util/winutil/winenv: add package for current Windows environment details

Package winenv provides information about the current Windows environment.
This includes details such as whether the device is a server or workstation,
and if it is AD domain-joined, MDM-registered, or neither.

Updates tailscale/corp#18342

Signed-off-by: Nick Khyl <nickk@tailscale.com>

util/winutil/winenv/zsyscall_windows.go

@@ -0,0 +1,77 @@
+// Code generated by 'go generate'; DO NOT EDIT.
+
+package winenv
+
+import (
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+var _ unsafe.Pointer
+
+// Do the interface allocations only once for common
+// Errno values.
+const (
+	errnoERROR_IO_PENDING = 997
+)
+
+var (
+	errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
+	errERROR_EINVAL     error = syscall.EINVAL
+)
+
+// errnoErr returns common boxed Errno values, to prevent
+// allocations at runtime.
+func errnoErr(e syscall.Errno) error {
+	switch e {
+	case 0:
+		return errERROR_EINVAL
+	case errnoERROR_IO_PENDING:
+		return errERROR_IO_PENDING
+	}
+	// TODO: add more here, after collecting data on the common
+	// error values see on Windows. (perhaps when running
+	// all.bat?)
+	return e
+}
+
+var (
+	modMDMRegistration = windows.NewLazySystemDLL("MDMRegistration.dll")
+	modkernel32        = windows.NewLazySystemDLL("kernel32.dll")
+
+	procIsDeviceRegisteredWithManagement = modMDMRegistration.NewProc("IsDeviceRegisteredWithManagement")
+	procVerSetConditionMask              = modkernel32.NewProc("VerSetConditionMask")
+	procVerifyVersionInfoW               = modkernel32.NewProc("VerifyVersionInfoW")
+)
+
+func isDeviceRegisteredWithManagement(isMDMRegistered *bool, upnBufLen uint32, upnBuf *uint16) (hr int32, err error) {
+	err = procIsDeviceRegisteredWithManagement.Find()
+	if err != nil {
+		return
+	}
+	var _p0 uint32
+	if *isMDMRegistered {
+		_p0 = 1
+	}
+	r0, _, e1 := syscall.Syscall(procIsDeviceRegisteredWithManagement.Addr(), 3, uintptr(unsafe.Pointer(&_p0)), uintptr(upnBufLen), uintptr(unsafe.Pointer(upnBuf)))
+	*isMDMRegistered = _p0 != 0
+	hr = int32(r0)
+	if hr == 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
+func verSetConditionMask(condMask verCondMask, typ verTypeMask, cond verCond) (res verCondMask) {
+	r0, _, _ := syscall.Syscall(procVerSetConditionMask.Addr(), 3, uintptr(condMask), uintptr(typ), uintptr(cond))
+	res = verCondMask(r0)
+	return
+}
+
+func verifyVersionInfo(verInfo *osVersionInfoEx, typ verTypeMask, cond verCondMask) (res bool) {
+	r0, _, _ := syscall.Syscall(procVerifyVersionInfoW.Addr(), 3, uintptr(unsafe.Pointer(verInfo)), uintptr(typ), uintptr(cond))
+	res = r0 != 0
+	return
+}