Warning

This protocol and module is experimental and can be changed or removed at any time. Use at own risk, security properties were not analyzed!

How it works¶

The module will look for NS target names formatted as:dot-{base32(sha256(SPKI))}....

For instance, Knot Resolver will detect NS names formatted like this

example.com NS dot-tpwxmgqdaurcqxqsckxvdq5sty3opxlgcbjj43kumdq62kpqr72a.example.com

and automatically discover that example.com NS supports DoT with the base64-encoded SPKI digest ofm+12GgMFIiheEhKvUcOynjbn3WYQUp5tVGDh7Snwj/Q=and will associate it with the IPs ofdot-tpwxmgqdaurcqxqsckxvdq5sty3opxlgcbjj43kumdq62kpqr72a.example.com.

In that example, the base32 encoded (no padding) version of the sha256 PIN istpwxmgqdaurcqxqsckxvdq5sty3opxlgcbjj43kumdq62kpqr72a, which whenconverted to base64 translates tom+12GgMFIiheEhKvUcOynjbn3WYQUp5tVGDh7Snwj/Q=.

Generating NS target names¶

To generate the NS target name, use the following command to generate the base32 encoded string of the SPKI fingerprint:

openssl x509 -in /path/to/cert.pem  -pubkey -noout|\openssl pkey -pubin -outform der|\openssl dgst -sha256 -binary|\base32| tr -d'='| tr'[:upper:]''[:lower:]'tpwxmgqdaurcqxqsckxvdq5sty3opxlgcbjj43kumdq62kpqr72a

Then add a target to your NS with:dot-${b32}.a.example.com

Finally, mapdot-${b32}.a.example.com to the right set of IPs.

......;; QUESTION SECTION:;example.com.      IN      NS;; AUTHORITY SECTION:example.com.3600  IN      NS      dot-tpwxmgqdaurcqxqsckxvdq5sty3opxlgcbjj43kumdq62kpqr72a.a.example.com.example.com.3600  IN      NS      dot-tpwxmgqdaurcqxqsckxvdq5sty3opxlgcbjj43kumdq62kpqr72a.b.example.com.;; ADDITIONAL SECTION:dot-tpwxmgqdaurcqxqsckxvdq5sty3opxlgcbjj43kumdq62kpqr72a.a.example.com.3600 IN A192.0.2.1dot-tpwxmgqdaurcqxqsckxvdq5sty3opxlgcbjj43kumdq62kpqr72a.b.example.com.3600 IN AAAA2001:DB8::1......

Example configuration¶

To enable the module, add this snippet to your config:

-- Start an experiment, use with cautionmodules.load('experimental_dot_auth')

This module requires standardbasexx Lua library which is typically provided bylua-basexx package.

Caveats¶

The module relies on seeing the reply of the NS query and as such will not workif Knot Resolver uses data from its cache. You may need to delete the cache before startingkresd to work around this.

The module also assumes that the NS query answer will return both the NS targets in the Authority section as well as the glue records in the Additional section.

Dependencies¶

• lua-basexx available in LuaRocks