feat(pairing): include the Cloud home in linked pairing QRs

.changeset/cloud-qr-v3.md

@@ -0,0 +1,5 @@
+---
+"ftw": minor
+---
+
+Include the Cloud home id in a linked box's pairing QR so the web app can pair through FTW Cloud.

go/internal/appenroll/payload.go

@@ -33,8 +33,8 @@ const (
 
 	// PayloadVersionHome is v2 with a sixth segment: the home id at FTW
 	// Cloud, base64url of its 26 ASCII characters, so a new phone knows
-	// where to dial before any session with the box. No shipped app reads
-	// it; each parser takes exactly five segments of v2.
+	// where to dial before any session with the box. Both the web client
+	// and iPhone read this form.
 	PayloadVersionHome = "v3"
 
 	// PayloadOrigin is where the app is served. It is also the passkey RP
@@ -47,12 +47,9 @@ const (
 	MaxLANHintChars = 64
 )
 
-// QRNamesHome is the one switch that puts the home id in the QR, as v3. It
-// stays false until the apps parse v3 and those builds are out: ftw-app's
-// Enrollment.swift and Enrollment.kt, and ftw-webapp's enrollment.ts. A v3
-// QR before then stops pairing on every shipped app. Until it flips, a new
-// phone learns the home id from hello_ok.cloud on its first session.
-const QRNamesHome = false
+// QRNamesHome puts the Cloud home id in the QR, as v3. The web client needs
+// it to pair through Cloud; iPhone also reads v3. An unlinked box keeps v2.
+const QRNamesHome = true
 
 // SetHome tells enrolment where to find the home id at FTW Cloud, for a QR
 // that names it. fn returns "" while the box is not linked.
@@ -66,7 +63,7 @@ func (i *Identity) SetHome(fn func() string) {
 //
 // lanHint is where the box believes it can be reached on the local network,
 // and is allowed to be empty: a box that does not know its own address should
-// say nothing rather than guess, and the app falls back to the relay.
+// say nothing rather than guess. The Cloud home id does not depend on it.
 func (i *Identity) EnrollmentURL(code []byte, lanHint string) (string, error) {
 	return i.enrollmentURL(code, lanHint, QRNamesHome)
 }

go/internal/appenroll/payload_home_test.go

@@ -63,22 +63,16 @@ func TestAnUnlinkedBoxShowsV2(t *testing.T) {
 	}
 }
 
-// The QR stays v2 until every shipped app parses v3: ftw-app's
-// Enrollment.swift and Enrollment.kt and ftw-webapp's enrollment.ts each
-// take exactly five segments today. Flipping QRNamesHome is step 2's, and
-// this test is there to be changed with it.
-func TestTheQRStaysV2UntilTheAppsParseV3(t *testing.T) {
-	if QRNamesHome {
-		t.Fatal("QRNamesHome is on; check that ftw-app (iOS and Android) and ftw-webapp parse v3 in builds people have, then change this test")
-	}
+// A linked box gives a new client enough to pair with the relay blocked.
+func TestTheLinkedQRNamesItsCloudHome(t *testing.T) {
 	id, _ := newIdentity(t)
 	id.SetHome(func() string { return testHome })
 	code, _, _ := id.MintPairingCode(apiauth.RoleOwner, PairingTTL)
 	url, err := id.EnrollmentURL(code, "")
 	if err != nil {
 		t.Fatal(err)
 	}
-	if strings.Contains(url, base64.RawURLEncoding.EncodeToString([]byte(testHome))) || !strings.Contains(url, "#"+PayloadVersion+".") {
-		t.Fatalf("the QR names the home before the apps can read it: %q", url)
+	if !strings.Contains(url, "."+base64.RawURLEncoding.EncodeToString([]byte(testHome))) || !strings.Contains(url, "#"+PayloadVersionHome+".") {
+		t.Fatalf("the linked QR omits its Cloud home: %q", url)
 	}
 }

go/internal/appuplink/livebox_test.go

@@ -124,6 +124,7 @@ func TestLiveBoxForTheiPhone(t *testing.T) {
 	defer closeTun()
 	uplink.Tunnel().Attach(timedTun{inner: link, log: tunLog})
 	bound.Store(link)
+	enroll.SetHome(link.Home)
 	enroll.OnChange(link.RosterChanged)
 	enroll.OnPairingCode(link.RosterChanged)
 	ctx, cancel := context.WithCancel(context.Background())
@@ -170,13 +171,11 @@ func TestLiveBoxForTheiPhone(t *testing.T) {
 	}
 	link.RosterChanged()
 	time.Sleep(300 * time.Millisecond)
-	v2, err := enroll.EnrollmentURL(code, "")
+	pairURL, err := enroll.EnrollmentURL(code, "")
 	if err != nil {
 		t.Fatal(err)
 	}
-	// v3 by hand while appenroll.QRNamesHome stays off.
-	v3 := strings.Replace(v2, "#v2.", "#v3.", 1) + "." + base64.RawURLEncoding.EncodeToString([]byte(link.Status().Home))
-	if err := os.WriteFile(filepath.Join(dir, "pair.url"), []byte(v3), 0o600); err != nil {
+	if err := os.WriteFile(filepath.Join(dir, "pair.url"), []byte(pairURL), 0o600); err != nil {
 		t.Fatal(err)
 	}
 	t.Logf("box linked as %s; pairing link written", link.Status().Home)