Add support for specifying a specific HTTP Host: header on the origin.

cmd/cloudflared/tunnel/cmd.go

@@ -488,6 +488,12 @@ func tunnelFlags(shouldHide bool) []cli.Flag {
 			EnvVars: []string{"TUNNEL_HOSTNAME"},
 			Hidden:  shouldHide,
 		}),
+		altsrc.NewStringFlag(&cli.StringFlag{
+			Name:    "httphost",
+			Usage:   "Sets the HTTP Host header for the local webserver.",
+			EnvVars: []string{"TUNNEL_HTTPHOST"},
+			Hidden:  shouldHide,
+		}),
 		altsrc.NewStringFlag(&cli.StringFlag{
 			Name:    "origin-server-name",
 			Usage:   "Hostname on the origin server certificate.",

cmd/cloudflared/tunnel/configuration.go

@@ -251,6 +251,7 @@ func prepareTunnelConfig(
 		HTTPTransport:        httpTransport,
 		HeartbeatInterval:    c.Duration("heartbeat-interval"),
 		Hostname:             hostname,
+		HTTPHost:             c.String("httphost"),
 		IncidentLookup:       origin.NewIncidentLookup(),
 		IsAutoupdated:        c.Bool("is-autoupdated"),
 		IsFreeTunnel:         isFreeTunnel,

origin/tunnel.go

@@ -52,6 +52,7 @@ type TunnelConfig struct {
 	HTTPTransport        http.RoundTripper
 	HeartbeatInterval    time.Duration
 	Hostname             string
+	HTTPHost             string
 	IncidentLookup       IncidentLookup
 	IsAutoupdated        bool
 	IsFreeTunnel         bool
@@ -520,6 +521,7 @@ func FindCfRayHeader(h1 *http.Request) string {
 
 type TunnelHandler struct {
 	originUrl  string
+	httpHost   string
 	muxer      *h2mux.Muxer
 	httpClient http.RoundTripper
 	tlsConfig  *tls.Config
@@ -545,6 +547,7 @@ func NewTunnelHandler(ctx context.Context,
 	}
 	h := &TunnelHandler{
 		originUrl:         originURL,
+		httpHost:          config.HTTPHost,
 		httpClient:        config.HTTPTransport,
 		tlsConfig:         config.ClientTlsConfig,
 		tags:              config.Tags,
@@ -629,6 +632,7 @@ func (h *TunnelHandler) createRequest(stream *h2mux.MuxedStream) (*http.Request,
 	if err != nil {
 		return nil, errors.Wrap(err, "Unexpected error from http.NewRequest")
 	}
+
 	err = H2RequestHeadersToH1Request(stream.Headers, req)
 	if err != nil {
 		return nil, errors.Wrap(err, "invalid request received")
@@ -666,6 +670,11 @@ func (h *TunnelHandler) serveHTTP(stream *h2mux.MuxedStream, req *http.Request)
 	// Request origin to keep connection alive to improve performance
 	req.Header.Set("Connection", "keep-alive")
 
+	if h.httpHost != "" {
+		req.Header.Set("Host", h.httpHost)
+		req.Host = h.httpHost
+	}
+
 	response, err := h.httpClient.RoundTrip(req)
 	if err != nil {
 		return nil, errors.Wrap(err, "Error proxying request to origin")