From 57da88747e02c9d6bb66b7ff38b4db963fd388c9 Mon Sep 17 00:00:00 2001 From: m-holger Date: Mon, 17 Mar 2025 13:50:23 +0000 Subject: [PATCH] Revert "Split QPDF.cc into QPDF.cc and QPDF_objects.cc" --- libqpdf/CMakeLists.txt | 1 - libqpdf/QPDF.cc | 1954 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------------ libqpdf/QPDF_objects.cc | 2017 ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- manual/release-notes.rst | 11 ++++++----- 4 files changed, 1948 insertions(+), 2035 deletions(-) delete mode 100644 libqpdf/QPDF_objects.cc diff --git a/libqpdf/CMakeLists.txt b/libqpdf/CMakeLists.txt index d351a0c..af8034a 100644 --- a/libqpdf/CMakeLists.txt +++ b/libqpdf/CMakeLists.txt @@ -95,7 +95,6 @@ set(libqpdf_SOURCES QPDF_encryption.cc QPDF_json.cc QPDF_linearization.cc - QPDF_objects.cc QPDF_optimization.cc QPDF_pages.cc QTC.cc diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc index c1dbcb7..015c5e4 100644 --- a/libqpdf/QPDF.cc +++ b/libqpdf/QPDF.cc @@ -413,26 +413,1726 @@ QPDF::findHeader() return valid; } +bool +QPDF::findStartxref() +{ + if (readToken(*m->file).isWord("startxref") && readToken(*m->file).isInteger()) { + // Position in front of offset token + m->file->seek(m->file->getLastOffset(), SEEK_SET); + return true; + } + return false; +} + +void +QPDF::parse(char const* password) +{ + if (password) { + m->encp->provided_password = password; + } + + // Find the header anywhere in the first 1024 bytes of the file. + PatternFinder hf(*this, &QPDF::findHeader); + if (!m->file->findFirst("%PDF-", 0, 1024, hf)) { + QTC::TC("qpdf", "QPDF not a pdf file"); + warn(damagedPDF("", 0, "can't find PDF header")); + // QPDFWriter writes files that usually require at least version 1.2 for /FlateDecode + m->pdf_version = "1.2"; + } + + // PDF spec says %%EOF must be found within the last 1024 bytes of/ the file. We add an extra + // 30 characters to leave room for the startxref stuff. + m->file->seek(0, SEEK_END); + qpdf_offset_t end_offset = m->file->tell(); + m->xref_table_max_offset = end_offset; + // Sanity check on object ids. All objects must appear in xref table / stream. In all realistic + // scenarios at least 3 bytes are required. + if (m->xref_table_max_id > m->xref_table_max_offset / 3) { + m->xref_table_max_id = static_cast(m->xref_table_max_offset / 3); + } + qpdf_offset_t start_offset = (end_offset > 1054 ? end_offset - 1054 : 0); + PatternFinder sf(*this, &QPDF::findStartxref); + qpdf_offset_t xref_offset = 0; + if (m->file->findLast("startxref", start_offset, 0, sf)) { + xref_offset = QUtil::string_to_ll(readToken(*m->file).getValue().c_str()); + } + + try { + if (xref_offset == 0) { + QTC::TC("qpdf", "QPDF can't find startxref"); + throw damagedPDF("", 0, "can't find startxref"); + } + try { + read_xref(xref_offset); + } catch (QPDFExc&) { + throw; + } catch (std::exception& e) { + throw damagedPDF("", 0, std::string("error reading xref: ") + e.what()); + } + } catch (QPDFExc& e) { + if (m->attempt_recovery) { + reconstruct_xref(e, xref_offset > 0); + QTC::TC("qpdf", "QPDF reconstructed xref table"); + } else { + throw; + } + } + + initializeEncryption(); + m->parsed = true; + if (m->xref_table.size() > 0 && !getRoot().getKey("/Pages").isDictionary()) { + // QPDFs created from JSON have an empty xref table and no root object yet. + throw damagedPDF("", 0, "unable to find page tree"); + } +} + +void +QPDF::inParse(bool v) +{ + if (m->in_parse == v) { + // This happens if QPDFParser::parse tries to resolve an indirect object while it is + // parsing. + throw std::logic_error( + "QPDF: re-entrant parsing detected. This is a qpdf bug." + " Please report at https://github.com/qpdf/qpdf/issues."); + } + m->in_parse = v; +} + +void +QPDF::warn(QPDFExc const& e) +{ + if (m->max_warnings > 0 && m->warnings.size() >= m->max_warnings) { + stopOnError("Too many warnings - file is too badly damaged"); + } + m->warnings.push_back(e); + if (!m->suppress_warnings) { + *m->log->getWarn() << "WARNING: " << m->warnings.back().what() << "\n"; + } +} + +void +QPDF::warn( + qpdf_error_code_e error_code, + std::string const& object, + qpdf_offset_t offset, + std::string const& message) +{ + warn(QPDFExc(error_code, getFilename(), object, offset, message)); +} + +void +QPDF::setTrailer(QPDFObjectHandle obj) +{ + if (m->trailer) { + return; + } + m->trailer = obj; +} + +void +QPDF::reconstruct_xref(QPDFExc& e, bool found_startxref) +{ + if (m->reconstructed_xref) { + // Avoid xref reconstruction infinite loops. This is getting very hard to reproduce because + // qpdf is throwing many fewer exceptions while parsing. Most situations are warnings now. + throw e; + } + + // If recovery generates more than 1000 warnings, the file is so severely damaged that there + // probably is no point trying to continue. + const auto max_warnings = m->warnings.size() + 1000U; + auto check_warnings = [this, max_warnings]() { + if (m->warnings.size() > max_warnings) { + throw damagedPDF("", 0, "too many errors while reconstructing cross-reference table"); + } + }; + + m->reconstructed_xref = true; + // We may find more objects, which may contain dangling references. + m->fixed_dangling_refs = false; + + warn(damagedPDF("", 0, "file is damaged")); + warn(e); + warn(damagedPDF("", 0, "Attempting to reconstruct cross-reference table")); + + // Delete all references to type 1 (uncompressed) objects + std::vector to_delete; + for (auto const& iter: m->xref_table) { + if (iter.second.getType() == 1) { + to_delete.emplace_back(iter.first); + } + } + for (auto const& iter: to_delete) { + m->xref_table.erase(iter); + } + + std::vector> found_objects; + std::vector trailers; + std::vector startxrefs; + + m->file->seek(0, SEEK_END); + qpdf_offset_t eof = m->file->tell(); + m->file->seek(0, SEEK_SET); + // Don't allow very long tokens here during recovery. All the interesting tokens are covered. + static size_t const MAX_LEN = 10; + while (m->file->tell() < eof) { + QPDFTokenizer::Token t1 = readToken(*m->file, MAX_LEN); + qpdf_offset_t token_start = m->file->tell() - toO(t1.getValue().length()); + if (t1.isInteger()) { + auto pos = m->file->tell(); + auto t2 = readToken(*m->file, MAX_LEN); + if (t2.isInteger() && readToken(*m->file, MAX_LEN).isWord("obj")) { + int obj = QUtil::string_to_int(t1.getValue().c_str()); + int gen = QUtil::string_to_int(t2.getValue().c_str()); + if (obj <= m->xref_table_max_id) { + found_objects.emplace_back(obj, gen, token_start); + } else { + warn(damagedPDF( + "", 0, "ignoring object with impossibly large id " + std::to_string(obj))); + } + } + m->file->seek(pos, SEEK_SET); + } else if (!m->trailer && t1.isWord("trailer")) { + trailers.emplace_back(m->file->tell()); + } else if (!found_startxref && t1.isWord("startxref")) { + startxrefs.emplace_back(m->file->tell()); + } + check_warnings(); + m->file->findAndSkipNextEOL(); + } + + if (!found_startxref && !startxrefs.empty() && !found_objects.empty() && + startxrefs.back() > std::get<2>(found_objects.back())) { + try { + m->file->seek(startxrefs.back(), SEEK_SET); + if (auto offset = QUtil::string_to_ll(readToken(*m->file).getValue().data())) { + read_xref(offset); + if (getRoot().getKey("/Pages").isDictionary()) { + QTC::TC("qpdf", "QPDF startxref more than 1024 before end"); + warn( + damagedPDF("", 0, "startxref was more than 1024 bytes before end of file")); + initializeEncryption(); + m->parsed = true; + m->reconstructed_xref = false; + return; + } + } + } catch (...) { + // ok, bad luck. Do recovery. + } + } + + auto rend = found_objects.rend(); + for (auto it = found_objects.rbegin(); it != rend; it++) { + auto [obj, gen, token_start] = *it; + insertXrefEntry(obj, 1, token_start, gen); + check_warnings(); + } + m->deleted_objects.clear(); + + for (auto it = trailers.rbegin(); it != trailers.rend(); it++) { + m->file->seek(*it, SEEK_SET); + auto t = readTrailer(); + if (!t.isDictionary()) { + // Oh well. It was worth a try. + } else { + if (t.hasKey("/Root")) { + m->trailer = t; + break; + } + warn(damagedPDF("trailer", *it, "recovered trailer has no /Root entry")); + } + check_warnings(); + } + + if (!m->trailer) { + qpdf_offset_t max_offset{0}; + size_t max_size{0}; + // If there are any xref streams, take the last one to appear. + for (auto const& iter: m->xref_table) { + auto entry = iter.second; + if (entry.getType() != 1) { + continue; + } + auto oh = getObject(iter.first); + try { + if (!oh.isStreamOfType("/XRef")) { + continue; + } + } catch (std::exception&) { + continue; + } + auto offset = entry.getOffset(); + auto size = oh.getDict().getKey("/Size").getUIntValueAsUInt(); + if (size > max_size || (size == max_size && offset > max_offset)) { + max_offset = offset; + setTrailer(oh.getDict()); + } + check_warnings(); + } + if (max_offset > 0) { + try { + read_xref(max_offset); + } catch (std::exception&) { + warn(damagedPDF( + "", 0, "error decoding candidate xref stream while recovering damaged file")); + } + QTC::TC("qpdf", "QPDF recover xref stream"); + } + } + + if (!m->trailer || (!m->parsed && !m->trailer.getKey("/Root").isDictionary())) { + // Try to find a Root dictionary. As a quick fix try the one with the highest object id. + QPDFObjectHandle root; + for (auto const& iter: m->obj_cache) { + try { + if (QPDFObjectHandle(iter.second.object).isDictionaryOfType("/Catalog")) { + root = iter.second.object; + } + } catch (std::exception&) { + continue; + } + } + if (root) { + if (!m->trailer) { + warn(damagedPDF( + "", 0, "unable to find trailer dictionary while recovering damaged file")); + m->trailer = QPDFObjectHandle::newDictionary(); + } + m->trailer.replaceKey("/Root", root); + } + } + + if (!m->trailer) { + // We could check the last encountered object to see if it was an xref stream. If so, we + // could try to get the trailer from there. This may make it possible to recover files with + // bad startxref pointers even when they have object streams. + + throw damagedPDF("", 0, "unable to find trailer dictionary while recovering damaged file"); + } + if (m->xref_table.empty()) { + // We cannot check for an empty xref table in parse because empty tables are valid when + // creating QPDF objects from JSON. + throw damagedPDF("", 0, "unable to find objects while recovering damaged file"); + } + check_warnings(); + if (!m->parsed) { + m->parsed = true; + getAllPages(); + check_warnings(); + if (m->all_pages.empty()) { + m->parsed = false; + throw damagedPDF("", 0, "unable to find any pages while recovering damaged file"); + } + } + // We could iterate through the objects looking for streams and try to find objects inside of + // them, but it's probably not worth the trouble. Acrobat can't recover files with any errors + // in an xref stream, and this would be a real long shot anyway. If we wanted to do anything + // that involved looking at stream contents, we'd also have to call initializeEncryption() here. + // It's safe to call it more than once. +} + +void +QPDF::read_xref(qpdf_offset_t xref_offset) +{ + std::map free_table; + std::set visited; + while (xref_offset) { + visited.insert(xref_offset); + char buf[7]; + memset(buf, 0, sizeof(buf)); + m->file->seek(xref_offset, SEEK_SET); + // Some files miss the mark a little with startxref. We could do a better job of searching + // in the neighborhood for something that looks like either an xref table or stream, but the + // simple heuristic of skipping whitespace can help with the xref table case and is harmless + // with the stream case. + bool done = false; + bool skipped_space = false; + while (!done) { + char ch; + if (1 == m->file->read(&ch, 1)) { + if (util::is_space(ch)) { + skipped_space = true; + } else { + m->file->unreadCh(ch); + done = true; + } + } else { + QTC::TC("qpdf", "QPDF eof skipping spaces before xref", skipped_space ? 0 : 1); + done = true; + } + } + + m->file->read(buf, sizeof(buf) - 1); + // The PDF spec says xref must be followed by a line terminator, but files exist in the wild + // where it is terminated by arbitrary whitespace. + if ((strncmp(buf, "xref", 4) == 0) && util::is_space(buf[4])) { + if (skipped_space) { + QTC::TC("qpdf", "QPDF xref skipped space"); + warn(damagedPDF("", 0, "extraneous whitespace seen before xref")); + } + QTC::TC( + "qpdf", + "QPDF xref space", + ((buf[4] == '\n') ? 0 + : (buf[4] == '\r') ? 1 + : (buf[4] == ' ') ? 2 + : 9999)); + int skip = 4; + // buf is null-terminated, and util::is_space('\0') is false, so this won't overrun. + while (util::is_space(buf[skip])) { + ++skip; + } + xref_offset = read_xrefTable(xref_offset + skip); + } else { + xref_offset = read_xrefStream(xref_offset); + } + if (visited.count(xref_offset) != 0) { + QTC::TC("qpdf", "QPDF xref loop"); + throw damagedPDF("", 0, "loop detected following xref tables"); + } + } + + if (!m->trailer) { + throw damagedPDF("", 0, "unable to find trailer while reading xref"); + } + int size = m->trailer.getKey("/Size").getIntValueAsInt(); + int max_obj = 0; + if (!m->xref_table.empty()) { + max_obj = m->xref_table.rbegin()->first.getObj(); + } + if (!m->deleted_objects.empty()) { + max_obj = std::max(max_obj, *(m->deleted_objects.rbegin())); + } + if ((size < 1) || (size - 1 != max_obj)) { + QTC::TC("qpdf", "QPDF xref size mismatch"); + warn(damagedPDF( + "", + 0, + ("reported number of objects (" + std::to_string(size) + + ") is not one plus the highest object number (" + std::to_string(max_obj) + ")"))); + } + + // We no longer need the deleted_objects table, so go ahead and clear it out to make sure we + // never depend on its being set. + m->deleted_objects.clear(); + + // Make sure we keep only the highest generation for any object. + QPDFObjGen last_og{-1, 0}; + for (auto const& item: m->xref_table) { + auto id = item.first.getObj(); + if (id == last_og.getObj() && id > 0) { + removeObject(last_og); + } + last_og = item.first; + } +} + +bool +QPDF::parse_xrefFirst(std::string const& line, int& obj, int& num, int& bytes) +{ + // is_space and is_digit both return false on '\0', so this will not overrun the null-terminated + // buffer. + char const* p = line.c_str(); + char const* start = line.c_str(); + + // Skip zero or more spaces + while (util::is_space(*p)) { + ++p; + } + // Require digit + if (!util::is_digit(*p)) { + return false; + } + // Gather digits + std::string obj_str; + while (util::is_digit(*p)) { + obj_str.append(1, *p++); + } + // Require space + if (!util::is_space(*p)) { + return false; + } + // Skip spaces + while (util::is_space(*p)) { + ++p; + } + // Require digit + if (!util::is_digit(*p)) { + return false; + } + // Gather digits + std::string num_str; + while (util::is_digit(*p)) { + num_str.append(1, *p++); + } + // Skip any space including line terminators + while (util::is_space(*p)) { + ++p; + } + bytes = toI(p - start); + obj = QUtil::string_to_int(obj_str.c_str()); + num = QUtil::string_to_int(num_str.c_str()); + return true; +} + +bool +QPDF::read_bad_xrefEntry(qpdf_offset_t& f1, int& f2, char& type) +{ + // Reposition after initial read attempt and reread. + m->file->seek(m->file->getLastOffset(), SEEK_SET); + auto line = m->file->readLine(30); + + // is_space and is_digit both return false on '\0', so this will not overrun the null-terminated + // buffer. + char const* p = line.data(); + + // Skip zero or more spaces. There aren't supposed to be any. + bool invalid = false; + while (util::is_space(*p)) { + ++p; + QTC::TC("qpdf", "QPDF ignore first space in xref entry"); + invalid = true; + } + // Require