FROM ubuntu:25.04

RUN apt-get update \
    && apt-get install -y --no-install-recommends socat \
    && rm -rf /var/lib/apt/lists/*

RUN useradd -m ctf

WORKDIR /home/ctf

COPY chal /home/ctf/chal
COPY flag.txt /home/ctf/flag.txt

RUN chown ctf:ctf /home/ctf/flag.txt \
    && chmod 444 /home/ctf/flag.txt \
    && chmod 755 /home/ctf/chal

USER ctf

EXPOSE 8080

CMD ["socat", "TCP-LISTEN:8080,reuseaddr,fork", "EXEC:./chal,stderr"]
