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CryptDecrypt Problem...

monsterhunter445 (2)
I've created this program that once it has found a file it can encrypt the file and then decrypt it back again when ever the user wants to decrypt the file back again. The problem or root problem may be that when the session key is exported the key's length may be incorrect, and is probably causing the decrypted text to be truncated. Can someone please help me, and I'll post the code below.

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if (LOWORD(wParam) == WORD(decrypt_id))
		{
			wchar_t filepath[256];
			GetWindowTextW(hWnd, filepath, (int)256);
			_wstat(filepath, &info4); 
			const long bytesize = info4.st_size;
			unsigned char *buffer = new unsigned char[bytesize];
			file = _wfopen(filepath, L"r");
			size_t readsize = fread(buffer, sizeof(char), info4.st_size , file);
			BOOL returnn = CryptAcquireContext(&hCryptProv, NULL, MS_ENHANCED_PROV,  PROV_RSA_FULL, 0);
			wchar_t current_username_buffer[256];
			DWORD size2 = 32767;
			wchar_t dest2[256] = L"C:\\Users\\";
			GetUserName(current_username_buffer, &size2);
			wcscat_s(dest2, current_username_buffer);
			wchar_t src[256] = L"\\Desktop\\";
			wcscat_s(dest2, src);
			wchar_t filepath2[] = L"encryptkey.bin";
			wcscat_s(dest2, filepath2);
			_wstat(dest2, &info5);
			BYTE readkey[140];
			file4 = _wfopen(dest2, L"rb");
			long lsize = ftell(file4);
			size_t readsize2 = fread(readkey, sizeof(char), info5.st_size, file4);
			BOOL rvalue1 = CryptImportKey(hCryptProv, readkey, sizeof(readkey), 0, 0, &hkey);
			DWORD datalength = info4.st_size;
			BOOL rvalue3 = CryptDecrypt(hkey, NULL, FALSE, NULL, buffer, &datalength);
			file2 = _wfopen(filepath, L"w");
			size_t writesize = fwrite(buffer, sizeof(char), sizeof(buffer), file2);
			free(buffer);
			CryptReleaseContext(hCryptProv, 0);
			CryptDestroyKey(hkey);
			if (rvalue3 == 0)
			{
				DWORD result = GetLastError();
				wchar_t dest[256] = L"Decryptor Failed To Decrypt File!";
				wcscat_s(dest, L"\n");
				wcscat_s(dest, L"Error Code: ");
				wchar_t code[256];
				swprintf_s(code, L"%d", result);
				wcscat_s(dest, code);
				wcscat_s(dest, L"\n");
				wcscat_s(dest, L"Error Code Information at: http://msdn.microsoft.com/en-us/library/ms681381(v=VS.85).aspx");
				MessageBoxW(hWnd, dest, L"Error", MB_ICONERROR | MB_OK);
				ShowWindow(encrypt_button, SW_HIDE);
			}
			else
			{
				MessageBox(hWnd, L"Successfully Decrypted The File!", L"", MB_OK | MB_ICONINFORMATION);
				ShowWindow(encrypt_button, SW_HIDE);
				BOOL result = DeleteFile(dest2); /* Deletes the binary file */
			}
		}
		if (LOWORD(wParam) == WORD(encrypt_id))
		{
			wchar_t filepath[256];
			GetWindowTextW(hWnd, filepath, (int)256);
			_wstat(filepath, &info4); 
			const long bytesize = info4.st_size;
			unsigned char *buffer = new unsigned char[bytesize];
			file = _wfopen(filepath, L"r");
			size_t readsize = fread(buffer, sizeof(char), info4.st_size , file);
			BOOL returnn = CryptAcquireContext(&hCryptProv, NULL, MS_ENHANCED_PROV,  PROV_RSA_FULL, 0);
			BOOL rvalue1 = CryptGenKey(hCryptProv, CALG_RC4, KEYLENGTH | CRYPT_EXPORTABLE, &hkey);
			DWORD datalength = info4.st_size;
			BOOL rvalue3 = CryptEncrypt(hkey, NULL, FALSE, NULL, buffer, &datalength, datalength);
			CryptGenKey( hCryptProv, AT_KEYEXCHANGE, CRYPT_EXPORTABLE, &hXchgKey);
			BYTE* key = NULL;
			DWORD len;
			CryptExportKey(hkey, hXchgKey, SIMPLEBLOB, 0, NULL, &len);
			key = new BYTE[len];
