caddy-ja4h

Caddy v2 module to calculate the JA4H fingerprinter for each request and add it to the headers.

Installation

You can build Caddy by yourself by installing xcaddy and running:

xcaddy build --with github.com/lum8rjack/caddy-ja4h

If you want to clone and make any changes, you can test locally with the following command:

# Specify the location of the local build
 xcaddy build --with github.com/lum8rjack/caddy-ja4h=./caddy-ja4h

Caddyfile

Below is an example Caddyfile that will calculate the JA4H fingerprint for each request and add it as a new header before forwarding the request on.

{
  admin off
  order ja4h_header first
}

https://test.example.com {
  ja4h_header

  handle /* {
    reverse_proxy https://localhost:8080 {
      header_up Host {http.request.host}
      transport http {
        tls
        tls_insecure_skip_verify
      }
    }
  }
}

The request received on the backen will look similar to below with the newly added JA4H header.

GET / HTTP/1.1
Host: 127.0.0.1:9000
User-Agent: curl/7.81.0
Accept: */*
Ja4h: ge11nn020000_a00508f53a24_000000000000_000000000000
X-Forwarded-For: 127.0.0.1
X-Forwarded-Host: 127.0.0.1:9000
X-Forwarded-Proto: http
Accept-Encoding: gzip

References

• JA4+ Network Fingerprinting
• ja4 GitHub
• go-ja4h