Add subscription to WebSub server

cmd/server/incoming.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"crypto/hmac"
+	"crypto/sha1"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// HubBackend handles information for the incoming handler
+type HubBackend interface {
+	CreateFeed(url string) int64
+	GetSecret(id int64) string
+}
+
+type incomingHandler struct {
+	Backend HubBackend
+}
+
+var (
+	urlRegex = regexp.MustCompile(`^/incoming/(\d+)$`)
+)
+
+func (h *incomingHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	defer r.Body.Close()
+	if r.Method == http.MethodGet {
+		values := r.URL.Query()
+
+		// check
+
+		verify := values.Get("hub.challenge")
+		fmt.Fprint(w, verify)
+
+		return
+	}
+
+	if r.Method != http.MethodPost {
+		http.Error(w, "Method not allowed", 405)
+		return
+	}
+
+	// find feed
+	matches := urlRegex.FindStringSubmatch(r.URL.Path)
+	feed, err := strconv.ParseInt(matches[1], 10, 64)
+	if err != nil {
+		fmt.Fprint(w, err)
+	}
+
+	// find secret
+	secret := h.Backend.GetSecret(feed)
+	if secret == "" {
+		http.Error(w, "Unknown", 400)
+		return
+	}
+
+	// match signature
+	sig := r.Header.Get("X-Hub-Signature")
+	parts := strings.Split(sig, "=")
+
+	if len(parts) != 2 {
+		http.Error(w, "Signature format", 400)
+		return
+	}
+
+	if sig != "sha1" {
+		http.Error(w, "Unknown signature format", 400)
+		return
+	}
+
+	feedContent, err := ioutil.ReadAll(r.Body)
+
+	// verification
+	mac := hmac.New(sha1.New, []byte(secret))
+	mac.Write(feedContent)
+	signature := mac.Sum(nil)
+
+	if fmt.Sprintf("%x", signature) != parts[1] {
+		http.Error(w, "Signature doesn't match", 400)
+		return
+	}
+
+	ct := r.Header.Get("Content-Type")
+	if strings.HasPrefix(ct, "application/rss+xml") {
+		// RSS parsing
+	} else if strings.HasPrefix(ct, "application/atom+xml") {
+		// Atom parsing
+	} else if strings.HasPrefix(ct, "text/html") {
+		// h-entry parsing
+	} else {
+		http.Error(w, "Unknown format of body", 400)
+		return
+	}
+}

cmd/server/main.go

@@ -22,7 +22,9 @@ import (
 	"flag"
 	"fmt"
 	"log"
+	"math/rand"
 	"net/http"
+	"net/url"
 	"os"
 	"regexp"
 	"strings"
@@ -45,8 +47,68 @@ func init() {
 }
 
 type microsubHandler struct {
-	Backend microsub.Microsub
-	Redis   redis.Conn
+	Backend            microsub.Microsub
+	HubIncomingBackend HubBackend
+	Redis              redis.Conn
+}
+
+type hubIncomingBackend struct {
+	conn redis.Conn
+}
+
+const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+
+func randStringBytes(n int) string {
+	b := make([]byte, n)
+	for i := range b {
+		b[i] = letterBytes[rand.Intn(len(letterBytes))]
+	}
+	return string(b)
+}
+
+func (h *hubIncomingBackend) GetSecret(id int64) string {
+	secret, err := redis.String(h.conn.Do("HGET", fmt.Sprintf("feed:%d", id), "secret"))
+	if err != nil {
+		return ""
+	}
+	return secret
+}
+
+var hubUrl = "https://hub.stuifzandapp.com/"
+
+func (h *hubIncomingBackend) CreateFeed(topic string) int64 {
+	id, err := redis.Int64(h.conn.Do("INCR", "feed:next_id"))
+	if err != nil {
+		log.Println(err)
+	}
+
+	h.conn.Do("HSET", fmt.Sprintf("feed:%d", id), "url", topic)
+	secret := randStringBytes(16)
+	h.conn.Do("HSET", fmt.Sprintf("feed:%d", id), "secret", secret)
+
+	hub, err := url.Parse(hubUrl)
+	q := hub.Query()
+	q.Add("hub.mode", "subscribe")
+	q.Add("hub.callback", fmt.Sprintf("https://microsub.stuifzandapp.com/incoming/%d", id))
+	q.Add("hub.topic", topic)
+	q.Add("hub.secret", secret)
+	hub.RawQuery = q.Encode()
+
+	req, err := http.NewRequest("GET", hub.String(), nil)
+	if err != nil {
+		log.Printf("new request: %s\n", err)
+		return -1
+	}
+
+	client := &http.Client{}
+
+	_, err = client.Do(req)
+	if err != nil {
+		log.Printf("subscription request: %s\n", err)
+		return -1
+	}
+
+	return id
 }
 
 func simplify(itemType string, item map[string][]interface{}) map[string]interface{} {
@@ -345,7 +407,7 @@ func (h *microsubHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		} else if action == "follow" {
 			uid := values.Get("channel")
 			url := values.Get("url")
-
+			h.HubIncomingBackend.CreateFeed(url)
 			feed := h.Backend.FollowURL(uid, url)
 			w.Header().Add("Content-Type", "application/json")
 			jw := json.NewEncoder(w)
@@ -432,6 +494,15 @@ func main() {
 		backend = loadMemoryBackend(conn)
 	}
 
-	http.Handle("/microsub", &microsubHandler{backend, nil})
+	hubBackend := hubIncomingBackend{conn}
+
+	http.Handle("/microsub", &microsubHandler{
+		Backend:            backend,
+		HubIncomingBackend: &hubBackend,
+		Redis:              nil,
+	})
+	http.Handle("/incoming/", &incomingHandler{
+		Backend: &hubBackend,
+	})
 	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%d", port), nil))
 }