FROM ubuntu:25.10 AS libc-donor

FROM alpine:3.23

COPY --from=libc-donor /lib/x86_64-linux-gnu/libc.so.6 /usr/lib/libc.so.6
COPY --from=libc-donor /lib/x86_64-linux-gnu/ld-linux-x86-64.so.2 /lib64/ld-linux-x86-64.so.2

RUN apk add --no-cache socat \
    && rm -rf /var/cache/apk/*

WORKDIR /app
RUN adduser -D ctfuser

COPY flag.txt /app/flag.txt
COPY chall /app/chall

RUN chmod +x /app/chall

USER ctfuser

EXPOSE 5000

CMD [ "socat", "TCP-LISTEN:5000,reuseaddr,fork", "exec:/app/chall" ]
