Manoj Jangid <>
Thu, 25 Dec 2008 20:53:55 -0800 (PST)
On Dec 25, 2:22 am, Joseph M. Newcomer <> wrote:

See below...

On Wed, 24 Dec 2008 01:43:01 -0800 (PST), Manoj Jangid <manoj.jan...@gmai=> wrote:

Hi I am calling a function from MFC dll in C# application.
This function work with C++ application but when I was calling from C#
application terminates unexpectedly.

can anyone tell me why this happening?

I am pasting my source code here
C# code
       private void button1_Click(object sender, EventArgs e)
           string strPassWord = textBox1.Text;
           string strHash = "";
           PasswordHash(strPassWord,ref strHash);

PasswordHash function in my MFC regular statically linked to MFC dll
C++ code

bool __stdcall PasswordHash(LPCTSTR lpPasswor=

d, LPTSTR lpszHash)


This is REALLY SCARY code. It has an LPTSTR and no explicit length is =

specified, nor is

there any way to determine if the caller actually gave you a buffer that =

is large enough.

This is a MAJOR security hole! This is extremely unsafe code.
****> AFX_MANAGE_STATE(AfxGetStaticModuleState());

   CString strPassword(lpPassword);
   bool bReturn = false;
   HCRYPTPROV hCryptProv;
   BYTE pbHash[16];
   DWORD dwHashLen= 16;

Why use 16 twice? Consider using a #define or static const UINT to def=

ine this and use

the symbolic name
****> DWORD cbContent= strPassword.GetLength() * sizeof(TCHAR);

   BYTE* pbContent= (BYTE *) strPassword.GetBuffer(cbContent);

   if(CryptAcquireContext(&hCryptProv, NULL, NULL, PROV_RSA_FULL,
if(CryptCreateHash(hCryptProv,CALG_MD5,0, 0, &hHash))
if(CryptHashData(hHash, pbContent, cbContent, 0))
if(CryptGetHashParam(hHash, HP_HASHVAL, pbHash, &dwHashLen, 0))
LPTSTR lpTmp = lpszHash;
for (int i = 0; i < 16; i++)

Another use of 16. That's three times too many

const size_t nlen = sizeof(pbHash[i])+2;

Why is this sizeof(pbHash[i])? Note that sizeof(pbHash[i]) *always* ha=

s to be 1. And

what's the magic "+2" term for?


This is even scarier. You are writing to the output buffer, whose leng=

th is unknown, by

claiming that it is big enough. Yet the computation is erroneous. I=

n ANSI, it computes

the nlen term to be 1+2, or 3, but it only needs to be 2; in Unicode apps=

, it computes the

nlen term to be 1+2, or 3, but it needs to be 2 (characters) which is 4 b=

ytes. There's a

lot of confusion here about how to use _stprintf_s. That length is not=

 computed based on

what you THINK might be available, but what the input parameters TELL you=

 is available.

What input parameter? Well, that's a serious design error. There is=

n't one.>lpTmp += 2;

You are advancing the pointer, but where is the bounds check. The corr=

ect code would be

int nlen = Length; // copy parameter to nlen
for(int i = 0; i < MAX_KEY_SIZE; i++)
    _stprintf_s(lpTmp, nlen, _T("%02X"), pbHash[i]);
    lpTmp += 2;

This will avoid a buffer overrun. Your code could clobber arbitrary am=

ounts of data (and

don't say "I know the output buffer is big enough" unless you also want t=

o say "and I

understand that secure code never relies on rumors but always passes in a=

 length, and

failure to do so can be cause for termination in many companies, but secu=

rity doesn't

matter. I like seeing our name in headlines."

bReturn = true;

Have you noticed that code that is not indented is hard to read?

CryptReleaseContext(hCryptProv, 0);
return bReturn;


here problem in my for loop

LPTSTR lpTmp = lpszHash;
for (int i = 0; i < 16; i++)
       const size_t nlen = sizeof(pbHash[i])+2;
       lpTmp += 2;
//Application will terminates when i=13
whats wrong in this loop I also try this with _stprintf (non secure
version) same problem each time only when I am trying to call in C#


Additional Information: The runtime has encountered a fatal error. The
address of the error was at 0x79ee24f1, on thread 0x10c4. The error
code is 0xc0000005. This error may be a bug in the CLR or in the
unsafe or non-verifiable portions of user code. Common sources of this
bug include user marshaling errors for COM-interop or PInvoke, which
may corrupt the stack.

The thread 'Win32 Thread' (0x1478) has exited with code -1073740791
The thread 'Win32 Thread' (0x854) has exited with code -1073740791
The thread 'Win32 Thread' (0x13e4) has exited with code -1073740791
The program '[6076] CryptClient.exe: Managed' has exited with code
-1073740791 (0xc0000409).
The program '[6076] CryptClient.exe: Native' has exited with code
-1073740791 (0xc0000409).

Kind Regards

Joseph M. Newcomer [MVP]
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Thank you Joseph,

I know code quality is not good, this code is written long back by
some other guy,
I,ll change the code according your suggestion.

Thanks again

Manoj Jangid

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