Function authenticate

src/DataStreams/MongoDBBlockInputStream.cpp:43–137

See https://pocoproject.org/forum/viewtopic.php?f=10&t=6326&p=11426&hilit=mongodb+auth#p11485

#if POCO_VERSION < 0x01070800
/// See https://pocoproject.org/forum/viewtopic.php?f=10&t=6326&p=11426&hilit=mongodb+auth#p11485
void authenticate(Poco::MongoDB::Connection & connection, const std::string & database, const std::string & user, const std::string & password)
{
    Poco::MongoDB::Database db(database);

    /// Challenge-response authentication.
    std::string nonce;

    /// First step: request nonce.
    {
        auto command = db.createCommand();
        command->setNumberToReturn(1);
        command->selector().add<Int32>("getnonce", 1);

        Poco::MongoDB::ResponseMessage response;
        connection.sendRequest(*command, response);

        if (response.documents().empty())
            throw Exception(
                "Cannot authenticate in MongoDB: server returned empty response for 'getnonce' command",
                ErrorCodes::MONGODB_CANNOT_AUTHENTICATE);

        auto doc = response.documents()[0];
        try
        {
            double ok = doc->get<double>("ok", 0);
            if (ok != 1)
                throw Exception(
                    "Cannot authenticate in MongoDB: server returned response for 'getnonce' command that"
                    " has field 'ok' missing or having wrong value",
                    ErrorCodes::MONGODB_CANNOT_AUTHENTICATE);

            nonce = doc->get<std::string>("nonce", "");
            if (nonce.empty())
                throw Exception(
                    "Cannot authenticate in MongoDB: server returned response for 'getnonce' command that"
                    " has field 'nonce' missing or empty",
                    ErrorCodes::MONGODB_CANNOT_AUTHENTICATE);
        }
        catch (Poco::NotFoundException & e)
        {
            throw Exception(
                "Cannot authenticate in MongoDB: server returned response for 'getnonce' command that has missing required field: "
                    + e.displayText(),
                ErrorCodes::MONGODB_CANNOT_AUTHENTICATE);
        }
    }

    /// Second step: use nonce to calculate digest and send it back to the server.
    /// Digest is hex_md5(n.nonce + username + hex_md5(username + ":mongo:" + password))
    {
        std::string first = user + ":mongo:" + password;

        Poco::MD5Engine md5;
        md5.update(first);
        std::string digest_first(Poco::DigestEngine::digestToHex(md5.digest()));
        std::string second = nonce + user + digest_first;
        md5.reset();
        md5.update(second);