Mike McCormack : ntdll: Implement RtlDecodePointer and RtlEncodePointer.

[Alexandre Julliard]

Module: wine
Branch: master
Commit: bcc717174c54017e0cb5dfdb8c0a8e4f521ea42a
URL:    http://source.winehq.org/git/wine.git/?a=commit;h=bcc717174c54017e0cb5dfdb8c0a8e4f521ea42a

Author: Mike McCormack <mike at codeweavers.com>
Date:   Mon Jan 22 19:24:14 2007 +0900

ntdll: Implement RtlDecodePointer and RtlEncodePointer.

---

 dlls/ntdll/ntdll.spec |    4 ++--
 dlls/ntdll/rtl.c      |   36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/dlls/ntdll/ntdll.spec b/dlls/ntdll/ntdll.spec
index 803ed53..b3e3540 100644
--- a/dlls/ntdll/ntdll.spec
+++ b/dlls/ntdll/ntdll.spec
@@ -501,7 +501,7 @@
 @ stub RtlDeactivateActivationContext
 @ stub RtlDeactivateActivationContextUnsafeFast
 @ stub RtlDebugPrintTimes
-# @ stub RtlDecodePointer
+@ stdcall RtlDecodePointer(ptr)
 # @ stub RtlDecodeSystemPointer
 @ stub RtlDecompressBuffer
 @ stub RtlDecompressFragment
@@ -543,7 +543,7 @@
 @ stdcall RtlDuplicateUnicodeString(long ptr ptr)
 @ stdcall RtlEmptyAtomTable(ptr long)
 # @ stub RtlEnableEarlyCriticalSectionEventCreation
-# @ stub RtlEncodePointer
+@ stdcall RtlEncodePointer(ptr)
 # @ stub RtlEncodeSystemPointer
 @ stdcall -ret64 RtlEnlargedIntegerMultiply(long long)
 @ stdcall RtlEnlargedUnsignedDivide(double long ptr)
diff --git a/dlls/ntdll/rtl.c b/dlls/ntdll/rtl.c
index 8ddab6a..449e91a 100644
--- a/dlls/ntdll/rtl.c
+++ b/dlls/ntdll/rtl.c
@@ -886,3 +886,39 @@ NTSTATUS WINAPI RtlIpv4AddressToStringEx
 
     return STATUS_SUCCESS;
 }
+
+static DWORD_PTR get_pointer_obfuscator( void )
+{
+    static DWORD_PTR pointer_obfuscator;
+
+    if (!pointer_obfuscator)
+    {
+        ULONG seed = NtGetTickCount();
+        ULONG_PTR rand;
+
+        /* generate a random value for the obfuscator */
+        rand = RtlUniform( &seed );
+
+        /* handle 64bit pointers */
+        rand ^= RtlUniform( &seed ) << ((sizeof (DWORD_PTR) - sizeof (ULONG))*8);
+
+        /* set the high bits so dereferencing obfuscated pointers will (usually) crash */
+        rand |= 0xc0000000 << ((sizeof (DWORD_PTR) - sizeof (ULONG))*8);
+
+        interlocked_cmpxchg_ptr( (void**) &pointer_obfuscator, (void*) rand, NULL );
+    }
+
+    return pointer_obfuscator;
+}
+
+PVOID WINAPI RtlEncodePointer( PVOID ptr )
+{
+    DWORD_PTR ptrval = (DWORD_PTR) ptr;
+    return (PVOID)(ptrval ^ get_pointer_obfuscator());
+}
+
+PVOID WINAPI RtlDecodePointer( PVOID ptr )
+{
+    DWORD_PTR ptrval = (DWORD_PTR) ptr;
+    return (PVOID)(ptrval ^ get_pointer_obfuscator());
+}