hans/worker.cpp

/*
 *  Hans - IP over ICMP
 *  Copyright (C) 2009 Friedrich Schöller <friedrich.schoeller@gmail.com>
 *  
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *  
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *  
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *  
 */

#include "worker.h"
#include "tun.h"
#include "exception.h"
#include "config.h"

#include <string.h>
#include <syslog.h>

using namespace std;

Worker::TunnelHeader::Magic::Magic(const char *magic)
{
	memset(data, 0, sizeof(data));
	strncpy(data, magic, sizeof(data));
}

bool Worker::TunnelHeader::Magic::operator==(const Magic &other) const
{
	return memcmp(data, other.data, sizeof(data)) == 0;
}

bool Worker::TunnelHeader::Magic::operator!=(const Magic &other) const
{
	return memcmp(data, other.data, sizeof(data)) != 0;
}

Worker::Worker(int tunnelMtu, const char *deviceName, bool answerEcho, uid_t uid, gid_t gid)
{
	this->tunnelMtu = tunnelMtu;
	this->answerEcho = answerEcho;
	this->uid = uid;
	this->gid = gid;
	this->privilegesDropped = false;

	echo = NULL;
	tun = NULL;

	try
	{
		echo = new Echo(tunnelMtu + sizeof(TunnelHeader));
		tun = new Tun(deviceName, tunnelMtu);
	}
	catch (...)
	{
		delete echo;
		delete tun;

		throw;
	}
}

Worker::~Worker()
{
	delete echo;
	delete tun;
}

void Worker::sendEcho(const TunnelHeader::Magic &magic, int type, int length, uint32_t realIp, bool reply, uint16_t id, uint16_t seq)
{
	if (length > payloadBufferSize())
		throw Exception("packet too big");

	TunnelHeader *header = (TunnelHeader *)echo->sendPayloadBuffer();
	header->magic = magic;
	header->type = type;

	DEBUG_ONLY(printf("sending: type %d, length %d, id %d, seq %d\n", type, length, id, seq));

	echo->send(length + sizeof(TunnelHeader), realIp, reply, id, seq);
}

void Worker::sendToTun(int length)
{
	tun->write(echoReceivePayloadBuffer(), length);
}

void Worker::setTimeout(Time delta)
{
	nextTimeout = now + delta;
}

void Worker::run()
{
	now = Time::now();
	alive = true;

	int maxFd = echo->getFd() > tun->getFd() ? echo->getFd() : tun->getFd();

	while (alive)
	{
		fd_set fs;
		Time timeout;

		FD_ZERO(&fs);
		FD_SET(tun->getFd(), &fs);
		FD_SET(echo->getFd(), &fs);

		if (nextTimeout != Time::ZERO)
		{
			timeout = nextTimeout - now;
			if (timeout < Time::ZERO)
				timeout = Time::ZERO;
		}

		// wait for data or timeout
		int result = select(maxFd + 1 , &fs, NULL, NULL, nextTimeout != Time::ZERO ? &timeout.getTimeval() : NULL);
		if (result == -1)
			throw Exception("select", true);
		now = Time::now();

		// timeout
		if (result == 0)
		{
			nextTimeout = Time::ZERO;
			handleTimeout();
			continue;
		}

		// icmp data
		if (FD_ISSET(echo->getFd(), &fs))
		{
			bool reply;
			uint16_t id, seq;
			uint32_t ip;

			int dataLength = echo->receive(ip, reply, id, seq);
			if (dataLength != -1)
			{
				bool valid = dataLength >= sizeof(TunnelHeader);

				if (valid)
				{
					TunnelHeader *header = (TunnelHeader *)echo->receivePayloadBuffer();

					DEBUG_ONLY(printf("received: type %d, length %d, id %d, seq %d\n", header->type, dataLength - sizeof(TunnelHeader), id, seq));

					valid = handleEchoData(*header, dataLength - sizeof(TunnelHeader), ip, reply, id, seq);
				}

				if (!valid && !reply && answerEcho)
				{
					memcpy(echo->sendPayloadBuffer(), echo->receivePayloadBuffer(), dataLength);
					echo->send(dataLength, ip, true, id, seq);
				}
			}
		}

		// data from tun
		if (FD_ISSET(tun->getFd(), &fs))
		{
			uint32_t sourceIp, destIp;

			int dataLength = tun->read(echoSendPayloadBuffer(), sourceIp, destIp);

			if (dataLength == 0)
				throw Exception("tunnel closed");

			handleTunData(dataLength, sourceIp, destIp);
		}
	}
}

void Worker::dropPrivileges()
{
	if (uid <= 0 || privilegesDropped)
		return;

	syslog(LOG_INFO, "dropping privileges");

	if (setgid(gid) == -1)
		throw Exception("setgid", true);

	if (setuid(uid) == -1)
		throw Exception("setuid", true);

	privilegesDropped = true;
}