Ensure email domain has valid MX record

Signed-off-by: Tamal Saha <[email protected]>

Author: tamalsaha

pkg/server/types.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/avct/uasurfer"
 	"github.com/google/uuid"
+	"golang.org/x/net/publicsuffix"
 	. "gomodules.xyz/email-providers"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
@@ -73,6 +74,13 @@ func (form LicenseForm) Validate() error {
 	if agree, _ := strconv.ParseBool(form.Tos); !agree {
 		return fmt.Errorf("user must agree to terms and services")
 	}
+	if apex, err := publicsuffix.EffectiveTLDPlusOne(Domain(form.Email)); err != nil {
+		return err
+	} else {
+		if err := DomainWithMXRecord(apex); err != nil {
+			return err
+		}
+	}
 	return nil
 }
 

pkg/server/utils.go

@@ -17,6 +17,7 @@ limitations under the License.
 package server
 
 import (
+	"errors"
 	"fmt"
 	"net"
 	"net/http"
@@ -29,6 +30,17 @@ import (
 	"k8s.io/klog/v2"
 )
 
+func DomainWithMXRecord(domain string) error {
+	records, err := net.LookupMX(domain)
+	if err != nil {
+		return err
+	}
+	if len(records) == 0 {
+		return errors.New("no MX records")
+	}
+	return nil
+}
+
 func IsEnterpriseProduct(product string) bool {
 	return strings.HasSuffix(strings.ToLower(product), "-enterprise")
 }