From 9b6a308958d4d7420c066e3f69a0afecbfdac10c Mon Sep 17 00:00:00 2001
From: Cuong Manh Le <cuong@windscribe.com>
Date: Thu, 21 Nov 2024 20:24:46 +0700
Subject: [PATCH] cmd/cli: get AD domain using Windows API

---
 cmd/cli/ad_windows.go      | 18 +++++++++++++-----
 cmd/cli/ad_windows_test.go | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 5 deletions(-)
 create mode 100644 cmd/cli/ad_windows_test.go

diff --git a/cmd/cli/ad_windows.go b/cmd/cli/ad_windows.go
index d7374d0..316414d 100644
--- a/cmd/cli/ad_windows.go
+++ b/cmd/cli/ad_windows.go
@@ -1,8 +1,11 @@
 package cli
 
 import (
-	"fmt"
 	"strings"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
 
 	"github.com/Control-D-Inc/ctrld"
 )
@@ -40,10 +43,15 @@ func addExtraSplitDnsRule(cfg *ctrld.Config) bool {
 
 // getActiveDirectoryDomain returns AD domain name of this computer.
 func getActiveDirectoryDomain() (string, error) {
-	cmd := "$obj = Get-WmiObject Win32_ComputerSystem; if ($obj.PartOfDomain) { $obj.Domain }"
-	output, err := powershell(cmd)
+	var domain *uint16
+	var status uint32
+	err := syscall.NetGetJoinInformation(nil, &domain, &status)
 	if err != nil {
-		return "", fmt.Errorf("failed to get domain name: %w, output:\n\n%s", err, string(output))
+		return "", err
 	}
-	return string(output), nil
+	defer syscall.NetApiBufferFree((*byte)(unsafe.Pointer(domain)))
+	if status == syscall.NetSetupDomainName {
+		return windows.UTF16PtrToString(domain), nil
+	}
+	return "", nil
 }
diff --git a/cmd/cli/ad_windows_test.go b/cmd/cli/ad_windows_test.go
new file mode 100644
index 0000000..392abbd
--- /dev/null
+++ b/cmd/cli/ad_windows_test.go
@@ -0,0 +1,36 @@
+package cli
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+func Test_getActiveDirectoryDomain(t *testing.T) {
+	start := time.Now()
+	domain, err := getActiveDirectoryDomain()
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("Using Windows API takes: %d", time.Since(start).Milliseconds())
+
+	start = time.Now()
+	domainPowershell, err := getActiveDirectoryDomainPowershell()
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("Using Powershell takes: %d", time.Since(start).Milliseconds())
+
+	if domain != domainPowershell {
+		t.Fatalf("result mismatch, want: %v, got: %v", domainPowershell, domain)
+	}
+}
+
+func getActiveDirectoryDomainPowershell() (string, error) {
+	cmd := "$obj = Get-WmiObject Win32_ComputerSystem; if ($obj.PartOfDomain) { $obj.Domain }"
+	output, err := powershell(cmd)
+	if err != nil {
+		return "", fmt.Errorf("failed to get domain name: %w, output:\n\n%s", err, string(output))
+	}
+	return string(output), nil
+}