Heap allocation problems - c++

Question

I am running into memory errors when I try to run my C++ program in Visual Studio 2012. I am thinking that this code is the cause (since when I remove it, it runs fine):
void GetMachineHash(CString &strHashHex) {
CMD5 cMD5;
BYTE *szHash = (BYTE*)malloc(48);
LPBYTE szMachineNameHash, szNetworkAddressHash, szVolumeIdHash;
TCHAR szMachineId[100];
DWORD nMachineIdLen = 100;
TCHAR szNetworkAddress[13];
IP_ADAPTER_INFO *pAdapterInfo, *pAdapter = NULL;
DWORD dwRetVal = 0;
ULONG ulOutBufLen = sizeof(IP_ADAPTER_INFO);
TCHAR szVolumeId[20];
TCHAR szVolumeName[MAX_PATH];
TCHAR szFileSystemName[MAX_PATH];
DWORD dwSerialNumber = 0;
DWORD dwMaxComponentLen = 0;
DWORD dwFileSystemFlags = 0;
ZeroMemory(szHash, 48);
ZeroMemory(szMachineId, 100);
ZeroMemory(szVolumeId, 20);
ZeroMemory(szVolumeName, MAX_PATH);
ZeroMemory(szFileSystemName, MAX_PATH);
ZeroMemory(szNetworkAddress, 13);
GetComputerName(szMachineId, &nMachineIdLen);
cMD5.Calculate(szMachineId);
szMachineNameHash = cMD5.Hash();
pAdapterInfo = (IP_ADAPTER_INFO *) malloc(sizeof(IP_ADAPTER_INFO));
if (pAdapterInfo == NULL) {
TRACE(_T("Error allocating memory needed to call GetAdaptersinfo()"));
szNetworkAddressHash = NULL;
}
// Make an initial call to GetAdaptersInfo to get the necessary size into the ulOutBufLen variable
if (GetAdaptersInfo(pAdapterInfo, &ulOutBufLen) == ERROR_BUFFER_OVERFLOW) {
free(pAdapterInfo);
pAdapterInfo = (IP_ADAPTER_INFO *)malloc(ulOutBufLen);
if (pAdapterInfo == NULL) {
TRACE(_T("Error allocating memory needed to call GetAdaptersinfo()"));
szNetworkAddressHash = NULL;
}
}
if ((dwRetVal = GetAdaptersInfo(pAdapterInfo, &ulOutBufLen)) == NO_ERROR) {
pAdapter = pAdapterInfo;
while (pAdapter) {
if (pAdapter->Type != MIB_IF_TYPE_LOOPBACK) {
_stprintf_s(szNetworkAddress, 13, _T("%.2X%.2X%.2X%.2X%.2X%.2X"),
pAdapter->Address[0],
pAdapter->Address[1],
pAdapter->Address[2],
pAdapter->Address[3],
pAdapter->Address[4],
pAdapter->Address[5]
);
break;
}
pAdapter = pAdapter->Next;
}
} else {
TRACE(_T("GetAdaptersInfo() call failed"));
szNetworkAddressHash = NULL;
}
cMD5.Calculate(szNetworkAddress);
szNetworkAddressHash = cMD5.Hash();
if (GetVolumeInformation(
NULL,
szVolumeName,
sizeof(szVolumeName),
&dwSerialNumber,
&dwMaxComponentLen,
&dwFileSystemFlags,
szFileSystemName,
sizeof(szFileSystemName))) {
_stprintf_s(szVolumeId, 20, _T("%lu"), dwSerialNumber);
}
cMD5.Calculate(szVolumeId);
szVolumeIdHash = cMD5.Hash();
// Calculate hash from hashes
memcpy(szHash, szMachineNameHash, 16);
memcpy(szHash+16, szNetworkAddressHash, 16);
memcpy(szHash+32, szVolumeIdHash, 16);
cMD5.Calculate(szHash, 48);
