system/dbus: use well-known address in spec

The session bus still performs non-standard formatting since it makes no sense for hakurei to start the session bus.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/app/app_test.go

@@ -250,7 +250,7 @@ func TestApp(t *testing.T) {
 				Args: []string{"zsh", "-c", "exec chromium "},
 				Env: []string{
 					"DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/65534/bus",
-					"DBUS_SYSTEM_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket",
+					"DBUS_SYSTEM_BUS_ADDRESS=unix:path=/var/run/dbus/system_bus_socket",
 					"HOME=/home/chronos",
 					"PULSE_COOKIE=" + hst.PrivateTmp + "/pulse-cookie",
 					"PULSE_SERVER=unix:/run/user/65534/pulse/native",
@@ -284,7 +284,7 @@ func TestApp(t *testing.T) {
 					Bind(m("/run/user/1971/hakurei/ebf083d1b175911782d413369b64ce7c/pulse"), m("/run/user/65534/pulse/native"), 0).
 					Place(m(hst.PrivateTmp+"/pulse-cookie"), bytes.Repeat([]byte{0}, pulseCookieSizeMax)).
 					Bind(m("/tmp/hakurei.0/ebf083d1b175911782d413369b64ce7c/bus"), m("/run/user/65534/bus"), 0).
-					Bind(m("/tmp/hakurei.0/ebf083d1b175911782d413369b64ce7c/system_bus_socket"), m("/run/dbus/system_bus_socket"), 0).
+					Bind(m("/tmp/hakurei.0/ebf083d1b175911782d413369b64ce7c/system_bus_socket"), m("/var/run/dbus/system_bus_socket"), 0).
 					Remount(m("/"), syscall.MS_RDONLY),
 				SeccompPresets: bits.PresetExt | bits.PresetDenyDevel,
 				HostNet:        true,
@@ -394,7 +394,7 @@ func TestApp(t *testing.T) {
 				Args: []string{"/nix/store/yqivzpzzn7z5x0lq9hmbzygh45d8rhqd-chromium-start"},
 				Env: []string{
 					"DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1971/bus",
-					"DBUS_SYSTEM_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket",
+					"DBUS_SYSTEM_BUS_ADDRESS=unix:path=/var/run/dbus/system_bus_socket",
 					"HOME=/var/lib/persist/module/hakurei/0/1",
 					"PULSE_COOKIE=" + hst.PrivateTmp + "/pulse-cookie",
 					"PULSE_SERVER=unix:/run/user/1971/pulse/native",
@@ -434,7 +434,7 @@ func TestApp(t *testing.T) {
 					Bind(m("/run/user/1971/hakurei/8e2c76b066dabe574cf073bdb46eb5c1/pulse"), m("/run/user/1971/pulse/native"), 0).
 					Place(m(hst.PrivateTmp+"/pulse-cookie"), bytes.Repeat([]byte{0}, pulseCookieSizeMax)).
 					Bind(m("/tmp/hakurei.0/8e2c76b066dabe574cf073bdb46eb5c1/bus"), m("/run/user/1971/bus"), 0).
-					Bind(m("/tmp/hakurei.0/8e2c76b066dabe574cf073bdb46eb5c1/system_bus_socket"), m("/run/dbus/system_bus_socket"), 0).
+					Bind(m("/tmp/hakurei.0/8e2c76b066dabe574cf073bdb46eb5c1/system_bus_socket"), m("/var/run/dbus/system_bus_socket"), 0).
 					Remount(m("/"), syscall.MS_RDONLY),
 				SeccompPresets: bits.PresetExt | bits.PresetDenyTTY | bits.PresetDenyDevel,
 				HostNet:        true,
@@ -655,7 +655,7 @@ func (k *stubNixOS) evalSymlinks(path string) (string, error) {
 		return "/run/user/1971", nil
 	case "/tmp/hakurei.0":
 		return "/tmp/hakurei.0", nil
-	case "/run/dbus":
+	case "/var/run/dbus":
 		return "/run/dbus", nil
 	case "/dev/kvm":
 		return "/dev/kvm", nil

internal/app/spdbus.go

@@ -50,7 +50,7 @@ func (s *spDBusOp) toContainer(state *outcomeStateParams) error {
 	state.env["DBUS_SESSION_BUS_ADDRESS"] = "unix:path=" + sessionInner.String()
 	state.params.Bind(state.instancePath().Append("bus"), sessionInner, 0)
 	if s.ProxySystem {
-		systemInner := fhs.AbsRun.Append("dbus/system_bus_socket")
+		systemInner := fhs.AbsVar.Append("run/dbus/system_bus_socket")
 		state.env["DBUS_SYSTEM_BUS_ADDRESS"] = "unix:path=" + systemInner.String()
 		state.params.Bind(state.instancePath().Append("system_bus_socket"), systemInner, 0)
 	}

system/dbus/dbus.go

@@ -8,8 +8,31 @@ import (
 )
 
 const (
+	/*SessionBusAddress is the name of the environment variable where the address of the login session message bus is given in.
+
+	If that variable is not set, applications may also try to read the address from the X Window System root window property _DBUS_SESSION_BUS_ADDRESS.
+	The root window property must have type STRING. The environment variable should have precedence over the root window property.
+
+	The address of the login session message bus is given in the DBUS_SESSION_BUS_ADDRESS environment variable.
+	If DBUS_SESSION_BUS_ADDRESS is not set, or if it's set to the string "autolaunch:",
+	the system should use platform-specific methods of locating a running D-Bus session server,
+	or starting one if a running instance cannot be found.
+	Note that this mechanism is not recommended for attempting to determine if a daemon is running.
+	It is inherently racy to attempt to make this determination, since the bus daemon may be started just before or just after the determination is made.
+	Therefore, it is recommended that applications do not try to make this determination for their functionality purposes, and instead they should attempt to start the server.
+
+	This package diverges from the specification, as the caller is unlikely to be an X client, or be in a position to autolaunch a dbus server.
+	So a fallback address with a socket located in the well-known default XDG_RUNTIME_DIR formatting is used.*/
 	SessionBusAddress = "DBUS_SESSION_BUS_ADDRESS"
-	SystemBusAddress  = "DBUS_SYSTEM_BUS_ADDRESS"
+
+	/*SystemBusAddress is the name of the environment variable where the address of the system message bus is given in.
+
+	If that variable is not set, applications should try to connect to the well-known address unix:path=/var/run/dbus/system_bus_socket.
+	Implementations of the well-known system bus should listen on an address that will result in that connection being successful.*/
+	SystemBusAddress = "DBUS_SYSTEM_BUS_ADDRESS"
+
+	// FallbackSystemBusAddress is used when [SystemBusAddress] is not set.
+	FallbackSystemBusAddress = "unix:path=/var/run/dbus/system_bus_socket"
 )
 
 var (
@@ -30,7 +53,7 @@ func Address() (session, system string) {
 		// resolve upstream system bus address
 		if addr, ok := os.LookupEnv(SystemBusAddress); !ok {
 			// fall back to default hardcoded value
-			addresses[1] = "unix:path=/run/dbus/system_bus_socket"
+			addresses[1] = FallbackSystemBusAddress
 		} else {
 			addresses[1] = addr
 		}