notwaldorf / cat-dns Goto Github PK

54.197.244.191 is down, I am even trying to ping it but no response

The issues I've opened have been filed in good humour, in case you're interested in figuring ways to handle them. I also have patches for them, but wasn't sure if that would be some kind of spoiler for the enjoyment of tinkering with low-level protocols.

Why cats ?
why not any other thing or animals ?

Is this because CATS have ESP ?

or any other reason ?

&& why intel-coders love CATS so much ?
I can't figure it out..

PS I don't hate cats, I love wild-cats

:-D

The cat-dns query name parser assumes that the query name is at the end of the DNS query, minus 4 bytes. This doesn't work if the query includes an EDNS0 option. See RFC2671, EDNS0 options show up as OPT records in the additional section of a query. To parse the query name, you need to start 12 bytes in to the message (after the header) and then add each label, so; www.example.com appears on the wire as;

\3www\7example\3com\0

so the full qname length in bytes is is 3 + 1 + 7 + 1 + 3 + 1 + 0 + 1 (the plus ones are for the byte encoding the label length) and iteration is needed.

Technically this math is valid only if the label length is a value <= 63 (otherwise it's a label-compressed pointer, and counts as one byte), but this can be ignored in the question section (which is never compressed).

cat-dns.js includes the http package, but doesn't seem to use it.

Hello,

It seems the server crashes when nmap is used when scanning the ports.

cat-dns.js behaves like an authoritative name-server, but does not set the AA bit. Surely cat-dns is authoritative about cats in dns.

cat-dns's answers don't include the original question, in violation of RFC1035. DNS answers must include the original question being asked. So the qd_count should be 1, the an_count should be 1 (since cats have just one IP address) and ar_count and ns_count should always be zero.

Per #5 cat-dns does not include the original question. One fix for this is to simply emit the question section and answer section in full, e.g.;

[12 byte header]
\3www\7example\3com\0\0\1\0\1
\3www\7example\3com\0\0\1\0\1\0\0\0\1\0\0\4\54\197\244\191

but DNS also supports label compression where labels can point to previous identical labels. See section 4.1.4. of RFC1035.