How to provide custom TXT records in class 3 (CHAOS) using BIND9.

Introduction

Query for a TXT resource record in class 3 (CHAOS) for the domain name hostname.bind
or any other version.bind, authors.bind, and id.server.

$ dig chaos txt hostname.bind @10.10.1.18 +short

"voyager.octocat.lab"

These zones are defined defined inside bin/named/config.c source file.

"#\n\
#  Zones in the \"_bind\" view are NOT counted in the count of zones.\n\
#\n\
view \"_bind\" chaos {\n\
	recursion no;\n\
	notify no;\n\
	allow-new-zones no;\n\
	max-cache-size 2M;\n\
\n\
	# Prevent use of this zone in DNS amplified reflection DoS attacks\n\
	rate-limit {\n\
		responses-per-second 3;\n\
		slip 0;\n\
		min-table-size 10;\n\
	};\n\
\n\
	zone \"version.bind\" chaos {\n\
		type primary;\n\
		database \"_builtin version\";\n\
	};\n\
\n\
	zone \"hostname.bind\" chaos {\n\
		type primary;\n\
		database \"_builtin hostname\";\n\
	};\n\
\n\
	zone \"authors.bind\" chaos {\n\
		type primary;\n\
		database \"_builtin authors\";\n\
	};\n\
\n\
	zone \"id.server\" chaos {\n\
		type primary;\n\
		database \"_builtin id\";\n\
	};\n\
};\n\
"

BIND configuration

Ensure that all zones are in views.

$ sudo cat  /etc/bind/named.conf

// This is the primary configuration file for the BIND DNS server named.
//
// Please read /usr/share/doc/bind9/README.Debian.gz for information on the 
// structure of BIND configuration files in Debian, *BEFORE* you customize 
// this configuration file.
//
// If you are just adding zones, please do that in /etc/bind/named.conf.local

include "/etc/bind/named.conf.options";
include "/etc/bind/named.conf.local";

view "default" {
  include "/etc/bind/named.conf.default-zones";
};

Load chaos zone.

$ sudo cat /etc/bind/named.conf.local 

//
// Do any local configuration here
//

// Consider adding the 1918 zones here, if they are not used in your
// organization
//include "/etc/bind/zones.rfc1918";

include "/etc/bind/zones.chaos";

Define chaos zone.

$ cat /etc/bind/zones.chaos

//
// chaos zone
//

view "chaos" chaos  {
  recursion no;
  notify no;
  allow-new-zones no;
  max-cache-size 2M;

  # Prevent use of this zone in DNS amplified reflection DoS attacks
  rate-limit {
    responses-per-second 3;
    slip 0;
    min-table-size 10;
  };

  zone "bind" chaos {
    type primary;
    file "/etc/bind/db.bind";
    allow-update { none; };
  };

  zone "server" chaos {
    type primary;
    file "/etc/bind/db.server";
    allow-update { none; };
  };
};

Define BIND data file for bind zone.

$ cat /etc/bind/db.bind

;
; BIND data file for chaos class, bind zone
;
$TTL      604800
@         CH      SOA     localhost. root.localhost. (
                              2         ; Serial
                         604800         ; Refresh
                          86400         ; Retry
                        2419200         ; Expire
                         604800 )       ; Negative Cache TTL
;
@         CH  NS  localhost.
version   CH  TXT "[REDACTED]"
authors   CH  TXT "[REDACTED]" 
;hostname CH  TXT "[REDACTED]"

Define BIND data file for server zone.

$ cat /etc/bind/db.server 

;
; BIND data file for chaos class, server zone
;
$TTL    604800
@       CH      SOA     localhost. root.localhost. (
                              2         ; Serial
                         604800         ; Refresh
                          86400         ; Retry
                        2419200         ; Expire
                         604800 )       ; Negative Cache TTL
;
@       CH      NS      localhost.
id      CH      TXT     "[REDACTED]"
loc     CH      TXT     "local network"

Check configuration syntax.

$ named-checkconf

Restart BIND server.

$ sudo systemctl restart named

Query TXT records

Query for a TXT resource record in chaos class.

Existing record.

$ dig chaos txt version.bind @10.10.1.18 +short

"[REDACTED]"

The nonexisting record will return nothing as expected.

$ dig chaos txt hostname.bind @10.10.1.18 +short

Define custom records to provide additional data.
$ dig ch txt loc.server @10.10.1.18 +short

"local network"

Additional notes
Requirements for a Mechanism Identifying a Name Server Instance