2834ad4911
Layout consistency: everything ckn-bw deploys to the host now lives under deploy/. ckn-bw's install_left4me_scripts copy-action goes away in lockstep with this commit and is replaced by target-side symlinks. Also updates all path references in docs, tests (conftest.py parents[] depth, test_overlay_helper.py HELPER_SOURCE), and deploy/README.md. Part of 2026-05-15-deployment-responsibility-design.md migration step 4.
81 lines
4 KiB
Bash
Executable file
81 lines
4 KiB
Bash
Executable file
#!/bin/bash
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# Privileged sandbox launcher for left4me script overlays.
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#
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# Invoked via sudo by the web user with two arguments:
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# <overlay_id> numeric overlay id; bind-mounts /var/lib/left4me/overlays/<id>
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# read-write at /overlay inside the sandbox.
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# <script_path> absolute path to a bash file already written by the web app;
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# bind-mounted read-only at /script.sh inside the sandbox.
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#
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# The script runs as a transient systemd .service with the full hardening
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# surface: cgroup limits + walltime kill, NoNewPrivileges, ProtectSystem,
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# ProtectHome, kernel-tunable / -module / -log protection, namespace
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# restriction, address-family restriction, capability bounding (empty),
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# seccomp filter (@system-service @network-io), MemoryDenyWriteExecute,
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# LockPersonality, RestrictSUIDSGID. Network namespace is *not* restricted —
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# scripts must reach the public internet to download workshop / l4d2center
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# / cedapug content. PID namespace is shared with the host (no
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# PrivatePID= directive in systemd); host PIDs are visible via /proc.
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# Same-uid attack surface (the sandbox runs as left4me, so do the
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# gameservers and the web app) is covered by the hardening profile plus
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# system-wide kernel.yama.ptrace_scope=2 — see
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# docs/superpowers/specs/2026-05-15-hardening-threat-model.md.
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set -euo pipefail
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# Self-wrap into PID 1's mount namespace before doing anything mount-related.
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# The web app's left4me-web.service has PrivateTmp=true, which gives it a
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# private mount namespace. When the worker invokes us via sudo, we inherit
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# that namespace; our `mount --bind` would land there. systemd-run below
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# spawns transient units in PID 1's namespace (where they don't see the
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# private bind), so the sandbox would bind onto an empty staging dir and
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# permission-deny on every write. The sentinel env var avoids an exec loop.
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if [[ "${L4D2_SANDBOX_IN_PID1_MNT_NS:-}" != "1" ]]; then
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exec env L4D2_SANDBOX_IN_PID1_MNT_NS=1 \
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/usr/bin/nsenter --mount=/proc/1/ns/mnt -- "$0" "$@"
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fi
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[[ $# -eq 2 ]] || { echo "usage: $0 <overlay_id> <script>" >&2; exit 64; }
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OVERLAY_ID=$1
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SCRIPT=$2
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[[ "$OVERLAY_ID" =~ ^[0-9]+$ ]] || { echo "bad overlay id" >&2; exit 64; }
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OVERLAY_DIR=/var/lib/left4me/overlays/$OVERLAY_ID
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[[ -d $OVERLAY_DIR ]] || { echo "no overlay dir at $OVERLAY_DIR" >&2; exit 65; }
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[[ -f $SCRIPT ]] || { echo "no script at $SCRIPT" >&2; exit 65; }
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if [[ "${LEFT4ME_SCRIPT_SANDBOX_DRY_RUN:-}" == "1" ]]; then
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echo "DRY RUN: overlay_id=$OVERLAY_ID script=$SCRIPT overlay_dir=$OVERLAY_DIR"
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exit 0
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fi
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SCRIPT_RC=0
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systemd-run --quiet --collect --wait --pipe \
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--unit="left4me-script-${OVERLAY_ID}-$$" \
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--slice=l4d2-build.slice \
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-p OOMScoreAdjust=500 \
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-p User=left4me -p Group=left4me \
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-p UMask=0022 \
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-p NoNewPrivileges=yes \
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-p ProtectSystem=strict -p ProtectHome=yes \
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-p PrivateTmp=yes -p PrivateDevices=yes -p PrivateIPC=yes \
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-p ProtectKernelTunables=yes -p ProtectKernelModules=yes \
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-p ProtectKernelLogs=yes -p ProtectControlGroups=yes \
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-p RestrictNamespaces=yes \
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-p RestrictAddressFamilies="AF_INET AF_INET6 AF_UNIX" \
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-p RestrictSUIDSGID=yes -p LockPersonality=yes \
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-p MemoryDenyWriteExecute=yes \
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-p SystemCallFilter="@system-service @network-io" \
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-p SystemCallArchitectures=native \
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-p CapabilityBoundingSet= -p AmbientCapabilities= \
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-p IPAddressDeny="127.0.0.0/8 ::1/128 169.254.0.0/16 fe80::/10 224.0.0.0/4 ff00::/8 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 100.64.0.0/10 fc00::/7" \
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-p TemporaryFileSystem="/etc /var/lib" \
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-p BindReadOnlyPaths="/etc/left4me/sandbox-resolv.conf:/etc/resolv.conf /etc/ssl /etc/ca-certificates /etc/nsswitch.conf /etc/alternatives ${SCRIPT}:/script.sh" \
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-p BindPaths="${OVERLAY_DIR}:/overlay" \
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-p WorkingDirectory=/overlay \
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-p Environment="HOME=/tmp PATH=/usr/bin:/usr/sbin OVERLAY=/overlay" \
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-p MemoryMax=4G -p MemorySwapMax=0 -p TasksMax=512 \
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-p CPUQuota=200% -p RuntimeMaxSec=3600 \
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-- /bin/bash /script.sh || SCRIPT_RC=$?
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exit $SCRIPT_RC
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