golink: listen on HTTPS and redirect HTTP traffic

Updates #9

On tailnets with TLS enabled serve HTTP traffic with a separate
redirectHandler which sends requests to our HTTPS listener destination.

Add `-L` to documented examples of using `curl` to follow these
redirects if present.

Signed-off-by: Patrick O'Doherty <[email protected]>

golink.go

@@ -9,6 +9,7 @@ import (
 	"bytes"
 	"context"
 	"crypto/rand"
+	"crypto/tls"
 	"embed"
 	"encoding/base64"
 	"encoding/json"
@@ -169,18 +170,78 @@ func Run() error {
 	if err := srv.Start(); err != nil {
 		return err
 	}
-	localClient, _ = srv.LocalClient()
 
-	l80, err := srv.Listen("tcp", ":80")
+	// create tsNet server and wait for it to be ready & connected.
+	localClient, _ = srv.LocalClient()
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	_, err = srv.Up(ctx)
 	if err != nil {
 		return err
 	}
 
-	log.Printf("Serving http://%s/ ...", *hostname)
-	if err := http.Serve(l80, serveHandler()); err != nil {
-		return err
+	enableTLS := len(srv.CertDomains()) > 0
+	if enableTLS {
+		// warm the certificate cache for all cert domains to prevent users waiting
+		// on ACME challenges in-line on their first request.
+		for _, d := range srv.CertDomains() {
+			log.Printf("Provisioning TLS certificate for %s ...", d)
+			ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+			defer cancel()
+
+			_, _, err := localClient.CertPair(ctx, d)
+			if err != nil {
+				return err
+			}
+		}
+
+		redirectFqdn := srv.CertDomains()[0]
+		// HTTP listener that redirects to our HTTPS listener.
+		log.Println("Listening on :80")
+		httpListener, err := srv.Listen("tcp", ":80")
+		if err != nil {
+			return err
+		}
+		go func() error {
+			log.Printf("Serving http://%s/ ...", *hostname)
+			if err := http.Serve(httpListener, redirectHandler(redirectFqdn)); err != nil {
+				return err
+			}
+			return nil
+		}()
+
+		log.Println("Listening on :443")
+		httpsListener, err := srv.Listen("tcp", ":443")
+		if err != nil {
+			return err
+		}
+		s := http.Server{
+			Addr:    ":443",
+			Handler: serveHandler(),
+			TLSConfig: &tls.Config{
+				GetCertificate: localClient.GetCertificate,
+			},
+		}
+
+		log.Printf("Serving https://%s/\n", redirectFqdn)
+		if err := s.ServeTLS(httpsListener, "", ""); err != nil {
+			return err
+		}
+		return nil
+	} else {
+		// no TLS, just serve on :80
+		log.Println("Listening on :80")
+		httpListener, err := srv.Listen("tcp", ":80")
+		if err != nil {
+			return err
+		}
+		log.Printf("Serving http://%s/ ...", *hostname)
+		if err := http.Serve(httpListener, serveHandler()); err != nil {
+			return err
+		}
+		return nil
 	}
-	return nil
+
 }
 
 var (
@@ -286,6 +347,16 @@ func deleteLinkStats(link *Link) {
 	db.DeleteStats(link.Short)
 }
 
+// redirectHandler returns the http.Handler for serving all plaintext HTTP
+// requests. It redirects all requests to the HTTPs version of the same URL.
+func redirectHandler(hostname string) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		path := r.URL.Path
+		newUrl := fmt.Sprintf("https://%s%s", hostname, path)
+		http.Redirect(w, r, newUrl, http.StatusMovedPermanently)
+	})
+}
+
 // serverHandler returns the main http.Handler for serving all requests.
 func serveHandler() http.Handler {
 	mux := http.NewServeMux()

tmpl/help.html

@@ -114,15 +114,15 @@ <h2 id="api">Application Programming Interface (API)</h2>
 Visit <a href="/.export">go/.export</a> to export all saved links and their metadata in <a href="https://jsonlines.org/">JSON Lines format</a>.
 This is useful to create data snapshots that can be restored later.
 
-<pre>{{`$ curl go/.export
+<pre>{{`$ curl -L go/.export
 {"Short":"go","Long":"http://go","Created":"2022-05-31T13:04:44.741457796-07:00","LastEdit":"2022-05-31T13:04:44.741457796-07:00","Owner":"[email protected]","Clicks":1}
 {"Short":"slack","Long":"https://company.slack.com/{{if .Path}}channels/{{PathEscape .Path}}{{end}}","Created":"2022-06-17T18:05:43.562948451Z","LastEdit":"2022-06-17T18:06:35.811398Z","Owner":"[email protected]","Clicks":4}`}}
 </pre>
 
 <p>
 Create a new link by sending a POST request with a <code>short</code> and <code>long</code> value:
 
-<pre>{{`$ curl -d short=cs -d long=https://cs.github.com/ go
+<pre>{{`$ curl -L -d short=cs -d long=https://cs.github.com/ go
 {"Short":"cs","Long":"https://cs.github.com/","Created":"2022-06-03T22:15:29.993978392Z","LastEdit":"2022-06-03T22:15:29.993978392Z","Owner":"[email protected]"}`}}
 </pre>