commit b31f3e0291b38c5d09191506c9a882c1a83ff1e3
Author: Christian Nennemann <christian@nennemann.de>
Date:   Sun Feb 22 22:19:03 2026 +0100

    Initial commit
    
    Co-authored-by: Cursor <cursoragent@cursor.com>

diff --git a/sandbox.sh b/sandbox.sh
new file mode 100755
index 0000000..8993fdc
--- /dev/null
+++ b/sandbox.sh
@@ -0,0 +1,396 @@
+#!/usr/bin/env bash
+# sandbox.sh - Safe AI coding agent sandbox
+# Usage: ./sandbox.sh <command> [options]
+# Commands: setup, run, shell, status, clean
+set -euo pipefail
+
+# ── Config ────────────────────────────────────────────────────────────────────
+SANDBOX_IMAGE="${SANDBOX_IMAGE:-ai-sandbox:latest}"
+SANDBOX_DIR="${SANDBOX_DIR:-$HOME/.ai-sandbox}"
+WORKDIR_HOST="${SANDBOX_DIR}/workspace"
+CONFIG_DIR="${SANDBOX_DIR}/config"      # persistent agent credentials (host-only, chmod 700)
+TMPDIR_SIZE="${TMPDIR_SIZE:-512m}"
+CPU_LIMIT="${CPU_LIMIT:-1.0}"
+MEM_LIMIT="${MEM_LIMIT:-512m}"
+NETWORK_MODE="${NETWORK_MODE:-none}"   # none = no internet; bridge = allow
+
+# Colors
+RED='\033[0;31m'; GREEN='\033[0;32m'; YELLOW='\033[1;33m'; CYAN='\033[0;36m'; NC='\033[0m'
+info()    { echo -e "${CYAN}[sandbox]${NC} $*"; }
+ok()      { echo -e "${GREEN}[ok]${NC} $*"; }
+warn()    { echo -e "${YELLOW}[warn]${NC} $*"; }
+die()     { echo -e "${RED}[error]${NC} $*" >&2; exit 1; }
+
+# ── OS detection ──────────────────────────────────────────────────────────────
+OS="$(uname -s)"
+case "$OS" in
+  Linux)  PLATFORM=linux ;;
+  Darwin) PLATFORM=macos ;;
+  *)      die "Unsupported OS: $OS" ;;
+esac
+
+# ── Helpers ───────────────────────────────────────────────────────────────────
+require_docker() {
+  command -v docker &>/dev/null || die "Docker not found. Run: ./sandbox.sh setup"
+  docker info &>/dev/null       || die "Docker daemon not running."
+}
+
+has_nsjail() {
+  [[ "$PLATFORM" == "linux" ]] && command -v nsjail &>/dev/null
+}
+
+has_firejail() {
+  command -v firejail &>/dev/null
+}
+
+# Verify that host networking/DNS was not changed by this script
+assert_host_untouched() {
+  # We never modify /etc/hosts, /etc/resolv.conf, iptables, or network interfaces.
+  # This function just documents that guarantee and does a quick sanity check.
+  if [[ "$PLATFORM" == "linux" ]]; then
+    local resolv_hash_before resolv_hash_after
+    resolv_hash_before="${_RESOLV_HASH_BEFORE:-}"
+    resolv_hash_after="$(md5sum /etc/resolv.conf 2>/dev/null | cut -d' ' -f1)"
+    if [[ -n "$resolv_hash_before" && "$resolv_hash_before" != "$resolv_hash_after" ]]; then
+      die "/etc/resolv.conf was modified unexpectedly! Aborting."
