check-names response fail;

Wed Aug 22 16:48:11 UTC 2018

So, the short answer is that check-names is pretty granular, doing
"check-names response fail" is just asking for trouble, for a resolver at
the Internet edge, since there's too much squirrely stuff out there. Most
folks just limit check-names "fail" to authoritative data (master or slave).

The longer answer is: this is an interesting standards-compliance question.
The rule is that a "hostname" can't contain an underscore. Owner names that
aren't "hostnames" are allowed to have underscores. I believe -- I could be
mistaken -- that owner names for MX records, for instance, can have
underscores. In some cases, underscores were *purposely* encoded into owner
names, for certain record types, *because* that way, they could never
collide with "hostnames". SRV records are an example of that.

But, in this case, the "hostname" is www.newegg.com -- no underscore. For
that matter, the owner name of the A record -- e5638.g.akamaiedge.net
-- doesn't
contain an underscore either. So, the only names that are involved in the
resolution of this name, that contain underscores, are *intermediate*
CNAMEs between the original name (www.newegg.com) and the ultimate owner of
the A record -- names that a user never sees or deals with when accessing
the resource. Does it therefore violate the "hostnames can't contain
underscores" rule or not? That's a very debatable question.

Having said that, however, Akamai violates a different rule by chaining
CNAMEs ("Domain names in RRs which point at another name should always
point at the primary name and not the alias" -- RFC 1034). In fact, their
whole business model is based on this standards-violation, and it's worked
very well for them.

Now, I don't really have a fundamental problem with Akamai, as a company;
we use them extensively, including their "Fast DNS" service, which
basically consists of replicating our zones to their DNS-CDN. But the
standards-purist in me still rankles at the fact that they're based on a
standards-violation.

                    - Kevin

On Wed, Aug 22, 2018 at 12:04 PM, Lee <ler762 at gmail.com> wrote:

> Validating input is good & rejecting invalid data is the way to go..
> but has the Internet moved on and check-names is now too restrictive?
>
> I have this bit in named.conf
>    check-names response fail;
>      # restrict the character set and syntax of domain names
>      # The rules for legal hostnames and mail domains are derived from
> RFC 952 and RFC 821 as modified by RFC 1123.
>
> which seems to be why I can't resolve www.newegg.com but 1.1.1.1 and
> 8.8.8.8 can
>
> C:\Users\Lee>dig www.newegg.com.
>
> ; <<>> DiG 9.11.4 <<>> www.newegg.com.
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 43232
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
>
> ;; OPT PSEUDOSECTION:
> ; EDNS: version: 0, flags:; udp: 4096
> ; COOKIE: 97fd73f55fd163f250da7a315b7d7e314d7b33f3eab3f468 (good)
> ;; QUESTION SECTION:
> ;www.newegg.com.                        IN      A
>
> ;; Query time: 62 msec
> ;; SERVER: 127.0.0.1#53(127.0.0.1)
> ;; WHEN: Wed Aug 22 11:16:01 Eastern Daylight Time 2018
> ;; MSG SIZE  rcvd: 71
>
> and this is what's logged
> security: error: client @000002112790F990 127.0.0.1#50079
> (www.newegg.com): check-names failure
> san_ssl-images.newegg.com.edgekey.net/A/IN
>
>
> 8.8.8.8 and 1.1.1.1 don't have a problem with "_" in the name:
>
> C:\Users\Lee>dig www.newegg.com. @8.8.8.8
>
> ; <<>> DiG 9.11.4 <<>> www.newegg.com. @8.8.8.8
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 681
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
>
> ;; OPT PSEUDOSECTION:
> ; EDNS: version: 0, flags:; udp: 512
> ;; QUESTION SECTION:
> ;www.newegg.com.                        IN      A
>
> ;; ANSWER SECTION:
> www.newegg.com.         215     IN      CNAME
> san_ssl-images.newegg.com.edgekey.net.
> san_ssl-images.newegg.com.edgekey.net. 3977 IN CNAME
> e5638.g.akamaiedge.net.
> e5638.g.akamaiedge.net. 19      IN      A       23.46.201.81
>
> ;; Query time: 15 msec
> ;; SERVER: 8.8.8.8#53(8.8.8.8)
> ;; WHEN: Wed Aug 22 11:16:16 Eastern Daylight Time 2018
> ;; MSG SIZE  rcvd: 143
>
> C:\Users\Lee>dig www.newegg.com. @8.8.8.8
>
> ; <<>> DiG 9.11.4 <<>> www.newegg.com. @8.8.8.8
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 681
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
>
> ;; OPT PSEUDOSECTION:
> ; EDNS: version: 0, flags:; udp: 512
> ;; QUESTION SECTION:
> ;www.newegg.com.                        IN      A
>
> ;; ANSWER SECTION:
> www.newegg.com.         215     IN      CNAME
> san_ssl-images.newegg.com.edgekey.net.
> san_ssl-images.newegg.com.edgekey.net. 3977 IN CNAME
> e5638.g.akamaiedge.net.
> e5638.g.akamaiedge.net. 19      IN      A       23.46.201.81
>
> ;; Query time: 15 msec
> ;; SERVER: 8.8.8.8#53(8.8.8.8)
> ;; WHEN: Wed Aug 22 11:16:16 Eastern Daylight Time 2018
> ;; MSG SIZE  rcvd: 143
>
>
> Thanks
> Lee
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