jochen
c42cd285e2
Replaces the AUR greenclip (declared absent) with the official clipmenu, started once from the session's xinitrc slot, its menu the launcher's dmenu command bound as an i3 drop-in, its history in the runtime directory. Go tools read and change clipmenu's own store under its lock.
424 lines
13 KiB
Go
424 lines
13 KiB
Go
// The operator's graphical session, as a tool the node's runtime runs finds it (novox/hq ADR 0208).
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//
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// The runtime is a system service running as the operator account (ADR 0175): it has the account's
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// uid and none of the session's environment — no DISPLAY, no XAUTHORITY, no session bus. A tool that
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// draws on the screen or talks to the desktop's D-Bus must find them. It reads them from a process of
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// the account that is part of the session (the window manager first), the same thing `loginctl` and
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// a person's own shell would point at, and says where it found them.
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//
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// Long-lived programs a tool starts go to the account's own service manager through `systemd-run
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// --user`, never as children of the tool: the runtime's unit is a cgroup the service manager empties
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// whenever the runtime restarts, and a compositor or a clipboard owner started from inside it would
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// die with it.
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//
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// This file is the same in every desktop module that carries it; it moves into the Go SDK once a
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// second consumer outside the desktop wants it.
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package main
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import (
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"bytes"
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"errors"
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"fmt"
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"os"
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"os/exec"
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"path/filepath"
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"sort"
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"strconv"
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"strings"
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"syscall"
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"time"
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)
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// Where the session is looked for. Variables so a test can point them at a fake tree.
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var (
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procRoot = "/proc"
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runUserDir = "/run/user"
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x11Sockets = "/tmp/.X11-unix"
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)
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// sessionHolders are the processes whose environment is the session's, best first: the window
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// manager is the session, the rest are its children. Anything else carrying DISPLAY ranks after them.
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var sessionHolders = []string{"i3", "sway", "i3bar", "picom", "xss-lock", "dunst", "clipmenud", "xterm"}
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// sessionKeys are the variables a session carries that a tool hands on to what it runs.
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var sessionKeys = []string{"DISPLAY", "XAUTHORITY", "WAYLAND_DISPLAY", "DBUS_SESSION_BUS_ADDRESS",
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"XDG_RUNTIME_DIR", "XDG_SESSION_ID", "I3SOCK"}
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// Session is what a tool needs to reach the operator's desktop.
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type Session struct {
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UID int `json:"uid"`
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Display string `json:"display,omitempty"`
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XAuthority string `json:"xauthority,omitempty"`
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Wayland string `json:"wayland_display,omitempty"`
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Bus string `json:"bus,omitempty"`
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RuntimeDir string `json:"runtime_dir,omitempty"`
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SessionID string `json:"session_id,omitempty"`
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I3Sock string `json:"i3sock,omitempty"`
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// From says where the values were found: the tool's own environment, a process, or the socket.
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From string `json:"from"`
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}
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// ErrNoSession is answered by a tool that needs the desktop when nobody is logged in to it.
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var ErrNoSession = errors.New("no graphical session")
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// ErrTimedOut is what run answers for a command ended because it ran past its time.
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var ErrTimedOut = errors.New("timed out")
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// ErrNoBus is answered by a tool that needs the session bus when the account has none.
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var ErrNoBus = errors.New("no session bus")
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// operatorHome is the account's home: what the runtime was told, else the process's own.
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func operatorHome() string {
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if h := strings.TrimSpace(os.Getenv("MESH_OPERATOR_HOME")); h != "" {
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return h
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}
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h, _ := os.UserHomeDir()
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return h
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}
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// findSession finds the graphical session of the account this tool runs as, or answers
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// ErrNoSession with what it looked at.
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func findSession() (Session, error) {
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s := findEnvironment()
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if s.Display == "" && s.Wayland == "" {
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return s, fmt.Errorf("%w for uid %d on this machine: no process of the account carries DISPLAY "+
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"or WAYLAND_DISPLAY, and no X server socket in %s has an authority file to go with it. "+
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"Is anyone logged in to the desktop?", ErrNoSession, s.UID, x11Sockets)
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}
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return s, nil
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}
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// findBus finds the account's session bus, which a logged-in account has whether or not a desktop
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// is running.
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func findBus() (Session, error) {
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s := findEnvironment()
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if s.Bus == "" {
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return s, fmt.Errorf("%w for uid %d: DBUS_SESSION_BUS_ADDRESS is not set and %s does not exist "+
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"(the account is not logged in)", ErrNoBus, s.UID, filepath.Join(runUserDir, strconv.Itoa(s.UID), "bus"))
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}
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return s, nil
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}
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func findEnvironment() Session {
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uid := os.Getuid()
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s := Session{UID: uid}
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own := map[string]string{}
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for _, k := range sessionKeys {
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own[k] = os.Getenv(k)
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}
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if own["DISPLAY"] != "" || own["WAYLAND_DISPLAY"] != "" {
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s.fill(own)
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s.From = "the tool's own environment"
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} else if pid, comm, env, ok := sessionProcess(uid); ok {
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s.fill(env)
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s.From = fmt.Sprintf("process %s (pid %d)", comm, pid)
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} else if display, ok := lonelyX11Socket(); ok {
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if a := filepath.Join(operatorHome(), ".Xauthority"); exists(a) {
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s.Display, s.XAuthority = display, a
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s.From = "the X server socket and the account's ~/.Xauthority"
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}
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s.fill(own)
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} else {
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s.fill(own)
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s.From = "nothing: no session found"
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}
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// The bus and the runtime directory are the account's, whether or not the process named them.
