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tailscale/util/winutil/winutil_windows.go

787 lines
23 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
package winutil
import (
"errors"
"fmt"
"log"
"math"
"os/exec"
"os/user"
"reflect"
"runtime"
"strings"
"syscall"
"time"
"unsafe"
"golang.org/x/exp/constraints"
"golang.org/x/sys/windows"
"golang.org/x/sys/windows/registry"
)
const (
regBase = `SOFTWARE\Tailscale IPN`
regPolicyBase = `SOFTWARE\Policies\Tailscale`
)
// ErrNoShell is returned when the shell process is not found.
var ErrNoShell = errors.New("no Shell process is present")
// ErrNoValue is returned when the value doesn't exist in the registry.
var ErrNoValue = registry.ErrNotExist
// GetDesktopPID searches the PID of the process that's running the
// currently active desktop. Returns ErrNoShell if the shell is not present.
// Usually the PID will be for explorer.exe.
func GetDesktopPID() (uint32, error) {
hwnd := windows.GetShellWindow()
if hwnd == 0 {
return 0, ErrNoShell
}
var pid uint32
windows.GetWindowThreadProcessId(hwnd, &pid)
if pid == 0 {
return 0, fmt.Errorf("invalid PID for HWND %v", hwnd)
}
return pid, nil
}
func getPolicyString(name string) (string, error) {
s, err := getRegStringInternal(regPolicyBase, name)
if err != nil {
// Fall back to the legacy path
return getRegString(name)
}
return s, err
}
func getPolicyStringArray(name string) ([]string, error) {
return getRegStringsInternal(regPolicyBase, name)
}
func getRegString(name string) (string, error) {
s, err := getRegStringInternal(regBase, name)
if err != nil {
return "", err
}
return s, err
}
func getPolicyInteger(name string) (uint64, error) {
i, err := getRegIntegerInternal(regPolicyBase, name)
if err != nil {
// Fall back to the legacy path
return getRegInteger(name)
}
return i, err
}
func getRegInteger(name string) (uint64, error) {
i, err := getRegIntegerInternal(regBase, name)
if err != nil {
return 0, err
}
return i, err
}
func getRegStringInternal(subKey, name string) (string, error) {
key, err := registry.OpenKey(registry.LOCAL_MACHINE, subKey, registry.READ)
if err != nil {
if err != ErrNoValue {
log.Printf("registry.OpenKey(%v): %v", subKey, err)
}
return "", err
}
defer key.Close()
val, _, err := key.GetStringValue(name)
if err != nil {
if err != ErrNoValue {
log.Printf("registry.GetStringValue(%v): %v", name, err)
}
return "", err
}
return val, nil
}
// GetRegStrings looks up a registry value in the local machine path, or returns
// the given default if it can't.
func GetRegStrings(name string, defval []string) []string {
s, err := getRegStringsInternal(regBase, name)
if err != nil {
return defval
}
return s
}
func getRegStringsInternal(subKey, name string) ([]string, error) {
key, err := registry.OpenKey(registry.LOCAL_MACHINE, subKey, registry.READ)
if err != nil {
if err != ErrNoValue {
log.Printf("registry.OpenKey(%v): %v", subKey, err)
}
return nil, err
}
defer key.Close()
val, _, err := key.GetStringsValue(name)
if err != nil {
if err != ErrNoValue {
log.Printf("registry.GetStringValue(%v): %v", name, err)
}
return nil, err
}
return val, nil
}
// SetRegStrings sets a MULTI_SZ value in the in the local machine path
// to the strings specified by values.
func SetRegStrings(name string, values []string) error {
return setRegStringsInternal(regBase, name, values)
}
func setRegStringsInternal(subKey, name string, values []string) error {
key, _, err := registry.CreateKey(registry.LOCAL_MACHINE, subKey, registry.SET_VALUE)
if err != nil {
log.Printf("registry.CreateKey(%v): %v", subKey, err)
}
defer key.Close()
return key.SetStringsValue(name, values)
}
// DeleteRegValue removes a registry value in the local machine path.
