CRLFuzz

A fast tool to scan CRLF vulnerability written in Go

---

Resources

• Installation
  • from Binary
  • from Source
  • from GitHub
• Usage
  • Basic Usage
  • Flags
  • Target
    • Single URL
    • URLs from list
    • from Stdin
  • Method
  • Data
  • Adding Headers
  • Using Proxy
  • Concurrency
  • Silent
  • Verbose
  • Version
  • Library
• Help & Bugs
• License
• Version

Installation

from Binary

The installation is easy. You can download a prebuilt binary from releases page, unpack and run! or with

▶ curl -sSfL https://git.io/crlfuzz | sh -s -- -b /usr/local/bin

from Source

If you have go1.13+ compiler installed and configured:

▶ GO111MODULE=on go install github.com/dwisiswant0/crlfuzz/cmd/crlfuzz@latest

In order to update the tool, you can use -u flag with go get command.

from GitHub

▶ git clone https://github.com/dwisiswant0/crlfuzz
▶ cd crlfuzz/cmd/crlfuzz
▶ go build .
▶ mv crlfuzz /usr/local/bin

Usage

Basic Usage

Simply, CRLFuzz can be run with:

▶ crlfuzz -u "http://target"

Flags

▶ crlfuzz -h

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

Flag	Description
-u, --url	Define single URL to fuzz
-l, --list	Fuzz URLs within file
-X, --method	Specify request method to use (default: GET)
-o, --output	File to save results
-d, --data	Define request data
-H, --header	Pass custom header to target
-x, --proxy	Use specified proxy to fuzz
-c, --concurrent	Set the concurrency level (default: 25)
-s, --silent	Silent mode
-v, --verbose	Verbose mode
-V, --version	Show current CRLFuzz version
-h, --help	Display its help

Target

You can define a target in 3 ways:

Single URL

▶ crlfuzz -u "http://target"

URLs from list

▶ crlfuzz -l /path/to/urls.txt

from Stdin

In case you want to chained with other tools.

▶ subfinder -d target -silent | httpx -silent | crlfuzz

Method

By default, CRLFuzz makes requests with GET method. If you want to change it, you can use the -X flag.

▶ crlfuzz -u "http://target" -X "GET"

Output

You can also save fuzzing results to a file with -o flag.

▶ crlfuzz -l /path/to/urls.txt -o /path/to/results.txt

Data

If you want to send a data request using POST, DELETE. PATCH or other methods, you just need to use -d flag.

▶ crlfuzz -u "http://target" -X "POST" -d "data=body"

Adding Headers

May you want to use custom headers to add cookies or other header parts.

▶ crlfuzz -u "http://target" -H "Cookie: ..." -H "User-Agent: ..."

Using Proxy

Using a proxy, proxy string can be specified with a protocol:// prefix to specify alternative proxy protocols.

▶ crlfuzz -u "http://target" -x http://127.0.0.1:8080

Concurrency

Concurrency is the number of fuzzing at the same time. Default value CRLFuzz provide is 25, you can change it by using -c flag.

▶ crlfuzz -l /path/to/urls.txt -c 50

Silent

If you activate this silent mode with the -s flag, you will only see vulnerable targets.

▶ crlfuzz -l /path/to/urls.txt -s | tee vuln-urls.txt

Verbose

Unlike silent mode, it will display error details if there is an error with the -v flag.

▶ crlfuzz -l /path/to/urls.txt -v

Version

To display the current version of CRLFuzz with the -V flag.

▶ crlfuzz -V

Library

You can use CRLFuzz as a library.

package main

import (
	"fmt"

	"github.com/dwisiswant0/crlfuzz/pkg/crlfuzz"
)

func main() {
	target := "http://target"
	method := "GET"

	// Generates a potentially CRLF vulnerable URLs
	for _, url := range crlfuzz.GenerateURL(target) {
		// Scan against target
		vuln, err := crlfuzz.Scan(url, method, "", []string{}, "")
		if err != nil {
			panic(err)
		}

		if vuln {
			fmt.Printf("VULN! %s\n", url)
		}
	}
}

Help & Bugs

If you are still confused or found a bug, please open the issue. All bug reports are appreciated, some features have not been tested yet due to lack of free time.

License

CRLFuzz released under MIT. See LICENSE for more details.

Version

Current version is 1.4.0 and still development.