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runtime := filepath.Join(runUserDir, strconv.Itoa(uid))
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if s.RuntimeDir == "" && exists(runtime) {
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s.RuntimeDir = runtime
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}
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if s.Bus == "" && s.RuntimeDir != "" && exists(filepath.Join(s.RuntimeDir, "bus")) {
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s.Bus = "unix:path=" + filepath.Join(s.RuntimeDir, "bus")
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}
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return s
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}
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func (s *Session) fill(env map[string]string) {
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set := func(dst *string, key string) {
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if *dst == "" {
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*dst = env[key]
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}
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}
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set(&s.Display, "DISPLAY")
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set(&s.XAuthority, "XAUTHORITY")
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set(&s.Wayland, "WAYLAND_DISPLAY")
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set(&s.Bus, "DBUS_SESSION_BUS_ADDRESS")
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set(&s.RuntimeDir, "XDG_RUNTIME_DIR")
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set(&s.SessionID, "XDG_SESSION_ID")
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set(&s.I3Sock, "I3SOCK")
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}
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// sessionProcess is the best process of this uid whose environment names a display.
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func sessionProcess(uid int) (int, string, map[string]string, bool) {
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entries, err := os.ReadDir(procRoot)
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if err != nil {
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return 0, "", nil, false
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}
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type candidate struct {
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pid int
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comm string
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env map[string]string
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rank int
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}
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var found []candidate
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for _, e := range entries {
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pid, err := strconv.Atoi(e.Name())
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if err != nil {
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continue
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}
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dir := filepath.Join(procRoot, e.Name())
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if owner, ok := ownerOf(dir); !ok || owner != uid {
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continue
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}
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raw, err := os.ReadFile(filepath.Join(dir, "environ"))
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if err != nil {
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continue
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}
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env := parseEnviron(raw)
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if env["DISPLAY"] == "" && env["WAYLAND_DISPLAY"] == "" {
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continue
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}
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comm := readTrimmed(filepath.Join(dir, "comm"))
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rank := len(sessionHolders)
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for i, h := range sessionHolders {
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if h == comm {
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rank = i
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break
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}
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}
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found = append(found, candidate{pid, comm, env, rank})
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}
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if len(found) == 0 {
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return 0, "", nil, false
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}
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sort.Slice(found, func(i, j int) bool {
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if found[i].rank != found[j].rank {
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return found[i].rank < found[j].rank
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}
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return found[i].pid > found[j].pid // the newer of two equals
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})
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best := found[0]
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return best.pid, best.comm, best.env, true
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}
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func parseEnviron(raw []byte) map[string]string {
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env := map[string]string{}
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for _, kv := range bytes.Split(raw, []byte{0}) {
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if i := bytes.IndexByte(kv, '='); i > 0 {
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env[string(kv[:i])] = string(kv[i+1:])
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}
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}
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return env
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}
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func ownerOf(path string) (int, bool) {
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info, err := os.Stat(path)
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if err != nil {
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return 0, false
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}
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st, ok := info.Sys().(*syscall.Stat_t)
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if !ok {
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return 0, false
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}
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return int(st.Uid), true
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}
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// lonelyX11Socket is the display of the one X server socket there is, when there is exactly one.
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func lonelyX11Socket() (string, bool) {
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entries, err := os.ReadDir(x11Sockets)
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if err != nil {
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return "", false
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}
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var displays []string
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for _, e := range entries {
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if n := strings.TrimPrefix(e.Name(), "X"); n != e.Name() {
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if _, err := strconv.Atoi(n); err == nil {
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displays = append(displays, ":"+n)
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}
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}
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}
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if len(displays) != 1 {
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return "", false
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}
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return displays[0], true
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}
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func readTrimmed(path string) string {
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b, err := os.ReadFile(path)
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if err != nil {
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return ""
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}
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return strings.TrimSpace(string(b))
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}
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func exists(path string) bool {
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_, err := os.Stat(path)
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return err == nil
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}
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// Env is this process's environment with the session's variables in place of its own.
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func (s Session) Env() []string {
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drop := map[string]bool{}
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for _, k := range sessionKeys {
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drop[k] = true
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}
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var env []string
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for _, kv := range os.Environ() {
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if i := strings.IndexByte(kv, '='); i > 0 && drop[kv[:i]] {
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continue
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}
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env = append(env, kv)
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}
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add := func(k, v string) {
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if v != "" {
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env = append(env, k+"="+v)
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}
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}
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add("DISPLAY", s.Display)
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add("XAUTHORITY", s.XAuthority)
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add("WAYLAND_DISPLAY", s.Wayland)
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add("DBUS_SESSION_BUS_ADDRESS", s.Bus)
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add("XDG_RUNTIME_DIR", s.RuntimeDir)
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add("XDG_SESSION_ID", s.SessionID)
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add("I3SOCK", s.I3Sock)
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return env
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}
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// mostOutput bounds what a command may answer with, per stream.
