fix(09): WR-11 reject ambiguous admin logins and cross-field login or email collisions

modules/cabana/auth.go

@@ -381,17 +381,22 @@ func adminBlacklist(app *backpack.App) bouncer.BlacklistStore {
 	return bouncer.NewPostgresBlacklist(sqlDB, backendJWTBlacklistTable)
 }
 
+// findBackendLogin resolves a login identifier (a login or an email) to one
+// administrator. An identifier that matches two rows, such as one admin's login
+// equal to another's email, resolves to nobody: it is reported as not found, so
+// the caller answers it like any wrong credential instead of letting the lowest
+// id win and lock the other admin out.
 func findBackendLogin(db *gorm.DB, identifier string) (BackendUser, bool, error) {
 	email := strings.ToLower(identifier)
-	var user BackendUser
-	err := db.Preload("Role").Where("login = ? OR lower(email) = ?", identifier, email).First(&user).Error
-	if errors.Is(err, gorm.ErrRecordNotFound) {
-		return BackendUser{}, false, nil
-	}
+	var users []BackendUser
+	err := db.Preload("Role").Where("login = ? OR lower(email) = ?", identifier, email).Order("id").Limit(2).Find(&users).Error
 	if err != nil {
 		return BackendUser{}, false, err
 	}
-	return user, true, nil
+	if len(users) != 1 {
+		return BackendUser{}, false, nil
+	}
+	return users[0], true, nil
 }
 
 func (s *service) db() (*gorm.DB, error) {

modules/cabana/auth_test.go

@@ -553,3 +553,26 @@ func itoa(id uint) string {
 func adminAPI(rel string) string {
 	return cabana.DefaultAdminPrefix + "/api/v1" + rel
 }
+
+// TestLoginAmbiguousIdentifier pins WR-11: an identifier that is one admin's
+// login and another's email resolves to nobody (a plain 401), so neither admin
+// is silently locked out by the other; each can still sign in by the
+// unambiguous field.
+func TestLoginAmbiguousIdentifier(t *testing.T) {
+	gdb := adminGorm(t)
+	h := adminHandler(t, gdb, nil)
+	insertAdmin(t, gdb, "ambig@amb.test", "owner-a@amb.test", "password-of-a", true, false)
+	insertAdmin(t, gdb, "owner-b", "ambig@amb.test", "password-of-b", true, false)
+	for _, password := range []string{"password-of-a", "password-of-b"} {
+		rec := postJSON(t, h, adminAPI("/auth/login"), map[string]string{"login": "ambig@amb.test", "password": password})
+		if rec.Code != http.StatusUnauthorized {
+			t.Fatalf("ambiguous identifier with %q = %d %s, want 401", password, rec.Code, rec.Body.String())
+		}
+	}
+	if rec := postJSON(t, h, adminAPI("/auth/login"), map[string]string{"login": "owner-a@amb.test", "password": "password-of-a"}); rec.Code != http.StatusOK {
+		t.Fatalf("admin A by email = %d %s", rec.Code, rec.Body.String())
+	}
+	if rec := postJSON(t, h, adminAPI("/auth/login"), map[string]string{"login": "owner-b", "password": "password-of-b"}); rec.Code != http.StatusOK {
+		t.Fatalf("admin B by login = %d %s", rec.Code, rec.Body.String())
+	}
+}

modules/cabana/commands.go

@@ -69,7 +69,10 @@ func adminCreate(ctx context.Context, app *backpack.App, in bonfire.Input, out b
 				return err
 			}
 			var existing int64
-			if err := tx.Model(&BackendUser{}).Where("login = ? OR lower(email) = ?", login, email).Count(&existing).Error; err != nil {
+			// Check both fields against both values: a new login equal to an
+			// existing email (or the reverse) would make the login identifier
+			// ambiguous, so neither admin could rely on it.
+			if err := tx.Model(&BackendUser{}).Where("login IN (?, ?) OR lower(email) IN (?, ?)", login, email, strings.ToLower(login), email).Count(&existing).Error; err != nil {
 				return err
 			}
 			if existing > 0 {

modules/cabana/commands_test.go

@@ -195,3 +195,34 @@ func (f flagInput) Flag(name string) (string, bool) {
 }
 
 func (f flagInput) Flags(string) []string { return nil }
+
+// TestAdminCreateRejectsCrossFieldCollision pins WR-11: admin:create refuses a
+// login that equals another admin's email and an email that equals another
+// admin's login, because either makes the login identifier ambiguous.
+func TestAdminCreateRejectsCrossFieldCollision(t *testing.T) {
+	gdb := adminGorm(t)
+	app := commandApp(t, gdb)
+	create := commandByName(t, cabana.RuntimeCommands(app), "admin:create")
+	out := bonfire.NewOutput(nil, &bytes.Buffer{}, &bytes.Buffer{})
+	const password = "correct-horse-battery"
+	if err := create.Run(context.Background(), flagInput{flags: map[string]string{
+		"email": "a-xf@example.test", "login": "login-xf@example.test", "password": password,
+	}}, out); err != nil {
+		t.Fatal(err)
+	}
+	for name, flags := range map[string]map[string]string{
+		"email equals an existing login": {"email": "login-xf@example.test", "login": "b-xf"},
+		"login equals an existing email": {"email": "c-xf@example.test", "login": "a-xf@example.test"},
+		"email differs only by case":     {"email": "A-XF@example.test", "login": "d-xf"},
+	} {
+		flags["password"] = password
+		err := create.Run(context.Background(), flagInput{flags: flags}, out)
+		if err == nil || !strings.Contains(err.Error(), "already exists") {
+			t.Fatalf("%s: err = %v, want an already-exists refusal", name, err)
+		}
+	}
+	var n int64
+	if err := gdb.Model(&cabana.BackendUser{}).Where("login LIKE ?", "%-xf%").Count(&n).Error; err != nil || n != 1 {
+		t.Fatalf("admins after refused creates = %d, %v; want 1", n, err)
+	}
+}