C / C++ / MFC

Re: calling a function multple times, clears previous values

20-Dec-11 17:14

I'm sure this is c++ 101

I build a class to encrypt and decrypt, but when I use the function multiple times, it changes the values of the previous buffers I stored the values in.

This is the first time I have called a function multiple times, so I'm not sure how to handle it.

CA_Encryption caEncrypt;
WCHAR *szSecretAnwser_Secure = 	new WCHAR[12];
szSecretAnwser_Secure = caEncrypt._encrypt_3DES(szSecretAnwser);
			
WCHAR *szPassword_Secure = new WCHAR[12];
szPassword_Secure = caEncrypt._encrypt_3DES(szPassword);
			
// Convert the Password to a hash
const int MD5_SIZE = 16;
BYTE *szPassword_Encoded = new BYTE[MD5_SIZE];			
szPassword_Encoded = caEncrypt._create_MD5_Hash(szPassword);

Richard MacCutchan20-Dec-11 21:46

Richard MacCutchan

20-Dec-11 21:46

I'm not sure where this code actually exists as you have not shown where in the function it is, or really what it is trying to do. however when you allocate a buffer with a new operator it creates a new buffer every time you pass that line of code (you should also delete[] them when finished with). If you want some permanent buffer then you should allocate it outside the function and pass it in as a reference on the function call. Something like:

C++

int myfunc(buffer* pszBuffer)
{
// fill buffer with information
    return 1;
}

char* nbuff = new char[64];
int val = myfunc(nbuff);
// do other things
delete[] nbuff; // finished with this buffer

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Re: calling a function multple times, clears previous values

jkirkerx21-Dec-11 6:16

Re: calling a function multple times, clears previous values

21-Dec-11 6:16

I didn't want to post the function because I had no idea where my poor use of buffers was. I made a class, and wrote 5 functions in it.

Normally I would of wrote 5 public functions, and do the work in private functions.

But no matter which function I run in the same class, it changes the previous buffer values to the last function ran in the class.

I think I understand now why everyone had there encryption function separated into 3 aspects.

Let me try that first.

David Crow21-Dec-11 2:38

David Crow

21-Dec-11 2:38

jkirkerx wrote:
I build a class to encrypt and decrypt, but when I use the function multiple times, it changes the values of the previous buffers I stored the values in.

What does _encrypt_3DES() look like? I don't need all of the details, just the variable that it returns and how it is declared.

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Re: calling a function multple times, clears previous values

jkirkerx21-Dec-11 6:23

Re: calling a function multple times, clears previous values

21-Dec-11 6:23

I just finished these,

Encrypt 3DES

WCHAR*	CA_Encryption::_encrypt_3DES( WCHAR *pzInputW )
{
BOOL			bResult = FALSE;
WCHAR			*szOutput = NULL;
 
HCRYPTPROV		hProv;
HCRYPTKEY		hKey;
ALG_ID			Algid;
PBYTE			pbKeyBlob = NULL; 
BYTE			*pbBuffer;
DWORD			dwBlockLen = 0;
DWORD			dwDataLen = 0;
DWORD			cbData = 0;
BOOL			bFinal = TRUE;
DWORD			errorCode = 0;

DWORD			dwResult = 0;
TCHAR			szBase64[80];
DWORD			cbKeyLen = 24;
	 
// Get the size of the conversion first
int iCharA = WideCharToMultiByte(CP_UTF8, 0, pzInputW, -1, NULL, 0, NULL, NULL);	
char *szInputA = new char[iCharA];
WideCharToMultiByte(CP_UTF8, 0, pzInputW, -1, szInputA, iCharA, NULL, NULL);

keyBlob192.hdr.bType = PLAINTEXTKEYBLOB;
keyBlob192.hdr.bVersion = CUR_BLOB_VERSION;
keyBlob192.hdr.reserved = 0;
keyBlob192.hdr.aiKeyAlg = CALG_3DES;
keyBlob192.cbKeySize = 24;
ZeroMemory(keyBlob192.rgbKeyData, 24);
CopyMemory(keyBlob192.rgbKeyData, KEY_192, cbKeyLen > 24 ? 24 : cbKeyLen);
			
bResult = CryptAcquireContextW( &hProv, 0, MS_ENHANCED_PROV, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
bResult = CryptImportKey(hProv, (BYTE*)&keyBlob192, sizeof(keyBlob192), 0, CRYPT_EXPORTABLE, &hKey);	
bResult = CryptSetKeyParam(hKey, KP_IV, IV_64, 0);
		
