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TruffleHog Custom Detector Setup Guide

This guide will walk you through setting up a custom detector in TruffleHog to identify specific patterns unique to your project. For users of Trufflehog Enterprise, this guide applies to that environment as well.

Steps to Set Up a Custom Detector

  1. Create a Configuration File:

    • TruffleHog uses a configuration file, typically named config.yaml, to manage custom detector configuration.
    • If this file doesn't exist, create it in your system.

  2. Define the Custom Detector:

    • Open config.yaml with a text editor.
    • Add a new detector under the detectors section.

    Here's a template for a custom detector:

    # config.yaml
detectors:
  - name: HogTokenDetector
    keywords:
      - hog
    regex:
      token: '[^A-Za-z0-9+\/]{0,1}([A-Za-z0-9+\/]{40})[^A-Za-z0-9+\/]{0,1}'
    verify:
      - endpoint: http://localhost:8000/
        # 'unsafe' must be set to true if the endpoint uses HTTP
        unsafe: true
        headers:
          - "Authorization: super secret authorization header"

    Explanation:

    • name: A unique identifier for your custom detector.

    • keywords: An array of strings that, when found, trigger the regex search. If multiple keywords are specified, the presence of any one of them will initiate the regex search.

    • regex: Defines the patterns to identify potential secrets. You can specify one or more named regular expressions. For a detection to be successful, each named regex must find a match. Capture groups () within these regular expressions are used to extract specific portions of the matched text, enabling the detector to process and report on particular segments of the identified patterns.

    • verify: An optional section to validate detected secrets. If you want to verify or unverify detected secrets, this section needs to be configured. If not configured, all detected secrets will be marked as unverified. Read verification server examples

    Other allowed parameters:

    • primary_regex_name: This parameter allows you designate the primary regex pattern when multiple regex patterns are defined in the regex section. If a match is found, the match for the designated primary regex will be used to determine the line number. The value must be one of the names specified in the regex section. If not provided, the first regex name in sorted order will be used as the primary regex by default.
    • exclude_regexes_capture: This parameter allows you to define regex patterns to exclude specific parts of a detected secret. If a match is found within the detected secret, the portion matching this regex is excluded from the result.
    • exclude_regexes_match: This parameter enables you to define regex patterns to exclude entire matches from being reported as secrets. This applies to the entire matched string, not just the token.
    • entropy: This parameter is used to assess the randomness of detected strings. High entropy often indicates that a string is a potential secret, such as an API key or password, due to its complexity and unpredictability. It helps in filtering false-positives. While an entropy threshold of 3 can be a starting point, it's essential to adjust this value based on your project's specific requirements and the nature of the data you have.
    • exclude_words: This parameter allows you to specify a list of words that, if present in a detected string, will cause TruffleHog to ignore that string. This is a substring match and does not enforce word boundaries. It applies only to the token.
    • validations: This parameter lets you define extra validation rules for each regex specified in the regex option. These rules address limitations of Go's RE2 engine, such as the lack of lookahead support, and are applied after a regex match to help reduce false positives. Available validation options:
      • contains_digit: Ensures the match contains at least one numeric digit (0-9). Useful for API keys or tokens that must include numbers.
      • contains_lowercase: Ensures the match contains at least one lowercase letter (a-z). Common requirement for passwords and mixed-case tokens.
      • contains_uppercase: Ensures the match contains at least one uppercase letter (A-Z). Helps validate tokens that follow mixed-case conventions.
      • contains_special_char: Ensures the match contains at least one special character from the set !@#$%^&*()_+-=[]{}|;:,.<>?. Useful for complex passwords or encoded tokens.

    Here is an example of a custom detector using these parameters.

  3. Run TruffleHog with the Custom Detector:

    • Execute TruffleHog, specifying your configuration file:

      trufflehog filesystem <path_to_folder_or_file> --config=<path_to_file>/config.yaml

    • Replace <path_to_folder_or_file> with the path to the directory or file you want to scan, and <path_to_file> with the path to your config.yaml.

    • TruffleHog will scan the specified file or folder using the custom detector you've defined.

  4. Example:

    Let's use the template config provided above to search a file.

    Assume you have a file /tmp/data.txt with the following content:

    // this is a custom example
this file has some random text and maybe a secret
hog token: pOIAj9x47WT5qElx5JrI3e7O714HgaAIz2ck9sVn
// end of file

    In this file, the keyword hog exists, which will trigger the regex search. The string pOIAj9x47WT5qElx5JrI3e7O714HgaAIz2ck9sVn matches the regex pattern, so it should be detected.

    Run the following command:

    trufflehog filesystem /tmp --config=config.yaml

    The output should be similar to:

    🐷🔑🐷  TruffleHog. Unearth your secrets. 🐷🔑🐷

Found verified result 🐷🔑
Detector Type: CustomRegex
Decoder Type: PLAIN
Raw result: pOIAj9x47WT5qElx5JrI3e7O714HgaAIz2ck9sVn
File: /tmp/data.txt
Line: 3

    The Raw result contains the matched string. File is the file name where secret was detected and Line is the exact line in the file where that was found.

Verification Server Examples

Unless you run a verification server, secrets found by the custom regex detector will be unverified. Here is an example Python and Go implementation of a verification server for the above config.yaml file.

Python:

import json
from http.server import BaseHTTPRequestHandler, HTTPServer

AUTH_HEADER = 'super secret authorization header'

class Verifier(BaseHTTPRequestHandler):
    def do_GET(self):
        self.send_response(405)
        self.end_headers()

    def do_POST(self):
        try:
            if self.headers['Authorization'] != AUTH_HEADER:
                self.send_response(401)
                self.end_headers()
                return

            length = int(self.headers['Content-Length'])
            request = json.loads(self.rfile.read(length))
            self.log_message("%s", request)

            if not validateTokens(request['HogTokenDetector']['token']):
                self.send_response(200)
                self.end_headers()
            else:
                self.send_response(403)
                self.end_headers()
        except Exception:
            self.send_response(400)
            self.end_headers()

def validateTokens(token):
    return False  # Implement actual validation logic

with HTTPServer(('', 8000), Verifier) as server:
    try:
        server.serve_forever()
    except KeyboardInterrupt:
        pass

Go

package main

import (
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
)

const authHeader = "super secret authorization header"

type HogTokenDetector struct {
	Token string `json:"token"`
}

type RequestBody struct {
	HogTokenDetector HogTokenDetector `json:"HogTokenDetector"`
}

func validateTokens(token string) bool {
	return false // Implement actual validation logic
}

func verifierHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
		return
	}

	if r.Header.Get("Authorization") != authHeader {
		http.Error(w, "Unauthorized", http.StatusUnauthorized)
		return
	}

	body, err := io.ReadAll(r.Body)
	if err != nil {
		http.Error(w, "Bad Request", http.StatusBadRequest)
		return
	}
	defer r.Body.Close()

	var requestBody RequestBody
	if err := json.Unmarshal(body, &requestBody); err != nil {
		http.Error(w, "Bad Request", http.StatusBadRequest)
		return
	}

	log.Printf("Received Request: %+v", requestBody)

	if validateTokens(requestBody.HogTokenDetector.Token) {
		http.Error(w, "Forbidden", http.StatusForbidden)
	} else {
		w.WriteHeader(http.StatusOK)
	}
}

func main() {
	http.HandleFunc("/", verifierHandler)
	serverAddr := ":8000"
	fmt.Printf("Starting server on %s...\n", serverAddr)
	if err := http.ListenAndServe(serverAddr, nil); err != nil {
		log.Fatalf("Server failed: %s", err)
	}
}