fix(xray): bound the xray version probe with a timeout

backend/xray/core.go

@@ -91,12 +91,21 @@ func (c *Core) GenerateConfigFile(config []byte) error {
 	return err
 }
 
+var versionProbeTimeout = 30 * time.Second
+
 func (c *Core) refreshVersion() (string, error) {
-	cmd := exec.Command(c.executablePath, "version")
+	ctx, cancel := context.WithTimeout(context.Background(), versionProbeTimeout)
+	defer cancel()
+
+	cmd := exec.CommandContext(ctx, c.executablePath, "version")
+	cmd.WaitDelay = time.Second
 	var out bytes.Buffer
 	cmd.Stdout = &out
 	err := cmd.Run()
-	if err != nil {
+	if ctx.Err() != nil {
+		return "", fmt.Errorf("xray version probe did not finish within %s: %w", versionProbeTimeout, ctx.Err())
+	}
+	if err != nil && !errors.Is(err, exec.ErrWaitDelay) {
 		return "", err
 	}
 

backend/xray/core_version_probe_unix_test.go

@@ -0,0 +1,72 @@
+//go:build !windows
+
+package xray
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+func writeVersionStub(t *testing.T, body string) string {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "xray")
+	if err := os.WriteFile(path, []byte("#!/bin/sh\n"+body+"\n"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	return path
+}
+
+func newCoreWithin(t *testing.T, path string, limit time.Duration) error {
+	t.Helper()
+	done := make(chan error, 1)
+	go func() {
+		_, err := NewXRayCore(path, t.TempDir(), t.TempDir(), 16, 16)
+		done <- err
+	}()
+	select {
+	case err := <-done:
+		return err
+	case <-time.After(limit):
+		t.Fatalf("NewXRayCore did not return within %s while the version probe hung", limit)
+		return nil
+	}
+}
+
+func TestVersionProbeOfAHungBinaryIsBounded(t *testing.T) {
+	previous := versionProbeTimeout
+	versionProbeTimeout = 500 * time.Millisecond
+	t.Cleanup(func() { versionProbeTimeout = previous })
+
+	err := newCoreWithin(t, writeVersionStub(t, "exec sleep 30"), 5*time.Second)
+	if err == nil {
+		t.Fatal("expected an error from a version probe that never answered")
+	}
+}
+
+func TestVersionProbeSurvivesABinaryThatForksAndHoldsStdout(t *testing.T) {
+	err := newCoreWithin(t, writeVersionStub(t, "echo 'Xray 26.10.31 (Xray, Penetrates Everything.)'\nsleep 30 &\nexit 0"), 15*time.Second)
+	if err != nil {
+		t.Fatalf("expected the printed version to be accepted, got %v", err)
+	}
+}
+
+func TestVersionProbeOfAWorkingBinaryStillParses(t *testing.T) {
+	path := writeVersionStub(t, "echo 'Xray 26.10.31 (Xray, Penetrates Everything.)'")
+	core, err := NewXRayCore(path, t.TempDir(), t.TempDir(), 16, 16)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if core.Version() != "26.10.31" {
+		t.Fatalf("version = %q", core.Version())
+	}
+}
+
+func TestVersionProbeWaitsForASlowButHealthyBinary(t *testing.T) {
+	t.Parallel()
+	err := newCoreWithin(t, writeVersionStub(t, "sleep 11\necho 'Xray 26.10.31 (Xray, Penetrates Everything.)'"), 40*time.Second)
+	if err != nil {
+		t.Fatalf("a version probe that answers after 11 s must still be accepted, got %v", err)
+	}
+}