dissertation-2-code/config/builder.go

package config

import (
	"encoding/base64"
	"fmt"
	"mpbl3p/crypto"
	"mpbl3p/crypto/sharedkey"
	"mpbl3p/flags"
	"mpbl3p/proxy"
	"mpbl3p/tcp"
	"mpbl3p/tun"
	"mpbl3p/udp"
	"mpbl3p/udp/congestion"
	"time"
)

func (c Configuration) Build(o *flags.Options) (*proxy.Proxy, error) {
	p := proxy.NewProxy(0)

	var g func() proxy.MacGenerator
	var v func() proxy.MacVerifier

	switch c.Host.Crypto {
	case "None":
		g = func() proxy.MacGenerator { return crypto.None{} }
		v = func() proxy.MacVerifier { return crypto.None{} }
	case "Blake2s":
		key, err := base64.StdEncoding.DecodeString(c.Host.SharedKey)
		if err != nil {
			return nil, err
		}
		if _, err := sharedkey.NewBlake2s(key); err != nil {
			return nil, err
		}
		g = func() proxy.MacGenerator {
			g, _ := sharedkey.NewBlake2s(key)
			return g
		}
		v = func() proxy.MacVerifier {
			v, _ := sharedkey.NewBlake2s(key)
			return v
		}
	}

	ifName := o.InterfaceName
	if ifName == "" {
		ifName = "nc%d"
	}

	ss, err := tun.NewTun(ifName, 1500)
	if err != nil {
		return nil, err
	}

	p.Source = ss
	p.Sink = ss

	for _, peer := range c.Peers {
		switch peer.Method {
		case "TCP":
			if err := buildTcp(p, peer, g, v); err != nil {
				return nil, err
			}
		case "UDP":
			if err := buildUdp(p, peer, g, v); err != nil {
				return nil, err
			}
		}
	}

	return p, nil
}

func buildTcp(p *proxy.Proxy, peer Peer, g func() proxy.MacGenerator, v func() proxy.MacVerifier) error {
	var laddr func() string
	if peer.LocalPort == 0 {
		laddr = func() string { return fmt.Sprintf("%s:", peer.GetLocalHost()) }
	} else {
		laddr = func() string { return fmt.Sprintf("%s:%d", peer.GetLocalHost(), peer.LocalPort) }
	}

	if peer.RemoteHost != "" {
		f, err := tcp.InitiateFlow(laddr, fmt.Sprintf("%s:%d", peer.RemoteHost, peer.RemotePort))

		if err != nil {
			return err
		}

		p.AddConsumer(f, g())
		p.AddProducer(f, v())

		return nil
	}

	err := tcp.NewListener(p, laddr(), v, g)
	if err != nil {
		return err
	}

	return nil
}

func buildUdp(p *proxy.Proxy, peer Peer, g func() proxy.MacGenerator, v func() proxy.MacVerifier) error {
	var laddr func() string
	if peer.LocalPort == 0 {
		laddr = func() string { return fmt.Sprintf("%s:", peer.GetLocalHost()) }
	} else {
		laddr = func() string { return fmt.Sprintf("%s:%d", peer.GetLocalHost(), peer.LocalPort) }
	}

	var c func() udp.Congestion
	switch peer.Congestion {
	case "None":
		c = func() udp.Congestion { return congestion.NewNone() }
	default:
		fallthrough
	case "NewReno":
		c = func() udp.Congestion { return congestion.NewNewReno() }
	}

	if peer.RemoteHost != "" {
		f, err := udp.InitiateFlow(
			laddr,
			fmt.Sprintf("%s:%d", peer.RemoteHost, peer.RemotePort),
			v(),
			g(),
			c(),
			time.Duration(peer.KeepAlive)*time.Second,
		)

		if err != nil {
			return err
		}

		p.AddConsumer(f, g())
		p.AddProducer(f, v())

		return nil
	}

	err := udp.NewListener(p, laddr(), v, g, c)
	if err != nil {
		return err
	}

	return nil
}