Function getAppImageDigestMd5

src/shared/shared.cpp:948–1009

}

QString getAppImageDigestMd5(const QString& path) {
    // try to read embedded MD5 digest
    unsigned long offset = 0, length = 0;

    // first of all, digest calculation is supported only for type 2
    if (appimage_get_type(path.toStdString().c_str(), false) != 2)
        return "";

    auto rv = appimage_get_elf_section_offset_and_length(path.toStdString().c_str(), ".digest_md5", &offset, &length);

    QByteArray buffer(16, '\0');

    if (rv && offset != 0 && length != 0) {
        // open file and read digest from ELF header section
        QFile file(path);

        if (!file.open(QFile::ReadOnly))
            return "";

        if (!file.seek(static_cast<qint64>(offset)))
            return "";

        if (!file.read(buffer.data(), buffer.size()))
            return "";

        file.close();
    }

    bool needToCalculateDigest;

    // there seem to be some AppImages out there who actually have the required section embedded, but it's empty
    // therefore we make the assumption that a hash value of zeroes is probably incorrect and recalculate
    // in the extremely rare case in which the AppImage's digest would *really* be that value, we'd waste a bit of
    // computation time, but the chances are so low... who cares, right?
    {
        auto nonZeroCharacterFound = false;

        for (const char i : buffer) {
            if (i != '\0') {
                nonZeroCharacterFound = true;
                break;
            }
        }

        needToCalculateDigest = !nonZeroCharacterFound;
    }

    if (needToCalculateDigest) {
        // calculate digest
        if (!appimage_type2_digest_md5(path.toStdString().c_str(), buffer.data()))
            return "";
    }

    // create hexadecimal representation
    auto hexDigest = appimage_hexlify(buffer, static_cast<size_t>(buffer.size()));

    QString hexDigestStr(hexDigest);