[PATCH 3/3] ntdll: Use ProcessCookie in RtlEncode/DecodePointer.
Myah Caron
qsniyg at protonmail.com
Wed Oct 14 22:04:36 CDT 2020
Signed-off-by: Myah Caron <qsniyg at protonmail.com>
---
I've opted to use a helper function, as it both makes the code cleaner, as well as avoid
unneeded "syscalls" (could be a performance issue for an application that calls
Encode/DecodePointer repeatedly).
dlls/ntdll/rtl.c | 30 +++++++++++-------------------
1 file changed, 11 insertions(+), 19 deletions(-)
diff --git a/dlls/ntdll/rtl.c b/dlls/ntdll/rtl.c
index 154de807501..8c8c8c9bb1a 100644
--- a/dlls/ntdll/rtl.c
+++ b/dlls/ntdll/rtl.c
@@ -1516,30 +1516,22 @@ WCHAR * WINAPI RtlIpv6AddressToStringW(const IN6_ADDR *address, WCHAR *str)
}
/***********************************************************************
- * get_pointer_obfuscator (internal)
+ * get_process_cookie (internal)
*/
-static DWORD_PTR get_pointer_obfuscator( void )
+static ULONG get_process_cookie( void )
{
- static DWORD_PTR pointer_obfuscator;
+ static ULONG process_cookie;
- if (!pointer_obfuscator)
+ if (!process_cookie)
{
- ULONG seed = NtGetTickCount();
- ULONG_PTR rand;
+ ULONG cookie;
+ NtQueryInformationProcess( NtCurrentProcess(), ProcessCookie, &cookie,
+ sizeof( cookie ), NULL );
- /* generate a random value for the obfuscator */
- rand = RtlUniform( &seed );
-
- /* handle 64bit pointers */
- rand ^= (ULONG_PTR)RtlUniform( &seed ) << ((sizeof (DWORD_PTR) - sizeof (ULONG))*8);
-
- /* set the high bits so dereferencing obfuscated pointers will (usually) crash */
- rand |= (ULONG_PTR)0xc0000000 << ((sizeof (DWORD_PTR) - sizeof (ULONG))*8);
-
- InterlockedCompareExchangePointer( (void**) &pointer_obfuscator, (void*) rand, NULL );
+ InterlockedExchange( (LONG*)&process_cookie, cookie );
}
- return pointer_obfuscator;
+ return process_cookie;
}
/***********************************************************************
@@ -1575,7 +1567,7 @@ PVOID WINAPI RtlEncodePointer( PVOID ptr )
{
DWORD_PTR ptrval = (DWORD_PTR) ptr;
- DWORD_PTR cookie = get_pointer_obfuscator();
+ DWORD_PTR cookie = (DWORD_PTR) get_process_cookie();
/* http://blogs.msdn.com/b/michael_howard/archive/2006/08/16/702707.aspx */
@@ -1586,7 +1578,7 @@ PVOID WINAPI RtlEncodePointer( PVOID ptr )
PVOID WINAPI RtlDecodePointer( PVOID ptr )
{
DWORD_PTR ptrval = (DWORD_PTR) ptr;
- DWORD_PTR cookie = get_pointer_obfuscator();
+ DWORD_PTR cookie = (DWORD_PTR) get_process_cookie();
ptrval = rotl_ptr(ptrval, cookie);
return (PVOID)(ptrval ^ cookie);
--
2.28.0
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