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fix(filesystem_parser): more robust section index discovery (gh #264)

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Marcus Holland-Moritz 2025-05-18 11:37:19 +02:00 committed by mhx
parent 532e86934e
commit 661b951cfd
1 changed files with 46 additions and 10 deletions
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46
src/reader/internal/filesystem_parser.cpp
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@ -250,18 +250,54 @@ void filesystem_parser::find_index() {
mm_->as<void>(image_offset_ + image_size_ - sizeof(uint64_t)),
sizeof(uint64_t));
if ((index_pos >> 48) == static_cast<uint16_t>(section_type::SECTION_INDEX)) {
if ((index_pos >> 48) != static_cast<uint16_t>(section_type::SECTION_INDEX)) {
return;
}
index_pos &= section_offset_mask;
index_pos += image_offset_;
if (std::cmp_less(index_pos, image_offset_ + image_size_)) {
if (std::cmp_greater_equal(index_pos, image_offset_ + image_size_)) {
return;
}
auto section = fs_section(*mm_, index_pos, version_);
if (section.check_fast(*mm_)) {
index_.resize(section.length() / sizeof(uint64_t));
::memcpy(index_.data(), section.data(*mm_).data(), section.length());
if (!section.check_fast(*mm_)) {
return;
}
if (section.type() != section_type::SECTION_INDEX) {
return;
}
if (section.length() % sizeof(uint64_t) != 0) {
return;
}
auto const section_count = section.length() / sizeof(uint64_t);
// at least METADATA_V2_SCHEMA, METADATA_V2, and SECTION_INDEX
if (section_count < 3) {
return;
}
// the section index must be the last section
if (std::cmp_not_equal(section.end(), image_offset_ + image_size_)) {
return;
}
auto const index = section.data(*mm_);
index_.resize(section_count);
::memcpy(index_.data(), index.data(), index.size());
// index entries must be sorted by offset
if (!std::ranges::is_sorted(index_, [](auto const a, auto const b) {
return (a & section_offset_mask) < (b & section_offset_mask);
})) {
// remove the index again if it is not sorted
index_.clear();
}
}