chore: validate email addresses with dns

models/user.go

@@ -4,6 +4,7 @@ import (
 	"crypto/md5"
 	"fmt"
 	conf "github.com/muety/wakapi/config"
+	"github.com/muety/wakapi/utils"
 	"regexp"
 	"strings"
 	"time"
@@ -190,8 +191,9 @@ func ValidatePassword(password string) bool {
 	return len(password) >= 6
 }
 
+// ValidateEmail checks that, if an email address is given, it has proper syntax and (if not in dev mode) an MX record exists for the domain
 func ValidateEmail(email string) bool {
-	return email == "" || mailRegex.Match([]byte(email))
+	return email == "" || (mailRegex.Match([]byte(email)) && (conf.Get().IsDev() || utils.CheckEmailMX(email)))
 }
 
 func ValidateTimezone(tz string) bool {

routes/settings.go

@@ -178,7 +178,7 @@ func (h *SettingsHandler) actionUpdateUser(w http.ResponseWriter, r *http.Reques
 	}
 
 	if !payload.IsValid() {
-		return http.StatusBadRequest, "", "invalid parameters"
+		return http.StatusBadRequest, "", "invalid parameters - perhaps invalid e-mail address?"
 	}
 
 	if payload.Email == "" && user.HasActiveSubscription() {

scripts/email_checker.go

@@ -0,0 +1,55 @@
+package main
+
+// Usage example:
+// cat emails.txt go run email_checker.go > result.txt
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"net"
+	"os"
+	"regexp"
+	"strings"
+)
+
+const MailPattern = "[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\\.[a-zA-Z0-9-.]+"
+
+var mailRegex *regexp.Regexp
+
+func init() {
+	mailRegex = regexp.MustCompile(MailPattern)
+}
+
+func CheckEmailMX(email string) bool {
+	parts := strings.Split(email, "@")
+	if len(parts) != 2 {
+		return false
+	}
+	records, err := net.LookupMX(parts[1])
+	return len(records) > 0 && err == nil
+}
+
+func ValidateEmail(email string) bool {
+	return mailRegex.Match([]byte(email)) && CheckEmailMX(email)
+}
+
+func main() {
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		email := scanner.Text()
+		if email == "" {
+			return
+		}
+
+		if ValidateEmail(email) {
+			fmt.Printf("[+] %s\n", email)
+		} else {
+			fmt.Printf("[-] %s\n", email)
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		log.Fatal(err)
+	}
+}

utils/dns.go

@@ -0,0 +1,16 @@
+package utils
+
+import (
+	"net"
+	"strings"
+)
+
+// CheckEmailMX takes an e-mail address and verifies that an MX DNS record exists for its domain
+func CheckEmailMX(email string) bool {
+	parts := strings.Split(email, "@")
+	if len(parts) != 2 {
+		return false
+	}
+	records, err := net.LookupMX(parts[1])
+	return len(records) > 0 && err == nil
+}