func DeleteRegValue(name string) error {
return deleteRegValueInternal(regBase, name)
}
func deleteRegValueInternal(subKey, name string) error {
key, err := registry.OpenKey(registry.LOCAL_MACHINE, subKey, registry.SET_VALUE)
if err == ErrNoValue {
return nil
}
if err != nil {
log.Printf("registry.OpenKey(%v): %v", subKey, err)
return err
}
defer key.Close()
err = key.DeleteValue(name)
if err == ErrNoValue {
err = nil
}
return err
}
func getRegIntegerInternal(subKey, name string) (uint64, error) {
key, err := registry.OpenKey(registry.LOCAL_MACHINE, subKey, registry.READ)
if err != nil {
if err != ErrNoValue {
log.Printf("registry.OpenKey(%v): %v", subKey, err)
}
return 0, err
}
defer key.Close()
val, _, err := key.GetIntegerValue(name)
if err != nil {
if err != ErrNoValue {
log.Printf("registry.GetIntegerValue(%v): %v", name, err)
}
return 0, err
}
return val, nil
}
var (
kernel32 = syscall.NewLazyDLL("kernel32.dll")
procWTSGetActiveConsoleSessionId = kernel32.NewProc("WTSGetActiveConsoleSessionId")
)
// TODO(crawshaw): replace with x/sys/windows... one day.
// https://go-review.googlesource.com/c/sys/+/331909
func WTSGetActiveConsoleSessionId() uint32 {
r1, _, _ := procWTSGetActiveConsoleSessionId.Call()
return uint32(r1)
}
func isSIDValidPrincipal(uid string) bool {
usid, err := syscall.StringToSid(uid)
if err != nil {
return false
}
_, _, accType, err := usid.LookupAccount("")
if err != nil {
return false
}
switch accType {
case syscall.SidTypeUser, syscall.SidTypeGroup, syscall.SidTypeDomain, syscall.SidTypeAlias, syscall.SidTypeWellKnownGroup, syscall.SidTypeComputer:
return true
default:
// Reject deleted users, invalid SIDs, unknown SIDs, mandatory label SIDs, etc.
return false
}
}
// EnableCurrentThreadPrivilege enables the named privilege
// in the current thread's access token. The current goroutine is also locked to
// the OS thread (runtime.LockOSThread). Callers must call the returned disable
// function when done with the privileged task.
func EnableCurrentThreadPrivilege(name string) (disable func(), err error) {
return EnableCurrentThreadPrivileges([]string{name})
}
// EnableCurrentThreadPrivileges enables the named privileges
// in the current thread's access token. The current goroutine is also locked to
// the OS thread (runtime.LockOSThread). Callers must call the returned disable
// function when done with the privileged task.
func EnableCurrentThreadPrivileges(names []string) (disable func(), err error) {
runtime.LockOSThread()
if len(names) == 0 {
// Nothing to enable; no-op isn't really an error...
return runtime.UnlockOSThread, nil
}
if err := windows.ImpersonateSelf(windows.SecurityImpersonation); err != nil {
runtime.UnlockOSThread()
return nil, err
}
disable = func() {
defer runtime.UnlockOSThread()
// If RevertToSelf fails, it's not really recoverable and we should panic.
// Failure to do so would leak the privileges we're enabling, which is a
// security issue.
if err := windows.RevertToSelf(); err != nil {
panic(fmt.Sprintf("RevertToSelf failed: %v", err))
}
}
defer func() {
if err != nil {
disable()
}
}()
var t windows.Token
err = windows.OpenThreadToken(windows.CurrentThread(),
windows.TOKEN_QUERY|windows.TOKEN_ADJUST_PRIVILEGES, false, &t)
if err != nil {
return nil, err
}
defer t.Close()
tp := newTokenPrivileges(len(names))
privs := tp.AllPrivileges()
for i := range privs {
var privStr *uint16
privStr, err = windows.UTF16PtrFromString(names[i])
if err != nil {
return nil, err
}
err = windows.LookupPrivilegeValue(nil, privStr, &privs[i].Luid)
if err != nil {
return nil, err
}
privs[i].Attributes = windows.SE_PRIVILEGE_ENABLED
}
err = windows.AdjustTokenPrivileges(t, false, tp, 0, nil, nil)
if err != nil {
return nil, err
}
return disable, nil
}
func newTokenPrivileges(numPrivs int) *windows.Tokenprivileges {
if numPrivs <= 0 {
panic("numPrivs must be > 0")
}
numBytes := unsafe.Sizeof(windows.Tokenprivileges{}) + (uintptr(numPrivs-1) * unsafe.Sizeof(windows.LUIDAndAttributes{}))
buf := make([]byte, numBytes)
result := (*windows.Tokenprivileges)(unsafe.Pointer(unsafe.SliceData(buf)))
result.PrivilegeCount = uint32(numPrivs)
return result
}
// StartProcessAsChild starts exePath process as a child of parentPID.
