Function TryDecompressZip

src/platform/linux/http_server.cpp:108–150

Decompress Steam's cloud-compression ZIP. Returns false (and leaves out untouched) on non-ZIP or failure.

// Decompress Steam's cloud-compression ZIP. Returns false (and leaves out untouched) on non-ZIP or failure.
static bool TryDecompressZip(const std::vector<uint8_t>& data, std::vector<uint8_t>& out) {
    if (data.size() < 4) return false;
    if (data[0] != 0x50 || data[1] != 0x4B || data[2] != 0x03 || data[3] != 0x04)
        return false;

    mz_zip_archive zip{};
    if (!mz_zip_reader_init_mem(&zip, data.data(), data.size(), 0)) {
        LOG("[HttpServer] ZIP init failed: %s", mz_zip_get_error_string(mz_zip_get_last_error(&zip)));
        return false;
    }

    // Steam cloud ZIP is single-entry, inner name "z"; anything else is a game save that's natively ZIP.
    if (mz_zip_reader_get_num_files(&zip) != 1) {
        mz_zip_reader_end(&zip);
        return false;
    }
    mz_zip_archive_file_stat fstat;
    if (!mz_zip_reader_file_stat(&zip, 0, &fstat) ||
        strcmp(fstat.m_filename, "z") != 0) {
        mz_zip_reader_end(&zip);
        return false;
    }

    // Reject if uncompressed size exceeds 512 MB or would overflow size_t
    if (fstat.m_uncomp_size > 512ULL * 1024 * 1024 || fstat.m_uncomp_size > SIZE_MAX) {
        LOG("[HttpServer] ZIP rejected: declared size %llu", (unsigned long long)fstat.m_uncomp_size);
        mz_zip_reader_end(&zip);
        return false;
    }

    size_t uncompSize = 0;
    void* p = mz_zip_reader_extract_to_heap(&zip, 0, &uncompSize, 0);
    mz_zip_reader_end(&zip);

    if (!p) {
        LOG("[HttpServer] ZIP extract failed");
        return false;
    }

    out.assign(static_cast<uint8_t*>(p), static_cast<uint8_t*>(p) + uncompSize);
    mz_free(p);
    return true;
}

// Verify the connecting client is our own process via /proc/net/tcp inode lookup.
static bool IsConnectionFromSteam(int clientFd) {