValue())));
                    if (!m_aElements.back()->Read(rStream))
                        return false;
                }
                else if (aKeyword == "stream")
                {
                    // Look up the length of the stream from the parent object's dictionary.
                    size_t nLength = 0;
                    for (size_t nElement = 0; nElement < m_aElements.size(); ++nElement)
                    {
                        // Iterate in reverse order.
                        size_t nIndex = m_aElements.size() - nElement - 1;
                        PDFElement* pElement = m_aElements[nIndex].get();
                        auto pObjectElement = dynamic_cast<PDFObjectElement*>(pElement);
                        if (!pObjectElement)
                            continue;

                        PDFElement* pLookup = pObjectElement->Lookup("Length");
                        auto pReference = dynamic_cast<PDFReferenceElement*>(pLookup);
                        if (pReference)
                        {
                            // Length is provided as a reference.
                            nLength = pReference->LookupNumber(rStream);
                            break;
                        }

                        auto pNumber = dynamic_cast<PDFNumberElement*>(pLookup);
                        if (pNumber)
                        {
                            // Length is provided directly.
                            nLength = pNumber->GetValue();
                            break;
                        }

                        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::Read: found no Length key for stream keyword");
                        return false;
                    }

                    PDFDocument::SkipWhitespace(rStream);
                    m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFStreamElement(nLength)));
                    if (!m_aElements.back()->Read(rStream))
                        return false;
                }
                else if (aKeyword == "endstream")
                {
                    m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFEndStreamElement()));
                    if (!m_aElements.back()->Read(rStream))
                        return false;
                }
                else if (aKeyword == "endobj")
                {
                    m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFEndObjectElement()));
                    if (!m_aElements.back()->Read(rStream))
                        return false;
                }
                else if (aKeyword == "true" || aKeyword == "false")
                    m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFBooleanElement(aKeyword.toBoolean())));
                else if (aKeyword == "null")
                    m_aElements.push_back(std::unique_ptr<PDFElement>(new PDFNullElement()));
                else if (aKeyword == "xref")
                    // Allow 'f' and 'n' keywords.
                    bInXRef = true;
                else if (bInXRef && (aKeyword == "f" || aKeyword == "n"))
                {
                }
                else if (aKeyword == "trailer")
                {
                    m_pTrailer = new PDFTrailerElement(*this);
                    m_aElements.push_back(std::unique_ptr<PDFElement>(m_pTrailer));
                }
                else if (aKeyword == "startxref")
                {
                }
                else
                {
                    SAL_WARN("xmlsecurity.pdfio", "PDFDocument::Read: unexpected '" << aKeyword << "' keyword");
                    return false;
                }
            }
            else
            {
                if (!isspace(ch))
                {
                    SAL_WARN("xmlsecurity.pdfio", "PDFDocument::Read: unexpected character: " << ch);
                    return false;
                }
            }
            break;
        }
        }
    }

    return true;
}

OString PDFDocument::ReadKeyword(SvStream& rStream)
{
    OStringBuffer aBuf;
    char ch;
    rStream.ReadChar(ch);
    while (isalpha(ch))
    {
        aBuf.append(ch);
        rStream.ReadChar(ch);
        if (rStream.IsEof())
            break;
    }
    rStream.SeekRel(-1);
    return aBuf.toString();
}

size_t PDFDocument::FindStartXRef(SvStream& rStream)
{
    // Find the "startxref" token, somewhere near the end of the document.
    std::vector<char> aBuf(1024);
    rStream.Seek(STREAM_SEEK_TO_END);
    rStream.SeekRel(-1 * aBuf.size());
    size_t nBeforePeek = rStream.Tell();
    size_t nSize = rStream.ReadBytes(aBuf.data(), aBuf.size());
    rStream.Seek(nBeforePeek);
    if (nSize != aBuf.size())
        aBuf.resize(nSize);
    OString aPrefix("startxref");
    char* pOffset = strstr(aBuf.data(), aPrefix.getStr());
    if (!pOffset)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::FindStartXRef: found no startxref");
        return 0;
    }

    rStream.SeekRel(pOffset - aBuf.data() + aPrefix.getLength());
    if (rStream.IsEof())
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::FindStartXRef: unexpected end of stream after startxref");
        return 0;
    }