// StartProcessAsChild copies parentPID's environment variables into
// the new process, along with any optional environment variables in extraEnv.
func StartProcessAsChild(parentPID uint32, exePath string, extraEnv []string) error {
// The rest of this function requires SeDebugPrivilege to be held.
//
// According to https://docs.microsoft.com/en-us/windows/win32/procthread/process-security-and-access-rights
//
// ... To open a handle to another process and obtain full access rights,
// you must enable the SeDebugPrivilege privilege. ...
//
// But we only need PROCESS_CREATE_PROCESS. So perhaps SeDebugPrivilege is too much.
//
// https://devblogs.microsoft.com/oldnewthing/20080314-00/?p=23113
//
// TODO: try look for something less than SeDebugPrivilege
disableSeDebug, err := EnableCurrentThreadPrivilege("SeDebugPrivilege")
if err != nil {
return err
}
defer disableSeDebug()
ph, err := windows.OpenProcess(
windows.PROCESS_CREATE_PROCESS|windows.PROCESS_QUERY_INFORMATION|windows.PROCESS_DUP_HANDLE,
false, parentPID)
if err != nil {
return err
}
defer windows.CloseHandle(ph)
var pt windows.Token
err = windows.OpenProcessToken(ph, windows.TOKEN_QUERY, &pt)
if err != nil {
return err
}
defer pt.Close()
env, err := pt.Environ(false)
if err != nil {
return err
}
env = append(env, extraEnv...)
sys := &syscall.SysProcAttr{ParentProcess: syscall.Handle(ph)}
cmd := exec.Command(exePath)
cmd.Env = env
cmd.SysProcAttr = sys
return cmd.Start()
}
// StartProcessAsCurrentGUIUser is like StartProcessAsChild, but if finds
// current logged in user desktop process (normally explorer.exe),
// and passes found PID to StartProcessAsChild.
func StartProcessAsCurrentGUIUser(exePath string, extraEnv []string) error {
// as described in https://devblogs.microsoft.com/oldnewthing/20190425-00/?p=102443
desktop, err := GetDesktopPID()
if err != nil {
return fmt.Errorf("failed to find desktop: %v", err)
}
err = StartProcessAsChild(desktop, exePath, extraEnv)
if err != nil {
return fmt.Errorf("failed to start executable: %v", err)
}
return nil
}
// CreateAppMutex creates a named Windows mutex, returning nil if the mutex
// is created successfully or an error if the mutex already exists or could not
// be created for some other reason.
func CreateAppMutex(name string) (windows.Handle, error) {
return windows.CreateMutex(nil, false, windows.StringToUTF16Ptr(name))
}
// getTokenInfoFixedLen obtains known fixed-length token information. Use this
// function for information classes that output enumerations, BOOLs, integers etc.
func getTokenInfoFixedLen[T any](token windows.Token, infoClass uint32) (result T, err error) {
var actualLen uint32
p := (*byte)(unsafe.Pointer(&result))
err = windows.GetTokenInformation(token, infoClass, p, uint32(unsafe.Sizeof(result)), &actualLen)
return result, err
}
type tokenElevationType int32
const (
tokenElevationTypeDefault tokenElevationType = 1
tokenElevationTypeFull tokenElevationType = 2
tokenElevationTypeLimited tokenElevationType = 3
)
// IsTokenLimited returns whether token is a limited UAC token.
func IsTokenLimited(token windows.Token) (bool, error) {
elevationType, err := getTokenInfoFixedLen[tokenElevationType](token, windows.TokenElevationType)
if err != nil {
return false, err
}
return elevationType == tokenElevationTypeLimited, nil
}
// UserSIDs contains the SIDs for a Windows NT token object's associated user
// as well as its primary group.
type UserSIDs struct {
User *windows.SID
PrimaryGroup *windows.SID
}
// GetCurrentUserSIDs returns a UserSIDs struct containing SIDs for the
// current process' user and primary group.