digit + if (!util::is_digit(*p)) { + return false; + } + // Gather digits + std::string f1_str; + while (util::is_digit(*p)) { + f1_str.append(1, *p++); + } + // Require space + if (!util::is_space(*p)) { + return false; + } + if (util::is_space(*(p + 1))) { + QTC::TC("qpdf", "QPDF ignore first extra space in xref entry"); + invalid = true; + } + // Skip spaces + while (util::is_space(*p)) { + ++p; + } + // Require digit + if (!util::is_digit(*p)) { + return false; + } + // Gather digits + std::string f2_str; + while (util::is_digit(*p)) { + f2_str.append(1, *p++); + } + // Require space + if (!util::is_space(*p)) { + return false; + } + if (util::is_space(*(p + 1))) { + QTC::TC("qpdf", "QPDF ignore second extra space in xref entry"); + invalid = true; + } + // Skip spaces + while (util::is_space(*p)) { + ++p; + } + if ((*p == 'f') || (*p == 'n')) { + type = *p; + } else { + return false; + } + if ((f1_str.length() != 10) || (f2_str.length() != 5)) { + QTC::TC("qpdf", "QPDF ignore length error xref entry"); + invalid = true; + } + + if (invalid) { + warn(damagedPDF("xref table", "accepting invalid xref table entry")); + } + + f1 = QUtil::string_to_ll(f1_str.c_str()); + f2 = QUtil::string_to_int(f2_str.c_str()); + + return true; +} + +// Optimistically read and parse xref entry. If entry is bad, call read_bad_xrefEntry and return +// result. +bool +QPDF::read_xrefEntry(qpdf_offset_t& f1, int& f2, char& type) +{ + std::array line; + if (m->file->read(line.data(), 20) != 20) { + // C++20: [[unlikely]] + return false; + } + line[20] = '\0'; + char const* p = line.data(); + + int f1_len = 0; + int f2_len = 0; + + // is_space and is_digit both return false on '\0', so this will not overrun the null-terminated + // buffer. + + // Gather f1 digits. NB No risk of overflow as 9'999'999'999 < max long long. + while (*p == '0') { + ++f1_len; + ++p; + } + while (util::is_digit(*p) && f1_len++ < 10) { + f1 *= 10; + f1 += *p++ - '0'; + } + // Require space + if (!util::is_space(*p++)) { + // Entry doesn't start with space or digit. + // C++20: [[unlikely]] + return false; + } + // Gather digits. NB No risk of overflow as 99'999 < max int. + while (*p == '0') { + ++f2_len; + ++p; + } + while (util::is_digit(*p) && f2_len++ < 5) { + f2 *= 10; + f2 += static_cast(*p++ - '0'); + } + if (util::is_space(*p++) && (*p == 'f' || *p == 'n')) { + // C++20: [[likely]] + type = *p; + // No test for valid line[19]. + if (*(++p) && *(++p) && (*p == '\n' || *p == '\r') && f1_len == 10 && f2_len == 5) { + // C++20: [[likely]] + return true; + } + } + return read_bad_xrefEntry(f1, f2, type); +} + +// Read a single cross-reference table section and associated trailer. +qpdf_offset_t +QPDF::read_xrefTable(qpdf_offset_t xref_offset) +{ + m->file->seek(xref_offset, SEEK_SET); + std::string line; + while (true) { + line.assign(50, '\0'); + m->file->read(line.data(), line.size()); + int obj = 0; + int num = 0; + int bytes = 0; + if (!parse_xrefFirst(line, obj, num, bytes)) { + QTC::TC("qpdf", "QPDF invalid xref"); + throw damagedPDF("xref table", "xref syntax invalid"); + } + m->file->seek(m->file->getLastOffset() + bytes, SEEK_SET); + for (qpdf_offset_t i = obj; i - num < obj; ++i) { + if (i == 0) { + // This is needed by checkLinearization() + m->first_xref_item_offset = m->file->tell(); + } + // For xref_table, these will always be small enough to be ints + qpdf_offset_t f1 = 0; + int f2 = 0; + char type = '\0'; + if (!read_xrefEntry(f1, f2, type)) { + QTC::TC("qpdf", "QPDF invalid xref entry"); + throw damagedPDF( + "xref table", "invalid xref entry (obj=" + std::to_string(i) + ")"); + } + if (type == 'f') { + insertFreeXrefEntry(QPDFObjGen(toI(i), f2)); + } else { + insertXrefEntry(toI(i), 1, f1, f2); + } + } + qpdf_offset_t pos = m->file->tell(); + if (readToken(*m->file).isWord("trailer")) { + break; + } else { + m->file->seek(pos, SEEK_SET); + } + } + + // Set offset to previous xref table if any + QPDFObjectHandle cur_trailer = readTrailer(); + if (!cur_trailer.isDictionary()) { + QTC::TC("qpdf", "QPDF missing trailer"); + throw damagedPDF("", "expected trailer dictionary"); + } + + if (!m->trailer) { + setTrailer(cur_trailer); + + if (!m->trailer.hasKey("/Size")) { + QTC::TC("qpdf", "QPDF trailer lacks size"); + throw damagedPDF("trailer", "trailer dictionary lacks /Size key"); + } + if (!m->trailer.getKey("/Size").isInteger()) { + QTC::TC("qpdf", "QPDF trailer size not integer"); + throw damagedPDF("trailer", "/Size key in trailer dictionary is not an integer"); + } + } + + if (cur_trailer.hasKey("/XRefStm")) { + if (m->ignore_xref_streams) { + QTC::TC("qpdf", "QPDF ignoring XRefStm in trailer"); + } else { + if (cur_trailer.getKey("/XRefStm").isInteger()) { + // Read the xref stream but disregard any return value -- we'll use our trailer's + // /Prev key instead of the xref stream's. + (void)read_xrefStream(cur_trailer.getKey("/XRefStm").getIntValue()); + } else { + throw damagedPDF("xref stream", xref_offset, "invalid /XRefStm"); + } + } + } + + if (cur_trailer.hasKey("/Prev")) { + if (!cur_trailer.getKey("/Prev").isInteger()) { + QTC::TC("qpdf", "QPDF trailer prev not integer"); + throw damagedPDF("trailer", "/Prev key in trailer dictionary is not an integer"); + } + QTC::TC("qpdf", "QPDF prev key in trailer dictionary"); + return cur_trailer.getKey("/Prev").getIntValue(); + } + + return 0; +} + +// Read a single cross-reference stream. +qpdf_offset_t +QPDF::read_xrefStream(qpdf_offset_t xref_offset) +{ + if (!m->ignore_xref_streams) { + QPDFObjGen x_og; + QPDFObjectHandle xref_obj; + try { + xref_obj = + readObjectAtOffset(false, xref_offset, "xref stream", QPDFObjGen(0, 0), x_og, true); + } catch (QPDFExc&) { + // ignore -- report error below + } + if (xref_obj.isStreamOfType("/XRef")) { + QTC::TC("qpdf", "QPDF found xref stream"); + return processXRefStream(xref_offset, xref_obj); + } + } + + QTC::TC("qpdf", "QPDF can't find xref"); + throw damagedPDF("", xref_offset, "xref not found"); + return 0; // unreachable +} + +// Return the entry size of the xref stream and the processed W array. +std::pair> +QPDF::processXRefW(QPDFObjectHandle& dict, std::function damaged) +{ + auto W_obj = dict.getKey("/W"); + if (!(W_obj.isArray() && (W_obj.getArrayNItems() >= 3) && W_obj.getArrayItem(0).isInteger() && + W_obj.getArrayItem(1).isInteger() && W_obj.getArrayItem(2).isInteger())) { + throw damaged("Cross-reference stream does not have a proper /W key"); + } + + std::array W; + int entry_size = 0; + auto w_vector = W_obj.getArrayAsVector(); + int max_bytes = sizeof(qpdf_offset_t); + for (size_t i = 0; i < 3; ++i) { + W[i] = w_vector[i].getIntValueAsInt(); + if (W[i] > max_bytes) { + throw damaged("Cross-reference stream's /W contains impossibly large values"); + } + if (W[i] < 0) { + throw damaged("Cross-reference stream's /W contains negative values"); + } + entry_size += W[i]; + } + if (entry_size == 0) { + throw damaged("Cross-reference stream's /W indicates entry size of 0"); + } + return {entry_size, W}; +} + +// Validate Size key and return the maximum number of entries that the xref stream can contain. +int +QPDF::processXRefSize( + QPDFObjectHandle& dict, int entry_size, std::function damaged) +{ + // Number of entries is limited by the highest possible object id and stream size. + auto max_num_entries = std::numeric_limits::max(); + if (max_num_entries > (std::numeric_limits::max() / entry_size)) { + max_num_entries = toI(std::numeric_limits::max() / entry_size); + } + + auto Size_obj = dict.getKey("/Size"); + long long size; + if (!dict.getKey("/Size").getValueAsInt(size)) { + throw damaged("Cross-reference stream does not have a proper /Size key"); + } else if (size < 0) { + throw damaged("Cross-reference stream has a negative /Size key"); + } else if (size >= max_num_entries) { + throw damaged("Cross-reference stream has an impossibly large /Size key"); + } + // We are not validating that Size <= (Size key of parent xref / trailer). + return max_num_entries; +} + +// Return the number of entries of the xref stream and the processed Index array. +std::pair>> +QPDF::processXRefIndex( + QPDFObjectHandle& dict, int max_num_entries, std::function damaged) +{ + auto size = dict.getKey("/Size").getIntValueAsInt(); + auto Index_obj = dict.getKey("/Index"); + + if (Index_obj.isArray()) { + std::vector> indx; + int num_entries = 0; + auto index_vec = Index_obj.getArrayAsVector(); + if ((index_vec.size() % 2) || index_vec.size() < 2) { + throw damaged("Cross-reference stream's /Index has an invalid number of values"); + } + + int i = 0; + long long first = 0; + for (auto& val: index_vec) { + if (val.isInteger()) { + if (i % 2) { + auto count = val.getIntValue(); + if (count <= 0) { + throw damaged( + "Cross-reference stream section claims to contain " + + std::to_string(count) + " entries"); + } + // We are guarding against the possibility of num_entries * entry_size + // overflowing. We are not checking that entries are in ascending order as + // required by the spec, which probably should generate a warning. We are also + // not checking that for each subsection first object number + number of entries + // <= /Size. The spec requires us to ignore object number > /Size. + if (first > (max_num_entries - count) || + count > (max_num_entries - num_entries)) { + throw damaged( + "Cross-reference stream claims to contain too many entries: " + + std::to_string(first) + " " + std::to_string(max_num_entries) + " " + + std::to_string(num_entries)); + } + indx.emplace_back(static_cast(first), static_cast(count)); + num_entries += static_cast(count); + } else { + first = val.getIntValue(); + if (first < 0) { + throw damaged( + "Cross-reference stream's /Index contains a negative object id"); + } else if (first > max_num_entries) { + throw damaged( + "Cross-reference stream's /Index contains an impossibly " + "large object id"); + } + } + } else { + throw damaged( + "Cross-reference stream's /Index's item " + std::to_string(i) + + " is not an integer"); + } + i++; + } + QTC::TC("qpdf", "QPDF xref /Index is array", index_vec.size() == 2 ? 0 : 1); + return {num_entries, indx}; + } else if (Index_obj.isNull()) { + QTC::TC("qpdf", "QPDF xref /Index is null"); + return {size, {{0, size}}}; + } else { + throw damaged("Cross-reference stream does not have a proper /Index key"); + } +} + +qpdf_offset_t +QPDF::processXRefStream(qpdf_offset_t xref_offset, QPDFObjectHandle& xref_obj) +{ + auto damaged = [this, xref_offset](std::string_view msg) -> QPDFExc { + return damagedPDF("xref stream", xref_offset, msg.data()); + }; + + auto dict = xref_obj.getDict(); + + auto [entry_size, W] = processXRefW(dict, damaged); + int max_num_entries = processXRefSize(dict, entry_size, damaged); + auto [num_entries, indx] = processXRefIndex(dict, max_num_entries, damaged); + + std::shared_ptr bp = xref_obj.getStreamData(qpdf_dl_specialized); + size_t actual_size = bp->getSize(); + auto expected_size = toS(entry_size) * toS(num_entries); + + if (expected_size != actual_size) { + QPDFExc x = damaged( + "Cross-reference stream data has the wrong size; expected = " + + std::to_string(expected_size) + "; actual = " + std::to_string(actual_size)); + if (expected_size > actual_size) { + throw x; + } else { + warn(x); + } + } + + bool saw_first_compressed_object = false; + + // Actual size vs. expected size check above ensures that we will not overflow any buffers here. + // We know that entry_size * num_entries is less or equal to the size of the buffer. + auto p = bp->getBuffer(); + for (auto [obj, sec_entries]: indx) { + // Process a subsection. + for (int i = 0; i < sec_entries; ++i) { + // Read this entry + std::array fields{}; + if (W[0] == 0) { + QTC::TC("qpdf", "QPDF default for xref stream field 0"); + fields[0] = 1; + } + for (size_t j = 0; j < 3; ++j) { + for (int k = 0; k < W[j]; ++k) { + fields[j] <<= 8; + fields[j] |= *p++; + } + } + + // Get the generation number. The generation number is 0 unless this is an uncompressed + // object record, in which case the generation number appears as the third field. + if (saw_first_compressed_object) { + if (fields[0] != 2) { + m->uncompressed_after_compressed = true; + } + } else if (fields[0] == 2) { + saw_first_compressed_object = true; + } + if (obj == 0) { + // This is needed by checkLinearization() + m->first_xref_item_offset = xref_offset; + } else if (fields[0] == 0) { + // Ignore fields[2], which we don't care about in this case. This works around the + // issue of some PDF files that put invalid values, like -1, here for deleted + // objects. + insertFreeXrefEntry(QPDFObjGen(obj, 0)); + } else { + insertXrefEntry(obj, toI(fields[0]), fields[1], toI(fields[2])); + } + ++obj; + } + } + + if (!m->trailer) { + setTrailer(dict); + } + + if (dict.hasKey("/Prev")) { + if (!dict.getKey("/Prev").isInteger()) { + throw damagedPDF( + "xref stream", "/Prev key in xref stream dictionary is not an integer"); + } + QTC::TC("qpdf", "QPDF prev key in xref stream dictionary"); + return dict.getKey("/Prev").getIntValue(); + } else { + return 0; + } +} + +void +QPDF::insertXrefEntry(int obj, int f0, qpdf_offset_t f1, int f2) +{ + // Populate the xref table in such a way that the first reference to an object that we see, + // which is the one in the latest xref table in which it appears, is the one that gets stored. + // This works because we are reading more recent appends before older ones. + + // If there is already an entry for this object and generation in the table, it means that a + // later xref table has registered this object. Disregard this one. + int new_gen = f0 == 2 ? 0 : f2; + + if (!(obj > 0 && obj <= m->xref_table_max_id && 0 <= f2 && new_gen < 65535)) { + // We are ignoring invalid objgens. Most will arrive here from xref reconstruction. There + // is probably no point having another warning but we could count invalid items in order to + // decide when to give up. + QTC::TC("qpdf", "QPDF xref overwrite invalid objgen"); + // ignore impossibly large object ids or object ids > Size. + return; + } + + if (m->deleted_objects.count(obj)) { + QTC::TC("qpdf", "QPDF xref deleted object"); + return; + } + + if (f0 == 2 && static_cast(f1) == obj) { + warn(damagedPDF("xref stream", "self-referential object stream " + std::to_string(obj))); + return; + } + + auto [iter, created] = m->xref_table.try_emplace(QPDFObjGen(obj, (f0 == 2 ? 0 : f2))); + if (!created) { + QTC::TC("qpdf", "QPDF xref reused object"); + return; + } + + switch (f0) { + case 1: + // f2 is generation + QTC::TC("qpdf", "QPDF xref gen > 0", ((f2 > 0) ? 