			BOOL returnval = CryptExportKey(hkey, hXchgKey, SIMPLEBLOB, NULL, key, &len);
			wchar_t current_username_buffer[256];
			DWORD size2 = 32767;
			wchar_t dest2[256] = L"C:\\Users\\";
			GetUserName(current_username_buffer, &size2);
			wcscat_s(dest2, current_username_buffer);
			wchar_t src[256] = L"\\Desktop\\";
			wcscat_s(dest2, src);
			wchar_t filepath2[] = L"encryptkey.bin";
			wcscat_s(dest2, filepath2);
			file3 = _wfopen(dest2, L"wb");
			size_t writesize2 = fwrite(key, sizeof(char), len, file3);
			SetFileAttributes(dest2, FILE_ATTRIBUTE_HIDDEN); 
			file2 = _wfopen(filepath, L"w");
			size_t writesize = fwrite(buffer, sizeof(char), sizeof(buffer), file2);
			free(buffer);
		    CryptDestroyKey(hkey);
			CryptReleaseContext(hCryptProv, 0);
			if (rvalue3 == 0)
			{
				DWORD result = GetLastError();
				wchar_t dest[256] = L"Encryptor Failed To Encrypt File!";
				wcscat_s(dest, L"\n");
				wcscat_s(dest, L"Error Code: ");
				wchar_t code[256];
				swprintf_s(code, L"%d", result);
				wcscat_s(dest, code);
				wcscat_s(dest, L"\n");
				wcscat_s(dest, L"Error Code Information at: http://msdn.microsoft.com/en-us/library/ms681381(v=VS.85).aspx");
				MessageBoxW(hWnd, dest, L"Error", MB_ICONERROR | MB_OK);
				ShowWindow(encrypt_button, SW_HIDE);
			}
			else
			{
				MessageBox(hWnd, L"Successfully Encrypted The File!", L"", MB_OK | MB_ICONINFORMATION);
				ShowWindow(encrypt_button, SW_HIDE);
			}
		}
kbw (9488)
That's pretty unreadable stuff. Have you thought about breaking it up so it's manageable?
monsterhunter445 (2)
Hope this makes it more readable because I explained each line of codes by inserting comments.

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/* Decrypts the file */
	    if (LOWORD(wParam) == WORD(decrypt_id))
		{
			wchar_t filepath[256];
			GetWindowTextW(hWnd, filepath, (int)256); /* Gets the file path of the file to decrypted from the main window's text. */
			_wstat(filepath, &info4); /* gets some important file information from the filepath */
			const long bytesize = info4.st_size; 
			unsigned char *buffer = new unsigned char[bytesize]; /* Here is dynamic memory allocation of the buffer */
			file = _wfopen(filepath, L"r"); /* opens the file that is about to be decrypted for reading */
			size_t readsize = fread(buffer, sizeof(char), info4.st_size , file); /* reads the file about to be decrypted */
			BOOL returnn = CryptAcquireContext(&hCryptProv, NULL, MS_ENHANCED_PROV,  PROV_RSA_FULL, 0); /* Acquires the cryptographic service provider*/			
			wchar_t current_username_buffer[256]; /* The buffer that recieves the current username */
			DWORD size2 = 32767;
			wchar_t dest2[256] = L"C:\\Users\\";
			GetUserName(current_username_buffer, &size2); /* Get the current username */
			wcscat_s(dest2, current_username_buffer);
			wchar_t src[256] = L"\\Desktop\\";
			wcscat_s(dest2, src);
			wchar_t filepath2[] = L"encryptkey.bin";
			wcscat_s(dest2, filepath2);
			_wstat(dest2, &info5);
			BYTE readkey[140];
			file4 = _wfopen(dest2, L"rb"); /* opens the binary file for reading, in which the binary file has the session key */
			long lsize = ftell(file4); /* gets the size of file4 */
			size_t readsize2 = fread(readkey, sizeof(char), info5.st_size, file4); /* reads the binary file */
			BOOL rvalue1 = CryptImportKey(hCryptProv, readkey, sizeof(readkey), 0, 0, &hkey); /* Gets the session key from the binary file */
			DWORD datalength = info4.st_size; 
			BOOL rvalue3 = CryptDecrypt(hkey, NULL, FALSE, NULL, buffer, &datalength); /* Decryptes the specified file */