    PDFDocument::SkipWhitespace(rStream);
    PDFNumberElement aNumber;
    if (!aNumber.Read(rStream))
        return 0;
    return aNumber.GetValue();
}

void PDFDocument::ReadXRef(SvStream& rStream)
{
    if (ReadKeyword(rStream) != "xref")
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRef: xref is not the first keyword");
        return;
    }

    PDFDocument::SkipWhitespace(rStream);
    PDFNumberElement aFirstObject;
    if (!aFirstObject.Read(rStream))
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRef: failed to read first object number");
        return;
    }

    if (aFirstObject.GetValue() != 0)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRef: expected first object number == 0");
        return;
    }

    PDFDocument::SkipWhitespace(rStream);
    PDFNumberElement aNumberOfEntries;
    if (!aNumberOfEntries.Read(rStream))
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRef: failed to read number of entries");
        return;
    }

    if (aNumberOfEntries.GetValue() <= 0)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRef: expected one or more entries");
        return;
    }

    size_t nSize = aNumberOfEntries.GetValue();
    for (size_t nEntry = 0; nEntry < nSize; ++nEntry)
    {
        PDFDocument::SkipWhitespace(rStream);
        PDFNumberElement aOffset;
        if (!aOffset.Read(rStream))
        {
            SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRef: failed to read offset");
            return;
        }

        PDFDocument::SkipWhitespace(rStream);
        PDFNumberElement aGenerationNumber;
        if (!aGenerationNumber.Read(rStream))
        {
            SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRef: failed to read genration number");
            return;
        }

        PDFDocument::SkipWhitespace(rStream);
        OString aKeyword = ReadKeyword(rStream);
        if (aKeyword != "f" && aKeyword != "n")
        {
            SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ReadXRef: unexpected keyword");
            return;
        }
        m_aXRef.push_back(aOffset.GetValue());
    }
}

void PDFDocument::SkipWhitespace(SvStream& rStream)
{
    char ch = 0;

    while (true)
    {
        rStream.ReadChar(ch);
        if (rStream.IsEof())
            break;

        if (!isspace(ch))
        {
            rStream.SeekRel(-1);
            return;
        }
    }
}

size_t PDFDocument::GetObjectOffset(size_t nIndex) const
{
    if (nIndex >= m_aXRef.size())
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::GetObjectOffset: wanted to look up index #" << nIndex);
        return 0;
    }

    return m_aXRef[nIndex];
}

const std::vector< std::unique_ptr<PDFElement> >& PDFDocument::GetElements()
{
    return m_aElements;
}

std::vector<PDFObjectElement*> PDFDocument::GetPages()
{
    std::vector<PDFObjectElement*> aRet;

    if (!m_pTrailer)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::GetPages: found no trailer");
        return aRet;
    }

    auto pRoot = dynamic_cast<PDFReferenceElement*>(m_pTrailer->Lookup("Root"));
    if (!pRoot)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::GetPages: trailer has no Root key");
        return aRet;
    }

    PDFObjectElement* pCatalog = pRoot->LookupObject();
    if (!pCatalog)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::GetPages: trailer has no catalog");
        return aRet;
    }

