This repo is more of me sharing an idea with everyone. Head over to bass for the finished tool :)

massNS

A tool that turns the authoritative nameservers of DNS providers to resolvers and resolves the target domain list. As of now the tool only resolves the A record for the list of domains.

Why Authoritative Nameservers?

• They are always reliable and always up!
• Sometimes the public dns resolvers would sprout up junk records. Authoritative nameservers would never do that.
• Every DNS server is rate-limited. They have to be. Hence we need numbers at our side. This tool tries to do just that by poking at the DNS providers infrastructure and asking for a whole lot of active authoritative DNS servers to resolve one of their clients( our target ).

This is more of a Proof Of Concept turned into a tool.

Let me know what your tests show and what issues you run into ? Is this a vialble approach ? Can something more be done ?

Basic Idea

The idea behind this tool is a product of observing how an authoritative nameserver of TARGET1 would also resolve TARGET2 provided both belonged to the same DNS Provider. So using this we could for a TARGET collect a huge bunch of authoritative nameservers and use them as resolvers instead of using the public dns resolvers.

Proof

1. Fetch bugcrowd.com nameservers

$ host -t ns bugcrowd.com
bugcrowd.com name server edna.ns.cloudflare.com.
bugcrowd.com name server lee.ns.cloudflare.com.

2. Fetch upserve.com nameservers

$ host -t ns upserve.com
upserve.com name server ulla.ns.cloudflare.com.
upserve.com name server jay.ns.cloudflare.com.

3. Resolve bugcrowd.com using upserve's nameserver jay.ns.cloudflare.com

$ nslookup bugcrowd.com jay.ns.cloudflare.com
Server:		jay.ns.cloudflare.com
Address:	173.245.59.123#53

Name:	bugcrowd.com
Address: 104.20.5.239
Name:	bugcrowd.com
Address: 104.20.4.239
Name:	bugcrowd.com
Address: 2606:4700:10::6814:5ef
Name:	bugcrowd.com
Address: 2606:4700:10::6814:4ef

4. Resolve docs.bugcrowd.com using upserve's nameserver jay.ns.cloudflare.com

$ nslookup docs.bugcrowd.com jay.ns.cloudflare.com
Server:		jay.ns.cloudflare.com
Address:	173.245.59.123#53

Name:	docs.bugcrowd.com
Address: 104.20.5.239
Name:	docs.bugcrowd.com
Address: 104.20.4.239
Name:	docs.bugcrowd.com
Address: 2606:4700:10::6814:5ef
Name:	docs.bugcrowd.com
Address: 2606:4700:10::6814:4ef

5. Repeating the same for upserve.com . Resolving upserve.com using bugcrowd's nameserver edna.ns.cloudflare.com

$ nslookup upserve.com edna.ns.cloudflare.com
Server:		edna.ns.cloudflare.com
Address:	173.245.58.109#53

Name:	upserve.com
Address: 35.221.46.9

Observation

As seen above how the authoritative nameserver's aren't tied down to their specific domain names, we could leverage the way these DNS providers are configured. We could probe into the IP range of the respective DNS Providers > grab all the active DNS servers in their range > use them as resolvers against our target list. All these servers would answer authoritatively due to their configuration as observed.

Requirements

• ipcalc

$ sudo apt-get install ipcalc

• massdns
• jq
• masscan

Tool Usage

$ cd massNS
$ chmod +x massns.sh
$ ./massns.sh target.com /path/to/target/domains

Output

• Generic output

• Only IP addresses

• Stats at the end!

Exceptions

• awsdns seems to not allow this.
• Custom nameserver like the one's employed by twitter (twtrdns.net) ,facebook etc. They might be hosted on services like amazon which would straight up REFUSE

DNS Providers :

DNS providers that allow this are :

• *.ns.cloudflare.com
• *.*.dynect.com/net
• *.ultradns.net/org/biz/com
• dnsimple and a lot more to be found.

As of now the above DNS providers are found to be allowing this. Make sure your target employs atleast one of these. To find that out , host -t ns target.com | grep 'ns\.cloudflare\|dynect\dnsimple\|ultradns'

Test Case

Against Paypal the tool could gather 698 authoritative nameservers turned resolvers, a combination of dns servers from both dynect & ultradns a spaypal employs them.

Thanks

Kudos to Patrik Hudak for some good suggestions and help.

P.S : This is purely experimental. Please do share what you think of this approach. Thanks!