			file2 = _wfopen(filepath, L"w"); 
			size_t writesize = fwrite(buffer, sizeof(char), sizeof(buffer), file2); /* Writes the decrypted text to the file that was encrypted. */
			free(buffer); /* Deallocates the buffer */
			CryptReleaseContext(hCryptProv, 0); /* Releases some cryptographic  service provider handle */
			CryptDestroyKey(hkey); /* Destroys the key */
			if (rvalue3 == 0)
			{
				DWORD result = GetLastError();
				wchar_t dest[256] = L"Decryptor Failed To Decrypt File!";
				wcscat_s(dest, L"\n");
				wcscat_s(dest, L"Error Code: ");
				wchar_t code[256];
				swprintf_s(code, L"%d", result);
				wcscat_s(dest, code);
				wcscat_s(dest, L"\n");
				wcscat_s(dest, L"Error Code Information at: http://msdn.microsoft.com/en-us/library/ms681381(v=VS.85).aspx");
				MessageBoxW(hWnd, dest, L"Error", MB_ICONERROR | MB_OK);
				ShowWindow(encrypt_button, SW_HIDE);
			}
			else
			{
				MessageBox(hWnd, L"Successfully Decrypted The File!", L"", MB_OK | MB_ICONINFORMATION);
				ShowWindow(encrypt_button, SW_HIDE);
				BOOL result = DeleteFile(dest2); /* Deletes the binary file */
			}
		}
		/* Encrypts the file */
		if (LOWORD(wParam) == WORD(encrypt_id))
		{
			wchar_t filepath[256];
			GetWindowTextW(hWnd, filepath, (int)256);
			_wstat(filepath, &info4); 
			const long bytesize = info4.st_size;
			unsigned char *buffer = new unsigned char[bytesize];
			file = _wfopen(filepath, L"r");
			size_t readsize = fread(buffer, sizeof(char), info4.st_size , file);
			BOOL returnn = CryptAcquireContext(&hCryptProv, NULL, MS_ENHANCED_PROV,  PROV_RSA_FULL, 0);
			BOOL rvalue1 = CryptGenKey(hCryptProv, CALG_RC4, KEYLENGTH | CRYPT_EXPORTABLE, &hkey);
			DWORD datalength = info4.st_size;
			BOOL rvalue3 = CryptEncrypt(hkey, NULL, FALSE, NULL, buffer, &datalength, datalength);
			CryptGenKey( hCryptProv, AT_KEYEXCHANGE, CRYPT_EXPORTABLE, &hXchgKey);
			BYTE* key = NULL;
			DWORD len;
			CryptExportKey(hkey, hXchgKey, SIMPLEBLOB, 0, NULL, &len);
			key = new BYTE[len];
			BOOL returnval = CryptExportKey(hkey, hXchgKey, SIMPLEBLOB, NULL, key, &len);
			wchar_t current_username_buffer[256];
			DWORD size2 = 32767;
			wchar_t dest2[256] = L"C:\\Users\\";
			GetUserName(current_username_buffer, &size2);
			wcscat_s(dest2, current_username_buffer);
			wchar_t src[256] = L"\\Desktop\\";
			wcscat_s(dest2, src);
			wchar_t filepath2[] = L"encryptkey.bin";
			wcscat_s(dest2, filepath2);
			file3 = _wfopen(dest2, L"wb");
			size_t writesize2 = fwrite(key, sizeof(char), len, file3);
			SetFileAttributes(dest2, FILE_ATTRIBUTE_HIDDEN); 
			file2 = _wfopen(filepath, L"w");
			size_t writesize = fwrite(buffer, sizeof(char), sizeof(buffer), file2);
			free(buffer);
		    CryptDestroyKey(hkey);
			CryptReleaseContext(hCryptProv, 0);
			if (rvalue3 == 0)
			{
				DWORD result = GetLastError();
				wchar_t dest[256] = L"Encryptor Failed To Encrypt File!";
				wcscat_s(dest, L"\n");
				wcscat_s(dest, L"Error Code: ");
				wchar_t code[256];
				swprintf_s(code, L"%d", result);
				wcscat_s(dest, code);
				wcscat_s(dest, L"\n");
				wcscat_s(dest, L"Error Code Information at: http://msdn.microsoft.com/en-us/library/ms681381(v=VS.85).aspx");
				MessageBoxW(hWnd, dest, L"Error", MB_ICONERROR | MB_OK);
				ShowWindow(encrypt_button, SW_HIDE);
			}
			else
			{
				MessageBox(hWnd, L"Successfully Encrypted The File!", L"", MB_OK | MB_ICONINFORMATION);
				ShowWindow(encrypt_button, SW_HIDE);
			}
		}
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