Add a trailing dot to DNS domains by default to speed up discovery when a search domain is configured #418
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…nting the DNS search domain being added. Added a flag "--no-fqdn" that disables this behaviour and operates like the original implementation.
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nice catch thanks! |
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Summary
If a DNS search domain is configured in the system resolver, gobuster will re-issue queries for every NXDOMAIN result with the DNS search domain appended. This occurs even when using a custom resolver. This PR simply adds a trailing dot to the domain if one isn't already present, so the search domain isn't applied. It also adds a flag to revert this behaviour if required.
While it is possible to work around by removing the search domain from resolv, or stipulating a base domain with a trailing dot, this is not something I always remember to do.
Details
The current behaviour results in an extraneous query for each word that doesn't exist if a DNS search domain is configured, and the domain is not supplied with a trailing dot.
For example, with the following
/etc/resolv.conf:Running a simple test with four subdomains:
This ends up sending 20 queries. All queries that returned NXDOMAIN are re-issued with the search domain:
If we either remove the search domain from resolv, or supply a domain with a trailing dot (
-d example.com.) , this is cut down to 12 queries:On a larger wordlist, eliminating these extraneous queries results in a significant speedup:
With the code from the PR applied we don't need to supply the trailing dot by default.: