package dns import ( "bytes" "context" "fmt" "io" "net/http" "net/url" "sync" "sync/atomic" "time" "github.com/xtls/xray-core/common" "github.com/xtls/xray-core/common/errors" "github.com/xtls/xray-core/common/log" "github.com/xtls/xray-core/common/net" "github.com/xtls/xray-core/common/net/cnc" "github.com/xtls/xray-core/common/protocol/dns" "github.com/xtls/xray-core/common/session" "github.com/xtls/xray-core/common/signal/pubsub" "github.com/xtls/xray-core/common/task" dns_feature "github.com/xtls/xray-core/features/dns" "github.com/xtls/xray-core/features/routing" "github.com/xtls/xray-core/transport/internet" "golang.org/x/net/dns/dnsmessage" ) // DoHNameServer implemented DNS over HTTPS (RFC8484) Wire Format, // which is compatible with traditional dns over udp(RFC1035), // thus most of the DOH implementation is copied from udpns.go type DoHNameServer struct { dispatcher routing.Dispatcher sync.RWMutex ips map[string]*record pub *pubsub.Service cleanup *task.Periodic reqID uint32 httpClient *http.Client dohURL string name string queryStrategy QueryStrategy } // NewDoHNameServer creates DOH server object for remote resolving. func NewDoHNameServer(url *url.URL, dispatcher routing.Dispatcher, queryStrategy QueryStrategy) (*DoHNameServer, error) { errors.LogInfo(context.Background(), "DNS: created Remote DOH client for ", url.String()) s := baseDOHNameServer(url, "DOH", queryStrategy) s.dispatcher = dispatcher tr := &http.Transport{ MaxIdleConns: 30, IdleConnTimeout: 90 * time.Second, TLSHandshakeTimeout: 30 * time.Second, ForceAttemptHTTP2: true, DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) { dest, err := net.ParseDestination(network + ":" + addr) if err != nil { return nil, err } link, err := s.dispatcher.Dispatch(toDnsContext(ctx, s.dohURL), dest) select { case <-ctx.Done(): return nil, ctx.Err() default: } if err != nil { return nil, err } cc := common.ChainedClosable{} if cw, ok := link.Writer.(common.Closable); ok { cc = append(cc, cw) } if cr, ok := link.Reader.(common.Closable); ok { cc = append(cc, cr) } return cnc.NewConnection( cnc.ConnectionInputMulti(link.Writer), cnc.ConnectionOutputMulti(link.Reader), cnc.ConnectionOnClose(cc), ), nil }, } s.httpClient = &http.Client{ Timeout: time.Second * 180, Transport: tr, } return s, nil } // NewDoHLocalNameServer creates DOH client object for local resolving func NewDoHLocalNameServer(url *url.URL, queryStrategy QueryStrategy) *DoHNameServer { url.Scheme = "https" s := baseDOHNameServer(url, "DOHL", queryStrategy) tr := &http.Transport{ IdleConnTimeout: 90 * time.Second, ForceAttemptHTTP2: true, DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) { dest, err := net.ParseDestination(network + ":" + addr) if err != nil { return nil, err } conn, err := internet.DialSystem(ctx, dest, nil) log.Record(&log.AccessMessage{ From: "DNS", To: s.dohURL, Status: log.AccessAccepted, Detour: "local", }) if err != nil { return nil, err } return conn, nil }, } s.httpClient = &http.Client{ Timeout: time.Second * 180, Transport: tr, } errors.LogInfo(context.Background(), "DNS: created Local DOH client for ", url.String()) return s } func baseDOHNameServer(url *url.URL, prefix string, queryStrategy QueryStrategy) *DoHNameServer { s := &DoHNameServer{ ips: make(map[string]*record), pub: pubsub.NewService(), name: prefix + "//" + url.Host, dohURL: url.String(), queryStrategy: queryStrategy, } s.cleanup = &task.Periodic{ Interval: time.Minute, Execute: s.Cleanup, } return s } // Name implements Server. func (s *DoHNameServer) Name() string { return s.name } // Cleanup clears expired items from cache func (s *DoHNameServer) Cleanup() error { now := time.Now() s.Lock() defer s.Unlock() if len(s.ips) == 0 { return errors.New("nothing to do. stopping...") } for domain, record := range s.ips { if record.A != nil && record.A.Expire.Before(now) { record.A = nil } if record.AAAA != nil && record.AAAA.Expire.Before(now) { record.AAAA = nil } if record.A == nil && record.AAAA == nil { errors.LogDebug(context.Background(), s.name, " cleanup ", domain) delete(s.ips, domain) } else { s.ips[domain] = record } } if len(s.ips) == 0 { s.ips = make(map[string]*record) } return nil } func (s *DoHNameServer) updateIP(req *dnsRequest, ipRec *IPRecord) { elapsed := time.Since(req.start) s.Lock() rec, found := s.ips[req.domain] if !found { rec = &record{} } updated := false switch req.reqType { case dnsmessage.TypeA: if isNewer(rec.A, ipRec) { rec.A = ipRec updated = true } case dnsmessage.TypeAAAA: addr := make([]net.Address, 0, len(ipRec.IP)) for _, ip := range ipRec.IP { if len(ip.IP()) == net.IPv6len { addr = append(addr, ip) } } ipRec.IP = addr if isNewer(rec.AAAA, ipRec) { rec.AAAA = ipRec updated = true } } errors.LogInfo(context.Background(), s.name, " got answer: ", req.domain, " ", req.reqType, " -> ", ipRec.IP, " ", elapsed) if