fix(auth): harden diagnostic cleanup races

tools/tht/internal/compose/process_windows_test.go

@@ -4,14 +4,37 @@ package compose
 
 import (
 	"context"
+	"errors"
+	"path/filepath"
 	"reflect"
 	"testing"
 )
 
-func TestWindowsTreeKillCommandUsesExactPIDArgumentArray(t *testing.T) {
-	command := windowsTreeKillCommand(context.Background(), 4242)
-	want := []string{"taskkill.exe", "/PID", "4242", "/T", "/F"}
+func TestWindowsTreeKillCommandUsesTrustedAbsoluteSystemPathAndExactPIDArgumentArray(t *testing.T) {
+	original := windowsSystemDirectory
+	windowsSystemDirectory = func() (string, error) { return `C:\\Windows\\System32`, nil }
+	t.Cleanup(func() { windowsSystemDirectory = original })
+
+	taskkillPath, err := systemTaskkillPath()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !filepath.IsAbs(taskkillPath) {
+		t.Fatalf("taskkill path = %q, want absolute trusted system path", taskkillPath)
+	}
+	command := windowsTreeKillCommand(context.Background(), taskkillPath, 4242)
+	want := []string{taskkillPath, "/PID", "4242", "/T", "/F"}
 	if !reflect.DeepEqual(command.Args, want) {
 		t.Fatalf("taskkill args = %#v, want %#v", command.Args, want)
 	}
 }
+
+func TestWindowsSystemTaskkillPathRejectsRelativeSystemDirectory(t *testing.T) {
+	original := windowsSystemDirectory
+	windowsSystemDirectory = func() (string, error) { return `System32`, nil }
+	t.Cleanup(func() { windowsSystemDirectory = original })
+
+	if _, err := systemTaskkillPath(); !errors.Is(err, ErrProcessReap) {
+		t.Fatalf("systemTaskkillPath() error = %v, want ErrProcessReap", err)
+	}
+}