    PDFObjectElement* pPages = pCatalog->LookupObject("Pages");
    if (!pPages)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::GetPages: catalog has no pages");
        return aRet;
    }

    auto pKids = dynamic_cast<PDFArrayElement*>(pPages->Lookup("Kids"));
    if (!pKids)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::GetPages: pages has no kids");
        return aRet;
    }

    for (const auto& pKid : pKids->GetElements())
    {
        auto pReference = dynamic_cast<PDFReferenceElement*>(pKid);
        if (!pReference)
            continue;

        aRet.push_back(pReference->LookupObject());
    }

    return aRet;
}

std::vector<PDFObjectElement*> PDFDocument::GetSignatureWidgets()
{
    std::vector<PDFObjectElement*> aRet;

    std::vector<PDFObjectElement*> aPages = GetPages();

    for (const auto& pPage : aPages)
    {
        auto pAnnots = dynamic_cast<PDFArrayElement*>(pPage->Lookup("Annots"));
        if (!pAnnots)
            continue;

        for (const auto& pAnnot : pAnnots->GetElements())
        {
            auto pReference = dynamic_cast<PDFReferenceElement*>(pAnnot);
            if (!pReference)
                continue;

            PDFObjectElement* pAnnotObject = pReference->LookupObject();
            if (!pAnnotObject)
                continue;

            auto pFT = dynamic_cast<PDFNameElement*>(pAnnotObject->Lookup("FT"));
            if (!pFT || pFT->GetValue() != "Sig")
                continue;

            aRet.push_back(pAnnotObject);
        }
    }

    return aRet;
}

int PDFDocument::AsHex(char ch)
{
    int nRet = 0;
    if (isdigit(ch))
        nRet = ch - '0';
    else
    {
        if (ch >= 'a' && ch <= 'f')
            nRet = ch - 'a';
        else if (ch >= 'A' && ch <= 'F')
            nRet = ch - 'A';
        else
            return -1;
        nRet += 10;
    }
    return nRet;
}

bool PDFDocument::ValidateSignature(SvStream& rStream, PDFObjectElement* pSignature, bool& bDigestMatch)
{
    PDFObjectElement* pValue = pSignature->LookupObject("V");
    if (!pValue)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: no value");
        return false;
    }

    auto pContents = dynamic_cast<PDFHexStringElement*>(pValue->Lookup("Contents"));
    if (!pContents)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: no contents");
        return false;
    }

    auto pByteRange = dynamic_cast<PDFArrayElement*>(pValue->Lookup("ByteRange"));
    if (!pByteRange || pByteRange->GetElements().size() < 2)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: no byte range or too few elements");
        return false;
    }

    auto pSubFilter = dynamic_cast<PDFNameElement*>(pValue->Lookup("SubFilter"));
    if (!pSubFilter || pSubFilter->GetValue() != "adbe.pkcs7.detached")
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: no or unsupported sub-filter");
        return false;
    }

    // At this point there is no obviously missing info to validate the
    // signature, so let's turn the hex dump of the signature into a memory
    // stream.
    const OString& rSignatureHex = pContents->GetValue();
    size_t nSignatureHexLen = rSignatureHex.getLength();
    std::vector<unsigned char> aSignature;
    {
        int nByte = 0;
        int nCount = 2;
        for (size_t i = 0; i < nSignatureHexLen; ++i)
        {
            nByte = nByte << 4;
            sal_Int8 nParsed = AsHex(rSignatureHex[i]);
            if (nParsed == -1)
            {
                SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: invalid hex value");
                return false;
            }
            nByte += nParsed;
            --nCount;
            if (!nCount)
            {
                aSignature.push_back(nByte);
                nCount = 2;
                nByte = 0;
            }
        }
    }

#ifdef XMLSEC_CRYPTO_NSS
    // Validate the signature. No need to call NSS_Init() here, assume that the
    // caller did that already.

    SECItem aSignatureItem;
    aSignatureItem.data = aSignature.data();
    aSignatureItem.len = aSignature.size();
    NSSCMSMessage* pCMSMessage = NSS_CMSMessage_CreateFromDER(&aSignatureItem,
                                 /*cb=*/nullptr,
                                 /*cb_arg=*/nullptr,
                                 /*pwfn=*/nullptr,
                                 /*pwfn_arg=*/nullptr,
                                 /*decrypt_key_cb=*/nullptr,
                                 /*decrypt_key_cb_arg=*/nullptr);
    if (!NSS_CMSMessage_IsSigned(pCMSMessage))
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: message is not signed");
        return false;
    }

