82 lines
3.7 KiB
Bash
Executable File
82 lines
3.7 KiB
Bash
Executable File
#!/usr/bin/env bash
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set -uo pipefail
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# CASAN Track C — TRUE runtime isolation via container (C6 / V22, production form).
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#
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# Upgrades the static-policy scaffold (sandbox-run.sh) to real kernel isolation:
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# the command runs inside a locked-down container where the KERNEL — not a grep —
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# neutralises escapes:
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# --network=none → no egress at all
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# --read-only → root filesystem is immutable (can't write outside workspace)
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# --pids-limit → fork bombs are capped
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# --memory/--cpus → resource abuse is bounded
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# -v <ws>:/work:rw → ONLY the workspace is writable; host $HOME/.ssh is NOT mounted
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# --cap-drop=ALL --security-opt=no-new-privileges → no privilege escalation
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# --user=65532:65532 → workload process is never root in the container
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#
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# Usage:
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# sandbox-container.sh --workspace <dir> [--image busybox] [--timeout 20]
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# [--memory 256m] [--pids 128] [--cpus 1] -- <command...>
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# Exit: command's exit code · 124 timeout · 2 policy/setup error · 127 no docker.
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SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
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IMAGE="${CASAN_SANDBOX_IMAGE:-busybox}"
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WORKSPACE="$PWD"; TIMEOUT="${CASAN_SANDBOX_TIMEOUT:-20}"
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MEMORY="${CASAN_SANDBOX_MEMORY:-256m}"; PIDS="${CASAN_SANDBOX_PIDS:-128}"; CPUS="${CASAN_SANDBOX_CPUS:-1}"
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USER_SPEC="${CASAN_SANDBOX_USER:-65532:65532}"
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while [[ "$#" -gt 0 ]]; do
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case "$1" in
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--workspace) WORKSPACE="${2:-}"; shift 2 ;;
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--image) IMAGE="${2:-}"; shift 2 ;;
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--timeout) TIMEOUT="${2:-}"; shift 2 ;;
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--memory) MEMORY="${2:-}"; shift 2 ;;
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--pids) PIDS="${2:-}"; shift 2 ;;
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--cpus) CPUS="${2:-}"; shift 2 ;;
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--user) USER_SPEC="${2:-}"; shift 2 ;;
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--) shift; break ;;
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*) echo "sandbox-container: unknown arg $1" >&2; exit 2 ;;
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esac
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done
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[[ "$#" -ge 1 ]] || { echo "Usage: sandbox-container.sh --workspace <dir> -- <command...>" >&2; exit 2; }
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command -v docker >/dev/null 2>&1 || { echo "SANDBOX_CONTAINER_NO_DOCKER" >&2; exit 127; }
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docker info >/dev/null 2>&1 || { echo "SANDBOX_CONTAINER_DOCKER_DOWN" >&2; exit 127; }
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[[ "$USER_SPEC" =~ ^[0-9]+:[0-9]+$ ]] || { echo "SANDBOX_CONTAINER_BAD_USER" >&2; exit 2; }
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# A non-root process is always required. Production additionally refuses a
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# rootful Docker daemon because a compromised daemon socket defeats container
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# isolation. Local developer/test profiles may use a rootful daemon, but cannot
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# claim that configuration as a hardened production runner.
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if [[ "${CASAN_PROFILE:-}" == "prod" || "${CASAN_SANDBOX_REQUIRE_ROOTLESS:-0}" == "1" ]]; then
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docker info --format '{{json .SecurityOptions}}' 2>/dev/null | grep -q 'rootless' \
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|| { echo "SANDBOX_CONTAINER_ROOTLESS_REQUIRED" >&2; exit 2; }
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fi
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WS_ABS="$(cd "$WORKSPACE" 2>/dev/null && pwd)" || { echo "SANDBOX_CONTAINER_BAD_WORKSPACE" >&2; exit 2; }
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# Join the command into a single shell string to run inside the container.
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CMD="$*"
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# Hardened container. --init reaps zombies; tmpfs gives a small writable /tmp
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# without a writable rootfs. The wall-clock timeout goes through tool-exec.sh
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# (portable: `timeout` if present, else a perl alarm — macOS has no coreutils
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# `timeout`). Container name is tracked so a timed-out container is force-removed.
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CID="casan-sbx-$$-${RANDOM}"
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set +e
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bash "$SCRIPT_DIR/tool-exec.sh" "$TIMEOUT" -- \
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docker run --rm --init --name "$CID" \
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--network=none --read-only \
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--pids-limit="$PIDS" --memory="$MEMORY" --cpus="$CPUS" \
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--user "$USER_SPEC" --cap-drop=ALL --security-opt=no-new-privileges \
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--tmpfs /tmp:rw,size=16m \
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-v "$WS_ABS":/work:rw -w /work \
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"$IMAGE" sh -c "$CMD"
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rc=$?
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set -e
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if [[ "$rc" -eq 124 ]]; then
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docker rm -f "$CID" >/dev/null 2>&1 || true
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echo "SANDBOX_CONTAINER_TIMEOUT after ${TIMEOUT}s" >&2
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exit 124
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fi
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exit "$rc"
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