main: forbid wow64 executions

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

3 files changed, 38 insertions, 5 deletions

diff --git a/README.md b/README.md
index 25265535..d0cb04a8 100644
--- a/README.md
+++ b/README.md
@@ -32,7 +32,7 @@ $ make
 
 ### Running
 
-After you've built the application, run `amd64\wireguard.exe` to install the manager service and show the UI.
+After you've built the application, run `amd64\wireguard.exe` or `x86\wireguard.exe` to install the manager service and show the UI.
 
 ```
 C:\Projects\wireguard-windows> amd64\wireguard.exe
diff --git a/main.go b/main.go
index c9941ab9..8aef8724 100644
--- a/main.go
+++ b/main.go
@@ -28,9 +28,11 @@ var flags = [...]string{
 }
 
 //sys messageBoxEx(hwnd windows.Handle, text *uint16, title *uint16, typ uint, languageId uint16) = user32.MessageBoxExW
+//sys isWow64Process(handle windows.Handle, isWow64 *bool) (err error) = kernel32.IsWow64Process
 
 func fatal(v ...interface{}) {
 	messageBoxEx(0, windows.StringToUTF16Ptr(fmt.Sprint(v...)), windows.StringToUTF16Ptr("Error"), 0x00000010, 0)
+	os.Exit(1)
 }
 
 func usage() {
@@ -43,6 +45,21 @@ func usage() {
 	os.Exit(1)
 }
 
+func checkForWow64() {
+	var b bool
+	p, err := windows.GetCurrentProcess()
+	if err != nil {
+		fatal("Unable to determine current process handle: ", err)
+	}
+	err = isWow64Process(p, &b)
+	if err != nil {
+		fatal("Unable to determine whether the process is running under WOW64: ", err)
+	}
+	if b {
+		fatal("You must use the 64-bit version of WireGuard on this computer.")
+	}
+}
+
 //sys shellExecute(hwnd windows.Handle, verb *uint16, file *uint16, args *uint16, cwd *uint16, showCmd int) (err error) = shell32.ShellExecuteW
 func execElevatedManagerServiceInstaller() error {
 	path, err := os.Executable()
@@ -66,6 +83,8 @@ func pipeFromHandleArgument(handleStr string) (*os.File, error) {
 }
 
 func main() {
+	checkForWow64()
+
 	if len(os.Args) <= 1 {
 		if ui.RaiseUI() {
 			return
diff --git a/zsyscall_windows.go b/zsyscall_windows.go
index d78d0ea3..dc9f9ffc 100644
--- a/zsyscall_windows.go
+++ b/zsyscall_windows.go
@@ -37,11 +37,13 @@ func errnoErr(e syscall.Errno) error {
 }
 
 var (
-	moduser32  = windows.NewLazySystemDLL("user32.dll")
-	modshell32 = windows.NewLazySystemDLL("shell32.dll")
+	moduser32   = windows.NewLazySystemDLL("user32.dll")
+	modkernel32 = windows.NewLazySystemDLL("kernel32.dll")
+	modshell32  = windows.NewLazySystemDLL("shell32.dll")
 
-	procMessageBoxExW = moduser32.NewProc("MessageBoxExW")
-	procShellExecuteW = modshell32.NewProc("ShellExecuteW")
+	procMessageBoxExW  = moduser32.NewProc("MessageBoxExW")
+	procIsWow64Process = modkernel32.NewProc("IsWow64Process")
+	procShellExecuteW  = modshell32.NewProc("ShellExecuteW")
 )
 
 func messageBoxEx(hwnd windows.Handle, text *uint16, title *uint16, typ uint, languageId uint16) {
@@ -49,6 +51,18 @@ func messageBoxEx(hwnd windows.Handle, text *uint16, title *uint16, typ uint, la
 	return
 }
 
+func isWow64Process(handle windows.Handle, isWow64 *bool) (err error) {
+	r1, _, e1 := syscall.Syscall(procIsWow64Process.Addr(), 2, uintptr(handle), uintptr(unsafe.Pointer(isWow64)), 0)
+	if r1 == 0 {
+		if e1 != 0 {
+			err = errnoErr(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}
+
 func shellExecute(hwnd windows.Handle, verb *uint16, file *uint16, args *uint16, cwd *uint16, showCmd int) (err error) {
 	r1, _, e1 := syscall.Syscall6(procShellExecuteW.Addr(), 6, uintptr(hwnd), uintptr(unsafe.Pointer(verb)), uintptr(unsafe.Pointer(file)), uintptr(unsafe.Pointer(args)), uintptr(unsafe.Pointer(cwd)), uintptr(showCmd))
 	if r1 == 0 {