Fix "Host is invalid" error when TLD >10 chars (#7948)

Fix “Host is invalid” error when TLD >10 chars (#7948)

Related to "Host is invalid" error when TLD is longer than 7 characters - bug - Discourse Meta.

Using Discourse v2.4.0.beta2 +119, I can’t add an host (when embedding, cf. /admin/customize/embedding) ending with .engineering. Turns out current regex limits to 10 characters.

Fix is dumb: it only allows for up to 24 chars, which is the current max TLD length, see

Maybe a better (and longer-term) fix would be to allow for up to 64 chars, which I understand comes from the RFC. I’m not at ease with regexes, so can’t be sure about it, but this suggestion seems pretty good:

rules of DNS labels are:

  • All labels are 1 to 63 characters, case insensitive A to Z, 0 to 9 and - (hyphen), all from ASCII.
  • No labels may start with a hyphen.
  • No top level domain label may start with a number.

That means a regexp for a valid domain name would look like:


Domains that are just a TLD are sufficiently bizarre as to be worth ignoring.

diff --git a/app/models/embeddable_host.rb b/app/models/embeddable_host.rb
index 545eeba..71b4478 100644
--- a/app/models/embeddable_host.rb
+++ b/app/models/embeddable_host.rb
@@ -63,7 +63,7 @@ class EmbeddableHost < ActiveRecord::Base
   def host_must_be_valid
-    if host !~ /\A[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,10}(:[0-9]{1,5})?(\/.*)?\Z/i &&
+    if host !~ /\A[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,24}(:[0-9]{1,5})?(\/.*)?\Z/i &&
        host !~ /\A(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})(:[0-9]{1,5})?(\/.*)?\Z/ &&
        host !~ /\A([a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.)?localhost(\:[0-9]{1,5})?(\/.*)?\Z/i
       errors.add(:host, I18n.t('errors.messages.invalid'))

GitHub sha: dcb0e5f1