+    fi
+  fi
+}
+
+snapshot_host() {
+  if [[ "$PLATFORM" == "linux" ]]; then
+    export _RESOLV_HASH_BEFORE="$(md5sum /etc/resolv.conf 2>/dev/null | cut -d' ' -f1)"
+  fi
+}
+
+# ── Dockerfile (embedded) ─────────────────────────────────────────────────────
+write_dockerfile() {
+  local dir="$1"
+  cat > "$dir/Dockerfile" <<'EOF'
+FROM ubuntu:24.04
+
+ARG DEBIAN_FRONTEND=noninteractive
+
+# System packages
+RUN apt-get update -qq && apt-get install -y --no-install-recommends \
+    python3 python3-pip python3-venv \
+    git curl wget ca-certificates gnupg \
+    build-essential \
+    && apt-get clean && rm -rf /var/lib/apt/lists/*
+
+# Node.js LTS (via NodeSource — newer than Ubuntu's bundled version)
+RUN curl -fsSL https://deb.nodesource.com/setup_lts.x | bash - \
+    && apt-get install -y --no-install-recommends nodejs \
+    && apt-get clean && rm -rf /var/lib/apt/lists/*
+
+# GitHub CLI
+RUN curl -fsSL https://cli.github.com/packages/githubcli-archive-keyring.gpg \
+      | gpg --dearmor -o /usr/share/keyrings/githubcli-archive-keyring.gpg \
+    && echo "deb [arch=$(dpkg --print-architecture) \
+         signed-by=/usr/share/keyrings/githubcli-archive-keyring.gpg] \
+         https://cli.github.com/packages stable main" \
+      > /etc/apt/sources.list.d/github-cli.list \
+    && apt-get update -qq && apt-get install -y --no-install-recommends gh \
+    && apt-get clean && rm -rf /var/lib/apt/lists/*
+
+# AI CLI tools (npm global)
+RUN npm install -g --no-audit --no-fund \
+    @anthropic-ai/claude-code \
+    @google/gemini-cli
+
+# Non-root sandbox user (fixed uid/gid 999)
+RUN groupadd -r -g 999 agent \
+    && useradd -r -u 999 -g agent -m -d /home/agent agent
+
+# Workspace dir
+RUN mkdir -p /workspace && chown agent:agent /workspace
+
+USER agent
+ENV HOME=/home/agent
+
+# Stub dirs for bind/tmpfs mounts (must exist before runtime mounts)
+RUN mkdir -p \
+    /home/agent/.claude \
+    /home/agent/.cache \
+    /home/agent/.config/gh \
+    /home/agent/.config/gemini \
+    /home/agent/.local/state
+
+# gh Copilot extension — baked into image; read-only at runtime is fine
+RUN gh extension install github/gh-copilot 2>/dev/null || true
+
+USER root
+WORKDIR /workspace
+USER agent
+
+ENV PYTHONDONTWRITEBYTECODE=1
+ENV PYTHONUNBUFFERED=1
+
+CMD ["/bin/bash"]
+EOF
+}
+
+# ── Commands ──────────────────────────────────────────────────────────────────
+
+cmd_setup() {
+  snapshot_host
+  info "Setting up AI sandbox on $PLATFORM..."
+
+  # 1. Docker
+  if ! command -v docker &>/dev/null; then
+    if [[ "$PLATFORM" == "linux" ]]; then
+      info "Installing Docker (rootless)..."
+      # Use official convenience script but only if user confirms
+      read -rp "  Install Docker via get.docker.com? [y/N] " ans
+      [[ "$ans" =~ ^[Yy]$ ]] || die "Aborted. Install Docker manually: https://docs.docker.com/engine/install/"
+      curl -fsSL https://get.docker.com | sh
+      # Rootless setup (optional, avoids root daemon)
+      if command -v dockerd-rootless-setuptool.sh &>/dev/null; then
+        info "Configuring rootless Docker..."
+        dockerd-rootless-setuptool.sh install 2>/dev/null || warn "Rootless setup skipped."
+      fi
+    elif [[ "$PLATFORM" == "macos" ]]; then
+      if command -v brew &>/dev/null; then
+        info "Installing Docker via Homebrew..."
+        brew install --cask docker
+        info "Please open Docker.app to finish installation, then re-run: ./sandbox.sh setup"
+        open /Applications/Docker.app 2>/dev/null || true
+        exit 0
+      else
+        die "Install Docker Desktop from https://docs.docker.com/desktop/mac/install/"
+      fi
+    fi
+  else
+    ok "Docker already installed: $(docker --version)"
+  fi
+
+  # 2. Verify Docker daemon
+  if ! docker info &>/dev/null; then
+    die "Docker daemon not running. Start Docker and retry."
+  fi
+
+  # 3. Optional: nsjail on Linux
+  if [[ "$PLATFORM" == "linux" ]] && ! command -v nsjail &>/dev/null; then
+    warn "nsjail not found (optional). For extra hardening: sudo apt install nsjail"
+  elif has_nsjail; then
+    ok "nsjail available: $(nsjail --version 2>&1 | head -1)"
+  fi
+
+  # 4. Create sandbox dirs
+  mkdir -p "$WORKDIR_HOST"
+  ok "Workspace: $WORKDIR_HOST"
+
+  # Persistent config dirs — host-only, never world-readable
+  mkdir -p \
+    "$CONFIG_DIR/claude" \
+    "$CONFIG_DIR/gh" \
+    "$CONFIG_DIR/gemini"
+  chmod 700 "$CONFIG_DIR" "$CONFIG_DIR/claude" "$CONFIG_DIR/gh" "$CONFIG_DIR/gemini"
+  ok "Config dir:  $CONFIG_DIR (chmod 700)"
+
+  # 5. Build Docker image
+  local build_dir
+  build_dir="$(mktemp -d)"
+  write_dockerfile "$build_dir"
+  info "Building sandbox image ($SANDBOX_IMAGE)..."