    NSSCMSContentInfo* pCMSContentInfo = NSS_CMSMessage_ContentLevel(pCMSMessage, 0);
    if (!pCMSContentInfo)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: NSS_CMSMessage_ContentLevel() failed");
        return false;
    }

    NSSCMSSignedData* pCMSSignedData = static_cast<NSSCMSSignedData*>(NSS_CMSContentInfo_GetContent(pCMSContentInfo));
    if (!pCMSSignedData)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: NSS_CMSContentInfo_GetContent() failed");
        return false;
    }

    NSSCMSSignerInfo* pCMSSignerInfo = NSS_CMSSignedData_GetSignerInfo(pCMSSignedData, 0);
    if (!pCMSSignerInfo)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: NSS_CMSSignedData_GetSignerInfo() failed");
        return false;
    }

    SECItem aAlgorithm = NSS_CMSSignedData_GetDigestAlgs(pCMSSignedData)[0]->algorithm;
    HASH_HashType eHashType = HASH_GetHashTypeByOidTag(SECOID_FindOIDTag(&aAlgorithm));
    HASHContext* pHASHContext = HASH_Create(eHashType);
    if (!pHASHContext)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: HASH_Create() failed");
        return false;
    }

    // We have a hash, update it with the byte ranges.
    size_t nByteRangeOffset = 0;
    const std::vector<PDFElement*>& rByteRangeElements = pByteRange->GetElements();
    for (size_t i = 0; i < rByteRangeElements.size(); ++i)
    {
        auto pNumber = dynamic_cast<PDFNumberElement*>(rByteRangeElements[i]);
        if (!pNumber)
        {
            SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: signature offset and length has to be a number");
            return false;
        }

        if (i % 2 == 0)
        {
            nByteRangeOffset = pNumber->GetValue();
            continue;
        }

        rStream.Seek(nByteRangeOffset);
        size_t nByteRangeLength = pNumber->GetValue();

        // And now hash this byte range.
        const int nChunkLen = 4096;
        std::vector<unsigned char> aBuffer(nChunkLen);
        for (size_t nByte = 0; nByte < nByteRangeLength;)
        {
            size_t nRemainingSize = nByteRangeLength - nByte;
            if (nRemainingSize < nChunkLen)
            {
                rStream.ReadBytes(aBuffer.data(), nRemainingSize);
                HASH_Update(pHASHContext, aBuffer.data(), nRemainingSize);
                nByte = nByteRangeLength;
            }
            else
            {
                rStream.ReadBytes(aBuffer.data(), nChunkLen);
                HASH_Update(pHASHContext, aBuffer.data(), nChunkLen);
                nByte += nChunkLen;
            }
        }
    }

    // Find out what is the expected length of the hash.
    unsigned int nMaxResultLen = 0;
    switch (SECOID_FindOIDTag(&aAlgorithm))
    {
    case SEC_OID_SHA1:
        nMaxResultLen = 20;
        break;
    default:
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: unrecognized algorithm");
        return false;
    }

    auto pActualResultBuffer = static_cast<unsigned char*>(PORT_Alloc(nMaxResultLen));
    unsigned int nActualResultLen;
    HASH_End(pHASHContext, pActualResultBuffer, &nActualResultLen, nMaxResultLen);

    if (!NSS_CMSSignerInfo_GetSigningCertificate(pCMSSignerInfo, CERT_GetDefaultCertDB()))
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: NSS_CMSSignerInfo_GetSigningCertificate() failed");
        return false;
    }

    SECItem* pContentInfoContentData = pCMSSignedData->contentInfo.content.data;
    if (pContentInfoContentData && pContentInfoContentData->data)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDocument::ValidateSignature: expected nullptr content info");
        return false;
    }

    SECItem aActualResultItem;
    aActualResultItem.data = pActualResultBuffer;
    aActualResultItem.len = nActualResultLen;
    bDigestMatch = NSS_CMSSignerInfo_Verify(pCMSSignerInfo, &aActualResultItem, nullptr) == SECSuccess;

