Le 20 juil. 2017 à 23:13, Peter Bowen <[email protected]<mailto:[email protected]>> a écrit :
On Jul 20, 2017, at 11:02 AM, Erwann Abalea <[email protected]<mailto:[email protected]>> wrote: Le 20 juil. 2017 à 16:52, Ryan Sleevi <[email protected]<mailto:[email protected]>> a écrit : On Thu, Jul 20, 2017 at 10:16 AM, Erwann Abalea <[email protected]<mailto:[email protected]>> wrote: Bonjour, Looking back in time on the list for a reason to allow for underscore in SAN:dNSName, I found basically 2 potential reasons: - allow things such as « _sip._tls.xxxxxxx.com<http://tls.xxxxxxx.com> » - provide certificates for names that are not internet routable, such as « m_staging9.xxxxxxx.com<http://xxxxxxx.com> » The first option is avoided here (and it’s fine), because this should go into an SRV-type entry (or in the SAN:URI for this example). The text of the proposed ballot opens the path to having underscores into the the « xxxxxx » portion. This path is closed later by the validation of domain authorization or control (except if method 3.2.2.4.11 is used). Text in 7.1.4.2.1 disallows FQDNs that contain a label within the class of R-LDH labels than don’t start with « xn-- ». IIUC, such domains are still allowed under some TLDs that don’t support IDNA (such as « in--valid.am », « in--valid.gov<http://valid.gov> », or « in--valid.co.uk<http://valid.co.uk> »). I just validated that Safari, Firefox, and Chrome (on MacOSX) are happy to connect to http://in--valid.mydomain.com (for a properly owned my domain.com<http://domain.com>). Is that the intention of the ballot to disallow CAs to provide certificates for such domains? Yes. See the terminology discussion in https://tools.ietf.org/html/rfc5890#section-2.3.1 (as well as Figure-1) . In effect, this prohibits CAs from issuing for Reserved LDH Labels - except for those explicitly noted (IDNA). I was just reading it. So valid names will be composed only of: - LDH labels that are correct A-labels (the (2) box) - NR-LDH labels (the box on top right) - a subset of NON-LDH labels: only the underscore will be authorized and only where an hyphen can be present; will « xn__something » be authorized? I read it as xn__something is allowed as it does not contain hyphens at all, so it is clearly not a Reserved LDH Label. Using censys.io and the following expression returns some currently valid certificates that contain a fake A-label while being valid names: parsed.extensions.subject_alt_name.dns_names:/(.*\.)?[^xX][^nN]--.*/ and tags: “trusted" Using the 5890 terminology, I believe this search finds Reserved LDH Labels that are not XN-labels. A “fake A-label” is one starting with xn-- but not containing a punycode string. Detecting fake A-label via regex is super hard, as it looks correct. The numbers found by this censys query are very close to what I found in CT logs. You can see the CA totals on the right; Censys is showing 20 while I found 13 in CT. Either number is a super small portion of the millions of trusted certificates. You’re right, they’re not fake A-labels, but R-LDH labels. With the following expression, there’s a list of registered domains that contain a double hyphen at 3rd and 4th position while not starting with xn: parsed.extensions.subject_alt_name.dns_names:/(.*\.)?[^xX][^nN]--[a-zA-Z0-9-]*\.[a-zA-Z]+/ Such certificates would then be considered as misissued. This is basically the same query as before but without “trusted”, right? It returns only names where the R-LDH labels is right below the TLD. Previous query returned all names containing an R-LDH label. So this query returns domain names that have been registered.
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