wintun: Introduce new package for obscuring Windows bits

tun/wintun/guid/guid_windows.go

@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package guid
+
+import (
+	"fmt"
+	"syscall"
+
+	"golang.org/x/sys/windows"
+)
+
+//sys	clsidFromString(lpsz *uint16, pclsid *windows.GUID) (hr int32) = ole32.CLSIDFromString
+
+//
+// FromString parses "{XXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}" string to GUID.
+//
+func FromString(str string) (*windows.GUID, error) {
+	strUTF16, err := syscall.UTF16PtrFromString(str)
+	if err != nil {
+		return nil, err
+	}
+
+	guid := &windows.GUID{}
+
+	hr := clsidFromString(strUTF16, guid)
+	if hr < 0 {
+		return nil, syscall.Errno(hr)
+	}
+
+	return guid, nil
+}
+
+//
+// ToString function converts GUID to string
+// "{XXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}".
+//
+// The resulting string is uppercase.
+//
+func ToString(guid *windows.GUID) string {
+	return fmt.Sprintf("{%06X-%04X-%04X-%04X-%012X}", guid.Data1, guid.Data2, guid.Data3, guid.Data4[:2], guid.Data4[2:])
+}

tun/wintun/guid/mksyscall.go

@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package guid
+
+//go:generate go run $GOROOT/src/syscall/mksyscall_windows.go -output zguid_windows.go guid_windows.go

tun/wintun/guid/zguid_windows.go

@@ -0,0 +1,49 @@
+// Code generated by 'go generate'; DO NOT EDIT.
+
+package guid
+
+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)
+)
+
+// errnoErr returns common boxed Errno values, to prevent
+// allocations at runtime.
+func errnoErr(e syscall.Errno) error {
+	switch e {
+	case 0:
+		return nil
+	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 (
+	modole32 = windows.NewLazySystemDLL("ole32.dll")
+
+	procCLSIDFromString = modole32.NewProc("CLSIDFromString")
+)
+
+func clsidFromString(lpsz *uint16, pclsid *windows.GUID) (hr int32) {
+	r0, _, _ := syscall.Syscall(procCLSIDFromString.Addr(), 2, uintptr(unsafe.Pointer(lpsz)), uintptr(unsafe.Pointer(pclsid)), 0)
+	hr = int32(r0)
+	return
+}