    // Everything went fine
    PORT_Free(pActualResultBuffer);
    HASH_Destroy(pHASHContext);
    NSS_CMSSignerInfo_Destroy(pCMSSignerInfo);

    return true;
#else
    // Not implemented.
    (void)rStream;
    (void)bDigestMatch;

    return false;
#endif
}

bool PDFCommentElement::Read(SvStream& rStream)
{
    // Read from (including) the % char till (excluding) the end of the line.
    OStringBuffer aBuf;
    char ch;
    rStream.ReadChar(ch);
    while (!rStream.IsEof())
    {
        if (ch == 0x0a)
        {
            m_aComment = aBuf.makeStringAndClear();
            SAL_INFO("xmlsecurity.pdfio", "PDFCommentElement::Read: m_aComment is '" << m_aComment << "'");
            return true;
        }
        aBuf.append(ch);
        rStream.ReadChar(ch);
    }

    return false;
}

bool PDFNumberElement::Read(SvStream& rStream)
{
    OStringBuffer aBuf;
    char ch;
    rStream.ReadChar(ch);
    while (!rStream.IsEof())
    {
        if (!isdigit(ch) && ch != '-')
        {
            rStream.SeekRel(-1);
            m_fValue = aBuf.makeStringAndClear().toDouble();
            SAL_INFO("xmlsecurity.pdfio", "PDFNumberElement::Read: m_fValue is '" << m_fValue << "'");
            return true;
        }
        aBuf.append(ch);
        rStream.ReadChar(ch);
    }

    return false;
}

PDFBooleanElement::PDFBooleanElement(bool /*bValue*/)
{
}

bool PDFBooleanElement::Read(SvStream& /*rStream*/)
{
    return true;
}

bool PDFNullElement::Read(SvStream& /*rStream*/)
{
    return true;
}

bool PDFHexStringElement::Read(SvStream& rStream)
{
    char ch;
    rStream.ReadChar(ch);
    if (ch != '<')
    {
        SAL_INFO("xmlsecurity.pdfio", "PDFHexStringElement::Read: expected '<' as first character");
        return false;
    }
    rStream.ReadChar(ch);

    OStringBuffer aBuf;
    while (!rStream.IsEof())
    {
        if (ch == '>')
        {
            m_aValue = aBuf.makeStringAndClear();
            SAL_INFO("xmlsecurity.pdfio", "PDFHexStringElement::Read: m_aValue length is " << m_aValue.getLength());
            return true;
        }
        aBuf.append(ch);
        rStream.ReadChar(ch);
    }

    return false;
}

const OString& PDFHexStringElement::GetValue() const
{
    return m_aValue;
}

bool PDFLiteralStringElement::Read(SvStream& rStream)
{
    char ch;
    rStream.ReadChar(ch);
    if (ch != '(')
    {
        SAL_INFO("xmlsecurity.pdfio", "PDFHexStringElement::Read: expected '(' as first character");
        return false;
    }
    rStream.ReadChar(ch);

    OStringBuffer aBuf;
    while (!rStream.IsEof())
    {
        if (ch == ')')
        {
            m_aValue = aBuf.makeStringAndClear();
            SAL_INFO("xmlsecurity.pdfio", "PDFLiteralStringElement::Read: m_aValue is '" << m_aValue << "'");
            return true;
        }
        aBuf.append(ch);
        rStream.ReadChar(ch);
    }

    return false;
}

PDFTrailerElement::PDFTrailerElement(PDFDocument& rDoc)
    : m_rDoc(rDoc)
{
}

bool PDFTrailerElement::Read(SvStream& /*rStream*/)
{
    return true;
}

PDFElement* PDFTrailerElement::Lookup(const OString& rDictionaryKey)
{
    if (m_aDictionary.empty())
        PDFDictionaryElement::Parse(m_rDoc.GetElements(), this, m_aDictionary);

