Subfinder is a subdomain discovery tool that discovers valid subdomains for websites. Designed as a passive framework to be useful for bug bounties and safe for penetration testing.

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README.md

Fast passive subdomain enumeration tool.

Features • Install • Usage • API Setup • Library • Join Discord

Subfinder is a subdomain discovery tool that discovers valid subdomains for websites by using passive online sources. It has a simple modular architecture and is optimized for speed. subfinder is built for doing one thing only - passive subdomain enumeration, and it does that very well.

We have designed subfinder to comply with all passive sources licenses, and usage restrictions, as well as maintained a consistently passive model to make it useful to both penetration testers and bug bounty hunters alike.

Features

Fast and powerful resolution and wildcard elimination module
Curated passive sources to maximize results
Multiple Output formats supported (Json, File, Stdout)
Optimized for speed, very fast and lightweight on resources
STDIN/OUT support for integrating in workflows

Usage

subfinder -h

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

Flag	Description	Example
-all	Use all sources (slow) for enumeration	subfinder -d uber.com -all
-config	Configuration file for API Keys, etc	subfinder -config config.yaml
-d	Domain to find subdomains for	subfinder -d uber.com
-dL	File containing list of domains to enumerate	subfinder -dL hackerone-hosts.txt
-exclude-sources	List of sources to exclude from enumeration	subfinder -exclude-sources archiveis
-max-time	Minutes to wait for enumeration results (default 10)	subfinder -max-time 1
-nC	Don't Use colors in output	subfinder -nC
-nW	Remove Wildcard & Dead Subdomains from output	subfinder -nW
-ls	List all available sources	subfinder -ls
-o	File to write output to (optional)	subfinder -o output.txt
-oD	Directory to write enumeration results to (optional)	subfinder -oD ~/outputs
-oI	Write output in Host,IP format	subfinder -oI
-oJ	Write output in JSON lines Format	subfinder -oJ
-r	Comma-separated list of resolvers to use	subfinder -r 1.1.1.1,1.0.0.1
-rL	Text file containing list of resolvers to use	subfinder -rL resolvers.txt
-recursive	Enumeration recursive subdomains	subfinder -d news.yahoo.com -recursive
-silent	Show only subdomains in output	subfinder -silent
-sources	Comma separated list of sources to use	subfinder -sources shodan,censys
-t	Number of concurrent goroutines for resolving (default 10)	subfinder -t 100
-timeout	Seconds to wait before timing out (default 30)	subfinder -timeout 30
-http-proxy	Http Proxy	subfinder -http-proxy http://localhost:3128
-v	Show Verbose output	subfinder -v
-version	Show current program version	subfinder -version

Installation

Subfinder requires go1.14+ to install successfully. Run the following command to get the repo -

▶ GO111MODULE=on go get -v github.com/projectdiscovery/subfinder/v2/cmd/subfinder

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. The following services do not work without an API key:

Theses values are stored in the $HOME/.config/subfinder/config.yaml file which will be created when you run the tool for the first time. The configuration file uses the YAML format. Multiple API keys can be specified for each of these services from which one of them will be used for enumeration.

For sources that require multiple keys, namely Censys, Passivetotal, they can be added by separating them via a colon (:).

An example config file -

resolvers:
  - 1.1.1.1
  - 1.0.0.1
sources:
  - binaryedge
  - bufferover
  - censys
  - passivetotal
  - sitedossier
binaryedge:
  - 0bf8919b-aab9-42e4-9574-d3b639324597
  - ac244e2f-b635-4581-878a-33f4e79a2c13
censys:
  - ac244e2f-b635-4581-878a-33f4e79a2c13:dd510d6e-1b6e-4655-83f6-f347b363def9
certspotter: []
passivetotal:
  - sample-email@user.com:sample_password
securitytrails: []
shodan:
  - AAAAClP1bJJSRMEYJazgwhJKrggRwKA
github:
  - d23a554bbc1aabb208c9acfbd2dd41ce7fc9db39
  - asdsd54bbc1aabb208c9acfbd2dd41ce7fc9db39

Running Subfinder

To run the tool on a target, just use the following command.

▶ subfinder -d example.com

The verbose flag v can be used to display verbose information.