dwDataLen = sizeof(ALG_ID);
cbData = sizeof(szInputA);	

if (!CryptGetKeyParam(hKey, KP_ALGID, (BYTE *)&Algid, &dwDataLen, 0)) 
	return 0;
	
if (GET_ALG_TYPE(Algid) != ALG_TYPE_STREAM) {		
	dwDataLen = sizeof(DWORD);		
	if (!CryptGetKeyParam(hKey, KP_BLOCKLEN, (BYTE *)&dwBlockLen, &dwDataLen, 0))
	  return 0;		
	dwDataLen = ((cbData + dwBlockLen - 1) / dwBlockLen) * dwBlockLen;		
	if (!(pbBuffer = (BYTE *)LocalAlloc(LMEM_FIXED, dwDataLen))) 
		return 0;
	} 
	else {
		if (!(pbBuffer = (BYTE *)LocalAlloc(LMEM_FIXED, cbData))) 
			return 0;
	}	  
	CopyMemory(pbBuffer, szInputA, cbData);
	if (!CryptEncrypt(hKey, 0, bFinal, 0, pbBuffer, &cbData, dwDataLen)) {
		DWORD dwError = GetLastError();		
		if(ERROR_MORE_DATA == dwError) {
			DWORD dwSizeNeeded = cbData;
			CopyMemory( pbBuffer, szInputA, cbData );
			bResult = CryptEncrypt(hKey, 0, FALSE, 0, pbBuffer, &dwSizeNeeded, dwDataLen);
		}			
		LocalFree(pbBuffer);
		return 0;
}	
	
if(CryptBinaryToString(pbBuffer, 8, CRYPT_STRING_BASE64, NULL, &dwResult)) {		
	CryptBinaryToString(pbBuffer, 8, CRYPT_STRING_BASE64, szBase64, &dwResult);
	szBase64[dwResult] = 0;
	szOutput = (WCHAR*)szBase64;
	szOutput[wcslen(szOutput)+1] = L'\0';
}	

// Secure sensitive data in buffers
SecureZeroMemory( keyBlob64.rgbKeyData, 8 );
SecureZeroMemory( pbBuffer, sizeof(pbBuffer) );
	
// Clean up the garbage in the heap
delete [] szInputA;

CryptDestroyKey(hKey);
CryptReleaseContext(hProv, 0);	
	
return szOutput;
}

Hash

BYTE* CA_Encryption::_create_MD5_Hash( WCHAR *pzInputW )
{
BOOL			bResult = FALSE;
HCRYPTPROV		hProv;
HCRYPTHASH		hHash;

const int		MD5_SIZE = 16;
static BYTE		hash[MD5_SIZE];
DWORD			hash_size = sizeof(hash);	
			
// Get the size of the conversion
int iChar = WideCharToMultiByte(CP_UTF8, 0, pzInputW, -1, NULL, 0, NULL, NULL);	
char *szInputA = new char[iChar];
WideCharToMultiByte(CP_UTF8, 0, pzInputW, -1, szInputA, iChar, NULL, NULL);
		
DWORD		dwBufferSize = 0;	
DWORD		dwPasswordLen = strlen((char *)szInputA);	
		
bResult = CryptAcquireContextW( &hProv, NULL, MS_STRONG_PROV, PROV_RSA_FULL, 0);	
bResult = CryptCreateHash( hProv, CALG_MD5, 0, 0, &hHash );   
bResult = CryptHashData( hHash, (BYTE*)szInputA, dwPasswordLen, 0 );
	
// Now get the value
bResult = CryptGetHashParam( hHash, HP_HASHVAL, hash, &hash_size, 0 );
		
// Release hash object.
delete [] szInputA;
CryptDestroyHash(hHash);
CryptReleaseContext(hProv, 0);
		    	
return hash;
}

David Crow21-Dec-11 7:54

David Crow

21-Dec-11 7:54

As I suspected, szOutput is an auto (i.e., local) variable. Under the right conditions, it will point to szBase64, another auto variable. It sounds as though you need to call _encrypt_3DES() with an additional argument: a buffer to store the result in.

Re: calling a function multple times, clears previous values

jkirkerx21-Dec-11 8:15

21-Dec-11 8:15

Thanks for checking it out Dave.

I even experimented with changing the name of szOutput to unique names, but it still did the same thing.

