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// Copyright 2016 PDFium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
#include "core/fpdfapi/parser/cpdf_hint_tables.h"
#include <limits>
#include "core/fpdfapi/parser/cpdf_array.h"
#include "core/fpdfapi/parser/cpdf_data_avail.h"
#include "core/fpdfapi/parser/cpdf_dictionary.h"
#include "core/fpdfapi/parser/cpdf_document.h"
#include "core/fpdfapi/parser/cpdf_linearized_header.h"
#include "core/fpdfapi/parser/cpdf_read_validator.h"
#include "core/fpdfapi/parser/cpdf_stream.h"
#include "core/fpdfapi/parser/cpdf_stream_acc.h"
#include "core/fpdfapi/parser/cpdf_syntax_parser.h"
#include "core/fxcrt/cfx_bitstream.h"
#include "core/fxcrt/fx_safe_types.h"
#include "third_party/base/check.h"
#include "third_party/base/numerics/safe_conversions.h"
#include "third_party/base/span.h"
namespace {
bool CanReadFromBitStream(const CFX_BitStream* hStream,
const FX_SAFE_UINT32& bits) {
return bits.IsValid() && hStream->BitsRemaining() >= bits.ValueOrDie();
}
// Sanity check values from the page table header. The note in the PDF 1.7
// reference for Table F.3 says the valid range is only 0 through 32. Though 0
// is not useful either.
bool IsValidPageOffsetHintTableBitCount(uint32_t bits) {
return bits > 0 && bits <= 32;
}
} // namespace
CPDF_HintTables::PageInfo::PageInfo() = default;
CPDF_HintTables::PageInfo::~PageInfo() = default;
// static
std::unique_ptr<CPDF_HintTables> CPDF_HintTables::Parse(
CPDF_SyntaxParser* parser,
const CPDF_LinearizedHeader* pLinearized) {
DCHECK(parser);
if (!pLinearized || pLinearized->GetPageCount() <= 1 ||
!pLinearized->HasHintTable()) {
return nullptr;
}
const FX_FILESIZE szHintStart = pLinearized->GetHintStart();
const uint32_t szHintLength = pLinearized->GetHintLength();
if (!parser->GetValidator()->CheckDataRangeAndRequestIfUnavailable(
szHintStart, szHintLength)) {
return nullptr;
}
parser->SetPos(szHintStart);
RetainPtr<CPDF_Stream> hints_stream = ToStream(
parser->GetIndirectObject(nullptr, CPDF_SyntaxParser::ParseType::kLoose));
if (!hints_stream)
return nullptr;
auto pHintTables = std::make_unique<CPDF_HintTables>(
parser->GetValidator().Get(), pLinearized);
if (!pHintTables->LoadHintStream(hints_stream.Get()))
return nullptr;
return pHintTables;
}
CPDF_HintTables::CPDF_HintTables(CPDF_ReadValidator* pValidator,
const CPDF_LinearizedHeader* pLinearized)
: m_pValidator(pValidator), m_pLinearized(pLinearized) {
DCHECK(m_pLinearized);
}
CPDF_HintTables::~CPDF_HintTables() = default;
bool CPDF_HintTables::ReadPageHintTable(CFX_BitStream* hStream) {
const uint32_t nPages = m_pLinearized->GetPageCount();
if (nPages < 1 || nPages >= CPDF_Document::kPageMaxNum)
return false;
const uint32_t nFirstPageNum = m_pLinearized->GetFirstPageNo();
if (nFirstPageNum >= nPages)
return false;
if (!hStream || hStream->IsEOF())
return false;
const uint32_t kHeaderSize = 288;
if (hStream->BitsRemaining() < kHeaderSize)
return false;
// Item 1: The least number of objects in a page.
const uint32_t dwObjLeastNum = hStream->GetBits(32);
if (!dwObjLeastNum)
return false;
// Item 2: The location of the first page's page object.
const FX_FILESIZE szFirstObjLoc =
HintsOffsetToFileOffset(hStream->GetBits(32));
if (!szFirstObjLoc)
return false;
m_szFirstPageObjOffset = szFirstObjLoc;
// Item 3: The number of bits needed to represent the difference
// between the greatest and least number of objects in a page.
const uint32_t dwDeltaObjectsBits = hStream->GetBits(16);
if (!IsValidPageOffsetHintTableBitCount(dwDeltaObjectsBits))
return false;
// Item 4: The least length of a page in bytes.
const uint32_t dwPageLeastLen = hStream->GetBits(32);
if (!dwPageLeastLen)
return false;
// Item 5: The number of bits needed to represent the difference
// between the greatest and least length of a page, in bytes.
const uint32_t dwDeltaPageLenBits = hStream->GetBits(16);
if (!IsValidPageOffsetHintTableBitCount(dwDeltaPageLenBits))
return false;
// Skip Item 6, 7, 8, 9 total 96 bits.
