diff --git a/reactos/include/ntdll/rtl.h b/reactos/include/ntdll/rtl.h
index 7d41be0a5bd..e66f2d9e24e 100644
--- a/reactos/include/ntdll/rtl.h
+++ b/reactos/include/ntdll/rtl.h
@@ -1,4 +1,4 @@
-/* $Id: rtl.h,v 1.31 2001/06/24 17:58:13 phreak Exp $
+/* $Id: rtl.h,v 1.32 2001/11/21 22:27:26 ekohl Exp $
  *
  */
 
@@ -465,6 +465,12 @@ RtlIsValidIndexHandle (
 	IN	ULONG			Index
 	);
 
+NTSTATUS
+STDCALL
+RtlImpersonateSelf (
+	IN	SECURITY_IMPERSONATION_LEVEL	ImpersonationLevel
+	);
+
 NTSTATUS
 STDCALL
 RtlpNtCreateKey (
diff --git a/reactos/lib/ntdll/def/ntdll.def b/reactos/lib/ntdll/def/ntdll.def
index 71bdba050b6..6660aabdeed 100644
--- a/reactos/lib/ntdll/def/ntdll.def
+++ b/reactos/lib/ntdll/def/ntdll.def
@@ -1,4 +1,4 @@
-; $Id: ntdll.def,v 1.80 2001/11/03 16:48:06 chorns Exp $
+; $Id: ntdll.def,v 1.81 2001/11/21 22:31:18 ekohl Exp $
 ;
 ; ReactOS Operating System
 ;
@@ -434,7 +434,7 @@ RtlImageDirectoryEntryToData@16
 RtlImageNtHeader@4
 RtlImageRvaToSection@12
 RtlImageRvaToVa@16
-;RtlImpersonateSelf
+RtlImpersonateSelf@4
 RtlInitAnsiString@8
 ;RtlInitCodePageTable
 ;RtlInitNlsTables
diff --git a/reactos/lib/ntdll/def/ntdll.edf b/reactos/lib/ntdll/def/ntdll.edf
index 7fc9125b7ec..9e7cc479c6e 100644
--- a/reactos/lib/ntdll/def/ntdll.edf
+++ b/reactos/lib/ntdll/def/ntdll.edf
@@ -1,4 +1,4 @@
-; $Id: ntdll.edf,v 1.69 2001/11/03 16:48:06 chorns Exp $
+; $Id: ntdll.edf,v 1.70 2001/11/21 22:31:18 ekohl Exp $
 ;
 ; ReactOS Operating System
 ;
@@ -433,7 +433,7 @@ RtlImageDirectoryEntryToData=RtlImageDirectoryEntryToData@16
 RtlImageNtHeader=RtlImageNtHeader@4
 RtlImageRvaToSection=RtlImageRvaToSection@12
 RtlImageRvaToVa=RtlImageRvaToVa@16
-;RtlImpersonateSelf
+RtlImpersonateSelf=RtlImpersonateSelf@4
 RtlInitAnsiString=RtlInitAnsiString@8
 ;RtlInitCodePageTable
 ;RtlInitNlsTables
diff --git a/reactos/lib/ntdll/makefile b/reactos/lib/ntdll/makefile
index 48f93880732..fcc5af0aa94 100644
--- a/reactos/lib/ntdll/makefile
+++ b/reactos/lib/ntdll/makefile
@@ -1,4 +1,4 @@
-# $Id: makefile,v 1.67 2001/11/03 16:48:05 chorns Exp $
+# $Id: makefile,v 1.68 2001/11/21 22:30:57 ekohl Exp $
 
 PATH_TO_TOP = ../..
 
@@ -31,7 +31,7 @@ RTL_OBJECTS = rtl/critical.o rtl/error.o rtl/heap.o rtl/largeint.o \
               rtl/access.o rtl/apc.o rtl/callback.o rtl/luid.o rtl/misc.o \
               rtl/registry.o rtl/exception.o rtl/intrlck.o rtl/resource.o \
               rtl/handle.o rtl/atom.o rtl/message.o rtl/timezone.o \
-      	      rtl/propvar.o
+      	      rtl/propvar.o rtl/security.o
 
 STDIO_OBJECTS = stdio/sprintf.o stdio/swprintf.o
 
diff --git a/reactos/lib/ntdll/rtl/security.c b/reactos/lib/ntdll/rtl/security.c
new file mode 100644
index 00000000000..f770a5947af
--- /dev/null
+++ b/reactos/lib/ntdll/rtl/security.c
@@ -0,0 +1,65 @@
+/* $Id: security.c,v 1.4 2001/11/21 22:30:45 ekohl Exp $
+ *
+ * COPYRIGHT:       See COPYING in the top level directory
+ * PROJECT:         ReactOS kernel
+ * FILE:            lib/ntdll/rtl/security.c
+ * PURPOSE:         Miscellaneous securitiy related functions
+ * PROGRAMMER:      Eric Kohl
+ * UPDATE HISTORY:
+ *                  21/11/2001 Created
+ */
+
+#include <ddk/ntddk.h>
+#include <ntdll/rtl.h>
+
+
+NTSTATUS STDCALL
+RtlImpersonateSelf(IN SECURITY_IMPERSONATION_LEVEL ImpersonationLevel)
+{
+  OBJECT_ATTRIBUTES ObjectAttributes;
+  SECURITY_QUALITY_OF_SERVICE SecQos;
+  HANDLE ProcessToken;
+  HANDLE ImpersonationToken;
+  NTSTATUS Status;
+
+  Status = NtOpenProcessToken(NtCurrentProcess(),
+			      TOKEN_DUPLICATE,
+			      &ProcessToken);
+  if (!NT_SUCCESS(Status))
+    return(Status);
+
+  SecQos.Length = sizeof(SECURITY_QUALITY_OF_SERVICE);
+  SecQos.ImpersonationLevel = ImpersonationLevel;
+  SecQos.ContextTrackingMode = SECURITY_DYNAMIC_TRACKING;
+  SecQos.EffectiveOnly = FALSE;
+
+  ObjectAttributes.Length = sizeof(OBJECT_ATTRIBUTES);
+  ObjectAttributes.RootDirectory = 0;
+  ObjectAttributes.ObjectName = NULL;
+  ObjectAttributes.Attributes = 0;
+  ObjectAttributes.SecurityDescriptor = NULL;
+  ObjectAttributes.SecurityQualityOfService = &SecQos;
+
+  Status = NtDuplicateToken(ProcessToken,
+			    TOKEN_IMPERSONATE,
+			    &ObjectAttributes,
+			    NULL,
+			    TokenImpersonation,
+			    &ImpersonationToken);
+  if (!NT_SUCCESS(Status))
+    {
+      NtClose(ProcessToken);
+      return(Status);
+    }
+
+  Status = NtSetInformationThread(NtCurrentThread(),
+				  ThreadImpersonationToken,
+				  &ImpersonationToken,
+				  sizeof(HANDLE));
+  NtClose(ImpersonationToken);
+  NtClose(ProcessToken);
+
+  return(Status);
+}
+
+/* EOF */