1 files changed, 70 insertions, 0 deletions
diff --git a/services/tokens.go b/services/tokens.go
new file mode 100644
index 00000000..aa6f2c4a
--- /dev/null
+++ b/services/tokens.go
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package services
+
+import (
+	"errors"
+	"runtime"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+func TokenIsMemberOfBuiltInAdministrator(token windows.Token) bool {
+	adminSid, err := windows.CreateWellKnownSid(windows.WinBuiltinAdministratorsSid)
+	if err != nil {
+		return false
+	}
+	gs, err := token.GetTokenGroups()
+	if err != nil {
+		return false
+	}
+	groups := (*[(1 << 28) - 1]windows.SIDAndAttributes)(unsafe.Pointer(&gs.Groups[0]))[:gs.GroupCount]
+	isAdmin := false
+	for _, g := range groups {
+		if (g.Attributes&windows.SE_GROUP_USE_FOR_DENY_ONLY != 0 || g.Attributes&windows.SE_GROUP_ENABLED != 0) && windows.EqualSid(g.Sid, adminSid) {
+			isAdmin = true
+			break
+		}
+	}
+	runtime.KeepAlive(gs)
+	return isAdmin
+}
+
+func DropAllPrivileges() error {
+	processHandle, err := windows.GetCurrentProcess()
+	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++ {
+		(*windows.LUIDAndAttributes)(unsafe.Pointer(uintptr(unsafe.Pointer(&tokenPrivileges.Privileges[0])) + unsafe.Sizeof(tokenPrivileges.Privileges[0])*uintptr(i))).Attributes = windows.SE_PRIVILEGE_REMOVED
+	}
+	err = windows.AdjustTokenPrivileges(processToken, false, tokenPrivileges, 0, nil, nil)
+	runtime.KeepAlive(buffer)
+	return err
+}