hStream->SkipBits(96);
// Item 10: The number of bits needed to represent the greatest
// number of shared object references.
const uint32_t dwSharedObjBits = hStream->GetBits(16);
if (!IsValidPageOffsetHintTableBitCount(dwSharedObjBits))
return false;
// Item 11: The number of bits needed to represent the numerically
// greatest shared object identifier used by the pages.
const uint32_t dwSharedIdBits = hStream->GetBits(16);
if (!IsValidPageOffsetHintTableBitCount(dwSharedIdBits))
return false;
// Item 12: The number of bits needed to represent the numerator of
// the fractional position for each shared object reference. For each
// shared object referenced from a page, there is an indication of
// where in the page's content stream the object is first referenced.
const uint32_t dwSharedNumeratorBits = hStream->GetBits(16);
if (dwSharedNumeratorBits > 32)
return false;
// Item 13: Skip Item 13 which has 16 bits.
hStream->SkipBits(16);
FX_SAFE_UINT32 required_bits = dwDeltaObjectsBits;
required_bits *= nPages;
if (!CanReadFromBitStream(hStream, required_bits))
return false;
m_PageInfos = std::vector<PageInfo>(nPages);
m_PageInfos[nFirstPageNum].set_start_obj_num(
m_pLinearized->GetFirstPageObjNum());
// The object number of remaining pages starts from 1.
uint32_t dwStartObjNum = 1;
for (uint32_t i = 0; i < nPages; ++i) {
FX_SAFE_UINT32 safeDeltaObj = hStream->GetBits(dwDeltaObjectsBits);
safeDeltaObj += dwObjLeastNum;
if (!safeDeltaObj.IsValid())
return false;
m_PageInfos[i].set_objects_count(safeDeltaObj.ValueOrDie());
if (i == nFirstPageNum)
continue;
m_PageInfos[i].set_start_obj_num(dwStartObjNum);
dwStartObjNum += m_PageInfos[i].objects_count();
}
hStream->ByteAlign();
required_bits = dwDeltaPageLenBits;
required_bits *= nPages;
if (!CanReadFromBitStream(hStream, required_bits))
return false;
for (uint32_t i = 0; i < nPages; ++i) {
FX_SAFE_UINT32 safePageLen = hStream->GetBits(dwDeltaPageLenBits);
safePageLen += dwPageLeastLen;
if (!safePageLen.IsValid())
return false;
m_PageInfos[i].set_page_length(safePageLen.ValueOrDie());
}
DCHECK(m_szFirstPageObjOffset);
m_PageInfos[nFirstPageNum].set_page_offset(m_szFirstPageObjOffset);
FX_FILESIZE prev_page_end = m_pLinearized->GetFirstPageEndOffset();
for (uint32_t i = 0; i < nPages; ++i) {
if (i == nFirstPageNum)
continue;
m_PageInfos[i].set_page_offset(prev_page_end);
prev_page_end += m_PageInfos[i].page_length();
}
hStream->ByteAlign();
// Number of shared objects.
required_bits = dwSharedObjBits;
required_bits *= nPages;
if (!CanReadFromBitStream(hStream, required_bits))
return false;
std::vector<uint32_t> dwNSharedObjsArray(nPages);
for (uint32_t i = 0; i < nPages; i++)
dwNSharedObjsArray[i] = hStream->GetBits(dwSharedObjBits);
hStream->ByteAlign();
// Array of identifiers, size = nshared_objects.
for (uint32_t i = 0; i < nPages; i++) {
required_bits = dwSharedIdBits;
required_bits *= dwNSharedObjsArray[i];
if (!CanReadFromBitStream(hStream, required_bits))
return false;
for (uint32_t j = 0; j < dwNSharedObjsArray[i]; j++)
m_PageInfos[i].AddIdentifier(hStream->GetBits(dwSharedIdBits));
}
hStream->ByteAlign();
if (dwSharedNumeratorBits) {
for (uint32_t i = 0; i < nPages; i++) {
FX_SAFE_UINT32 safeSize = dwNSharedObjsArray[i];
safeSize *= dwSharedNumeratorBits;
if (!CanReadFromBitStream(hStream, safeSize))
return false;
hStream->SkipBits(safeSize.ValueOrDie());
}
hStream->ByteAlign();
}
FX_SAFE_UINT32 safeTotalPageLen = nPages;
safeTotalPageLen *= dwDeltaPageLenBits;
if (!CanReadFromBitStream(hStream, safeTotalPageLen))
return false;
hStream->SkipBits(safeTotalPageLen.ValueOrDie());
hStream->ByteAlign();
return true;
}
bool CPDF_HintTables::ReadSharedObjHintTable(CFX_BitStream* hStream,
uint32_t offset) {
if (!hStream || hStream->IsEOF())
return false;
FX_SAFE_UINT32 bit_offset = offset;
bit_offset *= 8;
if (!bit_offset.IsValid() || hStream->GetPos() > bit_offset.ValueOrDie())
return false;
hStream->SkipBits((bit_offset - hStream->GetPos()).ValueOrDie());
const uint32_t kHeaderSize = 192;
if (hStream->BitsRemaining() < kHeaderSize)
return false;
// Item 1: The object number of the first object in the shared objects
// section.
