cmd/hsu: return hsurc id

The uid format is stable, this value is what caller has to obtain through hsu.

Closes #14.

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

internal/app/process.go

@@ -255,7 +255,7 @@ func (seal *outcome) main() {
 			// passed through to shim by hsu
 			shimEnv + "=" + strconv.Itoa(fd),
 			// interpreted by hsu
-			"HAKUREI_APP_ID=" + seal.user.identity.String(),
+			"HAKUREI_IDENTITY=" + seal.user.identity.String(),
 		}
 	}
 

internal/sys/hsu.go

@@ -17,69 +17,48 @@ import (
 
 // Hsu caches responses from cmd/hsu.
 type Hsu struct {
-	uidOnce sync.Once
-	uidCopy map[int]struct {
-		uid int
-		err error
-	}
-	uidMu sync.RWMutex
+	idOnce sync.Once
+	idErr  error
+	id     int
 }
 
 var ErrHsuAccess = errors.New("current user is not in the hsurc file")
 
 func (h *Hsu) Uid(identity int) (int, error) {
-	h.uidOnce.Do(func() {
-		h.uidCopy = make(map[int]struct {
-			uid int
-			err error
-		})
+	h.idOnce.Do(func() {
+		h.id = -1
+		hsuPath := internal.MustHsuPath()
+
+		cmd := exec.Command(hsuPath)
+		cmd.Path = hsuPath
+		cmd.Stderr = os.Stderr // pass through fatal messages
+		cmd.Env = make([]string, 0)
+		cmd.Dir = container.FHSRoot
+		var (
+			p         []byte
+			exitError *exec.ExitError
+		)
+
+		const step = "obtain uid from hsu"
+		if p, h.idErr = cmd.Output(); h.idErr == nil {
+			h.id, h.idErr = strconv.Atoi(string(p))
+			if h.idErr != nil {
+				h.idErr = &hst.AppError{Step: step, Err: h.idErr, Msg: "invalid uid string from hsu"}
+			}
+		} else if errors.As(h.idErr, &exitError) && exitError != nil && exitError.ExitCode() == 1 {
+			// hsu prints an error message in this case
+			h.idErr = &hst.AppError{Step: step, Err: ErrHsuAccess}
+		} else if os.IsNotExist(h.idErr) {
+			h.idErr = &hst.AppError{Step: step, Err: os.ErrNotExist,
+				Msg: fmt.Sprintf("the setuid helper is missing: %s", hsuPath)}
+		}
 	})
 
-	{
-		h.uidMu.RLock()
-		u, ok := h.uidCopy[identity]
-		h.uidMu.RUnlock()
-		if ok {
-			return u.uid, u.err
-		}
+	uid := -1
+	if h.id >= 0 {
+		uid = 1000000 + h.id*10000 + identity
 	}
-
-	h.uidMu.Lock()
-	defer h.uidMu.Unlock()
-
-	u := struct {
-		uid int
-		err error
-	}{}
-	defer func() { h.uidCopy[identity] = u }()
-
-	u.uid = -1
-	hsuPath := internal.MustHsuPath()
-
-	cmd := exec.Command(hsuPath)
-	cmd.Path = hsuPath
-	cmd.Stderr = os.Stderr // pass through fatal messages
-	cmd.Env = []string{"HAKUREI_APP_ID=" + strconv.Itoa(identity)}
-	cmd.Dir = container.FHSRoot
-	var (
-		p         []byte
-		exitError *exec.ExitError
-	)
-
-	const step = "obtain uid from hsu"
-	if p, u.err = cmd.Output(); u.err == nil {
-		u.uid, u.err = strconv.Atoi(string(p))
-		if u.err != nil {
-			u.err = &hst.AppError{Step: step, Err: u.err, Msg: "invalid uid string from hsu"}
-		}
-	} else if errors.As(u.err, &exitError) && exitError != nil && exitError.ExitCode() == 1 {
-		// hsu prints an error message in this case
-		u.err = &hst.AppError{Step: step, Err: ErrHsuAccess}
-	} else if os.IsNotExist(u.err) {
-		u.err = &hst.AppError{Step: step, Err: os.ErrNotExist,
-			Msg: fmt.Sprintf("the setuid helper is missing: %s", hsuPath)}
-	}
-	return u.uid, u.err
+	return uid, h.idErr
 }
 
 // MustUid calls [State.Uid] and terminates on error.