wt/finit
1
0 Fork 0
mirror of https://github.com/troglobit/finit.git synced 2026-10-17 10:49:34 +00:00
Code Issues Packages Projects Releases Wiki Activity
Files
d710a235130fe5fd009ba887166be1d6315e0efc
finit/doc/dbus.md
T
Joachim Wiberg d710a23513 dbus: gate the bus socket like INIT_SOCKET 
The D-Bus socket was bound world read/write, on the reasoning that
SO_PEERCRED authorizes each method anyway.  That leaves the read-only
surface open to every local user, and it quietly ignores --with-group:
a system that restricts initctl to the wheel group still handed the
same service state to anyone who asked over the bus.

Bind it 0660 and chown it to the configured group, the same gate the
fallback socket has always had.  libink takes the mode as an argument
rather than assuming one, since who may connect is the embedder's
policy, not the library's.

The mode is applied at bind(), so there is no window where the socket
is more permissive than intended.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
2026-08-13 10:14:48 +02:00

322 lines
16 KiB
Markdown
Raw Blame History

This file contains ambiguous Unicode characters
This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.
D-Bus Integration
=================
Finit ships with a built-in, brokerless [D-Bus][] implementation, **libink**
(`-link`), that exposes the running init system as a peer on its own private
bus, and optionally on the system bus when `dbus-daemon` is available.
Everything `initctl` does is also reachable from any generic D-Bus tooling —
`dbus-send`, `dbus-monitor`, `gdbus`, language bindings, dashboards,
monitoring agents, etc.
> [!NOTE]
> D-Bus support is enabled by default, opt out at build time with
> `--disable-dbus`, see [Building](build.md) for details. When disabled,
> `initctl` keeps using the legacy `INIT_SOCKET` transport and Finit
> exposes no bus.
Bus address
-----------
| Bus | Address |
|------------------------|---------------------------------------------|
| Local (always) | `unix:path=/run/finit/bus` |
| System (opportunistic) | `unix:path=/var/run/dbus/system_bus_socket` |
The **local** bus is brokerless: clients connect straight to Finit over a
Unix-domain socket using the standard D-Bus SASL EXTERNAL handshake. No
`dbus-daemon` is required, which makes it suitable for embedded systems that
don't ship one.
The socket is `0660`, owned by `root` and the group given to
`--with-group` at build time, the same gate as `/run/finit/socket` that
`initctl` falls back on. The bus reaches every operation `initctl`
does, so restricting one and not the other would leave the door open.
Members of that group may use it, see [Authorization](#authorization).
The **system** bus is best-effort: Finit probes for a running `dbus-daemon`
and, when reachable, claims the well-known name `org.finit` so that standard
tooling sees Finit just like any other system service:
```sh
dbus-send --system --print-reply --dest=org.finit /org/finit/manager \
org.finit.Manager1.ListServices
dbus-monitor --system "sender='org.finit'"
```
If no system bus is present (the common case on embedded targets), this step
is silently skipped.
Object tree
-----------
```
/
├── org/
│ └── finit/
│ ├── manager Manager1
│ ├── cond Cond1
│ └── service/
│ ├── keventd Service1 (one per service)
│ ├── sshd
│ └── …
└── org/freedesktop/DBus Standard well-known interfaces
```
Every node implements the usual stock interfaces:
| Interface | Purpose |
|---------------------------------------|-------------------------------------------|
| `org.freedesktop.DBus` | `Hello`, `AddMatch`, `RemoveMatch` |
| `org.freedesktop.DBus.Peer` | `Ping`, `GetMachineId` |
| `org.freedesktop.DBus.Introspectable` | `Introspect()` — XML description |
| `org.freedesktop.DBus.Properties` | `Get`, `GetAll` (Set not yet implemented) |
Note: `Hello`, `AddMatch`, and `RemoveMatch` are answered on the canonical
`/org/freedesktop/DBus` object only, as per the D-Bus specification.
`org.finit.Manager1`
--------------------
Lives at **`/org/finit/manager`**. Owns the global init operations
and the service registry.
### Methods
| Method | In sig | Out sig | Priv. | Notes |
|------------------------------|--------|---------|-------|-----------------------------------------------------------|
| `ListServices` | — | `as` | no | Returns identities (`name`, `name:id`) of loaded services |
| `GetService` | `s` | `o` | no | Resolves an identity to its `Service1` object path |
| `Start` | `s` | — | yes | Start the service(s) matching the identity |
| `Stop` | `s` | — | yes | Stop the service(s) matching the identity |
| `Restart` | `s` | — | yes | Restart (stop + start) the service(s) |
| `Reload` | — | — | yes | Re-read all `*.conf` and apply changes |
| `SetRunlevel` | `u` | — | yes | Transition to runlevel `u` (0–6) |
| `SetDebug` | — | — | yes | Toggle Finit's runtime debug flag |
| `Signal` | `su` | — | yes | Send signal `u` (1–31) to services matching identity `s` |
| `Suspend` | — | — | yes | `sync()` + suspend-to-RAM |
| `Reboot`, `Halt`, `Poweroff` | — | — | yes | Trigger the corresponding shutdown sequence |
### Properties
All read-only strings; observable via `Properties.Get` and
`Properties.GetAll`.