func GetCurrentUserSIDs() (*UserSIDs, error) {
token, err := windows.OpenCurrentProcessToken()
if err != nil {
return nil, err
}
defer token.Close()
userInfo, err := token.GetTokenUser()
if err != nil {
return nil, err
}
primaryGroup, err := token.GetTokenPrimaryGroup()
if err != nil {
return nil, err
}
return &UserSIDs{userInfo.User.Sid, primaryGroup.PrimaryGroup}, nil
}
// IsCurrentProcessElevated returns true when the current process is
// running with an elevated token, implying Administrator access.
func IsCurrentProcessElevated() bool {
token, err := windows.OpenCurrentProcessToken()
if err != nil {
return false
}
defer token.Close()
return token.IsElevated()
}
// keyOpenTimeout is how long we wait for a registry key to appear. For some
// reason, registry keys tied to ephemeral interfaces can take a long while to
// appear after interface creation, and we can end up racing with that.
const keyOpenTimeout = 20 * time.Second
// RegistryPath represents a path inside a root registry.Key.
type RegistryPath string
// RegistryPathPrefix specifies a RegistryPath prefix that must be suffixed with
// another RegistryPath to make a valid RegistryPath.
type RegistryPathPrefix string
// WithSuffix returns a RegistryPath with the given suffix appended.
func (p RegistryPathPrefix) WithSuffix(suf string) RegistryPath {
return RegistryPath(string(p) + suf)
}
const (
IPv4TCPIPBase RegistryPath = `SYSTEM\CurrentControlSet\Services\Tcpip\Parameters`
IPv6TCPIPBase RegistryPath = `SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters`
NetBTBase RegistryPath = `SYSTEM\CurrentControlSet\Services\NetBT\Parameters`
IPv4TCPIPInterfacePrefix RegistryPathPrefix = `SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\`
IPv6TCPIPInterfacePrefix RegistryPathPrefix = `SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\Interfaces\`
NetBTInterfacePrefix RegistryPathPrefix = `SYSTEM\CurrentControlSet\Services\NetBT\Parameters\Interfaces\Tcpip_`
)
// ErrKeyWaitTimeout is returned by OpenKeyWait when calls timeout.
var ErrKeyWaitTimeout = errors.New("timeout waiting for registry key")
// OpenKeyWait opens a registry key, waiting for it to appear if necessary. It
// returns the opened key, or ErrKeyWaitTimeout if the key does not appear
// within 20s. The caller must call Close on the returned key.
func OpenKeyWait(k registry.Key, path RegistryPath, access uint32) (registry.Key, error) {
runtime.LockOSThread()
defer runtime.UnlockOSThread()
deadline := time.Now().Add(keyOpenTimeout)
pathSpl := strings.Split(string(path), "\\")
for i := 0; ; i++ {
keyName := pathSpl[i]
isLast := i+1 == len(pathSpl)
event, err := windows.CreateEvent(nil, 0, 0, nil)
if err != nil {
return 0, fmt.Errorf("windows.CreateEvent: %w", err)
}
defer windows.CloseHandle(event)
var key registry.Key
for {
err = windows.RegNotifyChangeKeyValue(windows.Handle(k), false, windows.REG_NOTIFY_CHANGE_NAME, event, true)
if err != nil {
return 0, fmt.Errorf("windows.RegNotifyChangeKeyValue: %w", err)
}
var accessFlags uint32
if isLast {
accessFlags = access
} else {
accessFlags = registry.NOTIFY
}
key, err = registry.OpenKey(k, keyName, accessFlags)
if err == windows.ERROR_FILE_NOT_FOUND || err == windows.ERROR_PATH_NOT_FOUND {
timeout := time.Until(deadline) / time.Millisecond
if timeout < 0 {
timeout = 0
}
s, err := windows.WaitForSingleObject(event, uint32(timeout))
if err != nil {
return 0, fmt.Errorf("windows.WaitForSingleObject: %w", err)
}
if s == uint32(windows.WAIT_TIMEOUT) { // windows.WAIT_TIMEOUT status const is misclassified as error in golang.org/x/sys/windows
return 0, ErrKeyWaitTimeout
}
} else if err != nil {
return 0, fmt.Errorf("registry.OpenKey(%v): %w", path, err)
} else {
if isLast {
return key, nil
}
defer key.Close()
break
}
}
k = key
}
}
func lookupPseudoUser(uid string) (*user.User, error) {
sid, err := windows.StringToSid(uid)
if err != nil {
return nil, err
}
// We're looking for SIDs "S-1-5-x" where 17 <= x <= 20.
