Mastering gau: How to Install and Utilize gau for Effective Web Reconnaissance

Security testers and ethical hackers utilize their instruments to maximize the results in the field of web application hacking. One such important tool is the gau which means Gathering of URLs and which can be described as the means of finding out possible attack vectors. In this post, we’ll explain in further detail, what gau is, how you can install it, as well as guidelines on how most efficiently you can use gau when it comes to bug hunting and bug bounty.

What is gau?

gau, short for GetAllURLs, is a powerful open-source tool developed by the team at lc. It aids bug finders and developers to obtain URL lists from web archives including way back machine, common crawl and more. As we have noted, these URLs may point to dormant straggler endpoints, old application releases or installation directories and others which are nominally contained but are potential security exposures.

Key Features of gau:

• Wide Data Source Integration: Gather links from more than one archive, so that no archive is missed out during the scanning process.
• Fast and Lightweight: gau has been written in Go language and therefore is very efficient and performs the computation very fast.
• Simple Interface: Easy to use command-line options for the layman end-user.
• Highly Customizable: Refine information to targeted sets by such elements as parameters and flags.

Why Apply gau in Bug Hunting?

1. Discover Hidden Endpoints: Identify other end points which are probably not configurable from the current over-arching web version.
2. Identify Deprecated APIs: Older URLs may still be live to get a feeling about weaknesses stemming from stale code.
3. Automate Reconnaissance: This will help save time as a result of automation of the process of linking from the archived URLs.

How to Install gau

The installation of gau is relatively simple, if one has the pre requisites. Follow these step-by-step instructions to get started:

Step 1: Install Go

It is written in Go language, so there are a few things you have to do to get it installed.

On Linux:

sudo apt update;
sudo apt install golang-go -y

On macOS:

brew install go

After installation, verify it with:

go version

Step 2: Install gau from source

Use the following command to install gau:

go install github.com/lc/gau/v2/cmd/gau@latest

Use the command below to make it run from any terminal location

sudo mv ~/go/gau /usr/local/bin

Step 3: Setup .toml file

curl https://raw.githubusercontent.com/lc/gau/refs/heads/master/.gau.toml > ~/.gau.toml

Step 4: Verify the Installation

Once installed, check if gau is working by running:

gau --version

This command should give details of version of gau.

Basic Commands and Usage

gau ,however is now established, therefore it’s now about how to get the best out of it.

Fetch URLs for a Target Domain

The simplest command fetches all available URLs for a domain:

gau example.com

or

echo "example.com" | gau

Fetch Only Subdomains

gau can also help you focus on subdomains:

gau --subs example.com

Combine gau with Other Tools

Combine gau with other tools like gf (Gf-Patterns) for advanced filtering:

gau example.com | gf xss

Advanced Techniques

Using gau in Automated Recon

You can integrate gau into your recon scripts for automation:

#!/bin/bash
domain=$1
mkdir -p recon/$domain
gau $domain | tee recon/$domain/urls.txt

Combining gau with Wayback URLs

For an even larger set of results, combine gau with waybackurls:

gau example.com | waybackurls > combined_urls.txt

Identify Parameters for Vulnerability Testing

gau helps identify parameterized URLs, which are great targets for injection attacks:

gau example.com | grep '?'

Why we use gau?

Locate Deprecated Pages

Web archives typically provide URLs of pages that have been removed from other active uses. These may reveal information or improper configurations connected with the product.

Population of Client-Side Vulnerabilities

For collection of .js files use gau and them thoroughly for critical information or security vulnerabilities.

Data points and insights: Misconfigured Endpoints

URLs saved in an archive can go to test environments or an incorrectly configured admin panel.

How gau can be Utilized to the Fullest

1. Use Proxies for Large Targets: For large domains, pass route requests through a proxy if you do not want to be rate-limited.
2. Combine with Other Recon Tools: When used together with gooscan, jmptr, map, and portvista, leverage gau in combination with wordlists amass, subfinder, and httpx for further recon.
3. Validate URLs: Sometimes we collect URLs and which are not active anymore, so make sure and validate it using tools like httprobe.

Mistakes Made and Solutions to Them

1. Fetching Fewer URLs: Examine the sources for which gau is designed to provide frequency. Some of the archives may contain less data in the particular domains of the objects.
2. Compatibility Issues: Go Version Go on to check whether you are using the latest Go version. Newer releases of Go could be needed by gau.

gau is of huge importance in the world of bug hunting ethical hackers. It can obtain files that were stored at specific URLs in the past, which in turn gives the tool truly powerful insight into the applications retrieved based on URLs, opening up previously unseen exploitable vulnerabilities.

No matter if you’re a beginner in bug hunting or seek to improve your experience, gau will definitely be helpful. Therefore, Install it, and check out all the nooks and crannies of your target applications!

If you found this guide helpful, share it with fellow hackers and let us know your favorite use cases for gau in the comments!

Mastering gau: How to Install and Utilize gau for Effective Web Reconnaissance