notepad++ nppftp decryption routine

stuff.cpp

// Encryption.cpp
#include <openssl/des.h>

char * Encryption::_DefaultKey = NULL;
bool Encryption::_IsDefaultKey = true;
const char * defaultString = "NppFTP00";	//must be 8 in length
const size_t Encryption::KeySize = 8;

int Encryption::Init() {
	_DefaultKey = new char[KeySize];
	strncpy(_DefaultKey, defaultString, KeySize);
	return 0;
}

char* Encryption::Decrypt(const char * key, int keysize, const char * data, bool addZero) {
	int size = strlen(data);
	char * encrdata = SU::HexToData(data, size, false);
	if (!encrdata)
		return NULL;

	size = size/2;
	char * decdata = DES_encrypt(key, keysize, encrdata, size, addZero, DES_DECRYPT);
	SU::FreeChar(encrdata);

	return decdata;
}

char* Encryption::DES_encrypt(const char * key, int keysize, const char * data, int size, bool addZero, int type) {
	char keybuf[KeySize];
	if (key == NULL) {
		memcpy(keybuf, _DefaultKey, KeySize);
		keysize = KeySize;
	} else {
		if (keysize == -1)
			keysize = strlen(key);	//zero terminator NOT included
		if (keysize > KeySize)
			keysize = KeySize;
		memcpy(keybuf, key, keysize);
		for(size_t i = keysize; i < KeySize; i++)
			keybuf[i] = 0;
	}

	if (size == -1)
		size = strlen(data);

	char * decrypted = new char[size+(addZero?1:0)];
	if (!decrypted)
		return NULL;

	if (addZero)
		decrypted[size] = 0;

	// Prepare the key for use with DES_cfb64_encrypt
	DES_cblock key2;
	DES_key_schedule schedule;
	memcpy(key2, keybuf, KeySize);
	DES_set_odd_parity(&key2);
	DES_set_key_checked(&key2, &schedule);

	// Decryption occurs here
	int n = 0;
	DES_cfb64_encrypt((unsigned char*) data, (unsigned char *)decrypted, size, &schedule, &key2, &n, type);

	return decrypted;
}


// StringUtils.cpp
char* SU::HexToData(const char * hex, int len, bool addZero) {
	if (len == -1)
		len = strlen(hex);

	if (len%2 != 0)
		return NULL;

	len = len/2;
	unsigned char * data = new unsigned char[len + (addZero?1:0)];

	for(int i = 0; i < len; i++) {
		data[i] = 0;

		if (hex[i*2] <= '9')
			data[i] += (hex[i*2] - '0') * 16;
		else
			data[i] += ((hex[i*2] - 'A') + 10) * 16;

		if (hex[i*2+1] <= '9')
			data[i] += (hex[i*2+1] - '0');
		else
			data[i] += (hex[i*2+1] - 'A') + 10;
	}

	if (addZero) {
		data[len] = 0;
	}

	return (char*)data;
}


int SU::FreeChar(char * string) {
	if (!string)
		return -1;

	delete [] string;
	return 0;
}