ACE representation of email address with IDN considered invalid

[manuelmeurer]

When I enter an email with an IDN like "test@umläut.com" in a form in my Rails app and submit it, the backend receives the ACE representation "test@xn--umlut-ira.com", which is considered invalid by email_validator in strict mode:

EmailValidator.default_options[:mode] = :strict

> EmailValidator.valid?("test@xn--umlut-ira.com")
false

> EmailValidator.valid?("test@umläut.com")
true

Is this a bug?

[karlwilbur]

Yeah, I see what you are saying. International Domain Names (IDN), when ASCII-Compatible Encoded (ACE), are getting double dashes in them. I think that is why they are getting rejected in strict mode.

[karlwilbur]

https://github.com/K-and-R/email_validator/blob/develop/lib/email_validator.rb#L126-L128

I expected GitHub this to include the lines of code (below) just by adding in the link to them (above). It did not, so here they are:

    def label_contains_no_more_than_one_consecutive_hyphen
      '(?!.*?--.*$)'
    end

[karlwilbur]

So, this behavior is very much intentional, but may be a mistake. Let me look at the RFC again.

[karlwilbur]

So, I am thinking that rejecting consecutive hyphens was my mistake. I cannot see where they are not allowed in domain names.

I do see that India's Domain Registration Service does say that:

Two hyphens together is usually not permitted and also hyphens cannot appear at both third and fourth positions.

• • https://registry.gov.in/domiannamingcon.php

In fact, RFC 3696 clearly indicates that double hyphens preceded by "xn" should be expected. (https://www.rfc-editor.org/rfc/rfc3696#section-5)

So, definitely a bug.

Thank you for bringing it to my attention.

[karlwilbur]

@manuelmeurer Fixed in version 2.2.4

[manuelmeurer]

Brilliant, thanks so much for the quick fix! ❤️