Server 2.6.1: code field upper-cases and inserts the dash

The phone pages' code field gets one inline script, allowed by its
SHA-256 hash in the CSP; a test checks the served script against the
header. Image pinned by digest in k8s/server.yaml (not applied).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QLJfZQZeAKAwSqViTmLzki

server/handoff_http.go

@@ -111,7 +111,7 @@ var settingsTemplate = template.Must(template.New("settings").Parse(`<!doctype h
 <form method="post" action="/settings" autocomplete="off">
 {{if .Code}}<div class="code">{{.Code}}</div><input type="hidden" name="code" value="{{.Code}}">
 {{else}}<label for="code">Code shown on the car</label>
-<input id="code" name="code" autocapitalize="characters" placeholder="XXX-XXX" required>{{end}}
+` + codeInput + `{{end}}
 <label for="abrpApiKey">ABRP API key</label>
 <input id="abrpApiKey" name="abrpApiKey" type="password" autocomplete="off" spellcheck="false">
 <label for="abrpToken">ABRP user token</label>
@@ -133,7 +133,7 @@ var settingsTemplate = template.Must(template.New("settings").Parse(`<!doctype h
 func renderSettingsPage(w http.ResponseWriter, status int, data settingsPageData) {
 	h := w.Header()
 	h.Set("Content-Type", "text/html; charset=utf-8")
-	h.Set("Content-Security-Policy", "default-src 'none'; style-src 'unsafe-inline'; form-action 'self'; frame-ancestors 'none'; base-uri 'none'")
+	h.Set("Content-Security-Policy", pageCSP)
 	h.Set("X-Content-Type-Options", "nosniff")
 	h.Set("Referrer-Policy", "no-referrer")
 	h.Set("Cache-Control", "no-store")

server/pairing_http.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"crypto/sha256"
+	"encoding/base64"
 	"errors"
 	"html/template"
 	"io"
@@ -147,7 +149,7 @@ type pageData struct {
 	Done    bool
 }
 
-// pageStyle is shared by the phone pages (pairing, settings): dark, MG red, no scripts.
+// pageStyle is shared by the phone pages (pairing, settings): dark, MG red.
 const pageStyle = `
 :root{color-scheme:dark}
 body{margin:0;min-height:100vh;display:flex;align-items:center;justify-content:center;background:#000;color:#F4F3EF;font:16px/1.5 system-ui,sans-serif}
@@ -160,8 +162,29 @@ input{box-sizing:border-box;width:100%;padding:14px;border-radius:10px;border:1p
 button{flex:1;padding:14px;border-radius:10px;border:0;font-size:17px;font-weight:600;cursor:pointer}
 .approve{background:#E0424C;color:#1A0B0C}.deny{background:#2A1416;color:#FF9A9E;border:1px solid #3A1215}
 .error{color:#FFB4AB}.ok{color:#A4DCC1}
+#code{text-transform:uppercase;letter-spacing:2px;font-family:ui-monospace,monospace}
 `
 
+// codeInput is the typed-code field of both phone pages. Its script upper-cases what is typed and
+// puts the dash in after the third character; without the script the server still accepts the
+// code in any case, with or without the dash (normalizeUserCode).
+const codeInput = `<input id="code" name="code" autocapitalize="characters" autocomplete="off" autocorrect="off" spellcheck="false" maxlength="7" placeholder="XXX-XXX" required>
+<script>` + codeScript + `</script>`
+
+const codeScript = `document.getElementById('code').addEventListener('input',function(e){` +
+	`var v=this.value.toUpperCase().replace(/[^A-Z0-9]/g,'').slice(0,6);` +
+	`var del=e.inputType&&e.inputType.indexOf('delete')===0;` +
+	`this.value=v.length>3||(v.length===3&&!del)?v.slice(0,3)+'-'+v.slice(3):v;});`
+
+// pageCSP allows no script but codeScript, pinned by its hash, and forms only back to this server.
+var pageCSP = "default-src 'none'; script-src 'sha256-" + scriptHash(codeScript) +
+	"'; style-src 'unsafe-inline'; form-action 'self'; frame-ancestors 'none'; base-uri 'none'"
+
+func scriptHash(script string) string {
+	sum := sha256.Sum256([]byte(script))
+	return base64.StdEncoding.EncodeToString(sum[:])
+}
+
 var pairTemplate = template.Must(template.New("pair").Parse(`<!doctype html>
 <html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1">
 <title>Pair a car — Nils' MG4</title>
@@ -174,7 +197,7 @@ var pairTemplate = template.Must(template.New("pair").Parse(`<!doctype html>
 <form method="post" action="/pair" autocomplete="on">
 {{if .Code}}<div class="code">{{.Code}}</div><input type="hidden" name="code" value="{{.Code}}">
 {{else}}<label for="code">Code shown on the car</label>
-<input id="code" name="code" autocapitalize="characters" autocomplete="off" placeholder="XXX-XXX" required>{{end}}
+` + codeInput + `{{end}}
 <input type="text" name="username" value="mg4-approval" autocomplete="username" hidden readonly>
 <label for="password">Approval password</label>
 <input id="password" name="password" type="password" autocomplete="current-password" required {{if .Code}}autofocus{{end}}>
@@ -188,8 +211,7 @@ var pairTemplate = template.Must(template.New("pair").Parse(`<!doctype html>
 func renderPage(w http.ResponseWriter, status int, data pageData) {
 	h := w.Header()
 	h.Set("Content-Type", "text/html; charset=utf-8")
-	// No scripts at all, no framing, forms only back to this page.
-	h.Set("Content-Security-Policy", "default-src 'none'; style-src 'unsafe-inline'; form-action 'self'; frame-ancestors 'none'; base-uri 'none'")
+	h.Set("Content-Security-Policy", pageCSP)
 	h.Set("X-Content-Type-Options", "nosniff")
 	h.Set("Referrer-Policy", "no-referrer")
 	h.Set("Cache-Control", "no-store")

server/pairing_test.go

@@ -329,3 +329,30 @@ func TestClientAddressTakesTheProxysEntry(t *testing.T) {
 		t.Fatalf("without a proxy: %q", got)
 	}
 }
+
+// The typed-code field's script is the only one the pages may run: the CSP pins it by hash, so
+// the script served must hash to exactly what the header allows.
+func TestCodeScriptMatchesTheCSP(t *testing.T) {
+	api, _ := newTestAPI()
+	h := api.Routes()
+	script := regexp.MustCompile(`(?s)<script>(.*?)</script>`)
+	for _, path := range []string{"/pair", "/settings"} {
+		page := do(t, h, "GET", path, "", "")
+		if page.Code != 200 {
+			t.Fatalf("%s: %d", path, page.Code)
+		}
+		m := script.FindAllStringSubmatch(page.Body.String(), -1)
+		if len(m) != 1 || m[0][1] != codeScript {
+			t.Fatalf("%s: scripts %q", path, m)
+		}
+		csp := page.Header().Get("Content-Security-Policy")
+		if !strings.Contains(csp, "script-src 'sha256-"+scriptHash(m[0][1])+"'") || !strings.Contains(csp, "default-src 'none'") {
+			t.Fatalf("%s: CSP %q", path, csp)
+		}
+	}
+	// With the code in the link there is nothing to type, and no script.
+	_, userCode, _ := startPairing(t, h)
+	if body := do(t, h, "GET", "/pair?code="+userCode, "", "").Body.String(); strings.Contains(body, "<script") {
+		t.Fatal("script on the page with the code filled in")
+	}
+}