updated { s.ips[req.domain] = rec } switch req.reqType { case dnsmessage.TypeA: s.pub.Publish(req.domain+"4", nil) case dnsmessage.TypeAAAA: s.pub.Publish(req.domain+"6", nil) } s.Unlock() common.Must(s.cleanup.Start()) } func (s *DoHNameServer) newReqID() uint16 { return uint16(atomic.AddUint32(&s.reqID, 1)) } func (s *DoHNameServer) sendQuery(ctx context.Context, domain string, clientIP net.IP, option dns_feature.IPOption) { errors.LogInfo(ctx, s.name, " querying: ", domain) if s.name+"." == "DOH//"+domain { errors.LogError(ctx, s.name, " tries to resolve itself! Use IP or set \"hosts\" instead.") return } reqs := buildReqMsgs(domain, option, s.newReqID, genEDNS0Options(clientIP)) var deadline time.Time if d, ok := ctx.Deadline(); ok { deadline = d } else { deadline = time.Now().Add(time.Second * 5) } for _, req := range reqs { go func(r *dnsRequest) { // generate new context for each req, using same context // may cause reqs all aborted if any one encounter an error dnsCtx := ctx // reserve internal dns server requested Inbound if inbound := session.InboundFromContext(ctx); inbound != nil { dnsCtx = session.ContextWithInbound(dnsCtx, inbound) } dnsCtx = session.ContextWithContent(dnsCtx, &session.Content{ Protocol: "https", SkipDNSResolve: true, }) // forced to use mux for DOH // dnsCtx = session.ContextWithMuxPrefered(dnsCtx, true) var cancel context.CancelFunc dnsCtx, cancel = context.WithDeadline(dnsCtx, deadline) defer cancel() b, err := dns.PackMessage(r.msg) if err != nil { errors.LogErrorInner(ctx, err, "failed to pack dns query for ", domain) return } resp, err := s.dohHTTPSContext(dnsCtx, b.Bytes()) if err != nil { errors.LogErrorInner(ctx, err, "failed to retrieve response for ", domain) return } rec, err := parseResponse(resp) if err != nil { errors.LogErrorInner(ctx, err, "failed to handle DOH response for ", domain) return } s.updateIP(r, rec) }(req) } } func (s *DoHNameServer) dohHTTPSContext(ctx context.Context, b []byte) ([]byte, error) { body := bytes.NewBuffer(b) req, err := http.NewRequest("POST", s.dohURL, body) if err != nil { return nil, err } req.Header.Add("Accept", "application/dns-message") req.Header.Add("Content-Type", "application/dns-message") hc := s.httpClient resp, err := hc.Do(req.WithContext(ctx)) if err != nil { return nil, err } defer resp.Body.Close() if resp.StatusCode != http.StatusOK { io.Copy(io.Discard, resp.Body) // flush resp.Body so that the conn is reusable return nil, fmt.Errorf("DOH server returned code %d", resp.StatusCode) } return io.ReadAll(resp.Body) } func (s *DoHNameServer) findIPsForDomain(domain string, option dns_feature.IPOption) ([]net.IP, error) { s.RLock() record, found := s.ips[domain] s.RUnlock() if !found { return nil, errRecordNotFound } var err4 error var err6 error var ips []net.Address var ip6 []net.Address if option.IPv4Enable { ips, err4 = record.A.getIPs() } if option.IPv6Enable { ip6, err6 = record.AAAA.getIPs() ips = append(ips, ip6...) } if len(ips) > 0 { return toNetIP(ips) } if err4 != nil { return nil, err4 } if err6 != nil { return nil, err6 } if (option.IPv4Enable && record.A != nil) || (option.IPv6Enable && record.AAAA != nil) { return nil, dns_feature.ErrEmptyResponse } return nil, errRecordNotFound } // QueryIP implements Server. func (s *DoHNameServer) QueryIP(ctx context.Context, domain string, clientIP net.IP, option dns_feature.IPOption, disableCache bool) ([]net.IP, error) { // nolint: dupl fqdn := Fqdn(domain) option = ResolveIpOptionOverride(s.queryStrategy, option) if !option.IPv4Enable && !option.IPv6Enable { return nil, dns_feature.ErrEmptyResponse } if disableCache { errors.LogDebug(ctx, "DNS cache is disabled. Querying IP for ", domain, " at ", s.name) } else { ips, err := s.findIPsForDomain(fqdn, option) if err != errRecordNotFound { errors.LogDebugInner(ctx, err, s.name, " cache HIT ", domain, " -> ", ips) log.Record(&log.DNSLog{Server: s.name, Domain: domain, Result: ips, Status: log.DNSCacheHit, Elapsed: 0, Error: err}) return ips, err } } // ipv4 and ipv6 belong to different subscription groups var sub4, sub6 *pubsub.Subscriber if option.IPv4Enable { sub4 = s.pub.Subscribe(fqdn + "4") defer sub4.Close() } if option.IPv6Enable { sub6 = s.pub.Subscribe(fqdn + "6") defer sub6.Close() } done := make(chan interface{}) go func() { if sub4 != nil { select { case <-sub4.Wait(): case <-ctx.Done(): } } if sub6 != nil { select { case <-sub6.Wait(): case <-ctx.Done(): } } close(done) }() s.sendQuery(ctx, fqdn, clientIP, option) start := time.Now() for { ips, err := s.findIPsForDomain(fqdn, option) if err != errRecordNotFound { log.Record(&log.DNSLog{Server: s.name, Domain: domain, Result: ips, Status: log.DNSQueried, Elapsed: time.Since(start), Error: err}) return ips, err } select { case <-ctx.Done(): return nil, ctx.Err() case <-done: } } }