/**
* Creates new connection to OTServ administration backend.
*
* <p>
* This method automaticly handles RSA and XTEA encryption if such method is required by server including keys negotiations.
* </p>
*
* <p>
* After connecting you should check {@link OTS_Admin::requiresLogin() if server requires login}.
* </p>
*
* @version 0.1.2
* @since 0.1.2
* @param string $host Target server.
* @param int $port Port (7171 by default).
* @throws E_OTS_ErrorCode When receive failed respond or unexpected message.
* @throws E_OTS_OutOfBuffer When there is read attemp after end of packet stream.
*/
public function __construct($host, $port = 7171)
{
// saves connection sessint
$this->host = $host;
$this->port = $port;
// opens connection
$this->socket = fsockopen($this->host, $this->port);
// 254 = OTAdmin protocol identifier
$message = new OTS_Buffer(chr(254));
// sends initial packet
$respond = $this->send($message);
$message->reset();
$byte = $respond->getChar();
// checks if it's HELLO packet
if ($byte != self::RESPOND_HELLO) {
throw new E_OTS_ErrorCode($byte);
}
// skips respond signature and protocol version
$respond->getLong();
$respond->getString();
// saves protocol settings
$this->policy = $respond->getShort();
$this->options = $respond->getLong();
// handles encryption initialisation if required
if ($this->requiresEncryption() && $this->usesRSA1024XTEA()) {
// requests public key
$message->putChar(self::REQUEST_KEY_EXCHANGE);
$message->putChar(self::ENCRYPTION_RSA1024XTEA);
$respond = $this->send($message);
$message->reset();
$byte = $respond->getChar();
// checks if it succeded
if ($byte != self::RESPOND_KEY_EXCHANGE_OK) {
throw new E_OTS_ErrorCode($byte, $respond->getString());
}
// we support only RSA 1024bit encryption for XTEA key sending
if ($respond->getChar() != self::ENCRYPTION_RSA1024XTEA) {
throw new E_OTS_ErrorCode($byte);
}
// reads binary form of public key (128 bytes)
$key = OTS_BinaryTools::bin2Int(strrev($respond->getString(128)));
// creates RSA cipher
// as we have ready N computer here and we don't compute it by ourselves we can use a little hack, to save N as P * Q we will use P = N and Q = 1
$rsa = new OTS_RSA($key, '1');
$key = '';
// generates random XTEA key
for ($i = 0; $i < 4; $i++) {
$key .= pack('L', rand(0, 4294967295));
}
$xtea = new OTS_XTEA($key);
// sends XTEA key
$message->putChar(self::REQUEST_ENCRYPTION);
$message->putChar(self::ENCRYPTION_RSA1024XTEA);
$message->putString($rsa->encrypt(chr(0) . $key), false);
// we can't bind cipher yet since only respnd will be XTEA encrypted
$respond = new OTS_Buffer($xtea->decrypt($this->send($message)->getBuffer()));
$byte = $respond->getChar();
// checks if encryption negotation succeeded
if ($byte != self::RESPOND_ENCRYPTION_OK) {
throw new E_OTS_ErrorCode($byte, $respond->getString());
}
// saves encryption/decryption cipher
$this->cipher = $xtea;
}
}
/**
* Ecnrypts message with RSA algorithm.
*
* @version 0.1.2
* @since 0.1.2
* @param string $message Message to be encrypted.
* @return string Encrypted message.
*/
public function encrypt($message)
{
// chunk length
$length = ceil($this->length / 8);
// c = m^e mod n
return str_pad(strrev(OTS_BinaryTools::int2Bin(bcpowmod(OTS_BinaryTools::bin2Int(strrev(str_pad($message, $length, chr(0)))), $this->e, $this->n))), $length, chr(0), STR_PAD_LEFT);
}
/**
* Decrypt XTEA-encrypted string.
*
* @param string $message Encrypted message.
* @return string Decrypted string.
*/
public function decrypt($message)
{
// convert data to long
$message = array_values(unpack('V*', $message));
$length = count($message);
// converts to unsigned integers
foreach ($message as $index => $result) {
if ($result < 0) {
$message[$index] += 0xffffffff + 1;
}
}
// decrypt the long data with the key
$result = '';
for ($i = 0; $i < $length; $i++) {
$sum = 0xc6ef3720;
$delta = 0x61c88647;
$y = $message[$i];
$z = $message[++$i];
for ($j = 0; $j < 32; $j++) {
$z = OTS_BinaryTools::unsignedAdd($z, -(OTS_BinaryTools::unsignedAdd($y << 4 ^ OTS_BinaryTools::unsignedRightShift($y, 5), $y) ^ OTS_BinaryTools::unsignedAdd($sum, $this->key[OTS_BinaryTools::unsignedRightShift($sum, 11) & 3])));
$sum = OTS_BinaryTools::unsignedAdd($sum, $delta);
$y = OTS_BinaryTools::unsignedAdd($y, -(OTS_BinaryTools::unsignedAdd($z << 4 ^ OTS_BinaryTools::unsignedRightShift($z, 5), $z) ^ OTS_BinaryTools::unsignedAdd($sum, $this->key[$sum & 3])));
}
// append the deciphered longs to the result data
$result .= pack('VV', $y, $z);
}
// reads message length
$offset = unpack('v', $result);
return substr($result, 2, $offset[1]);
}
