• This code detects cyclic dependecies in DNS zones
• It takes as input DNS zone files
• First developed by @gmmoura and @seb-at-nzrs, from SIDN Labs and InternetNZ.
• Significantly improved by all contributors
• We've publicly disclose the tsuNAME vulnerability on 2021-05-06. Check our technical report for more detials on CycleHunter

• Clean your resolver's cache before running CycleHunter
• Requires Python3.7 minimum

Required packages for Debian/Ubuntu

• CycleHunter users newer versions of packages than the ones shipped with Debian
• Please remove the packages below and install them again with pip
  • python3-tqdm python3-multiprocess python3-dnspython
• Also, install : *pip install async_lru

To analyze a full zone, you can use CycleHunter.py as below

python CycleHunter.py --zonefile <ZONEFILE> --origin <ORIGIN> --save-file <FILE_TO_SAVE_AFFECTED_DOMAINS> --base-dir <BASE_DIR> --workers <WORKERS>

Where

• ZONEFILE is the file with the zone you want to analyze
• ORIGIN is the zone represented by the ZONEFILE, for example, .COM or .NL
• FILE_TO_SAVE_AFFECTED_DOMAINS is a JSON file that in the end will have the list of domains affected by full cycles
• BASE_DIR is the base directory used to write the intermediate files
• WORKERS is the number of parallel works that will use to send queries

CycleHunter.py wraps all the steps below, but if you still want to run them by hand, the process is:

1. Extract all NS records from the zone file

• python largeZoneParser.py $zonefile $TLD $output1
  • e.g: python3 largeZoneParser.py /var/cache/bind/com.zone .com com-nses.csv

2. Query these NSes, and output those that timeout into $output2

• python CyclicDetector.py $output1 $output2

3. Scrutinize each timed out NS, either parent or child, and see if which ones are really cyclic dependent into output3

• python findCyclicDep.py $output2 $output3

• Note: $output3 is a json file with 3 categories of dependency. fullDep is the one very bad, but the other two can quickily become fullDep

4. Get only the fully cyclic dependent ones from output3

• python fullDepParser.py $output3 $output4

output4 has the zones that are cyclic dependent. These are likely parent zones of NSes

5. Determine how many zones are affected by cyclic dependency

   • python zoneMatcher.py $output4 $zoneFile $TLD $output5
   • Alternative version for com : zoneMatcher-com.py

output5 has all domains affected by cyclic dependency

docker build -t sidn/cyclehunter --no-cache .

docker run -it -v $(pwd):/data --rm sidn/cyclehunter pypy3 CycleHunter.py --zonefile /data/org.txt --origin ".org" --save-file /data/org-final.out --base-dir /data --workers 6

or to run specific step within the container as per the general instructions:

e.g.

docker run -it -v $(pwd):/data --rm sidn/cyclehunter pypy3 findCyclicDep.py /data/$output2 /data/$output3