Question

I’m converting this code from C++ to Delphi but I don’t get the following part of the code. Can anyone explain me what the following code means; what’s happening to the szBuff buffer ?

I’m pretty sure it’s such kind of formatting (replacement), but I don’t even know what is expected as a result and I can’t find any sensible documentation of the used functions (maybe I’m just a lame 🙂

Can anyone help me with the translation of this code to Delphi (or direct me to proper documentation) ?

I don’t like this how do you convert kind of questions by myself, so I mentioned at least function names in the question title so it might searchable to someone else in the future.

function TSecInfo.BuildSecurityAttributes(var SecAttrs: TSecurityAttributes): boolean;
var
  pszSidUser: PChar;
  szBuff: array [0..1024] of Char;
begin

// pszSidUser at this time contains user SID like this
// S-1-5-21-1454471165-1004336348-1606980848-5555

// TCHAR szBuff[1024]; // I'm not sure with array [0..1024] of Char;

  _tcscpy(szBuff, _T("D:"));
  _tcscat(szBuff, _T("(A;;GA;;;"));
  _tcscat(szBuff, pszSidUser);
  _tcscat(szBuff, _T(")"));
  _tcscat(szBuff, _T("(A;;GWGR;;;AN)"));
  _tcscat(szBuff, _T("(A;;GWGR;;;WD)"));

...

  _tcscat(szBuff, _T("S:(ML;;NW;;;S-1-16-0)"));

end;

For those who are interested in what’s the whole code from the link about I can tell it should be a trick how to access network pipes for writing as an anonymous user on Windows Vista above. To the whole article follow this link.

Thanks for your time
Regards

Answer 1

_tcscpy and _tcscat are TCHAR macro versions of C standard library functions strcpy and strcat for copying and concatenating C strings. They evaluate to ANSI or Unicode versions depending on whether or the type of project you are targeting. It’s really C code rather than C++ code in my view.

In Delphi you would simply use string variables like this:

function TSecInfo.BuildSecurityAttributes(var SecAttrs: TSecurityAttributes): boolean;
var
  pszSidUser: PChar;
  Buff: string;
begin
  // pszSidUser at this time contains user SID like this
  // S-1-5-21-1454471165-1004336348-1606980848-5555

  Buff := 'D:(A;;GA;;;'+pszSidUser+')(A;;GWGR;;;AN)(A;;GWGR;;;WD)S:(ML;;NW;;;S-1-16-0)';
  SomeOtherWindowsAPICall(PChar(Buff));    
end;

Presumably in the C code there is a call to another Windows API function that receives an LPCTSTR. The C code will pass szBuff but you can simply pass PChar(Buff) as I have shown above.

The C code is using a fixed length buffer because it doesn’t have available a dynamically allocated string class like Delphi’s string or std::string in C++. Fixed length buffers like this often lead to buffer overruns. In Delphi don’t use a fixed length buffer if you can avoid it.

This is a classic example of why languages with built in string handling are so much easier to work with than C.