I think that's why all the examples I saw had the base64 part in a separate function.

Much better now

jkirkerx23-Dec-11 12:48

23-Dec-11 12:48

Thanks for your help. You were right on the money.

I learned alot on this one. Sort of like the post above this one. When you allocate memory, you have to have the exact right size including the null terminator.

So now I call it twice, once to get the size I need, and again with the right size.

I still have 1 bug left, I get 2 extra spaces in the SQL database column that are squares, I may have double null terminators or something. The -2 was just an experiment.

DWORD dwSecretAnwser;
caEncrypt._encrypt_3DES(szSecretAnwser, dwSecretAnwser);
WCHAR *szSecretAnwser_Secure = 	new WCHAR[dwSecretAnwser];
szSecretAnwser_Secure = caEncrypt._encrypt_3DES(szSecretAnwser, dwSecretAnwser);

WCHAR* CA_Encryption::_encrypt_3DES( WCHAR *pzInputW, DWORD &dwOutput )
{
	BOOL			bResult = FALSE;
	 
	HCRYPTPROV		hProv;
	HCRYPTKEY		hKey;
	ALG_ID			Algid;
	PBYTE			pbKeyBlob = NULL; 
    BYTE			*pbBuffer;
	DWORD			dwBlockLen = 0;
	DWORD			dwDataLen = 0;
	DWORD			cbData;
	BOOL			bFinal = TRUE;
	DWORD			errorCode = 0;
	TCHAR			*szBase64 = NULL;
	DWORD			dwResult;
	DWORD			cbKeyLen = sizeof(KEY_192);
	 
	// Get the size of the conversion first
	int iCharA = (WideCharToMultiByte(CP_UTF8, 0, pzInputW, -1, NULL, 0, NULL, NULL) - 1);	
	char *szInputA = new char[iCharA];
	WideCharToMultiByte(CP_UTF8, 0, pzInputW, -1, szInputA, iCharA, NULL, NULL);
		
	keyBlob192.hdr.bType = PLAINTEXTKEYBLOB;
	keyBlob192.hdr.bVersion = CUR_BLOB_VERSION;
	keyBlob192.hdr.reserved = 0;
	keyBlob192.hdr.aiKeyAlg = CALG_3DES;
	keyBlob192.cbKeySize = sizeof(KEY_192);
	CopyMemory(keyBlob192.rgbKeyData, KEY_192, cbKeyLen>  sizeof(keyBlob192) ? sizeof(keyBlob192) : cbKeyLen);
			
	bResult = CryptAcquireContextW( &hProv, 0, MS_ENHANCED_PROV, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
	bResult = CryptImportKey(hProv, (BYTE*)&keyBlob192, sizeof(keyBlob192), 0, CRYPT_EXPORTABLE, &hKey);	
	bResult = CryptSetKeyParam(hKey, KP_IV, IV_192, 0);
		
	dwDataLen = sizeof(ALG_ID);
	cbData = iCharA;

	if (!CryptGetKeyParam(hKey, KP_ALGID, (BYTE *)&Algid, &dwDataLen, 0)) 
		return 0;
	
	if (GET_ALG_TYPE(Algid) != ALG_TYPE_STREAM) {		
		dwDataLen = sizeof(DWORD);		
		if (!CryptGetKeyParam(hKey, KP_BLOCKLEN, (BYTE *)&dwBlockLen, &dwDataLen, 0))
		  return 0;		
		dwDataLen = ((cbData + dwBlockLen - 1) / dwBlockLen) * dwBlockLen;		
		if (!(pbBuffer = (BYTE *)LocalAlloc(LMEM_FIXED, dwDataLen))) 
			return 0;
		} 
		else {
			if (!(pbBuffer = (BYTE *)LocalAlloc(LMEM_FIXED, cbData))) 
				return 0;
		}	  
		CopyMemory(pbBuffer, szInputA, cbData);
		if (!CryptEncrypt(hKey, 0, bFinal, 0, pbBuffer, &cbData, dwDataLen)) {
			LocalFree(pbBuffer);
			return 0;
	}

	// Secure sensitive data in buffers
	SecureZeroMemory( keyBlob192.rgbKeyData, sizeof(keyBlob192.rgbKeyData) );
		
