tapir/networks/tor/BaseOnionService.go

package tor

import (
	"crypto/rand"
	"cwtch.im/tapir"
	"cwtch.im/tapir/primitives"
	"encoding/base64"
	"errors"
	"git.openprivacy.ca/openprivacy/connectivity"
	"git.openprivacy.ca/openprivacy/log"
	"golang.org/x/crypto/ed25519"
	"sync"
	"time"
)

// BaseOnionService is a concrete implementation of the service interface over Tor onion services.
type BaseOnionService struct {
	connections sync.Map
	acn         connectivity.ACN
	id          *primitives.Identity
	privateKey  ed25519.PrivateKey
	ls          connectivity.ListenService
	lock        sync.Mutex
}

// Metrics provides a report of useful information about the status of the service e.g. the number of active
// connections
func (s *BaseOnionService) Metrics() tapir.ServiceMetrics {
	s.lock.Lock()
	defer s.lock.Unlock()

	count := 0
	s.connections.Range(func(key, value interface{}) bool {
		connection := value.(tapir.Connection)
		if !connection.IsClosed() {
			count++
		}
		return true
	})

	return tapir.ServiceMetrics{
		ConnectionCount: count,
	}
}

// Init initializes a BaseOnionService with a given private key and identity
// The private key is needed to initialize the Onion listen socket, ideally we could just pass an Identity in here.
func (s *BaseOnionService) Init(acn connectivity.ACN, sk ed25519.PrivateKey, id *primitives.Identity) {
	// run add onion
	// get listen context
	s.acn = acn
	s.id = id
	s.privateKey = sk
}

// WaitForCapabilityOrClose blocks until the connection has the given capability or the underlying connection is closed
// (through error or user action)
func (s *BaseOnionService) WaitForCapabilityOrClose(cid string, name tapir.Capability) (tapir.Connection, error) {
	conn, err := s.GetConnection(cid)
	// If there is at least one active connection, then check the one that is returned and use it
	for conn != nil {
		if conn.HasCapability(name) {
			return conn, nil
		}
		time.Sleep(time.Millisecond * 200)
		// If we received both a Connection and an Error from GetConnection that means we have multiple connections
		// If that was the case we refresh from the connection store as the likely case is one of them has been
		// closed and the other one has the capabilities we need.
		if err != nil {
			conn, err = s.GetConnection(cid)
		}
	}
	// There are no active connections with that hostname
	return nil, err
}

// GetConnection returns a connection for a given hostname.
func (s *BaseOnionService) GetConnection(hostname string) (tapir.Connection, error) {
	conn := make([]tapir.Connection, 0)
	s.connections.Range(func(key, value interface{}) bool {
		connection := value.(tapir.Connection)
		if connection.Hostname() == hostname {
			if !connection.IsClosed() {
				conn = append(conn, connection)
				return true
			}
		}
		return true
	})
	if len(conn) == 0 {
		return nil, errors.New("no connection found")
	}
	if len(conn) > 1 {
		// If there are multiple connections we return the first one but also notify the user (this should be a
		// temporary edgecase (see Connect))
		return conn[0], errors.New("multiple connections found")
	}
	return conn[0], nil
}

// Connect initializes a new outbound connection to the given peer, using the defined Application
func (s *BaseOnionService) Connect(hostname string, app tapir.Application) (bool, error) {
	_, err := s.GetConnection(hostname)
	if err == nil {
		// Note: This check is not 100% reliable. And we may end up with two connections between peers
		// This can happen when a client connects to a server as the server is connecting to the client
		// Because at the start of the connection the server cannot derive the true hostname of the client until it
		// has auth'd
		// We mitigate this by performing multiple checks when Connect'ing
		return true, errors.New("already connected to " + hostname)
	}
	// connects to a remote server
	// spins off to a connection struct
	log.Debugf("Connecting to %v", hostname)
	conn, _, err := s.acn.Open(hostname)
	if err == nil {
		connectionID := s.getNewConnectionID()

		// Second check. If we didn't catch a double connection attempt before the Open we *should* catch it now because
		// the auth protocol is quick and Open over onion connections can take some time.
		// Again this isn't 100% reliable.
		_, err := s.GetConnection(hostname)
		if err == nil {
			conn.Close()
			return true, errors.New("already connected to " + hostname)
		}

		log.Debugf("Connected to %v [%v]", hostname, connectionID)
		s.connections.Store(connectionID, tapir.NewConnection(s, s.id, hostname, true, conn, app.NewInstance()))
		return true, nil
	}
	log.Debugf("Error connecting to %v %v", hostname, err)
	return false, err
}

func (s *BaseOnionService) getNewConnectionID() string {
	id := make([]byte, 10)
	rand.Read(id)
	connectionID := "connection-" + base64.StdEncoding.EncodeToString(id)
	return connectionID
}

// Listen starts a blocking routine that waits for incoming connections and initializes connections with them based
// on the given Application.
func (s *BaseOnionService) Listen(app tapir.Application) error {
	// accepts a new connection
	// spins off to a connection struct
	s.lock.Lock()
	ls, err := s.acn.Listen(s.privateKey, 9878)
	s.ls = ls
	log.Debugf("Starting a service on %v ", ls.AddressFull())
	s.lock.Unlock()

	if err == nil {
		for {
			conn, err := s.ls.Accept()
			if err == nil {
				tempHostname := s.getNewConnectionID()
				log.Debugf("Accepted connection from %v", tempHostname)
				s.connections.Store(tempHostname, tapir.NewConnection(s, s.id, tempHostname, false, conn, app.NewInstance()))
			} else {
				log.Debugf("Error accepting connection %v", err)
				return err
			}
		}
	}
	log.Debugf("Error listening to connection %v", err)
	return err
}

// Shutdown closes the service and ensures that any connections are closed.
func (s *BaseOnionService) Shutdown() {
	s.lock.Lock()
	defer s.lock.Unlock()
	if s.ls != nil {
		s.ls.Close()
	}
	s.connections.Range(func(key, value interface{}) bool {
		connection := value.(tapir.Connection)
		connection.Close()
		return true
	})
}

// Broadcast sends a message to all connections who possess the given capability
func (s *BaseOnionService) Broadcast(message []byte, capability tapir.Capability) error {
	s.lock.Lock()
	defer s.lock.Unlock()
	s.connections.Range(func(key, value interface{}) bool {
		connection := value.(tapir.Connection)
		if connection.HasCapability(capability) {
			connection.Send(message)
		}
		return true
	})
	return nil
}