cmd/derper: show more information on home page

- Basic description of DERP If configured to do so, also show - Mailto link to security@tailscale.com - Link to Tailscale Security Policies - Link to Tailscale Acceptable Use Policy Updates tailscale/corp#24092 Signed-off-by: Percy Wegmann <percy@tailscale.com>
1 month ago · 8dcbd988f7
parent 065825e94c
commit 8dcbd988f7
3 changed files with 92 additions and 19 deletions
--- a/cmd/derper/depaware.txt
+++ b/cmd/derper/depaware.txt
@ -264,6 +264,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
        hash/fnv                                                     from google.golang.org/protobuf/internal/detrand
        hash/maphash                                                 from go4.org/mem
        html                                                         from net/http/pprof+
+        html/template                                                from tailscale.com/cmd/derper
        io                                                           from bufio+
        io/fs                                                        from crypto/x509+
        io/ioutil                                                    from github.com/mitchellh/go-ps+
@ -308,6 +309,8 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
        sync/atomic                                                  from context+
        syscall                                                      from crypto/rand+
        text/tabwriter                                               from runtime/pprof
+        text/template                                                from html/template
+        text/template/parse                                          from html/template+
        time                                                         from compress/gzip+
        unicode                                                      from bytes+
        unicode/utf16                                                from crypto/x509+
--- a/cmd/derper/derper.go
+++ b/cmd/derper/derper.go
@ -19,6 +19,7 @@ import (
 	"expvar"
 	"flag"
 	"fmt"
+	"html/template"
 	"io"
 	"log"
 	"math"
@ -212,25 +213,16 @@ func main() {
 		tsweb.AddBrowserHeaders(w)
 		w.Header().Set("Content-Type", "text/html; charset=utf-8")
 		w.WriteHeader(200)
-		io.WriteString(w, `<html><body>
-<h1>DERP</h1>
-<p>
-  This is a <a href="https://tailscale.com/">Tailscale</a> DERP server.
-</p>
-<p>
-  Documentation:
-</p>
-<ul>
-  <li><a href="https://tailscale.com/kb/1232/derp-servers">About DERP</a></li>
-  <li><a href="https://pkg.go.dev/tailscale.com/derp">Protocol & Go docs</a></li>
-  <li><a href="https://github.com/tailscale/tailscale/tree/main/cmd/derper#derp">How to run a DERP server</a></li>
-</ul>
-`)
-		if !*runDERP {
-			io.WriteString(w, `<p>Status: <b>disabled</b></p>`)
-		}
-		if tsweb.AllowDebugAccess(r) {
-			io.WriteString(w, "<p>Debug info at <a href='/debug/'>/debug/</a>.</p>\n")
+		err := homePageTemplate.Execute(w, templateData{
+			ShowAbuseInfo: validProdHostname.MatchString(*hostname),
+			Disabled:      !*runDERP,
+			AllowDebug:    tsweb.AllowDebugAccess(r),
+		})
+		if err != nil {
+			if r.Context().Err() == nil {
+				log.Printf("homePageTemplate.Execute: %v", err)
+			}
+			return
 		}
 	}))
 	mux.Handle("/robots.txt", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@ -468,3 +460,52 @@ func init() {
 		return 0
 	}))
 }
+
+type templateData struct {
+	ShowAbuseInfo bool
+	Disabled      bool
+	AllowDebug    bool
+}
+
+// homePageTemplate renders the home page using [templateData].
+var homePageTemplate = template.Must(template.New("home").Parse(`<html><body>
+<h1>DERP</h1>
+<p>
+  This is a <a href="https://tailscale.com/">Tailscale</a> DERP server.
+</p>
+
+<p>
+  It provides STUN, interactive connectivity establishment, and relaying of end-to-end encrypted traffic
+  for Tailscale clients.
+</p>
+
+{{if .ShowAbuseInfo }}
+<p>
+  If you suspect abuse, please contact <a href="mailto:security@tailscale.com">security@tailscale.com</a>.
+</p>
+{{end}}
+
+<p>
+  Documentation:
+</p>
+
+<ul>
+{{if .ShowAbuseInfo }}
+  <li><a href="https://tailscale.com/security-policies">Tailscale Security Policies</a></li>
+  <li><a href="https://tailscale.com/tailscale-aup">Tailscale Acceptable Use Policies</a></li>
+{{end}}
+  <li><a href="https://tailscale.com/kb/1232/derp-servers">About DERP</a></li>
+  <li><a href="https://pkg.go.dev/tailscale.com/derp">Protocol & Go docs</a></li>
+  <li><a href="https://github.com/tailscale/tailscale/tree/main/cmd/derper#derp">How to run a DERP server</a></li>
+</ul>
+
+{{if .Disabled}}
+<p>Status: <b>disabled</b></p>
+{{end}}
+
+{{if .AllowDebug}}
+<p>Debug info at <a href='/debug/'>/debug/</a>.</p>
+{{end}}
+</body>
+</html>
+`))
--- a/cmd/derper/derper_test.go
+++ b/cmd/derper/derper_test.go
@ -4,7 +4,9 @@
 package main

 import (
+	"bytes"
 	"context"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@ -110,3 +112,30 @@ func TestDeps(t *testing.T) {
 		},
 	}.Check(t)
 }
+
+func TestTemplate(t *testing.T) {
+	buf := &bytes.Buffer{}
+	err := homePageTemplate.Execute(buf, templateData{
+		ShowAbuseInfo: true,
+		Disabled:      true,
+		AllowDebug:    true,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	str := buf.String()
+	if !strings.Contains(str, "If you suspect abuse") {
+		t.Error("Output is missing abuse mailto")
+	}
+	if !strings.Contains(str, "Tailscale Security Policies") {
+		t.Error("Output is missing Tailscale Security Policies link")
+	}
+	if !strings.Contains(str, "Status:") {
+		t.Error("Output is missing disabled status")
+	}
+	if !strings.Contains(str, "Debug info") {
+		t.Error("Output is missing debug info")
+	}
+	fmt.Println(buf.String())
+}