GCF.cpp

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#include <vpkpp/format/GCF.h>
 
#include <algorithm>
#include <filesystem>
 
#include <cryptopp/aes.h>
#include <cryptopp/modes.h>
#include <cryptopp/filters.h>
#include <FileStream.h>
#include <miniz.h>
#include <sourcepp/crypto/Adler32.h>
#include <sourcepp/crypto/CRC32.h>
 
using namespace sourcepp;
using namespace vpkpp;
 
std::unique_ptr<PackFile> GCF::open(const std::string& path, const EntryCallback& callback, const OpenPropertyRequest& requestProperty) {
    // TODO: Add v5 and perhaps v4 support
 
    if (!std::filesystem::exists(path)) {
        // File does not exist
        return nullptr;
    }
 
    auto* gcf = new GCF{path};
    auto packFile = std::unique_ptr<PackFile>(gcf);
 
    FileStream reader(gcf->fullFilePath);
    reader.seek_in(0);
 
    // read the main header here (not the block header)
    reader.read(gcf->header);
    if (gcf->header.dummy1 != 1 && gcf->header.dummy2 != 1 && gcf->header.gcfversion != 6) {
        return nullptr;
    }
 
    if (gcf->header.filesize != std::filesystem::file_size(gcf->fullFilePath)) {
        // again, this should never occur with a valid gcf file
        return nullptr;
    }
 
    reader.read(gcf->blockheader);
    if (gcf->blockheader.count != gcf->header.blockcount) {
        return nullptr;
    }
 
    // if you're having a headache reading the if statement below heres a quick explaination of what it actually does
    // it just adds all blockheader entries together and compares it against the checksum
    // if it's not the same then we bail out with a nullptr
    if (gcf->blockheader.count +
        gcf->blockheader.used +
        gcf->blockheader.dummy1 +
        gcf->blockheader.dummy2 +
        gcf->blockheader.dummy3 +
        gcf->blockheader.dummy4 +
        gcf->blockheader.dummy5 != gcf->blockheader.checksum) {
        return nullptr;
    }
 
    // block headers!!!!!!
    bool requestKey = false;
    for (int i = 0; i < gcf->header.blockcount; i++) {
        Block& block = gcf->blockdata.emplace_back();
        reader.read(block);
        if (block.isEncrypted()) {
            requestKey = true;
        }
    }
    if (requestKey) {
        const auto key = requestProperty(gcf, OpenProperty::DECRYPTION_KEY);
        if (key.size() != gcf->decryption_key.size()) {
            return nullptr;
        }
        std::ranges::copy(key, gcf->decryption_key.begin());
    }
 
    // Fragmentation Map header
    // not worth keeping around after verifying stuff so no struct def
    // if you want one this is how one should look like
    // actually if we want to implement writing later this might be a better idea
    // if anyone wants to touch this piece of shit format again anyways
 
    auto blkcount = reader.read<uint32_t>();
    auto d1 = reader.read<uint32_t>();
    auto d2 = reader.read<uint32_t>();
    auto checksum = reader.read<uint32_t>();
 
    if (blkcount + d1 + d2 != checksum || blkcount != gcf->blockheader.count) {
        return nullptr;
    }
 
    // Fragmentation Map (list of dwords)
 
    for (int i = 0; i < blkcount; i++) {
        gcf->fragmap.push_back(reader.read<uint32_t>());
    }
 
    // Directory stuff starts here
 
    //Reading the header
    uint64_t temp = reader.tell_in();
    reader.read(gcf->dirheader);
 
    uint64_t diroffset = reader.tell_in() + (gcf->dirheader.itemcount * 28);
 
    std::vector<DirectoryEntry2> direntries{};
 
    for (int i = 0; i < gcf->dirheader.itemcount; i++) {
        DirectoryEntry2& entry = direntries.emplace_back();
        reader.read(entry.entry_real);
        auto currentoffset = reader.tell_in();
        reader.seek_in_u(diroffset + entry.entry_real.nameoffset);
        reader.read(entry.filename);
        if (entry.entry_real.dirtype != 0) { // if not directory
            std::string dirname;
            DirectoryEntry2 current_filename_entry = entry;
            while (current_filename_entry.entry_real.parentindex != 0xffffffff) {
                current_filename_entry = direntries[current_filename_entry.entry_real.parentindex];
                dirname.insert(0, "/");
                dirname.insert(0, current_filename_entry.filename);
            }
 
            auto gcfEntryPath = gcf->cleanEntryPath(dirname);
            if (!gcfEntryPath.empty()) {
                gcfEntryPath += '/';
            }
            gcfEntryPath += entry.filename;
 