1 : 0)); + iter->second = QPDFXRefEntry(f1); + break; + + case 2: + iter->second = QPDFXRefEntry(toI(f1), f2); + break; + + default: + throw damagedPDF("xref stream", "unknown xref stream entry type " + std::to_string(f0)); + break; + } +} + +void +QPDF::insertFreeXrefEntry(QPDFObjGen og) +{ + if (!m->xref_table.count(og)) { + m->deleted_objects.insert(og.getObj()); + } +} + +void +QPDF::showXRefTable() +{ + auto& cout = *m->log->getInfo(); + for (auto const& iter: m->xref_table) { + QPDFObjGen const& og = iter.first; + QPDFXRefEntry const& entry = iter.second; + cout << og.unparse('/') << ": "; + switch (entry.getType()) { + case 1: + cout << "uncompressed; offset = " << entry.getOffset(); + break; + + case 2: + *m->log->getInfo() << "compressed; stream = " << entry.getObjStreamNumber() + << ", index = " << entry.getObjStreamIndex(); + break; + + default: + throw std::logic_error("unknown cross-reference table type while showing xref_table"); + break; + } + m->log->info("\n"); + } +} + +// Resolve all objects in the xref table. If this triggers a xref table reconstruction abort and +// return false. Otherwise return true. +bool +QPDF::resolveXRefTable() +{ + bool may_change = !m->reconstructed_xref; + for (auto& iter: m->xref_table) { + if (isUnresolved(iter.first)) { + resolve(iter.first); + if (may_change && m->reconstructed_xref) { + return false; + } + } + } + return true; +} + +// Ensure all objects in the pdf file, including those in indirect references, appear in the object +// cache. +void +QPDF::fixDanglingReferences(bool force) +{ + if (m->fixed_dangling_refs) { + return; + } + if (!resolveXRefTable()) { + QTC::TC("qpdf", "QPDF fix dangling triggered xref reconstruction"); + resolveXRefTable(); + } + m->fixed_dangling_refs = true; +} + +size_t +QPDF::getObjectCount() +{ + // This method returns the next available indirect object number. makeIndirectObject uses it for + // this purpose. After fixDanglingReferences is called, all objects in the xref table will also + // be in obj_cache. + fixDanglingReferences(); + QPDFObjGen og; + if (!m->obj_cache.empty()) { + og = (*(m->obj_cache.rbegin())).first; + } + return toS(og.getObj()); +} + +std::vector +QPDF::getAllObjects() +{ + // After fixDanglingReferences is called, all objects are in the object cache. + fixDanglingReferences(); + std::vector result; + for (auto const& iter: m->obj_cache) { + result.push_back(newIndirect(iter.first, iter.second.object)); + } + return result; +} + +void +QPDF::setLastObjectDescription(std::string const& description, QPDFObjGen og) +{ + m->last_object_description.clear(); + if (!description.empty()) { + m->last_object_description += description; + if (og.isIndirect()) { + m->last_object_description += ": "; + } + } + if (og.isIndirect()) { + m->last_object_description += "object " + og.unparse(' '); + } +} + +QPDFObjectHandle +QPDF::readTrailer() +{ + qpdf_offset_t offset = m->file->tell(); + bool empty = false; + auto object = + QPDFParser(*m->file, "trailer", m->tokenizer, nullptr, this, true).parse(empty, false); + if (empty) { + // Nothing in the PDF spec appears to allow empty objects, but they have been encountered in + // actual PDF files and Adobe Reader appears to ignore them. + warn(damagedPDF("trailer", "empty object treated as null")); + } else if (object.isDictionary() && readToken(*m->file).isWord("stream")) { + warn(damagedPDF("trailer", m->file->tell(), "stream keyword found in trailer")); + } + // Override last_offset so that it points to the beginning of the object we just read + m->file->setLastOffset(offset); + return object; +} + +QPDFObjectHandle +QPDF::readObject(std::string const& description, QPDFObjGen og) +{ + setLastObjectDescription(description, og); + qpdf_offset_t offset = m->file->tell(); + bool empty = false; + + StringDecrypter decrypter{this, og}; + StringDecrypter* decrypter_ptr = m->encp->encrypted ? &decrypter : nullptr; + auto object = + QPDFParser(*m->file, m->last_object_description, m->tokenizer, decrypter_ptr, this, true) + .parse(empty, false); + if (empty) { + // Nothing in the PDF spec appears to allow empty objects, but they have been encountered in + // actual PDF files and Adobe Reader appears to ignore them. + warn(damagedPDF(*m->file, m->file->getLastOffset(), "empty object treated as null")); + return object; + } + auto token = readToken(*m->file); + if (object.isDictionary() && token.isWord("stream")) { + readStream(object, og, offset); + token = readToken(*m->file); + } + if (!token.isWord("endobj")) { + QTC::TC("qpdf", "QPDF err expected endobj"); + warn(damagedPDF("expected endobj")); + } + return object; +} + +// After reading stream dictionary and stream keyword, read rest of stream. void -QPDF::warn(QPDFExc const& e) +QPDF::readStream(QPDFObjectHandle& object, QPDFObjGen og, qpdf_offset_t offset) { - if (m->max_warnings > 0 && m->warnings.size() >= m->max_warnings) { - stopOnError("Too many warnings - file is too badly damaged"); - } - m->warnings.push_back(e); - if (!m->suppress_warnings) { - *m->log->getWarn() << "WARNING: " << m->warnings.back().what() << "\n"; + validateStreamLineEnd(object, og, offset); + + // Must get offset before accessing any additional objects since resolving a previously + // unresolved indirect object will change file position. + qpdf_offset_t stream_offset = m->file->tell(); + size_t length = 0; + + try { + auto length_obj = object.getKey("/Length"); + + if (!length_obj.isInteger()) { + if (length_obj.isNull()) { + QTC::TC("qpdf", "QPDF stream without length"); + throw damagedPDF(offset, "stream dictionary lacks /Length key"); + } + QTC::TC("qpdf", "QPDF stream length not integer"); + throw damagedPDF(offset, "/Length key in stream dictionary is not an integer"); + } + + length = toS(length_obj.getUIntValue()); + // Seek in two steps to avoid potential integer overflow + m->file->seek(stream_offset, SEEK_SET); + m->file->seek(toO(length), SEEK_CUR); + if (!readToken(*m->file).isWord("endstream")) { + QTC::TC("qpdf", "QPDF missing endstream"); + throw damagedPDF("expected endstream"); + } + } catch (QPDFExc& e) { + if (m->attempt_recovery) { + warn(e); + length = recoverStreamLength(m->file, og, stream_offset); + } else { + throw; + } } + object = QPDFObjectHandle(qpdf::Stream(*this, og, object, stream_offset, length)); } void -QPDF::warn( - qpdf_error_code_e error_code, - std::string const& object, +QPDF::validateStreamLineEnd(QPDFObjectHandle& object, QPDFObjGen og, qpdf_offset_t offset) +{ + // The PDF specification states that the word "stream" should be followed by either a carriage + // return and a newline or by a newline alone. It specifically disallowed following it by a + // carriage return alone since, in that case, there would be no way to tell whether the NL in a + // CR NL sequence was part of the stream data. However, some readers, including Adobe reader, + // accept a carriage return by itself when followed by a non-newline character, so that's what + // we do here. We have also seen files that have extraneous whitespace between the stream + // keyword and the newline. + while (true) { + char ch; + if (m->file->read(&ch, 1) == 0) { + // A premature EOF here will result in some other problem that will get reported at + // another time. + return; + } + if (ch == '\n') { + // ready to read stream data + QTC::TC("qpdf", "QPDF stream with NL only"); + return; + } + if (ch == '\r') { + // Read another character + if (m->file->read(&ch, 1) != 0) { + if (ch == '\n') { + // Ready to read stream data + QTC::TC("qpdf", "QPDF stream with CRNL"); + } else { + // Treat the \r by itself as the whitespace after endstream and start reading + // stream data in spite of not having seen a newline. + QTC::TC("qpdf", "QPDF stream with CR only"); + m->file->unreadCh(ch); + warn(damagedPDF( + m->file->tell(), "stream keyword followed by carriage return only")); + } + } + return; + } + if (!util::is_space(ch)) { + QTC::TC("qpdf", "QPDF stream without newline"); + m->file->unreadCh(ch); + warn(damagedPDF( + m->file->tell(), "stream keyword not followed by proper line terminator")); + return; + } + warn(damagedPDF(m->file->tell(), "stream keyword followed by extraneous whitespace")); + } +} + +QPDFObjectHandle +QPDF::readObjectInStream(std::shared_ptr& input, int obj) +{ + m->last_object_description.erase(7); // last_object_description starts with "object " + m->last_object_description += std::to_string(obj); + m->last_object_description += " 0"; + + bool empty = false; + auto object = QPDFParser(*input, m->last_object_description, m->tokenizer, nullptr, this, true) + .parse(empty, false); + if (empty) { + // Nothing in the PDF spec appears to allow empty objects, but they have been encountered in + // actual PDF files and Adobe Reader appears to ignore them. + warn(damagedPDF(*input, input->getLastOffset(), "empty object treated as null")); + } + return object; +} + +bool +QPDF::findEndstream() +{ + // Find endstream or endobj. Position the input at that token. + auto t = readToken(*m->file, 20); + if (t.isWord("endobj") || t.isWord("endstream")) { + m->file->seek(m->file->getLastOffset(), SEEK_SET); + return true; + } + return false; +} + +size_t +QPDF::recoverStreamLength( + std::shared_ptr input, QPDFObjGen og, qpdf_offset_t stream_offset) +{ + // Try to reconstruct stream length by looking for endstream or endobj + warn(damagedPDF(*input, stream_offset, "attempting to recover stream length")); + + PatternFinder ef(*this, &QPDF::findEndstream); + size_t length = 0; + if (m->file->findFirst("end", stream_offset, 0, ef)) { + length = toS(m->file->tell() - stream_offset); + // Reread endstream but, if it was endobj, don't skip that. + QPDFTokenizer::Token t = readToken(*m->file); + if (t.getValue() == "endobj") { + m->file->seek(m->file->getLastOffset(), SEEK_SET); + } + } + + if (length) { + auto end = stream_offset + toO(length); + qpdf_offset_t found_offset = 0; + QPDFObjGen found_og; + + // Make sure this is inside this object + for (auto const& [current_og, entry]: m->xref_table) { + if (entry.getType() == 1) { + qpdf_offset_t obj_offset = entry.getOffset(); + if (found_offset < obj_offset && obj_offset < end) { + found_offset = obj_offset; + found_og = current_og; + } + } + } + if (!found_offset || found_og == og) { + // If we are trying to recover an XRef stream the xref table will not contain and + // won't contain any entries, therefore we cannot check the found length. Otherwise we + // found endstream\nendobj within the space allowed for this object, so we're probably + // in good shape. + } else { + QTC::TC("qpdf", "QPDF found wrong endstream in recovery"); + length = 0; + } + } + + if (length == 0) { + warn(damagedPDF( + *input, stream_offset, "unable to recover stream data; treating stream as empty")); + } else { + warn(damagedPDF( + *input, stream_offset, "recovered stream length: " + std::to_string(length))); + } + + QTC::TC("qpdf", "QPDF recovered stream length"); + return length; +} + +QPDFTokenizer::Token +QPDF::readToken(InputSource& input, size_t max_len) +{ + return m->tokenizer.readToken(input, m->last_object_description, true, max_len); +} + +QPDFObjectHandle +QPDF::readObjectAtOffset( + bool try_recovery, qpdf_offset_t offset, - std::string const& message) + std::string const& description, + QPDFObjGen exp_og, + QPDFObjGen& og, + bool skip_cache_if_in_xref) +{ + bool check_og = true; + if (exp_og.getObj() == 0) { + // This method uses an expect object ID of 0 to indicate that we don't know or don't care + // what the actual object ID is at this offset. This is true when we read the xref stream + // and linearization hint streams. In this case, we don't verify the expect object + // ID/generation against what was read from the file. There is also no reason to attempt + // xref recovery if we get a failure in this case since the read attempt was not triggered + // by an xref lookup. + check_og = false; + try_recovery = false; + } + setLastObjectDescription(description, exp_og); + + if (!m->attempt_recovery) { + try_recovery = false; + } + + // Special case: if offset is 0, just return null. Some PDF writers, in particular + // "Mac OS X 10.7.5 Quartz PDFContext", may store deleted objects in the xref table as + // "0000000000 00000 n", which is not correct, but it won't hurt anything for us to ignore + // these. + if (offset == 0) { + QTC::TC("qpdf", "QPDF bogus 0 offset", 0); + warn(damagedPDF(0, "object has offset 0")); + return QPDFObjectHandle::newNull(); + } + + m->file->seek(offset, SEEK_SET); + try { + QPDFTokenizer::Token tobjid = readToken(*m->file); + bool objidok = tobjid.isInteger(); + QTC::TC("qpdf", "QPDF check objid", objidok ? 1 : 0); + if (!objidok) { + QTC::TC("qpdf", "QPDF expected n n obj"); + throw damagedPDF(offset, "expected n n obj"); + } + QPDFTokenizer::Token tgen = readToken(*m->file); + bool genok = tgen.isInteger(); + QTC::TC("qpdf", "QPDF check generation", genok ? 1 : 0); + if (!genok) { + throw damagedPDF(offset, "expected n n obj"); + } + QPDFTokenizer::Token tobj = readToken(*m->file); + + bool objok = tobj.isWord("obj"); + QTC::TC("qpdf", "QPDF check obj", objok ? 1 : 0); + + if (!objok) { + throw damagedPDF(offset, "expected n n obj"); + } + int objid = QUtil::string_to_int(tobjid.getValue().c_str()); + int generation = QUtil::string_to_int(tgen.getValue().c_str()); + og = QPDFObjGen(objid, generation); + if (objid == 0) { + QTC::TC("qpdf", "QPDF object id 0"); + throw damagedPDF(offset, "object with ID 0"); + } + if (check_og && (exp_og != og)) { + QTC::TC("qpdf", "QPDF err wrong objid/generation"); + QPDFExc e = damagedPDF(offset, "expected " + exp_og.unparse(' ') + " obj"); + if (try_recovery) { + // Will be retried below + throw e; + } else { + // We can try reading the object anyway even if the ID doesn't match. + warn(e); + } + } + } catch (QPDFExc& e) { + if (try_recovery) { + // Try again after reconstructing xref table + reconstruct_xref(e); + if (m->xref_table.count(exp_og) && (m->xref_table[exp_og].getType() == 1)) { + qpdf_offset_t new_offset = m->xref_table[exp_og].getOffset(); + QPDFObjectHandle result = + readObjectAtOffset(false, new_offset, description, exp_og, og, false); + QTC::TC("qpdf", "QPDF recovered in readObjectAtOffset"); + return result; + } else { + QTC::TC("qpdf", "QPDF object gone after xref reconstruction"); + warn(damagedPDF( + "", + 0, + ("object " + exp_og.unparse(' ') + + " not found in file after regenerating cross reference " + "table"))); + return QPDFObjectHandle::newNull(); + } + } else { + throw; + } + } + + QPDFObjectHandle oh = readObject(description, og); + + if (isUnresolved(og)) { + // Store the object in the cache here so it gets cached whether we first know the offset or + // whether we first know the object ID and generation (in which we case we would get here + // through resolve). + + // Determine the end offset of this object before and after white space. We use these + // numbers to validate linearization hint tables. Offsets and lengths of objects may imply + // the end of an object to be anywhere between these values. + qpdf_offset_t end_before_space = m->file->tell(); + + // skip over spaces + while (true) { + char ch; + if (m->file->read(&ch, 1)) { + if (!isspace(static_cast(ch))) { + m->file->seek(-1, SEEK_CUR); + break; + } + } else { + throw damagedPDF(m->file->tell(), "EOF after endobj"); + } + } + qpdf_offset_t end_after_space = m->file->tell(); + if (skip_cache_if_in_xref && m->xref_table.count(og)) { + // Ordinarily, an object gets read here when resolved through xref table or stream. In + // the special case of the xref stream and linearization hint tables, the offset comes + // from another source. For the specific case of xref streams, the xref stream is read + // and loaded into the object cache very early in parsing. Ordinarily, when a file is + // updated by appending, items inserted into the xref table in later updates take + // precedence over earlier items. In the special case of reusing the object number + // previously used as the xref stream, we have the following order of events: + // + // * reused object gets loaded into the xref table + // * old object is read here while reading xref streams + // * original xref entry is ignored (since already in xref table) + // + // It is the second step that causes a problem. Even though the xref table is correct in + // this