// This is checking for the the "5"
if sid.IdentifierAuthority() != windows.SECURITY_NT_AUTHORITY {
return nil, fmt.Errorf(`SID %q does not use "NT AUTHORITY"`, uid)
}
// This is ensuring that there is only one sub-authority.
// In other words, only one value after the "5".
if sid.SubAuthorityCount() != 1 {
return nil, fmt.Errorf("SID %q should have only one subauthority", uid)
}
// Get that sub-authority value (this is "x" above) and check it.
rid := sid.SubAuthority(0)
if rid < 17 || rid > 20 {
return nil, fmt.Errorf("SID %q does not represent a known pseudo-user", uid)
}
// We've got one of the known pseudo-users. Look up the localized name of the
// account.
username, domain, _, err := sid.LookupAccount("")
if err != nil {
return nil, err
}
// This call is best-effort. If it fails, homeDir will be empty.
homeDir, _ := findHomeDirInRegistry(uid)
result := &user.User{
Uid: uid,
Gid: uid, // Gid == Uid with these accounts.
Username: fmt.Sprintf(`%s\%s`, domain, username),
Name: username,
HomeDir: homeDir,
}
return result, nil
}
// findHomeDirInRegistry finds the user home path based on the uid.
// This is borrowed from Go's std lib.
func findHomeDirInRegistry(uid string) (dir string, err error) {
k, err := registry.OpenKey(registry.LOCAL_MACHINE, `SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList\`+uid, registry.QUERY_VALUE)
if err != nil {
return "", err
}
defer k.Close()
dir, _, err = k.GetStringValue("ProfileImagePath")
if err != nil {
return "", err
}
return dir, nil
}
// ProcessImageName returns the fully-qualified path to the executable image
// associated with process.
func ProcessImageName(process windows.Handle) (string, error) {
var pathBuf [windows.MAX_PATH]uint16
pathBufLen := uint32(len(pathBuf))
if err := windows.QueryFullProcessImageName(process, 0, &pathBuf[0], &pathBufLen); err != nil {
return "", err
}
return windows.UTF16ToString(pathBuf[:pathBufLen]), nil
}
// TSSessionIDToLogonSessionID retrieves the logon session ID associated with
// tsSessionId, which is a Terminal Services / RDP session ID. The calling
// process must be running as LocalSystem.
func TSSessionIDToLogonSessionID(tsSessionID uint32) (logonSessionID windows.LUID, err error) {
var token windows.Token
if err := windows.WTSQueryUserToken(tsSessionID, &token); err != nil {
return logonSessionID, fmt.Errorf("WTSQueryUserToken: %w", err)
}
defer token.Close()
return LogonSessionID(token)
}
// TSSessionID obtains the Terminal Services (RDP) session ID associated with token.
func TSSessionID(token windows.Token) (tsSessionID uint32, err error) {
return getTokenInfoFixedLen[uint32](token, windows.TokenSessionId)
}
type tokenOrigin struct {
originatingLogonSession windows.LUID
}
// LogonSessionID obtains the logon session ID associated with token.
func LogonSessionID(token windows.Token) (logonSessionID windows.LUID, err error) {
origin, err := getTokenInfoFixedLen[tokenOrigin](token, windows.TokenOrigin)
if err != nil {
return logonSessionID, err
}
return origin.originatingLogonSession, nil
}
// BufUnit is a type constraint for buffers passed into AllocateContiguousBuffer.
type BufUnit interface {
byte | uint16
}
// AllocateContiguousBuffer allocates memory to satisfy the Windows idiom where
// some structs contain pointers that are expected to refer to memory within the
// same buffer containing the struct itself. T is the type that contains
// the pointers. values must contain the actual data that is to be copied
// into the buffer after T. AllocateContiguousBuffer returns a pointer to the
// struct, the total length of the buffer in bytes, and a slice containing
// each value within the buffer. The caller may use slcs to populate any
// pointers in t as needed. Each element of slcs corresponds to the element of
// values in the same position.