            Entry gcfEntry = createNewEntry();
            gcfEntry.length = entry.entry_real.itemsize;
            gcfEntry.crc32 = entry.entry_real.fileid; // INDEX INTO THE CHECKSUM MAP VECTOR NOT CRC32!!!
            gcfEntry.offset = i; // THIS IS THE STRUCT INDEX NOT SOME OFFSET!!!
            //printf("%s\n", gcfEntry.path.c_str());
            gcf->entries.emplace(gcfEntryPath, gcfEntry);
 
            if (callback) {
                callback(gcfEntryPath, gcfEntry);
            }
        }
        reader.seek_in_u(currentoffset);
    }
 
    // Directory Map
 
    // Directory Map header
    reader.seek_in_u(temp + gcf->dirheader.dirsize);
 
    //auto dmap = reader.read<DirectoryMapHeader>();
    reader.skip_in<DirectoryMapHeader>();
 
    // Directory Map entries
    for (int i = 0; i < gcf->dirheader.itemcount; i++) {
        DirectoryMapEntry& entry = gcf->dirmap_entries.emplace_back();
        reader.read(entry);
    }
 
    // Checksum header
    //auto dummy0 = reader.read<uint32_t>();
    reader.skip_in<uint32_t>();
    auto checksumsize = reader.read<uint32_t>();
    std::size_t checksums_start = reader.tell_in();
 
    //printf("checksums start: %llu\n", checksums_start);
    //printf("%lu %lu %lu %lu\n", gcf->header.blockcount, gcf->blockheader.used, gcf->header.appid, gcf->header.appversion);
    // map header
 
    auto chksummapheader = reader.read<ChecksumMapHeader>();
    if (chksummapheader.dummy1 != 0x14893721 || chksummapheader.dummy2 != 0x1) {
        return nullptr;
    }
 
    //printf("%lu %lu\n", chksummapheader.checksum_count, chksummapheader.item_count);
 
    for (int i = 0; i < chksummapheader.item_count; i++) {
        auto& cur_entry = gcf->chksum_map.emplace_back();
        reader.read(cur_entry);
    }
 
    for (int i = 0; i < chksummapheader.checksum_count; i++) {
        auto& currentChecksum = gcf->checksums.emplace_back();
        reader.read(currentChecksum);
    }
    //printf("current pos: %llu, block header: %llu should be: %llu", reader.tellInput(), reader.tellInput() + 0x80, checksums_start + checksumsize);
    // TODO: check the checksum RSA signature... later.. if ever...
 
    reader.seek_in_u(checksums_start + checksumsize);
 
    reader.read(gcf->datablockheader);
    return packFile;
}
 
std::vector<std::string> GCF::verifyEntryChecksums() const {
    std::vector<std::string> bad;
    this->runForAllEntries([this, &bad](const std::string& path, const Entry& entry) {
        auto bytes = this->readEntry(path);
        if (!bytes || bytes->empty()) {
            return;
        }
        std::size_t tocheck = bytes->size();
        uint32_t idx = entry.crc32;
        uint32_t count = this->chksum_map[idx].count;
        uint32_t checksumstart = this->chksum_map[idx].firstindex;
        for (int i = 0; i < count; i++) {
            uint32_t csum = this->checksums[checksumstart + i];
            std::size_t toread = std::min(static_cast<std::size_t>(0x8000), tocheck);
            const auto* data = bytes->data() + (i * 0x8000);
            uint32_t checksum = crypto::computeCRC32({data, toread}) ^ crypto::computeAdler32({data, toread});
            if (checksum != csum) {
                bad.push_back(path);
            }
            tocheck -= toread;
        }
    });
    return bad;
}
 
std::optional<std::vector<std::byte>> GCF::readEntry(const std::string& path_) const {
    auto path = this->cleanEntryPath(path_);
    auto entry = this->findEntry(path);
    if (!entry) {
        return std::nullopt;
    }
    if (entry->unbaked) {
        return readUnbakedEntry(*entry);
    }
 
    std::vector<std::byte> filedata;
    if (entry->length == 0) {
        // don't bother
        return filedata;
    }
 
    uint32_t dir_index = entry->offset;
    //printf(" extracting file: %s\n", entry.path.c_str());
 
    std::vector<Block> toread;
    for (const auto& v : this->blockdata) {
        if (v.dir_index == dir_index && (v.flags & 0x8000)) { // need to check for 0x8000 here because valve dumps uninitialized memory 
            toread.push_back(v);
        }
    }
 
    if (toread.empty()) {
        //printf("could not find any directory index for %lu", entry.vpk_offset);
        return std::nullopt;
    }
    std::sort(toread.begin(), toread.end(), [](const Block& lhs, const Block& rhs) {
        return lhs.file_data_offset < rhs.file_data_offset;
    });
 
