elevate: move service/token into proper module

1 files changed, 60 insertions, 0 deletions

diff --git a/elevate/privileges.go b/elevate/privileges.go
new file mode 100644
index 00000000..a02d8a5d
--- /dev/null
+++ b/elevate/privileges.go
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package elevate
+
+import (
+	"errors"
+	"runtime"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+func DropAllPrivileges(retainDriverLoading bool) error {
+	processHandle, err := windows.GetCurrentProcess()
+	if err != nil {
+		return err
+	}
+	var luid windows.LUID
+	if retainDriverLoading {
+		err = windows.LookupPrivilegeValue(nil, windows.StringToUTF16Ptr("SeLoadDriverPrivilege"), &luid)
+		if err != nil {
+			return err
+		}
+	}
+	var processToken windows.Token
+	err = windows.OpenProcessToken(processHandle, windows.TOKEN_READ|windows.TOKEN_WRITE, &processToken)
+	if err != nil {
+		return err
+	}
+	defer processToken.Close()
+
+	var bufferSizeRequired uint32
+	windows.GetTokenInformation(processToken, windows.TokenPrivileges, nil, 0, &bufferSizeRequired)
+	if bufferSizeRequired == 0 || bufferSizeRequired < uint32(unsafe.Sizeof(windows.Tokenprivileges{}.PrivilegeCount)) {
+		return errors.New("GetTokenInformation failed to provide a buffer size")
+	}
+	buffer := make([]byte, bufferSizeRequired)
+	var bytesWritten uint32
+	err = windows.GetTokenInformation(processToken, windows.TokenPrivileges, &buffer[0], uint32(len(buffer)), &bytesWritten)
+	if err != nil {
+		return err
+	}
+	if bytesWritten != bufferSizeRequired {
+		return errors.New("GetTokenInformation returned incomplete data")
+	}
+	tokenPrivileges := (*windows.Tokenprivileges)(unsafe.Pointer(&buffer[0]))
+	for i := uint32(0); i < tokenPrivileges.PrivilegeCount; i++ {
+		item := (*windows.LUIDAndAttributes)(unsafe.Pointer(uintptr(unsafe.Pointer(&tokenPrivileges.Privileges[0])) + unsafe.Sizeof(tokenPrivileges.Privileges[0])*uintptr(i)))
+		if retainDriverLoading && item.Luid == luid {
+			continue
+		}
+		item.Attributes = windows.SE_PRIVILEGE_REMOVED
+	}
+	err = windows.AdjustTokenPrivileges(processToken, false, tokenPrivileges, 0, nil, nil)
+	runtime.KeepAlive(buffer)
+	return err
+}