net.go

package tor

import (
	"errors"
	"net"
)

// TODO: this interface and its implementations should ideally be moved
// elsewhere as they are not Tor-specific.

// Net is an interface housing a Dial function and several DNS functions that
// allows us to abstract the implementations of these functions over different
// networks, e.g. clearnet, Tor net, etc.
type Net interface {
	// Dial connects to the address on the named network.
	Dial(network, address string) (net.Conn, error)

	// LookupHost performs DNS resolution on a given host and returns its
	// addresses.
	LookupHost(host string) ([]string, error)

	// LookupSRV tries to resolve an SRV query of the given service,
	// protocol, and domain name.
	LookupSRV(service, proto, name string) (string, []*net.SRV, error)

	// ResolveTCPAddr resolves TCP addresses.
	ResolveTCPAddr(network, address string) (*net.TCPAddr, error)
}

// ClearNet is an implementation of the Net interface that defines behaviour
// for regular network connections.
type ClearNet struct{}

// Dial on the regular network uses net.Dial
func (r *ClearNet) Dial(network, address string) (net.Conn, error) {
	return net.Dial(network, address)
}

// LookupHost for regular network uses the net.LookupHost function
func (r *ClearNet) LookupHost(host string) ([]string, error) {
	return net.LookupHost(host)
}

// LookupSRV for regular network uses net.LookupSRV function
func (r *ClearNet) LookupSRV(service, proto, name string) (string, []*net.SRV, error) {
	return net.LookupSRV(service, proto, name)
}

// ResolveTCPAddr for regular network uses net.ResolveTCPAddr function
func (r *ClearNet) ResolveTCPAddr(network, address string) (*net.TCPAddr, error) {
	return net.ResolveTCPAddr(network, address)
}

// ProxyNet is an implementation of the Net interface that defines behaviour
// for Tor network connections.
type ProxyNet struct {
	// SOCKS is the host:port which Tor's exposed SOCKS5 proxy is listening
	// on.
	SOCKS string

	// DNS is the host:port of the DNS server for Tor to use for SRV
	// queries.
	DNS string

	// StreamIsolation is a bool that determines if we should force the
	// creation of a new circuit for this connection. If true, then this
	// means that our traffic may be harder to correlate as each connection
	// will now use a distinct circuit.
	StreamIsolation bool
}

// Dial uses the Tor Dial function in order to establish connections through
// Tor. Since Tor only supports TCP connections, only TCP networks are allowed.
func (p *ProxyNet) Dial(network, address string) (net.Conn, error) {
	switch network {
	case "tcp", "tcp4", "tcp6":
	default:
		return nil, errors.New("cannot dial non-tcp network via Tor")
	}
	return Dial(address, p.SOCKS, p.StreamIsolation)
}

// LookupHost uses the Tor LookupHost function in order to resolve hosts over
// Tor.
func (p *ProxyNet) LookupHost(host string) ([]string, error) {
	return LookupHost(host, p.SOCKS)
}

// LookupSRV uses the Tor LookupSRV function in order to resolve SRV DNS queries
// over Tor.
func (p *ProxyNet) LookupSRV(service, proto, name string) (string, []*net.SRV, error) {
	return LookupSRV(service, proto, name, p.SOCKS, p.DNS, p.StreamIsolation)
}

// ResolveTCPAddr uses the Tor ResolveTCPAddr function in order to resolve TCP
// addresses over Tor.
func (p *ProxyNet) ResolveTCPAddr(network, address string) (*net.TCPAddr, error) {
	switch network {
	case "tcp", "tcp4", "tcp6":
	default:
		return nil, errors.New("cannot dial non-tcp network via Tor")
	}
	return ResolveTCPAddr(address, p.SOCKS)
}