    return PDFDictionaryElement::Lookup(m_aDictionary, rDictionaryKey);
}


double PDFNumberElement::GetValue() const
{
    return m_fValue;
}

PDFObjectElement::PDFObjectElement(PDFDocument& rDoc, double fObjectValue, double fGenerationValue)
    : m_rDoc(rDoc),
      m_fObjectValue(fObjectValue),
      m_fGenerationValue(fGenerationValue)
{
}

bool PDFObjectElement::Read(SvStream& /*rStream*/)
{
    SAL_INFO("xmlsecurity.pdfio", "PDFObjectElement::Read: " << m_fObjectValue << " " << m_fGenerationValue << " obj");
    return true;
}

void PDFDictionaryElement::Parse(const std::vector< std::unique_ptr<PDFElement> >& rElements, PDFElement* pThis, std::map<OString, PDFElement*>& rDictionary)
{
    if (!rDictionary.empty())
        return;

    // Find out where the dictionary for this object starts.
    size_t nIndex = 0;
    for (size_t i = 0; i < rElements.size(); ++i)
    {
        if (rElements[i].get() == pThis)
        {
            nIndex = i;
            break;
        }
    }

    OString aName;
    std::vector<PDFNumberElement*> aNumbers;
    // The array value we're in -- if any.
    PDFArrayElement* pArray = nullptr;
    for (size_t i = nIndex; i < rElements.size(); ++i)
    {
        auto pName = dynamic_cast<PDFNameElement*>(rElements[i].get());
        if (pName)
        {
            if (!aNumbers.empty())
            {
                rDictionary[aName] = aNumbers.back();
                aName.clear();
                aNumbers.clear();
            }

            if (aName.isEmpty())
            {
                // Remember key.
                aName = pName->GetValue();
            }
            else
            {
                // Name-name key-value.
                rDictionary[aName] = pName;
                aName.clear();
            }
            continue;
        }

        auto pArr = dynamic_cast<PDFArrayElement*>(rElements[i].get());
        if (pArr)
        {
            pArray = pArr;
            continue;
        }

        if (pArray && dynamic_cast<PDFEndArrayElement*>(rElements[i].get()))
        {
            if (!aNumbers.empty())
            {
                for (auto& pNumber : aNumbers)
                    pArray->PushBack(pNumber);
                aNumbers.clear();
            }
            rDictionary[aName] = pArray;
            aName.clear();
            pArray = nullptr;
            continue;
        }

        auto pReference = dynamic_cast<PDFReferenceElement*>(rElements[i].get());
        if (pReference)
        {
            if (!pArray)
            {
                rDictionary[aName] = pReference;
                aName.clear();
            }
            else
            {
                pArray->PushBack(pReference);
            }
            aNumbers.clear();
            continue;
        }

        auto pLiteralString = dynamic_cast<PDFLiteralStringElement*>(rElements[i].get());
        if (pLiteralString)
        {
            rDictionary[aName] = pLiteralString;
            aName.clear();
            continue;
        }

        auto pHexString = dynamic_cast<PDFHexStringElement*>(rElements[i].get());
        if (pHexString)
        {
            rDictionary[aName] = pHexString;
            aName.clear();
            continue;
        }

        if (dynamic_cast<PDFEndDictionaryElement*>(rElements[i].get()))
            break;

        if (dynamic_cast<PDFEndObjectElement*>(rElements[i].get()))
            break;

        // Just remember this, so that in case it's not a reference parameter,
        // we can handle it later.
        auto pNumber = dynamic_cast<PDFNumberElement*>(rElements[i].get());
        if (pNumber)
            aNumbers.push_back(pNumber);
    }

    if (!aNumbers.empty())
    {
        rDictionary[aName] = aNumbers.back();
        aName.clear();
        aNumbers.clear();
    }
}

