howsmyssl is the web app behind https://howsmyssl.com.

This is a Go project.

The HTML code goes in templates/. Templates are generated with Go's html/template package. Determining the client's security is done in client_info.go.

This project requires Go 1.10 (or newer). go build will generate a static binary called howsmyssl. This repo is go get'able, of course.

It has a fork of the Go crypto/tls library at ./tls/ in order to add a ServerHandshake and expose the ClientHello struct.

It's been useful to me to use justrun to recompile the project while modifying the template. Typical use is simply:

justrun -c "go build && ./howsmyssl" -i howsmyssl . templates/

(Justrun has the benefit of controlling the lifecycle of a process, unlike most other file watch utilities.)