+  docker build -t "$SANDBOX_IMAGE" "$build_dir" --quiet
+  rm -rf "$build_dir"
+  ok "Image built: $SANDBOX_IMAGE"
+
+  assert_host_untouched
+  echo ""
+  ok "Setup complete. Host network/DNS: unchanged."
+  info "Run agent code:  ./sandbox.sh run <script.py>"
+  info "Interactive:     ./sandbox.sh shell"
+}
+
+cmd_run() {
+  require_docker
+  snapshot_host
+
+  local script="${1:-}"
+  [[ -z "$script" ]] && die "Usage: ./sandbox.sh run <script> [args...]"
+  [[ -f "$script" ]] || die "File not found: $script"
+
+  local abs_script
+  abs_script="$(realpath "$script")"
+  local script_dir
+  script_dir="$(dirname "$abs_script")"
+  local script_file
+  script_file="$(basename "$abs_script")"
+
+  info "Running in sandbox: $script_file"
+  info "  Network:  $NETWORK_MODE"
+  info "  CPU:      $CPU_LIMIT"
+  info "  Memory:   $MEM_LIMIT"
+  [[ "$NETWORK_MODE" == "none" ]] && info "  Internet: BLOCKED"
+
+  # Detect language
+  local runner=""
+  case "$script_file" in
+    *.py)   runner="python3" ;;
+    *.js)   runner="node" ;;
+    *.sh)   runner="bash" ;;
+    *)      runner="" ;;  # executable or unknown
+  esac
+
+  local docker_args=(
+    docker run
+    --rm
+    --network "$NETWORK_MODE"
+    --cpus "$CPU_LIMIT"
+    --memory "$MEM_LIMIT"
+    --memory-swap "$MEM_LIMIT"                    # no swap
+    --read-only                                   # read-only rootfs
+    --tmpfs /tmp:size=128m,noexec                 # writable tmp, no exec
+    --tmpfs /home/agent/.cache:size=128m,uid=999,gid=999
+    --tmpfs /home/agent/.local/state:size=64m,uid=999,gid=999
+    --cap-drop ALL                                # drop all Linux capabilities
+    --security-opt no-new-privileges              # no privilege escalation
+    --security-opt seccomp=unconfined
+    --pids-limit 128                              # no fork bombs
+    -v "${script_dir}:/workspace:ro"              # mount script dir read-only
+    -v "${CONFIG_DIR}/claude:/home/agent/.claude:rw"
+    -v "${CONFIG_DIR}/gh:/home/agent/.config/gh:rw"
+    -v "${CONFIG_DIR}/gemini:/home/agent/.config/gemini:rw"
+    --workdir /workspace
+    "$SANDBOX_IMAGE"
+  )
+
+  # Optional nsjail wrapper on Linux
+  if has_nsjail && [[ "$PLATFORM" == "linux" ]]; then
+    info "  Extra:    nsjail wrapping enabled"
+    # nsjail wraps the entire docker run call for an extra namespace layer
+    # Note: this requires nsjail in PATH and appropriate permissions
+    exec nsjail \
+      --mode o \
+      --quiet \
+      --rlimit_nofile 64 \
+      --rlimit_nproc 32 \
+      --time_limit 300 \
+      --disable_clone_newcgroup \
+      -- "${docker_args[@]}" ${runner:+$runner} "$script_file" "${@:2}"
+  fi
+
+  "${docker_args[@]}" ${runner:+$runner} "$script_file" "${@:2}"
+
+  assert_host_untouched
+}
+
+cmd_shell() {
+  require_docker
+  snapshot_host
+
+  info "Opening interactive sandbox shell..."
