windows: add basic WTS functions for windows/svc usage

The svc package exposes svc.SessionChange, but it's impossible to do
anything with them without these structures, and without being able to
enumerate them prior to events, the events themselves aren't useful, so
we add the enumeration functions as well.

Change-Id: I14c932dfe97c6712fd4868c1b3a0e3a61a6a562c
Reviewed-on: https://go-review.googlesource.com/c/sys/+/176623
Run-TryBot: Jason Donenfeld <Jason@zx2c4.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

windows/security_windows.go

@@ -717,3 +717,45 @@ func (t Token) IsMember(sid *SID) (bool, error) {
 	}
 	return b != 0, nil
 }
+
+const (
+	WTS_CONSOLE_CONNECT        = 0x1
+	WTS_CONSOLE_DISCONNECT     = 0x2
+	WTS_REMOTE_CONNECT         = 0x3
+	WTS_REMOTE_DISCONNECT      = 0x4
+	WTS_SESSION_LOGON          = 0x5
+	WTS_SESSION_LOGOFF         = 0x6
+	WTS_SESSION_LOCK           = 0x7
+	WTS_SESSION_UNLOCK         = 0x8
+	WTS_SESSION_REMOTE_CONTROL = 0x9
+	WTS_SESSION_CREATE         = 0xa
+	WTS_SESSION_TERMINATE      = 0xb
+)
+
+const (
+	WTSActive       = 0
+	WTSConnected    = 1
+	WTSConnectQuery = 2
+	WTSShadow       = 3
+	WTSDisconnected = 4
+	WTSIdle         = 5
+	WTSListen       = 6
+	WTSReset        = 7
+	WTSDown         = 8
+	WTSInit         = 9
+)
+
+type WTSSESSION_NOTIFICATION struct {
+	Size      uint32
+	SessionID uint32
+}
+
+type WTS_SESSION_INFO struct {
+	SessionID         uint32
+	WindowStationName *uint16
+	State             uint32
+}
+
+//sys WTSQueryUserToken(session uint32, token *Token) (err error) = wtsapi32.WTSQueryUserToken
+//sys WTSEnumerateSessions(handle Handle, reserved uint32, version uint32, sessions **WTS_SESSION_INFO, count *uint32) (err error) = wtsapi32.WTSEnumerateSessionsW
+//sys WTSFreeMemory(ptr uintptr) = wtsapi32.WTSFreeMemory

windows/zsyscall_windows.go

@@ -46,6 +46,7 @@ var (
 	modsecur32  = NewLazySystemDLL("secur32.dll")
 	modnetapi32 = NewLazySystemDLL("netapi32.dll")
 	moduserenv  = NewLazySystemDLL("userenv.dll")
+	modwtsapi32 = NewLazySystemDLL("wtsapi32.dll")
 
 	procRegisterEventSourceW               = modadvapi32.NewProc("RegisterEventSourceW")
 	procDeregisterEventSource              = modadvapi32.NewProc("DeregisterEventSource")
@@ -269,6 +270,9 @@ var (
 	procDuplicateTokenEx                   = modadvapi32.NewProc("DuplicateTokenEx")
 	procGetUserProfileDirectoryW           = moduserenv.NewProc("GetUserProfileDirectoryW")
 	procGetSystemDirectoryW                = modkernel32.NewProc("GetSystemDirectoryW")
+	procWTSQueryUserToken                  = modwtsapi32.NewProc("WTSQueryUserToken")
+	procWTSEnumerateSessionsW              = modwtsapi32.NewProc("WTSEnumerateSessionsW")
+	procWTSFreeMemory                      = modwtsapi32.NewProc("WTSFreeMemory")
 )
 
 func RegisterEventSource(uncServerName *uint16, sourceName *uint16) (handle Handle, err error) {
@@ -2943,3 +2947,32 @@ func getSystemDirectory(dir *uint16, dirLen uint32) (len uint32, err error) {
 	}
 	return
 }
+
+func WTSQueryUserToken(session uint32, token *Token) (err error) {
+	r1, _, e1 := syscall.Syscall(procWTSQueryUserToken.Addr(), 2, uintptr(session), uintptr(unsafe.Pointer(token)), 0)
+	if r1 == 0 {
+		if e1 != 0 {
+			err = errnoErr(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}
+
+func WTSEnumerateSessions(handle Handle, reserved uint32, version uint32, sessions **WTS_SESSION_INFO, count *uint32) (err error) {
+	r1, _, e1 := syscall.Syscall6(procWTSEnumerateSessionsW.Addr(), 5, uintptr(handle), uintptr(reserved), uintptr(version), uintptr(unsafe.Pointer(sessions)), uintptr(unsafe.Pointer(count)), 0)
+	if r1 == 0 {
+		if e1 != 0 {
+			err = errnoErr(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}
+
+func WTSFreeMemory(ptr uintptr) {
+	syscall.Syscall(procWTSFreeMemory.Addr(), 1, uintptr(ptr), 0, 0)
+	return
+}