Dumping Active Directory DNS using adidnsdump
Any user can create new DNS records by default, any user can also list the child objects of a DNS zone by default. So we know a records is there, we just can’t query it using LDAP.
Querying records with adidnsdump
With adidnsdump, which you can get from my GitHub, it is possible to enumerate all records in the DNS zone. To get started, first display the zones in the domain where you are currently in with --print-zones. This will show which zones are present. Not all zones are interesting, for example forward, cache and stub zones don’t contain all the records for that domain. If you find these zones, it’s better to query the domain to which they actually belong. The output below shows that my test domain has only the default zones:
user@localhost:~/adidnsdump$ adidnsdump -u icorp\\testuser –print-zones icorp-dc.internal.corp
Password:
[-] Connecting to host…
[-] Binding to host
[+] Bind OK
[-] Found 2 domain DNS zones:
internal.corp
RootDNSServers
[-] Found 2 forest DNS zones:
..TrustAnchors
_msdcs.internal.corp
If we specify the zone to the tool (or leave it empty for the default zone), we will get a list of all the records. Records which can be listed but not read (so called “hidden” records) are shown but only with a question mark, as it is unknown which type of record is present and where it points to. The records are all saved to a file called records.csv.
To resolve the unknown records, specify the -r flag, which will perform an A query for all unknown records (you can easily change this to AAAA in the code if you’re in an IPv6 network). Several nodes which were blank before now suddenly have records:
If you don’t have a direct connection but are working via an agent, you can proxy the tool through socks and perform the DNS queries over TCP with the --dns-tcp flag.
Mitigations
You shouldn’t really rely on secrecy of your DNS records for security. If you really want to hide this information, removing the “List contents” permission for “Everyone” and “Pre-Windows 2000 Compatible Access” does prevent regular users from querying the entries, but this does require disabling inheritance on the DNS zone and may break stuff, so I don’t really recommend going that way. Monitoring for high volumes of DNS queries or enabling auditing on DNS zone listings may be a better way to deal with this, by detecting instead of blocking this kind of activity.
The tools
adidnsdump is available on GitHub and on PyPI (pip install adidnsdump). Right now the tool only dumps records to CSV files, but feel free to submit requests for alternate formats.
Sources
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