	// Clean up the garbage in the heap
	delete [] szInputA;
	CryptDestroyKey(hKey);
	CryptReleaseContext(hProv, 0);	

	if(CryptBinaryToString((BYTE*)pbBuffer, cbData, CRYPT_STRING_BASE64, NULL, &dwResult)) {		
		if  ((dwOutput > 0 ) && (dwOutput < 4096)) {
			szBase64 = new TCHAR[dwResult];
			CryptBinaryToString((BYTE*)pbBuffer, cbData, CRYPT_STRING_BASE64, szBase64, &dwResult);
			dwOutput = dwResult;
			szBase64[dwResult-2] = 0;
			return szBase64;
		}
		else {			
			dwOutput = dwResult;
			return L'\0';
		}				
	}
	else {
		dwOutput = dwResult;
		return L'\0';
	}	
}

16 bit C Compiler

softwaremonkey19-Dec-11 23:40

19-Dec-11 23:40

Hi,

Does anyone know of a compiler that will run under Windows 7 (64 bit) but will compile 16 bit DOS based code? I used to use MSVC 1.52 on XP 32 bit but it will not run on a 64 bit platform. I tried running it under Virtual PC but it is too unstable (it regularly deleted the contents of my source files which is not much fun).

Thanks Thumbs Up | :thumbsup:

CPallini19-Dec-11 23:55

CPallini

19-Dec-11 23:55

A quick search gives promising results for running Turbo C using DOSBox: I've not tried that, however.

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

User 742933820-Dec-11 8:12

User 7429338

20-Dec-11 8:12

I don't often use Windows 7 so I might be wrong on this, but as far as I know it comes with a built in 32 bit Windows XP virtual machine? MSVC 1.52 might work in that.

Personally I use Microsoft C 6.0 in DosBox[^] and MSVC 1.52 in a Windows 2000 guest OS with VirtualBox[^], both works.

modified 13-Sep-18 21:01pm.

softwaremonkey20-Dec-11 8:23

20-Dec-11 8:23

Thanks for the reply.

Win 7/64 Pro does come with XP virtual machine but unfortunately I only have the Home edition which does not. I thought about upgrading but its too much hassle re-installing everything.

I have a copy of Microsoft C 6.0 somewhere so I think I will give that a go in DosBox.

Can you advise how I install it in DosBox please.

Thanks for the tip. Thumbs Up | :thumbsup:

Richard MacCutchan20-Dec-11 21:40

Richard MacCutchan

20-Dec-11 21:40

You can download the VM from here[^].

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Richard Andrew x6422-Dec-11 10:24

Richard Andrew x64

22-Dec-11 10:24

softwaremonkey wrote:
I thought about upgrading but its too much hassle re-installing everything.

Upgrading from Home 7 to Pro 7 does not require you to reinstall a thing. All it does, essentially, is replace what's in the Windows folder with the upgraded components, and leave the registry and all program files intact.

The difficult we do right away...
...the impossible takes slightly longer.

softwaremonkey23-Dec-11 5:34

23-Dec-11 5:34

Hi Richard,

Thanks for this info. This only applies if you buy the Windows 7 Anytime Upgrade. Even though I have a copy of Windows 7 professional, it will not perform the upgrade - unless anyone knows differently.

Thanks again

Tony Thumbs Up | :thumbsup:

modified 23-Dec-11 11:51am.

Richard Andrew x6423-Dec-11 6:40

Richard Andrew x64

23-Dec-11 6:40

Your Product key from your boxed Pro 7 will work as an Anytime Upgrade key. I did that myself on a new netbook I had purchased with Win 7 Starter.

I chose the Anytime Upgrade, and put in my boxed Win 7 product key, and everything went through.

So you're not out of luck.

Rich

The difficult we do right away...
...the impossible takes slightly longer.

Software_Developer20-Dec-11 8:30

Software_Developer

20-Dec-11 8:30

Try [Microsoft QuickC 16 Bit] IDE/Compiler for the C programming language. Its main competitor was Turbo C. (Quick C vs Turbo C , get it? Cool | :cool:

), Its from the year 1990.

[This] link mentions this:

Emulation
The easiest way to get Turbo C/C++ to run is using DOSBOX which emulates the environment of an old 16bit MsDOS computer. This works very well and will allow you to run most programs (even CGA/VGA/SVGA graphics).
If you wish to run Turbo C on Linux there is DOSEMU.

Virtualization
Another option is to run the programs on a Virtual Machine. Think of this as running a virtual computer on your computer. The VM emulates a PC and you can load an OS like an old copy of windows (if you have old disks laying about) or you can use FreeDOS as an OS.

softwaremonkey23-Dec-11 5:57