failed miserably at hack.lu

2025/hack.lu/misc/SKAL/public/Dockerfile

@@ -0,0 +1,21 @@
+FROM debian:bookworm-slim@sha256:b1a741487078b369e78119849663d7f1a5341ef2768798f7b7406c4240f86aef
+
+COPY docker-stuff/ynetd /sbin/ynetd
+COPY docker-stuff/readflag /readflag
+COPY flag.txt /flag.txt
+
+RUN chown root:root /readflag /flag.txt && \
+    chmod  500 /sbin/ynetd && \
+    chmod 2555 /readflag   && \
+    chmod  040 /flag.txt
+
+WORKDIR /app
+COPY skal.sh /app/skal.sh
+
+RUN useradd --no-create-home --shell /bin/bash ctf
+USER ctf
+RUN ! find / -writable -or -user "$(id -un)" -or -group $(id -Gn | sed -e 's/ / -or -group /g') 2> /dev/null | grep -Ev -m 1 '^(/dev/|/proc/|/sys/|/tmp|/var/tmp|/run/lock|/var/lock)'
+USER root
+RUN find / -ignore_readdir_race -type f \( -perm -4000 -o -perm -2000 \) -not -wholename /readflag -delete
+
+CMD ynetd -lt 240 -d /app -sh y -se y -np y '/app/skal.sh'

2025/hack.lu/misc/SKAL/public/docker-compose.yml

@@ -0,0 +1,10 @@
+services:
+  skal:
+    build: .
+    ports:
+      - "1024:1024"
+    cap_add:
+      - SYS_ADMIN
+    security_opt:
+      - apparmor=unconfined
+    restart: unless-stopped

2025/hack.lu/misc/SKAL/public/flag.txt

@@ -0,0 +1 @@
+flag{fakeflag}

2025/hack.lu/misc/SKAL/public/skal.sh

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+
+RED="\e[31m"
+GREEN="\e[32m"
+BROWN="\e[33m"
+RESET="\e[0m"
+ALLOWED_CHARS='^[${}![:space:]:_=()]+$'
+
+echo -e "\e[1;34m
+⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⣀⣀⠀⠀⣀⣄⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+⠀⠀⠀⠀⠀⠀⠀⠀⠀⢠⡴⠦⣤⣴⡟⠉⠉⡗⠚⡇⠀⠈⡷⢤⠖⠒⠲⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+⠀⠀⠀⠀⠀⠀⠀⢀⣀⡇⠀⠀⢸⠀⡇⠀⠀⠇⠀⡇⠀⠀⡇⢸⠀⠀⢠⠋⡝⠉⠓⢦⠀⠀⠀⠀⠀⠀⠀⠀
+⠀⠀⠀⠀⠀⢠⠊⠁⢣⢰⠀⠀⠈⡆⢳⠀⠀⠀⠀⡇⠀⢸⠀⡇⠀⠀⡜⢰⠃⠀⠀⡜⢦⢤⣀⠀⠀⠀⠀⠀
+⠀⠀⠀⡠⢴⠻⡀⠀⠈⡎⡇⠀⠀⢃⢸⠀⠀⢸⠀⡇⠀⢸⢀⡇⠀⢠⠃⡎⠀⠀⡼⢡⠃⠀⠙⡆⠀⠀⠀⠀
+⠀⠀⢸⠁⠀⢣⢱⡀⠀⢸⣸⡀⠀⢸⠈⡄⠀⢸⠀⡇⠀⠘⢸⠀⠀⡸⢰⠁⠀⢰⢡⠏⠀⠀⡜⡿⢤⡀⠀⠀
+⠀⣠⠞⣷⡄⠀⢣⢣⠀⠀⢧⢇⠀⠈⡆⡇⠀⢸⠀⡇⠀⡇⡼⠀⢀⠇⡏⠀⢠⢇⠎⠀⢀⡜⡜⠁⠀⢳⠀⠀
+⢸⡁⠀⠈⢻⣦⠀⢫⢧⠀⠘⡾⡄⠀⣇⢡⠀⢸⠀⡇⠀⡇⡇⠀⣸⢸⠀⢀⠏⡜⠀⢀⢎⠞⠀⢀⡴⡻⡄⠀
+⣰⠻⣆⠀⠀⠻⣷⡀⢻⣇⠀⢹⢧⠀⢸⢸⠀⢸⠀⡇⢠⢿⠃⠀⡇⡇⠀⡜⡾⠀⢠⢾⠎⠀⡰⢫⠞⠀⡟⠀
+⢹⣅⠙⢷⣄⠀⠙⣷⡀⢻⡄⠈⣿⡄⠘⡞⡆⢸⠀⡇⢸⢸⠀⢸⣸⠀⡸⡽⠁⢠⣯⠋⣠⣾⡖⢁⡠⠚⣿⡄
+⠘⣏⠳⣄⠙⣦⡀⠘⢧⠀⢻⡄⠸⣧⠀⠇⡇⢸⠀⡇⢸⡌⠀⣇⠇⢰⣱⠁⣠⡻⢃⡴⡷⢋⡴⢋⡤⣺⠇⠀
+⠀⢹⡕⢄⠑⢌⠛⢦⠈⢣⡀⢻⡀⢳⠀⢸⢳⢸⠀⡇⣎⡇⢸⠽⢠⠇⠁⣰⡿⢡⣾⢞⣴⣯⡔⣫⢴⠟⠀⠀
+⠀⠀⠙⢦⣝⢦⡑⢄⠳⣌⠳⡈⢧⠈⡆⠸⣼⠸⡀⡇⡏⠁⡏⢀⠎⠀⡰⠉⡱⠋⡡⣫⣞⣽⣋⣴⠟⠀⠀⠀
+⠀⠀⠀⠀⠉⠻⢿⣮⡳⣌⢦⡱⡌⣆⢸⠀⡟⡆⡇⡇⡇⢸⠁⡜⠀⡼⠁⡜⠁⣪⠞⣿⡵⠟⠉⠀⠀⠀⠀⠀
+⠀⠀⠀⠀⠀⠀⠀⠙⡾⣾⣷⣵⡜⡜⡄⠇⢣⡇⡇⢳⠁⡎⠀⠀⡼⢁⠞⠠⢾⡵⠟⠉⠀⠀⠀⠀⠀⠀⠀⠀
+⠀⠀⠀⠀⠀⠀⠀⠀⣷⠈⠛⢿⣾⣾⣾⠘⠈⠁⠇⠀⠀⠁⠀⠾⠁⢀⣤⠞⢫⡗⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+⠀⠀⠀⠀⠀⠀⠀⠀⠘⢧⣄⠀⠙⠿⣟⠀⠀⠀⠀⠀⠀⠀⠀⢀⡴⠛⣡⡴⠋⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠙⠒⠦⠬⠷⢄⡀⠀⠀⠀⣠⠴⠟⠚⠉⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠛⠒⠋⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀\n"
+
+echo -e "${BROWN}\n[*] Tillåtna tecken: $ALLOWED_CHARS\n${RESET}"
+
+while true; do
+    echo -e "${GREEN}$$@skal${BROWN}$ ${RESET}\c"
+    read -rs command
+    if [[ $command =~ $ALLOWED_CHARS ]]; then
+        eval "$command"
+    else
+        echo -e "${RED}[-] Fel: Kommandot innehåller otillåtna tecken.${RESET}\n"
+    fi
+done