+  info "  Network: $NETWORK_MODE"
+  [[ "$NETWORK_MODE" == "none" ]] && warn "  Internet is BLOCKED (set NETWORK_MODE=bridge to allow)"
+
+  mkdir -p "$WORKDIR_HOST"
+  mkdir -p "$CONFIG_DIR/claude" "$CONFIG_DIR/gh" "$CONFIG_DIR/gemini"
+
+  docker run \
+    --rm -it \
+    --network "$NETWORK_MODE" \
+    --cpus "$CPU_LIMIT" \
+    --memory "$MEM_LIMIT" \
+    --memory-swap "$MEM_LIMIT" \
+    --read-only \
+    --tmpfs /tmp:size=128m,noexec \
+    --tmpfs /home/agent/.cache:size=128m,uid=999,gid=999 \
+    --tmpfs /home/agent/.local/state:size=64m,uid=999,gid=999 \
+    --tmpfs /workspace:size=256m,uid=999,gid=999 \
+    --cap-drop ALL \
+    --security-opt no-new-privileges \
+    --pids-limit 128 \
+    -v "${WORKDIR_HOST}:/mnt/workspace:rw" \
+    -v "${CONFIG_DIR}/claude:/home/agent/.claude:rw" \
+    -v "${CONFIG_DIR}/gh:/home/agent/.config/gh:rw" \
+    -v "${CONFIG_DIR}/gemini:/home/agent/.config/gemini:rw" \
+    "$SANDBOX_IMAGE" \
+    /bin/bash
+
+  assert_host_untouched
+}
+
+cmd_status() {
+  require_docker
+  info "Sandbox image:"
+  docker images "$SANDBOX_IMAGE" 2>/dev/null || warn "Image not built yet."
+  echo ""
+  info "Running sandbox containers:"
+  docker ps --filter "ancestor=$SANDBOX_IMAGE" --format "table {{.ID}}\t{{.Status}}\t{{.CreatedAt}}" 2>/dev/null || true
+  echo ""
+  info "Workspace: $WORKDIR_HOST"
+  echo ""
+  info "Optional tools:"
+  has_nsjail   && ok "nsjail:   available" || warn "nsjail:   not found (optional)"
+  has_firejail && ok "firejail: available" || warn "firejail: not found (optional)"
+}
+
+cmd_clean() {
+  require_docker
+  info "Removing sandbox image and workspace..."
+  read -rp "  Remove image '$SANDBOX_IMAGE' and $WORKDIR_HOST? [y/N] " ans
+  [[ "$ans" =~ ^[Yy]$ ]] || { info "Aborted."; exit 0; }
+  docker rmi "$SANDBOX_IMAGE" 2>/dev/null && ok "Image removed." || warn "Image not found."
+  rm -rf "$WORKDIR_HOST" && ok "Workspace removed."
+}
+
+cmd_help() {
+  cat <<EOF
+
+  ${CYAN}sandbox.sh${NC} - Safe AI coding agent sandbox
+
+  ${YELLOW}Commands:${NC}
+    setup              Check/install deps, build sandbox image
+    run <script> [..] Run a script inside the sandbox (network OFF by default)
+    shell              Interactive bash shell inside the sandbox
+    status             Show image, running containers, available tools
+    clean              Remove image and workspace
+    help               This help
+
+  ${YELLOW}Installed AI agents:${NC}
+    claude               Claude Code CLI  (@anthropic-ai/claude-code)
+    gemini               Gemini CLI       (@google/gemini-cli)
+    gh copilot           GitHub Copilot   (gh extension)
+    gh                   GitHub CLI       (for auth + copilot)
+
+  ${YELLOW}Persistent credentials:${NC}
+    ~/.ai-sandbox/config/claude/   → /home/agent/.claude
+    ~/.ai-sandbox/config/gh/       → /home/agent/.config/gh
+    ~/.ai-sandbox/config/gemini/   → /home/agent/.config/gemini
+    (host dirs are chmod 700; survive container restarts)
+
+  ${YELLOW}Environment:${NC}
+    NETWORK_MODE=none    (default) No internet inside sandbox
+    NETWORK_MODE=bridge  Allow internet (use with caution)
+    MEM_LIMIT=512m       Memory cap (default: 512m)
+    CPU_LIMIT=1.0        CPU cores (default: 1.0)
+    SANDBOX_IMAGE=...    Docker image name (default: ai-sandbox:latest)
+
+  ${YELLOW}Examples:${NC}
+    ./sandbox.sh setup
+    ./sandbox.sh run agent.py
+    ./sandbox.sh shell
+    NETWORK_MODE=bridge ./sandbox.sh run fetch_data.py
+
+  ${YELLOW}Platforms:${NC}
+    Linux:  Docker + optional nsjail hardening
+    macOS:  Docker only
+
+EOF
+}
+
+# ── Entrypoint ────────────────────────────────────────────────────────────────
+CMD="${1:-help}"
+shift || true
+
+case "$CMD" in
+  setup)   cmd_setup "$@" ;;
+  run)     cmd_run "$@" ;;
+  shell)   cmd_shell "$@" ;;
+  status)  cmd_status "$@" ;;
+  clean)   cmd_clean "$@" ;;
+  help|-h|--help) cmd_help ;;
+  *) die "Unknown command: $CMD. Run ./sandbox.sh help" ;;
+esac