Question

I’m trying to hide some values in the registry (such as serial numbers) with C++/windows
so I’ve been looking at this article http://www.codeproject.com/KB/system/NtRegistry.aspx
which says:

How is this possible? The answer is
that a name which is a counted as a
Unicode string can explicitly include
NULL characters (0) as part of the
name. For example, “Key\0”. To include
the NULL at the end, the length of the
Unicode string is specified as 4.
There is absolutely no way to specify
this name using the Win32 API since if
“Key\0” is passed as a name, the API
will determine that the name is “Key”
(3 characters in length) because the
“\0” indicates the end of the name.

When a key (or any other object with a
name such as a named Event, Semaphore,
or Mutex) is created with such a name,
any application using the Win32 API
will be unable to open the name, even
though they might seem to see it.

so I tried doing something similar:

HKEY keyHandle;
PHKEY key;
unsigned long status = 0;

wchar_t *wKeyName = new wchar_t[m_keyLength];
MultiByteToWideChar(CP_ACP, 0, m_keyName, m_keyLength, wKeyName, m_keyLength);
wKeyName[18] = '\0';
long result = RegCreateKeyExW(HKEY_LOCAL_MACHINE, 
                              wKeyName,
                              0,
                              NULL,
                              0,
                              KEY_ALL_ACCESS,
                              NULL,
                              &keyHandle,
                              &status);

where m_keyName is the ASCII text and wKeyName is the wide char text, but in regedit I see that it is treated the same and the key is just cut where I put the ‘\0’.

what is wrong with it?

Answer 1

The problem is that you are using the Win32 API and not the NT Native API. There is a table about 1/2 way through the article that you referenced that contains the list of Native APIs. For example, you would use NtCreateKey or ZwCreateKey instead of RegCreateKeyExW. The Win32 API assumes that alls strings are terminated by a NUL character whereas the Native API counterparts use a UNICODE_STRING structure for the name.