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const mostOutput = 256 << 10
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// Result is what a command did.
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type Result struct {
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Stdout string `json:"stdout"`
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Stderr string `json:"stderr,omitempty"`
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Code int `json:"code"`
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Truncated bool `json:"truncated,omitempty"`
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}
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// run runs a command in the session's environment, its input given, ended with everything it
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// started after timeout. A command that is not installed is an error naming it; one that exits
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// non-zero is a Result with its code, for the caller to judge.
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func (s Session) run(timeout time.Duration, stdin string, name string, args ...string) (Result, error) {
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path, err := exec.LookPath(name)
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if err != nil {
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return Result{}, fmt.Errorf("%s is not installed on this machine", name)
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}
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cmd := exec.Command(path, args...)
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cmd.Env = s.Env()
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if home := operatorHome(); exists(home) {
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cmd.Dir = home
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}
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if stdin != "" {
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cmd.Stdin = strings.NewReader(stdin)
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}
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var out, errOut capped
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cmd.Stdout, cmd.Stderr = &out, &errOut
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cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
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if err := cmd.Start(); err != nil {
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return Result{}, fmt.Errorf("%s: %w", name, err)
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}
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done := make(chan error, 1)
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go func() { done <- cmd.Wait() }()
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select {
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case err = <-done:
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case <-time.After(timeout):
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_ = syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
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<-done
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return Result{Stdout: out.String(), Stderr: errOut.String()},
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fmt.Errorf("%s did not finish within %s and was ended: %w", name, timeout, ErrTimedOut)
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}
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r := Result{Stdout: out.String(), Stderr: errOut.String(), Truncated: out.cut || errOut.cut}
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var exit *exec.ExitError
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if errors.As(err, &exit) {
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r.Code = exit.ExitCode()
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} else if err != nil {
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return r, fmt.Errorf("%s: %w", name, err)
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}
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return r, nil
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}
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// detach starts a long-lived program under the account's own service manager, as a transient unit
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// that carries the session's display, so it outlives the runtime that asked for it. A unit already
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// running under the same name is stopped first, so a fixed name means "at most one".
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func (s Session) detach(unit string, args ...string) error {
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if s.RuntimeDir == "" {
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return fmt.Errorf("%w: the account's runtime directory is missing, so its service manager "+
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"cannot be reached", ErrNoBus)
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}
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_, _ = s.run(5*time.Second, "", "systemctl", "--user", "stop", unit+".service")
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call := []string{"--user", "--collect", "--quiet", "--unit=" + unit}
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for _, kv := range [][2]string{{"DISPLAY", s.Display}, {"XAUTHORITY", s.XAuthority},
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{"WAYLAND_DISPLAY", s.Wayland}, {"XDG_SESSION_ID", s.SessionID}, {"I3SOCK", s.I3Sock}} {
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if kv[1] != "" {
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call = append(call, "--setenv="+kv[0]+"="+kv[1])
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}
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}
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call = append(call, "--")
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call = append(call, args...)
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r, err := s.run(10*time.Second, "", "systemd-run", call...)
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if err != nil {
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return err
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}
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if r.Code != 0 {
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return fmt.Errorf("systemd-run %s: %s", unit, strings.TrimSpace(r.Stderr))
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}
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return nil
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}
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// uniqueUnit is a transient unit name that will not collide with an earlier one.
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func uniqueUnit(prefix string) string {
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return fmt.Sprintf("%s-%d", prefix, time.Now().UnixNano())
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}
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type capped struct {
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bytes.Buffer
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cut bool
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}
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func (c *capped) Write(p []byte) (int, error) {
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if room := mostOutput - c.Len(); room < len(p) {
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if room > 0 {
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c.Buffer.Write(p[:room])
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}
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c.cut = true
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return len(p), nil
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}
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return c.Buffer.Write(p)
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}
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// processesOf are the pids of this uid's processes whose command name is comm, oldest first.
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func processesOf(comm string) []int {
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entries, err := os.ReadDir(procRoot)
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if err != nil {
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return nil
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}
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uid := os.Getuid()
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var pids []int
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for _, e := range entries {
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pid, err := strconv.Atoi(e.Name())
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if err != nil {
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continue
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}
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dir := filepath.Join(procRoot, e.Name())
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if owner, ok := ownerOf(dir); !ok || owner != uid {
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continue
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}
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if readTrimmed(filepath.Join(dir, "comm")) == comm {
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pids = append(pids, pid)
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}
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}
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sort.Ints(pids)
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return pids
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}
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// signalAll sends sig to every process of this uid named comm, and answers the pids it reached.
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func signalAll(comm string, sig syscall.Signal) []int {
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var reached []int
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for _, pid := range processesOf(comm) {
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if syscall.Kill(pid, sig) == nil {
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reached = append(reached, pid)
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}
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}
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return reached
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}
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