cool-dns/internal/lego.go

package cooldns

import (
	"encoding/json"
	"log"
	"net/http"

	"github.com/miekg/dns"
)

// See https://go-acme.github.io/lego/dns/httpreq/

type configLego struct {
	Enable   bool   `yaml:"enable"`
	Address  string `yaml:"address"`
	Username string `yaml:"username"`
	Secret   string `yaml:"secret"`
}

type legoPresent struct {
	Fqdn  string `json:"fqdn"`
	Value string `json:"value"`
}

type legoMap map[string]string

func startLEGOWebSever(config configLego) *legoMap {
	mux := http.NewServeMux()

	acmeMap := make(legoMap)

	mux.HandleFunc("/present", func(rw http.ResponseWriter, r *http.Request) {

		if !checkBasicAuth(r, config) {
			rw.WriteHeader(http.StatusUnauthorized)
			return
		}

		var presentData legoPresent
		err := json.NewDecoder(r.Body).Decode(&presentData)
		defer r.Body.Close()

		if err != nil {
			log.Printf("Failed to parse request for ACME: %s", err.Error())
		}

		acmeMap[presentData.Fqdn] = presentData.Value

		rw.WriteHeader(http.StatusOK)
	})

	mux.HandleFunc("/cleanup", func(rw http.ResponseWriter, r *http.Request) {
		if !checkBasicAuth(r, config) {
			rw.WriteHeader(http.StatusUnauthorized)
			return
		}

		for k := range acmeMap {
			delete(acmeMap, k)
		}

		rw.WriteHeader(http.StatusOK)
	})

	go func() {
		if err := http.ListenAndServe(config.Address, mux); err != nil {
			log.Fatalf("Failed to start Webserver for LEGO: %s\n", err.Error())
		}
	}()

	log.Printf("Startet webserver on %s", config.Address)

	return &acmeMap
}

func checkBasicAuth(r *http.Request, config configLego) bool {
	if config.Username != "" && config.Secret != "" {
		u, p, ok := r.BasicAuth()
		if !ok {
			return false
		}

		if u == config.Username && p == config.Secret {
			return true
		}

		log.Printf("Failed lego authentication")

		return false
	}
	return true
}

func handleACMERequest(w dns.ResponseWriter, r *dns.Msg, acmeMap *legoMap) bool {
	if len(r.Question) == 1 {
		if r.Question[0].Qtype == dns.TypeTXT && r.Question[0].Qclass == dns.ClassINET {
			if value, ok := (*acmeMap)[r.Question[0].Name]; ok {
				m := new(dns.Msg)
				m.SetReply(r)

				m.Answer = append(m.Answer, &dns.TXT{
					Hdr: dns.RR_Header{
						Name:   r.Question[0].Name,
						Rrtype: dns.TypeTXT,
						Class:  dns.ClassINET,
						Ttl:    0,
					},
					Txt: []string{value},
				})

				w.WriteMsg(m)
				return true
			}
		}
	}

	return false
}