uint32_t dwFirstSharedObjNum = hStream->GetBits(32);
if (!dwFirstSharedObjNum)
return false;
// Item 2: The location of the first object in the shared objects section.
const FX_FILESIZE szFirstSharedObjLoc =
HintsOffsetToFileOffset(hStream->GetBits(32));
if (!szFirstSharedObjLoc)
return false;
// Item 3: The number of shared object entries for the first page.
m_nFirstPageSharedObjs = hStream->GetBits(32);
// Item 4: The number of shared object entries for the shared objects
// section, including the number of shared object entries for the first page.
uint32_t dwSharedObjTotal = hStream->GetBits(32);
// Item 5: The number of bits needed to represent the greatest number of
// objects in a shared object group.
uint32_t dwSharedObjNumBits = hStream->GetBits(16);
if (dwSharedObjNumBits > 32)
return false;
// Item 6: The least length of a shared object group in bytes.
uint32_t dwGroupLeastLen = hStream->GetBits(32);
// Item 7: The number of bits needed to represent the difference between the
// greatest and least length of a shared object group, in bytes.
uint32_t dwDeltaGroupLen = hStream->GetBits(16);
// Trying to decode more than 32 bits isn't going to work when we write into
// a uint32_t. Decoding 0 bits also makes no sense.
if (!IsValidPageOffsetHintTableBitCount(dwDeltaGroupLen))
return false;
if (dwFirstSharedObjNum >= CPDF_Parser::kMaxObjectNumber ||
m_nFirstPageSharedObjs >= CPDF_Parser::kMaxObjectNumber ||
dwSharedObjTotal >= CPDF_Parser::kMaxObjectNumber) {
return false;
}
FX_SAFE_UINT32 required_bits = dwSharedObjTotal;
required_bits *= dwDeltaGroupLen;
if (!CanReadFromBitStream(hStream, required_bits))
return false;
if (dwSharedObjTotal > 0) {
uint32_t dwLastSharedObj = dwSharedObjTotal - 1;
if (dwLastSharedObj > m_nFirstPageSharedObjs) {
FX_SAFE_UINT32 safeObjNum = dwFirstSharedObjNum;
safeObjNum += dwLastSharedObj - m_nFirstPageSharedObjs;
if (!safeObjNum.IsValid())
return false;
}
}
m_SharedObjGroupInfos.resize(dwSharedObjTotal);
// Table F.6 – Shared object hint table, shared object group entries:
// Item 1: A number that, when added to the least shared object
// group length.
FX_SAFE_FILESIZE prev_shared_group_end_offset = m_szFirstPageObjOffset;
for (uint32_t i = 0; i < dwSharedObjTotal; ++i) {
if (i == m_nFirstPageSharedObjs)
prev_shared_group_end_offset = szFirstSharedObjLoc;
FX_SAFE_UINT32 safeObjLen = hStream->GetBits(dwDeltaGroupLen);
safeObjLen += dwGroupLeastLen;
if (!safeObjLen.IsValid())
return false;
m_SharedObjGroupInfos[i].m_dwLength = safeObjLen.ValueOrDie();
m_SharedObjGroupInfos[i].m_szOffset =
prev_shared_group_end_offset.ValueOrDie();
prev_shared_group_end_offset += m_SharedObjGroupInfos[i].m_dwLength;
if (!prev_shared_group_end_offset.IsValid())
return false;
}
hStream->ByteAlign();
{
// Item 2: A flag indicating whether the shared object signature (item 3) is
// present.
uint32_t signature_count = 0;
for (uint32_t i = 0; i < dwSharedObjTotal; ++i) {
signature_count += hStream->GetBits(1);
}
hStream->ByteAlign();
// Item 3: (Only if item 2 is 1) The shared object signature, a 16-byte MD5
// hash that uniquely identifies the resource that the group of objects
// represents.
if (signature_count) {
required_bits = signature_count;
required_bits *= 128;
if (!CanReadFromBitStream(hStream, required_bits))
return false;
hStream->SkipBits(required_bits.ValueOrDie());
hStream->ByteAlign();
}
}
// Item 4: A number equal to 1 less than the number of objects in the group.
