os/user: test that Current does not depend on netapi32.dll

Updates #21867.

Change-Id: I1eb923ef66aa0f338bfa0d683159edc1d8ae2a6c
Reviewed-on: https://go-review.googlesource.com/c/go/+/604415
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/internal/syscall/windows/syscall_windows.go

@@ -500,3 +500,5 @@ func QueryPerformanceCounter() int64 // Implemented in runtime package.
 //
 //go:linkname QueryPerformanceFrequency
 func QueryPerformanceFrequency() int64 // Implemented in runtime package.
+
+//sys   GetModuleHandle(modulename *uint16) (handle syscall.Handle, err error) = kernel32.GetModuleHandleW

src/internal/syscall/windows/zsyscall_windows.go

@@ -69,6 +69,7 @@ var (
 	procGetFileInformationByHandleEx      = modkernel32.NewProc("GetFileInformationByHandleEx")
 	procGetFinalPathNameByHandleW         = modkernel32.NewProc("GetFinalPathNameByHandleW")
 	procGetModuleFileNameW                = modkernel32.NewProc("GetModuleFileNameW")
+	procGetModuleHandleW                  = modkernel32.NewProc("GetModuleHandleW")
 	procGetTempPath2W                     = modkernel32.NewProc("GetTempPath2W")
 	procGetVolumeInformationByHandleW     = modkernel32.NewProc("GetVolumeInformationByHandleW")
 	procGetVolumeNameForVolumeMountPointW = modkernel32.NewProc("GetVolumeNameForVolumeMountPointW")
@@ -287,6 +288,15 @@ func GetModuleFileName(module syscall.Handle, fn *uint16, len uint32) (n uint32,
 	return
 }
 
+func GetModuleHandle(modulename *uint16) (handle syscall.Handle, err error) {
+	r0, _, e1 := syscall.Syscall(procGetModuleHandleW.Addr(), 1, uintptr(unsafe.Pointer(modulename)), 0, 0)
+	handle = syscall.Handle(r0)
+	if handle == 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
 func GetTempPath2(buflen uint32, buf *uint16) (n uint32, err error) {
 	r0, _, e1 := syscall.Syscall(procGetTempPath2W.Addr(), 2, uintptr(buflen), uintptr(unsafe.Pointer(buf)), 0)
 	n = uint32(r0)

src/os/user/user_windows_test.go

@@ -8,7 +8,11 @@ import (
 	"crypto/rand"
 	"encoding/base64"
 	"errors"
+	"fmt"
 	"internal/syscall/windows"
+	"internal/testenv"
+	"os"
+	"os/exec"
 	"runtime"
 	"strconv"
 	"syscall"
@@ -143,3 +147,37 @@ func TestImpersonated(t *testing.T) {
 	}
 	compare(t, want, got)
 }
+
+func TestCurrentNetapi32(t *testing.T) {
+	if os.Getenv("GO_WANT_HELPER_PROCESS") == "1" {
+		// Test that Current does not load netapi32.dll.
+		// First call Current.
+		Current()
+
+		// Then check if netapi32.dll is loaded.
+		netapi32, err := syscall.UTF16PtrFromString("netapi32.dll")
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "error: %s\n", err.Error())
+			os.Exit(9)
+			return
+		}
+		mod, _ := windows.GetModuleHandle(netapi32)
+		if mod != 0 {
+			fmt.Fprintf(os.Stderr, "netapi32.dll is loaded\n")
+			os.Exit(9)
+			return
+		}
+		os.Exit(0)
+		return
+	}
+	exe, err := os.Executable()
+	if err != nil {
+		t.Fatal(err)
+	}
+	cmd := testenv.CleanCmdEnv(exec.Command(exe, "-test.run=^TestCurrentNetapi32$"))
+	cmd.Env = append(cmd.Env, "GO_WANT_HELPER_PROCESS=1")
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("%v\n%s", err, out)
+	}
+}