SubFinder

SubFinder is a subdomain discovery tool that uses various techniques to discover massive amounts of subdomains for any target. It has been aimed as a successor to the sublist3r project. SubFinder uses Passive Sources, Search Engines, Pastebins, Internet Archives, etc to find subdomains and then it uses a permutation module inspired by altdns to generate permutations and resolve them quickly using a powerful bruteforcing engine. It can also perform plain bruteforce if needed. The tool is highly customizable, and the code is built with a modular approach in mind making it easy to add functionalities and remove errors.

Why?

This project began it's life as a Bug Bounty World slack channel discussion. We were talking about how the cornerstone subdomain tool at the time, sublist3r, appeared to have been abandoned. The goal of this project was to make a low dependancy, manageable project in Go that would continue to be maintained over time. I decided to rewrite the sublist3r project and posted about it. @codingo offered to contribute to the project and subfinder was born.

So finally after working hard, here is something that I hope you guys will ❤️.

Features

• Simple and modular code base making it easy to contribute.
• Fast And Powerful Bruteforcing Module (In Development)
• Powerful Permutation generation engine. (In Development)
• Many Passive Data Sources (CertDB, CertSpotter, crtsh, DNSDumpster, FindSubdomains, Hackertarget, Netcraft, PassiveTotal, PTRArchive, SecurityTrails, Threatcrowd, VirusTotal, Waybackarchive, Threatminer, Riddler)
• Multiple Output formats

Sources

Source	Usage
ask	Natively
certdb	Natively
certspotter	Natively
crtsh	Natively
dnsdumpster	Natively
findsubdomains	Natively
hackertarget	Natively
netcraft	Natively
passivetotal	With API key
ptrarchive	Natively
riddler	Natively
securitytrails	With API key
threatcrowd	Natively
threatminer	Natively
virustotal	With API key
waybackarchive	Natively

Usage

./subfinder -h 

This will display help for the tool. Here are all the switches it supports.

Flag	Description	Example
-b	Use bruteforcing top find subdomains	./subfinder -d example.com -b
-c	Don't show colored output	./subfinder -c
-d	Domain to find subdomains for	./subfinder -d example.com
-nw	Remove wildcard subdomains	./subfinder -nw
-o	Name of the output file (Optional)	./subfinder -o output.txt
-oJ	Write output in JSON format	./subfinder -o output.json -oJ
-r	Use recursive subdomain finding (default: true)	./subfinder -r
--set-config	Sets a configuration option	./subfinder --set-config example=something
--silent	Show only the subdomains found	./subfinder --silent
--sources	Comma separated list of sources to use (optional)	./subfinder --sources threatcrowd,virustotal
-t	Number of concurrent threads (Bruteforce)	./subfinder -t 10
--timeout	Seconds to wait until quitting connection	./subfinder --timeout 10
-v	Display verbose output	./subfinder -v
-w	Wordlist for doing bruteforcing and permutation	./subfinder -w words.txt

Installation Instructions

Direct Installation

The installation is easy. Git clone the repo and run go build.

go get github.com/ice3man543/subfinder

Running in a Docker Container

Git clone the repo, then build and run subfinder in a container with the following commands

• Clone the repo using git clone https://github.com/ice3man543/subfinder.git
• Build your docker container

docker build -t subfinder .

• After building the container, run the following.

docker run -it subfinder

The above command is the same as running -h

NOTE: Please follow the Post Install steps given after this to correctly configure the tool.

For example, this runs the tool against uber.com and output the results to your host file system:

docker run -v $HOME/.config/subfinder:/root/.config/subfinder -it subfinder -d uber.com > uber.com.txt

Post Installation Instructions

Subfinder will work after using the installation instructions however to configure Subfinder to work with certain services, you will need to have setup API keys. These following services do not work without an API key:

• Virustotal
• Passivetotal
• SecurityTrails

Theses values are stored in the $HOME/.config/subfinder/config.json file which will be created when you run the tool for the first time. To configure the services to use an API key, you need to use the tool with --set-config option which will allow you to set a configuration option. For example:

./subfinder --set-config VirustotalAPIKey=0x41414141
./subfinder --set-config PassivetotalUsername=hacker,PassivetotalKey=supersecret

If you are using docker, you need to first create your directory structure holding subfinder configuration file. You can either run the binary in your host system and let it create the directory structure of files, after which you can use --set-config flag to set the api values like before. Or you can run:

mkdir $HOME/.config/subfinder
cp config.json $HOME/.config/subfinder/config.json
nano $HOME/.config/subfinder/config.json (optional)

After that, you can pass it as a volume using the following sample command.

sudo docker run -v $HOME/.config/subfinder:/root/.config/subfinder -it subfinder -d freelancer.com

Now, you can also pass --set-config inside the docker to change the configuration options.

Acknowledgements

• @FranticFerret for his work on adding docker support.