case, the old object is already in the cache and so effectively prevails over + // the reused object. To work around this issue, we have a special case for the xref + // stream (via the skip_cache_if_in_xref): if the object is already in the xref stream, + // don't cache what we read here. + // + // It is likely that the same bug may exist for linearization hint tables, but the + // existing code uses end_before_space and end_after_space from the cache, so fixing + // that would require more significant rework. The chances of a linearization hint + // stream being reused seems smaller because the xref stream is probably the highest + // object in the file and the linearization hint stream would be some random place in + // the middle, so I'm leaving that bug unfixed for now. If the bug were to be fixed, we + // could use !check_og in place of skip_cache_if_in_xref. + QTC::TC("qpdf", "QPDF skipping cache for known unchecked object"); + } else { + updateCache(og, oh.getObj(), end_before_space, end_after_space); + } + } + + return oh; +} + +std::shared_ptr const& +QPDF::resolve(QPDFObjGen og) { - warn(QPDFExc(error_code, getFilename(), object, offset, message)); + if (!isUnresolved(og)) { + return m->obj_cache[og].object; + } + + if (m->resolving.count(og)) { + // This can happen if an object references itself directly or indirectly in some key that + // has to be resolved during object parsing, such as stream length. + QTC::TC("qpdf", "QPDF recursion loop in resolve"); + warn(damagedPDF("", "loop detected resolving object " + og.unparse(' '))); + updateCache(og, QPDFObject::create(), -1, -1); + return m->obj_cache[og].object; + } + ResolveRecorder rr(this, og); + + if (m->xref_table.count(og) != 0) { + QPDFXRefEntry const& entry = m->xref_table[og]; + try { + switch (entry.getType()) { + case 1: + { + qpdf_offset_t offset = entry.getOffset(); + // Object stored in cache by readObjectAtOffset + QPDFObjGen a_og; + QPDFObjectHandle oh = readObjectAtOffset(true, offset, "", og, a_og, false); + } + break; + + case 2: + resolveObjectsInStream(entry.getObjStreamNumber()); + break; + + default: + throw damagedPDF( + "", 0, ("object " + og.unparse('/') + " has unexpected xref entry type")); + } + } catch (QPDFExc& e) { + warn(e); + } catch (std::exception& e) { + warn(damagedPDF( + "", 0, ("object " + og.unparse('/') + ": error reading object: " + e.what()))); + } + } + + if (isUnresolved(og)) { + // PDF spec says unknown objects resolve to the null object. + QTC::TC("qpdf", "QPDF resolve failure to null"); + updateCache(og, QPDFObject::create(), -1, -1); + } + + auto& result(m->obj_cache[og].object); + result->setDefaultDescription(this, og); + return result; +} + +void +QPDF::resolveObjectsInStream(int obj_stream_number) +{ + if (m->resolved_object_streams.count(obj_stream_number)) { + return; + } + m->resolved_object_streams.insert(obj_stream_number); + // Force resolution of object stream + QPDFObjectHandle obj_stream = getObjectByID(obj_stream_number, 0); + if (!obj_stream.isStream()) { + throw damagedPDF( + "supposed object stream " + std::to_string(obj_stream_number) + " is not a stream"); + } + + // For linearization data in the object, use the data from the object stream for the objects in + // the stream. + QPDFObjGen stream_og(obj_stream_number, 0); + qpdf_offset_t end_before_space = m->obj_cache[stream_og].end_before_space; + qpdf_offset_t end_after_space = m->obj_cache[stream_og].end_after_space; + + QPDFObjectHandle dict = obj_stream.getDict(); + if (!dict.isDictionaryOfType("/ObjStm")) { + QTC::TC("qpdf", "QPDF ERR object stream with wrong type"); + warn(damagedPDF( + "supposed object stream " + std::to_string(obj_stream_number) + " has wrong type")); + } + + if (!(dict.getKey("/N").isInteger() && dict.getKey("/First").isInteger())) { + throw damagedPDF( + ("object stream " + std::to_string(obj_stream_number) + " has incorrect keys")); + } + + int n = dict.getKey("/N").getIntValueAsInt(); + int first = dict.getKey("/First").getIntValueAsInt(); + + std::map offsets; + + std::shared_ptr bp = obj_stream.getStreamData(qpdf_dl_specialized); + auto input = std::shared_ptr( + // line-break + new BufferInputSource( + (m->file->getName() + " object stream " + std::to_string(obj_stream_number)), + bp.get())); + + long long last_offset = -1; + for (int i = 0; i < n; ++i) { + QPDFTokenizer::Token tnum = readToken(*input); + QPDFTokenizer::Token toffset = readToken(*input); + if (!(tnum.isInteger() && toffset.isInteger())) { + throw damagedPDF( + *input, + m->last_object_description, + input->getLastOffset(), + "expected integer in object stream header"); + } + + int num = QUtil::string_to_int(tnum.getValue().c_str()); + long long offset = QUtil::string_to_int(toffset.getValue().c_str()); + + if (num == obj_stream_number) { + QTC::TC("qpdf", "QPDF ignore self-referential object stream"); + warn(damagedPDF( + *input, + m->last_object_description, + input->getLastOffset(), + "object stream claims to contain itself")); + continue; + } + + if (num < 1) { + QTC::TC("qpdf", "QPDF object stream contains id < 1"); + warn(damagedPDF( + *input, + "object "s + std::to_string(num) + " 0, offset " + std::to_string(offset), + 0, + "object id is invalid"s)); + continue; + } + + if (offset <= last_offset) { + QTC::TC("qpdf", "QPDF object stream offsets not increasing"); + warn(damagedPDF( + *input, + "object "s + std::to_string(num) + " 0, offset " + std::to_string(offset), + 0, + "offset is invalid (must be larger than previous offset " + + std::to_string(last_offset) + ")")); + continue; + } + last_offset = offset; + + if (num > m->xref_table_max_id) { + continue; + } + + offsets[num] = toI(offset + first); + } + + // To avoid having to read the object stream multiple times, store all objects that would be + // found here in the cache. Remember that some objects stored here might have been overridden + // by new objects appended to the file, so it is necessary to recheck the xref table and only + // cache what would actually be resolved here. + m->last_object_description.clear(); + m->last_object_description += "object "; + for (auto const& iter: offsets) { + QPDFObjGen og(iter.first, 0); + auto entry = m->xref_table.find(og); + if (entry != m->xref_table.end() && entry->second.getType() == 2 && + entry->second.getObjStreamNumber() == obj_stream_number) { + int offset = iter.second; + input->seek(offset, SEEK_SET); + QPDFObjectHandle oh = readObjectInStream(input, iter.first); + updateCache(og, oh.getObj(), end_before_space, end_after_space); + } else { + QTC::TC("qpdf", "QPDF not caching overridden objstm object"); + } + } +} + +QPDFObjectHandle +QPDF::newIndirect(QPDFObjGen og, std::shared_ptr const& obj) +{ + obj->setDefaultDescription(this, og); + return {obj}; +} + +void +QPDF::updateCache( + QPDFObjGen og, + std::shared_ptr const& object, + qpdf_offset_t end_before_space, + qpdf_offset_t end_after_space, + bool destroy) +{ + object->setObjGen(this, og); + if (isCached(og)) { + auto& cache = m->obj_cache[og]; + object->move_to(cache.object, destroy); + cache.end_before_space = end_before_space; + cache.end_after_space = end_after_space; + } else { + m->obj_cache[og] = ObjCache(object, end_before_space, end_after_space); + } +} + +bool +QPDF::isCached(QPDFObjGen og) +{ + return m->obj_cache.count(og) != 0; +} + +bool +QPDF::isUnresolved(QPDFObjGen og) +{ + return !isCached(og) || m->obj_cache[og].object->isUnresolved(); +} + +QPDFObjGen +QPDF::nextObjGen() +{ + int max_objid = toI(getObjectCount()); + if (max_objid == std::numeric_limits::max()) { + throw std::range_error("max object id is too high to create new objects"); + } + return QPDFObjGen(max_objid + 1, 0); +} + +QPDFObjectHandle +QPDF::makeIndirectFromQPDFObject(std::shared_ptr const& obj) +{ + QPDFObjGen next{nextObjGen()}; + m->obj_cache[next] = ObjCache(obj, -1, -1); + return newIndirect(next, m->obj_cache[next].object); +} + +QPDFObjectHandle +QPDF::makeIndirectObject(QPDFObjectHandle oh) +{ + if (!oh) { + throw std::logic_error("attempted to make an uninitialized QPDFObjectHandle indirect"); + } + return makeIndirectFromQPDFObject(oh.getObj()); } QPDFObjectHandle @@ -470,6 +2170,52 @@ QPDF::newStream(std::string const& data) return result; } +std::shared_ptr +QPDF::getObjectForParser(int id, int gen, bool parse_pdf) +{ + // This method is called by the parser and therefore must not resolve any objects. + auto og = QPDFObjGen(id, gen); + if (auto iter = m->obj_cache.find(og); iter != m->obj_cache.end()) { + return iter->second.object; + } + if (m->xref_table.count(og) || !m->parsed) { + return m->obj_cache.insert({og, QPDFObject::create(this, og)}) + .first->second.object; + } + if (parse_pdf) { + return QPDFObject::create(); + } + return m->obj_cache.insert({og, QPDFObject::create(this, og)}).first->second.object; +} + +std::shared_ptr +QPDF::getObjectForJSON(int id, int gen) +{ + auto og = QPDFObjGen(id, gen); + auto [it, inserted] = m->obj_cache.try_emplace(og); + auto& obj = it->second.object; + if (inserted) { + obj = (m->parsed && !m->xref_table.count(og)) + ? QPDFObject::create(this, og) + : QPDFObject::create(this, og); + } + return obj; +} + +QPDFObjectHandle +QPDF::getObject(QPDFObjGen og) +{ + if (auto it = m->obj_cache.find(og); it != m->obj_cache.end()) { + return {it->second.object}; + } else if (m->parsed && !m->xref_table.count(og)) { + return QPDFObject::create(); + } else { + auto result = + m->obj_cache.try_emplace(og, QPDFObject::create(this, og), -1, -1); + return {result.first->second.object}; + } +} + QPDFObjectHandle QPDF::getObject(int objid, int generation) { @@ -488,6 +2234,45 @@ QPDF::getObjectByID(int objid, int generation) return getObject(QPDFObjGen(objid, generation)); } +void +QPDF::replaceObject(int objid, int generation, QPDFObjectHandle oh) +{ + replaceObject(QPDFObjGen(objid, generation), oh); +} + +void +QPDF::replaceObject(QPDFObjGen og, QPDFObjectHandle oh) +{ + if (!oh || (oh.isIndirect() && !(oh.isStream() && oh.getObjGen() == og))) { + QTC::TC("qpdf", "QPDF replaceObject called with indirect object"); + throw std::logic_error("QPDF::replaceObject called with indirect object handle"); + } + updateCache(og, oh.getObj(), -1, -1, false); +} + +void +QPDF::removeObject(QPDFObjGen og) +{ + m->xref_table.erase(og); + if (auto cached = m->obj_cache.find(og); cached != m->obj_cache.end()) { + // Take care of any object handles that may be floating around. + cached->second.object->assign_null(); + cached->second.object->setObjGen(nullptr, QPDFObjGen()); + m->obj_cache.erase(cached); + } +} + +void +QPDF::replaceReserved(QPDFObjectHandle reserved, QPDFObjectHandle replacement) +{ + QTC::TC("qpdf", "QPDF replaceReserved"); + auto tc = reserved.getTypeCode(); + if (!(tc == ::ot_reserved || tc == ::ot_null)) { + throw std::logic_error("replaceReserved called with non-reserved object"); + } + replaceObject(reserved.getObjGen(), replacement); +} + QPDFObjectHandle QPDF::copyForeignObject(QPDFObjectHandle foreign) { @@ -747,6 +2532,21 @@ QPDF::copyStreamData(QPDFObjectHandle result, QPDFObjectHandle foreign) } } +void +QPDF::swapObjects(int objid1, int generation1, int objid2, int generation2) +{ + swapObjects(QPDFObjGen(objid1, generation1), QPDFObjGen(objid2, generation2)); +} + +void +QPDF::swapObjects(QPDFObjGen og1, QPDFObjGen og2) +{ + // Force objects to be read from the input source if needed, then swap them in the cache. + resolve(og1); + resolve(og2); + m->obj_cache[og1].object->swapWith(m->obj_cache[og2].object); +} + unsigned long long QPDF::getUniqueId() const { @@ -840,6 +2640,136 @@ QPDF::getXRefTableInternal() return m->xref_table; } +size_t +QPDF::tableSize() +{ + // If obj_cache is dense, accommodate all object in tables,else accommodate only original + // objects. + auto max_xref = m->xref_table.size() ? m->xref_table.crbegin()->first.getObj() : 0; + auto max_obj = m->obj_cache.size() ? m->obj_cache.crbegin()->first.getObj() : 0; + auto max_id = std::numeric_limits::max() - 1; + if (max_obj >= max_id || max_xref >= max_id) { + // Temporary fix. Long-term solution is + // - QPDFObjGen to enforce objgens are valid and sensible + // - xref table and obj cache to protect against insertion of impossibly large obj ids + stopOnError("Impossibly large object id encountered."); + } + if (max_obj < 1.1 * std::max(toI(m->obj_cache.size()), max_xref)) { + return toS(++max_obj); + } + return toS(++max_xref); +} + +std::vector +QPDF::getCompressibleObjVector() +{ + return getCompressibleObjGens(); +} + +std::vector +QPDF::getCompressibleObjSet() +{ + return getCompressibleObjGens(); +} + +template +std::vector +QPDF::getCompressibleObjGens() +{ + // Return a list of objects that are allowed to be in object streams. Walk through the objects + // by traversing the document from the root, including a traversal of the pages tree. This + // makes that objects that are on the same page are more likely to be in the same object stream, + // which is slightly more efficient, particularly with linearized files. This is better than + // iterating through the xref table since it avoids preserving orphaned items. + + // Exclude encryption dictionary, if any + QPDFObjectHandle encryption_dict = m->trailer.getKey("/Encrypt"); + QPDFObjGen encryption_dict_og = encryption_dict.getObjGen(); + + const size_t max_obj = getObjectCount(); + std::vector visited(max_obj, false); + std::vector queue; + queue.reserve(512); + queue.push_back(m->trailer); + std::vector result; + if constexpr (std::is_same_v) { + result.reserve(m->obj_cache.size()); + } else if constexpr (std::is_same_v) { + result.resize(max_obj + 1U, false); + } else { + throw std::logic_error("Unsupported type in QPDF::getCompressibleObjGens"); + } + while (!queue.empty()) { + auto obj = queue.back(); + queue.pop_back(); + if (obj.getObjectID() > 0) { + QPDFObjGen og = obj.getObjGen(); + const size_t id = toS(og.getObj() - 1); + if (id >= max_obj) { + throw std::logic_error( + "unexpected object id encountered in getCompressibleObjGens"); + } + if (visited[id]) { + QTC::TC("qpdf", "QPDF loop detected traversing objects"); + continue; + } + + // Check whether this is the current object. If not, remove it (which changes it into a + // direct null and therefore stops us from revisiting it) and move on to the next object + // in the queue. + auto upper = m->obj_cache.upper_bound(og); + if (upper != m->obj_cache.end() && upper->first.getObj() == og.getObj()) { + removeObject(og); + continue; + } + + visited[id] = true; + + if (og == encryption_dict_og) { + QTC::TC("qpdf", "QPDF exclude encryption dictionary"); + } else if (!