PDFElement* PDFDictionaryElement::Lookup(const std::map<OString, PDFElement*>& rDictionary, const OString& rKey)
{
    auto it = rDictionary.find(rKey);
    if (it == rDictionary.end())
        return nullptr;

    return it->second;
}

PDFElement* PDFObjectElement::Lookup(const OString& rDictionaryKey)
{
    if (m_aDictionary.empty())
        PDFDictionaryElement::Parse(m_rDoc.GetElements(), this, m_aDictionary);

    return PDFDictionaryElement::Lookup(m_aDictionary, rDictionaryKey);
}

PDFObjectElement* PDFObjectElement::LookupObject(const OString& rDictionaryKey)
{
    auto pKey = dynamic_cast<PDFReferenceElement*>(Lookup(rDictionaryKey));
    if (!pKey)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFObjectElement::LookupObject: no such key with reference value: " << rDictionaryKey);
        return nullptr;
    }

    return pKey->LookupObject();
}

double PDFObjectElement::GetObjectValue() const
{
    return m_fObjectValue;
}

double PDFObjectElement::GetGenerationValue() const
{
    return m_fGenerationValue;
}

PDFReferenceElement::PDFReferenceElement(PDFDocument& rDoc, int fObjectValue, int fGenerationValue)
    : m_rDoc(rDoc),
      m_fObjectValue(fObjectValue),
      m_fGenerationValue(fGenerationValue)
{
}

bool PDFReferenceElement::Read(SvStream& /*rStream*/)
{
    SAL_INFO("xmlsecurity.pdfio", "PDFReferenceElement::Read: " << m_fObjectValue << " " << m_fGenerationValue << " R");
    return true;
}

double PDFReferenceElement::LookupNumber(SvStream& rStream) const
{
    size_t nOffset = m_rDoc.GetObjectOffset(m_fObjectValue);
    if (nOffset == 0)
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFReferenceElement::LookupNumber: found no offset for object #" << m_fObjectValue);
        return 0;
    }

    sal_uInt64 nOrigPos = rStream.Tell();
    comphelper::ScopeGuard g([&]()
    {
        rStream.Seek(nOrigPos);
    });

    rStream.Seek(nOffset);
    {
        PDFDocument::SkipWhitespace(rStream);
        PDFNumberElement aNumber;
        bool bRet = aNumber.Read(rStream);
        if (!bRet || aNumber.GetValue() != m_fObjectValue)
        {
            SAL_WARN("xmlsecurity.pdfio", "PDFReferenceElement::LookupNumber: offset points to not matching object");
            return 0;
        }
    }

    {
        PDFDocument::SkipWhitespace(rStream);
        PDFNumberElement aNumber;
        bool bRet = aNumber.Read(rStream);
        if (!bRet || aNumber.GetValue() != m_fGenerationValue)
        {
            SAL_WARN("xmlsecurity.pdfio", "PDFReferenceElement::LookupNumber: offset points to not matching generation");
            return 0;
        }
    }

    {
        PDFDocument::SkipWhitespace(rStream);
        OString aKeyword = PDFDocument::ReadKeyword(rStream);
        if (aKeyword != "obj")
        {
            SAL_WARN("xmlsecurity.pdfio", "PDFReferenceElement::LookupNumber: offset doesn't point to an obj keyword");
            return 0;
        }
    }

    PDFDocument::SkipWhitespace(rStream);
    PDFNumberElement aNumber;
    if (!aNumber.Read(rStream))
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFReferenceElement::LookupNumber: failed to read referenced number");
        return 0;
    }

    return aNumber.GetValue();
}

PDFObjectElement* PDFReferenceElement::LookupObject() const
{
    const std::vector< std::unique_ptr<PDFElement> >& rElements = m_rDoc.GetElements();
    for (const auto& rElement : rElements)
    {
        auto* pObjectElement = dynamic_cast<PDFObjectElement*>(rElement.get());
        if (!pObjectElement)
            continue;

        if (pObjectElement->GetObjectValue() != m_fObjectValue)
            continue;

        if (pObjectElement->GetGenerationValue() != m_fGenerationValue)
            continue;

        return pObjectElement;
    }

    return nullptr;
}

bool PDFDictionaryElement::Read(SvStream& rStream)
{
    char ch;
    rStream.ReadChar(ch);
    if (ch != '<')
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDictionaryElement::Read: unexpected character: " << ch);
        return false;
    }

    if (rStream.IsEof())
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDictionaryElement::Read: unexpected end of file");
        return false;
    }

    rStream.ReadChar(ch);
    if (ch != '<')
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFDictionaryElement::Read: unexpected character: " << ch);
        return false;
    }