[bufferover] lutin.dima.example.com
[bufferover] izosimdima.example.com
[bufferover] glazkovdima.example.com
[bufferover] dengshima.example.com
[bufferover] wwwkima.example.com
[bufferover] proxima.example.com
[bufferover] mma.example.com
[bufferover] damidoma.example.com
[bufferover] nomerdoma.example.com
[bufferover] soti.croma.example.com

The -o command can be used to specify an output file.

▶ subfinder -d example.com -o output.txt

To run the tool on a list of domains, -dL option can be used. This requires a directory to write the output files. Subdomains for each domain from the list are written in a text file in the directory specified by the -oD flag with their name being the domain name.

▶ cat domains.txt
hackerone.com
google.com

▶ subfinder -dL domains.txt -oD ~/path/to/output
▶ ls ~/path/to/output

hackerone.com.txt
google.com.txt

You can also get output in json format using -oJ switch. This switch saves the output in the JSON lines format.

If you use the JSON format, or the Host:IP format, then it becomes mandatory for you to use the -nW format as resolving is essential for these output format. By default, resolving the found subdomains is disabled.

▶ subfinder -d hackerone.com -o output.json -oJ -nW
▶ cat output.json

{"host":"www.hackerone.com","ip":"104.16.99.52"}
{"host":"mta-sts.hackerone.com","ip":"185.199.108.153"}
{"host":"hackerone.com","ip":"104.16.100.52"}
{"host":"mta-sts.managed.hackerone.com","ip":"185.199.110.153"}

The subdomains discovered can be piped to other tools too. For example, you can pipe the subdomains discovered by subfinder to httpx httpx which will then find running http servers on the host.

▶ echo hackerone.com | subfinder -silent | httpx -silent

http://hackerone.com
http://www.hackerone.com
http://docs.hackerone.com
http://api.hackerone.com
https://docs.hackerone.com
http://mta-sts.managed.hackerone.com

Subfinder with docker

You can use the official dockerhub image at subfinder. Simply run -

▶ docker pull projectdiscovery/subfinder

The above command will pull the latest tagged release from the dockerhub repository.

If you want to build the container yourself manually, git clone the repo, then build and run the following commands

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

docker build -t projectdiscovery/subfinder .

If you are using docker, you need to first create your directory structure holding subfinder configuration file. After modifying the default config.yaml file, you can run:

▶ mkdir -p $HOME/.config/subfinder
▶ cp config.yaml $HOME/.config/subfinder/config.yaml
▶ nano $HOME/.config/subfinder/config.yaml

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

▶ docker run -v $HOME/.config/subfinder:/root/.config/subfinder -it projectdiscovery/subfinder -d example.com

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

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

Subfinder Go library

Usage example:

package main

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"io/ioutil"
	"log"

	"github.com/projectdiscovery/subfinder/v2/pkg/passive"
	"github.com/projectdiscovery/subfinder/v2/pkg/resolve"
	"github.com/projectdiscovery/subfinder/v2/pkg/runner"
)

func main() {
	config := runner.ConfigFile{
		// Use the default list of resolvers by marshaling it to the config
		Resolvers: resolve.DefaultResolvers,
		// Use the default list of passive sources
		Sources: passive.DefaultSources,
		// Use the default list of all passive sources
		AllSources: passive.DefaultAllSources,
		// Use the default list of recursive sources
		Recursive: passive.DefaultRecursiveSources,
	}

	runnerInstance, err := runner.NewRunner(&runner.Options{
		Threads:            10, // Thread controls the number of threads to use for active enumerations
		Timeout:            30, // Timeout is the seconds to wait for sources to respond
		MaxEnumerationTime: 10, // MaxEnumerationTime is the maximum amount of time in mins to wait for enumeration
		YAMLConfig:         config,
	})

	buf := bytes.Buffer{}
	err = runnerInstance.EnumerateSingleDomain(context.Background(), "projectdiscovery.io", []io.Writer{&buf})
	if err != nil {
		log.Fatal(err)
	}

	data, err := ioutil.ReadAll(&buf)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%s", data)
}

Resources

Recon with Me !!!

License

subfinder is made with 🖤 by the projectdiscovery team. Community contributions have made the project what it is. See the Thanks.md file for more details.

Read the disclaimer for usage at DISCLAIMER.md and contact us for any API removal.