(obj.isStream() || + (obj.isDictionaryOfType("/Sig") && obj.hasKey("/ByteRange") && + obj.hasKey("/Contents")))) { + if constexpr (std::is_same_v) { + result.push_back(og); + } else if constexpr (std::is_same_v) { + result[id + 1U] = true; + } + } + } + if (obj.isStream()) { + auto dict = obj.getDict().as_dictionary(); + auto end = dict.crend(); + for (auto iter = dict.crbegin(); iter != end; ++iter) { + std::string const& key = iter->first; + QPDFObjectHandle const& value = iter->second; + if (!value.null()) { + if (key == "/Length") { + // omit stream lengths + if (value.isIndirect()) { + QTC::TC("qpdf", "QPDF exclude indirect length"); + } + } else { + queue.emplace_back(value); + } + } + } + } else if (obj.isDictionary()) { + auto dict = obj.as_dictionary(); + auto end = dict.crend(); + for (auto iter = dict.crbegin(); iter != end; ++iter) { + if (!iter->second.null()) { + queue.emplace_back(iter->second); + } + } + } else if (auto items = obj.as_array()) { + queue.insert(queue.end(), items.crbegin(), items.crend()); + } + } + + return result; +} + bool QPDF::pipeStreamData( std::shared_ptr encp, diff --git a/libqpdf/QPDF_objects.cc b/libqpdf/QPDF_objects.cc deleted file mode 100644 index 121dde6..0000000 --- a/libqpdf/QPDF_objects.cc +++ /dev/null @@ -1,2017 +0,0 @@ -#include // include first for large file support - -#include - -#include -#include -#include -#include -#include -#include -#include -#include - -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include - -using namespace qpdf; -using namespace std::literals; - -namespace -{ - class InvalidInputSource: public InputSource - { - public: - ~InvalidInputSource() override = default; - qpdf_offset_t - findAndSkipNextEOL() override - { - throwException(); - return 0; - } - std::string const& - getName() const override - { - static std::string name("closed input source"); - return name; - } - qpdf_offset_t - tell() override - { - throwException(); - return 0; - } - void - seek(qpdf_offset_t offset, int whence) override - { - throwException(); - } - void - rewind() override - { - throwException(); - } - size_t - read(char* buffer, size_t length) override - { - throwException(); - return 0; - } - void - unreadCh(char ch) override - { - throwException(); - } - - private: - void - throwException() - { - throw std::logic_error( - "QPDF operation attempted on a QPDF object with no input " - "source. QPDF operations are invalid before processFile (or " - "another process method) or after closeInputSource"); - } - }; -} // namespace - -bool -QPDF::findStartxref() -{ - if (readToken(*m->file).isWord("startxref") && readToken(*m->file).isInteger()) { - // Position in front of offset token - m->file->seek(m->file->getLastOffset(), SEEK_SET); - return true; - } - return false; -} - -void -QPDF::parse(char const* password) -{ - if (password) { - m->encp->provided_password = password; - } - - // Find the header anywhere in the first 1024 bytes of the file. - PatternFinder hf(*this, &QPDF::findHeader); - if (!m->file->findFirst("%PDF-", 0, 1024, hf)) { - QTC::TC("qpdf", "QPDF not a pdf file"); - warn(damagedPDF("", 0, "can't find PDF header")); - // QPDFWriter writes files that usually require at least version 1.2 for /FlateDecode - m->pdf_version = "1.2"; - } - - // PDF spec says %%EOF must be found within the last 1024 bytes of/ the file. We add an extra - // 30 characters to leave room for the startxref stuff. - m->file->seek(0, SEEK_END); - qpdf_offset_t end_offset = m->file->tell(); - m->xref_table_max_offset = end_offset; - // Sanity check on object ids. All objects must appear in xref table / stream. In all realistic - // scenarios at least 3 bytes are required. - if (m->xref_table_max_id > m->xref_table_max_offset / 3) { - m->xref_table_max_id = static_cast(m->xref_table_max_offset / 3); - } - qpdf_offset_t start_offset = (end_offset > 1054 ? end_offset - 1054 : 0); - PatternFinder sf(*this, &QPDF::findStartxref); - qpdf_offset_t xref_offset = 0; - if (m->file->findLast("startxref", start_offset, 0, sf)) { - xref_offset = QUtil::string_to_ll(readToken(*m->file).getValue().c_str()); - } - - try { - if (xref_offset == 0) { - QTC::TC("qpdf", "QPDF can't find startxref"); - throw damagedPDF("", 0, "can't find startxref"); - } - try { - read_xref(xref_offset); - } catch (QPDFExc&) { - throw; - } catch (std::exception& e) { - throw damagedPDF("", 0, std::string("error reading xref: ") + e.what()); - } - } catch (QPDFExc& e) { - if (m->attempt_recovery) { - reconstruct_xref(e, xref_offset > 0); - QTC::TC("qpdf", "QPDF reconstructed xref table"); - } else { - throw; - } - } - - initializeEncryption(); - m->parsed = true; - if (m->xref_table.size() > 0 && !getRoot().getKey("/Pages").isDictionary()) { - // QPDFs created from JSON have an empty xref table and no root object yet. - throw damagedPDF("", 0, "unable to find page tree"); - } -} - -void -QPDF::inParse(bool v) -{ - if (m->in_parse == v) { - // This happens if QPDFParser::parse tries to resolve an indirect object while it is - // parsing. - throw std::logic_error( - "QPDF: re-entrant parsing detected. This is a qpdf bug." - " Please report at https://github.com/qpdf/qpdf/issues."); - } - m->in_parse = v; -} - -void -QPDF::setTrailer(QPDFObjectHandle obj) -{ - if (m->trailer) { - return; - } - m->trailer = obj; -} - -void -QPDF::reconstruct_xref(QPDFExc& e, bool found_startxref) -{ - if (m->reconstructed_xref) { - // Avoid xref reconstruction infinite loops. This is getting very hard to reproduce because - // qpdf is throwing many fewer exceptions while parsing. Most situations are warnings now. - throw e; - } - - // If recovery generates more than 1000 warnings, the file is so severely damaged that there - // probably is no point trying to continue. - const auto max_warnings = m->warnings.size() + 1000U; - auto check_warnings = [this, max_warnings]() { - if (m->warnings.size() > max_warnings) { - throw damagedPDF("", 0, "too many errors while reconstructing cross-reference table"); - } - }; - - m->reconstructed_xref = true; - // We may find more objects, which may contain dangling references. - m->fixed_dangling_refs = false; - - warn(damagedPDF("", 0, "file is damaged")); - warn(e); - warn(damagedPDF("", 0, "Attempting to reconstruct cross-reference table")); - - // Delete all references to type 1 (uncompressed) objects - std::vector to_delete; - for (auto const& iter: m->xref_table) { - if (iter.second.getType() == 1) { - to_delete.emplace_back(iter.first); - } - } - for (auto const& iter: to_delete) { - m->xref_table.erase(iter); - } - - std::vector> found_objects; - std::vector trailers; - std::vector startxrefs; - - m->file->seek(0, SEEK_END); - qpdf_offset_t eof = m->file->tell(); - m->file->seek(0, SEEK_SET); - // Don't allow very long tokens here during recovery. All the interesting tokens are covered. - static size_t const MAX_LEN = 10; - while (m->file->tell() < eof) { - QPDFTokenizer::Token t1 = readToken(*m->file, MAX_LEN); - qpdf_offset_t token_start = m->file->tell() - toO(t1.getValue().length()); - if (t1.isInteger()) { - auto pos = m->file->tell(); - auto t2 = readToken(*m->file, MAX_LEN); - if (t2.isInteger() && readToken(*m->file, MAX_LEN).isWord("obj")) { - int obj = QUtil::string_to_int(t1.getValue().c_str()); - int gen = QUtil::string_to_int(t2.getValue().c_str()); - if (obj <= m->xref_table_max_id) { - found_objects.emplace_back(obj, gen, token_start); - } else { - warn(damagedPDF( - "", 0, "ignoring object with impossibly large id " + std::to_string(obj))); - } - } - m->file->seek(pos, SEEK_SET); - } else if (!m->trailer && t1.isWord("trailer")) { - trailers.emplace_back(m->file->tell()); - } else if (!found_startxref && t1.isWord("startxref")) { - startxrefs.emplace_back(m->file->tell()); - } - check_warnings(); - m->file->findAndSkipNextEOL(); - } - - if (!found_startxref && !startxrefs.empty() && !found_objects.empty() && - startxrefs.back() > std::get<2>(found_objects.back())) { - try { - m->file->seek(startxrefs.back(), SEEK_SET); - if (auto offset = QUtil::string_to_ll(readToken(*m->file).getValue().data())) { - read_xref(offset); - if (getRoot().getKey("/Pages").isDictionary()) { - QTC::TC("qpdf", "QPDF startxref more than 1024 before end"); - warn( - damagedPDF("", 0, "startxref was more than 1024 bytes before end of file")); - initializeEncryption(); - m->parsed = true; - m->reconstructed_xref = false; - return; - } - } - } catch (...) { - // ok, bad luck. Do recovery. - } - } - - auto rend = found_objects.rend(); - for (auto it = found_objects.rbegin(); it != rend; it++) { - auto [obj, gen, token_start] = *it; - insertXrefEntry(obj, 1, token_start, gen); - check_warnings(); - } - m->deleted_objects.clear(); - - for (auto it = trailers.rbegin(); it != trailers.rend(); it++) { - m->file->seek(*it, SEEK_SET); - auto t = readTrailer(); - if (!t.isDictionary()) { - // Oh well. It was worth a try. - } else { - if (t.hasKey("/Root")) { - m->trailer = t; - break; - } - warn(damagedPDF("trailer", *it, "recovered trailer has no /Root entry")); - } - check_warnings(); - } - - if (!m->trailer) { - qpdf_offset_t max_offset{0}; - size_t max_size{0}; - // If there are any xref streams, take the last one to appear. - for (auto const& iter: m->xref_table) { - auto entry = iter.second; - if (entry.getType() != 1) { - continue; - } - auto oh = getObject(iter.first); - try { - if (!oh.isStreamOfType("/XRef")) { - continue; - } - } catch (std::exception&) { - continue; - } - auto offset = entry.getOffset(); - auto size = oh.getDict().getKey("/Size").getUIntValueAsUInt(); - if (size > max_size || (size == max_size && offset > max_offset)) { - max_offset = offset; - setTrailer(oh.getDict()); - } - check_warnings(); - } - if (max_offset > 0) { - try { - read_xref(max_offset); - } catch (std::exception&) { - warn(damagedPDF( - "", 0, "error decoding candidate xref stream while recovering damaged file")); - } - QTC::TC("qpdf", "QPDF recover xref stream"); - } - } - - if (!m->trailer || (!m->parsed && !m->trailer.getKey("/Root").isDictionary())) { - // Try to find a Root dictionary. As a quick fix try the one with the highest object id. - QPDFObjectHandle root; - for (auto const& iter: m->obj_cache) { - try { - if (QPDFObjectHandle(iter.second.object).isDictionaryOfType("/Catalog")) { - root = iter.second.object; - } - } catch (std::exception&) { - continue; - } - } - if (root) { - if (!m->trailer) { - warn(damagedPDF( - "", 0, "unable to find trailer dictionary while recovering damaged file")); - m->trailer = QPDFObjectHandle::newDictionary(); - } - m->trailer.replaceKey("/Root", root); - } - } - - if (!m->trailer) { - // We could check the last encountered object to see if it was an xref stream. If so, we - // could try to get the trailer from there. This may make it possible to recover files with - // bad startxref pointers even when they have object streams. - - throw damagedPDF("", 0, "unable to find trailer dictionary while recovering damaged file"); - } - if (m->xref_table.empty()) { - // We cannot check for an empty xref table in parse because empty tables are valid when - // creating QPDF objects from JSON. - throw damagedPDF("", 0, "unable to find objects while recovering damaged file"); - } - check_warnings(); - if (!m->parsed) { - m->parsed = true; - getAllPages(); - check_warnings(); - if (m->all_pages.empty()) { - m->parsed = false; - throw damagedPDF("", 0, "unable to find any pages while recovering damaged file"); - } - } - // We could iterate through the objects looking for streams and try to find objects inside of - // them, but it's probably not worth the trouble. Acrobat can't recover files with any errors - // in an xref stream, and this would be a real long shot anyway. If we wanted to do anything - // that involved looking at stream contents, we'd also have to call initializeEncryption() here. - // It's safe to call it more than once. -} - -void -QPDF::read_xref(qpdf_offset_t xref_offset) -{ - std::map free_table; - std::set visited; - while (xref_offset) { - visited.insert(xref_offset); - char buf[7]; - memset(buf, 0, sizeof(buf)); - m->file->seek(xref_offset, SEEK_SET); - // Some files miss the mark a little with startxref. We could do a better job of searching - // in the neighborhood for something that looks like either an xref table or stream, but the - // simple heuristic of skipping whitespace can help with the xref table case and is harmless - // with the stream case. - bool done = false; - bool skipped_space = false; - while (!done) { - char ch; - if (1 == m->file->read(&ch, 1)) { - if (util::is_space(ch)) { - skipped_space = true; - } else { - m->file->unreadCh(ch); - done = true; - } - } else { - QTC::TC("qpdf", "QPDF eof skipping spaces before xref", skipped_space ? 0 : 1); - done = true; - } - } - - m->file->read(buf, sizeof(buf) - 1); - // The PDF spec says xref must be followed by a line terminator, but files exist in the wild - // where it is terminated by arbitrary whitespace. - if ((strncmp(buf, "xref", 4) == 0) && util::is_space(buf[4])) { - if (skipped_space) { - QTC::TC("qpdf", "QPDF xref skipped space"); - warn(damagedPDF("", 0, "extraneous whitespace seen before xref")); - } - QTC::TC( - "qpdf", - "QPDF xref space", - ((buf[4] == '\n') ? 0 - : (buf[4] == '\r') ? 1 - : (buf[4] == ' ') ? 2 - : 9999)); - int skip = 4; - // buf is null-terminated, and util::is_space('\0') is false, so this won't overrun. - while (util::is_space(buf[skip])) { - ++skip; - } - xref_offset = read_xrefTable(xref_offset + skip); - } else { - xref_offset = read_xrefStream(xref_offset); - } - if (visited.count(xref_offset) != 0) { - QTC::TC("qpdf", "QPDF xref loop"); - throw damagedPDF("", 0, "loop detected following xref tables"); - } - } - - if (!m->trailer) { - throw damagedPDF("", 0, "unable to find trailer while reading xref"); - } - int size = m->trailer.getKey("/Size").getIntValueAsInt(); - int max_obj = 0; - if (!m->xref_table.empty()) { - max_obj = m->xref_table.rbegin()->first.getObj(); - } - if (!m->deleted_objects.empty()) { - max_obj = std::max(max_obj, *(m->deleted_objects.rbegin())); - } - if ((size < 1) || (size - 1 != max_obj)) { - QTC::TC("qpdf", "QPDF xref size mismatch"); - warn(damagedPDF( - "", - 0, - ("reported number of objects (" + std::to_string(size) + - ") is not one plus the highest object number (" + std::to_string(max_obj) + ")"))); - } - - // We no longer need the deleted_objects table, so go ahead and clear it out to make sure we - // never depend on its being set. - m->deleted_objects.clear(); - - // Make sure we keep only the highest generation for any object. - QPDFObjGen last_og{-1, 0}; - for (auto const& item: m->xref_table) { - auto id = item.first.getObj(); - if (id == last_og.getObj() && id > 0) { - removeObject(last_og); - } - last_og = item.first; - } -} - -bool -QPDF::parse_xrefFirst(std::string const& line, int& obj, int& num, int& bytes) -{ - // is_space and is_digit both return false on '\0', so this will not overrun the null-terminated - // buffer. - char const* p = line.c_str(); - char const* start = line.c_str(); - - // Skip zero or more spaces - while (util::is_space(*p)) { - ++p; - } - // Require digit - if (!util::is_digit(*p)) { - return false; - } - // Gather digits - std::string obj_str; - while (util::is_digit(*p)) { - obj_str.append(1, *p++); - } - // Require space - if (!util::is_space(*p)) { - return false; - } - // Skip spaces - while (util::is_space(*p)) { - ++p; - } - // Require digit - if (!util::is_digit(*p)) { - return false; - } - // Gather digits - std::string num_str; - while (util::is_digit(*p)) { - num_str.append(1, *p++); - } - // Skip any space including line terminators - while (util::is_space(*p)) { - ++p; - } - bytes = toI(p - start); - obj = QUtil::string_to_int(obj_str.c_str()); - num = QUtil::string_to_int(num_str.c_str()); - return true; -} - -bool -QPDF::read_bad_xrefEntry(qpdf_offset_t& f1, int& f2, char& type) -{ - // Reposition after initial read attempt and reread. - m->file->seek(m->file->getLastOffset(), SEEK_SET); - auto line = m->file->readLine(30); - - // is_space and is_digit both return false on '\0', so this will not overrun the null-terminated - // buffer. - char const* p = line.data(); - - // Skip zero or more spaces. There aren't supposed to be any. - bool invalid = false; - while (util::is_space(*p)) { - ++p; - QTC::TC("qpdf", "QPDF ignore first space in xref entry"); - invalid = true; - } - // Require digit - if (!util::is_digit(*p)) { - return false; - } - // Gather digits - std::string f1_str; - while (util::is_digit(*p)) { - f1_str.append(1, *p++); - } - // Require space - if (!util::is_space(*p)) { - return false; - } - if (util::is_space(*(p + 1))) { - QTC::TC("qpdf", "QPDF ignore first extra space in xref entry"); - invalid = true; - } - // Skip spaces - while (util::is_space(*p)) { - ++p; - } - // Require digit - if (!util::is_digit(*p)) { - return false; - } - // Gather digits - std::string f2_str; - while (util::is_digit(*p)) { - f2_str.append(1, *p++); - } - // Require space - if (!util::is_space(*p)) { - return false; - } - if (util::is_space(*(p + 1))) { - QTC::TC("qpdf", "QPDF ignore second extra space in xref entry"); - invalid = true; - } - // Skip spaces - while (util::is_space(*p)) { - ++p; - } - if ((*p == 'f') || (*p == 'n')) { - type = *p; - } else { - return false; - } - if ((f1_str.length() != 10) || (f2_str.length() != 5)) { - QTC::TC("qpdf", "QPDF ignore length error xref entry"); - invalid = true; - } - - if (invalid) { - warn(damagedPDF("xref table", "accepting invalid xref table entry")); - } - - f1 = QUtil::string_to_ll(f1_str.c_str()); - f2 = QUtil::string_to_int(f2_str.c_str()); - - return true; -} - -// Optimistically read and parse xref entry. If entry is bad, call read_bad_xrefEntry and return -// result. -bool -QPDF::read_xrefEntry(qpdf_offset_t& f1, int& f2, char& type) -{ - std::array line; - if (m->file->read(line.data(), 20) != 20) { - // C++20: [[unlikely]] - return false; - } - line[20] = '\0'; - char const* p = line.data(); - - int f1_len = 0; - int f2_len = 0; - - // is_space and is_digit both return false on '\0', so this will not overrun the null-terminated - // buffer. - - // Gather f1 digits. NB No risk of overflow as 9'999'999'999 < max long long. - while (*p == '0') { - ++f1_len; - ++p; - } - while (util::is_digit(*p) && f1_len++ < 10) { - f1 *= 10; - f1 += *p++ - '0'; - } - // Require space - if (!util::is_space(*p++)) { - // Entry doesn't start with space or digit. - // C++20: [[unlikely]] - return false; - } - // Gather digits. NB No risk of overflow as 99'999 < max int. - while (*p == '0') { - ++f2_len; - ++p; - } - while (util::is_digit(*p) && f2_len++ < 5) { - f2 *= 10; - f2 += static_cast(*p++ - '0'); - } - if (util::is_space(*p++) && (*p == 'f' || *p == 'n')) { - // C++20: [[likely]] - type = *p; - // No test for valid line[19]. - if (*(++p) && *(++p) && (*p == '\n' || *p == '\r') && f1_len == 10 && f2_len == 5) { - // C++20: [[likely]] - return true; - } - } - return read_bad_xrefEntry(f1, f2, type); -} - -// Read a single cross-reference table section and associated trailer. -qpdf_offset_t -QPDF::read_xrefTable(qpdf_offset_t xref_offset) -{ - m->file->seek(xref_offset, SEEK_SET); - std::string line; - while (true) { - line.assign(50, '\0'); - m->file->read(line.data(), line.size()); - int obj = 0; - int num = 0; - int bytes = 0; - if (!parse_xrefFirst(line, obj, num, bytes)) { - QTC::TC("qpdf", "QPDF invalid xref"); - throw damagedPDF("xref table", "xref syntax invalid"); - } - m->file->seek(m->file->getLastOffset() + bytes, SEEK_SET); - for (qpdf_offset_t i = obj; i - num < obj; ++i) { - if (i == 0) { - // This is needed by checkLinearization() - m->first_xref_item_offset = m->file->tell(); - } - // For xref_table, these will always be small enough to be ints - qpdf_offset_t f1 = 0; - int f2 = 0; - char type = '\0'; - if (!read_xrefEntry(f1, f2, type)) { - QTC::TC("qpdf", "QPDF invalid xref entry"); - throw damagedPDF( - "xref table", "invalid xref entry (obj=" + std::to_string(i) + ")"); - } - if (type == 'f') { - insertFreeXrefEntry(QPDFObjGen(toI(i), f2)); - } else { - insertXrefEntry(toI(i), 1, f1, f2); - } - } - qpdf_offset_t pos = m->file->tell(); - if (readToken(*m->file).isWord("trailer")) { - break; - } else { - m->file->seek(pos, SEEK_SET); - } - } - - // Set offset to previous xref table if any - QPDFObjectHandle cur_trailer = readTrailer(); - if (!cur_trailer.isDictionary()) { - QTC::TC("qpdf", "QPDF missing trailer"); - throw damagedPDF("", "expected trailer dictionary"); - } - - if (!m->trailer) { - setTrailer(cur_trailer); - - if (!m->trailer.hasKey("/Size")) { - QTC::TC("qpdf", "QPDF trailer lacks size"); - throw damagedPDF("trailer", "trailer dictionary lacks /Size key"); - } - if (!m->trailer.getKey("/Size").isInteger()) { - QTC::TC("qpdf", "QPDF trailer size not integer"); - throw damagedPDF("trailer", "/Size key in trailer dictionary is not an integer"); - } - } - - if (cur_trailer.hasKey("/XRefStm")) { - if (m->ignore_xref_streams) { - QTC::TC("qpdf", "QPDF ignoring XRefStm in trailer"); - } else { - if (cur_trailer.getKey("/XRefStm").isInteger()) { - // Read the xref stream but disregard any return value -- we'll use our trailer's - // /Prev key instead of the xref stream's. - (void)read_xrefStream(cur_trailer.getKey("/XRefStm").getIntValue()); - } else { - throw damagedPDF("xref stream", xref_offset, "invalid /XRefStm"); - } - } - } - - if (cur_trailer.hasKey("/Prev")) { - if (!cur_trailer.getKey("/Prev").isInteger()) { - QTC::TC("qpdf", "QPDF trailer prev not integer"); - throw damagedPDF("trailer", "/Prev key in trailer dictionary is not an integer"); - } - QTC::TC("qpdf", "QPDF prev key in trailer dictionary"); - return cur_trailer.getKey("/Prev").getIntValue(); - } - - return 0; -} - -// Read a single cross-reference stream. -qpdf_offset_t -QPDF::read_xrefStream(qpdf_offset_t xref_offset) -{ - if (!m->ignore_xref_streams) { - QPDFObjGen x_og; - QPDFObjectHandle xref_obj; - try { - xref_obj = - readObjectAtOffset(false, xref_offset, "xref stream", QPDFObjGen(0, 0), x_og, true); - } catch (QPDFExc&) { - // ignore -- report error below - } - if (xref_obj.isStreamOfType("/XRef")) { - QTC::TC("qpdf", "QPDF found xref stream"); - return processXRefStream(xref_offset, xref_obj); - } - } - - QTC::TC("qpdf", "QPDF can't find xref"); - throw damagedPDF("", xref_offset, "xref not found"); - return 0; // unreachable -} - -// Return the entry size of the xref stream and the processed W array. -std::pair> -QPDF::processXRefW(QPDFObjectHandle& dict, std::function damaged) -{ - auto W_obj = dict.getKey("/W"); - if (!(W_obj.isArray() && (W_obj.getArrayNItems() >= 3) && W_obj.getArrayItem(0).isInteger() && - W_obj.getArrayItem(1).isInteger() && W_obj.getArrayItem(2).isInteger())) { - throw damaged("Cross-reference stream does not have a proper /W key"); - } - - std::array W; - int entry_size = 0; - auto w_vector = W_obj.getArrayAsVector(); - int max_bytes = sizeof(qpdf_offset_t); - for (size_t i = 0; i < 3; ++i) { - W[i] = w_vector[i].getIntValueAsInt(); - if (W[i] > max_bytes) { - throw damaged("Cross-reference stream's /W contains impossibly large values"); - } - if (W[i] < 0) { - throw damaged("Cross-reference stream's /W contains negative values"); - } - entry_size += W[i]; - } - if (entry_size == 0) { - throw damaged("Cross-reference stream's /W indicates entry size of 0"); - } - return {entry_size, W}; -} - -// Validate Size key and return the maximum number of entries that the xref stream can contain. -int -QPDF::processXRefSize( - QPDFObjectHandle& dict, int entry_size, std::function damaged) -{ - // Number of entries is limited by the highest possible object id and stream size. - auto max_num_entries = std::numeric_limits::max(); - if (max_num_entries > (std::numeric_limits::max() / entry_size)) { - max_num_entries = toI(std::numeric_limits::max() / entry_size); - } - - auto Size_obj = dict.getKey("/Size"); - long long size; - if (!dict.getKey("/Size").getValueAsInt(size)) { - throw damaged("Cross-reference stream does not have a proper /Size key"); - } else if (size < 0) { - throw damaged("Cross-reference stream has a negative /Size key"); - } else if (size >= max_num_entries) { - throw damaged("Cross-reference stream has an impossibly large /Size key"); - } - // We are not validating that Size <= (Size key of parent xref / trailer). - return max_num_entries; -} - -// Return the number of entries of the xref stream and the processed Index array. -std::pair>> -QPDF::processXRefIndex( - QPDFObjectHandle& dict, int max_num_entries, std::function damaged) -{ - auto size = dict.getKey("/Size").getIntValueAsInt(); - auto Index_obj = dict.getKey("/Index"); - - if (Index_obj.isArray()) { - std::vector> indx; - int num_entries = 0; - auto index_vec = Index_obj.getArrayAsVector(); - if ((index_vec.size() % 2) || index_vec.size() < 2) { - throw damaged("Cross-reference stream's /Index has an invalid number of values"); - } - - int i = 0; - long long first = 0; - for (auto& val: index_vec) { - if (val.isInteger()) { - if (i % 2) { - auto count = val.getIntValue(); - if (count <= 0) { - throw damaged( - "Cross-reference stream section claims to contain " + - std::to_string(count) + " entries"); - } - // We are guarding against the possibility of num_entries * entry_size - // overflowing. We are not checking that entries are in ascending order as - // required by the spec, which probably should generate a warning. We are also - // not checking that for each subsection first object number + number of entries - // <= /Size. The spec requires us to ignore object number > /Size. - if (first > (max_num_entries - count) || - count > (max_num_entries - num_entries)) { - throw damaged( - "Cross-reference stream claims to contain too many entries: " + - std::to_string(first) + " " + std::to_string(max_num_entries) + " " + - std::to_string(num_entries)); - } - indx.emplace_back(static_cast(first), static_cast(count)); - num_entries += static_cast(count); - } else { - first = val.getIntValue(); - if (first < 0) { - throw damaged( - "Cross-reference stream's /Index contains a negative object id"); - } else if (first > max_num_entries) { - throw damaged( - "Cross-reference stream's /Index contains an impossibly " - "large object id"); - } - } - } else { - throw damaged( - "Cross-reference stream's /Index's item " + std::to_string(i) + - " is not an integer"); - } - i++; - } - QTC::TC("qpdf", "QPDF xref /Index is array", index_vec.size() == 2 ? 0 : 1); - return {num_entries, indx}; - } else if (Index_obj.isNull()) { - QTC::TC("qpdf", "QPDF xref /Index is null"); - return {size, {{0, size}}}; - } else { - throw damaged("Cross-reference stream does not have a proper /Index key"); - } -} - -qpdf_offset_t -QPDF::processXRefStream(qpdf_offset_t xref_offset, QPDFObjectHandle& xref_obj) -{ - auto damaged = [this, xref_offset](std::string_view msg) -> QPDFExc { - return damagedPDF("xref stream", xref_offset, msg.data()); - }; - - auto dict = xref_obj.getDict(); - - auto [entry_size, W] = processXRefW(dict, damaged); - int max_num_entries = processXRefSize(dict, entry_size, damaged); - auto [num_entries, indx] = processXRefIndex(dict, max_num_entries, damaged); - - std::shared_ptr bp = xref_obj.getStreamData(qpdf_dl_specialized); - size_t actual_size = bp->getSize(); - auto expected_size = toS(entry_size) * toS(num_entries); - - if (expected_size != actual_size) { - QPDFExc x = damaged( - "Cross-reference stream data has the wrong size; expected = " + - std::to_string(expected_size) + "; actual = " + std::to_string(actual_size)); - if (expected_size > actual_size) { - throw x; - } else { - warn(x); - } - } - - bool saw_first_compressed_object = false; - - // Actual size vs. expected size check above ensures that we will not overflow any buffers here. - // We know that entry_size * num_entries is less or equal to the size of the buffer. - auto p = bp->getBuffer(); - for (auto [obj, sec_entries]: indx) { - // Process a subsection. - for (int i = 0; i < sec_entries; ++i) { - // Read this entry - std::array fields{}; - if (W[0] == 0) { - QTC::TC("qpdf", "QPDF default for xref stream field 0"); - fields[0] = 1; - } - for (size_t j = 0; j < 3; ++j) { - for (int k = 0; k < W[j]; ++k) { - fields[j] <<= 8; - fields[j] |= *p++; - } - } - - // Get the generation number. The generation number is 0 unless this is an uncompressed - // object record, in which case the generation number appears as the third field. - if (saw_first_compressed_object) { - if (fields[0] != 2) { - m->uncompressed_after_compressed = true; - } - } else if (fields[0] == 2) { - saw_first_compressed_object = true; - } - if (obj == 0) { - // This is needed by checkLinearization() - m->first_xref_item_offset = xref_offset; - } else if (fields[0] == 0) { - // Ignore fields[2], which we don't care about in this case. This works around the - // issue of some PDF files that put invalid values, like -1, here for deleted - // objects. - insertFreeXrefEntry(QPDFObjGen(obj, 0)); - } else { - insertXrefEntry(obj, toI(fields[0]), fields[1], toI(fields[2])); - } - ++obj; - } - } - - if (!m->trailer) { - setTrailer(dict); - } - - if (dict.hasKey("/Prev")) { - if (!dict.getKey("/Prev").isInteger()) { - throw damagedPDF( - "xref stream", "/Prev key in xref stream dictionary is not an integer"); - } - QTC::TC("qpdf", "QPDF prev key in xref stream dictionary"); - return dict.getKey("/Prev").getIntValue(); - } else { - return 0; - } -} - -void -QPDF::insertXrefEntry(int obj, int f0, qpdf_offset_t f1, int f2) -{ - // Populate the xref table in such a way that the first reference to an object that we see, - // which is the one in the latest xref table in which it appears, is the one that gets stored. - // This works because we are reading more recent appends before older ones. - - // If there is already an entry for this object and generation in the table, it means that a - // later xref table has registered this object. Disregard this one. - int new_gen = f0 == 2 ? 0 : f2; - - if (!(obj > 0 && obj <= m->xref_table_max_id && 0 <= f2 && new_gen < 65535)) { - // We are ignoring invalid objgens. Most will arrive here from xref reconstruction. There - // is probably no point having another warning but we could count invalid items in order to - // decide when to give up. - QTC::TC("qpdf", "QPDF xref overwrite invalid objgen"); - // ignore impossibly large object ids or object ids > Size. - return; - } - - if (m->deleted_objects.count(obj)) { - QTC::TC("qpdf", "QPDF xref deleted object"); - return; - } - - if (f0 == 2 && static_cast(f1) == obj) { - warn(damagedPDF("xref stream", "self-referential object stream " + std::to_string(obj))); - return; - } - - auto [iter, created] = m->xref_table.try_emplace(QPDFObjGen(obj, (f0 == 2 ? 0 : f2))); - if (!created) { - QTC::TC("qpdf", "QPDF xref reused object"); - return; - } - - switch (f0) { - case 1: - // f2 is generation - QTC::TC("qpdf", "QPDF xref gen > 0", ((f2 > 0) ? 