| Property | Type | Returns |
|----------------|------|--------------------------------------------------------|
| `Runlevel` | `s` | Current runlevel as a digit (`"2"`, `"3"`, …) or `"S"` |
| `PrevRunlevel` | `s` | Previous runlevel, same encoding, `"N"` when none |
| `Version` | `s` | Finit's version string (`PACKAGE_VERSION`) |
### Signals
| Signal | Body | Fires when |
|-----------------------|----------------------------------------|------------------------|
| `ServiceStateChanged` | `sss` — identity, old state, new state | Service transitions |
| `RunlevelChanged` | `ss` — old level, new level | System runlevel change |
State names emitted by `ServiceStateChanged` are stable wire strings:
`halted`, `done`, `dead`, `cleanup`, `teardown`, `stopping`, `setup`,
`paused`, `waiting`, `starting`, `running`. `RunlevelChanged` levels
use the same encoding as the `Runlevel` property: digits, `"S"`, `"N"`.
`org.finit.Service1` (per-service objects)
------------------------------------------
Lives at **`/org/finit/service/<encoded>`**, one object per loaded service.
`<encoded>` is the service identity (name, or `name:id` for templated
services) put through systemd-style `_HH` hex escaping — ASCII alphanumerics
and `_` pass through, anything else becomes `_HH` where `HH` is the hex byte.
Use `Manager1.GetService(identity)` to look up the exact path rather than
constructing it by hand.
| Method | In sig | Out sig | Priv. | Notes |
|-----------|--------|---------|-------|-------------------------------------------------------------|
| `Start` | — | — | yes | Equivalent to `Manager1.Start(<identity>)` for this service |
| `Stop` | — | — | yes | … |
| `Restart` | — | — | yes | … |
| `Reload` | — | — | yes | Reload (SIGHUP if supported, else restart) |
### Properties
All read-only; observable via `Properties.Get` and `Properties.GetAll`.
| Property | Type | Returns |
|-----------------|------|----------------------------------------------------------------|
| `Identity` | `s` | Service identity, `name` or `name:id` |
| `Name` | `s` | Program name (basename of the command) |
| `State` | `s` | Current status, same vocabulary as `initctl status` |
| `Pid` | `u` | Current PID, 0 when not running |
| `RestartCount` | `u` | Restarts since the last stable run |
| `Runlevels` | `u` | Allowed runlevels as a bitmask, bit N = runlevel N, bit 10 = S |
| `Description` | `s` | The service's `description` string |
| `Command` | `s` | Full command line, arguments included |
| `Conditions` | `s` | Declared conditions, raw `.conf` form |
| `Type` | `s` | Unit type: `service`, `task`, `run`, `sysv`, `tty`, `free` |
| `Origin` | `s` | Source `.conf` file, empty for built-ins |
| `Environment` | `s` | The service's `env` setting, raw |
| `PidFile` | `s` | Declared PID file, raw (`!` prefix included) |
| `User` | `s` | User the service runs as |
| `Group` | `s` | Group the service runs as |
| `Uptime` | `u` | Seconds since start, 0 when not running |
| `ExitStatus` | `u` | Raw `waitpid(2)` status from the last exit |
| `RestartsTotal` | `u` | Restarts over the service's lifetime |
| `RestartMax` | `u` | Restart limit before the service is blocked |
| `Starts` | `u` | Times started, for `manual-start` units |
| `ManualStart` | `b` | `manual-start` set in the `.conf` |
| `Forking` | `b` | Daemon forks to background |
| `Started` | `b` | Run/task completed successfully |
On every state transition the object also emits the standard
`org.freedesktop.DBus.Properties.PropertiesChanged` signal: `State`
in the changed dictionary, `Pid` and `RestartCount` invalidated (call
`Get` for fresh values).
The per-service surface lets generic tooling supply an object handle
once and then invoke methods on it, instead of repeatedly passing the
identity string.
`org.finit.Cond1`
-----------------
Lives at **`/org/finit/cond`**. Exposes Finit's
[condition system](conditions.md) to bus clients.
### Methods
| Method | In sig | Out sig | Priv. | Notes |
|---------|--------|---------|-------|--------------------------------------------------------------|
| `Get` | `s` | `s` | no | Returns `"on"`, `"off"`, or `"flux"` for the named condition |
| `Set` | `s` | — | yes | Assert a `usr/<name>` condition |
| `Clear` | `s` | — | yes | Deassert a `usr/<name>` condition |
| `List` | — | `as` | no | Names of all known conditions |
| `Dump` | — | `a(ss)` | no | `(name, state)` pairs for everything `List` returns |
Note: non-`usr/*` paths are rejected with `InvalidArgs` -- system
conditions belong to Finit's state machine.