//
// It is the responsibility of the caller to ensure that any values expected
// to contain null-terminated strings are in fact null-terminated!
//
// AllocateContiguousBuffer panics if no values are passed in, as there are
// better alternatives for allocating a struct in that case.
func AllocateContiguousBuffer[T any, BU BufUnit](values ...[]BU) (t *T, tLenBytes uint32, slcs [][]BU) {
if len(values) == 0 {
panic("len(values) must be > 0")
}
// Get the sizes of T and BU, then compute a preferred alignment for T.
tT := reflect.TypeFor[T]()
szT := tT.Size()
szBU := int(unsafe.Sizeof(BU(0)))
alignment := max(tT.Align(), szBU)
// Our buffers for values will start at the next szBU boundary.
tLenBytes = alignUp(uint32(szT), szBU)
firstValueOffset := tLenBytes
// Accumulate the length of each value into tLenBytes
for _, v := range values {
tLenBytes += uint32(len(v) * szBU)
}
// Now that we know the final length, align up to our preferred boundary.
tLenBytes = alignUp(tLenBytes, alignment)
// Allocate the buffer. We choose a type for the slice that is appropriate
// for the desired alignment. Note that we do not have a strict requirement
// that T contain pointer fields; we could just be appending more data
// within the same buffer.
bufLen := tLenBytes / uint32(alignment)
var pt unsafe.Pointer
switch alignment {
case 1:
pt = unsafe.Pointer(unsafe.SliceData(make([]byte, bufLen)))
case 2:
pt = unsafe.Pointer(unsafe.SliceData(make([]uint16, bufLen)))
case 4:
pt = unsafe.Pointer(unsafe.SliceData(make([]uint32, bufLen)))
case 8:
pt = unsafe.Pointer(unsafe.SliceData(make([]uint64, bufLen)))
default:
panic(fmt.Sprintf("bad alignment %d", alignment))
}
t = (*T)(pt)
slcs = make([][]BU, 0, len(values))
// Use the limits of the buffer area after t to construct a slice representing the remaining buffer.
firstValuePtr := unsafe.Pointer(uintptr(pt) + uintptr(firstValueOffset))
buf := unsafe.Slice((*BU)(firstValuePtr), (tLenBytes-firstValueOffset)/uint32(szBU))
// Copy each value into the buffer and record a slice describing each value's limits into slcs.
var index int
for _, v := range values {
if len(v) == 0 {
// We allow zero-length values; we simply append a nil slice.
slcs = append(slcs, nil)
continue
}
valueSlice := buf[index : index+len(v)]
copy(valueSlice, v)
slcs = append(slcs, valueSlice)
index += len(v)
}
return t, tLenBytes, slcs
}
// alignment must be a power of 2
func alignUp[V constraints.Integer](v V, alignment int) V {
return v + ((-v) & (V(alignment) - 1))
}
// NTStr is a type constraint requiring the type to be either a
// windows.NTString or a windows.NTUnicodeString.
type NTStr interface {
windows.NTString | windows.NTUnicodeString
}
// SetNTString sets the value of nts in-place to point to the string contained
// within buf. A nul terminator is optional in buf.
func SetNTString[NTS NTStr, BU BufUnit](nts *NTS, buf []BU) {
isEmpty := len(buf) == 0
codeUnitSize := uint16(unsafe.Sizeof(BU(0)))
lenBytes := len(buf) * int(codeUnitSize)
if lenBytes > math.MaxUint16 {
panic("buffer length must fit into uint16")
}
lenBytes16 := uint16(lenBytes)
switch p := any(nts).(type) {
case *windows.NTString:
if isEmpty {
*p = windows.NTString{}
break
}
p.Buffer = unsafe.SliceData(any(buf).([]byte))
p.MaximumLength = lenBytes16
p.Length = lenBytes16
// account for nul terminator when present
if buf[len(buf)-1] == 0 {
p.Length -= codeUnitSize
}
case *windows.NTUnicodeString:
if isEmpty {
*p = windows.NTUnicodeString{}
break
}
p.Buffer = unsafe.SliceData(any(buf).([]uint16))
p.MaximumLength = lenBytes16
p.Length = lenBytes16
// account for nul terminator when present
if buf[len(buf)-1] == 0 {
p.Length -= codeUnitSize
}
default:
panic("unknown type")
}
}