1 : 0)); - iter->second = QPDFXRefEntry(f1); - break; - - case 2: - iter->second = QPDFXRefEntry(toI(f1), f2); - break; - - default: - throw damagedPDF("xref stream", "unknown xref stream entry type " + std::to_string(f0)); - break; - } -} - -void -QPDF::insertFreeXrefEntry(QPDFObjGen og) -{ - if (!m->xref_table.count(og)) { - m->deleted_objects.insert(og.getObj()); - } -} - -void -QPDF::showXRefTable() -{ - auto& cout = *m->log->getInfo(); - for (auto const& iter: m->xref_table) { - QPDFObjGen const& og = iter.first; - QPDFXRefEntry const& entry = iter.second; - cout << og.unparse('/') << ": "; - switch (entry.getType()) { - case 1: - cout << "uncompressed; offset = " << entry.getOffset(); - break; - - case 2: - *m->log->getInfo() << "compressed; stream = " << entry.getObjStreamNumber() - << ", index = " << entry.getObjStreamIndex(); - break; - - default: - throw std::logic_error("unknown cross-reference table type while showing xref_table"); - break; - } - m->log->info("\n"); - } -} - -// Resolve all objects in the xref table. If this triggers a xref table reconstruction abort and -// return false. Otherwise return true. -bool -QPDF::resolveXRefTable() -{ - bool may_change = !m->reconstructed_xref; - for (auto& iter: m->xref_table) { - if (isUnresolved(iter.first)) { - resolve(iter.first); - if (may_change && m->reconstructed_xref) { - return false; - } - } - } - return true; -} - -// Ensure all objects in the pdf file, including those in indirect references, appear in the object -// cache. -void -QPDF::fixDanglingReferences(bool force) -{ - if (m->fixed_dangling_refs) { - return; - } - if (!resolveXRefTable()) { - QTC::TC("qpdf", "QPDF fix dangling triggered xref reconstruction"); - resolveXRefTable(); - } - m->fixed_dangling_refs = true; -} - -size_t -QPDF::getObjectCount() -{ - // This method returns the next available indirect object number. makeIndirectObject uses it for - // this purpose. After fixDanglingReferences is called, all objects in the xref table will also - // be in obj_cache. - fixDanglingReferences(); - QPDFObjGen og; - if (!m->obj_cache.empty()) { - og = (*(m->obj_cache.rbegin())).first; - } - return toS(og.getObj()); -} - -std::vector -QPDF::getAllObjects() -{ - // After fixDanglingReferences is called, all objects are in the object cache. - fixDanglingReferences(); - std::vector result; - for (auto const& iter: m->obj_cache) { - result.push_back(newIndirect(iter.first, iter.second.object)); - } - return result; -} - -void -QPDF::setLastObjectDescription(std::string const& description, QPDFObjGen og) -{ - m->last_object_description.clear(); - if (!description.empty()) { - m->last_object_description += description; - if (og.isIndirect()) { - m->last_object_description += ": "; - } - } - if (og.isIndirect()) { - m->last_object_description += "object " + og.unparse(' '); - } -} - -QPDFObjectHandle -QPDF::readTrailer() -{ - qpdf_offset_t offset = m->file->tell(); - bool empty = false; - auto object = - QPDFParser(*m->file, "trailer", m->tokenizer, nullptr, this, true).parse(empty, false); - if (empty) { - // Nothing in the PDF spec appears to allow empty objects, but they have been encountered in - // actual PDF files and Adobe Reader appears to ignore them. - warn(damagedPDF("trailer", "empty object treated as null")); - } else if (object.isDictionary() && readToken(*m->file).isWord("stream")) { - warn(damagedPDF("trailer", m->file->tell(), "stream keyword found in trailer")); - } - // Override last_offset so that it points to the beginning of the object we just read - m->file->setLastOffset(offset); - return object; -} - -QPDFObjectHandle -QPDF::readObject(std::string const& description, QPDFObjGen og) -{ - setLastObjectDescription(description, og); - qpdf_offset_t offset = m->file->tell(); - bool empty = false; - - StringDecrypter decrypter{this, og}; - StringDecrypter* decrypter_ptr = m->encp->encrypted ? &decrypter : nullptr; - auto object = - QPDFParser(*m->file, m->last_object_description, m->tokenizer, decrypter_ptr, this, true) - .parse(empty, false); - if (empty) { - // Nothing in the PDF spec appears to allow empty objects, but they have been encountered in - // actual PDF files and Adobe Reader appears to ignore them. - warn(damagedPDF(*m->file, m->file->getLastOffset(), "empty object treated as null")); - return object; - } - auto token = readToken(*m->file); - if (object.isDictionary() && token.isWord("stream")) { - readStream(object, og, offset); - token = readToken(*m->file); - } - if (!token.isWord("endobj")) { - QTC::TC("qpdf", "QPDF err expected endobj"); - warn(damagedPDF("expected endobj")); - } - return object; -} - -// After reading stream dictionary and stream keyword, read rest of stream. -void -QPDF::readStream(QPDFObjectHandle& object, QPDFObjGen og, qpdf_offset_t offset) -{ - validateStreamLineEnd(object, og, offset); - - // Must get offset before accessing any additional objects since resolving a previously - // unresolved indirect object will change file position. - qpdf_offset_t stream_offset = m->file->tell(); - size_t length = 0; - - try { - auto length_obj = object.getKey("/Length"); - - if (!length_obj.isInteger()) { - if (length_obj.isNull()) { - QTC::TC("qpdf", "QPDF stream without length"); - throw damagedPDF(offset, "stream dictionary lacks /Length key"); - } - QTC::TC("qpdf", "QPDF stream length not integer"); - throw damagedPDF(offset, "/Length key in stream dictionary is not an integer"); - } - - length = toS(length_obj.getUIntValue()); - // Seek in two steps to avoid potential integer overflow - m->file->seek(stream_offset, SEEK_SET); - m->file->seek(toO(length), SEEK_CUR); - if (!readToken(*m->file).isWord("endstream")) { - QTC::TC("qpdf", "QPDF missing endstream"); - throw damagedPDF("expected endstream"); - } - } catch (QPDFExc& e) { - if (m->attempt_recovery) { - warn(e); - length = recoverStreamLength(m->file, og, stream_offset); - } else { - throw; - } - } - object = QPDFObjectHandle(qpdf::Stream(*this, og, object, stream_offset, length)); -} - -void -QPDF::validateStreamLineEnd(QPDFObjectHandle& object, QPDFObjGen og, qpdf_offset_t offset) -{ - // The PDF specification states that the word "stream" should be followed by either a carriage - // return and a newline or by a newline alone. It specifically disallowed following it by a - // carriage return alone since, in that case, there would be no way to tell whether the NL in a - // CR NL sequence was part of the stream data. However, some readers, including Adobe reader, - // accept a carriage return by itself when followed by a non-newline character, so that's what - // we do here. We have also seen files that have extraneous whitespace between the stream - // keyword and the newline. - while (true) { - char ch; - if (m->file->read(&ch, 1) == 0) { - // A premature EOF here will result in some other problem that will get reported at - // another time. - return; - } - if (ch == '\n') { - // ready to read stream data - QTC::TC("qpdf", "QPDF stream with NL only"); - return; - } - if (ch == '\r') { - // Read another character - if (m->file->read(&ch, 1) != 0) { - if (ch == '\n') { - // Ready to read stream data - QTC::TC("qpdf", "QPDF stream with CRNL"); - } else { - // Treat the \r by itself as the whitespace after endstream and start reading - // stream data in spite of not having seen a newline. - QTC::TC("qpdf", "QPDF stream with CR only"); - m->file->unreadCh(ch); - warn(damagedPDF( - m->file->tell(), "stream keyword followed by carriage return only")); - } - } - return; - } - if (!util::is_space(ch)) { - QTC::TC("qpdf", "QPDF stream without newline"); - m->file->unreadCh(ch); - warn(damagedPDF( - m->file->tell(), "stream keyword not followed by proper line terminator")); - return; - } - warn(damagedPDF(m->file->tell(), "stream keyword followed by extraneous whitespace")); - } -} - -QPDFObjectHandle -QPDF::readObjectInStream(std::shared_ptr& input, int obj) -{ - m->last_object_description.erase(7); // last_object_description starts with "object " - m->last_object_description += std::to_string(obj); - m->last_object_description += " 0"; - - bool empty = false; - auto object = QPDFParser(*input, m->last_object_description, m->tokenizer, nullptr, this, true) - .parse(empty, false); - if (empty) { - // Nothing in the PDF spec appears to allow empty objects, but they have been encountered in - // actual PDF files and Adobe Reader appears to ignore them. - warn(damagedPDF(*input, input->getLastOffset(), "empty object treated as null")); - } - return object; -} - -bool -QPDF::findEndstream() -{ - // Find endstream or endobj. Position the input at that token. - auto t = readToken(*m->file, 20); - if (t.isWord("endobj") || t.isWord("endstream")) { - m->file->seek(m->file->getLastOffset(), SEEK_SET); - return true; - } - return false; -} - -size_t -QPDF::recoverStreamLength( - std::shared_ptr input, QPDFObjGen og, qpdf_offset_t stream_offset) -{ - // Try to reconstruct stream length by looking for endstream or endobj - warn(damagedPDF(*input, stream_offset, "attempting to recover stream length")); - - PatternFinder ef(*this, &QPDF::findEndstream); - size_t length = 0; - if (m->file->findFirst("end", stream_offset, 0, ef)) { - length = toS(m->file->tell() - stream_offset); - // Reread endstream but, if it was endobj, don't skip that. - QPDFTokenizer::Token t = readToken(*m->file); - if (t.getValue() == "endobj") { - m->file->seek(m->file->getLastOffset(), SEEK_SET); - } - } - - if (length) { - auto end = stream_offset + toO(length); - qpdf_offset_t found_offset = 0; - QPDFObjGen found_og; - - // Make sure this is inside this object - for (auto const& [current_og, entry]: m->xref_table) { - if (entry.getType() == 1) { - qpdf_offset_t obj_offset = entry.getOffset(); - if (found_offset < obj_offset && obj_offset < end) { - found_offset = obj_offset; - found_og = current_og; - } - } - } - if (!found_offset || found_og == og) { - // If we are trying to recover an XRef stream the xref table will not contain and - // won't contain any entries, therefore we cannot check the found length. Otherwise we - // found endstream\nendobj within the space allowed for this object, so we're probably - // in good shape. - } else { - QTC::TC("qpdf", "QPDF found wrong endstream in recovery"); - length = 0; - } - } - - if (length == 0) { - warn(damagedPDF( - *input, stream_offset, "unable to recover stream data; treating stream as empty")); - } else { - warn(damagedPDF( - *input, stream_offset, "recovered stream length: " + std::to_string(length))); - } - - QTC::TC("qpdf", "QPDF recovered stream length"); - return length; -} - -QPDFTokenizer::Token -QPDF::readToken(InputSource& input, size_t max_len) -{ - return m->tokenizer.readToken(input, m->last_object_description, true, max_len); -} - -QPDFObjectHandle -QPDF::readObjectAtOffset( - bool try_recovery, - qpdf_offset_t offset, - std::string const& description, - QPDFObjGen exp_og, - QPDFObjGen& og, - bool skip_cache_if_in_xref) -{ - bool check_og = true; - if (exp_og.getObj() == 0) { - // This method uses an expect object ID of 0 to indicate that we don't know or don't care - // what the actual object ID is at this offset. This is true when we read the xref stream - // and linearization hint streams. In this case, we don't verify the expect object - // ID/generation against what was read from the file. There is also no reason to attempt - // xref recovery if we get a failure in this case since the read attempt was not triggered - // by an xref lookup. - check_og = false; - try_recovery = false; - } - setLastObjectDescription(description, exp_og); - - if (!m->attempt_recovery) { - try_recovery = false; - } - - // Special case: if offset is 0, just return null. Some PDF writers, in particular - // "Mac OS X 10.7.5 Quartz PDFContext", may store deleted objects in the xref table as - // "0000000000 00000 n", which is not correct, but it won't hurt anything for us to ignore - // these. - if (offset == 0) { - QTC::TC("qpdf", "QPDF bogus 0 offset", 0); - warn(damagedPDF(0, "object has offset 0")); - return QPDFObjectHandle::newNull(); - } - - m->file->seek(offset, SEEK_SET); - try { - QPDFTokenizer::Token tobjid = readToken(*m->file); - bool objidok = tobjid.isInteger(); - QTC::TC("qpdf", "QPDF check objid", objidok ? 1 : 0); - if (!objidok) { - QTC::TC("qpdf", "QPDF expected n n obj"); - throw damagedPDF(offset, "expected n n obj"); - } - QPDFTokenizer::Token tgen = readToken(*m->file); - bool genok = tgen.isInteger(); - QTC::TC("qpdf", "QPDF check generation", genok ? 1 : 0); - if (!genok) { - throw damagedPDF(offset, "expected n n obj"); - } - QPDFTokenizer::Token tobj = readToken(*m->file); - - bool objok = tobj.isWord("obj"); - QTC::TC("qpdf", "QPDF check obj", objok ? 1 : 0); - - if (!objok) { - throw damagedPDF(offset, "expected n n obj"); - } - int objid = QUtil::string_to_int(tobjid.getValue().c_str()); - int generation = QUtil::string_to_int(tgen.getValue().c_str()); - og = QPDFObjGen(objid, generation); - if (objid == 0) { - QTC::TC("qpdf", "QPDF object id 0"); - throw damagedPDF(offset, "object with ID 0"); - } - if (check_og && (exp_og != og)) { - QTC::TC("qpdf", "QPDF err wrong objid/generation"); - QPDFExc e = damagedPDF(offset, "expected " + exp_og.unparse(' ') + " obj"); - if (try_recovery) { - // Will be retried below - throw e; - } else { - // We can try reading the object anyway even if the ID doesn't match. - warn(e); - } - } - } catch (QPDFExc& e) { - if (try_recovery) { - // Try again after reconstructing xref table - reconstruct_xref(e); - if (m->xref_table.count(exp_og) && (m->xref_table[exp_og].getType() == 1)) { - qpdf_offset_t new_offset = m->xref_table[exp_og].getOffset(); - QPDFObjectHandle result = - readObjectAtOffset(false, new_offset, description, exp_og, og, false); - QTC::TC("qpdf", "QPDF recovered in readObjectAtOffset"); - return result; - } else { - QTC::TC("qpdf", "QPDF object gone after xref reconstruction"); - warn(damagedPDF( - "", - 0, - ("object " + exp_og.unparse(' ') + - " not found in file after regenerating cross reference " - "table"))); - return QPDFObjectHandle::newNull(); - } - } else { - throw; - } - } - - QPDFObjectHandle oh = readObject(description, og); - - if (isUnresolved(og)) { - // Store the object in the cache here so it gets cached whether we first know the offset or - // whether we first know the object ID and generation (in which we case we would get here - // through resolve). - - // Determine the end offset of this object before and after white space. We use these - // numbers to validate linearization hint tables. Offsets and lengths of objects may imply - // the end of an object to be anywhere between these values. - qpdf_offset_t end_before_space = m->file->tell(); - - // skip over spaces - while (true) { - char ch; - if (m->file->read(&ch, 1)) { - if (!isspace(static_cast(ch))) { - m->file->seek(-1, SEEK_CUR); - break; - } - } else { - throw damagedPDF(m->file->tell(), "EOF after endobj"); - } - } - qpdf_offset_t end_after_space = m->file->tell(); - if (skip_cache_if_in_xref && m->xref_table.count(og)) { - // Ordinarily, an object gets read here when resolved through xref table or stream. In - // the special case of the xref stream and linearization hint tables, the offset comes - // from another source. For the specific case of xref streams, the xref stream is read - // and loaded into the object cache very early in parsing. Ordinarily, when a file is - // updated by appending, items inserted into the xref table in later updates take - // precedence over earlier items. In the special case of reusing the object number - // previously used as the xref stream, we have the following order of events: - // - // * reused object gets loaded into the xref table - // * old object is read here while reading xref streams - // * original xref entry is ignored (since already in xref table) - // - // It is the second step that causes a problem. Even though the xref table is correct in - // this case, the old object is already in the cache and so effectively prevails over - // the reused object. To work around this issue, we have a special case for the xref - // stream (via the skip_cache_if_in_xref): if the object is already in the xref stream, - // don't cache what we