    FileStream stream{this->fullFilePath};
    if (!stream) {
        return std::nullopt;
    }
 
    uint64_t remaining = entry->length;
    bool needs_decrypt = false;
    auto filemode = Block::CompressionType::UNCOMPRESSED;
    for (auto& block : toread) {
        uint32_t currindex = block.first_data_block_index;
        while (currindex <= this->blockheader.count) {
            uint64_t curfilepos = static_cast<uint64_t>(this->datablockheader.firstblockoffset) + (static_cast<std::uint64_t>(0x2000) * static_cast<std::uint64_t>(currindex));
            stream.seek_in_u(curfilepos);
            //printf("off %lli block %lu toread %lli should be %llu\n", stream.tellInput(), currindex, remaining, curfilepos);
            uint32_t toreadAmt = std::min(remaining, static_cast<uint64_t>(0x2000));
            auto streamvec = stream.read_bytes(toreadAmt);
            filedata.insert(filedata.end(), streamvec.begin(), streamvec.end());
            remaining -= toreadAmt;
            currindex = this->fragmap[currindex];
            //printf("curridx now: %lu\n", currindex);
        }
        needs_decrypt = block.isEncrypted();
        filemode = block.getCompressionType();
    }
    if (needs_decrypt) {
        CryptoPP::byte iv[16] = {};
        switch (filemode) {
            using enum Block::CompressionType;
            case UNCOMPRESSED:
            case COMPRESSED:
                break;
            case ENCRYPTED: {
                auto real_size = filedata.size();
                if (filedata.size() % 10 != 0) {
                    filedata.resize(filedata.size() + (0x10 - (filedata.size() % 10)), {});
                }
                auto remaining_encrypted = filedata.size();
                auto offset = 0;
                while (remaining_encrypted) {
                    CryptoPP::CFB_Mode<CryptoPP::AES>::Decryption d;
                    d.SetKeyWithIV(reinterpret_cast<const CryptoPP::byte*>(this->decryption_key.data()), 16, iv);
                    auto current_batch = std::min(remaining_encrypted, static_cast<size_t>(0x8000));
                    d.ProcessData(reinterpret_cast<CryptoPP::byte*>(filedata.data() + offset), reinterpret_cast<CryptoPP::byte*>(filedata.data() + offset), current_batch);
                    remaining_encrypted -= current_batch;
                    offset += static_cast<int>(current_batch);
                }
                filedata.resize(real_size);
                break;
            }
            case COMPRESSED_AND_ENCRYPTED: {
                std::vector<std::byte> processed_data;
                BufferStream s(filedata.data(), filedata.size());
                while (s.size() != s.tell()) {
                    static constexpr auto allocate_block = [](std::vector<std::byte>& vec, size_t x) {
                        const size_t old = vec.size();
                        vec.resize(old + x);
                        return vec.data() + old;
                    };
 
                    auto encrypted_size = s.read<uint32_t>();
                    mz_ulong decompressed_size = s.read<uint32_t>();
 
                    auto buffer = s.read_bytes(encrypted_size);
                    auto real_size = buffer.size();
                    if (buffer.size() % 10 != 0) {
                        buffer.resize(buffer.size() + (0x10 - (buffer.size() % 10)), {});
                    }
                    CryptoPP::CFB_Mode<CryptoPP::AES>::Decryption d;
                    d.SetKeyWithIV(reinterpret_cast<const CryptoPP::byte*>(this->decryption_key.data()), 16, iv);
                    d.ProcessData(reinterpret_cast<CryptoPP::byte*>(buffer.data()), reinterpret_cast<CryptoPP::byte*>(buffer.data()), buffer.size());
                    buffer.resize(real_size);
 
                    auto start = allocate_block(processed_data, decompressed_size);
                    if (mz_uncompress(reinterpret_cast<uint8_t*>(start), &decompressed_size, reinterpret_cast<uint8_t*>(buffer.data()), buffer.size()) != MZ_OK) {
                        return std::nullopt;
                    }
 
                    //auto remaining = s.size() - s.tell();
                    if (entry->length == processed_data.size()) {
                        break;
                    }
                    s.seek_u(s.tell() + (0x8000 - s.tell() % 0x8000));
                }
                filedata = processed_data;
                break;
            }
        }
    }
    return filedata;
}
 
Attribute GCF::getSupportedEntryAttributes() const {
    using enum Attribute;
    return LENGTH;
}
 
GCF::operator std::string() const {
    return PackFileReadOnly::operator std::string() +
        " | Version v" + std::to_string(this->header.gcfversion) +
        " | AppID " + std::to_string(this->header.appid) +
        " | App Version v" + std::to_string(this->header.appversion);
}
 
uint32_t GCF::getVersion() const {
    return this->header.gcfversion;
}
 
uint32_t GCF::getAppID() const {
    return this->header.appid;
}
 
uint32_t GCF::getAppVersion() const {
    return this->header.appversion;
}