slack-welcomer: add workflow-only moderation for #kubernetes-careers

slack-welcomer/handler.go

@@ -22,10 +22,21 @@ import (
 	"io/ioutil"
 	"log"
 	"net/http"
+	"time"
 
 	"sigs.k8s.io/slack-infra/slack"
 )
 
+const (
+	workflowNotice = `Hi there! Your message in <#%s> was removed because that channel only accepts posts submitted via the official workflow.
+
+To post a job listing or resume, please use the workflow shortcut (:zap:) in that channel.
+
+If you have questions, reach out in #slack-admins.`
+
+	maxRetries = 5
+)
+
 type handler struct {
 	client      *slack.Client
 	messagePath string
@@ -39,7 +50,6 @@ func logError(rw http.ResponseWriter, format string, args ...interface{}) {
 
 type handlerFunc func(body []byte) ([]byte, error)
 
-// ServeHTTP handles Slack webhook requests.
 func (h *handler) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
 	body, err := ioutil.ReadAll(r.Body)
 	if err != nil {
@@ -96,35 +106,169 @@ func (h *handler) handleURLVerification(body []byte) ([]byte, error) {
 }
 
 func (h *handler) handleEvent(body []byte) ([]byte, error) {
-	event := struct {
+	t := struct {
 		Event struct {
-			Type string     `json:"type"`
-			User slack.User `json:"user"`
+			Type string `json:"type"`
 		} `json:"event"`
 	}{}
-	if err := json.Unmarshal(body, &event); err != nil {
+	if err := json.Unmarshal(body, &t); err != nil {
 		return nil, fmt.Errorf("failed to parse JSON: %v", err)
 	}
 
-	// We should only be getting team_join events, but be sure to filter out anything else.
-	// We don't consider this an error, because Slack might get upset if we did.
-	if event.Event.Type != "team_join" {
-		return []byte{}, nil
+	switch t.Event.Type {
+	case "team_join":
+		event := struct {
+			Event struct {
+				User slack.User `json:"user"`
+			} `json:"event"`
+		}{}
+		if err := json.Unmarshal(body, &event); err != nil {
+			return nil, fmt.Errorf("failed to parse JSON: %v", err)
+		}
+		if err := h.sendWelcome(event.Event.User.ID); err != nil {
+			return nil, fmt.Errorf("failed to send welcome: %v", err)
+		}
+	case "message":
+		event := struct {
+			Event struct {
+				SubType  string `json:"subtype"`
+				User     string `json:"user"`
+				Channel  string `json:"channel"`
+				Ts       string `json:"ts"`
+				ThreadTS string `json:"thread_ts"`
+				BotID    string `json:"bot_id"`
+			} `json:"event"`
+		}{}
+		if err := json.Unmarshal(body, &event); err != nil {
+			return nil, fmt.Errorf("failed to parse JSON: %v", err)
+		}
+		if event.Event.BotID != "" || event.Event.SubType == "bot_message" {
+			return []byte{}, nil
+		}
+		if event.Event.ThreadTS != "" && event.Event.ThreadTS != event.Event.Ts {
+			return []byte{}, nil
+		}
+		if h.isGuardedChannel(event.Event.Channel) && event.Event.User != "" {
+			if err := h.enforceWorkflowOnly(event.Event.Channel, event.Event.User, event.Event.Ts); err != nil {
+				return nil, fmt.Errorf("failed to enforce channel rules: %v", err)
+			}
+		}
 	}
 
-	if err := h.sendWelcome(event.Event.User.ID); err != nil {
-		return nil, fmt.Errorf("failed to send welcome: %v", err)
-	}
 	return []byte{}, nil
 }
 