read here. - // - // It is likely that the same bug may exist for linearization hint tables, but the - // existing code uses end_before_space and end_after_space from the cache, so fixing - // that would require more significant rework. The chances of a linearization hint - // stream being reused seems smaller because the xref stream is probably the highest - // object in the file and the linearization hint stream would be some random place in - // the middle, so I'm leaving that bug unfixed for now. If the bug were to be fixed, we - // could use !check_og in place of skip_cache_if_in_xref. - QTC::TC("qpdf", "QPDF skipping cache for known unchecked object"); - } else { - updateCache(og, oh.getObj(), end_before_space, end_after_space); - } - } - - return oh; -} - -std::shared_ptr const& -QPDF::resolve(QPDFObjGen og) -{ - if (!isUnresolved(og)) { - return m->obj_cache[og].object; - } - - if (m->resolving.count(og)) { - // This can happen if an object references itself directly or indirectly in some key that - // has to be resolved during object parsing, such as stream length. - QTC::TC("qpdf", "QPDF recursion loop in resolve"); - warn(damagedPDF("", "loop detected resolving object " + og.unparse(' '))); - updateCache(og, QPDFObject::create(), -1, -1); - return m->obj_cache[og].object; - } - ResolveRecorder rr(this, og); - - if (m->xref_table.count(og) != 0) { - QPDFXRefEntry const& entry = m->xref_table[og]; - try { - switch (entry.getType()) { - case 1: - { - qpdf_offset_t offset = entry.getOffset(); - // Object stored in cache by readObjectAtOffset - QPDFObjGen a_og; - QPDFObjectHandle oh = readObjectAtOffset(true, offset, "", og, a_og, false); - } - break; - - case 2: - resolveObjectsInStream(entry.getObjStreamNumber()); - break; - - default: - throw damagedPDF( - "", 0, ("object " + og.unparse('/') + " has unexpected xref entry type")); - } - } catch (QPDFExc& e) { - warn(e); - } catch (std::exception& e) { - warn(damagedPDF( - "", 0, ("object " + og.unparse('/') + ": error reading object: " + e.what()))); - } - } - - if (isUnresolved(og)) { - // PDF spec says unknown objects resolve to the null object. - QTC::TC("qpdf", "QPDF resolve failure to null"); - updateCache(og, QPDFObject::create(), -1, -1); - } - - auto& result(m->obj_cache[og].object); - result->setDefaultDescription(this, og); - return result; -} - -void -QPDF::resolveObjectsInStream(int obj_stream_number) -{ - if (m->resolved_object_streams.count(obj_stream_number)) { - return; - } - m->resolved_object_streams.insert(obj_stream_number); - // Force resolution of object stream - QPDFObjectHandle obj_stream = getObjectByID(obj_stream_number, 0); - if (!obj_stream.isStream()) { - throw damagedPDF( - "supposed object stream " + std::to_string(obj_stream_number) + " is not a stream"); - } - - // For linearization data in the object, use the data from the object stream for the objects in - // the stream. - QPDFObjGen stream_og(obj_stream_number, 0); - qpdf_offset_t end_before_space = m->obj_cache[stream_og].end_before_space; - qpdf_offset_t end_after_space = m->obj_cache[stream_og].end_after_space; - - QPDFObjectHandle dict = obj_stream.getDict(); - if (!dict.isDictionaryOfType("/ObjStm")) { - QTC::TC("qpdf", "QPDF ERR object stream with wrong type"); - warn(damagedPDF( - "supposed object stream " + std::to_string(obj_stream_number) + " has wrong type")); - } - - if (!(dict.getKey("/N").isInteger() && dict.getKey("/First").isInteger())) { - throw damagedPDF( - ("object stream " + std::to_string(obj_stream_number) + " has incorrect keys")); - } - - int n = dict.getKey("/N").getIntValueAsInt(); - int first = dict.getKey("/First").getIntValueAsInt(); - - std::map offsets; - - std::shared_ptr bp = obj_stream.getStreamData(qpdf_dl_specialized); - auto input = std::shared_ptr( - // line-break - new BufferInputSource( - (m->file->getName() + " object stream " + std::to_string(obj_stream_number)), - bp.get())); - - long long last_offset = -1; - for (int i = 0; i < n; ++i) { - QPDFTokenizer::Token tnum = readToken(*input); - QPDFTokenizer::Token toffset = readToken(*input); - if (!(tnum.isInteger() && toffset.isInteger())) { - throw damagedPDF( - *input, - m->last_object_description, - input->getLastOffset(), - "expected integer in object stream header"); - } - - int num = QUtil::string_to_int(tnum.getValue().c_str()); - long long offset = QUtil::string_to_int(toffset.getValue().c_str()); - - if (num == obj_stream_number) { - QTC::TC("qpdf", "QPDF ignore self-referential object stream"); - warn(damagedPDF( - *input, - m->last_object_description, - input->getLastOffset(), - "object stream claims to contain itself")); - continue; - } - - if (num < 1) { - QTC::TC("qpdf", "QPDF object stream contains id < 1"); - warn(damagedPDF( - *input, - "object "s + std::to_string(num) + " 0, offset " + std::to_string(offset), - 0, - "object id is invalid"s)); - continue; - } - - if (offset <= last_offset) { - QTC::TC("qpdf", "QPDF object stream offsets not increasing"); - warn(damagedPDF( - *input, - "object "s + std::to_string(num) + " 0, offset " + std::to_string(offset), - 0, - "offset is invalid (must be larger than previous offset " + - std::to_string(last_offset) + ")")); - continue; - } - last_offset = offset; - - if (num > m->xref_table_max_id) { - continue; - } - - offsets[num] = toI(offset + first); - } - - // To avoid having to read the object stream multiple times, store all objects that would be - // found here in the cache. Remember that some objects stored here might have been overridden - // by new objects appended to the file, so it is necessary to recheck the xref table and only - // cache what would actually be resolved here. - m->last_object_description.clear(); - m->last_object_description += "object "; - for (auto const& iter: offsets) { - QPDFObjGen og(iter.first, 0); - auto entry = m->xref_table.find(og); - if (entry != m->xref_table.end() && entry->second.getType() == 2 && - entry->second.getObjStreamNumber() == obj_stream_number) { - int offset = iter.second; - input->seek(offset, SEEK_SET); - QPDFObjectHandle oh = readObjectInStream(input, iter.first); - updateCache(og, oh.getObj(), end_before_space, end_after_space); - } else { - QTC::TC("qpdf", "QPDF not caching overridden objstm object"); - } - } -} - -QPDFObjectHandle -QPDF::newIndirect(QPDFObjGen og, std::shared_ptr const& obj) -{ - obj->setDefaultDescription(this, og); - return {obj}; -} - -void -QPDF::updateCache( - QPDFObjGen og, - std::shared_ptr const& object, - qpdf_offset_t end_before_space, - qpdf_offset_t end_after_space, - bool destroy) -{ - object->setObjGen(this, og); - if (isCached(og)) { - auto& cache = m->obj_cache[og]; - object->move_to(cache.object, destroy); - cache.end_before_space = end_before_space; - cache.end_after_space = end_after_space; - } else { - m->obj_cache[og] = ObjCache(object, end_before_space, end_after_space); - } -} - -bool -QPDF::isCached(QPDFObjGen og) -{ - return m->obj_cache.count(og) != 0; -} - -bool -QPDF::isUnresolved(QPDFObjGen og) -{ - return !isCached(og) || m->obj_cache[og].object->isUnresolved(); -} - -QPDFObjGen -QPDF::nextObjGen() -{ - int max_objid = toI(getObjectCount()); - if (max_objid == std::numeric_limits::max()) { - throw std::range_error("max object id is too high to create new objects"); - } - return QPDFObjGen(max_objid + 1, 0); -} - -QPDFObjectHandle -QPDF::makeIndirectFromQPDFObject(std::shared_ptr const& obj) -{ - QPDFObjGen next{nextObjGen()}; - m->obj_cache[next] = ObjCache(obj, -1, -1); - return newIndirect(next, m->obj_cache[next].object); -} - -QPDFObjectHandle -QPDF::makeIndirectObject(QPDFObjectHandle oh) -{ - if (!oh) { - throw std::logic_error("attempted to make an uninitialized QPDFObjectHandle indirect"); - } - return makeIndirectFromQPDFObject(oh.getObj()); -} - -std::shared_ptr -QPDF::getObjectForParser(int id, int gen, bool parse_pdf) -{ - // This method is called by the parser and therefore must not resolve any objects. - auto og = QPDFObjGen(id, gen); - if (auto iter = m->obj_cache.find(og); iter != m->obj_cache.end()) { - return iter->second.object; - } - if (m->xref_table.count(og) || !m->parsed) { - return m->obj_cache.insert({og, QPDFObject::create(this, og)}) - .first->second.object; - } - if (parse_pdf) { - return QPDFObject::create(); - } - return m->obj_cache.insert({og, QPDFObject::create(this, og)}).first->second.object; -} - -std::shared_ptr -QPDF::getObjectForJSON(int id, int gen) -{ - auto og = QPDFObjGen(id, gen); - auto [it, inserted] = m->obj_cache.try_emplace(og); - auto& obj = it->second.object; - if (inserted) { - obj = (m->parsed && !m->xref_table.count(og)) - ? QPDFObject::create(this, og) - : QPDFObject::create(this, og); - } - return obj; -} - -QPDFObjectHandle -QPDF::getObject(QPDFObjGen og) -{ - if (auto it = m->obj_cache.find(og); it != m->obj_cache.end()) { - return {it->second.object}; - } else if (m->parsed && !m->xref_table.count(og)) { - return QPDFObject::create(); - } else { - auto result = - m->obj_cache.try_emplace(og, QPDFObject::create(this, og), -1, -1); - return {result.first->second.object}; - } -} - -void -QPDF::replaceObject(int objid, int generation, QPDFObjectHandle oh) -{ - replaceObject(QPDFObjGen(objid, generation), oh); -} - -void -QPDF::replaceObject(QPDFObjGen og, QPDFObjectHandle oh) -{ - if (!oh || (oh.isIndirect() && !(oh.isStream() && oh.getObjGen() == og))) { - QTC::TC("qpdf", "QPDF replaceObject called with indirect object"); - throw std::logic_error("QPDF::replaceObject called with indirect object handle"); - } - updateCache(og, oh.getObj(), -1, -1, false); -} - -void -QPDF::removeObject(QPDFObjGen og) -{ - m->xref_table.erase(og); - if (auto cached = m->obj_cache.find(og); cached != m->obj_cache.end()) { - // Take care of any object handles that may be floating around. - cached->second.object->assign_null(); - cached->second.object->setObjGen(nullptr, QPDFObjGen()); - m->obj_cache.erase(cached); - } -} - -void -QPDF::replaceReserved(QPDFObjectHandle reserved, QPDFObjectHandle replacement) -{ - QTC::TC("qpdf", "QPDF replaceReserved"); - auto tc = reserved.getTypeCode(); - if (!(tc == ::ot_reserved || tc == ::ot_null)) { - throw std::logic_error("replaceReserved called with non-reserved object"); - } - replaceObject(reserved.getObjGen(), replacement); -} - -void -QPDF::swapObjects(int objid1, int generation1, int objid2, int generation2) -{ - swapObjects(QPDFObjGen(objid1, generation1), QPDFObjGen(objid2, generation2)); -} - -void -QPDF::swapObjects(QPDFObjGen og1, QPDFObjGen og2) -{ - // Force objects to be read from the input source if needed, then swap them in the cache. - resolve(og1); - resolve(og2); - m->obj_cache[og1].object->swapWith(m->obj_cache[og2].object); -} - -size_t -QPDF::tableSize() -{ - // If obj_cache is dense, accommodate all object in tables,else accommodate only original - // objects. - auto max_xref = m->xref_table.size() ? m->xref_table.crbegin()->first.getObj() : 0; - auto max_obj = m->obj_cache.size() ? m->obj_cache.crbegin()->first.getObj() : 0; - auto max_id = std::numeric_limits::max() - 1; - if (max_obj >= max_id || max_xref >= max_id) { - // Temporary fix. Long-term solution is - // - QPDFObjGen to enforce objgens are valid and sensible - // - xref table and obj cache to protect against insertion of impossibly large obj ids - stopOnError("Impossibly large object id encountered."); - } - if (max_obj < 1.1 * std::max(toI(m->obj_cache.size()), max_xref)) { - return toS(++max_obj); - } - return toS(++max_xref); -} - -std::vector -QPDF::getCompressibleObjVector() -{ - return getCompressibleObjGens(); -} - -std::vector -QPDF::getCompressibleObjSet() -{ - return getCompressibleObjGens(); -} - -template -std::vector -QPDF::getCompressibleObjGens() -{ - // Return a list of objects that are allowed to be in object streams. Walk through the objects - // by traversing the document from the root, including a traversal of the pages tree. This - // makes that objects that are on the same page are more likely to be in the same object stream, - // which is slightly more efficient, particularly with linearized files. This is better than - // iterating through the xref table since it avoids preserving orphaned items. - - // Exclude encryption dictionary, if any - QPDFObjectHandle encryption_dict = m->trailer.getKey("/Encrypt"); - QPDFObjGen encryption_dict_og = encryption_dict.getObjGen(); - - const size_t max_obj = getObjectCount(); - std::vector visited(max_obj, false); - std::vector queue; - queue.reserve(512); - queue.push_back(m->trailer); - std::vector result; - if constexpr (std::is_same_v) { - result.reserve(m->obj_cache.size()); - } else if constexpr (std::is_same_v) { - result.resize(max_obj + 1U, false); - } else { - throw std::logic_error("Unsupported type in QPDF::getCompressibleObjGens"); - } - while (!queue.empty()) { - auto obj = queue.back(); - queue.pop_back(); - if (obj.getObjectID() > 0) { - QPDFObjGen og = obj.getObjGen(); - const size_t id = toS(og.getObj() - 1); - if (id >= max_obj) { - throw std::logic_error( - "unexpected object id encountered in getCompressibleObjGens"); - } - if (visited[id]) { - QTC::TC("qpdf", "QPDF loop detected traversing objects"); - continue; - } - - // Check whether this is the current object. If not, remove it (which changes it into a - // direct null and therefore stops us from revisiting it) and move on to the next object - // in the queue. - auto upper = m->obj_cache.upper_bound(og); - if (upper != m->obj_cache.end() && upper->first.getObj() == og.getObj()) { - removeObject(og); - continue; - } - - visited[id] = true; - - if (og == encryption_dict_og) { - QTC::TC("qpdf", "QPDF exclude encryption dictionary"); - } else if (!(obj.isStream() || - (obj.isDictionaryOfType("/Sig") && obj.hasKey("/ByteRange") && - obj.hasKey("/Contents")))) { - if constexpr (std::is_same_v) { - result.push_back(og); - } else if constexpr (std::is_same_v) { - result[id + 1U] = true; - } - } - } - if (obj.isStream()) { - auto dict = obj.getDict().as_dictionary(); - auto end = dict.crend(); - for (auto iter = dict.crbegin(); iter != end; ++iter) { - std::string const& key = iter->first; - QPDFObjectHandle const& value = iter->second; - if (!value.null()) { - if (key == "/Length") { - // omit stream lengths - if (value.isIndirect()) { - QTC::TC("qpdf", "QPDF exclude indirect length"); - } - } else { - queue.emplace_back(value); - } - } - } - } else if (obj.isDictionary()) { - auto dict = obj.as_dictionary(); - auto end = dict.crend(); - for (auto iter = dict.crbegin(); iter != end; ++iter) { - if (!iter->second.null()) { - queue.emplace_back(iter->second); - } - } - } else if (auto items = obj.as_array()) { - queue.insert(queue.end(), items.crbegin(), items.crend()); - } - } - - return result; -} diff --git a/manual/release-notes.rst b/manual/release-notes.rst index 0092e21..cabc9c3 100644 --- a/manual/release-notes.rst +++ b/manual/release-notes.rst @@ -21,15 +21,16 @@ more detail. integer object. Previously the method returned false if the first dictionary object was not a linearization parameter dictionary. - - Other enhancements +.. _r12-0-0: + +12.0.1: not yet released + - Other enhancements - - There have been further enhancements to how files with damaged xref - tables are recovered. + - There have been further enhancements to how files with damaged xref + tables are recovered. .. cSpell:ignore substract -.. _r12-0-0: - 12.0.0: March 9, 2025 - API breaking changes -- libgit2 0.21.4