cmd/hello: make whois client work on macOS against GUI client

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/hello/hello.go

@@ -16,6 +16,8 @@ import (
 	"net"
 	"net/http"
 	"net/url"
+	"os"
+	"strconv"
 	"strings"
 
 	"tailscale.com/safesocket"
@@ -25,10 +27,21 @@ import (
 var (
 	httpAddr  = flag.String("http", ":80", "address to run an HTTP server on, or empty for none")
 	httpsAddr = flag.String("https", ":443", "address to run an HTTPS server on, or empty for none")
+	testIP    = flag.String("test-ip", "", "if non-empty, look up IP and exit before running a server")
 )
 
 func main() {
 	flag.Parse()
+	if *testIP != "" {
+		res, err := whoIs(*testIP)
+		if err != nil {
+			log.Fatal(err)
+		}
+		e := json.NewEncoder(os.Stdout)
+		e.SetIndent("", "\t")
+		e.Encode(res)
+		return
+	}
 	if !devMode() {
 		tmpl = template.Must(template.New("home").Parse(slurpHTML()))
 	}
@@ -113,6 +126,7 @@ func root(w http.ResponseWriter, r *http.Request) {
 	var data tmplData
 	if err != nil {
 		if devMode() {
+			log.Printf("warning: using fake data in dev mode due to whois lookup error: %v", err)
 			data = tmplData{
 				DisplayName:   "Taily Scalerson",
 				LoginName:     "taily@scaler.son",
@@ -153,13 +167,28 @@ func firstLabel(s string) string {
 var tsSockClient = &http.Client{
 	Transport: &http.Transport{
 		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
+			// On macOS, when dialing from non-sandboxed program to sandboxed GUI running
+			// a TCP server on a random port, find the random port. For HTTP connections,
+			// we don't send the token. It gets added in an HTTP Basic-Auth header.
+			if port, _, err := safesocket.LocalTCPPortAndToken(); err == nil {
+				var d net.Dialer
+				return d.DialContext(ctx, "tcp", "localhost:"+strconv.Itoa(port))
+			}
 			return safesocket.ConnectDefault()
 		},
 	},
 }
 
 func whoIs(ip string) (*tailcfg.WhoIsResponse, error) {
-	res, err := tsSockClient.Get("http://local-tailscaled.sock/localapi/v0/whois?ip=" + url.QueryEscape(ip))
+	ctx := context.Background()
+	req, err := http.NewRequestWithContext(ctx, "GET", "http://local-tailscaled.sock/localapi/v0/whois?ip="+url.QueryEscape(ip), nil)
+	if err != nil {
+		return nil, err
+	}
+	if _, token, err := safesocket.LocalTCPPortAndToken(); err == nil {
+		req.SetBasicAuth("", token)
+	}
+	res, err := tsSockClient.Do(req)
 	if err != nil {
 		return nil, err
 	}