Lame delegation checking at scale!

Requires go1.18+.

go build

Usage of ./broken-dns:
  -expected-ns string
        comma-separated list of domains which we expect nameservers to be under, findings are logged otherwise
  -list string
        comma-separated list of domain lists
  -parallel uint
        number of worker threads to use (default 10)
  -verbose
        show verbose messages

./broken-dns -list domain_list.txt -expected-ns googledomains.com,google.com,markmonitor.com,google

Results are printed to stdout, and any logs, errors, or debug messages are printed to stderr. You can pipe these to different files to save each independently. ex: ./broken-dns $ARGS >results.txt 2>results.log.

Findings:

• ERROR: server: an unexpected error occurred while sending the DNS query to a specific nameserver on every retry attempt
• varying responses: one (or more) of the nameservers did not return all of the records the other nameservers for the name returned.
• ERROR querying authoritative: an unexpected error occurred while sending parallel requests to all authoritative nameservers. (this error will likely also include a more specific ERROR: server: as well)
• unexpected difference in nameservers: authoritative nameservers returned different results from parent non-authoritative nameservers
  • > extra nameservers returned by authoritative NS: if any of the authoritative nameservers returned any new or unexpected nameservers, they will be printed here
• lame delegation: a lame delegation was found, meaning a domain's NS records to not point to authoritative servers
• unexpected nameserver: only displayed with -expected-ns and one of the input domains nameservers are not subdomains of -expected-ns

The speed will largely depend on the argument to -parallel. The only real bottleneck is network latency, so this program can be extremely fast if given enough workers. However, if there are a lot of network errors, especially for any of the apex/parent/tld nameservers, then it will slow down considerably as these requests are retried.

You can use the following dig command to roughly verify the results of this program. The +trace flag is similar, but not quite as through as the tests this program performs. To check for Authoritative responses, look for the aa flag in the dig response output.

dig +trace +question +qr +comments +nodnssec -t NS -q $DOMAIN