6 ms·
Even without CT, you're still setting public DNS records -- so better yet, don't rely on "internal" hostnames staying private if you want them publicly trusted.
by mholt 8y ago
Even without CT, you're still setting public DNS records -- so better yet, don't rely on "internal" hostnames staying private if you want them publicly trusted. Full stop.
- organsnyder 8y agoIt's very common for internal hostnames to be resolvable only internally (such as with split-zone or dedicated internal DNS servers). Edit: Or do you mean as part of the challenge-response mechanism? Yeah, that would have to be public.
- zeeZ 8y agoOnly needs to be public for the challenge though. We use split DNS with an external server that has an empty zone. Internal clients are limited to setting their respective _acme-challenge.subdomain TXT record and delete it afterwards.
- someone13 8y agoOut of curiosity, how is this implemented?
- w7 8y agoNot the person you asked, but: Besides possibly being a function of a provider's API; DNS server security policies can be used to limit updates to certain domains and/or record types based on preshared key. Since the DNS-01 challenge only needs to make a TXT record with a predetermined name you can configure a zone like so (using BIND syntax as an example): key "example-key" { algorithm hmac-sha512; secret <KEY_HERE>; }; zone { ... update-policy { grant "example-key" name _acme-challenge.example.com TXT; }; }; another option is to have a CNAME from _acme-challenge.example.com to a dedicated challenge zone like challenges.example.com that has similar restrictions. This coupled with something like acme.sh makes it easy and relatively secure for machines to generate their own certificates.
- isostatic 8y agoIt is common, but as dns over https becomes standard it won’t be able to be.
- organsnyder 8y agoWhy would that preclude the ability to host certain zones only on internal DNS servers?
- yjftsjthsd-h 8y agoIt appears that some clients just universally query third-party servers, thereby giving out a list of every host name that they're looking for to a third party.
- organsnyder 8y agoNot enterprise devices, though. Some enterprise networks even block third-party DNS servers (yes, even over HTTPS—all traffic must go through the corporate proxy).
- isostatic 8y agoIf the default option allows a fallback then yes, only split dns (where you get different results internal and externally) will be affected. However how long before the default option is via https only.
- organsnyder 8y agoI still don't understand. How does DNS over HTTPS differ from DNS over port 53 in a way that would impact the ability to host internal zones (or even split DNS)?
- tracker1 8y agoConsidering how many office networks use 192.168.. or 10..., I'm not sure that in practice you're REALLY* leaking all that much... I mean it's a little bit of a hint, but if you can control a bridged device with internal network access, you'll probably get the same info (roughly) from a port scan. The "breach of info" is overblown imho.
- pawal 8y agoIn practice internal only DNS names will always leak to external resolvers in one way or another. Pretending otherwise is very naive.