FX_SAFE_UINT32 cur_obj_num = m_pLinearized->GetFirstPageObjNum();
for (uint32_t i = 0; i < dwSharedObjTotal; ++i) {
if (i == m_nFirstPageSharedObjs)
cur_obj_num = dwFirstSharedObjNum;
FX_SAFE_UINT32 obj_count =
dwSharedObjNumBits ? hStream->GetBits(dwSharedObjNumBits) : 0;
obj_count += 1;
if (!obj_count.IsValid())
return false;
uint32_t obj_num = cur_obj_num.ValueOrDie();
cur_obj_num += obj_count.ValueOrDie();
if (!cur_obj_num.IsValid())
return false;
m_SharedObjGroupInfos[i].m_dwStartObjNum = obj_num;
m_SharedObjGroupInfos[i].m_dwObjectsCount = obj_count.ValueOrDie();
}
hStream->ByteAlign();
return true;
}
bool CPDF_HintTables::GetPagePos(uint32_t index,
FX_FILESIZE* szPageStartPos,
FX_FILESIZE* szPageLength,
uint32_t* dwObjNum) const {
if (index >= m_pLinearized->GetPageCount())
return false;
*szPageStartPos = m_PageInfos[index].page_offset();
*szPageLength = m_PageInfos[index].page_length();
*dwObjNum = m_PageInfos[index].start_obj_num();
return true;
}
CPDF_DataAvail::DocAvailStatus CPDF_HintTables::CheckPage(uint32_t index) {
if (index == m_pLinearized->GetFirstPageNo())
return CPDF_DataAvail::kDataAvailable;
if (index >= m_pLinearized->GetPageCount())
return CPDF_DataAvail::kDataError;
const uint32_t dwLength = m_PageInfos[index].page_length();
if (!dwLength)
return CPDF_DataAvail::kDataError;
if (!m_pValidator->CheckDataRangeAndRequestIfUnavailable(
m_PageInfos[index].page_offset(), dwLength)) {
return CPDF_DataAvail::kDataNotAvailable;
}
// Download data of shared objects in the page.
for (const uint32_t dwIndex : m_PageInfos[index].Identifiers()) {
if (dwIndex >= m_SharedObjGroupInfos.size())
continue;
const SharedObjGroupInfo& shared_group_info =
m_SharedObjGroupInfos[dwIndex];
if (!shared_group_info.m_szOffset || !shared_group_info.m_dwLength)
return CPDF_DataAvail::kDataError;
if (!m_pValidator->CheckDataRangeAndRequestIfUnavailable(
shared_group_info.m_szOffset, shared_group_info.m_dwLength)) {
return CPDF_DataAvail::kDataNotAvailable;
}
}
return CPDF_DataAvail::kDataAvailable;
}
bool CPDF_HintTables::LoadHintStream(CPDF_Stream* pHintStream) {
if (!pHintStream || !m_pLinearized->HasHintTable())
return false;
CPDF_Dictionary* pDict = pHintStream->GetDict();
CPDF_Object* pOffset = pDict ? pDict->GetObjectFor("S") : nullptr;
if (!pOffset || !pOffset->IsNumber())
return false;
int shared_hint_table_offset = pOffset->GetInteger();
if (shared_hint_table_offset <= 0)
return false;
auto pAcc = pdfium::MakeRetain<CPDF_StreamAcc>(pHintStream);
pAcc->LoadAllDataFiltered();
uint32_t size = pAcc->GetSize();
// The header section of page offset hint table is 36 bytes.
// The header section of shared object hint table is 24 bytes.
// Hint table has at least 60 bytes.
const uint32_t kMinStreamLength = 60;
if (size < kMinStreamLength)
return false;
FX_SAFE_UINT32 safe_shared_hint_table_offset = shared_hint_table_offset;
if (!safe_shared_hint_table_offset.IsValid() ||
size < safe_shared_hint_table_offset.ValueOrDie()) {
return false;
}
CFX_BitStream bs(pAcc->GetSpan().subspan(0, size));
return ReadPageHintTable(&bs) &&
ReadSharedObjHintTable(&bs, shared_hint_table_offset);
}
FX_FILESIZE CPDF_HintTables::HintsOffsetToFileOffset(
uint32_t hints_offset) const {
FX_SAFE_FILESIZE file_offset = hints_offset;
if (!file_offset.IsValid())
return 0;
// The resulting positions shall be interpreted as if the primary hint stream
// itself were not present. That is, a position greater than the hint stream
// offset shall have the hint stream length added to it to determine the
// actual offset relative to the beginning of the file.
// See ISO 32000-1:2008 spec, annex F.4 (Hint tables).
// Note: The PDF spec does not mention this, but positions equal to the hint
// stream offset also need to have the hint stream length added to it. e.g.
// There exists linearized PDFs generated by Adobe software that have this
// property.
if (file_offset.ValueOrDie() >= m_pLinearized->GetHintStart())
file_offset += m_pLinearized->GetHintLength();
return file_offset.ValueOrDefault(0);
}