### Signals
| Signal | Body | Fires when |
|--------------------|------------------------|---------------------------------------|
| `ConditionChanged` | `ss` — name, new state | A condition is asserted or deasserted |
Authorization
-------------
Privileged methods reject any caller whose peer `uid` isn't 0. On the
**local** bus the kernel's `SO_PEERCRED` socket option tells Finit exactly
who's calling, so privilege escalation through the bus is impossible.
On the **system** bus, all incoming traffic is treated as unprivileged: it
arrives through `dbus-daemon` (typically running as root) and Finit cannot yet
ask the daemon for the real requester's uid via `GetConnectionUnixUser`. This
means external tooling can freely `Get`/`Introspect`/`ListServices`, but every
state-changing method returns `org.freedesktop.DBus.Error.AccessDenied`.
Per-sender uid lookup is on the roadmap.
When a privileged method is rejected the error name is exactly
`org.freedesktop.DBus.Error.AccessDenied`, and the body carries a short reason
string (e.g. `"permission denied: Start requires root"`).
`initctl` integration
---------------------
`initctl` transparently routes through D-Bus when the bus socket is present,
and falls back to the legacy `INIT_SOCKET` transport otherwise. Concretely,
the following subcommands use the bus first:
| Subcommand | Method |
|----------------------------|--------------------------------------------------|
| `initctl start` | `Manager1.Start(svc)` |
| `initctl stop` | `Manager1.Stop(svc)` |
| `initctl restart` | `Manager1.Restart(svc)` |
| `initctl reload` | `Manager1.Reload()` |
| `initctl reload S` | `Service1.Reload()` (per-svc) |
| `initctl reboot` | `Manager1.Reboot()` |
| `initctl halt` | `Manager1.Halt()` |
| `initctl poweroff` | `Manager1.Poweroff()` |
| `initctl suspend` | `Manager1.Suspend()` |
| `initctl debug` | `Manager1.SetDebug()` |
| `initctl signal` | `Manager1.Signal(svc, signo)` |
| `initctl runlevel` | `Properties.Get(Manager1.Runlevel/PrevRunlevel)` |
| `initctl cond set/get/clear` | `Cond1.{Set,Get,Clear}`, `clr` is an alias |
Two `initctl` subcommands are pure D-Bus features without legacy equivalents:
* `initctl monitor` — subscribes to every signal on the local bus and prints
one line per delivery (with timestamp, interface and member). Same idea as
`dbus-monitor`, but scoped to Finit and with no need to pass `--address`.
* `initctl cond` emits the standard `Cond1.ConditionChanged` signal as a side
effect, so subscribers observe user-driven state changes the same way they
observe service-driven ones.
Examples
--------
The examples below use `dbus-send` and `dbus-monitor`, which ship as part of
the [dbus][] reference implementation; they're widely packaged and don't pull
in any extra runtime. Any tool that speaks D-Bus over an AF_UNIX socket works
equally well — `gdbus`, Python's `jeepney`/`dasbus`, etc. — substitute their
syntax for setting the bus address. The wire protocol is the compatibility
surface: Finit's own **libink** is an internal implementation detail, external
clients should use any standard D-Bus library.
When `org.finit` is registered on the system bus you can replace
`--address=unix:path=/run/finit/bus` with `--system` in any example below.
List the running services:
```sh
dbus-send --address=unix:path=/run/finit/bus \
--type=method_call --print-reply --dest=org.finit \
/org/finit/manager \
org.finit.Manager1.ListServices
```
Read the current runlevel via the Properties interface:
```sh
dbus-send --address=unix:path=/run/finit/bus \
--type=method_call --print-reply --dest=org.finit \
/org/finit/manager \
org.freedesktop.DBus.Properties.Get \
string:org.finit.Manager1 string:Runlevel
```
Subscribe to every state change on the manager object:
```sh
dbus-monitor --address=unix:path=/run/finit/bus \
"type='signal',interface='org.finit.Manager1'"
```
Or use `initctl monitor`, which does the same without any address
plumbing.
Restart a service by its object path:
```sh
dbus-send --address=unix:path=/run/finit/bus \
--type=method_call --dest=org.finit \
/org/finit/service/sshd \
org.finit.Service1.Restart
```
Trigger a `usr/`-condition assertion that wakes any dependent service:
```sh
dbus-send --address=unix:path=/run/finit/bus \
--type=method_call --dest=org.finit \
/org/finit/cond \
org.finit.Cond1.Set string:"data-ready"
```
The `--dest=org.finit` argument is informational on the local
brokerless bus — Finit accepts any destination because there's no
broker to route by name — but `dbus-send` requires it syntactically.
[dbus]: https://gitlab.freedesktop.org/dbus/dbus
[D-Bus]: https://dbus.freedesktop.org/doc/dbus-specification.html
Reference in new issue View Git Blame Copy Permalink