strHashHex.Preallocate(33);
strHashHex = cMD5.HexHash();
free(szHash);
free(pAdapterInfo);
return;
}
And then if I leave the function and just remove this code:
strHashHex.Preallocate(33);
strHashHex = cMD5.HexHash();
Then it will work fine as well. So I am wondering if that is the code that's causing the memory problems, and if it is, how can I fix it?
Here's the CMD5 class (which utilizes the Windows API to generate a MD5 sum):
class CMD5
{
public:
CMD5() {
if(CryptAcquireContext(&m_hCryptProv, NULL, MS_ENHANCED_PROV, PROV_RSA_FULL, CRYPT_NEWKEYSET) == 0){
if(GetLastError() == NTE_EXISTS){
CryptAcquireContext(&m_hCryptProv, NULL, MS_ENHANCED_PROV, PROV_RSA_FULL, 0);
}
}
}
~CMD5() {
if(m_hCryptProv)
CryptReleaseContext(m_hCryptProv, 0);
m_hCryptProv = NULL;
free(m_szHash);
}
bool Calculate(LPCTSTR szText) {
DWORD dwLen = sizeof(TCHAR) * _tcslen(szText);
DWORD dwHashLen;
DWORD dwHashLenSize = sizeof(DWORD);
if (CryptCreateHash(m_hCryptProv, CALG_MD5, 0, 0, &m_hHash)) {
if (CryptHashData(m_hHash, (const BYTE*)szText, dwLen, 0)) {
if (CryptGetHashParam(m_hHash, HP_HASHSIZE, (BYTE *)&dwHashLen, &dwHashLenSize, 0)) {
if(m_szHash = (BYTE*)malloc(dwHashLen)) {
if (CryptGetHashParam(m_hHash, HP_HASHVAL, (BYTE*)m_szHash, &dwHashLen, 0)) {
CryptDestroyHash(m_hHash);
}
}
}
}
}
return false;
}
bool Calculate(const LPBYTE szText, DWORD dwLen) {
DWORD dwHashLen;
DWORD dwHashLenSize = sizeof(DWORD);
if (CryptCreateHash(m_hCryptProv, CALG_MD5, 0, 0, &m_hHash)) {
if (CryptHashData(m_hHash, (const BYTE*)szText, dwLen, 0)) {
if (CryptGetHashParam(m_hHash, HP_HASHSIZE, (BYTE *)&dwHashLen, &dwHashLenSize, 0)) {
if(m_szHash = (BYTE*)malloc(dwHashLen)) {
if (CryptGetHashParam(m_hHash, HP_HASHVAL, (BYTE*)m_szHash, &dwHashLen, 0)) {
CryptDestroyHash(m_hHash);
}
}
}
}
}
return false;
}
LPBYTE Hash() const {
LPBYTE szHash = new BYTE[16];
ZeroMemory(szHash, 16);
memcpy(szHash, m_szHash, 16);
return szHash;
}
LPTSTR HexHash() const {
LPTSTR szBuf = new TCHAR[33];
ZeroMemory(szBuf, 33);
for (int i=0; i<16; i++)
_stprintf_s(szBuf+i*2, 33, _T("%02X"), m_szHash[i]);
szBuf[32]=0;
return szBuf;
}
private:
BYTE *m_szHash;
DWORD m_hHash;
HCRYPTPROV m_hCryptProv;
};
Also, the error I get from VS2012 is Critical error detected c0000374 and the call stack ends with a call to HeapAlloc() from _heap_alloc. Not sure if it matters but this code is being called in a DLL.

Answer 1

It looks like I was able to solve the memory allocation problems by changing the CMD5::HexHash() function to
void HexHash(CString &strHash) {
for (int i=0; i<16; i++)
strHash += StringFormat(_T("%02X"), m_szHash[i]);
return;
}
and call it via cMD5.HexHash(strHashHex);