syncthing/lib/relay/client/static.go

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// Copyright (C) 2015 Audrius Butkevicius and Contributors (see the CONTRIBUTORS file).
package client
import (
"context"
"crypto/tls"
"errors"
"fmt"
"net"
"net/url"
"time"
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"github.com/syncthing/syncthing/lib/dialer"
syncthingprotocol "github.com/syncthing/syncthing/lib/protocol"
"github.com/syncthing/syncthing/lib/relay/protocol"
)
type staticClient struct {
commonClient
uri *url.URL
config *tls.Config
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messageTimeout time.Duration
connectTimeout time.Duration
conn *tls.Conn
}
func newStaticClient(uri *url.URL, certs []tls.Certificate, invitations chan protocol.SessionInvitation, timeout time.Duration) *staticClient {
c := &staticClient{
uri: uri,
config: configForCerts(certs),
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messageTimeout: time.Minute * 2,
connectTimeout: timeout,
}
c.commonClient = newCommonClient(invitations, c.serve, c.String())
return c
}
func (c *staticClient) serve(ctx context.Context) error {
if err := c.connect(ctx); err != nil {
l.Debugf("Could not connect to relay %s: %s", c.uri, err)
return err
}
l.Debugln(c, "connected", c.conn.RemoteAddr())
defer c.disconnect()
if err := c.join(); err != nil {
l.Debugf("Could not join relay %s: %s", c.uri, err)
return err
}
if err := c.conn.SetDeadline(time.Time{}); err != nil {
l.Debugln("Relay set deadline:", err)
return err
}
l.Infof("Joined relay %s://%s", c.uri.Scheme, c.uri.Host)
messages := make(chan interface{})
errorsc := make(chan error, 1)
go messageReader(ctx, c.conn, messages, errorsc)
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timeout := time.NewTimer(c.messageTimeout)
for {
select {
case message := <-messages:
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timeout.Reset(c.messageTimeout)
l.Debugf("%s received message %T", c, message)
switch msg := message.(type) {
case protocol.Ping:
if err := protocol.WriteMessage(c.conn, protocol.Pong{}); err != nil {
l.Debugln("Relay write:", err)
return err
}
l.Debugln(c, "sent pong")
case protocol.SessionInvitation:
ip := net.IP(msg.Address)
if len(ip) == 0 || ip.IsUnspecified() {
msg.Address = remoteIPBytes(c.conn)
}
select {
case c.invitations <- msg:
case <-ctx.Done():
l.Debugln(c, "stopping")
return ctx.Err()
}
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case protocol.RelayFull:
l.Debugf("Disconnected from relay %s due to it becoming full.", c.uri)
return errors.New("relay full")
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default:
l.Debugln("Relay: protocol error: unexpected message %v", msg)
return fmt.Errorf("protocol error: unexpected message %v", msg)
}
case <-ctx.Done():
l.Debugln(c, "stopping")
return ctx.Err()
case err := <-errorsc:
l.Debugf("Disconnecting from relay %s due to error: %s", c.uri, err)
return err
case <-timeout.C:
l.Debugln(c, "timed out")
return errors.New("timed out")
}
}
}
func (c *staticClient) String() string {
return fmt.Sprintf("StaticClient:%p@%s", c, c.URI())
}
func (c *staticClient) URI() *url.URL {
return c.uri
}
func (c *staticClient) connect(ctx context.Context) error {
if c.uri.Scheme != "relay" {
return fmt.Errorf("unsupported relay scheme: %v", c.uri.Scheme)
}
timeoutCtx, cancel := context.WithTimeout(ctx, c.connectTimeout)
defer cancel()
tcpConn, err := dialer.DialContext(timeoutCtx, "tcp", c.uri.Host)
if err != nil {
return err
}
// Copy the TLS config and set the server name we're connecting to. In
// many cases this will be an IP address, in which case it's a no-op. In
// other cases it will be a hostname, which will cause the TLS stack to
// send SNI.
cfg := c.config
if host, _, err := net.SplitHostPort(c.uri.Host); err == nil {
cfg = cfg.Clone()
cfg.ServerName = host
}
conn := tls.Client(tcpConn, cfg)
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if err := conn.SetDeadline(time.Now().Add(c.connectTimeout)); err != nil {
conn.Close()
return err
}
if err := performHandshakeAndValidation(conn, c.uri); err != nil {
conn.Close()
return err
}
c.conn = conn
return nil
}
func (c *staticClient) disconnect() {
l.Debugln(c, "disconnecting")
c.conn.Close()
}
func (c *staticClient) join() error {
if err := protocol.WriteMessage(c.conn, protocol.JoinRelayRequest{}); err != nil {
return err
}
message, err := protocol.ReadMessage(c.conn)
if err != nil {
return err
}
switch msg := message.(type) {
case protocol.Response:
if msg.Code != 0 {
return &incorrectResponseCodeErr{msg.Code, msg.Message}
}
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case protocol.RelayFull:
return errors.New("relay full")
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default:
return fmt.Errorf("protocol error: expecting response got %v", msg)
}
return nil
}
func performHandshakeAndValidation(conn *tls.Conn, uri *url.URL) error {
if err := conn.Handshake(); err != nil {
return err
}
cs := conn.ConnectionState()
if cs.NegotiatedProtocol != protocol.ProtocolName {
return errors.New("protocol negotiation error")
}
q := uri.Query()
relayIDs := q.Get("id")
if relayIDs != "" {
relayID, err := syncthingprotocol.DeviceIDFromString(relayIDs)
if err != nil {
return fmt.Errorf("relay address contains invalid verification id: %w", err)
}
certs := cs.PeerCertificates
if cl := len(certs); cl != 1 {
return fmt.Errorf("unexpected certificate count: %d", cl)
}
remoteID := syncthingprotocol.NewDeviceID(certs[0].Raw)
if remoteID != relayID {
return fmt.Errorf("relay id does not match. Expected %v got %v", relayID, remoteID)
}
}
return nil
}
func messageReader(ctx context.Context, conn net.Conn, messages chan<- interface{}, errors chan<- error) {
for {
msg, err := protocol.ReadMessage(conn)
if err != nil {
errors <- err
return
}
select {
case messages <- msg:
case <-ctx.Done():
return
}
}
}