    SAL_INFO("xmlsecurity.pdfio", "PDFDictionaryElement::Read: '<<'");

    return true;
}

bool PDFEndDictionaryElement::Read(SvStream& rStream)
{
    char ch;
    rStream.ReadChar(ch);
    if (ch != '>')
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFEndDictionaryElement::Read: unexpected character: " << ch);
        return false;
    }

    if (rStream.IsEof())
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFEndDictionaryElement::Read: unexpected end of file");
        return false;
    }

    rStream.ReadChar(ch);
    if (ch != '>')
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFEndDictionaryElement::Read: unexpected character: " << ch);
        return false;
    }

    SAL_INFO("xmlsecurity.pdfio", "PDFEndDictionaryElement::Read: '>>'");

    return true;
}

bool PDFNameElement::Read(SvStream& rStream)
{
    char ch;
    rStream.ReadChar(ch);
    if (ch != '/')
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFNameElement::Read: unexpected character: " << ch);
        return false;
    }

    if (rStream.IsEof())
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFNameElement::Read: unexpected end of file");
        return false;
    }

    // Read till the first white-space.
    OStringBuffer aBuf;
    rStream.ReadChar(ch);
    while (!rStream.IsEof())
    {
        if (isspace(ch) || ch == '/' || ch == '[' || ch == '<' || ch == '(')
        {
            rStream.SeekRel(-1);
            m_aValue = aBuf.makeStringAndClear();
            SAL_INFO("xmlsecurity.pdfio", "PDFNameElement::Read: m_aValue is '" << m_aValue << "'");
            return true;
        }
        aBuf.append(ch);
        rStream.ReadChar(ch);
    }

    return false;
}

const OString& PDFNameElement::GetValue() const
{
    return m_aValue;
}

PDFStreamElement::PDFStreamElement(size_t nLength)
    : m_nLength(nLength)
{
}

bool PDFStreamElement::Read(SvStream& rStream)
{
    SAL_INFO("xmlsecurity.pdfio", "PDFStreamElement::Read: length is " << m_nLength);
    rStream.SeekRel(m_nLength);

    return rStream.good();
}

bool PDFEndStreamElement::Read(SvStream& /*rStream*/)
{
    return true;
}

bool PDFEndObjectElement::Read(SvStream& /*rStream*/)
{
    return true;
}

bool PDFArrayElement::Read(SvStream& rStream)
{
    char ch;
    rStream.ReadChar(ch);
    if (ch != '[')
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFArrayElement::Read: unexpected character: " << ch);
        return false;
    }

    SAL_INFO("xmlsecurity.pdfio", "PDFArrayElement::Read: '['");

    return true;
}

void PDFArrayElement::PushBack(PDFElement* pElement)
{
    m_aElements.push_back(pElement);
}

const std::vector<PDFElement*>& PDFArrayElement::GetElements()
{
    return m_aElements;
}

bool PDFEndArrayElement::Read(SvStream& rStream)
{
    char ch;
    rStream.ReadChar(ch);
    if (ch != ']')
    {
        SAL_WARN("xmlsecurity.pdfio", "PDFEndArrayElement::Read: unexpected character: " << ch);
        return false;
    }

    SAL_INFO("xmlsecurity.pdfio", "PDFEndArrayElement::Read: ']'");

    return true;
}


} // namespace pdfio
} // namespace xmlsecurity

/* vim:set shiftwidth=4 softtabstop=4 expandtab: */