+func (h *handler) isGuardedChannel(channel string) bool {
+	for _, c := range h.client.Config.GuardedChannels {
+		if c == channel {
+			return true
+		}
+	}
+	return false
+}
+
+func (h *handler) getUserInfo(id string) (slack.User, error) {
+	user := struct {
+		User slack.User `json:"user"`
+	}{}
+	if err := h.client.CallOldMethod("users.info", map[string]string{"user": id}, &user); err != nil {
+		return slack.User{}, fmt.Errorf("failed get user: %v", err)
+	}
+	return user.User, nil
+}
+
+func (h *handler) userIsAdmin(id string) (bool, error) {
+	user, err := h.getUserInfo(id)
+	if err != nil {
+		log.Printf("Failed to look up admin status: %v\n", err)
+		return false, err
+	}
+	return user.IsAdmin || user.IsOwner || user.IsPrimaryOwner, nil
+}
+
+func (h *handler) enforceWorkflowOnly(channel, userID, ts string) error {
+	admin, err := h.userIsAdmin(userID)
+	if err != nil {
+		log.Printf("Could not verify admin status for user %s, allowing post: %v\n", userID, err)
+		return nil
+	}
+	if admin {
+		return nil
+	}
+
+	log.Printf("Removing direct post from user %s in channel %s\n", userID, channel)
+
+	adminClient := slack.New(slack.Config{
+		AccessToken:   h.client.Config.AdminToken,
+		SigningSecret: h.client.Config.SigningSecret,
+	})
+
+	req := map[string]interface{}{
+		"channel": channel,
+		"ts":      ts,
+		"as_user": true,
+	}
+	for i := 0; i < maxRetries; i++ {
+		err := adminClient.CallMethod("chat.delete", req, nil)
+		if err == nil {
+			break
+		}
+		switch e := err.(type) {
+		case slack.ErrRateLimit:
+			if i == maxRetries-1 {
+				return fmt.Errorf("rate limit exceeded after %d retries: %v", maxRetries, err)
+			}
+			log.Printf("Slack is rate limiting us, trying again in %s...\n", e.Wait)
+			time.Sleep(e.Wait)
+		case slack.ErrSlack:
+			if e.Type == "message_not_found" {
+				log.Printf("Message to delete not found, probably already deleted.\n")
+				return nil
+			}
+			return err
+		default:
+			return err
+		}
+	}
+
+	if err := h.notifyUser(userID, channel); err != nil {
+		log.Printf("Deleted message but failed to DM user %s: %v\n", userID, err)
+	}
+	return nil
+}
+
+func (h *handler) notifyUser(userID, channelID string) error {
+	response := struct {
+		Channel struct {
+			ID string `json:"id"`
+		} `json:"channel"`
+	}{}
+	if err := h.client.CallMethod("conversations.open", map[string]string{"users": userID}, &response); err != nil {
+		return fmt.Errorf("couldn't open a conversation channel: %v", err)
+	}
+	message := struct {
+		Channel   string `json:"channel"`
+		Text      string `json:"text"`
+		AsUser    bool   `json:"as_user"`
+		LinkNames bool   `json:"link_names"`
+	}{
+		Channel:   response.Channel.ID,
+		Text:      fmt.Sprintf(workflowNotice, channelID),
+		AsUser:    true,
+		LinkNames: true,
+	}
+	if err := h.client.CallMethod("chat.postMessage", message, nil); err != nil {
+		return fmt.Errorf("failed to send message: %v", err)
+	}
+	return nil
+}
+
 func (h *handler) sendWelcome(uid string) error {
 	welcome, err := h.getWelcome()
 	if err != nil {
 		return fmt.Errorf("couldn't get welcome: %v", err)
 	}
 
-	// Slack requires that we first open a "conversation channel" that we can then use to actually send messages.
 	response := struct {
 		Channel struct {
 			ID string `json:"id"`

slack-welcomer/main.go

@@ -43,9 +43,7 @@ func handleHealthz(w http.ResponseWriter, r *http.Request) {
 	_, _ = w.Write([]byte("ok"))
 }
 
-func runServer(sl *slack.Client, o options) {
-	h := &handler{client: sl, messagePath: o.messagePath}
-
+func runServer(h *handler) error {
 	http.HandleFunc("/healthz", handleHealthz)
 	http.Handle(os.Getenv("PATH_PREFIX")+"/webhook", h)
 
@@ -56,7 +54,7 @@ func runServer(sl *slack.Client, o options) {
 	}
 
 	log.Printf("Listening on port %s", port)
-	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", port), nil))
+	return http.ListenAndServe(fmt.Sprintf(":%s", port), nil)
 }
 
 func main() {
@@ -65,6 +63,14 @@ func main() {
 	if err != nil {
 		log.Fatalf("Failed to load config from %s: %v", o.configPath, err)
 	}
+	if c.AdminToken == "" {
+		log.Fatalf("adminToken is required but was not found in %s", o.configPath)
+	}
+	if len(c.GuardedChannels) == 0 {
+		log.Fatalf("guardedChannels is required but was not found in %s", o.configPath)
+	}
 	s := slack.New(c)
-	runServer(s, o)
+
+	h := &handler{client: s, messagePath: o.messagePath}
+	log.Fatal(runServer(h))
 }

slack/config.go

@@ -24,9 +24,11 @@ import (
 
 // Config is the information needed to communicate with Slack.
 type Config struct {
-	SigningSecret string `json:"signingSecret"`
-	WebhookURL    string `json:"webhook"`
-	AccessToken   string `json:"accessToken"`
+	SigningSecret   string   `json:"signingSecret"`
+	WebhookURL      string   `json:"webhook"`
+	AccessToken     string   `json:"accessToken"`
+	AdminToken      string   `json:"adminToken"`
+	GuardedChannels []string `json:"guardedChannels"`
 }
 
 // LoadConfig loads a Config from a JSON file.