crypt.cpp

#include "stdafx.h"

#include <Wincrypt.h>
#include <sstream>

std::string GetHashText(const void * data, const size_t data_size, HashType hashType)
{
	HCRYPTPROV hProv = NULL;

	if (!CryptAcquireContext(&hProv, NULL, NULL, PROV_RSA_AES, CRYPT_VERIFYCONTEXT)) {
		return "";
	}

	BOOL hash_ok = FALSE;
	HCRYPTPROV hHash = NULL;
	switch (hashType) {
	case HashSha1: hash_ok = CryptCreateHash(hProv, CALG_SHA1, 0, 0, &hHash); break;
	case HashMd5: hash_ok = CryptCreateHash(hProv, CALG_MD5, 0, 0, &hHash); break;
	case HashSha256: hash_ok = CryptCreateHash(hProv, CALG_SHA_256, 0, 0, &hHash); break;
	}

	if (!hash_ok) {
		CryptReleaseContext(hProv, 0);
		return "";
	}

	if (!CryptHashData(hHash, static_cast<const BYTE *>(data), data_size, 0)) {
		CryptDestroyHash(hHash);
		CryptReleaseContext(hProv, 0);
		return "";
	}

	DWORD cbHashSize = 0, dwCount = sizeof(DWORD);
	if (!CryptGetHashParam(hHash, HP_HASHSIZE, (BYTE *)&cbHashSize, &dwCount, 0)) {
		CryptDestroyHash(hHash);
		CryptReleaseContext(hProv, 0);
		return "";
	}

	std::vector<BYTE> buffer(cbHashSize);
	if (!CryptGetHashParam(hHash, HP_HASHVAL, reinterpret_cast<BYTE*>(&buffer[0]), &cbHashSize, 0)) {
		CryptDestroyHash(hHash);
		CryptReleaseContext(hProv, 0);
		return "";
	}

	std::ostringstream oss;

	for (std::vector<BYTE>::const_iterator iter = buffer.begin(); iter != buffer.end(); ++iter) {
		oss.fill('0');
		oss.width(2);
		oss << std::hex << static_cast<const int>(*iter);
	}

	CryptDestroyHash(hHash);
	CryptReleaseContext(hProv, 0);
	return oss.str();
}