HMS-159 : Add support for webhook based authentication in slack

README.md

@@ -139,6 +139,7 @@ receivers:
   - name: "slack"
     slack:
       token: YOUR-API-TOKEN-HERE
+      endpoint: YOUR-WEBHOOK-ENDPOINT-HERE
       channel: "@{{ .InvolvedObject.Labels.owner }}"
       message: "{{ .Message }}"
       color: # optional
@@ -152,6 +153,8 @@ receivers:
 
 ```
 
+The bot `token` along with the `channel` field can be used for authentication. Alternatively, `endpoint` field can be used to define the webhook url for a given channel. In case both the fields `token` and `endpoint` are provided, the bot-token will be used for authentication.
+
 ### Kinesis
 
 Kinesis is an AWS service allows to collect high throughput messages and allow it to be used in stream processing.

pkg/sinks/slack.go

@@ -2,7 +2,6 @@ package sinks
 
 import (
 	"context"
-
 	"github.com/opsgenie/kubernetes-event-exporter/pkg/kube"
 	"github.com/rs/zerolog/log"
 	"github.com/slack-go/slack"
@@ -17,6 +16,7 @@ type SlackConfig struct {
 	Title      string            `yaml:"title"`
 	AuthorName string            `yaml:"author_name"`
 	Fields     map[string]string `yaml:"fields"`
+	Endpoint   string            `yaml:"endpoint"`
 }
 
 type SlackSink struct {
@@ -30,25 +30,15 @@ func NewSlackSink(cfg *SlackConfig) (Sink, error) {
 		client: slack.New(cfg.Token),
 	}, nil
 }
+func (s *SlackSink) GetAttachment(ev *kube.EnhancedEvent) (slack.Attachment, error) {
 
-func (s *SlackSink) Send(ctx context.Context, ev *kube.EnhancedEvent) error {
-	channel, err := GetString(ev, s.cfg.Channel)
-	if err != nil {
-		return err
-	}
-
-	message, err := GetString(ev, s.cfg.Message)
-	if err != nil {
-		return err
-	}
-
-	options := []slack.MsgOption{slack.MsgOptionText(message, true)}
+	slackAttachment := slack.Attachment{}
 	if s.cfg.Fields != nil {
 		fields := make([]slack.AttachmentField, 0)
 		for k, v := range s.cfg.Fields {
 			fieldText, err := GetString(ev, v)
 			if err != nil {
-				return err
+				return slackAttachment, err
 			}
 
 			fields = append(fields, slack.AttachmentField{
@@ -57,9 +47,6 @@ func (s *SlackSink) Send(ctx context.Context, ev *kube.EnhancedEvent) error {
 				Short: false,
 			})
 		}
-
-		// make slack attachment
-		slackAttachment := slack.Attachment{}
 		slackAttachment.Fields = fields
 		if s.cfg.AuthorName != "" {
 			slackAttachment.AuthorName = s.cfg.AuthorName
@@ -73,12 +60,46 @@ func (s *SlackSink) Send(ctx context.Context, ev *kube.EnhancedEvent) error {
 		if s.cfg.Footer != "" {
 			slackAttachment.Footer = s.cfg.Footer
 		}
+	}
+	return slackAttachment, nil
+}
 
-		options = append(options, slack.MsgOptionAttachments(slackAttachment))
+func (s *SlackSink) Send(ctx context.Context, ev *kube.EnhancedEvent) error {
+	message, err := GetString(ev, s.cfg.Message)
+	if err != nil {
+		return err
 	}
 
-	_ch, _ts, _text, err := s.client.SendMessageContext(ctx, channel, options...)
-	log.Debug().Str("ch", _ch).Str("ts", _ts).Str("text", _text).Err(err).Msg("Slack Response")
+	slackAttachments, err := s.GetAttachment(ev)
+	if err != nil {
+		return err
+	}
+	// use bot token
+	if s.cfg.Token != "" {
+		channel, err := GetString(ev, s.cfg.Channel)
+		if err != nil {
+			return err
+		}
+		options := []slack.MsgOption{slack.MsgOptionText(message, true)}
+		options = append(options, slack.MsgOptionAttachments(slackAttachments))
+		_ch, _ts, _text, err := s.client.SendMessageContext(ctx, channel, options...)
+		log.Debug().Str("ch", _ch).Str("ts", _ts).Str("text", _text).Err(err).Msg("Slack Response")
+		return err
+	} else {
+		// use webhook endpoint
+		endpoint, err := GetString(ev, s.cfg.Endpoint)
+		if err != nil {
+			return err
+		}
+		webhookMessage := slack.WebhookMessage{
+			Text:        message,
+			Attachments: []slack.Attachment{slackAttachments},
+		}
+		err = slack.PostWebhook(endpoint, &webhookMessage)
+		if err != nil {
+			return err
+		}
+	}
 	return err
 }